Microbial dysbiosis and epigenetics modulation in cancer development - A chemopreventive approach.

An overwhelming number of research articles have reported a strong relationship of the microbiome with cancer. Microbes have been observed more commonly in the body fluids like urine, stool, mucus of people with cancer compared to the healthy controls. The microbiota is responsible for both progression and suppression activities of various diseases. Thus, to maintain healthy human physiology, host and microbiota relationship should be in a balanced state. Any disturbance in this equilibrium, referred as microbiome dysbiosis becomes a prime cause for the human body to become more prone to immunodeficiency and cancer. It is well established that some of these microbes are the causative agents, whereas others may encourage the formation of tumours, but very little is known about how these microbial communications causing change at gene and epigenome level and trigger as well as encourage the tumour growth. Various studies have reported that microbes in the gut influence DNA methylation, DNA repair and DNA damage. The genes and pathways that are altered by gut microbes are also associated with cancer advancement, predominantly those implicated in cell growth and cell signalling pathways. This study exhaustively reviews the current research advancements in understanding of dysbiosis linked with colon, lung, ovarian, breast cancers and insights into the potential molecular targets of the microbiome promoting carcinogenesis, the epigenetic alterations of various potential targets by altered microbiota, as well as the role of various chemopreventive agents for timely prevention and customized treatment against various types of cancers.

Fisetin Deters Cell Proliferation, Induces Apoptosis, Alleviates Oxidative Stress and Inflammation in Human Cancer Cells, HeLa.

BACKGROUND: Fisetin, a flavonol profusely found in vegetables and fruits, exhibited a myriad of properties in preclinical studies to impede cancer growth. PURPOSE: This study was proposed to delineate molecular mechanisms through analysing the modulated expression of various molecular targets in HeLa cells involved in proliferation, apoptosis and inflammation. METHODS: MTT assay, flow cytometry, nuclear morphology, DNA fragmentation and Annexin-Pi were performed to evaluate the anti-cancer potential of fisetin. Furthermore, qPCR and proteome profiler were performed to analyse the expression of variety of gene related to cell death, cell proliferation, oxidative stress and inflammation and cancer pathways. RESULTS: Fisetin demonstrated apoptotic inducing ability in HeLa cells, which was quite evident through nuclear morphology, DNA ladder pattern, decreased TMRE fluorescent intensity, cell cycle arrest at G2/M and increased early and late apoptosis. Furthermore, fisetin treatment modulated pro-apoptotic genes such as APAF1, Bad, Bax, Bid and BIK at both transcript and protein levels and anti-apoptotic gene Bcl-2, BIRC8, MCL-1, XIAP/BIRC4, Livin/BIRC7, clap-2/BIRC3, etc. at protein levels to mitigate cell proliferation and induce apoptosis. Interestingly, the aforementioned alterations consequently led to an elevated level of Caspase-3, Caspase-8 and Caspase-9, which was found to be consistent with the transcript and protein level expression. Moreover, fisetin downregulated the expression of AKT and MAPK pathways to avert proliferation and enhance apoptosis of cancer cells. Fisetin treatment also improves oxidative stress and alleviates inflammation by regulating JAK-STAT/NF-kB pathways. CONCLUSION: Together, these studies established that fisetin deters human cervical cancer cell proliferation, enhances apoptosis and ameliorates inflammation through regulating various signalling pathways that may be used as a therapeutic regime for better cancer management.

Quercetin modifies 5'CpG promoter methylation and reactivates various tumor suppressor genes by modulating epigenetic marks in human cervical cancer cells.

The central role of epigenomic alterations in carcinogenesis has been widely acknowledged, particularly the impact of DNA methylation on gene expression across all stages of carcinogenesis is considered vital for both diagnostic and therapeutic strategies. Dietary phytochemicals hold great promise as safe anticancer agents and effective epigenetic modulators. This study was designed to investigate the potential of a phytochemical, quercetin as a modulator of the epigenetic pathways for anticancer strategies. Biochemical activity of DNA methyltransferases (DNMTs), histone deacetylases (HDACs), histone methyltransferases (HMTs), and global genomic DNA methylation was quantitated by an enzyme-linked immunosorbent assay based assay in quercetin-treated HeLa cells. Molecular docking studies were performed to predict the interaction of quercetin with DNMTs and HDACs. Quantitative methylation array was used to assess quercetin-mediated alterations in the promoter methylation of selected tumor suppressor genes (TSGs). Quercetin induced modulation of chromatin modifiers including DNMTs, HDACs, histone acetyltransferases (HAT) and HMTs, and TSGs were assessed by quantitative reverse transcription PCR (qRT-PCR). It was found that quercetin modulates the expression of various chromatin modifiers and decreases the activity of DNMTs, HDACs, and HMTs in a dose-dependent manner. Molecular docking results suggest that quercetin could function as a competitive inhibitor by interacting with residues in the catalytic cavity of several DNMTs and HDACs. Quercetin downregulated global DNA methylation levels in a dose- and time-dependent manner. The tested TSGs showed steep dose-dependent decline in promoter methylation with the restoration of their expression. Our study provides an understanding of the quercetin's mechanism of action and will aid in its development as a candidate for epigenetic-based anticancer therapy.

