Cellular reprogramming and signaling control by kaempferol in colorectal cancer

Abstract

Drug resistance and toxicity are major challenges for colorectal cancer (CRC) therapy. Kaempferol (KMP), a natural flavonoid compound, is characterized by low toxicity and multi-targeted effects. KMP has multiple biological functions (anti-inflammation, antioxidation, anti-angiogenesis, apoptosis induction, and immunoregulation). Therefore, KMP is extensively investigated the treatment of various diseases, including cancer. Currently, a series of studies has explored the potential anti-cancer role in CRC therapy. KMP can inhibit the progression of colitis to CRC. Furthermore, KMP suppresses the proliferation of CRC cells and tumor growth. The mechanisms regulated by KMP are involved in multiple signaling pathways such as the matrix metalloproteinases family, VEGF/VEGFR, Wnt/β-catenin, and PI3K/Akt/mTOR. As a multi-targeted inhibitor, KMP shows its natural advantage in combination therapy and is often defined as a sensitizer or attenuator. However, due to the poor stability, absorption, and bioavailability of KMP, its clinical value is hindered. Nano-based delivery systems can compensate for these shortcomings and boost their therapeutic potential. KMP is a hopeful anticancer flavonol, and this review aims to summarize its anticancer effects, mechanisms, and potential applications in CRC.

Graphical abstract

Introduction

Colorectal cancer (CRC) remains a leading malignancy, with an annual burden reaching roughly two million newly diagnosed cases and close to one million deaths [1]. Estimates project an annual increase of 63% in new cases and 73% in deaths by 2040 [2]. Its rising incidence is closely related to rapid urbanization, dietary shifts, and population aging [3]. Despite significant progress in screening and treatment, CRC remains a growing public health challenge.

Current management of CRC typically relies on multimodal strategies, spanning local interventions, systemic chemotherapy, and increasingly, molecularly targeted and immune-based therapies. These treatment strategies have enhanced the therapeutic efficacy and improved the prognosis. However, we have to confront two major challenges: drug resistance and toxicity. 5-fluorouracil (5-FU) is the most effective agent for CRC, but drug resistance remains particularly prominent. Innate and acquired drug resistance often lead to treatment failure and disease progression. While the mechanisms have been extensively explored, drug resistance, including 5-FU resistance, has not been completely overcome. Furthermore, these treatments often cause various serious side effects. For example, chemotherapy-induced myelosuppression and drug-induced dermatitis severely impair patients' tolerability and the quality of life. Additionally, combination therapy may lead to the accumulation of drug-related side effects. [4]. Therefore, there is an urgent need to develop safer, multi-targeted drugs to overcome these limitations.

Natural compounds have gained widespread attention, particularly flavonoids [5, 6]. These plant-derived molecules are characterized by low toxicity and multi-targeted effects [7]. Kaempferol (KMP) is a common dietary flavonoid with multiple biological activities such as anti-inflammation, antioxidation, apoptosis induction, and immunoregulation [8–10]. Research has shown that KMP has protective effects on multiple organs, including the heart [11], liver [12], kidneys [13], bones, and nervous system [14], suggesting its promise in treating associated disorders. Compared with other flavonoids, KMP exerts unique anticancer effects in CRC [15, 16]. KMP prevents the malignant transformation of colitis into CRC [17]. Furthermore, KMP suppresses the proliferation of CRC cells and tumor growth. In addition to the biological activities mentioned above, KMP can also inhibit the growth of CRC through multiple pathways, including the suppression of angiogenesis, post-transcriptional regulation, metabolic reprogramming, and novel forms of programmed cell death. Especially, KMP may improve drug resistance and toxicity. These characteristics make KMP a mechanistically versatile and translationally promising flavonol in CRC. Combination therapy involving KMP, as well as nanoparticle-based delivery strategies, may enhance the translational potential of KMP. This review aims to summarize the anticancer effects, mechanisms, and potential applications of KMP in CRC.

