SPOP and cancer: Conversely, forced expression of ΔERG significantly reduced the growth of SPOP-Y83C mutant LuCaP-147 patient-derived xenograft (PDX) cancer cells in vivo and in culture (Fig. 1e and Supplementary Fig. 3a, b)17, adding orthogonal support for a synthetic sick relationship between mutant SPOP and ΔERG in advanced prostate cancer.