Analysis of the distribution of HEV by immunohistochemistry using a mouse oral squamous cell carcinoma model

Objective: The density of tumor-associated high endothelial venule (TA-HEV) correlates with a favorable prognosis in various tumors, including oral squamous cell carcinoma (OSCC). Despite the association of TA-HEVs with a better prognosis, their changes during tumor progression remain unclear. Therefore, this study aimed to examine these alterations in a mouse OSCC model. Methods: Mice were treated with water containing 4NQO to establish a mouse OSCC model. Immunohistochemical analyses were performed using CD31 and MECA 79 antibodies to evaluate TA-HEV alterations during tumor progression. Results: Tongue samples were histologically classified into untreated, normal, dysplasia, and carcinoma groups. During the dysplastic stage, the number of blood vessels increased, and pericyte coverage was reduced as the carcinoma developed. Moreover, HEVs were more abundant in the dysplasia and carcinoma groups, with an increased number of HEVs infiltrated with CD8⁺ T cells as the lesion progressed. The location and morphology of the HEVs changed during the transition from normal tissue to carcinoma, with the distribution of the TA-HEVs associated with the tumor growth patterns. Specifically, TA-HEVs were frequently found within the tumor in endophytic carcinomas, and at the tumor margins in exophytic carcinomas. Margin TA-HEVs correlated with a higher number of T cells than HEVs within the tumors. Conclusion: OSCC-associated HEVs increase in density with tumor progression, and margin TA-HEVs suggests a better anti-tumor prognosis compared with intra-TA-HEVs.