Smiyun Gregoriy, Azarenko Olga, Miller Herbert, Rifkind Alexander, LaPointe Nichole E, Wilson Leslie, Jordan Mary Ann
Department of Molecular, Cellular, and Developmental Biology, and the Neuroscience Research Institute, University of California Santa Barbara, Life Sciences Building, Room 1117, Santa Barbara, CA, 93106, USA.
Cancer Chemother Pharmacol. 2017 Jul;80(1):151-164. doi: 10.1007/s00280-017-3345-2. Epub 2017 May 31.
Cabazitaxel is a novel taxane approved for treatment of metastatic hormone-refractory prostate cancer in patients pretreated with docetaxel. Cabazitaxel, docetaxel, and paclitaxel bind specifically to tubulin in microtubules, disrupting functions essential to tumor growth. High levels of βIII-tubulin isotype expression are associated with tumor aggressivity and drug resistance. To understand cabazitaxel's increased efficacy, we examined binding of radio-labeled cabazitaxel and docetaxel to microtubules and the drugs' suppression of microtubule dynamic instability in vitro in microtubules assembled from purified bovine brain tubulin containing or devoid of βIII-tubulin. We found that cabazitaxel suppresses microtubule dynamic instability significantly more potently in the presence of βIII-tubulin than in its absence. In contrast, docetaxel showed no βIII-tubulin-enhanced microtubule stabilization. We also asked if the selective potency of cabazitaxel on βIII-tubulin-containing purified microtubules in vitro extends to cabazitaxel's effects in human tumor cells. Using MCF7 human breast adenocarcinoma cells, we found that cabazitaxel also suppressed microtubule shortening rates, shortening lengths, and dynamicity significantly more strongly in cells with normal levels of βIII-tubulin than after 50% reduction of βIII-tubulin expression by siRNA knockdown. Cabazitaxel also more strongly induced mitotic arrest in MCF7 cells with normal βIII-tubulin levels than after βIII-tubulin reduction. In contrast, docetaxel had little or no βIII-tubulin-dependent selective effect on microtubule dynamics or mitotic arrest. The selective potency of cabazitaxel on purified βIII-tubulin-containing microtubules and in cells expressing βIII-tubulin suggests that cabazitaxel may be unusual among microtubule-targeted drugs in its superior anti-tumor efficacy in tumors overexpressing βIII-tubulin.
卡巴他赛是一种新型紫杉烷类药物，被批准用于治疗经多西他赛预处理的转移性激素难治性前列腺癌患者。卡巴他赛、多西他赛和紫杉醇特异性结合微管中的微管蛋白，破坏肿瘤生长所必需的功能。高水平的βIII -微管蛋白同型表达与肿瘤侵袭性和耐药性相关。为了解卡巴他赛疗效增强的原因，我们检测了放射性标记的卡巴他赛和多西他赛与微管的结合情况，以及这两种药物在体外对由含有或不含βIII -微管蛋白的纯化牛脑微管蛋白组装而成的微管动态不稳定性的抑制作用。我们发现，在存在βIII -微管蛋白的情况下，卡巴他赛对微管动态不稳定性的抑制作用明显强于不存在βIII -微管蛋白时。相比之下，多西他赛未表现出βIII -微管蛋白增强的微管稳定作用。我们还探究了卡巴他赛在体外对含有βIII -微管蛋白的纯化微管的选择性效力是否延伸至其对人类肿瘤细胞的作用。使用MCF7人乳腺腺癌细胞，我们发现，与通过小干扰RNA敲低使βIII -微管蛋白表达降低50%后相比，在βIII -微管蛋白水平正常的细胞中，卡巴他赛对微管缩短速率、缩短长度和动态性的抑制作用也明显更强。与βIII -微管蛋白水平降低后相比，卡巴他赛在βIII -微管蛋白水平正常的MCF7细胞中诱导有丝分裂停滞的作用也更强。相比之下，多西他赛对微管动力学或有丝分裂停滞几乎没有或没有βIII -微管蛋白依赖性的选择性作用。卡巴他赛对纯化的含有βIII -微管蛋白的微管以及表达βIII -微管蛋白的细胞具有选择性效力，这表明在靶向微管的药物中，卡巴他赛在过表达βIII -微管蛋白的肿瘤中可能具有卓越的抗肿瘤疗效，这一点可能不同寻常。
