MicroRNA 99a (miR-99a)

MicroRNA 99a (miR-99a) is a small, evolutionary conserved, non-coding RNA molecule encoded on chromosome 21q21.1 within intron 13 of the C21orf34 gene. It functions as a post-transcriptional regulator by binding to the 3′ untranslated regions of multiple target mRNAs, promoting their degradation or inhibiting translation. miR-99a is significantly downregulated in many human cancers, acting as a tumor suppressor by inhibiting the expression of various oncogenic and cell growth-related genes such as mTOR, FGFR3, and IGF-1R. In experimental models, restoring miR-99a leads to reduced cell proliferation, induction of apoptosis, cell cycle arrest, and decreased migration and invasion. Its low expression is associated with poor prognosis, making it a promising candidate biomarker and a potential therapeutic target in cancer treatment. No approved drugs target miR-99a directly, but research is ongoing into miRNA mimics and gene therapy approaches. Safety concerns focus on specificity, potential for broad gene regulation, and delivery toxicity.

Other names

hsa-mir-99aMIRN99Amir-99aMIR99AmiR-99a-5p

Restoration of miR-99a levels via mimics or gene therapy re-establishes its tumor suppressor function through RNA interference. This leads to post-transcriptional inhibition and degradation or translational repression of target oncogenes such as mammalian target of rapamycin (mTOR), fibroblast growth factor receptor 3 (FGFR3), IGF-1R, AKT1, HOXA1, NOX4, and TNFAIP8. This ultimately results in reduced cell proliferation, induction of apoptosis, cell cycle arrest, and decreased migration and invasion.