Department of Neurosurgery, School of Medicne, Virginia Commonwealth University, Richmond, VA 23298-0035, USA.
Mol Pharmacol. 2012 Dec;82(6):1217-29. doi: 10.1124/mol.112.081539. Epub 2012 Sep 18.
Previous studies showed that lapatinib and obatoclax interact in a greater-than-additive fashion to cause cell death and do so through a toxic form of autophagy. The present studies sought to extend our analyses. Lapatinib and obatoclax killed multiple tumor cell types, and cells lacking phosphatase and tensin homolog (PTEN) function were relatively resistant to drug combination lethality; expression of PTEN in PTEN-null breast cancer cells restored drug sensitivity. Coadministration of lapatinib with obatoclax elicited autophagic cell death that was attributable to the actions of mitochondrial reactive oxygen species. Wild-type cells but not mitochondria-deficient rho-zero cells were radiosensitized by lapatinib and obatoclax treatment. Activation of p38 mitogen-activated protein kinase (MAPK) and c-Jun NH(2)-terminal kinase 1/2 (JNK1/2) by the drug combination was enhanced by radiation, and signaling by p38 MAPK and JNK1/2 promoted cell killing. In immunohistochemical analyses, the autophagosome protein p62 was determined to be associated with protein kinase-like endoplasmic reticulum kinase (PERK) and inositol-requiring enzyme 1, as well as with binding immunoglobulin protein/78-kDa glucose-regulated protein, in drug combination-treated cells. Knockdown of PERK suppressed drug-induced autophagy and protected tumor cells from the drug combination. Knockdown of PERK suppressed the reduction in Mcl-1 expression after drug combination exposure, and overexpression of Mcl-1 protected cells. Our data indicate that mitochondrial function plays an essential role in cell killing by lapatinib and obatoclax, as well as radiosensitization by this drug combination.
先前的研究表明，拉帕替尼和 obatoclax 以大于相加的方式相互作用，导致细胞死亡，并通过一种有毒的自噬形式发挥作用。本研究旨在扩展我们的分析。拉帕替尼和 obatoclax 杀死了多种肿瘤细胞类型，而缺乏磷酸酶和张力蛋白同系物 (PTEN) 功能的细胞对药物组合的致死性相对耐药；在 PTEN 缺失的乳腺癌细胞中表达 PTEN 恢复了药物敏感性。拉帕替尼和 obatoclax 的共同给药引起了自噬细胞死亡，这归因于线粒体活性氧的作用。野生型细胞而不是缺乏线粒体的 rho-zero 细胞被 lapatinib 和 obatoclax 处理增敏。药物组合对 p38 丝裂原活化蛋白激酶 (MAPK) 和 c-Jun NH(2)-末端激酶 1/2 (JNK1/2) 的激活作用通过辐射增强，而 p38 MAPK 和 JNK1/2 的信号转导促进了细胞杀伤。在免疫组织化学分析中，自噬体蛋白 p62 被确定与蛋白激酶样内质网激酶 (PERK) 和需要肌醇的酶 1 以及结合免疫球蛋白蛋白/78-kDa 葡萄糖调节蛋白有关，在药物组合处理的细胞中。PERK 的敲低抑制了药物诱导的自噬，并保护肿瘤细胞免受药物组合的影响。PERK 的敲低抑制了药物组合暴露后 Mcl-1 表达的减少，而过表达 Mcl-1 则保护了细胞。我们的数据表明，线粒体功能在 lapatinib 和 obatoclax 的细胞杀伤以及该药物组合的放射增敏中起着至关重要的作用。
