ABCG2 and uterine corpus sarcoma: Indeed, various molecular mechanisms are involved in this MDR phenotype, particularly in uterine sarcoma, such as the loss of induction of apoptotic cell death pathways [43], the exacerbated phase I/II drug metabolism (i.e., increased expression and activity of metabolizing enzymes), or the deregulated expression and activity of plasma membrane phase III efflux transporters (ABC transporters).