ABCG2 and cancer: miR-7-5p/ABCC1/SLC7A5, miR-107/RAD51, miR-124-3p/ABCC4/SLC16A1/MGMT, miR-212-3p/ABCG2, miR-381-3p/GJA1 and miR-485-3p/SLC40A1 may modulate pathways that confer chemoresistance to cancer cells.