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 (miRs) to regulate endogenous TGFbeta1 levels via miR-663/4787 mediated RNA interference (Mol Cancer Res. 2016 Sep 13. pii: molcanres.0083.2016) (1). While DZNep also attenuates exogenous TGFbeta-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 contribute to the suppression of exogenous TGFbeta-induced EMT in pancreatic cancer cells. Lentiviral overexpression of miR-202 significantly reduced the protein levels of both TGFbeta receptors and suppressed TGFbeta signaling and EMT phenotypic characteristics of cultured parenchymal pancreatic cancer cells. Consistently, transfection of anti-miRs 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 (ECM) 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. Implications: These findings support the possibility of combining small molecule- (e.g., DZNep analogs) or large molecule- (e.g., miRs) based epigenetic modifiers with conventional nucleoside analogs (e.g., gemcitabine, capecitabine) to improve the anti-metastatic potential of current pancreatic cancer therapy.
- Received September 23, 2016.
- Revision received March 27, 2017.
- Accepted March 29, 2017.
- Copyright ©2017, American Association for Cancer Research.