Suppression of tumorigenesis and metastasis of hepatocellular carcinoma by shRNA interference targeting on inhibition of homeoprotein Six1

Abstract

We previously demonstrated that overexpression of homeoprotein Six1 in hepatocellular carcinoma (HCC) patients is associated with venous infiltration, later pathologic tumor metastasis (pTNM) stage and poor overall survival rate (Ng et al., 2006). In this study, short hairpin RNA (shRNA) interference approach was used to suppress the expression of Six1 in a HCC cell line MHCC97L which is capable of local and distant metastases. Stable transfectant MHCC97L-shSix1carrying Six1 specific shRNA plasmid exhibited suppression of Six1 expression to about 40% of the control cell line MHCC97L. In vitro functional assays demonstrated that the growth rate and proliferation ability of MHCC97L-shSix1 were markedly suppressed comparing with the control cells. Furthermore, noticeable decrease in cell motility and invasiveness were observed in MHCC97L-shSix1. Data from in vivo xenograft tumorigenesis model demonstrated that the growth rate of subcutaneous xenograft in MHCC97L-shSix1 group was significantly reduced (P<0.01). Spontaneous metastasis models indicated that targeting Six1 suppression significantly reduced the tumor volume (P < 0.01) and the pulmonary metastasis in MHCC97L-shSix1 group (P=0.026). Our data suggested that Six1 might function involved in tumorigenesis and metastasis of HCC. Suppression of Six1 leading to the reduction of in vitro and in vivo metastatic ability of MHCC97L implied its potential therapeutic application on treatment of HCC metastasis.