For example, drug resistant cell lines that overexpress P gly coprotein 170 also have significantly upregulated Cox 2 expression, selleck kinase inhibitor indicating a strong corre lation between Cox 2 expression and resistance to che motherapy in breast cancer cell lines. In addition, selective inhibition of Cox 2 suppresses the invasion activity of oral squamous cells through downregulation of a matrix metalloproteinase 2 activating mechanism. Cox 2 overexpression in human breast cancer cells enhances their motility and invasiveness. Furthermore, Cox 2 overexpression in human breast cancers correlates with several clinical parameters that are characteristic of aggressive breast disease. Inhibitors that are selective for Cox 2 have been developed as anti inflammatory agents and also show effective anticancer properties in breast cancer patients at risk for disease recurrence.

Furthermore, inhibition of Cox 2 has a significant effect on the drug resistance and metastatic potential of cancer cells. Knocking down Cox 2 using small interfering RNA or Cox 2 inhibitors suppresses cell growth and invasion and enhances the chemosensitivity of cancers, including breast cancer. Several lines of evidence have suggested that metasta sis may be enhanced by an ability to resist apoptosis and highly metastatic cancer cells exhibit greater survi val ability and resistance to apoptosis than poorly meta static cells. Therefore, cancer cells may acquire invasive and metastatic properties during the process of becoming resistant, a mechanism that remains poorly understood.

To identify genes associated with the inva sive and metastatic activities of drug resistant cells, we analyzed changes in gene expression in doxorubicin resistant MCF 7 breast cancer cells that we established using DNA array analysis. We observed invasive activities related to high expression of Cox 2 in MCF 7 DOX cells. Having identified Cox 2 as an important regulator of the invasiveness of MCF 7 DOX cells, we next asked which upstream pathway modulates the expression of Cox 2 and how the invasive activities increased doxoru bicin resistant cancer in this study. Methods Animals, cells, and materials Female 6 week old Balb c nude mice were purchased from Charles River Laboratories. The human breast cancer cell lines MDA MB 231, MCF 7, and T 47D were obtained from the Ameri can Type Culture Collection.

MCF 7 DOX cells were derived from MCF Cilengitide 7 cells by continuous culture in the presence of doxorubicin for more than 3 months. Exposure of MCF 7 cells to stepwise increasing concentrations of doxorubicin resulted in the selection of doxorubicin resistant MCF 7 DOX cells. Exposure to doxorubicin was terminated 4 days prior to the experiments. Cells were cultured in Dulbeccos mod ified Eagles medium supplemented with 10% fetal bovine serum and penicillin streptomycin. Cell culture inserts incorporating polyethylene terephthalate membranes and 24 well plates for invasion assays were purchased from Costar.