Sorafenib sensitizes hepatocellular carcinoma cells to physiological apoptotic stimuli

Abstract

Sorafenib increases survival rate of patients with advanced hepatocellular carcinoma (HCC). The mechanism underlying this effect is not completely understood. In this work we have analyzed the effects of sorafenib on autocrine proliferation and survival of different human HCC cell lines. Our results indicate that Sorafenib in vitro counteracts autocrine growth of different tumor cells (Hep3B, HepG2, PLC-PRF-5, SK-Hep1). Arrest in S/G2/M cell cycle phases were observed coincident with cyclin D1 down-regulation. However, sorafenib’s main anti-tumor activity seems to occur through cell death induction which correlated with caspase activation, increase in the percentage of hypodiploid cells, activation of BAX and BAK and cytochrome c release from mitochondria to cytosol. In addition, we observed a rise in mRNA and protein levels of the pro-apoptotic “BH3-domain only” PUMA and BIM, as well as decreased protein levels of the anti-apoptotic MCL1 and survivin. PUMA targeting knockdown, by using specific siRNAs, inhibited sorafenib-induced apoptotic features. Moreover, we obtained evidence suggesting that sorafenib also sensitizes HCC cells to the apoptotic activity of Transforming Growth Factor-β (TGF-β) through the intrinsic pathway and to Tumor Necrosis Factor-α (TNF) through the extrinsic pathway. Interestingly, sensitization to sorafenib-induced apoptosis is characteristic of liver tumor cells, since untransformed hepatocytes did not respond to sorafenib inducing apoptosis, either alone or in combination with TGF-β or TNF. Indeed, sorafenib effectiveness in delaying HCC late progression might be partly related to a selectively sensitization of HCC cells to apoptosis by disrupting autocrine signals that protect them from adverse conditions and pro-apoptotic physiological cytokines.

Flavonoid-Enriched Apple Fraction AF4 Induces Cell Cycle Arrest, DNA Topoisomerase II Inhibition, and Apoptosis in Human Liver Cancer HepG2 Cells

“…Consistent with the previous studies, the cell cycle analysis suggested that the AF4 induced G2/M phase arrest in HepG2 cells (Fig. 5) signifying mitosis arrest; whereas chemotherapy drug Sorafenib showed a S/G2-M phase arrest which was consistent with previous finding (28). This confirms that the AF4-induced cell death is cell-cycle regulated.…”

Upregulation of PP2Ac predicts poor prognosis and contributes to aggressiveness in hepatocellular carcinoma

“…28 BBC3 is a proapoptotic BH3-only protein that can sensitize HCC cells to sorafenib-induced apoptosis. 29 Some tumor-promoting genes such as MYC, 30 EGFR, 31 VEGFA, 32 and NOTCH1 33 are downregulated by PP2Ac silencing. These results offer a molecular insight into the regulation of the aggressiveness of HCC by PP2Ac.…”

Epigenetic upregulation of Bak by ZBP-89 inhibits the growth of hepatocellular carcinoma

“…The reduction of Bak contributes to the development and progression of HCC [28,29]. The significance of Bak in HCC cells is further supported by several experiments in which different agents induce apoptosis in HCC cells by stimulating Bak expression [30–33]. Although the significance of Bak in HCC has been reported, the mechanism responsible for its regulation in HCC is largely unknown.…”