ESR1 and cancer: Previous studies have shown that chlorohyssopifolin A (1) inhibits cell viability of several cancer cell lines, including 1A9 (ovarian cancer), KB (nasopharyngeal cancer) and KB-V (vincristine-resistant KB subline), and that chlorohyssopifolin C (3) showed significant cytotoxicity against MCF-7 (estrogen receptor positive breast cancer).