Chrysin Modulates Aberrant Epigenetic Variations and Hampers Migratory Behavior of Human Cervical (HeLa) Cells.

Purpose: Plant-derived phytochemicals have shown epigenetic modulatory effect in different types of cancer by reversing the pattern of DNA methylation and chromatin modulation, thereby restoring the function of silenced tumor-suppressor genes. In the present study, attempts have been made to explore chrysin-mediated epigenetic alterations in HeLa cells. Methods: Colony formation and migration assays followed by methylation-specific PCR for examining the methylation status of CpG promoters of various tumor-suppressor genes (TSGs) and the expression of these TSGs at the transcript and protein levels were performed. Furthermore, global DNA methylation; biochemical activities of DNA methyltransferases (DNMTs), histone methyl transferases (HMTs), histone deacetylases (HDACs), and histone acetyl transferases (HATs) along with the expression analysis of chromatin-modifying enzymes; and H3 and H4 histone modification marks analyses were performed after chrysin treatment. Results: The experimental analyses revealed that chrysin treatment encourages cytostatic behavior as well as inhibits the migration capacity of HeLa cells in a time- and dose-dependent manner. Chrysin reduces the methylation of various tumor-suppressor genes, leading to their reactivation at mRNA and protein levels. The expression levels of various chromatin-modifying enzymes viz DNMTs, HMTs, HDACs, and HATS were found to be decreased, and H3 and H4 histone modification marks were modulated too. Also, reduced global DNA methylation was observed following the treatment of chrysin. Conclusion: This study concludes that chrysin can be used as a potential epigenetic modifier for cancer treatment and warrants for further experimental validation.

A review on myricetin as a potential therapeutic candidate for cancer prevention.

Myricetin, one of the most extensively studied polyphenols, is present abundantly in various fruits and vegetables and exhibits diverse pharmacological properties. The multifaceted biological action of myricetin against tumor heterogeneity makes it an impressive anticancer agent whose efficacy has been confirmed by an overwhelming number of studies. Myricetin shows its therapeutic potential by targeting and modulating the expression of various molecular target which are involved in inflammation, cell proliferation, apoptosis, angiogenesis, invasion, and metastasis. Myricetin deters tumor progression by inducing apoptosis via both intrinsic and extrinsic pathway, activating/inactivating several signaling pathways, and reactivating various tumor suppressor genes. This comprehensive review represents the effect of myricetin on various hallmarks of cancer with insight into the molecular mechanism employed by myricetin to mitigate cell proliferation, angiogenesis, metastasis, and induce apoptosis. In addition, enhanced bioavailability of myricetin through conjugation and its increased efficacy as an anticancer agent when used in combination are also highlighted.

Quercetin modulates signaling pathways and induces apoptosis in cervical cancer cells.

Cancer cells have the unique ability to overcome natural defense mechanisms, undergo unchecked proliferation and evade apoptosis. While chemotherapeutic drugs address this, they are plagued by a long list of side effects and have a poor success rate. This has spurred researchers to identify safer bioactive compounds that possess chemopreventive and therapeutic properties. A wide range of experimental as well as epidemiological data encourage the use of dietary agents to impede or delay different stages of cancer. In the present study, we have examined the anti-ancer property of ubiquitous phytochemical quercetin by using cell viability assay, flow cytometry, nuclear morphology, colony formation, scratch wound assay, DNA fragmentation and comet assay. Further, qPCR analysis of various genes involved in apoptosis, cell cycle regulation, metastasis and different signal transduction pathways was performed. Proteome profiler was used to quantitate the expression of several of these proteins. We find that quercetin decreases cell viability, reduces colony formation, promotes G2-M cell cycle arrest, induces DNA damage and encourages apoptosis. Quercetin induces apoptosis via activating both apoptotic pathways with a stronger effect of the extrinsic pathway relying on the combined power of TRAIL, FASL and TNF with up-regulation of caspases and pro-apoptotic genes. Quercetin could inhibit anti-apoptotic proteins by docking studies. Further, quercetin blocks PI3K, MAPK and WNT pathways. Anticancer effect of quercetin observed in cell-based assays were corroborated by molecular biology studies and yielded valuable mechanistic information. Quercetin appears to be a promising candidate with chemopreventive and chemotherapeutic potential and warrants further research.