Noncoding somatic and inherited single-nucleotide variants converge to promote ESR1 expression in breast cancer.

Mathieu Lupien and colleagues report an enrichment of somatic mutations at the ESR1 cis-regulatory region in 7% of ESR1-positive breast cancers. They find that the activity of the recurrently mutated ESR1 enhancer is also influenced by breast cancer risk–associated SNPs.