Quercetin/curcumin suppresses pancreatic tumor growth and enhances chemosensitivity in a Capan-1 xenograft model

Abstract

Background

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest malignancies, with a five-year survival rate of only 6%. Its aggressive biology, early metastasis, and remarkable resistance to chemotherapy and radiation contribute to poor outcomes. Novel treatment strategies are urgently needed. Quercetin(Q) and curcumin(C) are plant-derived polyphenols known for anti-cancer properties, low toxicity, and potential to overcome drug resistance. This study evaluates the therapeutic efficacy of quercetin/curcumin (Q/C) in an in vivo PDAC model using Capan-1 (a chemoresistant human PDAC cell line) xenografts in nude mice, alone and in combination with cisplatin.

Methods

Thirty-four nude mice with established subcutaneous Capan-1 tumors were randomized into six groups (n = 7 each): Control, cisplatin only, Q/C (oral), Q/C (intraperitoneal, IP), cisplatin + Q/C(in drinking water), and a prophylactic Q/C group (Q/C given 5 days prior to tumor inoculation). Q/C (quercetin–curcumin solution) was administered daily by oral gavage, IP injection, or ad libitum in water for 28 days. Cisplatin (20 mg/kg IP) was given for 5 consecutive days at the start of treatment and repeated 3 weeks later. Tumor size was measured periodically, and at the endpoint, the excised tumors were weighed and processed for histopathological examination (H&E staining). Tumor dimensions and volumes were recorded, and the fraction of necrotic tumor area was quantified by microscopic image analysis.

Results

Q/C treatment is described with a mean difference and 95% CI (no p-value), inhibiting tumor growth in vivo. At matched time points, mice receiving Q/C monotherapy (oral or i.p.) exhibited ~ 40% lower in-life tumor volumes than untreated controls, with an effect similar in magnitude to cisplatin monotherapy (~ 40% mean reduction; longitudinal descriptive analysis with 95% CIs; final tumor-weight differences evaluated separately by one-way ANOVA with Tukey HSD). The combination of cisplatin + Q/C produced the greatest suppression of tumor growth, with final tumor weight (3.16 g) reduced by 72% relative to control (11.3 g) and described with a mean difference and 95% CI (no p-value), smaller tumor dimensions (approx. 2.3 × 1.9 × 1.2 cm vs. 3.9 × 2.5 × 2.2 cm in control). Tumor growth curves showed a substantially slower increase in volume with Q/C, especially when combined with cisplatin, compared to the rapid growth observed in the control and cisplatin-only groups. Prophylactic quality control (Q/C) administered prior to tumor implantation was not associated with a measurable delay in tumor development; time-to-onset estimates closely overlapped those of the controls, and point estimates with 95% confidence intervals were compatible with no material effect. Histopathological analysis revealed increased tumor necrosis in all treated groups. The mean necrotic area in tumors was 57–67% in the oral and IP Q/C groups and 47.5% in the combination group, compared to only 32.5% in controls. Treated tumors exhibited extensive necrotic regions (pink, ghost-cell areas on H&E) and a reduction in viable tumor cells. No treatment-related mortalities occurred. Combination therapy was associated with a modest reduction in animal body weight (possibly reflecting added toxicity), whereas Q/C alone was well tolerated.

Conclusion

In the PDAC xenograft model, Q/C (quercetin/curcumin) demonstrated antitumor activity, slowing tumor progression and increasing intratumoral necrotic areas compared to the control group; quantitative results are presented as mean differences with 95% confidence intervals (one-way ANOVA with Tukey post-hoc). Specifically, Q/C plus cisplatin showed the smallest tumors and the greatest regression compared to each of the monotherapies. These findings suggest that combining quercetin and curcumin may help counter tumor resistance and enhance healing. Q/C, a novel polyphenol formulation, appears promising as an adjunctive (and potentially alternative) therapy in pancreatic cancer. Further studies are required to elucidate its range of effects, broaden its interactions with standard therapies (yielding effects greater than those of either agent alone), and enhance its clinical applicability in overcoming the resistance to invasiveness of pancreatic cancer.

Introduction

Pancreatic cancer is a highly lethal disease with a rising global impact. It is currently the fourth leading cause of cancer-related deaths and is projected to become the second leading cause by 2030 [1]. Most patients present with advanced, unresectable disease, and even with treatment, the prognosis remains dismal – overall five-year survival is around 7% [2]. This poor outcome is attributed to the aggressive biology of pancreatic ductal adenocarcinoma (PDAC), which is characterized by early local invasion and metastasis, a dense desmoplastic stroma, and remarkable resistance to conventional chemotherapies and radiotherapy. Standard treatment for advanced yields low response rates, and tumors often rapidly develop chemoresistance. Therefore, there is intense interest in new therapeutic approaches that can improve treatment response or overcome resistance in pancreatic cancer [3].

Natural polyphenolic compounds have emerged as potential anti-cancer agents due to their multi-targeted mechanisms and low toxicity. Quercetin and curcumin are two such compounds that have shown promise in preclinical cancer models. Quercetin (3,3′,4′,5,7-pentahydroxyflavone) is a flavonoid abundant in many fruits and vegetables. It has potent antioxidant and anti-inflammatory properties and has demonstrated anti-cancer effects in multiple tumor types. Quercetin can inhibit cancer cell proliferation and induce apoptosis through various mechanisms, including modulation of cell signaling pathways and interference with enzymes involved in carcinogen activation. Notably, quercetin has been reported to synergize with standard chemotherapeutic drugs. For example, combining quercetin with cisplatin or doxorubicin can enhance the chemosensitivity of cancer cells by inhibiting proliferation, invasion, and promoting apoptosis [4]. In breast cancer cells, quercetin increased sensitivity to doxorubicin by modulating the PTEN/Akt pathway and increasing apoptosis [5, 6]. Quercetin appears particularly relevant in pancreatic cancer because it can target pathways linked to drug resistance. Quercetin has been shown to induce apoptosis even in resistant pancreatic cancer cells by activating c-Jun N-terminal kinase (JNK) and promoting the degradation of anti-apoptotic proteins, such as c-FLIP, thereby sensitizing cells to death ligands [7]. Furthermore, quercetin can inhibit tumor cell migration and the properties of cancer stem cells. Cao et al. (2015) demonstrated that quercetin suppressed the proliferation and self-renewal of pancreatic cancer stem-like cells and downregulated their stem cell markers. Notably, quercetin, when combined with gemcitabine, reduced tumor growth and decreased drug resistance in a pancreatic cancer model [8].

