To carry out these studies, we developed a new in vitro model of de novo CDK12BAL prostate cancer by generating a cell line (LuCaP189.4_CL) from the LuCaP189.4 patient derived xenograft (PDX) (51) that carries bi-allelic CDK12 frameshift mutations (p.S345Gfs*10, p.S521Qfs*89) (Fig S4h). Here, CDK12 is linked to prostate carcinoma.