Silibinin and colorectal cancer chemoprevention: a comprehensive review on mechanisms and efficacy

PI3K and tankyrase inhibitors as therapeutic targets in colorectal cancer

INTRODUCTION

The pathways like Wingless-related integration (Wnt/β-catenin) and PI3K play an important role in colorectal cancer (CRC) development; however, their roles are distinct in the process of oncogenesis. Despite their differences, these pathways interact through feedback mechanisms and regulate the common effectors both in the upstream and the downstream processes in normal and pathological conditions. Their ability to reciprocally control each other is a primary resistance mechanism for the selective inhibitors in CRC.

AREA COVERED

This review highlights the Wnt/β-catenin and PI3K pathways that are interrelated in CRC, recent advances and some key perspectives in developing inhibitors that could target the tankyrase enzyme and PI3K, apart from a brief description of the potential of dual inhibitors of PI3K and Tankyrases (TNKS).

EXPERT OPINION

Recent research has focused on overcoming the challenges particularly relating to the resistance and efficacy of dual inhibitors targeting PI3K and tankyrase proteins. Despite these challenges, PI3K as well as tankyrases remain promising therapeutic targets for the treatment of solid tumors. The design of potent inhibitors is crucial to effectively block these protein signaling pathways. Moreover, it is essential to explore the potential of dual-target inhibition of other signaling pathways in conjunction with PI3K and tankyrase.

A Review of Nutraceuticals in Cancer Cachexia

Cancer cachexia is largely characterized by muscle wasting and inflammation, leading to weight loss, functional impairment, poor quality of life (QOL), and reduced survival. The main barrier to therapeutic development is a lack of efficacy for improving clinically relevant outcomes, such as physical function or QOL, yet most nutraceutical studies focus on body weight. This review describes clinical and pre-clinical nutraceutical studies outside the context of complex nutritional and/or multimodal interventions, in the setting of cancer cachexia, in view of considerations for future clinical trial design. Clinical studies mostly utilized polyunsaturated fatty acids or amino acids/derivatives, and they primarily focused on body weight and, secondarily, on muscle mass and/or QOL. The few studies that measured physical function almost exclusively utilized handgrip strength with, predominantly, no time and/or group effect. Preclinical studies focused mainly on amino acids/derivatives and polyphenols, assessing body weight, muscle mass, and occasionally physical function. While this review does not provide sufficient evidence of the efficacy of nutraceuticals for cancer cachexia, more preclinical and adequately powered clinical studies are needed, and they should focus on clinically meaningful outcomes, including physical function and QOL.

Silibinin exhibits anti-tumor effects in a breast cancer stem cell model by targeting stemness and induction of differentiation and apoptosis

Introduction: Malignant breast cancer (BC) frequently contains a rare population of cells called cancer stem cells which underlie tumor relapse and metastasis, and targeting these cells may improve treatment options and outcomes for patients with BC. The aim of the present study was to determine the effect of silibinin on the self-renewal capacity, tumorgenicity, and metastatic potential of mammospheres. Methods: The effect of silibinin on viability and proliferation of MCF-7, MDA-MB-231 mammospheres, and MDA-MB-468 cell aggregation was determined after 72-120 hours of treatment. Colony and sphere formation ability, and the expression of stemness, differentiation, and epithelial-mesenchymal-transition (EMT)-associated genes were assessed by reverse transcription-quantitative polymerase chain reaction (qRT-PCR) in mammospheres treated with an IC₅₀ dose of silibinin. Additionally, the antitumor capacity of silibinin was assessed in vivo, in mice. Results: The results of the present study showed that silibinin decreased the viability of all mammospheres derived from MCF-7, MDA-MB-231, and MDA-MB-468 cell aggregation in a dose-dependent manner. Colony and sphere-forming ability, as well as the expression of genes associated with EMT were reduced in mammospheres treated with silibinin. Additionally, the expression of genes associated with stemness and metastasis was also decreased and the expression of genes associated with differentiation were increased. Intra-tumoral injection of 2 mg/kg silibinin decreased tumor volumes in mice by 2.8 fold. Conclusion: The present study demonstrated that silibinin may have exerted its anti-tumor effects in BC by targeting the BC stem cells, reducing the tumorgenicity and metastasis. Therefore, silibinin may be a potential adjuvant for treatment of BC.

