ABCG2 and gastric cancer: Preliminary experiments of the present study indicated that celecoxib can inhibit the proliferation of SGC7901 human gastric cancer cells in vitro and may be combined with 5-Fu to reduce the expression of cancer stem cell markers such as hypoxia-inducible factor-2α (HIF-2α), ATP-binding cassette transporter G2 (ABCG2) and octamer-binding transcription factor 4 (Oct-4).