Sources, extraction, and pharmacokinetics of KMP

The chemical name of KMP is 3,5,7-Trihydroxy-2-(4-hydroxy phenyl)-4H-chromen-4-one. It is a natural polyphenol that belongs to the flavonoid class. KMP is a naturally occurring flavonol, widely distributed in the leaves (portulaca oleracea L. [18], ginkgo leaf [19]), flowers (broccoli [20], chrysanthemum [21]), rhizomes (kaempferia galanga [22], astragalus membranaceus [23]), and fruits (apple [24], strawberry [25]) of various plants (Fig. 1). KMP is commonly extracted from plant materials using conventional solvent-based methods, particularly methanolic [26], ethanolic [27], or hydroalcoholic extraction [28]. Following crude extraction, purification is typically achieved through Sephadex LH-20 column chromatography and high-performance liquid chromatography [29]. Ultrasound and microwaves play an auxiliary role in this process [30, 31].

Fig. 1.

Sources and extraction methods of Kaempferol

Oral delivery is the primary way for the intake of KMP and other flavonoids. KMP is mainly absorbed through three mechanisms (active transport, passive diffusion, and facilitated diffusion) in the intestine and colon. Subsequently, KMP enters the circulatory system in both aglycone and glycoside forms [32]. During the metabolic phase, KMP undergoes glucuronidation and sulfonation in the liver [33]. Finally, the metabolites are excreted through urine and feces [34]. It should be known that the free form of KMP exhibits lipophilicity [35]. But KMP is prone to glycosylation, which results in its hydrophilic properties [26]. Low-polarity glycosides are readily absorbed, while high-polarity ones are not. These characteristics determine the poor absorption, stability, and bioavailability of KMP [36]. This is the primary issue to be resolved before the clinical application of KMP.

Anticancer effects and mechanisms of KMP in CRC

Apoptosis induction and anti-proliferation

KMP may have the potential to inhibit the growth of CRC cells. The optimum extract containing KMP inhibited the viability of HT-29 cells [37, 38]. Another work further evaluated the cytotoxicity of 14 plant-derived phytochemicals using the MTT assay, and KMP was found to induce cell death and inhibit the growth of SW1116 cells [39]. Apoptosis, also known as type I programmed cell death, is the greatest barrier to tumor initiation and progression. Inducing apoptosis is an important step in suppressing tumor proliferation, while cell cycle arrest is often a prelude to apoptosis. KMP induced apoptosis and suppressed the proliferation of HCT116 and DLD1 cells [40] (Table 1). Experimental analyses showed that KMP delayed the progression of the G1 phase and then induced apoptosis. KMP induced apoptosis of HCT116 and HT29 cells and significantly inhibited the proliferation, invasion, and migration [41]. Cell-cycle profiling suggests that KMP skewed the population toward a G1-enriched distribution, concomitantly reducing the S-phase fraction. KMP treatment (60 μM) to HT-29 cells caused cell cycle arrest at the G1 phase after 6 h and at the G2/M phase after 12 h [42].

Table 1.

The anticancer effects and mechanisms of kaempferol in colorectal cancer

Classes	Cell lines	Animal Models	Functions and Mechanisms	Refs.
Apoptosis induction and anti-proliferation	HCT116, DLD1	N/A	Inducing apoptosis and suppressing cell proliferation through the miR-339-5p–hnRNPA1/PTBP1–PKM2 signaling axis	[40]
	HCT116, HT-29	N/A	Inducing apoptosis, arresting the cell cycle, and inhibiting proliferation, invasion, and migration through downregulation of MMP-1, MMP-2, and MMP-9 expression	[41]
Anti-angiogenesis	HCT-15, HCT-116	N/A	Inhibiting hypoxia-induced tumor angiogenesis through the HIF-1α/VEGF signaling pathway	[43]
Anti-oxidation and anti-inflammation	N/A	C57 BL/6 mice (male and female, 6 weeks)	inhibiting the progression of colitis to CRC through BCRP and MRP2	[17]
	HCT-15, HCT-116	N/A	Inducing oxidative stress-mediated DNA damage and apoptosis	[43]
Immune regulation	HCT116	BALB/c mice (male, weeks of age unknown)	Inhibiting the expression of IL1B, MMP9, CXCL8, and IL6 and promoting neutrophil activity	[44]
Post-transcriptional regulation	HCT116, HT-29, YB5	C57BL/6 mice (male, 4 weeks)	Inhibiting cell proliferation, migration, and reducing tumor burden via the DNMT1–DACT2–Wnt/β-catenin signaling axis	[45]
	LoVo, SW620, SW480, HCT8, HCT15, HCT116, Caco-2	Nude mice (unspecified)	Inhibiting CRC cell migration and lung metastasis through the circ_0000345-mediated JMJD2C/β-catenin signaling pathway	[46]
Metabolic reprogramming	HCT116, DLD1	N/A	Inhibiting aerobic glycolysis and tumor growth via the miR-339-5p–hnRNPA1/PTBP1–PKM2 signaling axis	[40]
	DLD1, SW620	N/A	Inducing DNA damage via the miR-195/miR-497–PFKFB4-mediated nonoxidative pentose phosphate pathway	[47]
	DLD-1, HCT116, RKO, HT-29, SW480, Caco2; MC38	APCMin/ + , C57BL/6 mice (male, 5–6 weeks)	Suppressing cell proliferation, migration, and tumor growth through the OGT-collagen signaling axis	[48]
Novel programmed cell death	HCT116, HT29, LOVO, SW620, CT26	BALB/c mice (male, 5 weeks)	Inducing ferroptosis through upregulation of Hmox-1 expression	[49]
	CT26, FHC	BALB/c mice (female, 4 weeks)	Inducing pyroptosis through the Ca overload/ER stress/STING/IRF3 signaling pathway	[50]
	RKO, HCT-116	N/A	Suppressing cell proliferation, motility, and invasion and inducing apoptosis and autophagy	[51]

