Inulin-based formulations as an emerging therapeutic strategy for cancer: A comprehensive review

Abstract

Cancer stands as the second leading cause of death in the United States (US). Most chemotherapeutic agents exhibit severe adverse effects that are attributed to exposure of drugs to off-target tissues, posing a significant challenge in cancer therapy management. In recent years, inulin, a naturally occurring prebiotic fiber has gained substantial attention for its potential in cancer treatment owing to its multitudinous health values. Its distinctive structure, stability, and nutritional properties position it as an effective adjuvant and carrier for drug delivery in cancer therapy. To address some of the above unmet clinical issues, this review summarizes the recent efforts towards the development of inulin-based nanomaterials and nanocomposites for healthcare applications with special emphasis on the multifunctional role of inulin in cancer therapy as a synergist, signaling molecule, immunomodulatory and anticarcinogenic molecule. Furthermore, the review provides a concise overview of ongoing clinical trials and observational studies associated with inulin-based therapy. In conclusion, the current review offers insights on the significant role of inulin interventions in exploring its potential as a therapeutic agent to treat cancer.

1. Introduction

Cancer stands as the second most prevalent cause of death in the United States (US) and it is a significant global public health concern [1]. The American Cancer Society estimated that around 1,958,310 new cancer cases and 609,820 cancer-related deaths are projected in 2023, in the US. Notably, prostate cancer, lung cancer, bronchus cancer, and colorectal cancer account for 48 % of all incident cases in men, whereas breast cancer, lung cancer, and colorectal cancer account for 52 % of all diagnoses in women [2]. Consequently, cancer poses a substantial health challenge for both genders. The complexity of cancer treatment is evident with traditional methods such as surgery, radiotherapy, and chemotherapy being employed alongside recent advancements like nanoparticles, targeted therapy, natural antioxidants, sonodynamic therapy, radionics, chemodynamic therapy, ferroptosis-based therapy, and ablation therapy [3–7]. A prominent focus of current research is the development of nanomedicines, deemed safe and efficient for cancer treatment. The advent of nanotechnology has revolutionized cancer diagnosis and therapy, leveraging the biocompatibility, low toxicity, stability, precise targeting, amplified retention, and in depth tumor permeability effects of nanoparticles. Particularly, the nanoparticle drug delivery systems utilize tumor and its environmental characteristics. An enormous development has been observed in the delivery of therapeutic or natural active compounds to the target location to treat different ailments [8,9]. Unlike synthetic polymers, natural polysaccharides offer biodegradability and non-toxicity, meeting optimal requirements for drug delivery systems, including stealth and targeting properties [10,11]. Inulin, a US Food and Drug Administration (FDA) approved natural polysaccharide, extracted from plants, stands out for its biodegradability, safety, and cost-effectiveness [12–14]. Due to its unique properties, it has gained recognition as a leading colon-targeting carrier [15–19]. Despite a substantial volume of research on inulin since 1905 with approximately 12,529 peer-reviewed articles available online, a limited global exploration has been conducted on the use of inulin as a nanocarrier for cancer therapy. Fig. 1 provides a visual representation of the number of peer-reviewed articles published on inulin and its applications in cancer therapy either individually or as its nanoparticles (Nanoformulations) according to a thorough PubMed/Medline literature survey using keywords such as inulin, pharmacological effects, nanoformulations, and cancer therapy.

Fig. 1.

Graphical representation of number of peer-reviewed articles related to concerning all types of inulin studies, and inulin applications for cancer therapy alone and as nanoformulations, from 2000 to 2023.

This graph was plotted using Graph Pad Prism version 9.4.0 (Graph pad Software Inc., San Diego, CA) software.

Inulin, a linear fructan and primary storage carbohydrate, is present in approximately 45,000 plant species. It was first discovered by German scientist, Valentine Rose, in 1800s from the roots of Inula helenium, naming it “Inulin” by Thomson in 1817 [20]. In 1864, plant physiologist Julius Sachs identified spherocrystals in the tubers of Inula helenium, Helianthus tuberosus, and Dahlia pinnata. The initial model for biosynthesis of inulin was proposed by Edelman and Jefford in 1968 in Helianthus tuberosus. Maintaining a healthy nutrition regimen can mitigate the risk of communicable diseases, bolster the immune system, extend longevity, and ensure safer childbirths. Inadequate nutrient intake may lead to various ailments, including hypercholesterolemia, hyperglycemia, cancers, and other diseases. Enhancing the nutritional value of food can contribute to its functional qualities, and functional foods, such as inulin, play a crucial role in this regard. Inulin, a naturally occurring prebiotic fiber, is found in chicory, asparagus, leeks, onions, garlic, wheat, soybeans, oats, and Jerusalem artichoke [21]. It is considered an integral part of daily food intake promoting numerous health benefits. Often used as a sugar substitute, inulin provides 10 % of the sweetness of sucrose while contributing only 25–35 % of energy. It has a longstanding history of use by diabetic patients as a sweetener [22]. Additionally, inulin is classified as Fermentable Oligo-, Di-, Monosaccharides, and Polyols (FODMAP), making it valuable in the preparation of low-caloric foods for diabetics due to its slow digestibility and growth-promoting ability of micro-flora. This review delves into the multifaceted role of inulin and its applications in cancer therapy, exploring completed and ongoing clinical trials to provide a comprehensive understanding of its potential in this field.

2. Inulin structure and physicochemical properties

Inulin’s distinctive structure, stability, and nutritional attributes position it as an outstanding carrier for drug delivery in cancer therapy [23]. Inulin is composed of fructose units (n ≥ 60) linked linearly by β-(2➔1) linkages that are attached to (1➔2) α-d-glucopyranose as a terminal group [24]. The presence of β-anomeric carbon renders it indigestible in the human small intestine, however, it can be gradually digested by the micro-flora present in the large intestine [25]. The number of fructose units varies from 2 to 60 in the case of chicory inulin, indicating a combination of polymers and oligomers [26]. Inulin being a hyperdispersed molecule, exhibits diverse physicochemical properties influenced by its polydispersity and polymerization [27]. These characteristics, in turn, are impacted by factors such as plant species, harvesting period, phase in the life cycle, as well as extraction and post-extraction methods [28,29]. Structurally, inulin is a fructan comprising 2 to 100 fructose units linked by β-(2➔1) D-fructosyl-fructose bonds with a terminal glucose unit linked by an α-(1➔2) d-glucopyranosyl bond, akin to sucrose.

