Project description:Among microtubule-targeting agents, docetaxel has received recent interest owing to its good therapeutic index. Clinical trials have underlined its potential for the treatment of advanced breast cancer, although little is known about its molecular mode of action in this context. We characterized the molecular changes induced by docetaxel in two well-known human breast carcinoma cell lines. Two mechanisms of action according to drug concentration were suggested by a biphasic sensitivity curve, and were further validated by cell morphology, cell cycle and cell death changes. Two to four nanomolar docetaxel induced aberrant mitosis followed by late necrosis, and 100 nM docetaxel induced mitotic arrest followed by apoptosis. Passing through mitosis phase was a requirement for hypodiploidy to occur, as shown by functional studies in synchronized cells and by combining docetaxel with the proteasome inhibitor MG132. Transcriptional profiling showed differences according to cell line and docetaxel concentration, with cell cycle, cell death and structural genes commonly regulated in both cell lines. Although p53 targets were mainly induced with low concentration of drug in MCF7 cells, its relevance in the dual mechanism of docetaxel cytotoxicity was ruled out by using an isogenic shp53 cell line. Many of the genes shown in this study may contribute to the dual mechanism by which docetaxel inhibits the growth of breast cancer cells at different concentrations. These findings provide a basis for rationally enhancing docetaxel therapy, considering lower concentrations, and better drug combinations. Keywords: Dose-response analysis
Project description:The taxanes, namely Paclitaxel and Docetaxel, are important and widely used cancer chemotherapy drugs in the treatment of invasive and metastatic human breast cancer. Although treatment with the taxanes is beneficial to many patients, drug-responsive tumors in patients with metastatic breast cancer often display resistance to these drugs, either initially or over time following the continued administration of chemotherapy drugs. To investigate the patterns of cross-resistance with the taxane drugs and to identify potential mechanisms of resistance, we generated a series of MDA-MB-231 taxane resistant cell lines. We then used microarrays to determine gene expression differences between sensitive, Docetaxel and Paclitaxel resistant MDA-MB-231 cells. RNA isolated from three independent passages of sensitive, Docetaxel and Paclitaxel resistant cell lines and purified using the Qiagen RNeasy Mini Kit. Total RNA was processed and hybridized to Affymetrix Genechip HU133A arrays.