Platinum drugs upregulate CXCR4 and PD-L1 expression via ROS-dependent pathways, with implications for novel combined treatment in gastric cancer.

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CXC chemokine receptor 4 (CXCR4) and programmed cell death-ligand 1 (PD-L1) are two critical molecules involved in the tumor immune microenvironment. However, the impact of platinum drugs, such as cisplatin, on CXCR4 or PD-L1 expression and the underlying mechanisms in gastric cancer (GC) remain unknown. Moreover, the correlation between their expression levels in GC remains elusive. Immunohistochemistry, western blot, and RT-qPCR were performed to determine the expression pattern of CXCR4 and PD-L1 in GC. Clinical samples, patient-derived xenografts, and cell-derived xenografts were utilized to investigate the effects of platinum drugs on the expression levels of CXCR4 and PD-L1. Postchemotherapy resected GC tumor tissues showed higher CXCR4 and PD-L1 expression levels than pretreatment biopsies (p < 0.05). Similarly, GC xenografts treated with platinum-based chemotherapy exhibited increased CXCR4 and PD-L1 expression levels compared to saline-treated controls (p < 0.05). A positive correlation was detected between the expression levels of CXCR4 and PD-L1 in GC tumor tissues. Increased levels of CXCR4 and PD-L1 expression, in a dose- and time-dependent manner upon cisplatin treatment, were observed in GC cells (p < 0.05). Cisplatin-induced CXCR4 upregulation relies on ROS/HIF-1α and ROS/NF-κB pathways, while cisplatin-induced PD-L1 upregulation is cyclic GMP-AMP synthase/stimulator of IFN genes-dependent and associated with elevated ROS levels in GC cells. CXCR4 expression was found to be positively correlated with PD-L1 expression in GC. Platinum drugs upregulated the levels of CXCR4 and PD-L1 expression in GC. A combined strategy targeting CXCR-4 and PD-L1 might have clinical prospects for GC patients.