Exon 7 splicing of <scp>ERα</scp> predicts poor prognosis and increases phenotypic heterogeneity in luminal a subtype breast cancer

ERαΔ7 is one of the most frequently observed splice variants of the ESR1 gene in breast cancer but its functions remain largely unknown. Here we report that ERαΔ7 predicted poor survival in luminal A type breast cancer from TCGA data. ERαΔ7 occurred more frequently in luminal type breast cancer, with expression inversely correlating with ESR1 expression. Functionally, ERαΔ7-expressing MCF-7 cells were found to have lower death rates at the expense of reduced growth and migration, while also being responsive to estrogen deprivation. Furthermore, molecular dynamics simulation showed that estradiol can bind to ERαΔ7. Our study indicated that ERαΔ7 might serve as a potential prognostic marker in Luminal A type breast cancer and has different functions from those of canonical ERα-expressing cells.