Degree of polymerization, for instance short- and long-chain fractions, also affects the functional characteristics of inulin markedly. Short-chain fractions are sweeter and more soluble in water compared to long-chain fractions, which are less soluble, thermostable, and more viscous. A study by Andrew et al. [22] reported that helical conformation of inulin favors a lower degree of polymerization. A conformational state such as zigzag stability of inulin plays a crucial role in its molecular flexibility. Chicory inulin particles are white powdered with greater clarity and the flavor offers no aftertaste with 10 % of the sweetness of sucrose [30]. Inulin shows some similarities to artificial sweeteners such as acesulfame K and aspartame with a little aftertaste [31]. The solubility of chicory inulin in water is nearly 10 % at 25 °C and the usage of hot water (50–100 °C) is recommended to make its solution. Inulin also affects the freezing and boiling points of water to some extent. The critical parameters for inulin hydrolysis are low pH, less dry environments, and high temperature [32,33]. Inulin also shows gelling nature at high level and forms gelling structure with standard chicory inulin (>25 %) and long-chain inulin (>15 %), and the gelling property is greatly influenced by the inulin concentration, shearing factors such as speed, temperature, time, quantity, and the shearing. Cryo-electron microscopic study revealed the 3D structure of inulin gels and are composed of non-soluble submicron fragments in water [34]. The crystalline structure of inulin has two differently shaped morphologies, namely obloid and needle-like, of which the obolid ones develop lubricity of the food and the needle-like crystals enhance viscosity by changing the cooling temperature of inulin from solutions.

3. Sources of inulin

Inulin is a natural polysaccharide with numerous pharmaceutical and food applications. Most of the inulin-containing plants are dicotyledonous which belong to Asteraceae family in addition to some of the monocotyledonous plants from Asparagaceae, Amaryllidaceae, Liliaceae, and Poaceae families [35]. Some of its rich sources are Camassia quamash, Cichorium intybus, Helianthus tuberosus, Allium sativum, Asparagus racemosus, Taraxacum officinale, Dahlia pinnata, Smallanthus sonchifolius, Musa acuminata, and Allium cepa as illustrated in Fig. 2. The structure and rich sources (in % fresh weight) of inulin are summarized in Fig. 2 [36].The details of some inulin-containing plants together with the site of abundance and inulin content have been summarized in Table 1 [37–41].

Fig. 2.

Representation of chemical structure and rich sources of Inulin.

Table 1.

Rich sources of inulin.

Scientific name	Family	Common name	Plant part	Inulin content (%)
Camassia sp.	Asparagaceae	Camas	Bulb	12–22
Cichorium intybus	Asteraceae	Chicory	Roots	15–20
Tragopogon sp.	Asteraceae	Salsify	Roots	15–20
Saussurea lappa	Asteraceae	Kuth	Roots	18–20
Helianthus tuberosus	Asteraceae	Jerusalem Artichoke	Tubers	14–19
Allium sativum	Amaryllidaceae	Garlic	Bulb	9–16
Asparagus officinalis	Asparagaceae	Shatwaar	Root tubers	10–15
Asparagus racemosus	Asparagaceae	Safed Musli/Shatwaar	Root tubers	10–15
Taraxacum officinale	Asteraceae	Dandelion	Leaves	12–15
Microseris lanceolata	Asteraceae	Murnong	Roots	8–13
Dahlia sp.	Asteraceae	Dahlia	Root tubers	9–13
Scorzonera hispanica	Asteraceae	Spanish Salsify	Roots	8.15–10.75
Smallanthus sonchifolius	Asteraceae	Yacon	Roots	3–10
Agave americana	Asparagaceae	Agave	Lobes	7–10
Allium ampeloprasum var. porrum	Amaryllidaceae	Leek	Bulb	3–10
Cynara cardunculus	Asteraceae	Artichoke	Leaves	3–10
Allium cepa	Amaryllidaceae	Onion	Bulb	2–6
Arctium sp.	Asteraceae	Burdock	Roots	3.5–4.0
Hordeum vulgare	Poaceae	Barley	Grains	0.5–1.5
Secale cereale	Poaceae	Rye	Grains	0.5–1.0
Musa acuminata	Musaceae	Banana	Fruit	0.3–0.7

4. Pharmacological activities of inulin

Inulin has critical functional roles for the human body due to its unique structure, rapid water solubility, and low friability [17]. This natural carbohydrate is stable against intestinal and gastric enzymes and helps in the regulation of blood glucose and osteoporosis [42]. Furthermore, it helps in the treatment of constipation and diabetes as it can be fermented by beneficial microorganisms after reaching the colon. It has also been extensively used as a potent macromolecule in drug-delivery systems, synergy, cell signaling mechanism and regulation of the immune system during cancer therapy as discussed later in this review. In addition, a detailed section of different activities of inulin, and the mechanism of actions are summarized in Table 2.

Table 2.

Molecular mechanisms of various pharmacological activities of inulin.

