The Role of miRNA in Papillary Thyroid Cancer in the Context of miRNA Let-7 Family

Abstract

Papillary thyroid carcinoma (PTC) is the most common endocrine malignancy. RET/PTC rearrangement is the most common genetic modification identified in this category of cancer, increasing proliferation and dedifferentiation by the activation of the RET/PTC-RAS-BRAF-MAPK-ERK signaling pathway. Recently, let-7 miRNA was found to reduce RAS levels, acting as a tumor suppressor gene. Circulating miRNA profiles of the let-7 family may be used as novel noninvasive diagnostic, prognostic, treatment and surveillance markers for PTC.

Keywords: carcinogenesis; let-7 family; miRNAs; papillary thyroid cancer.

Figure 1

MicroRNA maturation and function. RNA polymerase II synthesizes primary miRNA. Next, pri-miRNA is processed by the Drosha DGCR8 microprocessor in the nucleus. The produced pre-miRNA is transported to the cytoplasm with the participation of EXP5-Ran-GTP. In the next step, the Dicer microprocessor creates a mature miRNA from pri-miRNA by removing the loop. The mature miRNA with AGO protein forms RISC to stop the translation of a target mRNA.