Department of Clinical Oncology, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, N.T., Hong Kong.
Biochem Pharmacol. 2012 May 1;83(9):1146-58. doi: 10.1016/j.bcp.2012.01.013. Epub 2012 Jan 20.
The mammalian target of rapamycin (mTOR) and the microtubules are prominent druggable targets for hepatocellular carcinoma (HCC). PI3K/Akt/mTOR activation is associated with resistance to microtubule inhibitors. Here, we hypothesized that co-targeting of mTOR (by mTOR inhibitor temsirolimus) and the microtubule (by microtubule-destabilizing agent vinblastine) would be more efficacious than single targeting in HCC models. In vitro studies showed that effective inhibition of mTOR signaling with temsirolimus alone was able to suppress HCC cell growth in a dose-dependent manner. Among five cell lines tested, Huh7 was the most temsirolimus-sensitive (IC(50)=1.27±0.06μM), while Hep3B was the most temsirolimus-resistant (IC(50)=52.95±17.14μM). We found that co-targeting of mTOR (by temsirolimus) and the microtubule (by vinblastine, at low nM) resulted in marked growth inhibition in Huh7 cells and synergistic growth inhibition in Hep3B cells (achieving maximal growth inhibition of 80-90%), demonstrating potent antitumor activity of this novel combination. In vivo studies showed that temsirolimus treatment alone for 1 week was able to inhibit the growth of Huh7 xenografts. Strikingly, the temsirolimus/vinblastine combination induced a significant and sustained antitumor activity (up to 27 days post-treatment), with effective reduction of tumor vessel density in both Huh7 and Hep3B xenograft models. Mechanistic investigation revealed that this marked antitumor effect was accompanied by specific and concerted down-regulation of several key anti-apoptotic/survival proteins (survivin, Bcl-2, and Mcl-1), which was not observed in single agent treatments. Our findings demonstrated that the potent anti-cancer activity of this co-targeting strategy was indeed mediated in parts by inhibition of these key survival/anti-apoptotic proteins.
哺乳动物雷帕霉素靶蛋白（mTOR）和微管是肝癌（HCC）的重要药物靶点。PI3K/Akt/mTOR 的激活与对微管抑制剂的耐药性有关。在这里，我们假设 mTOR（通过 mTOR 抑制剂替西罗莫司）和微管（通过微管不稳定剂长春碱）的共同靶向治疗将比 HCC 模型中的单一靶向治疗更有效。体外研究表明，替西罗莫司单独有效抑制 mTOR 信号能够以剂量依赖的方式抑制 HCC 细胞的生长。在测试的五个细胞系中，Huh7 对替西罗莫司最敏感（IC50=1.27±0.06μM），而 Hep3B 对替西罗莫司最耐药（IC50=52.95±17.14μM）。我们发现，mTOR（通过替西罗莫司）和微管（通过长春碱，在低 nM 时）的共同靶向治疗导致 Huh7 细胞的生长明显抑制，并在 Hep3B 细胞中协同生长抑制（达到 80-90%的最大生长抑制），表明这种新组合具有强大的抗肿瘤活性。体内研究表明，替西罗莫司单独治疗 1 周即可抑制 Huh7 异种移植物的生长。引人注目的是，替西罗莫司/长春碱联合治疗诱导了显著和持续的抗肿瘤活性（治疗后长达 27 天），在 Huh7 和 Hep3B 异种移植模型中均有效降低了肿瘤血管密度。机制研究表明，这种显著的抗肿瘤作用伴随着几种关键抗凋亡/存活蛋白（survivin、Bcl-2 和 Mcl-1）的特异性和协同下调，这在单一药物治疗中未观察到。我们的研究结果表明，这种共同靶向策略的强大抗癌活性确实部分是通过抑制这些关键存活/抗凋亡蛋白来介导的。