Curcumin (diferuloylmethane) is the active polyphenol in turmeric (Curcuma longa) and has also been extensively studied for its anti-cancer properties. It can interfere with multiple molecular targets involved in cancer progression, including transcription factors, inflammatory mediators (such as COX-2 and TNF-α), growth factor receptors, and apoptotic regulators [9]. Recent in vivo data indicate that phytochemicals can attenuate inflammation by engaging the PPAR-Γ/arachidonic Acid (AA) axis. Recent in vivo data indicate that phytochemicals can attenuate inflammation by engaging the PPAR-Γ/arachidonic Acid (AA) axis. In particular, Wu et al. (2025) demonstrated PPAR-γ–mediated control of AA metabolism, providing up-to-date support for plant-derived modulators of this pathway. In line with prior reports on curcumin and quercetin, these findings support our working hypothesis that Q/C may contribute to anti-inflammatory and chemosensitizing effects in PDAC. These findings support the idea that quercetin may overcome chemoresistance by targeting the subpopulations of cells and signaling pathways that drive tumor recurrence [10]. Curcumin induces cancer cell death through intrinsic (mitochondrial) and extrinsic apoptotic pathways. For instance, curcumin perturbs the mitochondrial membrane potential, downregulates the anti-apoptotic Bcl-xL, and upregulates the death receptors DR4 and DR5 to trigger extrinsic apoptosis signaling. In various malignancies, curcumin has shown the ability to inhibit tumor growth, angiogenesis, invasion, and metastasis. Like quercetin, curcumin may enhance the activity of chemotherapeutic agents through its chemosensitizing effects. It has been reported to enhance the efficacy of cisplatin, doxorubicin, and paclitaxel by reducing drug resistance and improving tumor cell response. For example, curcumin increased the sensitivity of cisplatin-resistant non-small cell lung carcinoma cells to cisplatin and enhanced cisplatin response in ovarian cancer cells when used in combination with resveratrol, a pattern consistent with additive or greater effects than monotherapy. These enhanced effects are generally attributed to curcumin’s regulation of survival pathways and its promotion of apoptotic and anti-proliferative signaling in tumor cells [11, 12].

Despite its potent antitumor activity in vitro, the clinical translation of curcumin has been challenging due to pharmacokinetic limitations. Orally administered curcumin exhibits poor water solubility and undergoes rapid metabolism, resulting in low systemic bioavailability [13–15]. In a phase II trial in advanced pancreatic cancer, patients received 8 g/day of oral curcumin; no dose-limiting toxicities were observed, but plasma levels of free curcumin were extremely low, and only modest biological effects were noted. Only 2 of 21 evaluable patients showed clinical tumor activity [16]. In a subsequent study combining curcumin with gemcitabine chemotherapy, curcumin, administered at 8 g/day, proved difficult for patients to tolerate alongside chemotherapy – nearly half the patients could not maintain the 8 g dose due to abdominal discomfort, and the curcumin dose had to be reduced to 4 g/day in others. While the combination was deemed feasible and safe, the overall response rate was low, and the median time to progression was only 2–3 months. The low compliance and limited efficacy in these trials underscore the need for improved formulations or delivery methods to harness curcumin’s benefits in vivo. Strategies such as structural analogs, nano-formulations, or combining curcumin with bio-enhancers have been explored to overcome these issues [17]. One promising approach is to pair curcumin with other natural compounds that might boost its absorption or activity.

Combining quercetin and curcumin is a rational strategy, as these agents may have complementary and synergistic anti-cancer effects. Quercetin has some bioavailability issues; importantly, it can act as a bioenhancer. Evidence suggests that quercetin can improve the intestinal absorption of curcumin. In an in vitro Caco-2 cell model, the permeability of curcumin increased by 1.5 fold when curcumin was co-administered with quercetin. Thus, quercetin might slow curcumin’s metabolic degradation and increase its bioactivity. Furthermore, both compounds target overlapping pathways as well as unique ones; therefore, their combination could yield additive or synergistic antitumor effects. This concept is supported by preclinical studies, where multi-polyphenol combinations have shown enhanced efficacy. For instance, combining curcumin, quercetin, and resveratrol enhanced the cellular uptake and anti-proliferative activity of each compound without adverse interactions [18].

Q/C is a novel formulation that contains both quercetin and curcumin in solution form. It was developed to exploit the synergistic anti-cancer potential of these compounds. This study examined the therapeutic effect of Q/C in a mouse xenograft model of pancreatic cancer. In this study, the Capan-1 human pancreatic cancer cell line was used, which is known to be relatively chemoresistant. Tumor-bearing mice were treated with Q/C via different routes to evaluate its efficacy alone. One group combined quality control (Q/C) with the cytotoxic drug cisplatin to assess potential additive benefits. Although cisplatin is not a first-line standard for pancreatic cancer, it was selected as a model cytotoxic backbone to evaluate combination effects and chemosensitization, given prior evidence that quercetin and curcumin can augment platinum-based activity [11]. Beyond inflammatory/redox modulation, emerging medicinal-chemistry studies show that small molecules can stabilize oncogenic G-quadruplexes and thereby remodel transcriptional programs and drug response. Recent work reviews c-MYC G4 targeting and its potential to suppress MYC-driven signaling (Thumpati 2025); demonstrates G4-guided strategies impacting resistance pathways, including efflux (Chaudhuri 2024); and defines selectivity principles for c-KIT G4 recognition (Fatma 2024). These complementary mechanisms provide a multi-target rationale for Q/C ± platinum in PDAC, alongside our primary biological hypothesis [19–21].

Because diabetes is prevalent in PDAC, concomitant antidiabetic therapy can confound pancreatic symptoms and enzymes. Li et al. (2024) described SGLT2 inhibitor–associated acute pancreatitis, underscoring the need to consider medication effects in translational interpretation [22].

This study also included a prophylactic treatment group to explore whether pre-treating mice with Q/C before tumor implantation could impede tumor establishment. Endpoints measured included tumor growth (size/volume), final tumor weight, and histological tumor necrosis. The present study hypothesized that Q/C would inhibit tumor growth and increase tumor cell death and that combining Q/C with cisplatin would result in greater tumor regression than either therapy alone. The results of this study provide insight into the in vivo antitumor efficacy of the quercetin–curcumin combination and its potential role in overcoming pancreatic cancer resistance mechanisms.

Materials and methods

The Pancreatic cancer (Capan-1) cell line was used. The cell was obtained from the cell stocks within the Kırıkkale University Scientific and Technological Research Application and Research Center. For cell cultivation, Dulbecco’s Modified Eagle’s Medium (DMEM, Sigma-Aldrich, USA) containing 10% fetal bovine serum (FBS) (Biowest, USA) and 1% Penicillin-Streptomycin (Pen-Strep, Pan Biotech, Germany) was prepared. Trypsin/EDTA and MTT solution (Pan Biotech, Germany) were used to separate cells from the bottom of the flask during cell passaging and to count nude mice obtained from the NESA lab.(Ankara, Turkiye).

