Incomplete radiofrequency ablation promotes the development of CD133 cancer stem cells in hepatocellular carcinoma cell line HepG2 via inducing SOX9 expression.

Background: Cancer stem cells (CSCs) accelerate the growth of hepatocellular carcinoma (HCC) residual after incomplete radiofrequency ablation (In-RFA). The present study aimed to detect the effects of In-RFA on stemness transcription factors (STFs) expression which are important for the production and function of CSCs, and to find which STFs promote HCC stemness after In-RFA.

Methods: HepG2 cells were used for in vitro and in vivo studies. Flow cytometry and sphere-formation assays were used to detect the level and function of CD133CSCs in the models. PCR array and ELISA were applied to analyze the altered expression of 84 STFs in CD133CSCs in two models. Specific lentiviral shRNA was used to knockdown STFs expression, followed by detecting In-RFA's effects on the levels and function of CD133CSCs.

Results: In-RFA was identified to induce CD133CSCs and increase their tumorigenesis ability in vitro and in vivo. The mRNA levels of 84 STFs in CD133CSCs were detected by PCR array, showing that 15 and 22 STFs were up-regulated in two models, respectively. Meanwhile, the mRNA levels of seven common STFs were up-regulated in both models. ELISA assay demonstrated that only the protein of sex determining region Y-box 9 (SOX9) was up-regulated in both models, the protein levels of the other 6 common STFs did not increase in both models. Finally, SOX9 was identified to play an important role in inducing, maintaining stemness and promoting tumorigenesis ability of CD133CSCs in both models.

Conclusion: In-RFA-induced SOX9 stimulates CD133CSCs proliferation and increases their tumorigenesis ability, suggesting that SOX9 may be a good target for HCC treatment.