TERT-mediated induction of MIR500A contributes to tumor invasiveness by targeting Hedgehog pathway

The classical activity of telomerase (TERT) is to maintain telomere homeostasis, ensuring chromosome stability and cellular proliferation. However, increasing evidences of telomere-independent human TERT functions have been lastly obtained. We report here that TERT directly binds to the TCF binding elements (TBE) located upstream the oncomiR MIR500A inducing its expression and promoting cancer invasiveness. This function is independent of telomerase activity, since catalytic inactive TERT also induces MIR500A expression and telomerase inhibitors directed against TERT, but not to its RNA component TERC, inhibit telomerase-induced MIR500A expression and cancer invasiveness. Mechanistically, telomerase-induced MIR500A down-regulates key genes of the Hedgehog signaling pathway, namely patched 1 (PTCH1), Gli family zinc finger 3 (GLI3) and cullin 3 (CUL3), increasing tumor invasiveness. Our results show a crucial role of the TERT/MIR500A/Hedgehog axis is tumor aggressiveness, pointing out to the relevance of inhibiting the extracurricular functions of telomerase to fight cancer.