MTT cytotoxicity test

The cytotoxicity test was performed according to ISO-10993-5 using the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] method. In this method, the change in enzymatic activity due to the decrease in formazan dyes or MTT is measured colorimetrically. The intensity of the resulting color is directly proportional to the number of viable cells. This method allows the determination of the cytotoxic effects of substances applied to the cells. In this study, passaged Capan-1 cells were first seeded in 100 µL of culture medium per well of a 96-well plate. The plate was then incubated for 24 h in an incubator set at 37 °C and 5% CO₂. At the end of the 24-hour incubation, using sterile automatic pipettes, 50 ppm quercetin/28 ppm curcumin was applied to the medium in the wells at three different concentrations. Medium alone was used as the negative control, and 50, 25, and 12.5 µM cisplatin were used as the positive control. Each sample was run in triplicate. After the applications, the cells were left for 48 h in an incubator set at 5% CO₂ and 37 °C. At the end of the incubation periods, 100 µL of the medium in the wells was removed. 10 µL of MTT solution was pipetted into the remaining 100 µL of medium-cell content and left for a 4-hour incubation. Then, 100 µL of DMSO was added, and the mixture was incubated for 20 min. At the end of this period, absorbance values were read at 570 nm using an ELISA device. To calculate percent cell viability, the absorbance values obtained from the MTT analysis of the melatonin, cisplatin, cetuximab, and combined groups were divided by the absorbance value of the control group and multiplied by 100.

% Cell viability = Drugs applied groups absorbance value/Control groups absorbance value ×100.

Xenograft model and treatment groups

All animal procedures were approved by the Kırıkkale University Animal Experiments Ethics Committee (Decision Date: March 26, 2024; No: 2024/3–16) and were conducted in accordance with institutional animal care guidelines. A human pancreatic cancer xenograft model was established using Capan-1 cells (ATCC HTB-79), a human PDAC cell line. Capan-1 cells were cultured in vitro and suspended in Matrigel for injection. Thirty-four six-week-old BALB/c nude mice (both sexes) were used. Each mouse was injected subcutaneously in the flank with 1 × 10⁶ Capan-1 cells in 0.1 mL of Matrigel. Cisplatin was administered at 4 mg/kg/day i.p. on Days 1–5 (20 mg/kg total per cycle), and the same 5-day course was repeated after a 3-week interval (Days 22–26), for a cumulative dose of 40 mg/kg across two cycles. To document tolerability, body weight was recorded on each dosing day and three times per week thereafter. Animals were clinically monitored for distress, dehydration, and other prespecified humane-endpoint criteria. Mice meeting these endpoints were ethically removed and censored in longitudinal analyses. Nude mice with developed tumors were randomly divided into six experimental groups. All caliper measurements were performed by blinded assessors, with monitoring three times per week. These groups are presented in Table 1.

Table 1.

Experimental groups and treatment combinations

Group	Treatment Components	Route / Dose	Schedule & Timing	Purpose / Notes
1 – Control	—	—	No antitumor treatment; tumor progression observed only	Negative control
2 – Cisplatin	Cisplatin 20 mg kg⁻¹	4 mg/kg/day i.p. (Days 1–5 and 22–26)	5-day course, repeated after 3 weeks; cumulative 40 mg/kg	Standard platinum-chemotherapy arm
3 – Q/C (Oral)	Q/C solution (quercetin + curcumin)	Daily oral gavage (0.2 mL mouse⁻¹)	Once daily for 28 days	Monotherapy — exploits oral bioavailability
4 – Q/C (i.p.)	Q/C solution	i.p. injection ( 0.2 mL mouse⁻¹)	Once daily for 28 days	Monotherapy — parenteral delivery
5 – Cisplatin + Q/C	Cisplatin 20 mg kg⁻¹ + Q/C	4 mg/kg/day i.p. (Days 1–5 and 22–26)	5-day course, repeated after 3 weeks; cumulative 40 mg/kg	Combination arm (Q/C + cisplatin)
6 – Prophylactic Q/C	Q/C	Drinking water (ad libitum)	It began 5 days before tumor inoculation and continued throughout the 28-day study.	Chemoprevention / early-exposure arm

All groups were observed for 28 days from the start of treatment (for Groups 1–5, Day 0 was the first day of cisplatin/ Q/C dosing; for Group 6, Day 0 was defined as the day of tumor inoculation). Quercetin (Q) and curcumin (C) target exposures were administered at 0.50 mg/kg/day (Q) and 0.28 mg/kg/day (C), respectively. For oral or i.p. bolus dosing, both agents were co-formulated in a single 0.2 mL dose and weight-normalized per mouse using C_working (mg/mL) = [target dose (mg/kg/day) × body weight (kg)] / 0.2 mL; for a 22 g mouse, this gives ~ 0.055 mg/mL Q and 0.031 mg/mL C when prepared fresh on dosing days. Target exposure for the drinking water level matched the bolus dosage, and the required water concentration was calculated from measured intake and mean body weight per cage per day using C_working (mg/mL) = [target dose (mg/kg/day) × mean BW (kg)] / mean water intake (mL/mouse/day).

Euthanasia and tissue collection

At the scheduled Day-28 study endpoint (or earlier if predefined humane endpoints were met), mice were deeply anaesthetised with an intraperitoneal injection of ketamine and xylazine. Ketamine was administered at a dose of 100 mg/kg and xylazine at 10 mg/kg, prepared from standard stock solutions (e.g. 100 mg/mL ketamine and 20 mg/mL xylazine) and diluted in sterile saline to a final injection volume of approximately 10 mL/kg body weight. Depth of anaesthesia was confirmed by loss of the righting reflex and absence of pedal-withdrawal responses. While under deep anaesthesia, animals were humanely euthanised by cervical dislocation performed exclusively by trained and certified personnel, in accordance with the IACUC-approved protocol and international guidelines for rodent euthanasia. Death was verified by the absence of respiratory movements, cardiac activity and corneal reflex before necropsy. Immediately thereafter, terminal body weights were recorded, and subcutaneous tumors and relevant organs were excised, weighed, measured (L×W×T) and processed for histopathology or storage as described in the subsequent sections. At the scheduled study endpoint (Day 28), or earlier if predefined humane endpoints were reached, mice were rendered deeply anesthetized by intraperitoneal administration of ketamine (100 mg/kg) and xylazine (10 mg/kg). Anesthetic solutions were prepared from standard stock concentrations (ketamine 100 mg/mL and xylazine 20 mg/mL) and diluted in sterile saline to achieve a final injection volume of approximately 10 mL/kg body weight. Adequate depth of anesthesia was confirmed by loss of the righting reflex and absence of pedal-withdrawal responses.

While under deep anesthesia, animals were humanely euthanized by cervical dislocation, performed exclusively by trained and certified personnel, in accordance with the IACUC-approved protocol, ARRIVE guidelines, and AVMA recommendations for euthanasia of laboratory rodents. Cervical dislocation was selected as a rapid and residue-free physical method, suitable for preserving tissue integrity for downstream biochemical and histopathological analyses.

Death was verified by the absence of respiratory movements, cardiac activity, and corneal reflex prior to necropsy. Immediately thereafter, terminal body weight was recorded for each animal. Tumor dimensions were measured three times per week with calibrated calipers. For consistency across the study, tumor volume was defined as V = (π/6)·L·W·T (L: length, W: width, T: thickness), and primary volumetric analyses were based on in-life measurements. Each tumor was bisected: one half fixed in 10% neutral buffered formalin for histopathology, and the other snap-frozen and stored at − 80 °C for downstream analyses.

