Combinatorial treatment with PARP and MAPK inhibitors to overcome phenotype switch-driven drug resistance in advanced melanoma. Combinatorial treatment with PARP and MAPK inhibitors to overcome phenotype switch-driven drug resistance in advanced melanoma

The prognosis for most patients with advanced malignant melanoma is traditionally very poor, as the disease is either intrinsically resistant or rapidly acquires resistance to targeted therapy treatments. Here, using a drug screen targeting chromatin regulators in patient-derived 3D melanoma cell cultures, we discovered that PARP inhibitors are capable of restoring MAPKi sensitivity. This synergy was found to be independent of DNA damage repair pathways and was effective both in vitro and in vivo in patients-derived xenografts. Strikingly, through integrated transcriptomic, proteomic and epigenomic analysis, we discovered that PARPi induces lysosomal autophagy which was accompanied by enhanced mitochondrial lipid metabolism that, ultimately, increased antigen presentation and T-cell cytotoxicity. Moreover, we also found that PARP inhibitors regulated EMT-like phenotype switching by dampening the mesenchymal phenotype via transcriptomic and epigenetic rearrangements. This, in turn, redirected melanoma cells towards a proliferative and, thus, MAPKi-sensitive state. Our study provides a scientific rational for treating patients with PARPi in combination with MAPKi to annihilate acquired therapy resistance Overall design: RNAseq of spheroids of melanoma cell lines M121224 and M111031 were treated with Talazoparib (PARPi), Encorafenib (LGX818) and combination of Talazoparib and Encorafenib .

传统上，多数晚期恶性黑色素瘤患者的预后极差——这类肿瘤要么先天对靶向治疗耐受，要么会快速获得靶向治疗耐药性。本研究通过在患者来源的3D黑色素瘤细胞培养体系中靶向染色质调控因子进行药物筛选，发现PARP抑制剂（PARP inhibitor）能够恢复肿瘤细胞对MAPK抑制剂（MAPKi）的敏感性。该协同效应不依赖于DNA损伤修复通路，且在体外实验及患者来源异种移植瘤模型中均能发挥作用。
令人惊喜的是，通过整合转录组、蛋白质组与表观基因组分析，我们发现PARP抑制剂（PARPi）可诱导溶酶体自噬，伴随线粒体脂质代谢增强，最终提升抗原呈递能力与T细胞细胞毒性。此外，我们还发现，PARP抑制剂可通过转录组与表观基因组重编程抑制间质表型，从而调控上皮间质转化（EMT）样表型转换。这一转变可将黑色素瘤细胞重定向至增殖性且对MAPKi敏感的状态。
本研究为采用PARP抑制剂联合MAPK抑制剂治疗以根除获得性治疗耐药性提供了科学依据。
实验整体设计：对黑色素瘤细胞系M121224与M111031的球体培养物分别施加他拉唑帕利（Talazoparib，PARPi）、恩考芬尼（Encorafenib，LGX818）以及二者联合处理，并对其进行RNA测序（RNAseq）。