ABCG2 and neoplasm: Resveratrol, a polyphenolic phytochemical, improves the anti-tumor activity of gemcitabine by reducing ZEB1, Slug, and Snail expression as well as Nanog and Oct4 expression and that of drug-resistant ATP-Binding Cassette (ABC) transporter genes, in addition to pathways governing the self-renewal of CSCs [114].