In order to better define LOX-1 and its splice variant Δ4 in breast cancer, we analyzed their expression in three different phenotypes of breast cancer cell lines, MCF-7 (ER+/PR+, luminal A), MDA-MB-231, deriving from a triple-negative tumor and SK-BR-3 (HER-2 enriched). The gene discussed is ESR1; the disease is breast cancer.