Abstract 1930: 4-nitroquinoline-1-oxide enhances induction of apoptosis preferentially in HPV positive head and neck squamous cell carcinoma cells

Abstract

Abstract Background: Tobacco use and human papillomavirus (HPV) infection are both strong contributors to the oncogenesis of head and neck squamous cell carcinoma (HNSCC). Despite HPV's causative role in HNSCC, it confers no statistically significant difference in mutational profile between HPV-associated HNSCC smokers and non-smokers. Our earlier preliminary data suggested that HPV positive (+) HNSCC cells have better activation of DNA repair proteins compared to HPV negative (-) HNSCC cells when treated with 4NQO, a mutagen and carcinogen which serves as a surrogate for tobacco exposure. This may partially explain HPV+ HNSCC's higher mutational resistance. In addition to increased DNA repair, HPV+ cells may also eliminate mutations through higher rates of apoptosis compared to HPV- cells. Hence, we wanted to test this hypothesis by analyzing the effects of 4NQO on apoptosis in HPV+ and HPV- HNSCC cells. Methods: NOK, NOK E6.E7, SCC40 (HPV-), SCC104 and UMSCC47 (HPV+) cells were treated with different concentrations of 4NQO (0, 0.1, and 0.2 ug/ml) for 24 and 48 hours. Untreated (control) and 4NQO treated cells were assessed for cell viability using MTT assay. Apoptotic cells were determined using Annexin-V FITC flow cytometry analysis, and Western blot was performed to check the apoptotic proteins for the afore-mentioned control and 4NQO treatments. Results: MTT assay showed decreased cell viability of NOK E6.E7, SCC47 and SCC104 cells in response to 4NQO treatment compared to relatively higher cell viability of SCC40 cells. Flow cytometry confirmed that HPV+ HNSCC cells are relatively more apoptotic compared to HPV- cells following 4NQO treatment at 24 and 48 hours. This is further supported by activation of pro-apoptotic proteins including p53, cleaved caspase 3, cleaved PARP, cleaved caspase 9, and p21 to a greater extent in HPV+ cells at different time points of 4NQO treatment using Western blot analysis. Conclusion: Our in-vitro data suggest HPV may stimulate a protective measure against smoking-induced mutations by increasing apoptosis before cells can contribute to the HNSCC mutational profile. Taken together, these data explain why HPV associated HNSCC have a better prognosis than HPV negative irrespective of smoking history. Citation Format: Gauri Shishodia, Alice Lee, Rhodee Ric Toledo, Emily Zimmerman, Xiaohua Rong, Adam Xiao, Lynn Harrison, Cherie Ann Nathan. 4-nitroquinoline-1-oxide enhances induction of apoptosis preferentially in HPV positive head and neck squamous cell carcinoma cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1930.