To examine whether the presence of the estrogen receptor (ER) or progesterone receptor (PR) in the luminal A-derived cancer cell lines affects LIP/LAP expression we cultivated MCF-7 cells in hormone-depleted medium and treated the cells with estrogen (E) or progesterone (P) and did not observe significant changes in the LIP/LAP isoform ratio (Supplementary Fig. 1b). This evidence concerns the gene ESR1 and cancer.