Multiple proteins are associated with the KMP-induced cell cycle arrest and apoptosis [52]. Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases with the function of cleaving the extracellular matrix (ECM) [53]. MMPs are involved in a wide range of physiological and pathological processes, such as tissue remodeling, inflammation, and cancer invasion and metastasis. Surface plasmon resonance revealed a strong binding affinity (6.551 × 10⁻⁶ M) between KMP and MMP3 [54]. Western blot (WB) assay demonstrated that KMP induced cell cycle arrest and apoptosis by inhibiting the expression of MMP-1, MMP-2, and MMP-9 [41]. AURKB is a cell cycle regulatory protein [55]. Molecular docking revealed that KMP formed two hydrogen bonds with AURKB through the residues LEU-83 and PHE-219 [56]. Cellular thermal shift assay and WB assay further confirmed that KMP (100 μM) increased the heat stability of AURKB. Through these key proteins, KMP induces cell cycle arrest and apoptosis, thereby inhibiting tumor cell proliferation.

KMP is also involved in the regulation of several classical signaling pathways. Molecular docking found that KMP strongly bound to PI3K and mTOR proteins [57]. The high affinity of KMP and the PI3K/Akt/mTOR pathway should be further confirmed in experimental studies. KMP promoted apoptosis under hypoxic conditions and was regarded as a multi-pathway inhibitor [43]. First, it enhanced reactive oxygen species (ROS)-induced DNA damage and then triggered intrinsic apoptosis (increased caspase-3/9 activation and decreased Bcl-2 expression). Second, KMP significantly reduced the expression of key molecules such as β-catenin. In short, KMP inhibited the activation of the Wnt/β-catenin axis. Third, KMP markedly suppressed the phosphorylation levels of multiple proteins (Akt, ERK, and p38-MAPK). Finally, KMP weakens the hypoxia-induced cell survival and proliferation.

Anti-angiogenesis

A variety of signaling pathways are associated with tumor angiogenesis of CRC [58]. KMP is capable of interacting with these pathways, such as MMPs [59], VEGF/VEGFR [60, 61], HIF [62], and FGF [63]. However, studies on the anti-angiogenic mechanisms of KMP in CRC are relatively limited. One research analyzed the effects and mechanisms of KMP on HCT-15 and HCT-116 in a hypoxic environment [43]. KMP not only induced intrinsic apoptosis and inhibited cell proliferation but also reduced tumor angiogenesis. In hypoxia-induced conditions, KMP (60 µM) treatment markedly reduced HIF-1α protein levels in both CRC cell lines. A significant downregulation of VEGF was observed in the KMP-treated hypoxic group compared with the control group. Furthermore, KMP markedly suppressed both the activation and expression of VEGFR-2. In addition, KMP also reduced the expression of angiogenic factor ANG-1 that was upregulated under CoCl₂-induced hypoxic conditions. In summary, KMP significantly inhibited the stability of HIF-1α and the expression of its downstream angiogenesis-related genes, thereby blocking hypoxia-induced tumor angiogenesis. However, more evidence is needed to support the notion that KMP inhibits angiogenesis in CRC.

