Martin S, Dudek-Perić A M, Maes H, Garg A D, Gabrysiak M, Demirsoy S, Swinnen J V, Agostinis P
Cell Death Research and Therapy Unit, Department for Cellular and Molecular Medicine, University of Leuven (KU Leuven), Campus Gasthuisberg, O&N1, Herestraat 49, Box 802, 3000 Leuven, Belgium.
Laboratory of Lipid Metabolism and Cancer, Department of Oncology, University of Leuven (KU Leuven), Campus Gasthuisberg, O&N1, Herestraat 49, Box 818, 3000 Leuven, Belgium.
Biochem Pharmacol. 2015 Feb 1;93(3):290-304. doi: 10.1016/j.bcp.2014.12.003. Epub 2014 Dec 18.
Vemurafenib (PLX4032), an inhibitor of BRAF(V600E), has demonstrated significant clinical anti-melanoma effects. However, the majority of treated patients develop resistance, due to a variety of molecular mechanisms including MAPK reactivation through MEK. The induction of a cancer cell death modality associated with danger-signalling resulting in surface mobilization of crucial damage-associated-molecular-patterns (DAMPs), e.g. calreticulin (CRT) and heat shock protein-90 (HSP90), from dying cells, is emerging to be crucial for therapeutic success. Both cell death and danger-signalling are modulated by autophagy, a key adaptation mechanism stimulated during melanoma progression. However, whether melanoma cell death induced by MAPK inhibition is associated with danger-signalling, and the reliance of these mechanisms on autophagy, has not yet been scrutinized. Using a panel of isogenic PLX4032-sensitive and resistant melanoma cell lines we show that PLX4032-induced caspase-dependent cell death and DAMPs exposure in the drug-sensitive cells, but failed to do so in the drug-resistant cells, displaying heightened MEK activation. MEK inhibitor, U0126, treatment sensitized PLX4032-resistant cells to death and re-established their danger-signalling capacity. Only melanoma cells exposing death-induced danger-signals were phagocytosed and induced DC maturation. Although the PLX4032-resistant melanoma cells displayed higher basal and drug-induced autophagy, compromising autophagy, pharmacologically or by ATG5 knockdown, was insufficient to re-establish their PLX4032 sensitivity. Interestingly, autophagy abrogation was particularly efficacious in boosting cell death and ecto-CRT/ecto-HSP90 in PLX4032-resistant cells upon blockage of MEK hyper-activation by U0126. Thus combination of MEK inhibitors with autophagy blockers may represent a novel treatment regime to increase both cell death and danger-signalling in Vemurafenib-resistant metastatic melanoma.
维莫非尼（PLX4032）是一种BRAF（V600E）抑制剂，已显示出显著的临床抗黑色素瘤效果。然而，大多数接受治疗的患者会产生耐药性，这是由于多种分子机制，包括通过MEK使MAPK重新激活。诱导与危险信号相关的癌细胞死亡方式，从而导致关键的损伤相关分子模式（DAMPs），如钙网蛋白（CRT）和热休克蛋白90（HSP90）从垂死细胞表面动员起来，对于治疗成功至关重要。细胞死亡和危险信号均受自噬调节，自噬是黑色素瘤进展过程中被刺激的一种关键适应机制。然而，MAPK抑制诱导的黑色素瘤细胞死亡是否与危险信号相关，以及这些机制对自噬的依赖性，尚未得到仔细研究。使用一组同基因的PLX4032敏感和耐药黑色素瘤细胞系，我们发现PLX4032在药物敏感细胞中诱导了半胱天冬酶依赖性细胞死亡和DAMPs暴露，但在耐药细胞中未能如此，耐药细胞显示出增强的MEK激活。MEK抑制剂U0126处理使PLX4032耐药细胞对死亡敏感，并重新建立了它们的危险信号能力。只有暴露死亡诱导危险信号的黑色素瘤细胞被吞噬并诱导DC成熟。虽然PLX4032耐药黑色素瘤细胞表现出更高的基础和药物诱导的自噬，但通过药理学方法或敲低ATG5来损害自噬，不足以重新建立它们对PLX4032的敏感性。有趣的是，在通过U0126阻断MEK过度激活后，自噬废除在增强PLX4032耐药细胞的细胞死亡和细胞外CRT/细胞外HSP90方面特别有效。因此，MEK抑制剂与自噬阻滞剂的联合可能代表一种新的治疗方案，以增加维莫非尼耐药转移性黑色素瘤中的细胞死亡和危险信号。
