Abstract 3793: Cell-based, high-throughput screen for small molecule inducers of cell death in HPV-associated head and neck cancers

Abstract

Abstract High-risk human papillomavirus (HPV) is an oncogenic virus associated with 90% of cervical cancers, over 60% of oropharyngeal carcinoma cases and over 90% of anogenital cancers. Although HPV-positive cancers are molecularly, clinically and epidemiologically distinct from HPV-negative cancers, there are no specific or targeted therapies for HPV-positive cancers. In order to identify small molecule inhibitors that target HPV-positive cancers, we performed a high throughput drug screen on 24 cervical cancer and head and neck squamous cell carcinoma (HNSCC) cell lines (12 HPV-positive and 12 HPV-negative) to determine if these cell lines display differential sensitivity based on HPV status. HPV-positive cell lines with doubling times of less than 72 hours were selected for the screen. Unsupervised clustering of HNSCC cell lines based on protein expression levels obtained from reverse phase protein array (RPPA) was used to select matched HPV-negative cell lines by Spearman's rank-order correlation. Cytotoxic chemotherapeutics and agents targeting a broad range of processes including cell cycle control and DNA damage response were obtained from commercial vendors and academic collaborators. Drug sensitivity was measured by using nuclear staining to monitor cell death and proliferation after 72h of treatment. The screen of 1062 unique compounds at 6 different concentrations (0-3μM) in 24 cell lines represents 25,448 cell line – drug interactions. To ensure the robustness and reproducibility of the screen, the Z-factor and standard deviation for biological replicates were calculated. A Z-factor greater 0.5 was considered acceptable and the mean standard deviation across all drugs for each cell line was 0.06. Drug sensitivity was determined by calculating IC50 and area under the curve (AUC) values. Overall, HPV-positive HNSCC cell lines showed greater sensitivity to 13 drugs from different classes. Particularly, HPV-positive HNSCC cells were more sensitive to p38 MAPK and B-Raf inhibitors including LY2228820 (p < 0.01), regorafenib (p < 0.01), sorafenib (p < 0.05) and SB590885 (p < 0.05). On the other hand, HPV-negative HNSCC lines showed increased sensitivity to 30 drugs among these, palbociclib (p < 0.01), a CDK 4/6 inhibitor, and ryuvidine (p <0.05) which is reported to inhibit CDK 4. We are currently in the process of performing mechanistic studies and identifying genomic characteristics that influence sensitivity to B-Raf and p38 MAPK inhibitors in HPV-associated cancers using the genomic analyses and drug sensitivity data. Given the difference in clinical outcomes based on HPV status, any validated chemical-genomic interactions we discover will provide strong support for HPV-based treatment plans that may improve efficacy, allow for dose de-escalation and prevent permanent toxicity in patients. Citation Format: Nene N. Kalu, Tuhina Mazumdar, Pan Tong, Li Shen, Jing Wang, Lauren Averett Byers, Faye M. Johnson. Cell-based, high-throughput screen for small molecule inducers of cell death in HPV-associated head and neck cancers. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3793.