Linking Diet to Colorectal Cancer: The Emerging Role of MicroRNA in the Communication between Plant and Animal Kingdoms

The Crucial Roles of Diet, Microbiota, and Postbiotics in Colorectal Cancer

PURPOSE OF REVIEW

Colorectal cancer is the second deadliest cancer in the world, and its prevalence has been increasing alarmingly in recent years. After researchers discovered the existence of dysbiosis in colorectal cancer, they considered the use of probiotics in the treatment of colorectal cancer. However, for various reasons, including the low safety profile of probiotics in susceptible and immunocompromised patient5s, and the risk of developing antibiotic resistance, researchers have shifted their focus to non-living cells, their components, and metabolites. This review aims to comprehensively evaluate the literature on the effects of diet, microbiota, and postbiotics on colorectal cancer and the future of postbiotics.

RECENT FINDINGS

The link between diet, gut microbiota, and colorectal cancer has been established primarily as a relationship rather than a cause-effect relationship. The gut microbiota can convert gastrointestinal tract and dietary factors into either onco-metabolites or tumor suppressor metabolites. There is serious dysbiosis in the microbiota in colorectal cancer. Postbiotics appear to be promising agents in the prevention and treatment of colorectal cancer. It has been shown that various postbiotics can selectively induce apoptosis in CRC, inhibit cell proliferation, growth, invasion, and migration, modulate the immune system, suppress carcinogenic signaling pathways, maintain intestinal epithelial integrity, and have a synergistic effect with chemotherapy drugs. However, it is also reported that some postbiotics are ineffective and may be risky in terms of safety profile in some patients. Many issues need to be researched about postbiotics. Large-scale, randomized, double-blind clinical studies are needed.

An updated review of the pre-clinical role of microRNAs and their contribution to colorectal cancer

Colorectal cancer (CRC) is one of the main causes of malignancy-related mortality worldwide. It was well-identified that microRNAs (miRNAs) decisively participate in cellular biological pathways; in a way that their deregulated expression causes CRC progression. miRNAs can control the translation and degradation of mRNAs by binding to various molecular targets involved in different biological processes, including growth, apoptosis, cell cycle, autophagy, angiogenesis, metastasis, etc. The functions of these dysregulated miRNAs may be either oncogenic or tumor-suppressive. Therefore, these miRNAs can be contributed to prognostic, diagnostic, and therapeutic approaches in CRC. In this study, we reviewed the tumor-suppressive and oncogenic functions of miRNAs in CRC and assessed their molecular activities in CRC development. However, further investigation for the involvement of dysregulated miRNAs in CRC progression is required.

Resistant Starches and Non-Communicable Disease: A Focus on Mediterranean Diet

Resistant starch (RS) is the starch fraction that eludes digestion in the small intestine. RS is classified into five subtypes (RS1-RS5), some of which occur naturally in plant-derived foods, whereas the others may be produced by several processing conditions. The different RS subtypes are widely found in processed foods, but their physiological effects depend on their structural characteristics. In the present study, foods, nutrition and biochemistry are summarized in order to assess the type and content of RS in foods belonging to the Mediterranean Diet (MeD). Then, the benefits of RS consumption on health are discussed, focusing on their capability to enhance glycemic control. RS enters the large bowel intestine, where it is fermented by the microbiome leading to the synthesis of short-chain fatty acids as major end products, which in turn have systemic health effects besides the in situ one. It is hoped that this review will help to understand the pros of RS consumption as an ingredient of MeD food. Consequently, new future research directions could be explored for developing advanced dietary strategies to prevent non-communicable diseases, including colon cancer.

Molecular mechanisms underlying curcumin-mediated microRNA regulation in carcinogenesis; Focused on gastrointestinal cancers

Curcumin is a bioactive ingredient found in the Rhizomes of Curcuma longa. Curcumin is well known for its chemopreventive and anti-cancer properties. Recent findings have demonstrated several pharmacological and biological impacts of curcumin, related to the control and the management of gastrointestinal cancers. Mechanistically, curcumin exerts its biological impacts via antioxidant and anti-inflammatory effects through the interaction with various transcription factors and signaling molecules. Moreover, epigenetic modulators such as microRNAs (miRNAs) have been revealed as novel targets of curcumin. Curcumin was discovered to regulate the expression of numerous pathogenic miRNAs in gastric, colorectal, esophageal and liver cancers. The present systematic review was performed to identify miRNAs that are modulated by curcumin in gastrointestinal cancers.

Dietary microRNAs and cancer: A new therapeutic approach?

