146713

RBFOX3

The RNA-binding protein Rbfox3 is a well-known splicing regulator that is used as a marker for post-mitotic neurons in various vertebrate species. Although recent studies indicate a variable expression of Rbfox3 in non-neuronal tissues, including lung tissue, its cellular function in lung cancer remains largely unknown. Here, we report that the number of RBFOX3-positive cells in tumorous lung tissue is lower than that in normal lung tissue. As the transforming growth factor-beta (TGF-beta) signaling pathway is important in cancer progression, we investigated its role in RBFOX3 expression in A549 lung adenocarcinoma cells. TGF-beta1 treatment inhibited RBFOX3 expression at the transcriptional level. Further, RBFOX3 depletion led to a change in the expression levels of a subset of proteins related to epithelial-mesenchymal transition (EMT), such as E-cadherin and Claudin-1, during TGF-beta1-induced EMT. In immunofluorescence microscopic analysis, mesenchymal morphology was more prominent in RBFOX3-depleted cells than in control cells. These findings show that TGF-beta-induced RBFOX3 inhibition plays an important role in EMT and propose a novel role for RBFOX3 in cancer progression.

BACKGROUND/AIMS: RBFOX3, an RNA-binding fox protein, plays an important role in the differentiation of neuronal development, but its role in the chemosensitivity of hepatocellular carcinoma (HCC) to 5-FU is unknown. METHODS: In this study, we examined the biological functions of RBFOX3 and its effect on the chemosensitivity of HCC cells to 5-FU in vitro and in a mouse xenograft model. RESULTS: RBFOX3 was found to have elevated expression in HCC cell lines and tissue samples, and its knockdown inhibited HCC cell proliferation. Moreover, knockdown of RBFOX3 improved the inhibitory effect of 5-fluorouracil (5-FU) on cell proliferation, migration and invasion, and enhanced the apoptosis induced by 5-FU. However, overexpression of RBFOX3 reduced the inhibitory effect of 5-fluorouracil (5-FU) on cell proliferation, migration and invasion, and decreased the apoptosis induced by 5-FU. We further elucidated that RBFOX3 knockdown synergized with 5-FU to inhibit the growth and invasion of HCC cells through PI3K/AKT and epithelial-mesenchymal transition (EMT) signaling, and promote apoptosis by activating the cytochrome-c/caspase signaling pathway. Finally, we validated that RBFOX3 regulated 5-FU-mediated cytotoxicity in HCC in mouse xenograft models. CONCLUSIONS: The findings from this study indicate that RBFOX3 regulates the chemosensitivity of HCC to 5-FU in vitro and in vivo. Therefore, targeting RBFOX3 may improve the inhibition of HCC growth and progression by 5-FU, and provide a novel potential therapeutic strategy for HCC.CI - (c) 2018 The Author(s). Published by S. Karger AG, Basel.