Interaction of microRNA-21/145 and Smad3 domain-specific phosphorylation in hepatocellular carcinoma

// Ji Yu Wang 1, * , Meng Fang 1, * , Alex Boye 1, * , Chao Wu 1 , Jia Jun Wu 1 , Ying Ma 1 , Shu Hou 1 , Yue Kan 1 and Yan Yang 1 1 Department of Pharmacology and Institute of Natural Medicine, Anhui Medical University, Hefei 230032, China * These authors have contributed equally to this work Correspondence to: Yan Yang, email: yangyan@ahmu.edu.cn Keywords: hepatocellular carcinoma, microRNA-21, microRNA-145, pSmad3C, pSmad3L Received: November 10, 2016     Accepted: April 02, 2017     Published: May 09, 2017 ABSTRACT MicroRNAs 21 and 145 exhibit inverse expression in Hepatocellular carcinoma (HCC), but how they relate to Smad3 C-terminal and Link region phosphorylation (pSmad3C and pSmad3L) downstream of TGF-β/MAPK signaling, remains inconclusive. Our results suggest microRNA-145 targets Smad3 in HepG2 cells. Decreased tumor volume and increased apoptosis were produced in both microRNA-21 antagomir and microRNA-145 agomir groups compared to controls. Inhibition of TβRI and MAPK (ERK, JNK, and p38) activation respectively produced decreased microRNA-21 but increased microRNA-145 expression. Correspondingly, the expression level of pSmad3C obviously increased while pSmad3L decreased in microRNA-145 agomir-group and the expression of pSmad3C/3L were not markedly changed but pERK, pJNK, pp38 decreased in microRNA-21 antagomir-group compared to controls. On the other hand, microRNA-145 and 21 increased respectively in xenografts of HepG2 cells transfected with Smad3 EPSM and 3S-A plasmid, and this correlated with the overexpression of pSmad3C and pSmad3L respectively compared to control. To conclude, microRNA-21 promotes tumor progression in a MAPK-dependent manner while microRNA-145 suppresses it via domain-specific phosphorylation of Smad3 in HCC. Meanwhile, increased pSmad3C/3L lead to the up-regulation of microRNA-145/21 respectively. The interaction between pSmad3C/3L and microRNA-145/21 regulates HCC progression and the switch of pSmad3C/3L may serve as an important target for HCC therapy.