Abstract
Cisplatin (CDDP)-based chemotherapy is a standard treatment for gastric cancer (GC). However, chemoresistance is a major obstacle for CDDP application. Exploring underlying mechanisms of CDDP resistance development in GC and selecting an effective strategy to overcome CDDP resistance remain a challenge. Here, we demonstrate that a transmembrane ectoenzyme, CD13, endows GC patients with insensitivity to CDDP and predicts an undesirable prognosis in GC patients with CDDP treatment. Similarly, CD13 expression is positively related with CDDP resistance in GC cells. A CD13 inhibitor, Ubenimex, reverses CDDP resistance and renders GC cells sensitivity to CDDP, for which CD13 reduction is essential, and epithelial membrane protein 3 (EMP3) is a putative target downstream of CD13. Furthermore, Ubenimex decreases EMP3 expression by boosting its CpG island hypermethylation for which CD13 down-regulation is required. In addition, EMP3 is a presumptive modifier by which CD13 exerts functions in the phosphoinositol 3-kinase/protein kinase B (PI3K/AKT) pathway. Ubenimex inhibits the activation of the CD13/EMP3/PI3K/AKT/NF-κB pathway to overcome CDDP resistance in GC cells by suppressing autophagy and epithelial-mesenchymal transition (EMT). Therefore, CD13 is a potential indicator of CDDP resistance formation, and Ubenimex may serve as a potent candidate for reversing CDDP resistance in GC.