Anti-oxidation and anti-inflammation

Oxidative stress may be a contributing factor in the initiation and progression of CRC [64]. KMP displays significant anti-oxidant and anti-inflammatory effects [65]. Digestive products containing KMP exert anti-inflammatory activity by suppressing NF-κB and activating the Keap1–Nrf2 pathway [66]. The methanolic extract rich in KMP enhanced oxidative stress, caused mitochondrial dysfunction, and ultimately induced apoptosis [67]. The ethanolic extract containing KMP increases ROS production in CRC cells, thereby inducing apoptosis and inhibiting proliferation [68]. Flavonoids containing KMP showed both antioxidant and anticancer activities against HT-29 cells [69]. However, these works only provide indirect evidence. Several other works have further elucidated the antioxidant and anti-inflammatory effects of KMP, as well as their underlying mechanisms. Under hypoxic conditions, KMP markedly increased intracellular ROS levels [43]. Subsequently, KMP induced oxidative stress, resulting in DNA damage and impaired repair. Furthermore, KMP derivatives also showed antioxidant activity and cytotoxicity against CaCo-2 cells, accompanied by necrotic cell death [28].

Several animal models have provided more valuable research findings. In a 1,2-dimethylhydrazine (DMH)-induced CRC rat model, KMP mitigated lipid peroxidation while enhancing enzymatic antioxidant capacity, reflected by increased SOD/CAT/GPx activity [70]. In addition, KMP also exhibited anti-inflammatory effects in mouse models and maintained a high concentration in the intestine through the "enterohepatic triple recycling" [17, 71]. Mechanistic analysis indicated that the inhibitory effect of KMP on the progression of colitis to CRC relied on BCRP and MRP2 [17].

Immune regulation

A series of genes and proteins, such as PD-1 and PD-L1, have been identified as potentially correlated with tumor immunity in CRC. Integrated spectroscopy and molecular dynamics simulations revealed a strong binding affinity between KMP and the extracellular domain of PD-L1 [72]. It is necessary to address the question of how KMP regulates tumor immunity in CRC. Through network pharmacology and bioinformatics analyses, CDKN2A, SERPINE1, and MMP3 were identified as prognostic genes [73]. These prognostic genes displayed a positive correlation with the immune infiltration score. Moreover, KMP was found to bind to these genes and may exert pharmacological effects through these interactions. Another similar study also identified nine genes (e.g., ICAM1, IL6, MMPs) associated with tumor immunity [59]. Molecular docking manifested a strong binding affinity between KMP and these targets. Protein–protein interaction analysis and molecular docking revealed that KMP had strong binding interactions with multiple core targets such as TP53, MAPK1, HSP90AA1, HIF-1A, STAT3, ESR1, JUN, and AKT1 [74, 75]. Therefore, KMP may regulate tumor immunity through classical signaling pathways (p53, HIF-1A, PI3K/Akt, STAT3, MMPs). KMP may further strengthen the antitumor immune response by enhancing the activation and killing capacity of T cells in CRC mice [74]. KMP inhibited the viability of HCT116 cells and promoted their apoptosis [44]. Immune infiltration analysis showed that IL1B, MMP9, CXCL8, and IL6 exerted their anticancer effects mainly by enhancing neutrophil activity.

Although preliminary laboratory data support the immunomodulatory potential of KMP, most existing studies rely on bioinformatics analyses. Evidence derived from in vivo and in vitro experiments remains limited. As an important research direction of CRC, the immunoregulatory effects and mechanisms of KMP should receive greater attention. Further experimental validation, such as co-immunoprecipitation or in vivo studies, is needed to confirm these predictions.

