MicroRNAs in DNA Damage Response, Carcinogenesis, and Chemoresistance.

In the classical model of tumorigenesis, cancer develops via slowly accumulating mutations that facilitate uncontrolled cell growth and allow cells to escape apoptosis. Oncogenes and tumor suppressor genes regulate the key signaling pathways involved in tumorigenesis and cancer progression. Moreover, studies indicate that MicroRNAs (MiRNAs) are also key parts of these processes. MiRNAs are short, noncoding RNAs that regulate the expression of target genes at the posttranscriptional level. By regulating the expression of numerous cytokines, MiRNAs play crucial roles in cell growth, apoptosis, and stemness maintenance. Abundant evidence demonstrates that MiRNAs can function as both oncogenes and tumor suppressors in accommodating the proliferation and invasion of cancer cells in solid tumors. Targeting these MiRNAs may significantly alter oncogenic signaling pathways and slow or halt progression of many different types of tumors. A better understanding of the functions of MiRNAs in cancer will enable the development of new treatment strategies for chemoresistant malignancies. This review discusses recent findings about the connections between MiRNAs and carcinogenesis and provides insight into the role of MiRNAs in generating chemoresistance.