Department of Medical Research, National Taiwan University Hospital, Taipei, Taiwan.
Biochem Pharmacol. 2013 Feb 1;85(3):356-66. doi: 10.1016/j.bcp.2012.11.009. Epub 2012 Nov 23.
Erlotinib is a small-molecular inhibitor of epidermal growth factor receptor (EGFR). Here, we identify that cancerous inhibitor of protein phosphatase 2A (CIP2A) is a major determinant mediating erlotinib-induced apoptosis in hepatocellular carcinoma (HCC). Erlotinib showed differential effects on apoptosis in 4 human HCC cell lines. Erlotinib induced significant apoptosis in Hep3B and PLC5 cell lines; however, Huh-7 and HA59T cell lines showed resistance to erlotinib-induced apoptosis at all tested doses. Down-regulation of CIP2A, a cellular inhibitor of protein phosphatase 2A (PP2A), mediated the apoptotic effect of erlotinib in HCC. Erlotinib inhibited CIP2A in a dose- and time-dependent manner in all sensitive HCC cells whereas no alterations in CIP2A were found in resistant cells. Overexpression of CIP2A upregulated phospho-Akt and protected Hep3B cells from erlotinib-induced apoptosis. In addition, silencing CIP2A by siRNA restored the effects of erlotinib in Huh-7 cells. Moreover, adding okadaic acid, a PP2A inhibitor, abolished the effects of erlotinib on apoptosis in Hep3B cells; and forskolin, a PP2A agonist enhanced the effect of erlotinib in resistant HA59T cells. Combining Akt inhibitor MK-2206 with erlotinib restored the sensitivity of HA59T cells to erlotinib. Furthermore, in vivo xenograft data showed that erlotinib inhibited the growth of PLC5 tumor but had no effect on Huh-7 tumor. Erlotinib downregulated CIP2A and upregulated PP2A activity in PLC5 tumors, but not in Huh-7 tumors. In conclusion, inhibition of CIP2A determines the effects of erlotinib on apoptosis in HCC. CIP2A may be useful as a therapeutic biomarker for predicting clinical response to erlotinib in HCC treatment.
厄洛替尼是一种表皮生长因子受体（EGFR）的小分子抑制剂。在这里，我们发现癌性蛋白磷酸酶 2A 抑制剂（CIP2A）是介导厄洛替尼诱导肝癌（HCC）细胞凋亡的主要决定因素。厄洛替尼对 4 个人 HCC 细胞系的凋亡有不同的影响。厄洛替尼在 Hep3B 和 PLC5 细胞系中诱导显著的凋亡；然而， Huh-7 和 HA59T 细胞系在所有测试剂量下均对厄洛替尼诱导的凋亡表现出抗性。CIP2A 的下调，即蛋白磷酸酶 2A（PP2A）的细胞抑制剂，介导了厄洛替尼在 HCC 中的凋亡作用。厄洛替尼在所有敏感 HCC 细胞中以剂量和时间依赖的方式抑制 CIP2A，而在抗性细胞中未发现 CIP2A 的改变。CIP2A 的过表达上调磷酸化 Akt 并保护 Hep3B 细胞免受厄洛替尼诱导的凋亡。此外，用 siRNA 沉默 CIP2A 恢复了厄洛替尼对 Huh-7 细胞的作用。此外，添加 PP2A 抑制剂 okadaic 酸消除了厄洛替尼对 Hep3B 细胞凋亡的影响；而 forskolin，一种 PP2A 激动剂，增强了厄洛替尼对抗性 HA59T 细胞的作用。将 Akt 抑制剂 MK-2206 与厄洛替尼联合使用恢复了 HA59T 细胞对厄洛替尼的敏感性。此外，体内异种移植数据表明，厄洛替尼抑制了 PLC5 肿瘤的生长，但对 Huh-7 肿瘤没有影响。厄洛替尼下调了 PLC5 肿瘤中的 CIP2A 并上调了 PP2A 活性，但在 Huh-7 肿瘤中没有。总之，CIP2A 的抑制决定了厄洛替尼对 HCC 细胞凋亡的影响。CIP2A 可作为预测 HCC 治疗中厄洛替尼临床反应的治疗生物标志物。
