BRCA1-HRD tumors with RB1 alterations had significantly higher mRNA levels of the cell proliferation-related genes PCNA (proliferating cell nuclear antigen) and MCM3 (minichromosome maintenance complex component 3) compared with BRCA1-HRD tumors without RB1 alterations (P < 0.0001; Supplementary Fig. S7). This evidence concerns the gene RB1 and hypoparathyroidism-retardation-dysmorphism syndrome.