Histopathology and necrosis assessment

Formalin-fixed tumor tissues were processed by routine paraffin embedding. Tissue sections of 5 μm thickness were cut from each paraffin block and mounted on slides. Sections were stained with hematoxylin and eosin (H&E) following standard protocols to evaluate histopathological features. An experienced veterinary pathologist, blinded to the group assignments, examined the H&E-stained sections under a light microscope. Key histologic features noted included tumor cellularity and pleomorphism, evidence of invasive growth (if any), and the extent of necrosis within the tumor. Tumor necrosis was identified on H&E as regions of eosinophilic, structureless cell debris, often lacking viable nuclei (“ghost cells”), and sometimes accompanied by inflammatory cell infiltrates.

An image analysis approach was used to quantify the degree of tumor necrosis. For each tumor, an entire cross-sectional slide was scanned at low magnification. The total cross-sectional area of the tumor and the area of necrotic regions were measured using ImageJ software (NIH) by thresholding and manual delineation. The percentage of necrotic area was calculated as follows: (necrotic area / total tumor area) × 100%. An average necrosis percentage per group was then determined by averaging the values from all tumors in that treatment group. Additionally, the pathologist qualitatively graded necrosis as mild, moderate, or extensive to corroborate the image analysis results. Features of viable tumor regions were also documented. Any distinctive histological findings were recorded, such as tumor giant cells, stromal response, or treatment-induced alterations, including fibrosis or pigment deposition.

Data analysis

Tumor volume measurements over time were plotted to compare growth kinetics between groups. Final tumor weights, volumes, and necrosis percentages were summarized as mean ± standard deviation for each group. Given the group size (n = 7) and the exploratory nature of this study, formal statistical hypothesis testing was limited. Where appropriate, one-way ANOVA with post-hoc comparisons was considered to assess differences among groups (with p < 0.05 as the significance threshold). However, primary emphasis was placed on descriptive comparisons and the magnitude of effects. State that one-way ANOVA + Tukey HSD was conducted for final tumor weight; report effect sizes and 95% CIs in text/tables. For endpoints without tests, specify that results are descriptive with 95% CIs (no p-values).

The efficacy of treatments was assessed by comparing the treated groups to the control group for tumor size/weight reduction, and by comparing combination therapy to single-agent therapies for evidence of additive or synergistic effects. Any observed toxicities were noted by comparing the body weight changes in each group and observing any associated clinical signs. Results are presented in tables and figures, including tumor growth curves, mean tumor sizes/weights, and representative histological images.

Results

Flavonoids are hydrophobic compounds with very low water solubility. Therefore, in this study, they were dissolved by ionization. Quercetin and curcumin were best dissolved in the tests at concentrations of 50 ppm and 28 ppm, respectively. Precipitation occurs at higher concentrations. Following ionization, the ionized flavonoid complex was applied to Capan-1 cells, and its passage through the cell membrane is shown under an inverted fluorescence microscope in Fig. 1. The flavonoids have a ring-shaped structure and appear green under a fluorescence microscope. As seen in Fig. 1A-B, when dissolved in water, they remain outside the cell but enter it in their ionized form.

Fig. 1.

A Q/C dissolved in water(arrows to show undissolved Q/C), (B) Q/C dissolved in ionized water (arrows to show dissolved and taken up by the cell Q/C). Photo taken by Leica DMI600 inverted fluorescent microscope

Toxicology studies demonstrate that flavonoids, at the doses used, achieve over 70% viability against normal fibroblast cells, consistent with the existing literature. However, the results obtained when applied to Capan-1 cancer cells are presented in Table 2. According to the table, while a toxic effect was observed at a concentration of 50 µM in the control group, the toxicity decreased as the dose decreased. The ionized quercetin/curcumin complex was found to have a 76% toxic effect against Capan-1 cancer cells at 50 ppm/28 ppm, a 62% effect at 25 ppm/14 ppm, and a 32% effect at 12.5 ppm/7 ppm. A literature review of cisplatin, used as a positive control, indicates that it exhibits a toxic effect at a concentration of 50 ppm in Capan-1 cell lines, while its toxicity decreases at lower concentrations. Our study obtained toxicity values of 55%, 26%, and 11% at concentrations of 50, 25, and 12.5 ppm, respectively.

Table 2.

Cytotoxic effect of quercetin/curcumin(Q/C) and cisplatin on Capan-1 cells

Compounds (ppm)	Cell Viability(%)
	Quercetin/Curcumin	Cisplatin
50	24	45
25	38	74
12,5	68	89
control	100	100

In vivo tumor growth inhibition by Q/C and combination therapy

All mice in the study developed measurable tumors at the site of injection with Capan-1 cells. By two weeks post-implantation, the mean tumor size was approximately 5–7 mm in diameter across groups, with no significant differences at baseline. Once treatments began, divergent tumor growth trajectories were observed.

Final tumor weight differed across treatment groups by one-way ANOVA (p = 1.2 × 10⁻⁵). The cisplatin + Q/C group had the lowest mean tumor weight, with values lower than those of the control and each monotherapy group (Tukey HSD; adjusted comparisons summarized in Supplementary Table S1). The cisplatin-only and Q/C monotherapy groups showed intermediate weights relative to control, while the prophylactic Q/C group approximated the control distribution. We present group means ± SD with 95% CIs in Table 3, and individual animal values are plotted in Fig. 2.

Table 3.

Final tumor weight and size in each treatment group (day 28)

Group (Treatment)	Mean Tumor Weight (g)	Mean Tumor Dimensions (cm) (L × W × T)	Mean Body Weight (g)
Group 1 – Control	11.3 ± 1.4	3.9 × 2.5 × 2.2	34.4 (M), 28.4 (F)
Group 2 – Cisplatin	7.1 ± 0.8	3.1 × 2.3 × 1.9	34.3 (M), 26.8 (F)
Group 3 – Q/C (Oral)	7.5 ± 1.1	3.05 × 2.58 × 2.11	31.2 (M), 26.2 (F)
Group 4 – Q/C (IP)	7.7 ± 1.0	3.11 × 2.50 × 2.14	32.3 (M), 26.1 (F)
Group 5 – Cisplatin + QC	3.16 ± 0.5	2.3 × 1.9 × 1.23	27.2 (M), 26.3 (F)
Group 6 – Prophylactic Q/C	10.4 ± 1.3	3.7 × 2.66 × 2.26	34.2 (M), 26.1 (F)

Fig. 2.

Final tumor weight by treatment group (one-way ANOVA with Tukey HSD). Each dot represents an individual mouse; horizontal bars indicate mean ± SD (n = 7/group). Omnibus ANOVA p = 1.2 × 10⁻⁵; Tukey HSD pairwise comparisons are reported in Supplementary Table 3

In contrast, mice receiving Q/C showed substantially slower tumor growth. Tumors in the Q/C (oral) group grew at a reduced rate, reaching an average volume of 8,000 mm³ on Day 28, whereas tumors treated with Q/C (IP) were of similar final size (8,000 mm^³). At matched time points, Q/C monotherapy produced ~ 30–40% lower in-life tumor volumes than control, with the corresponding mean differences and 95% confidence intervals reported in the Results. Divergence of growth curves was evident by Week 1 and persisted through the follow-up period, with Q/C-treated tumors remaining consistently smaller than those of the controls. One-way ANOVA evaluated final tumor-weight differences with Tukey HSD, whereas longitudinal volume comparisons are presented descriptively with 95% CIs.

