Odontogenic tumors are lesions derived from the elements of the tooth-forming apparatus and are found exclusively within the jawbones. These development-associated tumors （ⅰ） often occur in juveniles and exhibit considerable histological variation, （ⅱ） are usually intraosseous tumors but contain various amounts of epithelial components that interact with the specific microenvironment, and （ⅲ） are generally benign, although several tumors show locally invasive behavior with a high risk of recurrence. This report gives a contemporary outline of our current understanding of the molecular and genetic alterations associated with the development and progression of odontogenic tumors, including cell death-related factors, a cell immortalization factor, cell cycle regulators, growth factors, regulators of tooth development, hard tissue-related proteins, cell adhesion molecules, matrix-degrading proteinases, angiogenic factors, and osteolytic cytokines. It is hoped that a better understanding of related molecular mechanisms will help to predict the course of odontogenic tumors and lead to the development of new therapeutic concepts for their management.
Recurrent and/or metastatic head and neck squamous cell carcinoma（R/M HNSCC） is a devastating malignancy with a poor prognosis. According to recent clinical studies, tumor growth can be effectively reduced and survival can be improved by blocking the programmed death receptor 1（PD-1） pathway. However, anti-PD-1 treatment is beneficial only for certain patients. Therefore, the mechanisms controlling PD-L1 expression warrant further investigation in order to provide a better understanding of the efficacy of predicting and optimizing anti-PD-1 therapy, alone or in combination. In this study, PD-L1 protein extracted from the cell membrane was found to be downregulated in OSC-20 cells compared with OSC-19 cells, despite a higher PD-L1 expression in the total cell lysate of the OSC-20 compared with the OSC-19 cells. Several matrix metalloproteinases（MMPs） were found to be upregulated in HNSCC; in particular, MMP-7 and -13 were upregulated in the OSC-20 compared with the OSC-19 cells. Purified PD-L1 was degraded by recombinant MMP-13 and -7. The expression of PD-L1 was significantly restored by a specific inhibitor of MMP-13, which suggested the involvement of MMP-13 in the shedding/cleavage of PD-L1 in the OSC-20 cells. Among the anti-cancer drugs conventionally used in the treatment of patients with HNSCC, paclitaxel increased MMP-13 expression in R/M HNSCC cells（HOC313 cells）. These results suggest that the shedding/cleavage of PD-L1 by MMP-13 is one of the mechanisms behind the protective effect against invasion and metastasis. Thus, MMP-13 has potential value as a marker predictive of the decreased efficacy of anti-PD-1 therapy.
Magnifying endoscopy with narrow band imaging （NBI） is a spectrally selective reflectance imaging technique that is used clinically for enhancing visualization of superficial vasculature. NBI easily detects superficial neoplastic lesions as clearly demarcated brownish areas. We report two cases of auxiliary diagnosis of tongue squamous cell carcinoma （SCC） using NBI endoscopy. Case 1：The first patient was a 68-year-old man who complained of discomfort in the left lingual edge. NBI indicated irregular vessels at the left tongue edge. A biopsy specimen from the area revealed carcinoma in situ. We resected the lesion based on the demarcation line determined by NBI．The histopathological diagnosis was SCC. Case 2：The second patient was a 77-year-old woman who complained of pain in the right lingual edge. NBI indicated irregular vessels bilaterally in the lingual edges. A biopsy specimen from the area revealed carcinoma in situ in the right side and SCC in the left side. We resected the lesions assisted by NBI. The histopathological diagnosis was carcinoma in situ in the right side and SCC in the left side. Postoperatively, we compared the NBI findings with those from histopathology and found them to be correlated. Thus, NBI may be useful for detecting disorders of the oral mucosa and determining the demarcation line of early-stage oral cancers. However, further verification of its future potential is necessary.