Kawata Hirotoshi, Kamiakito Tomoko, Omoto Yawara, Miyazaki Chieko, Hozumi Yasuo, Tanaka Akira
Department of Pathology, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi, 329-0498, Japan.
Horm Cancer. 2014 Dec;5(6):414-23. doi: 10.1007/s12672-014-0199-5. Epub 2014 Aug 15.
Therapy-resistant cancer cells are a major problem in cancer research. Recent studies suggest that the epithelial-mesenchymal transition (EMT) is a key mechanism in therapy resistance. Yet, the expressions of EMT markers, EMT core regulators, and a stem cell marker of BMI1 during chemotherapy have been poorly analyzed in clinical breast cancer specimens. In the present study, we investigated the roles of RhoC under chemotherapy to follow up on earlier findings demonstrating the involvement of RhoC in prostate cancer resistance to endocrine therapy. Immunohistochemically, E-cadherin expression was significantly lower in human breast cancer specimens analyzed after chemotherapy than specimens biopsied before chemotherapy. Significant upregulation of fibronectin, a mesenchymal EMT marker, was found in post-chemotherapy analysis. A study of the EMT core regulators of SNAIL1, SNAIL2, TWIST1, and a well-known stem cell marker of BMI1 revealed no post-chemotherapy upregulation of these molecules. In contrast, RhoC expression was significantly upregulated in post-chemotherapy breast cancer specimens. MCF-7 cells stably transfected with the constitutive active (CA) RhoC plasmid manifested a reduced level of E-cadherin at the peripheries and disorganization of actin fibers, with no accompanying upregulation of SNAIL1, SNAIL2, TWIST1, or BMI1 in Western blots. Exposure of etoposide on MCF-7 cells showed RhoC upregulation together with reduced membranous expression of E-cadherin and disorganization of actin fibers. In MTT assay, however, the CA-RhoC-expressing MCF-7 cells failed to show chemotherapy resistance under etoposide treatment. Taken in sum, RhoC may contribute to an EMT-like process in human breast cancer during chemotherapy.
耐药癌细胞是癌症研究中的一个主要问题。最近的研究表明，上皮-间质转化（EMT）是耐药的关键机制。然而，在临床乳腺癌标本中，化疗期间EMT标志物、EMT核心调节因子和BMI1干细胞标志物的表达情况尚未得到充分分析。在本研究中，我们研究了化疗条件下RhoC的作用，以跟进早期发现，即RhoC参与前列腺癌对内分泌治疗的耐药性。免疫组织化学分析显示，化疗后的人类乳腺癌标本中E-钙黏蛋白的表达明显低于化疗前活检的标本。化疗后分析发现，间质EMT标志物纤连蛋白显著上调。对EMT核心调节因子SNAIL1、SNAIL2、TWIST1以及著名的干细胞标志物BMI1的研究表明，这些分子在化疗后并未上调。相反，化疗后的乳腺癌标本中RhoC表达显著上调。稳定转染组成型活性（CA）RhoC质粒的MCF-7细胞在外周表现出E-钙黏蛋白水平降低和肌动蛋白纤维紊乱，Western印迹分析显示SNAIL1、SNAIL2、TWIST1或BMI1无伴随上调。依托泊苷处理MCF-7细胞后，RhoC上调，同时E-钙黏蛋白膜表达降低和肌动蛋白纤维紊乱。然而，在MTT试验中，表达CA-RhoC的MCF-7细胞在依托泊苷处理下未表现出化疗耐药性。综上所述，RhoC可能在化疗期间促进人类乳腺癌中的类EMT过程。
