Growth suppression activity of tensin2 in human hepatocellular carcinoma is dependent on PTEN and SH2 domains

Abstract

BACKGROUND: Tensin is a group of focal adhesion proteins that serves as a link between cytoskeleton and signal transduction. Dysregulation of tensin members have been revealed in various human cancers, including hepatocellular carcinoma (HCC). Our previous study has shown that tensin2 exerted pronounced cell death in HCC cells and was downregulated in 41% of human HCCs. In this study, we functionally characterized the role of tensin2 in HCC. MATERIALS AND METHODS: Functional characterization of tensin2 was studied by stable overexpression or knockdown of tensin2 in HCC cells with lentiviral delivery system. The proliferation rate, migration and invasion ability of the stable clones were monitored by growth curve, transwell assay and matrigel invasion assay, respectively. The in vivo effect of tensin2 in HCC tumour formation was studied in nude mice. Tensin2 knockdown stable clones were subcutaneously injected into nude mice and tumour growth was monitored for 4 weeks. Tensin2 deletion mutants were expressed in HCC cells and their apoptotic inducing activities were analyzed by flow cytometry and TUNEL assay. RESULTS: Tensin2 overexpression stable clones displayed lower proliferation rate, decreased anchorage-independent growth, inhibited motility and invasiveness when compared with the vector control. Conversely, stable knockdown clones of tensin2 showed higher proliferation rate, increased motility and invasiveness. Enhanced tumour formation in nude mice was also observed in stable knockdown clones. Transient expression of tensin2 induced significant suppression in colony formation of HCC cells. However, the suppression effect was lost in tensin2 mutants with either PTEN or SH2 domain deleted. TUNEL assay revealed that the number of apoptotic cells was inversely correlated with the number of HCC colonies formed. CONCLUSIONS: Our study showed that tensin2 plays a negative regulatory role in HCC development and revealed the biological significance of the PTEN and SH2 domains in the growth suppression activity of tensin2.