Research Project 2 - Targeting Melanoma Tumor Survival and Apoptotic Machinery

项目摘要-项目2 黑色素瘤是皮肤癌中最具侵袭性的一种，其特点是体细胞突变率很高。 大约50%的皮肤黑色素瘤的突变会影响BRAF中的V600残留物。这个 突变形式的蛋白质(BRAFV600)的活性显著增加，并导致结构性激活 RAS-RAF-MAPK信号通路。这些信息已迅速转化为临床益处，如5 靶向治疗方案已被批准用于治疗转移性黑色素瘤患者 BRAFV600突变。虽然这些药物具有非常高的临床应答率，但不幸的是，大多数 患者在2年内产生耐药性。此外，这些靶向治疗不能用于以下患者 没有BRAFV600突变。因此，仍有未得到满足的临床需求来确定预防策略。 具有激活的BRAFV600突变的转移性黑色素瘤患者对已批准的靶向治疗的耐药性， 以及为没有BRAFV600突变(BRAF野生型)的患者提供新的靶向治疗方法。虽然很多人 评估其他激酶抑制剂的治疗潜力的研究正在进行中，有越来越多的证据表明 支持对针对细胞凋亡机制的药物进行测试的理由。与许多其他人不同 在癌症、皮肤黑色素瘤中，TP53基因的突变率很低(~20%)。更多的研究表明 BCL2家族蛋白的抗凋亡成员可促进对靶向治疗的抵抗力 Ras-RAF-MAPK途径，以及促凋亡蛋白(即BIM)是其有效性的关键。 基于有限数量的临床前模型的可喜结果，针对细胞凋亡的临床试验 机械联合RAS-RAF-MAPK途径抑制剂治疗转移性黑色素瘤 病人。然而，目前还没有生物标记物来优化这些策略的患者选择，也没有 了解对它们的抗性机制。这一提议的中心假设是，具体的 分子特征将预测对组合策略的敏感性和抵抗力 细胞凋亡剂和MAPK通路的靶向治疗。为了检验这一假设，我们将评估 促凋亡药物联合MAPK途径抑制剂治疗分子特征性黑色素瘤 PDX模型，它准确地复制了这种疾病的分子特征和异质性。在目标1中我们 将评估Navitoclax的疗效和分子效应，Navitoclax是一种BH3模拟物，可单独和在 联合达普拉非尼(BRAFi)和曲美替尼(Meki)治疗具有BRAFV600突变的黑色素瘤PDX。这些 实验反映了这些药物在转移性黑色素瘤患者中正在进行的随机II期试验，以及 该试验的结果将用于临床验证与PDX耐药相关的标记物。在AIM 2中 我们将评估MDM2抑制剂AMG232单独以及与曲美替尼联合使用的疗效。测试 将在带有野生型TP53的BRAF WT黑色素瘤中执行，包括带有MDM2扩增的子集。 这些研究将有助于改进和优先使用这些药物治疗转移性黑色素瘤患者的策略。

Project Summary – Project 2 Melanoma, the most aggressive form of skin cancer, is characterized by a very high rate of somatic mutations. Approximately 50% of cutaneous melanomas have a mutation that affects the V600 residue in Braf. The activity of the mutant form of the protein (BRAFV600) is markedly increased and results in constitutive activation of the RAS-RAF-MAPK signaling pathway. This information has rapidly translated into clinical benefit, as five targeted therapy regimens have been approved for the treatment of metastatic melanoma patients with a BrafV600 mutation. While these agents have very high clinical response rates, unfortunately the majority of patients develop resistance within 2 years. Further, these targeted therapies cannot be used in patients who do not have a BrafV600 mutation. Thus, there remain unmet clinical needs to identify strategies to prevent resistance to approved targeted therapies in metastatic melanoma patients with an activating BrafV600 mutation, and new targeted therapy approaches for patients without a BrafV600 mutation (BRAF Wild-Type). While many studies are ongoing to evaluate the therapeutic potential of other kinase inhibitors, there is growing evidence to support the rationale for the testing of agents that target the apoptotic machinery. In contrast to many other cancers, cutaneous melanomas have a low rate (~20%) of mutations in Tp53. Additional studies have shown anti-apoptotic members of the BCL2 family of proteins can promote resistance to targeted therapies against the RAS-RAF-MAPK pathway, and that pro-apoptotic proteins (i.e., BIM) are critical to their effectiveness. Based on promising results in a limited number of preclinical models, clinical trials targeting the apoptotic machinery in combination with RAS-RAF-MAPK pathway inhibitors are ongoing in metastatic melanoma patients. However, currently there are no biomarkers to optimize patient selection for these strategies, nor understanding of resistance mechanisms to them. The central hypothesis of this proposal is that specific molecular features will predict sensitivity and resistance to combinatorial strategies utilizing pro- apoptotic agents and MAPK pathway targeted therapies. In order to test this hypothesis we will evaluate pro-apoptotic agents in combination with MAPK pathway inhibitors in molecularly characterized melanoma PDX models, which accurately replicate the molecular features and heterogeneity of this disease. In AIM 1 we will evaluate the efficacy and molecular effects of navitoclax, a BH3 mimetic that inhibits BCL2, alone and in combination with dabrafenib (BRAFi) and trametinib (MEKi) in melanoma PDX with a BrafV600 mutation. These experiments mirror an ongoing randomized phase II of these agents in metastatic melanoma patients, and the results of that trial will be used to clinically validate markers associated with resistance in the PDX. In AIM 2 we will evaluate the efficacy of the MDM2 inhibitor AMG232, alone and in combination with trametinib. Testing will be performed in BRAF WT melanomas with wild-type Tp53, including a subset with MDM2 amplification. These studies will help to refine and prioritize strategies using these agents in metastatic melanoma patients.