Numerous members of the IGF signalling pathway are also regulated by p-Ser294 PR in the absence of ligand.13 Experimental point mutation of Ser294 to Ala (S294A) blocked CD44+/CD24−/ALDH+ CSC expansion.15 Recently, PR, but not ER, was demonstrated to regulate a genetic programme unique to disseminating tumour cells derived from early mammary lesions arising in BALB-NeuT mice.16 PR-induced factors RANKL and Wnt1 (i.e. known PR target genes) substituted for PR-driven actions in these models. The gene discussed is IGF1; the disease is neoplasm.