Activity of inulin	Model system	Mechanism of action	References
Antioxidant activities	In vitro (model-free)	Compared to Vitamin C, free radical scavenging activity of inulin was weak and significantly lower as evident from DPPH radical scavenging activity, ABTS scavenging activity and ferric reducing power assays.	[43]
	In vivo (laying hens)	Inulin has shown the significant dose-dependent increase in the levels of MDA and serum antioxidant enzymes such as SOD, CAT, and GSD-Px (p < 0.001).
	Colonic smooth muscle cells	Inulin has shown a significantly higher antioxidant activity compared to simple sugars and remained unaltered regardless of cooking and digestion processes (p < 0.05).	[44]
	In vitro (model-free)	Inulin-containing hydrogels showed controllable antioxidant properties in response to the thermo-sensitive water affinity of the network with a DPPH reduction of 74 % and 55 % in swollen and shrunk states respectively.	[45]
Protection against LPS-induced oxidative stress	Human colonic smooth muscle cell	Pre-incubation of LPS with inulin has shown a significant reduction of maximal acetylcholine (Ach)-induced contraction in smooth muscle cells.	[46]
Immunomodulatory effects in intestine	Intestinal epithelial cells	Regulated the intestinal inflammation (through Treg), maintained intestinal-barrier homeostasis (by expressing tight junction proteins, sIgA and Muc2 in goblet and plasma cells), improved the intestinal barrier (by promoting IL-22 secretion by ILC3s and γδ T cells), enhanced the anti-tumor effect by regulating the epigenetics and inhibiting the tumor growth by infiltration of γδ T cells and CD8+ T cells.	[47]
Anti-obesity	Randomized, double-blinded placebo-controlled study (obese Thai children aged 7–15 years)	Obese children, when supplemented with inulin containing diet, significantly increased the fat-free mass index and decreased the fat mass index (FMI), BMI z-score, and trunk FMI.	[48]
	Randomized, single-blinded, multicentric, placebo-controlled trial was conducted in obese participants (placebo: n = 31, prebiotic: n = 30)	Obese subjects who increased physical activity along with a 3-month intervention with an inulin-enriched diet decreased BMI (−1.6kg/m2), reduced plasma cholesterol and liver enzymes, and increased glucose tolerance.	[49]
Anticancer property	Human colon cell lines (LT97 and HT29); Female BALB/c mice and male C57BL/6 mice (6–8weeks old); Male Swiss mice (6 weeks old)	Inulin stimulated apoptosis and reduced proliferation of tumor cells; stimulated memory T-cell responses, and intensified α-PD-1; significant reduction in the levels of carcinoembryonic antigen and aberrant crypt foci due to the variation of JNK-1/β-catenin signaling mechanism.	[50–52]
Anti-inflammatory activity	Male F344 rats (4–5 weeks old)	Inulin decreased azoxymethane (AOM)-induced carcinogenesis in rats.	[53]
Vaccine adjuvant and delivery system	In Vitro Dendritic Cells (DC2.4)	Soluble inulin microparticles (sIMs) took up the antigen in a higher proportion by >25 times when presented them to antigen-presenting cells (APCs) versus in solution (99 % vs. 22 %).	[54]
	Male BALB/c mice (6–8 weeks old)	sIMs produced robust Th2-type antibody titers (IgG1: 500,000) compared to unadjuvanted antigens (IgG1: 17,500) or alum-adjuvanted antigens (IgG1: 80,000).	[54]
	Randomized clinical subjects (281 adults aged 18–70 years)	11.1-fold raise in antibody titers was noted in 80 % (95 % CI: 52–96) of 18–49 years old who received recombinant hemagglutinin (rHA)-based vaccine (45 μg) with Advax™ adjuvant made of semi-crystalline delta inulin. Advax™ adjuvant increased seroprotection rates by 1.9 times and 2.5 times after the first and the second immunizations respectively, when compared to rHA alone.	[55]
Antiviral activity	Horses, including pregnant mares and foals aged 74–152 days.	Japanese encephalitis virus (JEV) vaccine (JE-ADVAX™) containing delta inulin as an adjuvant proved as a well-tolerated, effective, and safe, in inducing protective levels of JEV-neutralizing antibodies with partial cross-neutralization of Murray Valley encephalitis virus and a new variant strain of Kunjin virus, a subtype of West Nile virus.	[56]
Cartilage regeneration	Bovine chondrocytes	Bovine chondrocytes, when encapsulated during crosslinking of amino-functionalized hyaluronic acid derivatives with divinylsulfone functionalized inulin (INU-DV), sufficiently survived and efficiently proliferated until 28 days of analysis.	[57]
Prebiotic effect	Bifidobacteria and Lactobacilli	Inulin stimulates the growth of beneficial bacteria, such as Bifidobacteria and Lactobacilli, in the colon, promoting a healthy gut microbiota.	[58] [59]
Technological functionality	Model free	Inulin exhibited various technological properties, including gelation, thickening, and structure stabilization, making it widely utilized in the food industry.	[60]
Physiological functionality	Fischer 344 rats (5 weeks old)	Inulin has been shown to have physiological functionalities such as being bifidogenic, laxative, and promoting the production of beneficial short-chain fatty acids in the large intestine.	[61] [59]
Fat replacement	Raw cow’s milk (3 % fat); skim milk and Cream (40 % fat)	Inulin can be used as a fat replacer in food products, affecting properties such as moisture content, firmness, and spreadability.	[62] [63]
Blood pressure regulation	Randomized, placebo-controlled, double-blinded, parallel intervention trial (116 overweight or obese participants)	Systolic (5.35 ± 2.4 mmHg, p = 0.043) as well as diastolic (2.82 ± 1.3 mmHg, p = 0.047) blood pressure has been reduced with the fiber supplementation compared to placebo.	[64]
Antidiabetic	Randomized, triple-blind controlled trial, 49 females (fiber intake <30 g/day) with type 2 diabetes	Inulin supplementation significantly decreased fasting plasma glucose (8.47 %), glycosylated hemoglobin (10.43 %), and malondialdehyde (37.21 %) levels (p < 0.05).	[65]
	Randomized clinical trials (48 adults with prediabetes or at increased risk for T2D)	Supplementation with prebiotic inulin significantly reduced cardiometabolic risk in individuals at risk of T2D (p < 0.05).	[66]
Cardiometabolic disease	Male LDL receptor-deficient mice (7 weeks old)	Inulin-fed mice displayed a decreased C16:0/C24:0 plasma ceramide (Cer) ratio and lower levels of circulating ceramides associated with VLDL and LDL. Liver transcriptomic analysis revealed that Smpd3, a gene that encodes neutral SMase (NSMase), was downregulated by 2-fold in inulin-fed mice. Hepatic NSMase activity was 3-fold lower in inulin-fed mice than in controls. Furthermore, liver redox status and compositions of phosphatidylserine and FFA species, the major factors that determine NSMase activity, were also modified by inulin.	[67]
Anti-hypercholesterolemic effects	Randomized, double-blind, crossover trial (Men and women (n = 21)	Baseline LDL increased significantly during the control phase. There were small, nonsignificant declines in total cholesterol (1.3 %) and LDL-C (2.1 %) during the inulin phase. Differences in response between periods (inulin - control) were significant (p < 0.05) for LDL-C (−14.4 %) and total cholesterol (−8.7 %).	[68]

