Lactoferricin B reverses cisplatin resistance in head and neck squamous cell carcinoma cells through targeting PD‐L1

Head and neck squamous cell carcinoma (HNSCC) ranks among the top most common cancers with a poor prognosis. The mechanism of chemoresistance is still not well known. This study is to investigate the programmed death‐ligand 1 (PD‐L1) expression in HNSCC, and test the effect of lactoferricin B (LfcinB) on chemoresistance and its mechanism. We analyzed 510 HNSCC patients in TCGA database and investigated how CD274 expression was related to patient prognosis. PD‐L1 was verified from HNSCC samples at local hospital with immunohistochemistry. PD‐L1 expression in the acquired cisplatin‐resistant HNSCC cells was examined by PCR and WB in order to test PD‐L1‐induced chemoresistance. LfcinB inoculation in cisplatin‐resistant HNSCC cells and in the nude mice was introduced to test the effect of LfcinB on targeting cisplatin resistance and its mechanism. High CD274 mRNA (>125 FPKM) from TCGA database had a significantly reduced 5‐year survival rate, and a lower 5‐year survival rate in the chemotherapy and radiotherapy‐treated patients (P < .05). PD‐L1 overexpression was further supported from analysis of 40 HNSCC specimens. PD‐L1 and IL‐6 in the established cisplatin‐resistant HNSCC cells were shown significantly higher (P < .05). IL‐6 and PD‐L1 expression were partially inhibited by the anti‐IL‐6/STAT3 antibody. LfcinB displayed a direct cytotoxic effect on cisplatin‐resistant HNSCC cells and HNSCC xenografts of cisplatin‐resistant cells in the nude mice displayed significant reduction in tumor volume after LfcinB injection (P < .05). Besides, the increase of IL‐6 and PD‐L1 in cisplatin‐resistant HNSCC cells was abolished in vitro by LfcinB (P < .05). PD‐L1 expression in HNSCC cells correlates with poor prognosis and chemoresistance, and LfcinB might provide therapeutic potential in HNSCC patients through modulating IL‐6 and PD‐L1.