Chiral Flavonoids as Antitumor Agents

Flavonoids are a group of natural products with a great structural diversity, widely distributed in plant kingdom. They play an important role in plant growth, development and defense against aggressors. Flavonoids show a huge variety of biological activities such as antioxidant, anti-inflammatory, anti-mutagenic, antimicrobial and antitumor, being able to modulate a large diversity of cellular enzymatic activities. Among natural flavonoids, some classes comprise chiral molecules including flavanones, flavan-3-ols, isoflavanones, and rotenoids, which have one or more stereogenic centers. Interestingly, in some cases, individual compounds of enantiomeric pairs have shown different antitumor activity. In nature, these compounds are mainly biosynthesized as pure enantiomers. Nevertheless, they are often isolated as racemates, being necessary to carry out their chiral separation to perform enantioselectivity studies. Synthetic chiral flavonoids with promising antitumor activity have also been obtained using diverse synthetic approaches. In fact, several new chiral bioactive flavonoids have been synthesized by enantioselective synthesis. Particularly, flavopiridol was the first cyclin-dependent kinase (CDK) inhibitor which entered clinical trials. The chiral pool approaches using amino acid as chiral building blocks have also been reported to achieve small libraries of chrysin derivatives with more potent in vitro growth inhibitory effect than chrysin, reinforcing the importance of the introduction of chiral moieties to improve antitumor activity. In this work, a literature review of natural and synthetic chiral flavonoids with antitumor activity is reported for the first time.

A Comprehensive Overview of Colon Cancer- A Grim Reaper of the 21st Century

A few decades ago, the incidence of colorectal cancer (CRC) was low and is now the fourth in the list of deadly cancers producing nearly a million deaths annually. A population that is aging along with risk factors such as smoking, obesity, sedentary lifestyle with little or no physical activity, and non-healthy food habits of developed countries can increase the risk of colorectal cancer. The balance in gut microbiota and the metabolites produced during bacterial fermentation within the host plays a significant role in regulating intestinal diseases as well as colorectal cancer development. Recent progress in the understanding of illness resulted in multiple treatment options such as surgery, radiation, and chemotherapy, including targeted therapy and multitherapies. The treatment plan for CRC depends on the location, stage and grade of cancer as well as genomic biomarker tests. Despite all the advancements made in the genetic and molecular aspects of the disease, the knowledge seems inadequate as the drug action as well as the wide variation in drug response did not appear strongly correlated with the individual molecular and genetic characteristics, which suggests the requirement of comprehensive molecular understanding of this complex heterogeneous disease. Furthermore, multitherapies or a broad spectrum approach, which is an amalgamation of the various promising as well as effective therapeutic strategies that can tackle heterogeneity and act on several targets of the disease, need to be validated in clinical studies. The latest treatment options have significantly increased the survival of up to three years in the case of advanced disease. The fact that colorectal cancer is developed from a polypoid precursor, as well as the symptoms of the disease that occur at an advanced stage, underlines how screening programs can help early detection and decrease mortality as well as morbidity from CRC.

Silibinin Triggers the Mitochondrial Pathway of Apoptosis in Human Oral Squamous Carcinoma Cells

Background:

Silibinin, a natural polyphenolic flavonoid present in seed extracts of milk thistle (Silybum marianum). It has been shown to interact with various cancer-related cell signalling pathways in preclinical models, demonstrating promising anticancer effects in vitro and in vivo.

Materials and Methods:

The cytotoxic effect of silibinin was evaluated in human oral squamous carcinoma (SCC-25) cells by MTT assay. The apoptosis-related morphological changes were investigated by AO/EB dual staining. The cytochrome c, caspases-3, and -9, B-cell lymphoma-2 (Bcl-2), and B-cell associated X protein (Bax) gene expressions were analysed by PCR.

