Wang Harris, Vo The, Hajar Ali, Li Sarah, Chen Xinmei, Parissenti Amadeo M, Brindley David N, Wang Zhixiang
Department of Medical Genetics, University of Alberta, Edmonton, AB T6G 2H7, Canada.
BMC Cancer. 2014 Jan 22;14:37. doi: 10.1186/1471-2407-14-37.
Chemoresistance is a major factor involved in a poor response and reduced overall survival in patients with advanced breast cancer. Although extensive studies have been carried out to understand the mechanisms of chemoresistance, many questions remain unanswered.
In this research, we used two isogenic MCF-7 breast cancer cell lines selected for resistance to doxorubicin (MCF-7DOX) or docetaxel (MCF-7TXT) and the wild type parental cell line (MCF-7CC) to study mechanisms underlying acquired resistance to taxanes in MCF-7TXT cells. Cytotoxicity assay, immunoblotting, indirect immunofluorescence and live imaging were used to study the drug resistance, the expression levels of drug transporters and various tubulin isoforms, apoptosis, microtubule formation, and microtubule dynamics.
MCF-7TXT cells were cross resistant to paclitaxel, but not to doxorubicin. MCF-7DOX cells were not cross-resistant to taxanes. We also showed that multiple mechanisms are involved in the resistance to taxanes in MCF-7TXT cells. Firstly, MCF-7TXT cells express higher level of ABCB1. Secondly, the microtubule dynamics of MCF-7TXT cells are weak and insensitive to the docetaxel treatment, which may partially explain why docetaxel is less effective in inducing M-phase arrest and apoptosis in MCF-7TXT cells in comparison with MCF-7CC cells. Moreover, MCF-7TXT cells express relatively higher levels of β2- and β4-tubulin and relatively lower levels of β3-tubulin than both MCF-7CC and MCF-7DOX cells. The subcellular localization of various β-tubulin isoforms in MCF-7TXT cells is also different from that in MCF-7CC and MCF-7DOX cells.
Multiple mechanisms are involved in the resistance to taxanes in MCF-7TXT cells. The high expression level of ABCB1, the specific composition and localization of β-tubulin isoforms, the weak microtubule dynamics and its insensitivity to docetaxel may all contribute to the acquired resistance of MCF-7TXT cells to taxanes.
化疗耐药是晚期乳腺癌患者反应不佳和总生存期缩短的主要因素。尽管已经进行了广泛的研究来了解化疗耐药的机制，但许多问题仍未得到解答。
在本研究中，我们使用了两种对阿霉素（MCF-7DOX）或多西他赛（MCF-7TXT）具有耐药性的同基因MCF-7乳腺癌细胞系以及野生型亲本细胞系（MCF-7CC），以研究MCF-7TXT细胞对紫杉烷获得性耐药的潜在机制。采用细胞毒性测定、免疫印迹、间接免疫荧光和实时成像技术研究耐药性、药物转运蛋白和各种微管蛋白亚型的表达水平、细胞凋亡、微管形成以及微管动力学。
MCF-7TXT细胞对紫杉醇具有交叉耐药性，但对阿霉素没有交叉耐药性。MCF-7DOX细胞对紫杉烷没有交叉耐药性。我们还表明，MCF-7TXT细胞对紫杉烷的耐药涉及多种机制。首先，MCF-7TXT细胞中ABCB1的表达水平较高。其次，MCF-7TXT细胞的微管动力学较弱，对多西他赛治疗不敏感，这可能部分解释了为什么与MCF-7CC细胞相比，多西他赛在诱导MCF-7TXT细胞的M期阻滞和细胞凋亡方面效果较差。此外，与MCF-7CC和MCF-7DOX细胞相比，MCF-7TXT细胞中β2-和β4-微管蛋白的表达水平相对较高，而β3-微管蛋白水平相对较低。MCF-7TXT细胞中各种β-微管蛋白亚型的亚细胞定位也与MCF-7CC和MCF-7DOX细胞不同。
MCF-7TXT细胞对紫杉烷的耐药涉及多种机制。ABCB1的高表达水平、β-微管蛋白亚型的特定组成和定位、微管动力学较弱及其对多西他赛的不敏感性可能都导致了MCF-7TXT细胞对紫杉烷的获得性耐药。