5. Recent inulin-based nanomaterials and nanocomposites for healthcare applications

Nanotechnology can control the chemotherapies directly or selectively to the cancer cells and neoplasms and offers the enhancement of therapeutic efficacy of current treatment modalities [69]. Nanomaterials and derived nanocomposites can increase the efficacy of the drugs by improving its solubility, bioavailability, and targeting to cancer cells [70,71]. They also have unique physicochemical properties used in the early detection of cancer, need very subtle diagnostic tests, and improve patient prognosis [72,73]. They have demonstrated high utility for biomarker detection by moving away from complicated and invasive procedures [74,75]. Depending on the mechanism of action and kinetics of drugs, multiple drugs may be engineered and be released simultaneously, and the release of the drug occurs via degradation of the carrier, desorption of the drug, diffusion, or triggered release through the nanoparticle matrix [76]. The recent innovations in the areas of nanotechnology have created a bridge for “smart healthcare” for a healthier society. The concept of nanotechnology where particles have a size of <100 nm has been explored for smart biosensors and targeted drug delivery towards an efficient theranostics system [77]. The nanomaterial-based drug delivery system has the potential to bypass biological barriers apart from improving the stability of different therapeutic drugs and their pharmacokinetics and pharmacodynamics [78]. Since inulin has established itself as a promising pharmaceutical agent, recent innovations have been made towards making nanocomposite of inulin with various nanomaterials and nanoarchitectures.

Inulin exerts potential prebiotic effects on the gut by undergoing fermentation in the human colon by the gut microbiota and producing short-chain fatty acids [79–82]. Some of the healthcare applications of inulin-based nanomaterials such as usage of inulin as a coating material, as an adjuvant in vaccine co-formulation, in the delivery of drugs efficiently and for improving the viability of probiotics on electrospun nanofiber mat are briefly explained in Fig. 3.

Fig. 3.

Inulin-based nanomaterials and nanocomposites for healthcare applications.

Ibuprofen-modified inulin was prepared using direct esterification linkage which showed excellent cytocompatibility with the Rat Schwann cell line (RSC-96 cells) [83]. Similarly, delta inulin (Advax^™) was used as an adjuvant to co-formulate gold glyconanoparticles (GNP) vaccine against listeria infection and improve T-cell immunity [84]. Detailed experimentation was done on exploring inulin as a biocompatible coating material for different types of inorganic nanomaterials such as ZnO, Fe₂O_3, etc. [84]. To further extend the application of inulin-based nanocomposite, dual-delivery micelles were synthesized using inulin and vitamin E as the polymeric source to deliver curcumin and celecoxib towards anti-angiogenic activity [85]. This type of delivery system offers enormous potential in diabetic therapy along with cancer therapy. Another work involving micelles synthesis using inulin was reported by Mandracchisa et al. [86] for the delivery of rifampicin (RIF), as the prepared delivery system showed very high delivery of RIF and excellent antibacterial behavior with both gram-positive and negative bacteria. Apart from exploring inulin-based micelles for anti-bacterial applications inulin-conjugated mesoporous silica nanoparticles were prepared to target the gut bacteria [87]. The high affinity with gut bacteria can lead to its possible drug delivery application in the future. Inulin-based nanocomposites have also shown their potential in the oral delivery system. Eroglu and a co-worker prepared sodium alginate/inulin core-shell nano-hydrogels for the controlled delivery of 5-aminosalicylic acid (5-ASA) as an anti-inflammatory drug. The prepared delivery system provided stability to 5-ASA against the stomach’s acidic pH condition thus providing controlled release at the intestine [88].

Inflammatory bowel disease (IBD) is another major area where these inulin-based nanosystems offer significant potential. In view of this, a nanocomposite was prepared of inulin and carbon dot using the self-assembly method and was fluorescent in nature which was able to load apremilast efficiently. It was also able to target inflamed macrophages thus providing the possibility for the macrophage’s targeted drug delivery and offering exciting possibilities for IBD treatment in the future [89]. Apart from applying inulin-based nanomaterials and nanocomposites for the delivery of different therapeutic agents, some recent innovations were also made in the areas of protective capabilities, facilitation of trace metal uptake in cells, anti-hepatoma activities and tissue engineering applications [90–93]. They have shown their potential in different areas of healthcare applications and can transform the pharmaceutical industry with further systematic research ahead.

Recently some research has been made on inulin-based electrospinning and electrospraying for preparing advanced fabrics for different applications. Nagy and co-workers used inulin as a stabilizing excipient in polyvinyl alcohol-polyethylene oxide solution for preparing polymer nanofibers containing Lactobacillus paracasei a probiotic. Inulin helps in the long-term survival of bacteria [94]. In another work, nozzle-free electrospinning was performed to encapsulate Lactobacillus paracasei K₇ within the fibrous network [95]. One of the major advantages of incorporating inulin within the spinning solution is to improve the viability of the probiotics along with modulating the fiber geometry and stability. Furthermore, these fibrous mats containing living probiotic cells help in expanding the durability of functional foods [96]. Some other groups have also explored inulin-based nanofibrous mats for probiotic viability and later they used the same for colon targets, anti-bacterial activities, etc. [97,98]. Considering the potential associated with inulin for improving human health it has paved a new pathway for cancer therapy.

6. Potentiation of cancer therapy by inulin interventions

Cancer, a disease with ever-dynamic nature, devastate tens of millions of lives every year worldwide [99,100]. Despite great advances in medical technology, usage of chemotherapeutics and their severe side effects persists [101–104]. Pain is one of the major side effects that was experienced by the cancer patients during chemotherapy by 66 % at the advanced stage of cancer and 55 % while undergoing cancer therapy [105,106]. Without a distinct pointing approach, chemotherapies may kill noncancerous cells in addition to the cancerous cells, thus causing systemic toxicity that deteriorates the quality of the patient life [107–109]. Therefore, there is a need to shift from existing therapies to new possible ways such as plant-derived products that are effective, innovative, and plausible for cancer therapies. Inulin is one such molecule that has inhibited malignant tumor growth in experimental animals as per the previous study [110]. Some of the strategies of inulin for cancer therapy are described in detail in the following sections and briefly in Fig. 4.

Fig. 4.

