We speculate that in MDA-MB-468 cells, phosphorylation of EGFR Ser1070 causes EGFR to translocate from the cell membrane to the cytoplasm to be degraded, and relies heavily on the presence of EGFR for cell survival, as it lacks both ER and PR.35–37 On the other hand, ZR-75-1 can rely on both ER and PR, and can, therefore, internalise and degrade EGFR faster and more readily.38,39 Moreover, phosphoproteome analysis of MCF10A breast cells, in which PGRMC1 overexpression was induced, showed changes to PI3K/AKT signalling in cancer and signalling by receptor tyrosine kinases. Here, PGRMC1 is linked to cancer.