DEfiNING PATHOLOGIC AND MOLECULAR CHARACTERISTICS OF TONGUE LESIONS IN THE 4NQO MOUSE CARCINOGENESIS MODEL

Oral cancer patients experience function-related pain, whereas patients with oral epithelial dysplasia rarely report pain. To study pain and model its onset with progression to cancer, we use the 4-nitroquinoline-1-oxide (4NQO) rodent carcinogenesis model that recapitulates oral cancer progression. Consensus is lacking regarding histopathologic definition of 4NQO-induced lesions. Objective Our objective was to determine histopathologic and genomic alterations of 4NQO-induced tongue lesions to better model human oral cancer pain and improve understanding of cancer progression and evolution. We offered C57BL/6 mice 4NQO or vehicle in the drinking water for 16 weeks. At 32+ weeks, animals were sacrificed. Fifty 5 μm longitudinal sections were obtained from formalin fixed paraffin embedded tongues. Every tenth section was stained with H&E and examined for lesions. Findings Vehicle treated animals lacked lesions (n=5). Tongues from 4NQO treated animals (n=9) bore multiple lesions, including field changes, dysplasia, papillomas, carcinoma in situ (CIS) and invasive cancers distinguished by depth of invasion – superficially invasive ( 2 mm). Hierarchical clustering (Euclidean distance, Ward linkage) according to presence of lesions (CIS, papilloma, invasive cancer, deeply invasive cancer) revealed three clusters, each with three animals. Significantly greater numbers of lesions were present in Cluster 3 tongues compared to Clusters 1 and 2 (p=0.03 for both comparisons, Ordinary one-way ANOVA, Holm-Sidak multiple comparisons test). Cluster 1 comprised tongues with the deeply invasive cancers, which also showed aggressive features, including perineural invasion. Significantly fewer papillary lesions were present compared to Clusters 2 and 3 (p=0.004 and p=0.0002, respectively, two-way ANOVA, Tukey's multiple comparisons test). Conclusions Our data suggest possible division of the 4NQO model into subtypes. Lesion associated genomic copy number alterations and mutations are being determined to identify molecular and evolutionary relationships among lesion types and possible model subtypes.