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Abstract Background Aberrant Notch signaling pathway has been related with the tumorigenesis in head and neck region, involving oral cavity. Here, we report the correlation between mutations in the Notch signaling pathway and CD8+ T‐cell infiltration via PD‐L1, which lead to enhanced antitumor immunity and may target for immune‐checkpoint inhibitors (ICIs) therapy. Methods This retrospective study analyzed the results of immunohistochemical staining for PD‐L1 and CD8+ T‐cell infiltration in 10 patients and whole‐exome sequencing (WES) was conducted on five of these patients to identify frequently mutated genes. Results Four of 10 patients were positive for PD‐L1 and CD8+ T. By analyzing WES in three of these four patients, we notably identified the mutations of NOTCH1, FBXW7, and noncoding RNA intronic mutation in NOTCH2NLR in two of these three patients. This study may enable better selection of ICI therapy with CD8+ T‐cell infiltration via PD‐L1 expression for oral squamous cell carcinoma patients with mutations in Notch signaling pathway.

Abstract Background The CXCL12/CXCR4 axis plays a pivotal role in the progression of various malignancies, including oral squamous cell carcinoma (OSCC). In this study, we aimed to clarify the biological and clinical significance of CXCL12 in the tumor microenvironment of OSCCs. Methods Publicly available single‐cell RNA‐sequencing (RNA‐seq) datasets were used to analyze CXCL12 expression in head and neck squamous cell carcinomas (HNSCC). Immunohistochemical analysis of CXCL12, α‐smooth muscle antigen (α‐SMA), fibroblast activation protein (FAP) and CD8 was performed in a series of 47 surgically resected primary tongue OSCCs. Human skeletal muscle cells were co‐cultured with or without OSCC cells, after which CXCL12 expression was analyzed using quantitative reverse‐transcription PCR. Results Analysis of the RNA‐seq data suggested CXCL12 is abundantly expressed in stromal cells within HNSCC tissue. Immunohistochemical analysis showed that in grade 1 primary OSCCs, CXCL12 is expressed in both tumor cells and muscle cells. By contrast, grade 3 tumors were characterized by disruption of muscle structure and reduced CXCL12 expression. Quantitative analysis of CXCL12‐positive areas within tumors revealed that reduced CXCL12 expression correlated with poorer overall survival. Levels of CXCL12 expression tended to inversely correlate α‐SMA expression and positively correlate with infiltration by CD8+ lymphocytes, though these relations did not reach statistical significance. CXCL12 was significantly upregulated in muscle cells co‐cultured with OSCC cells. Conclusion Our results suggest that tongue OSCC cells activate CXCL12 expression in muscle cells, which may contribute to tumor progression. However, CXCL12 is reduced in advanced OSCCs due to muscle tissue destruction.