Roles of Connective Tissue Growth Factor in Breast Cancer Metastasis and Drug Resistance

• Main Authors: Pai-Sheng Chen, 陳百昇
• Other Authors: 郭明良
• Format: Others
• Language: en_US
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/52729798919575180089

博士 === 國立臺灣大學 === 毒理學研究所 === 97 === Connective tissue growth factor (CTGF) expression is elevated in advanced stages of breast cancer, but the regulatory role of CTGF in invasive breast cancer cell phenotypes is unclear. In the first part (Chapter 1), we found that over-expression of CTGF in MCF-7 cells (MCF-7/CTGF) enhanced cellular migratory ability and spindle-like morphological alterations, as evidenced by actin polymerization and focal adhesion complex aggregation. Reducing the CTGF level in MDA-MB-231 (MDA231) cells by antisense CTGF cDNA (MDA231/AS cells) impaired cellular migration and promoted a change to an epithelial-like morphology. A neutralizing antibody to integrin alphavbeta3 significantly attenuated CTGF-mediated ERK1/2 activation and cellular migration, indicating that integrin alphavbeta3/ERK1/2 signaling pathway was critical in mediating CTGF function. Moreover, the cDNA microarray analysis revealed CTGF-mediated regulation of the critical prometastatic gene S100A4. Transfection of MCF-7/CTGF cells with AS-S100A4 reversed the CTGF-induced cellular migratory ability, while over-expression of S100A4 in MDA231/AS cells restored their high migratory ability. Genetic and pharmacological manipulations suggested that the CTGF–mediated S100A4 up-regulation was dependent on ERK1/2 activation, with expression levels of CTGF and S100A4 being closely correlated with human breast tumors. We conclude that CTGF plays a critical role in the migratory/invasive processes in human breast cancer by a mechanism involving the activation of the integrin alphavbeta3/ERK1/2/S100A4 pathway. In addition, since most metastatic disease only responds transiently to chemotherapy and most cancer patients die of metastatic disease. In the second part (Chapter 2), we examined whether CTGF expression could confer drug resistance in human breast cancer. In breast cancer patients who received neoadjuvant chemotherapy, CTGF expression inversely associated with chemotherapy response. Overexpression of CTGF in MCF-7 cells enhanced clonogenic ability, cell viability and resistance to apoptosis upon exposure to doxorubicin and paclitaxel. Reducing the CTGF level in MDA-MB-231 cells decreased these effects. CTGF overexpression resulted in resistance to doxorubicin- and paclitaxel-induced apoptosis by up-regulation of Bcl-xL and cIAP1. Knockdown of Bcl-xL or cIAP1 with specific siRNAs abolished the CTGF-mediated resistance to apoptosis induced by the chemotherapeutic agents in MCF-7/CTGF cells. Inhibition of ERK1/2 effectively reversed the resistance to apoptosis as well as the up-regulation of Bcl-xL and cIAP1 in MCF-7/CTGF cells. A neutralizing antibody against integrin alphavbeta3 significantly attenuated CTGF-mediated ERK1/2 activation and up-regulation of Bcl-xL and cIAP1, indicating that the integrin alphavbeta3/ERK1/2 signaling pathway is essential for CTGF functions. The Bcl-xL level also correlated with the CTGF level in breast cancer patients. We concluded that CTGF expression could confer resistance to chemotherapeutic agents through ERK1/2-mediated Bcl-xL/cIAP1 up-regulation of a survival pathway.