STAT3 and neoplasm: Surprisingly, and in sharp contrast to the oncogenic role of Stat3 in many cancers14, 15, Ptenpc−/−Stat3pc−/− mice showed accelerated PCa formation with up to sixfold increase in tumour weight compared with Ptenpc−/− tumours at different stages of PCa development (Fig. 1c,d and Supplementary Fig. 2d,e).