Overexpressed microRNA-136 works as a cancer suppressor in gallbladder cancer through suppression of JNK signaling pathway via inhibition of MAP2K4

Abstract

In recent studies, microRNAs (miRs) have been widely explored as important regulators in tumor suppression. miR-136 has been suggested to participate in tumor inhibition through control of vital cellular processes, such as angiogenesis, proliferation, and apoptosis. This study aimed to evaluate the effects of overexpressed miR-136 by transferring mimics in gallbladder cancer (GBC) and to assess the functional role of miR-136 in GBC cell behaviors with the involvement of the mitogen-activated protein kinase kinase 4 ( MAP2K4)-dependent JNK signaling pathway. Differentially expressed miRs associated with GBC were screened using microarray expression profiles, which identified that miR-136 expression was decreased in GBC. Furthermore, MAP2K4 was validated as a target gene of miR-136. To uncover functional relevance regarding miR-136 and MAP2K4 in GBC, cultured GBC cell lines were prepared to transfect with mimic, inhibitor, siRNA, or vectors. At the same time, the transfected GBC cells were inoculated into nude mice to validate findings in vivo. The obtained results demonstrated that overexpressed miR-136 inhibited angiogenesis and cell proliferation and promoted apoptosis in GBC cell lines in vitro, accompanied by impeded cellular tumorigenicity in nude mice via the suppression of MAP2K4. Moreover, the overexpression of MAP2K4 and the activation of the JNK signaling pathway reversed the inhibitory effects of miR-136 on the angiogenesis and tumorigenicity of GBC cells. Together, our results indicated that overexpressed miR-136 attenuates angiogenesis and enhances cell apoptosis in GBC via the JNK signaling pathway by downregulating the expression of MAP2K4. NEW & NOTEWORTHY This study is based on previous studies suggesting the tumor-suppressive role of microRNA (miR)-136 in various cancers. We aim to clarify whether miR-136 could function as a tumor suppressor in gallbladder cancer (GBC) and an underlying mechanism. In vitro and in vivo assays delineated that the tumor-suppressive role of miR-136 in GBC is achieved through inactivation of the JNK signaling pathway by downregulation of MAP2K4.