Abstract 427: A mouse model for studying oncogenesis of HPV-associated oropharyngeal cancer

The human papillomavirus (HPV) causes 70% of oropharyngeal cancers in the United States. While the molecular and cellular mechanisms and the stepwise progression of HPV-related cervical cancer have been well studied, oropharyngeal HPV carcinogenesis remains to be unraveled since an equivalent HPV premalignant stage has never been identified in clinical oropharyngeal tissues. In this study, a series of keratinocyte cell lines derived from the base of the tongue of C3H mice were established. These cells formed varying degrees of malignancy in the syngenetic mice and are used to study the biology of HPV-related oropharyngeal cancer in an immunocompetent host. Keratinocytes from the base of the tongue were isolated from C3H newborns and were subsequently retrovirally immortalized with TERT or HPV16 E6E7 oncoproteins, with or without oncogene H-ras. They are designated MOKT1 (TERT), MOKT1/H-ras (TERT/H-ras), MOKE2 (E6E7), or MOKE2/H-ras (E6E7/H-ras). These cells were injected in the masseter muscle of syngeneic mice and the developing lesions were harvested for histological analysis over a time course of 1 month. E6E7 transformed MOKE2 cells exhibited features of HPV associated cancer cells. We found that p63 and phosphorylated STAT3 were upregulated in MOKE2 cells in comparison to MOKT1 cells. MOKE2 cells obtained growth advantages with increased cell proliferation and decreased apoptosis. In addition, MOKE2 cells showed increased cell migration activity in wound healing assays. While all cell lines grew indefinitely in vitro, MOKT1 and MOKT1/H-ras failed to show any sign of malignancy when implanted in vivo. MOKE2 demonstrated features of malignancy, but the phenotype was transient. Host immunity does not appear to be the determining factor for suppressing tumor growth as MOKE2 regressing also occurred when implanted in immunodeficient NSG mice. Only MOKE2/H-ras cells were capable of progressing and establishing permanent cancer. Ourdata suggest that differentiation induced cell growth arrest may contribute to tumor regression and a second hit is required to overcome such arrest. The MOKE2 cells can be used in syngeneic mice to study secondary oncogenic factors in the development of HPV-related oropharyngeal cancer. Citation Format: Eva McGhee, Yi-Ling Lin, Jay Vadgama, Khadijah Lang, Judith Okoro, Victoria Vidal, Naomi Long, Mengtao Li. A mouse model for studying oncogenesis of HPV-associated oropharyngeal cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 427.