Results:

We have shown that silibinin treatment for 24 h in SCC-25 cells induced cytotoxicity in a concentration-dependent manner. The cytotoxic potential was due to the induction of apoptosis via the release of mitochondrial cytochrome c into the cytosol and subsequent activation of caspases-3 and -9. Dual staining assay was further confirmed the induction of early apoptosis upon silibinin treatment.

Conclusion:

The results from this study show that silibinin can be considered as a promising drug candidate for the treatment of oral squamous cell carcinoma.

Comprehensive analysis of expression profiles of long non‑coding RNAs with associated ceRNA network involved in gastric cancer progression

Long non-coding RNAs (lncRNAs) play critical roles in the development and progression of cancers. The present study aimed to identify novel lncRNAs and associated microRNAs (miRNAs or miRs) and mRNAs in gastric cancer. Differentially expressed lncRNAs (DElncRNAs) and differentially expressed mRNAs (DEmRNAs) of 6 paired gastric cancer and normal tissues were identified using microarray. The DEmiRNAs between gastric cancer and the normal control tissues were identified using miRNA-seq data from Cancer Genome Atlas. Common DElncRNAs from the Cancer RNA-Seq Nexus database and circlncRNAnet database were analyzed. A DElncRNAs-DEmiRNAs-DEmRNAs network was constructed by target prediction. Functional enrichment analysis was employed to predict the function of DEmRNAs in the network. The correlation between the expression of DElncRNAS and DEmRNAs in the network was analyzed. The expression levels of several genes were validated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). A total of 1,297 DElncRNAs, 2,037 DEmRNAs and 171 DEmiRNAs were identified. Among the 4 lncRNAs common to the 3 datasets, prostate androgen-regulated transcript 1 (PART1) was selected for further analysis. The analysis identified 5 DEmiRNAs and 13 DEmRNAs in the PART1-mediated ceRNA network. The DEmRNAs in the ceRNA network were markedly enriched in cancer-related biological processes (response to hypoxia, positive regulation of angiogenesis and positive regulation of endothelial cell proliferation) and pathways (cGMP-PKG signaling pathway, cAMP signaling pathway and proteoglycans in cancer). Out of the 13 DEmRNAs, 11 were positively associated with PART1. The downregulation of PART1, myosin light chain 9 (MYL9), potassium calcium-activated channel subfamily M alpha 1 (KCNMA1), cholinergic receptor muscarinic 1 (CHRM1), solute carrier family 25 member 4 (SLC25A4) and ATPase Na⁺/K⁺ transporting subunit alpha 2 (ATP1A2) expression levels in gastric cancer was validated by RT-qPCR. On the whole, the current study identified a novel lncRNA and associated miRNAs and mRNAs that are involved in the pathogenesis of gastric cancer that may serve as potential therapeutic targets for the treatment of gastric cancer.

Combination of Epigallocatechin-3-gallate and Silibinin: A Novel Approach for Targeting Both Tumor and Endothelial Cells

Despite promising benefits, anti-angiogenic strategies have revealed several drawbacks, which necessitate development of novel approaches in cancer therapy strategies including non-small-cell lung cancer, as one of the leading causes of cancer death, all over the world. Combination of flavonoids could be a safe and effective option to synergize their impact on mechanisms controlling tumor angiogenesis. In this study, we have investigated the plausible synergism of epigallocatechin-3-gallate (EGCG) and silibinin on endothelial cells, for the first time. Cell viability and migration were evaluated by survival and wound healing assays, respectively. Then, we assessed the expression of VEGF, VEGFR2, and miR-17-92 cluster using real-time polymerase chain reaction in endothelial-tumor cell and endothelial-fibroblast coculture models. EGCG ± silibinin suppressed endothelial and lung tumor cell migration in lower than 50% toxic doses. VEGF, VEGFR2, and pro-angiogenic members of the miR-17-92 cluster were downregulated upon treatments. Specifically, the combination treatment upregulated an anti-angiogenic member of the cluster, miR-19b. Our data provides evidence to utilize the EGCG and silibinin combination as a novel approach to target tumor angiogenesis in the future.