Post-transcriptional regulation

KMP acts on the post-transcriptional regulation and regulates the Wnt/β-catenin axis in CRC. As a tumor suppressor gene, DACT2 is often silenced due to DNA methylation [76]. KMP induced DACT2 demethylation by directly binding to DNA methyltransferase 1 (DNMT1), which significantly reduced its methylation level (approximately 19.58–67.00%) [45]. Subsequently, the Wnt/β-catenin axis was inactivated, and the proliferation and migration of CRC cells were significantly reduced. Consequently, KMP successfully slowed down and reversed CRC tumorigenesis by restoring the epigenetic regulation of DACT2 through the Wnt/β-catenin axis. It is well known that JMJD2C can activate the Wnt/β-catenin axis and promote CRC cell metastasis [77]. A study revealed that miR-205-5p is a key regulatory factor for JMJD2C expression [46]. In this study, KMP inhibited CRC cell migration in vitro and lung metastasis in vivo. Mechanically, KMP downregulated the expression of circ_0000345, which subsequently inhibited the function of miR-205-5p. Thus, KMP suppressed CRC metastasis by inhibiting the circ_0000345-mediated JMJD2C/β-catenin axis. As a multi-targeted inhibitor, KMP may regulate more signaling pathways through post-transcriptional regulation. This could be a promising research direction in the future.

Metabolic reprogramming

Tumor cells often exhibit metabolic reprogramming, tending to acquire ATP and intermediate metabolites through unconventional metabolic pathways. GlcNAcylation is a reversible post-translational modification of proteins that is closely associated with tumor proliferation, metabolic abnormalities, and metastasis [78]. KMP reduced the O-GlcNAcylation modification of Hsp47, leading to decreased maturation and secretion of type I collagen [48]. This process affected ECM remodeling and blocked CRC progression. Thus, KMP showed its anticancer effects by targeting the OGT-collagen axis. O-GlcNAcylation Metabolic reprogramming is subject to post-transcriptional regulation. The Warburg effect suggests that cancer cells preferentially obtain energy through aerobic glycolysis [79]. PKM2 is a rate-limiting enzyme that regulates tumor progression [80]. KMP upregulated the miR-339-5p expression, which mediated the alternative splicing of PKM and then reduced the production of PKM2 [40]. As a result, aerobic glycolysis was inhibited, and the metabolic balance of CRC cells was restored. KMP reversed aerobic glycolysis and inhibited CRC growth by modulating the miR-339-5p–hnRNPA1/PTBP1–PKM2 axis. The pentose phosphate pathway is an important intracellular metabolic pathway, consisting of two types: oxidative and non-oxidative [81]. KMP caused DNA damage and promoted apoptosis via the miR-195/miR-497–PFKFB4-mediated nonoxidative pentose phosphate axis [47]. Specifically, KMP upregulated the expression of miR-195/497. miR-195/497 directly bound to PFKFB4 and then suppressed its expression. Finally, two key enzymes, transketolase and transaldolase, were inhibited. In summary, KMP can reverse the aberrant metabolic reprogramming of CRC cells through post-transcriptional regulation, thereby exerting its anticancer effects.

The induction of novel programmed cell death

In recent years, novel forms of programmed cell death have attracted increasing attention in CRC, including ferroptosis, pyroptosis, and autophagy. Ferroptosis is defined by the accumulation of lipid peroxidation products driven by iron-dependent ROS [82]. Hmox1 belongs to the heme oxygenase family and is the rate-limiting enzyme in heme degradation [83]. Upregulation of Hmox1 increases intracellular iron load and induces ferroptosis. As an active ingredient, KMP may directly upregulate Hmox-1 expression and induce ferroptosis [49]. Further experimental evidence is needed to verify this potential mechanism.

Pyroptosis induces CRC cell death through both typical and atypical pathways [84]. CS-HAP@KAE is a KMP-loaded nanomedicine [50]. When CS-HAP@KAE bound to the CRC cell membrane, KMP promoted calcium influx, led to intracellular calcium overload, and ultimately induced pyroptosis. Mechanically, CS-HAP@KAE induced caspase-1-mediated pyroptosis through the Ca overload/ER stress/STING/IRF3 axis.

Autophagy can maintain cellular homeostasis by degrading long-lived proteins and eliminating abnormal organelles [85]. KMP not only inhibited cell proliferation, motility, and invasion of RKO and HCT-116 cells but also stimulated apoptosis and autophagy [51]. Additionally, KMP treatment also modified the expression of coding and noncoding genes. Research on novel programmed cell death in CRC is rapidly evolving. Increasing evidence suggests that KMP can induce these forms of death through specific mechanisms. These findings provide novel insights for developing CRC therapies.

