Search

Aromatase inhibitors (AI) have improved the treatment of oestrogen receptor positive (ER+) breast cancer. Despite the efficacy of these agents over 40% of patients relapse with endocrine resistant disease. Here we describe an in vitro model of acquired resistance to long-term oestrogen deprivation (LTED). The LTED cells retain expression of the ER and appear hypersensitive to oestrogen as a result of altered kinase activity. Furthermore analysis of temporal changes in gene expression during the acquisition of resistance highlight growth factor receptor pathways as key mediators of this adaptive process.

Introduction Imatinib mesylate is a tyrosine kinase receptor inhibitor targeted against PDGFR α and β, c-kit and bcr-abl. These receptors regulate cellular processes such as proliferation, differentiation, and survival. This study was performed to evaluate the effects of imatinib on breast cancer cell lines with respect to the activity of PDGFR β and Akt: a downstream modulator of cell growth and survival. Methods Expression of imatinib targets was analyzed with reverse transciptase PCR and immunoblotting assays in the breast cell lines MDA MB 231, MCF 7, ZR 75-1, and T 47-D. Changes on receptor expression and phosphorylation status under imatinib were evaluated using drug concentrations of 2 to 10 μM. The anti-proliferative and pro-apoptotic effects of imatinib alone and in combination with vinorelbine were investigated with an MTT and TUNEL assay. Results Imatinib inhibited growth and induced apoptosis of all cell lines examined. This effect was increased when combined with vinorelbine. A dose-dependent inhibitory effect on the phosphorylation of PDGFR β and Akt was detected. Conclusions The growth inhibitory effect of imatinib on breast cell lines may be caused by inhibiting the activity of the tyrosine kinases PDGFR β and Akt. Imatinib is a promising novel drug for targeted therapy of breast cancer patients.