PGRMC1 and breast carcinoma: To gain insight into the mechanism by which PGRMC1 impacts proliferation of breast cancer cells, we screened for potential PGRMC1 interaction partners upon treatment with the PPP NET by mass spectrometry analysis of proteins co-immunoprecipitated from whole-cell lysates of MCF7/PGRMC1 cells utilizing an antibody directed against the HA-tag (Table S1).