Sequential administration of pemetrexed and cisplatin reprograms tumor immune microenvironment and potentiates PD-1/PD-L1 treatment in a lung cancer model

This article aimed to investigate the effects of the administration method of pemetrexed and cisplatin on the efficacy and safety of treating non-small cell lung cancer (NSCLC) and the intrinsic molecular mechanism. Subcutaneous injection of A549 cells into BALB/C nude mice was used to explore the efficacy of different administration methods of pemetrexed and cisplatin in vivo. Immunogenic cell death (ICD) was evaluated by ATP secretion, ecto-CALR expression, and high mobility group protein 1 release. Western blot, qRT-PCR, and immunohistochemical staining were applied to detect the expression of apoptosis, cell cycle, and stimulator of interferon genes (STING) pathway-related markers. Immune microenvironment was evaluated by secretion of cytokines, infiltration of CD8+ T cells, and expression of programmed death molecular ligand-1 (PD-L1). Sequential treatment with pemetrexed and cisplatin inhibited A549 cell-driven tumor formation in nude mice and regulated the expression of apoptosis and cell cycle-related genes. STING pathway and ICD were further activated by sequential treatment with pemetrexed and cisplatin. This sequential administration method increased the levels of interferon β, tumor necrosis factor α, interleukin 12, and C-X-C motif chemokine ligand 10, enhanced the infiltration of CD8+ T cells, and upregulated the expression of PD-L1. Sequential administration of pemetrexed and cisplatin in the treatment of mouse NSCLC model may have a better effect than combination of drugs, providing theoretical basis and potential guidance for clinical medication.