The effects of Co-exposure of tobacco smoke with Dibenzo[a,l]pyrene diol epoxide on molecular targets and immune cells in the mouse oral cavity

Tobacco smoking (TS) is an established etiological factor in the development of head and neck squamous cell carcinoma (HNSCC). We previously developed a mouse model using a select tobacco carcinogen, dibenzo[a,l]pyrene (DB[a,l]P, and its ultimate carcinogenic metabolite diol-epoxide (DB[a,l]PDE) to induce oral squamous cell carcinoma (OSCC) in mice; the molecular characteristics and histological changes observed in the mouse oral cavity mimic those found in human HNSCC. In the present study, using our mouse model, we examined for the first time the co-carcinogenic effects of TS with DB[a,l]PDE on DNA damage, histology, molecular targets, and immune cell regulation. We observed a non-significant increase of the levels of DB[a,l]PDE-DNA adduct in the oral cavity of mice exposed to TS as compared to those exposed to compressed air. Histologically, we observed significant increases in epithelial hyperplasia and epithelial single cell necrosis in TS treated mice. TS significantly enhanced protein expression of NF-κB and Ki67 while the enhancement of COX-2 did not reach significance but p53 expression was significantly decreased. We analyzed immune cell regulation in both spleen and tongue (target organ). No significant changes were observed in the spleen; however, in the tongue, we observed a significantly reduced frequency of CD3+T cells that included reductions of both CD4 and CD8 T cells and a corresponding increase was observed for multiple myeloid cell populations. While preliminary, our results offer the foundation for future research using this mouse model to explore the impact of co-carcinogens/tumor promotors other than TS on critical factors involved in the development of HNSCC.