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 me droxyprogesterone-acetate (MPA), was obtained by continuous exposure i n vitro to the drug. MCF-7/MPA cells were grown in the presence of 12. 5x10(-6)M MPA and were selected by increasing the concentration of the drug in the growth medium in a stepwise manner from 0.025x10(-6) M up to 12.5x10(-6) M. Comparative studies of cellular morphology, cytosol ic steroid receptor content and P-Glycoprotein expression were perform ed 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 i n terms of membrane alterations, reduced content of cytosolic progeste rone receptor; increased expression of P-glycoprotein along with reduc tion of Doxorubicin (Dx) activity on the growth of MCF-7/MPA resistant cells.