Combination therapy and nano-delivery

Combination therapy

Owing to its multi-pathway modulation, KMP is often discussed as an adjuvant candidate in combination strategies (Table 2). Sulindac is a non-steroidal anti-inflammatory drug, and fluoxetine is an antidepressant. They have been reported to have the ability to suppress colon carcinogenesis [86, 87]. Using a DMH-induced CRC rat model, KMP enhanced the antiproliferative, pro-apoptotic, and anti-inflammatory activities of sulindac and fluoxetine [88, 89]. Clearly, KMP potentiates their chemopreventive effects against CRC. The combined treatment with KMP and sorafenib induced cell cycle arrest (S and G2/M phases), mitochondrial membrane damage, and finally resulted in apoptosis [39]. KMP synergistically enhances cisplatin-induced apoptosis, characterized by the upregulation of pro-apoptotic factors and the downregulation of anti-apoptotic factors [90]. The combined treatment of KMP and cisplatin induces cell cycle arrest, thereby inhibiting cell division and proliferation. Thus, KMP can enhance the preventive and therapeutic effects of some drugs against CRC.

Table 2.

Kaempferol combined with other drugs for the treatment of colorectal cancer

Combined treatment	Cell lines	Models	Effects and Mechanisms	Refs.
kaempferol + sorafenib	SW1116, SW837	N/A	Inducing cell-cycle arrest and mitochondrial membrane damage, leading to apoptosis	[39]
kaempferol + sulindac kaempferol + fluoxetine	N/A	Sprague–Dawley albino rats (male, 220 ± 30 g)	Enhancing the chemopreventive effects of sulindac and fluoxetine against CRC development	[88, 89]
kaempferol + cisplatin	HCT-15, HCT-116	N/A	Enhancing cisplatin-induced apoptosis through ROS-mediated signaling pathways	[90]
kaempferol + 5-fluorouracil	HCT8-R	N/A	Overcoming 5-FU resistance through modulation of the miR-326–hnRNPA1/A2/PTBP1–PKM2 axis	[91]
kaempferol + 5-fluorouracil	LS174-R	N/A	Enhancing 5-FU sensitivity through ROS modulation and regulation of JAK/STAT3, MAPK, PI3K/AKT, and NF-κB signaling pathways	[92]
kaempferol + 5-fluorouracil	N/A	Wistar rats (male, 300 ± 30 g)	Providing hematopoietic protection, immunomodulation, and hepatic and renal protection, thereby improving survival	[93]

Drug resistance and toxicity remain major challenges in CRC treatment. HCT8-R is a 5-FU–resistant CRC cell line. KMP significantly reduced glucose and lactic acid production uptake [91]. Mechanistically, KMP overcame the resistance to 5-FU by modulating the miR-326–hnRNPA1/A2/PTBP1–PKM2 axis. KMP can chemosensitize 5-FU-resistant LS174-R cells [92]. KMP and 5-FU exerted a strong synergistic inhibitory effect through ROS inhibition and multiple signaling axes, including PI3K/AKT, MAPK, JAK/STAT3, and NF-κB. KMP reduced the toxicity of 5-FU and increased the survival rate of DMH-induced CRC rats [93]. KMP could restore hematological parameters (RBC, Hb, and platelets) and alleviate the suppression of lymphocyte percentage caused by 5-FU, showing hematopoietic protective and immunomodulatory effects. KMP also exerted protective effects on the liver and kidneys of rats. In addition, another work manifested that KMP could reduce the cardiotoxicity induced by 5-FU [94]. Therefore, KMP can serve as both a chemosensitizer and a detoxifying agent for chemotherapeutic drugs.

Oral intake and nano-delivery

The anti-CRC effect of KMP was positively correlated with the dose. KMP inhibited proliferation and induced apoptosis in HCT116 and DLD1 cells, with IC₅₀ values of 63.0 ± 12.9 μM and 98.3 ± 15.9 μM, respectively [40]. Furthermore, the high-dose KMP group (120 μM) exhibited a stronger growth-inhibitory effect than the low-dose group (60 μM) [39]. Therefore, increasing oral intake of KMP may be a potential strategy to enhance its anti-CRC efficacy. A clinical study reported that healthy individuals can tolerate a single oral dose of 10 mg of KMP [95]. Further in vivo and clinical studies are needed to determine the optimal dosage and safety profile.

