The interplay of hypoxia, inflammation, and microbiota as indicators of malignant transformation in oral potentially malignant disorders

Oral Potentially Malignant Disorders (OPMDs), such as leukoplakia, erythroplakia, proliferative verrucous leukoplakia, and oral submucous fibrosis, carry a risk of malignant transformation, with reported rates ranging from 2.6 % to 7.9 %. Higher risks are observed in specific subtypes, such as erythroplakia and proliferative verrucous leukoplakia. Although clinical factors like lesion size, dysplasia, and patient demographics have been studied, none have consistently proven reliable for predicting malignancy. This study conducted a retrospective review of OPMD patients treated at the University of Brescia from 1996 to 2019, including various dysplasia grades and extensive clinical data. Gene expression profiling was performed on these samples to explore molecular stratification based on a six-subtype classification developed for Head and Neck Squamous Cell Carcinoma (HNSCC). Additionally, intratumor microbiota content was analyzed to assess its association with OPMD transformation risk. The findings highlighted the aggressive nature of the Cl3-Hypoxia molecular subtype, with a median malignant transformation time of 30.1 months. Considering the role of hypoxia in modulating tumor-associated inflammatory cell functions, we also assessed two inflammatory gene signatures, demonstrating their significant association with OPMDs and correlating with tissue-resident microbiota. This study provides compelling evidence of microbial-host interactions in the malignant transformation of OPMDs, with specific molecular features, particularly hypoxia-related pathways, linked to increased malignancy risk. These results suggest potential biomarkers for prognosis and offer therapeutic strategies targeting the tumor microenvironment and microbiota to mitigate malignant progression in high-risk OPMD patients.