Inulin-based strategies for cancer therapy. Inulin can act as a drug carrier and can also modulate the immune system. Furthermore, inulin can generate different signaling molecules leading to their anticancer application and ultimately can provide synergistic effect.

6.1. As a synergist

Therapeutic responses can be improved in terms of magnitude and probability with the help of combination therapies to treat cancer [111]. Usage of affordable drug combinations exhibits potential health benefits which parallelly decrease the multiple risk factors without enhancing the adverse effects. Synergistic effects produced by the combination of drugs result in the reduction of usage of concentration of individual drugs [112]. Combination therapies lead to the reduction of toxicity and drug resistance in addition to enhanced better efficacy. Hence, they have become typical as a promising approach for the treatment of several diseases which is an unmet medical need [113]. Some examples of combination products are drug-drug combinations [114,115] drug-biological agents like monoclonal antibodies in combination with a chemotherapeutic agent to treat cancer, and drug-device combinations such as stents eluted with drugs to treat coronary blockages [115]. The non-soluble fibers have potent tumor-growth-suppressing and anticancer properties. Of these, partially water-soluble dietary fibers possess anticarcinogenic properties and prevent the promotion and initiation phases of carcinogenesis. The health authorities of North America and Europe also recommended that enhancement of dietary fiber in the diet supports reducing the risk of cancer. Inulin is the one that has several therapeutic benefits by decreasing the risk of various cancers, and constipation, enhancing anti-biofilm behavior and calcium absorption of some of the antimicrobial molecules, and possessing antioxidant properties [24].

Studies of fermentation supernatant fraction of inulin in human colon cell lines such as LT97 and HT29, which represents early and late stages of colon cancer, demonstrated that inulin-type fructans stimulated apoptosis and reduced proliferation of tumor cells at different stages of human colon cancer. This supernatant fraction was collected by incubating Synergy 1 (inulin enriched with oligofructose) with fecal inocula under anaerobic conditions [50]. Effects of Synergy 1^® (Chicory inulin) and Metlin^® (from Mexican agave) were analyzed in bone calcium metabolism and colon cancer models in rats and mice and found that inulin-type fructans exhibited increased calcium absorption, anti-inflammatory, and anticancer properties. This study also proved that inulin is a prebiotic that has the potential to improve health and inhibits the development of chronic diseases, namely osteoporosis and cancer [116].

6.2. As an immunomodulant and potent signaling molecule

The immune system is a complex or group comprised of different biological mechanisms and structures that protect the host against harmful pathogens. Impairment in this system causes the host to be susceptible to foreign pathogens leading to cancer [117]. Enhancement in the immune system positively correlates with lesser cancer incidence according to a cohort study performed on individuals with the profound cytotoxic activity of lymphocytes [118]. Specific foods have been shown to possess immunomodulatory effects, offering protection from cancer progression [119]. There is an increase in the usage of functional foods, particularly in Western societies as they boost the immune system by providing metabolic benefits [120,121]. Inulin is a natural, plant-derived prebiotic [122] with many pharmaceutical applications. It has gained much attention for its immunomodulatory activities such as the induction of beneficial effects through direct contact with the immune system by the gut microbiota [25,123–125].

Inulin is the best prebiotic that can be added to food or feed to enhance health-beneficial properties. Immunological activities of inulin-type fructans are produced through direct plus indirect mechanisms as shown in Fig. 5. Dendritic cells exert antigen presentation towards T cells, B cells, and natural killer cells. Gut dendritic cells can recognize inulin-type fructans by pathogen recognition receptors such as Toll-like receptors, nucleotide oligomerization domain-containing proteins (NODs), C-type lectin receptors, and galectins, ultimately inducing anti-inflammatory cytokines. The regular intake of inulin improves blood parameters and modulates immune responses [120,126–128]. In the gut, dietary fructans are fermented to short chain fatty acids (SCFAs) and gases like H₂, bind TLR 2 and TLR 4, stimulate the cells, and thus finally leading to immunomodulation [129].

Fig. 5.

Immunomodulatory activity of fructans. In the gut, dietary fructans are fermented to SCFAs and gases like H₂ [129].

In addition to the immunomodulatory property, inulin is also shown to act as a true signaling compound [125]. It was predicted that prebiotics can directly influence the activity of immune cells irrespective of dependency on the microbiota [130]. Some inulin-type fructans also try to modulate the human peripheral blood mononuclear cells to some extent by TLR 4, 5, 7 and 8. It was reported that TLR4 is the main protein that is involved in stimulating immunity with the help of inulin as a novel adjuvant [131]. A study on Inulin and oligofructose synergy in HLA-B27 transgenic rats showed that there is an increase in the immunomodulatory molecules and a decrease in the tissue proinflammatory cytokines [132]. A study on the combination of prebiotic (inulin) and probiotic (Lactobacillus rhamnosus) in rats demonstrated that probiotics reasonably affected immune functions whereas the prebiotics’ supplementation mainly acted on lymphoid tissue associated with gut [130]. Fructo-oligosaccharides from Allium cepa are inulin-type fructans that possess immunostimulatory properties towards macrophages and murine lymphocytes [133].

The immunomodulatory potential of inulin and heteroglycan was emphasized that human whole blood culture has a prominent response when compared with human leukemia monocytic cell line (THP-1) [134]. Synbiotics (probiotics + prebiotics) supplementation in rats treated with carcinogen altered immune functions by reducing the number of colon tumors in the Peyer’s patches. They contribute to the inhibition of colon carcinogenesis by modulating the gut-associated lymphoid tissue [130]. Minor effects on immune parameters in colon cancer patients were observed when they consumed inulin-enriched oligofructose along with Lactobacillus rhamnosus and Bifidobacterium lactis [135,136].

Inulin enhanced its immunomodulatory role by showing an impact on macrophages directly by stimulating phagocytosis and activating the TLR4 signaling pathway for enhancing immunomodulation [137]. It was observed that there is an increased beta-catenin and cyclin D1 levels with an increase in the size of adenomas in mice in the presence of inulin [138]. It was further evaluated that dietary inulin promoted adenoma growth by increasing cyclin D1 and reducing adhesion proteins in mice mucosa [139]. Inulin-type fructans positively regulate the gene expression related to biotransformation, thus supporting the significant chemo-preventive role of dietary fibers in carcinoma cells [140]. γ-Inulin potentiates the development of CTL-mediated immunity against PDT-treated tumors by acting as a PDT adjuvant [141].

