Imaging Biomarker Laboratory, Translational Medicine, Pfizer, Collegeville, Pennsylvania, USA.
J Pharmacol Exp Ther. 2011 Nov;339(2):421-9. doi: 10.1124/jpet.111.185249. Epub 2011 Aug 11.
The mammalian target of rapamycin (mTOR) has proven to be a valid therapeutic target in a number of human cancers, and it is a candidate for clinical trials in human breast cancer. We report on a biomarker-based translational medicine approach to assess the efficacy and mechanism of action for the mTOR inhibitor temsirolimus (CCI-779) in a mammary carcinoma OncoMouse model [polyomavirus middle T antigen (PyMT)]. The mTOR signaling pathway biomarkers were assessed using a reverse-phase protein array. Pharmacokinetics studies were conducted in both the tumor and plasma compartments. Pharmacodynamic biomarkers for compound-target engagement of tumor phospho-S6 proteins were assayed by Western blot. Temsirolimus (intravenously once a week for 2 weeks) was administered in both early and advanced stages of tumors. Biomarkers for temsirolimus effects on tumor progression were assessed by three-dimensional ultrasound imaging in combination with immunohistochemistry to assess vascular density (Texas red-dextran and CD31 immunostaining) and macrophage burden (F4/80 antigen). Tumor growth was significantly arrested in temsirolimus (25 ± 14% from 8 to 10 weeks, p < 0.05, and 26 ± 17% from 11 to 13 weeks, p < 0.01), compared with 493 ± 160 and 376 ± 50% increases, respectively, in vehicle-treated groups. Temsirolimus reduced tumor vascular density, 36 to 48 and 58 to 60%, p < 0.05, by the Texas red-dextran method or CD31-positive vessel count, respectively. Temsirolimus reduced tumor macrophage burden by 46% at 13 weeks (p < 0.05). Temsirolimus inhibited (p < 0.05) the phosphoproteins S6 pS235/236 and S6 pS240/244 up to 81 and 87%, respectively. We conclude that the multimodal biomarkers of temsirolimus efficacy and mechanism of action (phosphoproteins) strongly suggest that it might translate to therapeutic efficacy in human tumors that bear congruency to features present in the mammary carcinoma of PyMT tumors.
哺乳动物雷帕霉素靶蛋白（mTOR）已被证明是多种人类癌症的有效治疗靶点，也是在人类乳腺癌临床试验中的候选药物。我们报告了一种基于生物标志物的转化医学方法，用于评估雷帕霉素抑制剂替西罗莫司（CCI-779）在乳腺腺癌 OncoMouse 模型[多瘤病毒中 T 抗原（PyMT）]中的疗效和作用机制。使用反相蛋白阵列评估 mTOR 信号通路生物标志物。在肿瘤和血浆隔室中进行药代动力学研究。通过 Western blot 测定化合物与肿瘤磷酸化 S6 蛋白靶标结合的药效动力学生物标志物。替西罗莫司（每周静脉注射一次，连续 2 周）在肿瘤的早期和晚期阶段给药。通过三维超声成像结合免疫组织化学评估替西罗莫司对肿瘤进展的影响的生物标志物，以评估血管密度（Texas red-dextran 和 CD31 免疫染色）和巨噬细胞负担（F4/80 抗原）。与 vehicle 处理组相比，替西罗莫司显著抑制肿瘤生长（第 8 至 10 周时减少 25 ± 14%，p < 0.05，第 11 至 13 周时减少 26 ± 17%，p < 0.01）。替西罗莫司分别使肿瘤血管密度减少 36 至 48%和 58 至 60%（p < 0.05），Texas red-dextran 法或 CD31 阳性血管计数分别减少。替西罗莫司在第 13 周时减少肿瘤巨噬细胞负担 46%（p < 0.05）。替西罗莫司抑制磷酸化蛋白 S6 pS235/236 和 S6 pS240/244 的表达，抑制率分别为 81%和 87%（p < 0.05）。我们得出结论，替西罗莫司疗效和作用机制的多模态生物标志物（磷酸化蛋白）强烈表明，它可能在具有与 PyMT 肿瘤中存在的特征一致的人类肿瘤中转化为治疗效果。
