To assess whether such correlation would also operate in patients, we took advantage of two previously described isogenic patient-derived xenograft (PDX) models of prostate cancer – termed MR-0009 and MR-019145, characterized by the presence of BRCA2 germline and secondary reversion mutations conferring sensitivity or resistance to PARPi, respectively (Fig. 3H). The gene discussed is BRCA2; the disease is prostate cancer.