ABCG2 and osteosarcoma: These receptors have been found to be overexpressed in CSCs of different tumors [97,98], from breast cancer (ABCB1, also called P-glycoprotein, P-gp; ABCG2) [99,100,101], to neuroblastoma (ABCG2, ABCA3) [98], lung cancer (ABCG2) [102,103], ovarian cancer (ABCG2, ABCB1) [104,105], melanoma (ABCB5, ABCG2) [106,107] [108], colon cancer (ABCG2) [109], osteosarcoma (ABCG2, ABCB1, ABCB5) [110].