Another important issue is that the poor absorption, stability, and bioavailability of KMP may limit its application in tumor therapy [96]. It has been reported that derivatization (Kae-SO₃-Ga) can increase the water solubility of KMP [97]. However, more efficient approaches are expected. Nanoparticle-based drug delivery systems offer a range of advantages, including high stability, excellent biocompatibility, resistance to enzymatic degradation, and low toxicity [98]. Loading phytochemicals into this system can enhance their activity and bioavailability against cancers [99]. Nanoencapsulation of polyphenols such as KMP can improve the bioavailability and therapeutic effects [100, 101]. Various KMP-loaded nanomedicines have been developed and applied for the treatment of liver cancer [102, 103], breast cancer [104, 105], lung cancer [106, 107], and glioblastoma multiforme [108].

A variety of KMP-loaded nanomedicines for CRC have been developed and validated (Table 3). Nano-KMP was synthesized using an oil-in-water emulsion technique. It is bound to human serum albumin and human holo-transferrin, which modulated their interaction [109]. MTT assays revealed that Nano-KMP inhibits the viability of SW480 cells in a concentration- and time-dependent pattern. Mechanistic analysis implied that Nano-KMP downregulates the PI3K/Akt/mTOR pathway, leading to cell cycle arrest. KMP can effectively disrupt the regulation of calcium homeostasis and promote calcium influx into tumor cells. This effect was used to develop KMP-loaded nanomedicines [110]. CS-HAP@KAE are constructed from three components: calcium-releasing hydroxyapatite (HAP) nanoparticles (NPs), chondroitin sulfate (CS), and KMP [50]. After binding to the CRC cell membrane, HAP released calcium in the acidic tumor microenvironment (TME), while KMP facilitated the influx of extracellular calcium. These processes collectively led to intracellular calcium overload and induced pyroptosis. KMP and KMP nanoparticles (KPF-NPs) could improve 5-FU-induced cardiotoxicity [94]. This study was conducted by intraperitoneally injecting 5-FU and KMP or KPF-NPs into male Wistar rats. On one hand, KPF and KPF-NPs alleviated oxidative stress and reduced cardiac enzyme levels, COX-2 expression, and VEGF expression. On the other hand, they improved hematological parameters (blood cell counts and hemoglobin levels), mitigated histopathological damage, and increased body weight in the treated rats. Naturally, KPF-NPs demonstrated superior performance compared to KMP. In summary, nanoparticle-based drug delivery systems overcome the limitations of KMP and enhance its anticancer efficacy against CRC.

Table 3.

List of kaempferol-loaded nanomedicines against colorectal cancer

KMP-loaded nanocomposite	Cell lines	Models	Effects	Refs.
CS-HAP@KAE	CT26, FHC	BALB/c mice (female, 4 weeks)	Inducing intracellular calcium overload and inducing pyroptosis	[50]
KPF-NPs	N/A	Male Wistar rats (male, 200–250 g)	Attenuating 5-FU-induced cardiotoxicity	[94]
Nano-KMP	SW480	N/A	Suppressing cell viability and inducing cell-cycle arrest	[109]

Future directions

In this review, we systematically summarize the multifaceted effects, underlying mechanisms, and therapeutic prospects of KMP in CRC (Fig. 2). KMP precisely modulates a range of biological processes, including cell cycle arrest, apoptosis induction, anti-proliferation, anti-angiogenesis, anti-inflammation, anti-oxidation, tumor immunology, post-transcriptional regulation, and metabolic reprogramming. Additionally, KMP also induces novel types of programmed cell death (ferroptosis [49], pyroptosis [50], and autophagy [51]). Multiple genes, proteins, and signaling pathways are crucial for KMP to exert its anti-CRC effects, such as the MMP family, miR-205-5p, and the Wnt/β-catenin axis.

Fig. 2.

Multilevel anticancer mechanisms and translational potential of kaempferol in colorectal cancer

Although the preclinical evidence supporting the anti-CRC effects of KMP is strong, there are several limitations and inconsistencies that need to be addressed. First, the current conclusions are predominantly based on in vitro findings and lack support from in vivo data. Second, poor absorption and metabolism result in low bioavailability of KMP in the human body. Third, few clinical trials or retrospective research on KMP treatment for CRC have been reported.

