Mechanisms of p27Kipl Proteolysis in Cancer Cells

描述（由申请人提供）：细胞周期蛋白激酶抑制剂p27Kip1是一种有效的细胞增殖抑制剂，在抑制多种人类癌症的肿瘤发生中起重要作用。p27Kip1的异常低含量与许多人类肿瘤有关，这一点已经得到了很好的证实。与许多其他肿瘤抑制蛋白（如p53）不同，p27Kip1因突变而失活在人类癌症中非常罕见，相反，p27Kip1低水平表达主要是由泛素介导的途径过度降解引起的。通过引入不可降解的p27Kip1或单纯过表达来恢复p27Kip1在肿瘤细胞中的表达，往往会诱导肿瘤凋亡或肿瘤细胞死亡。因此，体外和体内研究支持这样的观点，即稳定肿瘤细胞中的p27Kip1可能具有对抗人类癌症的治疗潜力。合成化学途径产生的小分子化合物仍然是靶向治疗和细胞毒性药物最有效的策略。通过筛选约6000个化合物的小分子文库，我们发现了两个有希望的小分子化合物，它们干扰了p27Kip1降解的关键分子相互作用。这些化合物还能稳定肿瘤细胞系中的p27Kip1。我们建议进行系统的先导化合物进化和优化，并确定我们优化的先导化合物对小鼠乳腺癌生长和转移的化疗效果。

DESCRIPTION (provided by applicant): The cyclin kinase inhibitor p27Kip1 is a potent inhibitor of cell proliferation and plays important roles in the suppression of tumorigenesis in a variety of human cancers. It has been very well established that abnormally low amounts of p27Kip1 is associated with numerous human tumors. Unlike many other tumor suppressor proteins such as p53, inactivation of p27Kip1 by mutations is very rare in human cancers instead low levels of p27Kip1 expression is primarily caused by excessive degradation by a ubiquitin-mediated pathway. Restoring p27Kip1 expression in tumor cells by introducing non-degradable p27Kip1 or simply overexpression often induces tumor apoptosis or tumor cell death. Thus in vitro and in vivo studies support the concept that stabilization of p27Kip1 in tumor cells may have therapeutic potentials to combat human cancers. Small molecule compounds generated by synthetic chemical routes continue to represent the most effective strategy for targeted therapeutics and cytotoxic drugs. By screening a small molecule library of ~6000 compounds, we discovered two promising small molecule compounds that perturb a key molecular interaction critical for p27Kip1 degradation. These compounds also stabilize p p27Kip1 in tumor cell lines. We propose to perform systematic lead compound evolution and optimization and determine chemotherapeutic efficacy of our optimized lead compounds to inhibit breast cancer growth and metastasis in mice. PUBLIC HEALTH RELEVANCE: The goal of this competitive revision is to perform systematic lead compound evolution and optimization of small molecule compound disovered from our high throughput screen for anti-tumor activity. We will also evaluate the chemotherapeutic efficacy of our optimized lead compounds to inhibit breast cancer growth and metastasis in mice.