In VCaP prostate cancer cells, treatment with T-474 or T-418 suppressed the phosphorylation of the known CDK8 substrate STAT1 at Ser727 both in the absence and in the presence of IFN-γ (Figure 1B), which stimulates CDK8-mediated STAT1 phosphorylation [23]. Here, STAT1 is linked to Familial prostate cancer.