ABCG2（ATP binding cassette subfamily G member 2 (Junior blood group)），癌症关联基因，基因ID：9429，由该基因编码的膜相关蛋白包含在ATP结合盒（ABC）转运子的超家族中。ABC蛋白通过细胞外膜和细胞内膜转运各种分子。ABC基因分为7个不同的亚家族（abc1，mdr/tap，mrp，ald，oabp，gcn20，white）。这种蛋白是白色亚家族的成员。或者称为乳腺癌抵抗蛋白，这种蛋白作为外源性转运蛋白发挥作用，可能在多药耐药中起主要作用。它可能是对米托蒽醌和蒽环类药物暴露的一种细胞防御机制。该蛋白在胎盘中有明显的表达，这可能提示该分子在胎盘组织中的潜在作用。已发现编码该基因不同亚型的多种转录变体。The membrane-associated protein encoded by this gene is included in the superfamily of ATP-binding cassette (ABC) transporters. ABC proteins transport various molecules across extra- and intra-cellular membranes. ABC genes are divided into seven distinct subfamilies (ABC1， MDR/TAP， MRP， ALD， OABP， GCN20， White). This protein is a member of the White subfamily. Alternatively referred to as a breast cancer resistance protein， this protein functions as a xenobiotic transporter which may play a major role in multi-drug resistance. It likely serves as a cellular defense mechanism in response to mitoxantrone 。