PARP1 and breast cancer: Ursolic acid isolated from the ethyl acetate fraction of Betula utilis D.Don methanolic extract was found to be highly effective as cytotoxic agent on MCF-7 breast cancer cells while non-tumorigenic breast epithelial MCF-10A cells remained unaffected, thus emphasizing a selective anticancer activity; an apoptotic effect was identified and attributed to the up-regulation of DR4, DR5 and PARP cleavage (145).