A potential relevance of PARP-1 inhibition in ER+ breast cancers might emerge from our functional analyses of a new single nucleotide variant (SNV) within the aromatase promoter I.3/II-region (SNV(T-241C); NC_000015.10:n.51243270T>C; GRCh38.p13 human genome reference). Here, PARP1 is linked to breast cancer.