6.3. As an anticarcinogen

Inulin-rich functional foods are redesigned and cost-effective that produce short-chain fatty acids, a potent dietary strategy against colorectal cancer in human populations [59]. The effect of 15 % oligofructose or inulin incorporated into the basal diet for experimental animals demonstrated the potent effects of six various cytotoxic drugs, which could be considered as a novel, nontoxic, easily applicable adjuvant cancer therapy without any side effects for patients [110]. Inulin and oligofructose have crucial roles as anti-carcinogenic and anti-metastatic molecules that have the potential for reducing tumor growth and developing the treatment strategy for colorectal cancer [142]. This is mainly due to the enhancement of bifidobacteria in the colon, which induced preparations of cell walls [143]. The apoptotic and proliferative properties of these prebiotics are mainly related to the reduced glucose availability as a substrate for cancer cells [144–146].

Inulin-derived fermentation products reduced colon cancer by altering differentiation, reducing cell growth and metastasis activities in human cells, as evident from the gradually accumulated fermentation products and inulin-type fructans. This is possibly due to the inhibition of survival of tumor cells and exposure to risk factors, thus exhibited chemopreventive properties [147]. Intestinal flora recovery of gynecologic cancer patients helped them from radiation enteritis by the application of inulin [148,149]. Besides, the application of probiotics in patients suffering from pelvic cancer reduced radiation-induced diarrhea in a dose-dependent manner [150]. A chemotherapeutic agent, doxorubicin, when conjugated with a polysaccharide chain (inulin) showed supportive results when compared to doxorubicin alone [151]. Inulin and polycaprolactone (polyols) together were employed for the preparation of new inulin-based responsive polyurethanes, which are used as intelligent drug release matrices for breast cancer applications [152].

A study on human cancer cell lines such as Hela, HepG2 and 7721, and Skov3 showed that inulin-type fructan (ACPS-1) from Atractylodes chinensis significantly inhibited proliferation of HepG2, Hela, and 7721 with a rate of 87.40 % [153]. Doxorubicin-loaded superparamagnetic iron oxide nanoparticles (SPIONs) coated with a sheath made of PEGy-lated squalene-grafted-inulin amphiphile amplified drug uptake and anticancer efficacies [154]. Inulin or oligofructose incorporation in basal diet inhibits the growth of malignant tumors (transplantable), reduces the incidence of mammary tumors induced by methyl nitrosourea in Sprague-Dawley rats, and lung metastasis of a tumor implanted in mice intramuscularly. Besides, they show a reduction in cancer risk effects and potentiated the effects of cytotoxic drugs applicable for the treatment of human cancer, thus easily applicable as a possible risk-free adjuvant cancer therapy [155]. It was evident that inulin reduces exposure to risk factors and suppresses the survival rate of tumor cells, thus modulating parameters of colon cancer and its risks in human colon cells, in animals as well as in human intervention trials [156].

Inulin gel modulated the microbiome of the gut, stimulates memory T-cell responses, and intensifies α-PD-1 (anti-programmed cell death protein-1) as shown in the study on multiple tumor mice models [51]. In mammary carcinogenesis, inulin and LS/07 (Lactobacillus plantarum) exhibited pro-differentiating, antiproliferative, and immunomodulatory actions that significantly enhanced by co-administration of melatonin [157]. There was a significant reduction in the levels of carcinoembryonic antigen and aberrant crypt foci in the prebiotic-, probiotic- and synbiotic-treated group after the administration of inulin along with Lactobacillus casei or their combinations in mice probably due to the variation of JNK-1/β-catenin signaling mechanism [52].

A study on Swiss male mice, administered with Inulin (50 mg/Kg body weight) orally, suggests that inulin has bio-antimutagenic and desmutagenic mechanisms [158]. In a double-blind, randomized, placebo-controlled trial conducted on women suffering from early-stage breast cancer undergoing neoadjuvant therapy with doxorubicin and cyclophosphamide, inulin supplementation reduced systolic blood pressure and retarded the increase in the diastolic blood pressure, which could be considered an innovative nutraceutical approach during chemotherapy [159]. A study on Sprague-Dawley rats with inulin significantly decreased NF-κB and COX-2-positive cells in the tela submucosa and tunica mucosa of the colon, and reduced the expression of TNF-α, IL-2, and IL-10, thus showing prevention of preneoplastic alterations that induce the development of colon cancer [160].

6.4. As a potent nanocomposite

Inulin and inulin-based nanomaterials have been intensively explored for the treatment of cancer. To start with, a recent study by Vatansever et al. [161] showed that quaternized inulin-coated lipidic nanoparticles enhanced the internalization of nanoparticles to the MDA-MB-231 breast cancer cell lines, leading to a significant toxicity profile compared to the empty lipidic nanoparticles. Besides, inulin polysaccharide-capped selenium nanoparticles were synthesized which showed significant in vitro antiproliferative activity on mouse forest-omach carcinoma cells with a 41.5 % inhibition rate and 38.9 % apoptosis [162]. In another work, inulin-ibuprofen polymer self-assembly was prepared and encapsulated with RGD-targeted epirubicin. This in situ study showed a reduction in toxicity, and higher in vivo antitumor efficacy, histology, and epirubicin biodistribution compared to free epirubicin and nanoparticles [163]. In this scenario, cancer cells efficiently internalized the nanoparticles and exhibited greater apoptosis-inducing ability and cytotoxicity compared to drugs alone. Furthermore, in another work a detailed in vivo study was performed with inulin-based nanoformulations. These nanoformulations were able to accumulate at tumor site for significant time thus providing improved therapeutic efficacy on orthotopic colon cancer [164]. Similarly, chitosan-carboxymethyl inulin nanoparticles that were microencapsulated with mitoxantrone have shown cytotoxic effects on non-neoplastic NIH3T3 cell lines and neoplastic MDA-MB-231. This treatment enhanced NIH3T3 cell survival and killed MDA-MB-231 cells in vitro [165]. Inulin derived from Codonopsis pilosula, when stabilized selenium nanoparticles, showed strong potential application in liver cancer treatments by exhibiting selective anti-hepatoma activities on Huh-7 and HepG2 cells (liver cancer cells) without causing any side effects on 293T (normal cells) [92].