Role of mast cells in the generation of a T-helper type 2 dominated anti-helminthic immune response

Mast cells are long-lived, innate immune cells of the myeloid lineage which are found in peripheral tissues located throughout the body, and positioned at the interface between the host and the environment. Mast cells are found in high concentrations during helminth infection. Using Kitw-sh mast cell deficient mice, a recently published study in Bioscience Reports by Gonzalez et al. (Biosci. Rep., 2018) focused on the role of mast cells in the immune response to infection by the helminth Hymenolepis diminuta The authors showed that mast cells play a role in the modulation of Th2 immune response characterized by a unique IL-4, IL-5 and IL-13 cytokine profile, as well as subsequent robust worm expulsion during H. diminuta infection. Unlike WT mice which expelled H. diminuta at day 10, Kitw-sh deficient mice displayed delayed worm expulsion (day 14 post infection). Further, a possible role for mast cells in the basal expression of cytokines IL-25, IL-33 and thymic stromal lymphopoietin was described. Deletion of neutrophils in Kitw-sh deficient mice enhanced H. diminuta expulsion, which was accompanied by splenomegaly. However, interactions between mast cells and other innate and adaptive immune cells during helminth infections are yet to be fully clarified. We conclude that the elucidation of mechanisms underlying mast cell interactions with cells of the innate and adaptive immune system during infection by helminths can potentially uncover novel therapeutic applications against inflammatory, autoimmune and neoplastic diseases.

Chemopreventive Effects of Silibinin on Colitis-Associated Tumorigenesis by Inhibiting IL-6/STAT3 Signaling Pathway

Inflammatory bowel disease (IBD), characterized by sustained inflammation, is a latent risk factor of colon tumorigenesis. Silibinin has been reported to be anti-inflammatory and antineoplastic, but its efficacy on colitis-associated cancer (CAC) has not been reported. Interlukin-6/signal transducer and activator of transcription 3 (IL-6/STAT3) is the key signaling pathway involved in CAC. We evaluated the chemopreventive effect of silibinin on a CAC mouse model and determined its impact on IL-6/STAT3 signaling. Intestinal tumor cells (IMCE and HCT-116 cell lines) were also treated by graded concentration of silibinin, and cellular viability was determined. Silibinin (750 mg/kg/day) was administered to an azoxymethane/dextran sulfate sodium (AOM/DSS) C57BL/6 mouse model for 10 weeks by gavage. Body weight, colon length, and the amount and diameter of colon tumors were documented, respectively. Specimens were subjected to H&E staining for colitis and tumor scoring, immunohistochemical staining and terminal deoxynucleotidyl transferase dUTP nick end labeling for proliferation assessment, and immunofluorescent staining for intestinal mucosa barrier assessment. Production of inflammatory cytokines was determined by real-time PCR. IL-6/STAT3 pathway activation was evaluated through immunohistochemical staining and western blot. In the current study, silibinin significantly inhibited the viability of intestinal tumor cells. The production of inflammatory cytokines and the phosphorylation of STAT3 were both inhibited in intestinal tumor cells. Meanwhile, silibinin decreased the amount and size of tumors in AOM/DSS mice. Colitis and tumor scores were decreased accompanying with inhibition of colonic tumor cell proliferation and promotion of cellular apoptosis. Additionally, silibinin could reduce the production of inflammatory cytokines and attenuate the impairment of colonic mucosal barrier. Furthermore, STAT3 phosphorylation was significantly suppressed by silibinin. In conclusion, silibinin could protect against colitis-associated tumorigenesis in mice via inhibiting IL-6/STAT3, which showed promising chemopreventive potential of CAC.