Oliver Christopher L, Bauer Joshua A, Wolter Keith G, Ubell Mathew L, Narayan Ajita, O'Connell Kathleen M, Fisher Susan G, Wang Shaomeng, Wu Xihan, Ji Min, Carey Thomas E, Bradford Carol R
Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, Michigan 48109-0312, USA.
Clin Cancer Res. 2004 Nov 15;10(22):7757-63. doi: 10.1158/1078-0432.CCR-04-0551.
Bcl-xL overexpression is common in head and neck squamous cell carcinomas (HNSCC) and correlates with resistance to chemotherapy. Thus, a nonpeptidic, cell-permeable small molecule that mimics the BH3 domain of proapoptotic proteins may inhibit Bcl-xL function and have therapeutic potential for HNSCC by overcoming drug-resistance. (-)-Gossypol, the levorotatory isomer of a natural product isolated from cottonseeds and roots, was recently discovered to bind to the BH3 binding groove of Bcl-xL and Bcl-2.
We investigated the in vitro effects of (-)-gossypol on HNSCC cell lines as well as on fibroblast and keratinocyte cultures by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell survival assays and assessed the results with respect to Bcl-2 family protein expression.
We observed dose-dependent growth inhibition of 10 HNSCC cell lines at biologically achievable doses (2.5-10 micromol/L). (-)-Gossypol doses required to inhibit the growth of human fibroblast cell lines by 50% were 2- to 10-fold higher than for HNSCC cell lines. To inhibit human oral keratinocyte growth by 50%, (-)-gossypol concentrations were 2-to 3-fold higher than for HNSCC cell lines.
There is a direct correlation between Bcl-xL-to-Bcl-xS ratios and sensitivity to (-)-gossypol. This agent induced apoptosis in a much higher proportion of cells with wild-type p53. Importantly, cell lines resistant to cisplatin were very sensitive to (-)-gossypol. These results demonstrate that (-)-gossypol has potent antitumor activity in HNSCC in vitro. This agent may be developed as a novel therapeutic agent for HNSCC, either alone or in combination with existing chemotherapeutic agents.
Bcl-xL过表达在头颈部鳞状细胞癌（HNSCC）中很常见，且与化疗耐药相关。因此，一种模拟促凋亡蛋白BH3结构域的非肽类、细胞可渗透小分子可能抑制Bcl-xL功能，并通过克服耐药性对头颈部鳞状细胞癌具有治疗潜力。（-）-棉酚是从棉籽和根部分离出的天然产物的左旋异构体，最近被发现可与Bcl-xL和Bcl-2的BH3结合凹槽结合。
我们通过使用3-（4,5-二甲基噻唑-2-基）-2,5-二苯基四氮唑溴盐（MTT）细胞存活试验，研究了（-）-棉酚对HNSCC细胞系以及成纤维细胞和角质形成细胞培养物的体外作用，并根据Bcl-2家族蛋白表达评估了结果。
我们在生物学可达到的剂量（2.5 - 10微摩尔/升）下观察到10种HNSCC细胞系的剂量依赖性生长抑制。抑制人成纤维细胞系生长50%所需的（-）-棉酚剂量比HNSCC细胞系高2至10倍。为抑制人口腔角质形成细胞生长50%，（-）-棉酚浓度比HNSCC细胞系高2至3倍。
Bcl-xL与Bcl-xS的比例与对（-）-棉酚的敏感性之间存在直接相关性。该药物在野生型p53的细胞中诱导凋亡的比例要高得多。重要的是，对顺铂耐药的细胞系对（-）-棉酚非常敏感。这些结果表明，（-）-棉酚在体外对头颈部鳞状细胞癌具有强大的抗肿瘤活性。该药物可单独或与现有化疗药物联合开发成为头颈部鳞状细胞癌的新型治疗药物。
