Nonetheless, it has been reported that clinical resistance to chemotherapy in a series of cancers is strongly associated with the overexpression of the ABC transporters, and overexpression of ABCB1 and ABCG2 in cancers may come with poor prognosis and high risk of death (Marsh et al., 2007; Campa et al., 2012; Hlavata et al., 2012; Litviakov et al., 2013; Bartholomae et al., 2016). The gene discussed is ABCG2; the disease is cancer.