Tumor growth curves in mice bearing Capan-1 pancreatic cancer xenografts under different treatment conditions. Points represent mean tumor volume (mm³) derived from thrice-weekly caliper measurements; values are displayed at weekly intervals (error bars = SEM). Control tumors (yellow) proliferated, reaching more than 10,000 mm³ by Day 28. Cisplatin alone (orange) slowed tumor growth relative to control. The mean necrotic fraction was lower in the cisplatin group (19%) than in the control group (32.5%); however, this difference was not statistically significant (p > 0.05). We therefore present necrosis descriptively and report the mean difference with 95% confidence intervals in Table 4. Q/Cmonotherapy administered orally (red) or intraperitoneally (pink) produced a greater suppression of tumor expansion. The combined treatment with cisplatin + Q/C (blue) showed the most pronounced inhibition of tumor growth, with near-stabilization of tumor size over the first two weeks and only a slight increase thereafter. The prophylactic Q/C group (teal) exhibited a tumor growth curve similar to that of the controls, indicating a minimal preventive effect on tumor establishment. These data demonstrate that Q/C, particularly in combination with cisplatin, impeded pancreatic tumor growth in vivo; the combination arm yielded the smallest end-of-study tumors relative to control and each monotherapy (one-way ANOVA with Tukey HSD; mean differences and 95% CIs reported).

Table 4.

Histopathologic assessment of viable and necrotic tumor areas in Capan-1 xenografts by treatment group

Group	Viable Tumor Area (% of tumor)	Necrotic Area (% of tumor)
1. Control (no treatment)	67.5	32.5
2. Cisplatin only	80.7	19.3
3.Q/C (Oral)	33.3	66.7
4. Q/C (Intraperitoneal)	42.5	57.5
5. Cisplatin + Q/C	52.5	47.5
6. Prophylactic Q/C	79.0	21.0

The cisplatin group exhibited a slight attenuation of tumor growth compared to the controls; however, cisplatin alone showed limited efficacy in this model. After an initial brief stagnation of tumor growth during the cisplatin treatment cycles, tumors in cisplatin-treated mice resumed growth, reaching an average volume of 6500–7000 mm^³ by Day 28. This volume was smaller than that of control tumors (approximately 35–40% reduction in mean volume compared to control) but larger than those in the Q/C groups by the end of the study. These results suggest that the Capan-1 tumors are only partially sensitive to cisplatin. By contrast, Q/C monotherapy achieved tumor growth inhibition of similar magnitude to cisplatin, with mean differences and 95% confidence intervals indicating at most a small advantage for Q/C in this model.

The combination therapy (cisplatin + Q/C) group observed the most striking tumor growth suppression. As shown in Fig. 1 (blue curve), tumors in the combination group barely grew during the first two weeks of treatment, with some tumor shrinkage even noted in the initial phase. By Day 28, combination-treated tumors had reached an average volume of only 2500 mm³, significantly smaller than those in all other groups. Combined therapy reduced the final tumor volume by approximately 75% relative to control. Notably, even after the second cycle of cisplatin (around Day 21), these tumors remained significantly smaller, indicating that Q/C continued to restrain tumor regrowth in the interval between cisplatin treatments. It suggests a strongly additive or synergistic interaction between cisplatin and the Q/C treatment.

In the prophylactic Q/C group (Group 6), the tumor growth pattern did not differ substantially from that of the untreated controls. Tumors still grew aggressively, reaching volumes nearly as large as control tumors by Day 28 (10000 mm³). There was no significant delay in tumor appearance or growth in mice that had received Q/C for 5 days prior to tumor injection. By the end of the study, the average tumor size in the prophylaxis group was slightly lower than that in the control group (5–10%). However, this difference fell within variability and was not statistically meaningful. It indicates that short-term pre-exposure to Q/C, without continued treatment after tumor inoculation, was insufficient to impede tumor establishment or growth in this model.

Overall, these longitudinal measurements indicate that Q/C has an apparent inhibitory effect on tumor growth, and combining Q/C with cisplatin is significantly more effective than cisplatin alone. By the study’s end, precise tumor size and weight differences were apparent among the groups, as summarized in Table 3.

Mean body weight at sacrifice is shown separately for male (M) and female (F) mice in each group (each group had a mix of 3–4 males and 3–4 females). There were no significant differences in body weights between the female groups. Male mice in Group 5 (combination therapy) had a lower terminal body weight (approximately 27.2 g) compared to the other male groups (approximately 32–34 g), suggesting a possible increased systemic effect or toxicity from the combined treatment. No overt toxicities were observed in other groups aside from minor weight differences.

As shown in Table 3, the mean tumor weight in the control group at harvest was 11.3 g, corresponding to large tumor masses occupying much of the flank. Cisplatin treatment reduced the mean tumor weight to 7.1 g, roughly 63% of the control weight. The Q/C monotherapy groups (oral and IP) had mean tumor weights of 7.5 g and 7.7 g, respectively, which were similar to those of the cisplatin group. Thus, after 28 days, tumors from mice treated with either cisplatin or Q/C weighed only about one-third of the weight of untreated tumors. Notably, the cisplatin + Q/C group had a dramatically lower mean tumor weight of 3.16 g, representing only 28% of the control tumor weight (an absolute decrease of 8.14 g). It highlights a strong therapeutic benefit when Q/C is combined with chemotherapy. The combination group’s average tumor weight was less than half that of the next-best single-therapy group. The smallest individual tumor observed in the entire experiment was in a mouse from the combination group, weighing only 2.0 g and measuring 2.0 × 1.5 × 0.9 cm, a striking response compared to untreated tumors.

The mean tumor dimensions in Table 3 further illustrate these differences. On average, control tumors were the largest (3.9 cm in the longest dimension). Cisplatin and Q/C alone yielded tumors around 3.0–3.1 cm in length (with slightly smaller width and thickness). Combination therapy resulted in significantly smaller tumors (2.3 cm long, with widths of 1.9 cm), indicating a substantial reduction in overall tumor volume. Group 6 (prophylaxis) had a mean tumor size (3.7 × 2.66 × 2.26 cm) nearly as large as controls, consistent with its near-control mean weight of 10.4 g. It aligns with the observation that prophylactic Q/C did not significantly prevent tumor growth; those tumors ultimately grew to almost the same size as if no treatment had been given.

In summary, by the end of the study, the ranking of tumor sizes (largest to smallest) was as follows: Control = Prophylactic Q/C > Cisplatin = Q/C (oral) = Q/C (IP) > Cisplatin + Q/C. All treatment groups (Groups 2–5) exhibited a decrease in mean tumor weight and size compared to the control, with the decrease being most pronounced in the combination therapy group (Group 5). In this chemotherapy-resistant model, Q/C monotherapy provided tumor suppression of similar magnitude to cisplatin (mean differences with 95% confidence intervals reported in Results), whereas the Q/C + cisplatin combination produced lower final tumor weights than the control and each monotherapy.

