Among PDXs from patients with germline BRCA1/2-mutated breast cancer, 2 of 9 PARPi-resistant models had somatic mutations in TP53BP1 and exposure to olaparib in PDX models correlated with reduced mRNA expression of SHLD1 and SHLD2 [23, 27]. The gene discussed is BRCA1; the disease is breast carcinoma.