Investigating the regulatory role of miRNAs as silent conductors in the management of pathogenesis and therapeutic resistance of pancreatic cancer

Pancreatic cancer (PC) has the greatest mortality rate of all the main malignancies. Its advanced stage and poor prognosis place it at the bottom of all cancer sites. Hence, emerging biomarkers can enable precision medicine where PC therapy is tailored to each patient. This highlights the need for new, highly sensitive and specific biomarkers for early PC diagnosis. Prognostic indicators are also required to stratify PC patients. To avoid ineffective treatment, adverse events, and expenses, biomarkers are also required for patient monitoring and identifying responders to treatment. There is substantial evidence that microRNAs (miRs, miRNAs) play a critical role in regulating mRNA and, as a consequence, protein expression in normal and malignant tissues. Deregulated miRNA profiling in PC can help with diagnosis, treatment planning, and prognosis. Furthermore, knowledge of the primary effector genes and downstream pathways in PC can help pinpoint potential miRNAs for use in treatment. Different miRNA expression profiles may serve as diagnostic, prognostic markers, and therapeutic targets across the spectrum of malignant pancreatic illness. Dysregulation of miRNAs has been linked to the malignant pathophysiology of PC through affecting many cellular functions such as increasing invasive and proliferative prospect, supporting angiogenesis, cell cycle aberrance, apoptosis elusion, metastasis promotion, and low sensitivity to particular treatments. Accordingly, in the current review, we summarize the recent advances in the roles of oncogenic and tumor suppressor (TS) miRNAs in PC and discuss their potential as worthy diagnostic and prognostic biomarkers for PC, as well as their significance in PC pathogenesis and anticancer drug resistance.

MicroRNA mediated therapeutic effects of natural agents in prostate cancer

BACKGROUND

Several natural products, extensively studied for their anticancer activities, have been found to play an efficient role in preventing prostate cancer (PCa). Recently many natural agents have been reported to modulate microRNAs (miRNAs), that are involved in cancer cell growth. The microRNAs are endogenous small noncoding ribonucleic acid molecules that regulate various biological processes through an elegant mechanism of post-transcriptional control of gene expression. Besides being involved in cancer initiation, progression, angiogenesis, inflammation, they have been reported to be responsible for chemoresistance, and radioresistance of tumors. The dysregulated miRNA expression has been associated with many cancers including PCa. Over the past several years, it has been found that natural agents are good regulators of miRNAs and have a role in PCa also. Understanding the molecular mechanisms involving miRNAs by natural agents could result in developing useful strategies to combat this deadly disease.

METHODS

In order to collect research articles, the PubMed search engine was used with keywords 'prostate cancer' and 'natural agents' and 2007 papers were retrieved, further refinement with keywords 'phytochemical' and 'prostate cancer' showed 503 papers. Data was collected from research articles, published from 2010 to 2021. From these, research articles showing miRNA-mediated mechanisms were selected.

RESULTS

In this review, we have summarized the information available on the modulation of miRNAs by natural agents, their derivatives, and various combinatorial strategies with chemo/radiation therapy for the mitigation of PCa.

CONCLUSIONS

Based on the current review of literature, it has been found that the use of natural agents is a novel approach for altering miRNA expression strongly associated with PCa development, recurrence and resistance.

Regulation of miRNAs by agents targeting the tumor stem cell markers DCLK1, MSI1, LGR5, and BMI1

Gastrointestinal cancers such as colorectal, pancreatic, liver, gastric, and esophageal, are the most common forms of malignant cancers. MicroRNAs (miRNA) play important role in regulating gastrointestinal cancer progress either as potent oncogenes or tumor suppressors. In this report, we will discuss the importance of several tumor suppressors involved in colon or pancreatic cancer. Some recent studies on tumor stem cells and regulation of these miRNAs via agents targeting the tumor stem cell markers doublecortin-like kinase 1 (DCLK1), Musashi-1 (MSI1), polycomb protein BMI1, and WNT genes (LGR5 and ASCL2) will also be discussed. Agents such as siRNA/shRNA, small molecule kinase inhibitors, and general herbal drugs (curcumin) targeting these tumor stem cell markers and tumor suppressor miRNAs could be the perfect therapeutic agents for the treatment of these cancers.

miRNA-Based Therapeutic Strategies

Micro-RNAs (miRNAs) are short non-coding RNA species, thought to act primarily through downregulation of target mRNA species with subsequent decrease in encoded proteins. Recent studies revealed that miRNAs play pivotal roles in physiology and disease, and therapeutic targeting has started being investigated. Generally, the up-regulation of miRNAs is achieved through administration of synthetic miRNAs or administration of miRNA expressing vectors. The down-regulation of miRNAs is achieved through administration of anti-sense nucleotides, often chemically modified to ensure stability and specificity. There are multiple potential limitations associated with the development and testing of miRNAs-based therapeutics. These issues include, but are not limited to, off-target effect, avoidance from internal nucleases, and toxicity for miRNA therapy. In this review, we will discuss recent advances in miRNA based therapeutic strategies.

MicroRNAs, stem cells and cancer stem cells

This review discusses the various regulatory characteristics of microRNAs that are capable of generating widespread changes in gene expression via post translational repression of many mRNA targets and control self-renewal, differentiation and division of cells. It controls the stem cell functions by controlling a wide range of pathological and physiological processes, including development, differentiation, cellular proliferation, programmed cell death, oncogenesis and metastasis. Through either mRNA cleavage or translational repression, miRNAs alter the expression of their cognate target genes; thereby modulating cellular pathways that affect the normal functions of stem cells, turning them into cancer stem cells, a likely cause of relapse in cancer patients. This present review further emphasizes the recent discoveries on the functional analysis of miRNAs in cancer metastasis and implications on miRNA based therapy using miRNA replacement or anti-miRNA technologies in specific cancer stem cells that are required to establish their efficacy in controlling tumorigenic potential and safe therapeutics.