Histopathological findings and tumor necrosis

Upon necropsy, treated tumors often appeared paler or had visible areas of softening/whitish discoloration compared to the control group’s deep, red, uniformly firm tumors. This gross observation suggested necrosis (dead tissue) in the treated tumors. Histological examination with H&E staining confirmed these impressions. The Control group showed densely cellular cancer tissue with malignant glands and clusters of cells with pleomorphic nuclei. Viable tumor cells in the controls exhibited high-grade features, including prominent nuclear atypia, frequent mitotic figures, and a glandular growth pattern typical of adenocarcinoma. Only modest spontaneous necrosis (< 1/3 of the tumor area) was present in control tumors, typically in the central regions of larger tumors, where the blood supply might have been insufficient.

In contrast, tumors from the Q/C-treated groups and the combination group showed extensive areas of necrosis on histological examination. These necrotic regions were characterized by sheets of eosinophilic (pink) amorphous material devoid of nuclei, often infiltrated by neutrophils and containing debris from destroyed cells. At the interface between necrotic and viable tissue, “ghost cells” (tumor cells with faint outlines and lost nuclei) and pyknotic nuclei could be seen, indicating recent cell death. Viable tumor cells in treated groups, when present, were often confined to the periphery of the tumor or in islands surrounded by necrosis. They also tended to exhibit some treatment-related changes: for instance, viable tumor cells in Q/C-treated tumors showed slightly less mitotic activity and more irregular glandular structures than controls, suggesting an effect on tumor proliferation and architecture.

It quantified the extent of tumor necrosis across groups as described in Methods. Table 4 summarizes the mean percentage of necrotic area versus viable tumor area in each group’s tumors.

The control tumors had approximately one-third of their area composed of necrosis (likely due to outgrowing their blood supply in the centers of large tumors) and about two-thirds viable tumor cells. Interestingly, cisplatin-only tumors showed a slightly lower fraction of necrosis (19%) compared to controls, indicating that most (81%) of the tumor tissue remained viable despite cisplatin treatment. It suggests that cisplatin’s cytotoxic effect in this model was not very effective at inducing tumor cell death consistent with the modest tumor size reduction, the drug did not kill a large portion of the tumor mass. By contrast, the oral Q/C group had an average necrotic area of 66.7%, indicating that only one-third of the tumor remained viable. It was the highest necrosis percentage among all groups. Similarly, IP Q/C-treated tumors were, on average, 57.5% necrotic. Thus, Q/C monotherapy (especially via the oral route) produced extensive tumor cell kill, leaving behind large necrotic regions. The combination of cisplatin and Q/C also significantly increased tumor necrosis to 47.5%, which is higher than the control, although somewhat less than Q/C alone. One possible reason the combination group showed a slightly lower necrosis percentage than the Q/C monotherapies is that the overall tumor size in the combination group was much smaller; some of those tiny tumors still contained pockets of viable cells (half the area) rather than being uniformly necrotic. In other words, Q/C alone allowed tumors to grow larger but largely necrotized their interiors, whereas the addition of cisplatin kept tumors small. However, some viable tumors persisted in those small remnants. Regardless, all Q/C-treated groups (Groups 3–5) had a higher necrosis fraction compared to the untreated control (32.5%), indicating the ability of the quercetin–curcumin therapy to induce tumor tissue death. Meanwhile, tumors in the prophylactic Q/C group were primarily viable (79% viable, 21% necrotic), indicating that these tumors had grown unchecked until harvest.

The percentages of necrotic areas followed a decreasing gradient: orally administered Q/C caused the highest necrotic load, intraperitoneal Q/C provided slightly lower but still significant necrosis, and the cisplatin + Q/C combination exhibited moderate levels of necrosis. In contrast, the control group showed limited necrosis compared to the cisplatin and prophylactic Q/C groups. The strikingly high necrosis observed with orally administered Q/C (approaching two-thirds of the total tumor area) demonstrates that enteral administration provides superior intratumoral bioavailability, leading to widespread cell death. Although the peritoneal route was also effective, the oral route resulted in the largest necrotic load, and antitumor activity was observed for both routes. The cisplatin group’s lower necrosis fraction (19%) compared to the control may be explained by cisplatin causing more gradual shrinkage without extensive necrosis, or perhaps by sampling differences; regardless, cisplatin did not increase microscopic necrosis in this model.

Microscopic images support these quantitative findings. Figure 3 shows representative H&E histology from xenograft tumors in selected groups, highlighting viable versus necrotic regions. Panel A shows a section from a control tumor, characterized by densely packed viable tumor cells and minimal spontaneous necrosis. Panel B is from a Q/C–X-treated tumor, illustrating large necrotic areas (pale pink regions lacking nuclei, indicated by black arrows) surrounded by the rim of viable tumor (blue arrows point to darker-staining viable tumor cell clusters). The Q/C treatment has led to massive cell death in the tumor interior. Panel C is from the combination therapy group, showing an overall smaller tumor cross-section. Viable tumor islands (blue arrows) are present but interspersed with significant necrotic zones (black arrows). The necrotic areas often contained neutrophils and fibrin deposits, indicating the body’s attempt to remove dead tissue. In viable zones of treated tumors, tumor cells exhibited nuclear pleomorphism and mitotic figures. However, in combination-treated tumors, the viable cells were often sparse and surrounded by a fibrotic stroma, suggesting tumor regression.

Fig. 3.

Photographs of tumor tissues of each group. A Control group (B) Cisplatin only (C) Q/C administered orally (D) Q/C administered peritoneally (E) Q/C administered via drinking water beginning 5 days before cancer induction (F) Cisplatin + Q/C administered via drinking water. Blue arrows indicate the tumor area, while black arrows indicate the necrosis area. Bar = 100 μm; Hematoxylin & Eosin staining

Microscopic examination also revealed notable cytological and architectural changes in the treated tumors compared to the control. In control tumors, cancer cells grew in poorly formed glands or solid sheets, with frequent atypical mitotic figures (Fig. 4). The cellular density was much lower in treated tumors, especially those from the combination group. Many fields were dominated by ghost cells and karyorrhectic debris. The viable tumor cells that remained often exhibited evidence of cellular stress or injury, with some displaying condensed (pyknotic) nuclei and eosinophilic cytoplasm, indicating ongoing apoptotic cell death in those regions. In Q/C–only groups, an interesting observation was the presence of inflammatory infiltrates (macrophages and neutrophils) around necrotic foci, implying that the therapy may have stimulated an immune response to clear dead tumor cells. No significant differences in tumor morphology were noted between the oral and IP Q/C routes, except for the quantity of necrosis.

Fig. 4.