The migration and proliferation of tumors as well as angiogenesis were significantly reduced in transgenic zebrafish models when treated with a concentration range of 1–4 μg/mL of inulin-based selenium nanoparticles (CIP-SeNPs) [166]. Inulin fructan (TMP50-2) isolated from dandelion when fabricated with stable spherical nanoparticles (Tw-TMP-SeNP) showed significant in vitro anti-tumor activity (A549, HepG2, and HeLa cell lines) as well as in vivo (zebrafish model) [167]. High drug encapsulation has been reported in MDA-MB-231 cells when lauryl carbamate derivative of inulin (Inutec-SP1^®, INT) micelles was used during the delivery of chemotherapeutic drugs such as doxorubicin and/or paclitaxel [168]. The toxicity of silver nanoparticles was reduced and biocompatibility of nanoformulation was enhanced by a novel silver-graphene quantum dots (Ag-GQDs) nanocomposite coated with carboxymethyl inulin in the drug delivery strategy against pancreatic cancer in Wistar rats [169]. A study on HeLa (human cervical cancer cells) and A549 (lung cancer cells) cell line models with inulin-coated plasmonic gold nanoparticles loaded with doxorubicin showed increased accumulation and metabolism, and significantly killed target tumor cells compared to doxorubicin alone [170]. Biocompatible inulin, inulin-stearic acid conjugate, delivered genistein in HCT 116 (human colorectal cancer cells), suggesting a way to improve the anticancer property of natural biomolecules like genistein [171]. Doxorubicin-loaded SPIONs amplified uptake and anticancer properties of doxorubicin throughout the tumor mass [154]. A study on inulin multi-methacrylate core covalently linked by targeted peptide RGD reported the high accumulation of doxorubicin metabolite in the tumor cells than that of all other studied organs [172].

A preliminary study by Wu et al. [173] suggested that inulin acetate microspheres were successfully able to deliver loaded model drugs such as chlorhexidine and chymotrypsin for an extended period. Anticancer effect of 7-ethyl-10-hydroxy-camptothecin (SN38) was enhanced when an amphiphilic inulin-thiocholesterol biodegradable conjugate is employed in precision cancer therapies of breast and colorectal cancers [174]. An engineered nanoparticle-based vaccine delivery system with inulin acetate targets dendritic cells, activates maturation markers such as MHC-I, MHC-II, CD40, and CD80, enhances potential applications in cancer immunotherapy, and delivers vaccines against different infectious diseases [175]. Gold/graphene oxide composite coated with inulin-folate conjugate improved the hyperthermia-triggered chemotherapy of paclitaxel and significantly killed cancer cells after photo-thermal treatments. In this study, a biotinylated inulin-doxorubicin conjugate, CJ-PEGBT, was synthesized by linking citraconic acid and pentynoic acid to inulin and conjugated with doxorubicin. This CJ-PEGBT was further added to reduced graphene oxide (RGO), which is more recently proposed as a hyperthermia agent for anticancer therapies that kills cancer cells [176]. There is an enhanced anticancer activity when biotinylated inulin-doxorubicin conjugate is combined with a reduced graphene oxide-based nanosystem, taking hyperthermia and thermoablation phenomena into consideration for the treatment of solid tumors [177].

A study by Kermanian et al. [178] reported the tremendous performance of a super magnetic nanocomposite, Fe-Si-In, which is composed of carboxymethyl inulin-coated core iron oxide nanoparticles with coated inner nonporous silica shell, in MRI with a good contrast enhancement between normal and injured livers in rats. In this study, as shown in Fig. 6, after Fe-Si-In injection, darkness of the T2-weighed MR image is increased due to MR signal attenuation by the distribution of Fe-Si-In molecules into injured cells. This demonstrates the theranostic applications of inulin-based nanoformulation.

Fig. 6.

Good contrast enhancement in MRI of normal and injured livers after administration of Fe-Si-In: (A) T2-weighted MR images (B) Intensity-pixel histograms of T2-weighted MR images (C) Measured T2-weighted contrast (Statistical analysis: The unpaired t-test with Welch’s correction; Error bars: standard deviation (SD), **p < 0.002).

Adapted with permission from ref. [178].

Similarly, usage of inulin-based copolymer (INU-LAPEG-FA) coated FA-SPIONs has efficiently increased the contrast in conventional MRI, offering a potential nanoplatform for the tumor diagnosis and cancer therapy [179]. Efficient and persistent delivery of shRNA to the gut of Apc knockout colon cancer mice models was achieved by using inulin coated arginine stabilized manganese oxide nanocuboids, a promising usage of RNA interference and nanotechnology that encourages the usage of bio-drug in place of chemo-drugs as the future cancer therapeutics. In this study, significant alteration of morphology of crypt-villus to normal after treatment with erythropoietin producing human hepatocellular carcinoma receptor b4 (Ephb4) shRNA conjugated with Inulin coated Mn3O4 nanocuboids (Ephb4 shRNA + NPs) has been observed as shown in Fig. 7 [180].

Fig. 7.

Immunohistochemical analysis of β- catenin, NF-κB and CD44 in colon cancer models after treating with Ephb4 shRNA + NPs. Using Image J software, area of expression was quantified; Error bars: mean ± SD and ***p < 0.001.

Adapted with permission from ref. [180].

Sensitivity to the anticancer agent such as doxorubicin has been enhanced by an increase in the internalization and transfection efficiency of siSUR (a siRNA against surviving mRNA) by novel inulin complex nanoaggregates that are made of chemical functionalization with polyethylenglycol and epidermal growth factor [181]. Inulin copolymer ethylenediamine molecules coat SPIONs (IC-SPIONs) when complexed with siRNA improved oligonucleotide transfection efficiency in cancer and non-tumoral cell line models. This study has potential application as a magnetically targeted drug delivery system in which Inu-EDA copolymer was synthesized by “Enhanced Microwave Synthesis”, stirred with SPIONs and complexed with siRNA to generate the IC-SPIONs/siRNA Magnetoplexes [182].

