MicroRNAs in Cancer (An Overview)

The expression of microRNAs (miRNAs) is deregulated in human cancer, with some miRNAs consistently up- or down-regulated in more than one type of neoplasm. The demonstration that aberrantly expressed miRNAs can affect the function of known oncogenes and tumor suppressor genes established molecular links with pathways implicated in malignant transformation. Cell cycle progression, loss of differentiation, increased survival, invasion, and metastasis were shown to be all under the influence of miRNAs, thereby implicating that miRNAs can themselves act as oncogenes or tumor suppressor genes. Besides increasing our knowledge on the molecular basis of cancer, accumulating evidences indicate that miRNA expression profiling has the potential of being translated into clinical applications. Analysis of cancer tissues revealed that miRNAs could be molecular markers useful for cancer classification, prognostic stratification, and drug-response prediction. MiRNAs also emerged as circulating markers, which may become valuable for early diagnosis and follow-up investigations. If we consider that studies on miRNAs in cancer therapy have already produced important results, in just few years, miRNAs have had a great impact in all cancer areas. Whether this will translate into important clinical applications is still too early to say.