Bcl-2 selective inhibitors: development and application to cancer treatment

描述(申请人提供)：抗药性是抗击癌症的重要绊脚石。抑制抗细胞凋亡的Bcl-2蛋白的小分子有可能克服这种耐药性。目前的小分子抑制剂大多非选择性地靶向多种抗凋亡的Bcl2蛋白。目前尚不确定：1)一种选择性抑制物在克服耐药性方面是否有效；2)非选择性抑制多种抗凋亡蛋白是否会对健康组织产生更大的毒性；3)非选择性抑制多种抗凋亡蛋白是否在某些癌症的治疗中效果不佳，因为所有内源性抗凋亡蛋白在所有肿瘤中是否都具有保护功能尚存疑问。我们的长期目标是开发抗凋亡的Bcl-2蛋白的化学探针，以帮助研究它们在各种肿瘤中的功能，并开发用于癌症治疗的小分子抑制剂。我们对这项拟议研究的中心假设是，抗凋亡蛋白的成员选择性抑制剂将选择性地诱导过度表达这种蛋白的癌症/使其对细胞凋亡敏感。这一中心假设是基于以下观察得出的。首先，虽然有些肿瘤同时过表达多个抗凋亡蛋白，但许多肿瘤只过表达单一的抗凋亡蛋白。一种抗细胞凋亡蛋白的选择性过表达表明，选择性抑制剂将有效地克服耐药。其次，Wang等人(YC137)发现的一种Bcl-2抑制剂选择性地诱导肿瘤细胞系凋亡，该肿瘤细胞系过度表达Bcl-2蛋白，对正常细胞毒性较小。第三，我们实验室发现的一种Bcl2选择性抑制剂可以有效地克服Bcl2过表达诱导的耐药性(初步研究)。基于这些观察，这项建议的重点是开发抗细胞凋亡的Bcl-2蛋白的选择性抑制剂，并评估它们在癌症治疗中对原发肿瘤的作用。其具体目的是：1.筛选一组具有严格选择性(每种蛋白2个)的Bcl2、Bclxl和Bclw的抑制剂。我们将1)通过分子模拟和固相合成，合理地设计和合成一个基于有前景的模板的72元文库；2)通过固相分析鉴定选择性抑制剂；3)确定它们的绝对结合选择性。2.研究结合选择性对肿瘤对健康组织的选择毒性的影响，以及对传统癌症治疗增敏肿瘤的可能性。我们将1)评估我们当前的选择性和非选择性抑制剂对血液原发肿瘤和健康血细胞的细胞毒性；2)评估我们当前的选择性抑制剂与针对血液原发肿瘤的临床治疗的潜在协同作用。

DESCRIPTION (provided by applicant): Drug resistance is a significant stumbling block in the fight against cancer. Small molecules that inhibit anti- apoptotic Bcl-2 proteins have the potential to overcome such drug resistance. Most of current small- molecule inhibitors non-selectively target multiple anti-apoptotic Bcl-2 proteins. It remains to be determined: 1) whether a selective inhibitor will be effective in overcoming drug resistance; 2) whether non-selectively inhibiting multiple anti-apoptotic Bcl-2 proteins may introduce more toxicity against healthy tissues; 3) whether non-selectively inhibiting multiple anti-apoptotic Bcl-2 proteins may be less effective in the treatment of certain cancers since it is questionable that all endogenous anti-apoptotic Bcl-2 proteins have protective functions in all tumors. Our long-term goal is to develop chemical probes for anti-apoptotic Bcl-2 proteins to help study their functions in various tumors and to develop small-molecule inhibitors for cancer treatment. Our central hypothesis for this proposed research is that member-selective inhibitors of anti-apoptotic Bcl-2 proteins will selectively induce / sensitize the cancers that overexpress such a protein to apoptosis. This central hypothesis is formulated based on the following observations. First, though some tumors simultaneously overexpress multiple anti-apoptotic Bcl-2 proteins, many tumors only overexpress a single anti-apoptotic Bcl- 2 protein. The selective overexpression of one anti-apoptotic Bcl-2 protein suggests that a selective inhibitor would be effective in overcoming the drug resistance. Second, a Bcl-2 inhibitor identified by Wang et al (YC 137) selectively induces apoptosis in a tumor cell line that overexpresses Bcl-2 protein and shows less toxicity to normal cells. Third, a Bcl-2 selective inhibitor identified in our laboratory can effectively overcome the drug resistance induced by Bcl-2 overexpression (Preliminary Studies). Based on these observations, the focus of this proposal is on the development of selective inhibitors for anti-apoptotic Bcl-2 proteins and their evaluation against primary tumors for cancer treatment. The specific aims are to: 1. Identify a set of inhibitors for Bcl-2, Bcl-XL, and Bcl-w with stringent selectivity (two for each protein). We will 1) rationally design and synthesize a 72-member library based on a promising template by using molecular modeling and solid-phase synthesis; 2) identify the selective inhibitors by a solid-phase assay; and 3) determine their absolute binding selectivity. 2. Examine the effect of binding selectivity on the potential for selective toxicity to tumors over healthy tissues and the potential of sensitizing tumors to conventional cancer treatment. We will 1) evaluate our current selective and non-selective inhibitors for their cytotoxicity against hematologic primary tumors and healthy blood cells; 2) evaluate our current selective inhibitors for their potential synergism with clinical therapies against the hematologic primary tumors.