MicroRNAs (miRNAs) are small non-coding RNA molecules, approximately 22 nucleotides in length that regulate gene translation through silencing or degradation of target mRNAs. They are involved in multiple biological processes, including differentiation and proliferation, metabolism, hemostasis, apoptosis or inflammation, and in pathophysiology of many diseases. Numerous studies have suggested circulating miRNAs as promising diagnostic and prognostic biomarkers of many diseases.
Let-7b has been found to act as a tumor suppressor, in order to halt cell proliferation, adhesion, and invasion by targeting the genes of PKA1, DIAPH2, RDX, Ras, c-myc, and HMGA2 proteins. Let-7b expression is differently regulated in breast cancer and the data reveal its possible role in DNA repair capacity during breast carcinogenesis. Similarly, miR-let-7b was shown to be significantly downregulated in osteosarcoma tissues and cell lines and the functional studies revealed that the antitumor effect of miR-let-7b was probably due to targeting and suppressing IGF1R expression.
Let-7b has differential expression patterns also in inflamed tissues compared with healthy controls. The data demonstrate that overexpression of miR-let-7b caused a marked decrease in the expression of the proinflammatory genes, whereas blocking of miR-let-7b caused a reciprocal increase in cytokine expression. Circulating miR-let-7b-5p together with miR-125b-5p function as regulators of the inflammatory response in endometriosis. It was published that up-regulation of miR-let-7b was characteristic of prostatic tumor-associated macrophages and might play a vital role in regulating macrophage polarization, thus modulating the prognosis of prostate cancer. Furthermore, results suggest that miR-let-7b contributes to the epithelial immune responses against H. pylori infection. It has also been shown that miR-let-7b may protect human mesenchymal stem cells implanted into infarcted myocardium from apoptosis and autophagy.
Moreover, miR-let-7b has been linked to neurodegeneration; elevated amounts of miR-let-7b were found in the cerebrospinal fluid of patients with Alzheimer’s disease. In addition, miR-let-7b might be a promising blood-derived miRNA biomarker in multiple sclerosis.
- References to miR-let-7b-5p