Medroxyprogesterone acetate-driven increase in breast cancer risk might be mediated via cross-talk with growth factors in the presence of progesterone receptor membrane component-1

We could demonstrate a significant proliferative effect of MPA when combined with high concentrations of growth factors. This effect was more pronounced in breast cancer cells overexpressing PGRMC1. These results may be of clinical relevance since in the combined WHI trial an increased breast cancer risk was found during treatment with conjugated equine estrogens plus MPA.