Morphological and biochemical features of a medroxyprogesterone acetate (MPA)-resistant MCF-7 breast cancer cell line.

An MCF-7 human breast cancer line variant (MCF-7/MPA), resistant to medroxyprogesterone-acetate (MPA), was obtained by continuous exposure in vitro to the drug. MCF-7/MPA cells were grown in the presence of 12.5 x 10(-6) M MPA and were selected by increasing the concentration of the drug in the growth medium in a stepwise manner from 0.025 x 10(-6) M up to 12.5 x 10(-6) M. Comparative studies of cellular morphology, cytosolic steroid receptor content and P-Glycoprotein expression were performed on both MCF-7 parental line and MCF-7/MPA variant. MCF-7/MPA cells, when compared to the parental line, exhibit a different morphology in terms of membrane alterations, reduced content of cytosolic progesterone receptor, increased expression of P-glycoprotein along with reduction of Doxorubicin (Dx) activity on the growth of MCF-7/MPA resistant cells.