Cancer is one of the leading causes of premature death and constitutes a challenge for both low- and high-income societies. Previous evidence supports a close association between modifiable risk factors, including dietary habits, and cancer risk. Investigation of molecular mechanisms that mediate the pro-oncogenic and anti-oncogenic effects of diet is therefore fundamental. MicroRNAs (miRNAs) have received much attention in the past few decades as crucial molecular elements of human physiology and disease. Aberrant expression patterns of these small noncoding transcripts have been observed in a wide array of cancers. Interestingly, human miRNAs not only can be modulated by bioactive dietary components, but it has also been proposed that diet-derived miRNAs may contribute to the pool of human miRNAs. Results from independent groups have suggested that these exogenous miRNAs may be functional in organisms. These findings open the door to novel and innovative approaches to cancer therapy. Here, we provide an overview of the biology of miRNAs, with a special focus on plant-derived dietary miRNAs, summarize recent findings in the field of cancer, address the possible applications to clinical practice and discuss obstacles and challenges in the field.

Dietary patterns and cancer risk

Over the past decade, the search for dietary factors on which to base cancer prevention guidelines has led to the rapid expansion of the field of dietary patterns and cancer. Multiple systematic reviews and meta-analyses have reported epidemiological associations between specific cancer types and both data-driven dietary patterns determined by empirical analyses and investigator-defined dietary indexes based on a predetermined set of dietary components. New developments, such as the use of metabolomics to identify objective biomarkers of dietary patterns and novel statistical techniques, could provide further insights into the links between diet and cancer risk. Although animal models of dietary patterns are limited, progress in this area could identify the potential mechanisms underlying the disease-specific associations observed in epidemiological studies. In this Review, we summarize the current state of the field, provide a critical appraisal of new developments and identify priority areas for future research. An underlying theme that emerges is that the effectiveness of different dietary pattern recommendations in reducing risk could depend on the type of cancer or on other risk factors such as family history, sex, age and other lifestyle factors or comorbidities as well as on metabolomic signatures or gut microbiota profiles.

I. A, Elbehi AM, Cash E, Adeyeye A. The Impact of Diet on the Involvement of Non-Coding RNAs, Extracellular Vesicles, and Gut Microbiome-Virome in Colorectal Cancer Initiation and Progression

Cancer is the major cause of morbidity and mortality in the world today. The third most common cancer and which is most diet related is colorectal cancer (CRC). Although there is complexity and limited understanding in the link between diet and CRC, the advancement in research methods have demonstrated the involvement of non-coding RNAs (ncRNAs) as key regulators of gene expression. MicroRNAs (miRNAs) which are a class of ncRNAs are key players in cancer related pathways in the context of dietary modulation. The involvement of ncRNA in cancer progression has recently been clarified throughout the last decade. ncRNAs are involved in biological processes relating to tumor onset and progression. The advances in research have given insights into cell to cell communication, by highlighting the pivotal involvement of extracellular vesicle (EV) associated-ncRNAs in tumorigenesis. The abundance and stability of EV associated ncRNAs act as a new diagnostic and therapeutic target for cancer. The understanding of the deranging of these molecules in cancer can give access to modulating the expression of the ncRNAs, thereby influencing the cancer phenotype. Food derived exosomes/vesicles (FDE) are gaining interest in the implication of exosomes in cell-cell communication with little or no understanding to date on the role FDE plays. There are resident microbiota in the colon; to which the imbalance in the normal intestinal occurrence leads to chronic inflammation and the production of carcinogenic metabolites that lead to neoplasm. Limited studies have shown the implication of various types of microbiome in CRC incidence, without particular emphasis on fungi and protozoa. This review discusses important dietary factors in relation to the expression of EV-associated ncRNAs in CRC, the impact of diet on the colon ecosystem with particular emphasis on molecular mechanisms of interactions in the ecosystem, the influence of homeostasis regulators such as glutathione, and its conjugating enzyme-glutathione S-transferase (GST) polymorphism on intestinal ecosystem, oxidative stress response, and its relationship to DNA adduct fighting enzyme-0-6-methylguanine-DNA methyltransferase. The understanding of the molecular mechanisms and interaction in the intestinal ecosystem will inform on the diagnostic, preventive and prognosis as well as treatment of CRC.

Induction of Apoptosis in HeLa by Corn Small RNAs

Insights in RNA biology have opened up a plethora of opportunities to explore the small regulatory RNAs from various natural and artificial sources. These small RNAs have been suggested to play a role too in tumor progression by either as oncogenic or tumor suppressor small RNAs. In this study, authors have attempted to evaluate the therapeutic potential of small RNAs fractionated from corn (Zea mays) upon growth and survival of HeLa. Here, authors have employed standard cellular-based approaches including microscopy, spectroscopy, and flow cytometry-based staining assays. Our data indicate that corn small RNAs fraction can appreciably decrease HeLa cell proliferation and survival, which is supported by a number of complementary assays such as Trypan blue dye exclusion, MTT, propidium iodide, and Annexin V/PI apoptotic cell death. Taken together, present finding suggests that corn small RNAs fraction may display up to 70% reduction in HeLa cell viability. Furthermore, these data indicate that around 40-50% of HeLa cells become apoptotic due to exogenous use of corn small. Overall, this finding proposes that possibility of cross-kingdom anticancer use of small RNAs from corn and present data need to be explored in depth.