Since MF was effective in growth inhibiting the 10 human cancer cell lines included in this study, we subsequently evaluated in all cells the expression levels of classical, nuclear PR isoforms A (PR-A) and B (PR-B), GR isoforms alpha (GR-α) and beta (GR-β), AR, and ER isoform alpha (ER-α) to determine whether there is a correlation between the expression of one or more receptor types and the sensitivity to MF-induced growth inhibition when MF is used at cytostatic, non-lethal doses. Here, RB1 is linked to cancer.