To further study the role of Oct-4 in tumor malignancy of LC-CD133 + in vitro, the migration/invasive and soft agar colony assay were used. The results showed that the abilities of the in vitro migratory invasion and colony formation in LC-CD133 + treated by Oct-4 siRNA were significantly decreased compared with nontreated LC-CD133 + , or LC-CD133 + treated with scramble-siRNA (control; p,0.001; Fig. 6A ). Furthermore, the treatment effect of chemoradiotherapy for the LC-CD133 + group can be significantly improved by the treatment of Oct-4 siRNA compared with nontreated LC-CD133 + or LC-CD133 + treated by scramble-siRNA ( Fig. 6B; p,0.001 ). In addition, we found that the apoptotic activities of annexin V (Fig. 6C) and caspase 3 (Fig. 6D; upper part) were quickly and effectively induced in LC-CD133 + treated by Oct-4 siRNA after 72 hours. In accordance with the result of cell survival and treatment effects in Oct-4 siRNA-treated LC-CD133 + (Fig. 6B) , the western blot data further demonstrated that the amounts of activated (cleaved) form of PARP were consistently elevated in LC-CD133 + treated by Oct-4 siRNA with IR alone or combined with chemotherapy ( Fig. 6D; lower part) . Thus, knockdown of Oct-4 expression in LC-CD133 + can effectively enhance chemoradiosensitivities and apoptotic activities in response to IR and chemotherapy, suggesting that Oct-4 could be a key factor enables LC-CD133 + to resist radiochemotherapeutic stress.