Microscopic examination also revealed notable cytological and architectural changes

Summarizing the histopathology: Q/C treatment, with or without cisplatin, resulted in significantly higher tumor necrosis compared to controls, corroborating its cytotoxic effect on tumor cells in vivo. Cisplatin alone had a relatively modest histological impact, aligning with its limited efficacy in reducing tumor size. Prophylactic Q/C did not increase necrosis, as those tumors largely resembled histologically (mostly viable tumor) controls. The combination of cisplatin + Q/C produced a strong growth delay and considerable cell kill (nearly half the tumor area was necrotic), indicating that the two modalities worked together to kill tumor cells rather than just slow their proliferation.

Treatment tolerability and systemic effects

All mice survived through the end of the 28-day experiment. General health observations indicated that Q/C was well tolerated when administered either orally or intraperitoneally – mice in Groups 3 and 4 showed no abnormal behavior, maintained their weight (aside from the expected growth in young mice), and exhibited no noticeable side effects (including no diarrhea or skin issues). Mice receiving cisplatin (Groups 2 and 5) showed mild signs of chemotherapy toxicity, such as slight weight loss and transient ruffled fur during the dosing periods. In the combination group (Group 5), male mice experienced a more pronounced weight drop, suggesting that the combined therapy had a greater systemic impact (possibly due to cisplatin toxicity compounded by reduced food/water intake or the additional metabolic load of Q/C). Female weights were relatively similar across groups (26–28 g), indicating that female mice did not experience strong toxicity from these treatments.

There were no clinical signs of acute toxicity. The lack of observed severe toxicity is likely due to the relatively short treatment duration and the use of a robust mouse strain. However, the weight loss in the combination group males suggests that careful monitoring would be needed for any potential dose-limiting toxicities in further studies. No significant differences in organ weights were noted at necropsy among the groups, although detailed pathology was not performed on normal organs.

In summary, Q/C, as monotherapy, was well tolerated in mice, and Q/C did not noticeably exacerbate cisplatin’s toxicity, aside from some additional weight suppression. It is an encouraging sign that Q/C(quercetin + curcumin) could be added to chemotherapy without severe additive side effects, although more extensive toxicological evaluation would be required.

Discussion

This study investigated the therapeutic potential of a combined quercetin–curcumin solution (Q/C) in a pancreatic cancer xenograft model using a chemoresistant human PDAC cell line in vitro and in vivo. In vitro studies suggest that the flavonoids curcumin and quercetin exhibit a relatively low toxic effect on pancreatic cancer, likely due to their low solubility. However, because ionized quercetin/curcumin can penetrate cells, it can kill drug-resistant Capan-1 pancreatic cancer cells more effectively than existing chemotherapeutic agents and treatments. Further improving its solubility and using it in complexes with chemotherapeutic agents are thought to be more effective.

The results demonstrated that Q/C exerts significant antitumor effects in vivo. Q/C, orally or intraperitoneally, substantially slowed tumor growth and reduced final tumor volumes compared to the untreated controls. Perhaps most notably, Q/C dramatically enhanced the efficacy of cisplatin – the combination therapy resulted in the smallest tumors and the greatest tumor weight reduction among all groups. It indicates a synergistic or at least additive interaction betweenQ/C and cisplatin in suppressing tumor progression. By contrast, prophylactic administration of Q/C prior to tumor implantation did not confer protection against tumor growth, suggesting that the continuous presence of the agents during tumor development is necessary to achieve antitumor effects.

These findings align with and expand upon prior evidence regarding the anti-cancer activities of quercetin and curcumin. Quercetin and curcumin have each been shown individually to inhibit growth and induce apoptosis in pancreatic cancer cells [8]. Our in vivo data confirm that when delivered in combination (as Q/C), they can effectively impair tumor growth in a living system and, significantly, do so against a tumor model that is relatively resistant to standard chemotherapy. The Capan-1 cell line is known to be less responsive to standard chemotherapies, such as gemcitabine [18]. While cisplatin is not a standard PDAC drug, its limited effect in our study (a 37% tumor weight reduction) suggests the tumor’s general drug-resistance phenotype. The fact that Q/C alone produced a similar (34%) tumor weight reduction suggests that the quercetin–curcumin combination is overcoming some of the same resistance barriers.

Q/C significantly enhanced cisplatin’s antitumor activity, resulting in approximately a 72% reduction in the final tumor weight, which was more effective than cisplatin alone. Histological examination revealed much larger necrotic areas in tumors treated with Q/C, and it was observed that the quercetin–turmeric combination increased tumor cell death. Mechanistically, quercetin activates intrinsic apoptosis by disrupting mitochondrial function and triggering the activation of caspases. At the same time, curcumin enhances extrinsic apoptosis by upregulating death receptors and suppressing the NF-κB survival pathway, resulting in widespread coagulative necrosis that is subsequently cleared by neutrophils and macrophages. Both polyphenols slow down proliferation: quercetin causes a G1 arrest, while curcumin causes a G2/M arrest and is thought to inhibit angiogenesis by downregulating the VEGF pathway. Additionally, it can be stated that quercetin enhances the tumor’s sensitivity to chemotherapy by inhibiting β-catenin and suppressing cancer stem cell properties. Quercetin is thought to enhance the oral bioavailability of curcumin, thereby increasing its bioavailability and leading to Q/C oral producing the highest necrotic load. Necrosis was scored on H&E without apoptosis or regulated-necrosis markers; therefore, we cannot distinguish ischemic/coagulative necrosis from necroptosis or ferroptosis in this dataset. Future work will incorporate cleaved caspase-3/TUNEL, RIPK3/pMLKL, and ferroptosis/ferritinophagy readouts to define death modalities. We also did not measure pathway modulation in this study (no Western blot, qRT-PCR, or pathway-specific IHC); therefore, we refrain from attributing the combination benefit to specific resistance pathways. Previous reports suggest that curcumin may modulate NF-κB and PI3K/Akt signaling [11].

Our findings are consistent with previous literature that has examined similar combinations. A study by Khan et al. observed that combining quercetin with standard chemotherapy increased apoptosis in cancer cells and reduced tumor growth more than chemotherapy alone [23–26]. In pancreatic cancer specifically, Cao et al. showed that quercetin + gemcitabine can overcome drug resistance, and others have reported that curcumin can sensitize pancreatic tumors to gemcitabine and radiation [8, 11]. Although cisplatin is not typically first-line for PDAC, some studies have looked at platinum in combination with nutraceuticals: for example, curcumin was found to enhance the antitumor effect of oxaliplatin in colorectal cancer models by inhibiting NF-κB and inducing apoptosis. This study appears to be the first to evaluate a quercetin + curcumin formulation (Q/C) in a pancreatic cancer xenograft, demonstrating that this combination can produce meaningful antitumor outcomes.

The lack of effect in the prophylactic group is noteworthy. It suggests that the timing and duration of exposure to these compounds are critical. The 5-day pre-treatment might have been too short to induce any long-lasting protective changes before the tumor took hold. Once the rapidly proliferating Capan-1 cells were implanted, whatever transient effect Q/C had could have been overwhelmed by the aggressive tumor growth. Alternatively, it could indicate that quercetin and curcumin primarily act on existing tumor cells rather than altering the host tissue to prevent initial tumor engraftment. In practice, this suggests that continuous treatment is necessary; using Q/C as a “preventive” supplement alone is unlikely to stop cancer initiation in a high-risk scenario. However, even short-term administration during their growth can have therapeutic benefits once tumors are present. This finding helps define the scope of Q/C’s utility it appears to be more effective as a treatment for active disease rather than a prophylactic agent.

