ESR1 and breast cancer: Across these studies, both crude venoms and purified components—such as phospholipases A2, L-amino acid oxidases, disintegrins, and cytotoxins—were shown to exert marked cytotoxic activity against a range of breast cancer cell lines, including MDA-MB-231 (triple-negative), MCF-7 (ER/PR-positive), and SK-BR-3 (HER2-positive).