Currently, there are two approaches to try to solve these problems. KMP should be defined as a sensitizer or attenuator to be used in combination with current mainstream therapies. For instance, KMP can improve the effect of 5-FU and reduce its toxicity [91, 93]. Although KMP is a multi-targeted agent, improving the bioavailability is the fundamental approach to enhancing its anticancer effects. Nanoparticle-based drug delivery systems can precisely deliver a greater amount of KMP to tumor tissues. Various KMP-loaded nanomedicines have been developed and validated in CRC treatments such as CS-HAP@KAE [50], KPF-NPs [94], and Nano-KMP [109]. Therefore, nano-delivery systems or combination therapy represent feasible strategies to enhance the bioavailability and therapeutic efficacy of KMP.

Some clinical studies provide a reference for the use of KMP in treating CRC. A study (UMIN Clinical Trials Registry in Japan, ID: UMIN000049589) involving 16 well-trained male athletes evaluated the impact of a single 10 mg KMP intake on high-intensity exercise capacity [95]. Compared to the control group, KMP significantly reduced VO₂ and respiratory rate during exercise, without concurrent increases in the respiratory quotient or blood lactate levels. Furthermore, it led to a significant increase in exercise duration at 100% VO_2max. Another study further investigated the effects of KMP on hypoxia and inflammatory responses [111]. A botanical preparation containing KMP significantly improved oxygen saturation and lung function parameters (FVC and respiratory volume). It also elevated ATPase activity and glucose levels, while reducing the white blood cell count. These findings highlight the role of KMP in improving organ oxygenation and inflammatory status. As discussed earlier, this constitutes an important mechanism underlying the anti-CRC effects of KMP. Thus, the preliminary clinical data on KMP provide a rationale for considering its evaluation in future clinical trials for CRC.

There is still a long journey ahead before KMP can make its way from the laboratory to the clinic. As works further explore the mechanisms of KMP and confirm its efficacy through clinical trials, its potential as a new therapeutic option for CRC appears increasingly promising.

Conclusions

KMP demonstrates considerable potential as an anti-CRC agent by targeting a variety of crucial biological processes involved in tumor growth, metabolism, angiogenesis, oxidative stress, immune response, metabolic reprogramming, and programmed cell death. In addition, KMP may serve as a valuable adjuvant by enhancing chemosensitivity and alleviating treatment-related toxicity. KMP primarily exerts its anti-CRC effects through several classical signaling pathways, such as the PI3K/Akt, Wnt/β-catenin, MMPs, and VEGF/VEGFR pathways. However, its clinical translation faces significant challenges due to its poor stability, limited bioavailability, and inefficient absorption. Nano-based delivery strategies may partially address these issues. Nanoencapsulation allows for targeted delivery of KMP to tumor tissues, bypassing the barriers associated with traditional oral administration. While preclinical studies provide strong evidence supporting KMP's anti-CRC effects, the lack of sufficient clinical trials remains a critical gap. Further well-designed clinical studies are necessary. These studies will not only validate its effectiveness but also explore the optimal dosing strategies and treatment combinations. In conclusion, KMP shows promise as a potential therapeutic option for CRC, and continued research may help confirm its clinical applicability.

Abbreviations

CRC

Colorectal cancer

KMP

Kaempferol

5-FU

5-Fluorouracil

ECM

Extracellular matrix

MMPs

Matrix metalloproteinases

VEGF

Vascular endothelial growth factor

VEGFR

Vascular endothelial growth factor receptor

HIF-1α

Hypoxia-inducible factor 1 alpha

ROS

Reactive oxygen species

DMH

1,2-Dimethylhydrazine

PD-1

Programmed cell death protein 1

PD-L1

Programmed death-ligand 1

DNMT1

DNA methyltransferase 1

TME

Tumor microenvironment

Author contributions

Bo Wu and Li-li Qiu conceived the study. Bo Wu conducted the investigation and prepared the original draft of the manuscript. Yuan Bu and You-long Liang contributed to manuscript review and editing. Yuan-yuan Tan was responsible for visualization and figure preparation. Li-li Qiu supervised the work. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by Shandong Provincial Natural Science Foundation (Grant No. ZR2023LZY019), Shandong Provincial Traditional Chinese Medicine Science and Technology Project (No. M-2023128), and Doctoral Research Fund of Binzhou Polytechnic (No. 2022bzbs03).

Data availability

No datasets were generated or analysed during the current study.

Declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.