From a safety and translational perspective, it is encouraging that Q/C did not cause apparent toxicity in mice. Both quercetin and curcumin are known for their low toxicity profiles, and humans have consumed them in their diets for centuries. Clinical trials with curcumin up to 8 g/day in humans reported minimal side effects [16]. In translation, clinicians should review SGLT2i exposure when attributing abdominal pain or enzyme elevations to tumor biology, given reported SGLT2i-associated pancreatitis [27]. Quercetin has been given in gram quantities in some trials with manageable safety. Preclinical meta-analytic evidence indicates quercetin confers reno-protection in AKI models via anti-oxidant/anti-inflammatory mechanisms, providing biological plausibility for kidney-sparing effects alongside cisplatin; future studies should incorporate renal biomarkers (e.g., BUN/Cr, NGAL, KIM-1) [28]. Given evidence that METTL14-driven m6A modification sustains c-MYC signaling in PDAC [Li 2024], polyphenol–platinum combinations may offer an advantage by engaging multiple axes inflammatory, redox, and iron-handling rather than relying on a single pathway [22]. Recognizing the bioavailability limitations of polyphenols highlighted by Rajasekaran (2011), a prospective route to separate exposure from mechanism-of-action effects by LC-MS/MS quantification of parent compounds and conjugates in plasma and tumor (target interaction biomarkers) is planned for further comparative PK/PD studies [29].

Quercetin has been given in gram quantities in some trials with manageable safety. Our observation of mild weight loss in the combination therapy group hints that adding quercetin + curcumin could potentially increase chemotherapy side effects. However, it is not easy to separate whether this was due to cisplatin. Importantly, no animals had to be removed from the study due to illness, and no severe adverse effects were observed with the quality control (Q/C) treatment. It supports the notion that using such nutraceutical combinations alongside standard chemo could be feasible. One potential advantage is that if Q/C truly enhances chemotherapy efficacy, it may allow for lower doses of chemotherapy to achieve the same tumor kill, thereby reducing chemotherapy-related toxicity.

The study on Q/C, a combination therapy for pancreatic cancer, found a therapeutic benefit in this model. In some cases, the combination therapy led to a partial remission, similar to the Dhillon clinical trial, where curcumin alone had a limited effect. The study suggests combining quercetin and curcumin in an optimized formulation could improve outcomes when used as adjuncts to chemotherapy.

The results reinforce that multi-target therapies, such as PDAC, can be highly effective against multi-factorial resistant cancers. Pancreatic cancer cells activate numerous survival pathways and have an immunosuppressive microenvironment. Quercetin and curcumin hit a broad swath of these targets, impairing tumor cell survival on multiple fronts. The improved outcome with the combination indicates they complement cisplatin’s mechanism (DNA damage) by simultaneously causing metabolic and signaling collapse in tumor cells, leading to cell death rather than recovery.

This study proves that combining two nutraceutical compounds, quercetin and curcumin, yields significant antitumor activity in pancreatic cancer and can potentiate the effects of conventional chemotherapy. These findings contribute to the growing evidence that natural compounds targeting multiple hallmarks of cancer can augment the treatment of resistant cancers like PDAC. Q/C, as a formulated combination, Q/C could be a promising adjunct in treating pancreatic cancer, potentially improving responses without adding substantial toxicity. Further research, including mechanistic studies and evaluation in more clinically relevant models, is warranted to fully elucidate Q/C’s therapeutic potential and pave the way for possible clinical trials integrating this approach in pancreatic cancer patients.

Conclusion

In a PDAC xenograft model, the quercetin/curcumin (Q/C) formulation reduced intra-life tumor volumes compared with control, and the Q/C + cisplatin regimen produced the lowest end-of-study tumor weights compared with control and each monotherapy (one-way ANOVA with Tukey’s HSD for final tumor weight; longitudinal volumes were mean differences and 95% CI). Q/C monotherapy provided tumor suppression of a similar magnitude to cisplatin and was observed to be more effective than the combination monotherapy. Histology was consistent with reduced tumor burden in the Q/C-containing groups; necrosis was reported descriptively with 95% CI. Taken together with our in vitro data, these findings support the chemosensitizing potential of Q/C in preclinical pancreatic cancer.

These results position Q/C as a candidate adjunct to cytotoxic therapy in pancreatic cancer. Translation will require confirmation in additional PDAC models (including orthotopic and metastatic settings), dose-finding and PK/PD studies, and prospective interaction testing for combination effects. Safety work should include renal monitoring alongside cisplatin and attention to potential clinical confounders in patients (e.g., antidiabetic SGLT2 inhibitor exposure). Mechanistic follow-up should employ predefined biomarker panels spanning inflammatory, redox/iron handling, and transcriptional control pathways to clarify how Q/C may modulate treatment response. Overall, integrating biologically active dietary polyphenols with standard cytotoxics may offer a feasible and potentially safe strategy, but independent validation is needed before clinical claims are made.

Abbreviations

Q/C

Quercetin–Curcumin formulation

PDAC

Pancreatic ductal adenocarcinoma

H&E

Hematoxylin and eosin

ANOVA

Analysis of variance

IACUC

Institutional Animal Care and Use Committee

SEM

Standard error of the mean

Authors’ contributions

**GV** performed the cell culture experiments and MTT cytotoxicity assays.**FABY** designed and coordinated the study, prepared Q/C solutions, conducted data analysis, and oversaw manuscript preparation and revision.**ÖA** established the xenograft animal model, administered treatments, and carried out tumor monitoring and measurements.**NS** conducted the histopathological evaluations, quantified necrosis, and interpreted microscopic findings.**MT** managed the ethical approval process, ensured animal care throughout the experiments, and contributed to data collection.

Funding

This research was supported by internal funds from [Institution/Center Name] and materials provided by Dezonkon Kimya (Konya, Turkey). The sponsor had no direct role in study design, data collection, or interpretation.

Data availability

All data supporting the findings of this study are included in the article and its Supplementary Information. Source data underlying all figures and tables including individual tumor weights, longitudinal tumor-volume measurements, body-weight data, water-intake calculations, necrotic-area quantification, and full ANOVA/Tukey outputs are provided in the Supplementary Data files. Representative H&E histology images are included in the Supplementary Information. Additional raw data can be obtained from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

All animal experimental procedures were approved by the Kırıkkale University Animal Experiments Ethics Committee (Approval Date: 26/03/2024; Decision No: 2024/3–16). The study complied with the institutional guidelines for the care and use of laboratory animals. Animals were housed in a temperature-controlled facility with a 12-hour light/dark cycle and received sterile food and water ad libitum. All efforts were made to minimize animal suffering; mice were monitored daily and humanely euthanized at the study endpoint or if any humane endpoints were reached prior to that time.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.