Anti-tumor effect of human endostatin mediated by retroviral gene transfer in nude mice

Objective To explore the inhibitory effect of human endostatin gene mediated by retroviral vector on the growth of human liver carcinoma. Methods A recombinant retroviral plasmid containing human endostatin gene and signal peptide was engineered and transferred into PA317 cells to produce retrovirus. Human liver carcinoma cells (SMMC7721) were infected with the above retrovirus to build a stable endostatin-transfected liver carcinoma cell line (SMMC-endo). The control liver carcinoma cell line (SMMC-pLncx) was developed in a similar way except that the plasmid was replaced by an empty retroviral vector. Immunohistochemistry and Western blot were used to test the expression and secretion of human endostatin. The biological activity of the expressed human endostatin was assessed by endothelial cell proliferation assay. The growth rates of SMMC-endo and control SMMC-pLncx cells in vivo and in vitro were also observed.Results The expression and secretion of human endostatin by endostatin-transfected SMMC-endo cells were confirmed by immunohistochemistry and Western blot. Compared with the control group, concentrated supernatant of SMMC-endo cells remarkably inhibited the proliferation of human umbilical vein endothelial cells by 48%, significantly higher than the inhibition by the control (10.2%; P<0.01). The endostatin-transfected SMMC-endo cells had similar in vitro growth rates to SMMC-pLncx cells. The in vivo experiment showed that the growth rate of SMMC-endo cells was slowed. Only in 3 out of 5 mice were tumors formed and flank tumors of SMMC-endo cells were 94.5% smaller than those of control cells 22 days after inoculation into nude mice (P<0.001). Conclusions Gene transfer of human endostatin mediated by retroviral vector is an effective form of cancer therapy.