miR-202 Diminishes TGFβ Receptors and Attenuates TGFβ1-Induced EMT in Pancreatic Cancer.

Previous studies in our laboratory identified that 3-deazaneplanocin A (DZNep), a carbocyclic adenosine analog and histone methyl transferase inhibitor, suppresses TGFβ-induced epithelial-to-mesenchymal (EMT) characteristics. In addition, DZNep epigenetically reprograms miRNAs to regulate endogenous TGFβ1 levels via miR-663/4787-mediated RNA interference (Mol Cancer Res. 2016 Sep 13. pii: molcanres.0083.2016) (1). Although DZNep also attenuates exogenous TGFβ-induced EMT response, the mechanism of this inhibition was unclear. Here, DZNep induced miR-202-5p to target both TGFβ receptors, TGFBR1 and TGFBR2, for RNA interference and thereby contributes to the suppression of exogenous TGFβ-induced EMT in pancreatic cancer cells. Lentiviral overexpression of miR-202 significantly reduced the protein levels of both TGFβ receptors and suppressed TGFβ signaling and EMT phenotypic characteristics of cultured parenchymal pancreatic cancer cells. Consistently, transfection of anti-miRNAs against miR-202-5p resulted in increased TGFBR1 and TGFBR2 protein expressions and induced EMT characteristics in these cells. In stellate pancreatic cells, miR-202 overexpression slowed growth as well as reduced stromal extracellular membrane matrix protein expression. In orthotopic pancreatic cancer mouse models, both immunodeficient and immunocompetent, miR-202 reduced tumor burden and metastasis. Together, these findings demonstrate an alternative mechanism of DZNep in suppressing TGFβ signaling at the receptor level and uncover the EMT-suppressing role of miR-202 in pancreatic cancer. These findings support the possibility of combining small molecule-based (e.g., DZNep analogs) or large molecule-based (e.g., miRNAs) epigenetic modifiers with conventional nucleoside analogs (e.g., gemcitabine, capecitabine) to improve the antimetastatic potential of current pancreatic cancer therapy. .