Melanoma Resistance to Apoptosis: Mechanisms and Therapeutic Potential

恶性黑色素瘤的一个基本特征是对细胞凋亡的抵抗，这在很大程度上决定了 黑色素瘤的抗药性促凋亡和抗凋亡分子的复杂相互作用， Bcl-2家族是细胞凋亡的中心控制点，是一个很有前途的药物靶点。BH 3模拟物ABT-737是一种 抗凋亡蛋白Bcl-2/Bcl-XL/Bcl-w的有效小分子抑制剂，并且它显示出用于 作为单一药剂或组合疗法的癌症治疗。 我们已经发现，单独的ABT-737在黑素瘤细胞中诱导的细胞毒性很小，并且敲除实验 利用RNAi技术证实抗凋亡蛋白Mcl-1而不是Bcl-2或Bcl-XL是主要的 黑色素瘤对ABT-737治疗耐药性的介导物。此外，ABT-737还表现出较强的协同增效作用， 与蛋白酶体抑制剂（MG-132或硼替佐米）或紫杉醇联合使用时的致死率，以及 机制研究表明，蛋白酶体抑制剂和Paclitaxel中和Mcl-1的功能。 这些令人兴奋的结果表明，中和Mcl-1功能的药物是治疗糖尿病的杰出候选者。 与ABT-737联合治疗黑色素瘤，并在临床前模型中进行验证 并进一步探索靶向Mcl-1的其他药物与ABT-737组合的治疗潜力。 也有人提出，优选引发癌症的癌症引发细胞（或癌症干细胞）， 可能是癌症对治疗产生耐药性的原因，消除这些细胞可能是治疗癌症的关键。 开发任何癌症治疗方法并取得长期成功。我们将这些细胞称为癌模仿细胞。我们 建议研究富集的黑色素瘤起始细胞是否对现有的 化疗剂比非分选细胞在黑色素瘤，并检查是否组合 减少多种抗凋亡防御的药物，如ABT-737加硼替佐米或紫杉醇， 克服黑色素瘤起始细胞的这种抗性。这些研究将是一个重要组成部分， 了解黑色素瘤起始细胞是否对治疗更具抵抗力。 具体目的1：直接测试富集的黑色素瘤起始细胞对现有和 体外新疗法i）为了确定富集的黑色素瘤起始细胞是否更耐 常规化疗剂如替莫唑胺。ii）为了确定ABT-2000的组合是否是ABT-2000的组合。 737与硼替佐米或紫杉醇的组合克服了富集的黑素瘤起始细胞中的抗性。 具体目的2：验证ABT-737与硼替佐米或硼替佐米的组合的功效。 紫杉醇治疗黑色素瘤的两种新的异种移植模型：一种靶向人的模型 体内黑素瘤起始细胞，以及黑素瘤患者样品的直接异种移植物模型。 具体目的3：研究BH 3模拟物ABT-737与其他药物联合治疗的可能性。 抑制Mcl-1的化合物。i）通过microRNA下调黑素瘤中Mcl-1的新方法。 ii）已知抑制Mcl-1的其他药物。 该项目提出通过靶向多种抗凋亡Bcl-2来开发新的组合疗法 成员，并验证治疗组合在杀死黑色素瘤中的功效，最重要的是， 黑色素瘤起始细胞群。我们相信，这里提出的研究将很快导致未来的 临床研究以及ABT-737（或类似药剂）在治疗人黑素瘤患者中的临床用途。 重要的是，这种方法不应受到个体的不同信号特征的限制。 黑素瘤。这个建议是一个合作的经验丰富的黑色素瘤基础科学家，皮肤干细胞 他是一位黑色素瘤肿瘤学家，也是人类癌症异种移植模型的专家， 将在开发基于逆转细胞凋亡抗性的黑色素瘤治疗方面取得重要进展。

A fundamental characteristic of malignant melanoma is resistance to apoptosis, which largely determines melanoma's resistance to therapy. The complex interaction of pro-apoptotic and anti-apoptotic members of the Bcl-2 family is a central control point of apoptosis and a promising drug target. The BH3 mimetic ABT-737 is a potent small molecule inhibitor of the anti-apoptotic proteins Bcl-2/Bcl-XL/Bcl-w, and it exhibits promise for cancer treatment either as a single agent or in combination therapy. We have found that ABT-737 alone induced little cytotoxicity in melanoma cells, and knockdown experiments with RNAi techniques demonstrated that anti-apoptotic protein Mcl-1, but not Bcl-2 or Bcl-XL is the main mediator of melanoma resistance to ABT-737 treatment. In addition, ABT-737 displayed strong synergistic lethality when combined with either proteasome inhibitors (MG-132 or Bortezomib) or Paclitaxel, and mechanistic studies suggested that both proteasome inhibitors and Paclitaxel neutralize Mcl-1's functions. These exciting results indicate that drugs that neutralize Mcl-1 function are outstanding candidates for combination therapy with the ABT-737 for treating melanomas, and demand validation in preclinical models and further exploring the therapeutic potential of other drugs which target Mcl-1 in combination with ABT-737. It has also been proposed that cancer initiating cells (or cancer stem cells), which preferably initiate cancers, may be responsible for cancer resistance to therapy, and eliminating these cells may be essential for developing any cancer therapy with long term success. We will refer these cells as cancer imitating cells. We propose to investigate whether enriched melanoma initiating cells are more resistant to existing chemotherapeutic agents than non-sorted cells in melanoma, and to examine whether combinations of drugs that reduce multiple anti-apoptotic defenses such as ABT-737 plus Bortezomib or Paclitaxel will overcome this resistance of melanoma initiating cells. These studies will be an important component to understand whether melanoma initiating cells are more resistant to therapy. Specific Aim 1: To directly test the responses of enriched melanoma initiating cells to existing and new therapies in vitro. i) To determine whether enriched melanoma initiating cells are more resistant to conventional chemotherapeutic agents such as Temozolomide. ii) To determine whether combinations of ABT- 737 with either Bortezomib or Paclitaxel overcome the resistance in enriched melanoma initiating cells. Specific Aim 2: To verify the efficacy of the combinations of ABT-737 with either Bortezomib or Paclitaxel for treating melanoma using two novel xenotransplantation models: a model targeting human melanoma initiating cells in vivo, and a direct xenograft model for melanoma patient samples. Specific Aim 3: To investigate the therapeutic potential of combining BH3 mimetic ABT-737 with other compounds which inhibit Mcl-1. i) A new approach to down-regulating Mcl-1 in melanomas by microRNAs. ii) Other drugs known to inhibit Mcl-1. This project proposes to develop novel combination therapeutics by targeting multiple anti-apoptotic Bcl-2 members, and to verify the efficacy of the treatment combinations in killing melanomas, and most importantly, melanoma initiating cell populations. We believe that the studies proposed here will quickly lead to future clinical studies and to the clinical use of ABT-737 (or similar agents) in treating human melanoma patients. Importantly, this approach should not be restricted by different signaling signatures of individual melanomas. This proposal is a collaboration of experienced melanoma basic scientists, a skin stem cell expert, a melanoma oncologist, and an expert in xenotransplantation models of human cancers, and this team will make important advances in developing melanoma treatments based on reversing resistance to apoptosis.