IL-6 up-regulates the expression of IL-6R through JAK2/STAT3 signaling pathway to promote HCC progression

Abstract

Background The progression of hepatocellular carcinoma (HCC) involves multi-factor, multi-step interactions. It has been reported that the high expression of interleukin-6 receptor (IL-6R) plays an important role in the occurrence and development of tumors, but the regulation mechamismof IL-6R expression and its function in HCC have not been adequately reported. Methods Western Blot was used to evaluate the phosphorylation of key kinases in JAK2/STAT3 pathway and the protein expression levels of related proliferative molecules, migration molecules and apoptotic molecules. The anti-apoptosis, migration and proliferation abilities of cells of each group were analyzed using JC-1 measures cell apoptosis, EdU method to detect cell apoptosis, clone formation experiment and Transwell. Result The expression of IL-6R in HCC cells (HepG2, Huh7 and SK-Hep1) was higher than that in normal hepatocytes (THLE-2 and THLE-5), and the protein expression of IL-6R was relatively highest in SK-Hep1 and relatively lowest in HepG2. Compared with the HepG2IL − 6 cell line, the protein levels of apoptotic molecules c-Caspase7 and c-Caspase3 were lower, while the protein levels of proliferative molecules p-P70S6K and migration molecules MMP9 and MMP2 were higher, showing stronger anti-apoptosis, proliferation and migration abilities. Compared with SK-Hep1 in SK-Hep1TCZ and SK-Hep1IL − 6R−, the protein levels of apoptotic molecules c-Caspase7 and c-Caspase3 were higher, while the protein levels of proliferative molecules p-P70S6K and migration molecules MMP9 and MMP2 were lower. It showed strong apoptotic ability and low proliferation and migration ability. Interestingly, IL-6 up-regulated the expression of IL-6R by activating JAK2/STAT3 signaling pathway. The expression of IL-6R protein was also down-regulated after lentivirus knockdown of STAT3. In subcutaneous tumor-bearing experiments in nude mice, compared with SK-Hep1 group, the up-regulation of IL-6R expression after JAK2/STAT3 signaling pathway activation by IL-6 in SK-Hep1IL − 6 group significantly improved the tumor growth ability. However, the expression of IL-6R protein was down-regulated and the terminal tumor volume was significantly down-regulated in the lentiviral STAT3 knockdown group, which inhibited the tumor growth ability. Conclusions The results showed that IL-6 regulated the transcription of IL-6R through the activation of JAK2/STAT3 signaling pathway, thereby promoting the progression of HCC. The result are expected to provide experimental basis for IL-6R as a potential therapeutic target for HCC.