MicroRNA-21 induces resistance to 5-fluorouracil by down-regulating human DNA MutS homolog 2 (hMSH2).

The overexpression of microRNA-21 (miR-21) is linked to a number of human tumors including colorectal cancer, where it appears to regulate the expression of tumor suppressor genes including p21, phosphatase and tensin homolog, TGFβ receptor II, and B-cell leukemia/lymphoma 2 -associated X protein. Here we demonstrate that miR-21 targets and down-regulates the core mismatch repair (MMR) recognition protein complex, human mutS homolog 2 (hMSH2) and 6 (hMSH6). Colorectal tumors that express a high level of miR-21 display reduced hMSH2 protein expression. Cells that overproduce miR-21 exhibit significantly reduced 5-fluorouracil (5-FU)-induced G2/M damage arrest and apoptosis that is characteristic of defects in the core MMR component. Moreover, xenograft studies demonstrate that miR-21 overexpression dramatically reduces the therapeutic efficacy of 5-FU. These studies suggest that the down-regulation of the MMR mutator gene associated with miR-21 overexpression may be an important clinical indicator of therapeutic efficacy in colorectal cancer.

Alder H, Amadori D, Braconi C, Croce CM, Fabbri M, Fishel R, Gasparini P, Lovat F, Nuovo GJ, Paone A, Patel T, Sumani KM, Valeri N


Proc. Natl. Acad. Sci. U.S.A., 2010, 107 (49)

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