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

描述（由申请人提供）：耐药性是对抗癌症的重大障碍。抑制抗凋亡Bcl-2蛋白的小分子有可能克服这种耐药性。目前大多数小分子抑制剂非选择性地靶向多种抗凋亡Bcl-2蛋白。有待确定的是：1)选择性抑制剂能否有效克服耐药性；2)非选择性抑制多种抗凋亡Bcl-2蛋白是否会对健康组织产生更大的毒性；3)是否非选择性抑制多种抗凋亡Bcl-2蛋白对某些肿瘤的治疗效果较差，因为所有内源性抗凋亡Bcl-2蛋白对所有肿瘤都具有保护作用尚存疑问。我们的长期目标是开发抗凋亡Bcl-2蛋白的化学探针，以帮助研究其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。本研究的中心假设是，抗凋亡Bcl-2蛋白的成员选择性抑制剂会选择性地诱导/使过度表达这种蛋白的癌症细胞凋亡。这一中心假设是基于以下观察得出的。首先，尽管一些肿瘤同时过表达多种抗凋亡Bcl-2蛋白，但许多肿瘤仅过表达一种抗凋亡Bcl-2蛋白。一种抗凋亡Bcl-2蛋白的选择性过表达表明，一种选择性抑制剂可能有效地克服耐药性。其次，Wang等人（YC 137）发现的一种Bcl-2抑制剂选择性诱导过表达Bcl-2蛋白的肿瘤细胞系凋亡，对正常细胞的毒性较小。第三，我们实验室发现的Bcl-2选择性抑制剂可以有效克服Bcl-2过表达引起的耐药（初步研究）。基于这些观察结果，本提案的重点是开发抗凋亡Bcl-2蛋白的选择性抑制剂及其对原发性肿瘤治疗的评估。具体目标是：1。鉴定一组具有严格选择性的Bcl-2、Bcl-XL和Bcl-w抑制剂（每种蛋白两种）。1)利用分子模拟技术和固相合成技术，以有前景的模板为基础，合理设计合成一个72个成员的文库；2)用固相法鉴定选择性抑制剂；3)确定它们的绝对结合选择性。2. 检查结合选择性对肿瘤对健康组织的选择性毒性的潜在影响，以及使肿瘤对常规癌症治疗敏感的潜在影响。我们将1)评估我们目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)评估我们目前的选择性抑制剂与针对血液学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.