7. Clinical trials and observational studies

Several controlled clinical trials have confirmed that prebiotics are safe and could be effective in the impediment of acute gastrointestinal conditions [183–186]. Table 3 depicts the status, interventions as well as the ingredients of the supplemented polysaccharides, conditions, respective phase of clinical trials and observational studies on inulin. The study by Hibberd et al. [187] on colon cancer patients who received probiotics supplementation [consisted of two ProBion Clinica (Wasa Medicals AB, Halmstad, Sweden), yielding a daily dose of 0.63 g inulin, ATCC 700396 (7 × 10⁹ CFUs Lactobacillus acidophilus NCFM), and ATCC SD5219 (1.4 × 10¹⁰ CFUs Bifidobacterium lactis Bl-04)] had an increased profusion of Clostridiales and Faecalibacterium species in the fecal microbiota, tumor, and non-tumor mucosa. Similarly, Keane et al. [188] employed Probion Clinica tablet [(Wasa Medicals AB, Halmstad, Sweden); 7 × 10⁹ CFUs Bifidobacterium lactis Bl-04 (ATCC SD5219), 3.5 × 10⁹ CFUs Lactobacillus acidophilus NCFM (ATCC 700396) and 0.32 g inulin/xanthan mix] and demonstrated the suppression of DLG2 expression in colorectal cancer, ulcerative colitis as well as inflammatory bowel disease. A prebiotic mixture, namely Inulin and fructo-oligosaccharide improved the recovery of Bifidobacterium and Lactobacillus from the negative effects in the abdomen post-radiotherapy [189].

Table 3.

List of the clinical trials and observational studies related to inulin [190].

Title	Status	Conditions	Interventions	Identifier	Phase
Atorvastatin calcium, oligofructose-enriched inulin, or sulindac in preventing cancer in patients at increased risk of developing colorectal neoplasia	Completed	Colon cancer; precancerous condition; rectal cancer	Drug: oligofructose-enriched inulin (Raftilose Synergy1: a commercially available powder containing 90 to 94 %, wt/wt inulin and oligofructose, glucose and fructose (4 to 6 %, wt/wt), and sucrose (2 to 4 %, wt/wt; 6 g twice daily); Drug: sulindac; Drug: placebo; Drug: atorvastatin calcium; Other: laboratory biomarker analysis	NCT00335504	Phase 2
Using probiotics to reactivate tumor suppressor genes in colon cancer	Completed	Colon cancer	Dietary supplement: ProBion Clinica (equivalent to a dose of 1.4 × 1010 Bifidobacterium lactis bl-04 (ATCC sd5219), 7 × 109 Lactobacillus acidophilus NCFM (ATCC 700396), and 0.63 g inulin)	NCT03072641	NA
Mixture of prebiotics on intestinal microbiota of patients receiving abdominal radiotherapy.	Completed	Prebiotics; microbiota; radiation therapy complication; endometrial neoplasms	Dietary supplement: 6 g of fiber containing inulin (50 %) and fructo-oligosaccharide (50 %); Dietary supplement: maltodextrin (a homo-oligomer containing 3 to 17 glucose residues per chain)	NCT01549782	NA
Prevention of febrile neutropenia by synbiotics in pediatric cancer patients	Unknown status	Febrile neutropenia; neutropenia; infection in an immunocompromised host; cancer	Dietary supplement: Probio-Fix inum; Dietary supplement: Beneo Synergy 1 (oligofructose-enriched inulin); Other: placebo	NCT02544685	Phase 2
Synbiotics and gastrointestinal function related quality of life after colectomy for cancer	Completed	Colorectal neoplasms	Dietary supplement: Synbiotics (containing 2.5 g of each of the four fermentable fibers (prebiotics) such as b-glucan, inulin, pectin, and resistant starch; Dietary supplement: placebo	NCT01479907	NA
Influence of sulindac and probiotics on the development of pouch adenomas in patients with familial adenomatous polyposis	Unknown status	Adenomatous polyposis coli	Drug: sulindac; Drug: VSL#3® (probiotic); Drug: probiotic-inulin (12 g/day)	NCT00319007	Phase 2
Inositol supplementation to treat PCOS (INSUPP-PCOS)	Recruiting	PCOS; anovulation; hyperandrogenism; insulin resistance; glucose intolerance; metabolic complication	Other: daily placebo (received maltodextrin and inulin); Drug: inositol	NCT03864068	Phase 2
Effect of dietary fiber intervention on patients with polycystic ovary syndrome	Not yet recruiting	PCOS	Dietary supplement: dietary intervention [dietary fiber containing inulin (4 g), resistant starch (4 g), and β-glucan (2 g)]	NCT05431816	NA
The vascular and metabolic effects of sunitinib in patients with metastatic renal cell carcinoma	Completed	Hypertension; renal function; insulin sensitivity; renal cell carcinoma	Not provided	NCT01227213	Observational study
Effect of dietary modification on microbiota in overweight and obese polycystic ovary syndrome patients	Unknown status	PCOS	Dietary supplement: dietary and lifestyle modification and probiotic SANPROBI super formula (containing seven live probiotic bacteria strains and two prebiotics, namely fructo-oligosaccharide, inulin); Other: placebo	NCT03325023	Phase 4

Abbreviations: ATCC: American type cell culture; NA: not applicable; PCOS: polycystic ovary syndrome.

8. Conclusions and future perspectives

In summary, the use of inulin as a synergist, immunomodulant, signaling molecule, and nanomedicine against different cancers offers significant potential for various healthcare applications. The current detailed analysis of the published work on inulin provides information about use of inulin either through diet or as a carrier, furthermore it can mitigate the unintended and undesirable adverse effects induced by the toxicity of anticancer drugs to the off-target sites. Though many studies have been conducted to understand the potency of inulin as a nanocarrier to treat cancer, in-depth studies are still necessary. The current trends on applications of inulin are mainly focused on the development of inulin-based nanoformulations or products, however, more effective, and innovative products and treatments could be expected. Future studies could consider the effects of inulin-based nanoformulations on the treatment of brain tumors, cancer diagnosis, more advancements in cancer immunotherapy, hyperthermia, and thermoablation are also needed. More importantly, in future, well-designed, and long-term randomized controlled trials must be performed to further evaluate the efficacy of inulin-based nanoformulations against different cancers.

Data availability

No data was used for the research described in the article.