Although MT/Shc2F/2F breast cancer cells display reduced Y705-STAT3 phosphorylation in vitro (Fig. 3a), progressively growing MT/Shc2F/2F tumours (PD) that evolved in an immunocompetent background hyperactivated STAT3 compared with those that emerged in IFNγ−/− mice. This evidence concerns the gene IFNG and breast carcinoma.