Abstract 1858: Rb deficient HPV+ HNSCC experienced enhanced sensitivity to aurora kinase inhibitors by altering the balance of MAD2 and TRIP13 levels
Authors: Ghosh Soma , Mazumdar Tuhina , Xu Wei , Powell Reid T. , Stephan Clifford , Shen Li , Pickering Curtis R. , Wang Jing , Johnson Faye M. 
Published: June 2022

Abstract
Human papilloma virus (HPV)-driven head and neck squamous cell carcinoma (HNSCC) is common in young patients (&lt;60 years). All patients experience either permanent toxicity from standard therapy or death from recurrent disease. To address this unmet need for more effective and less toxic therapy, we performed a high throughput drug screen comparing drug efficacy in HPV+ and HPV- cell lines. We tested the drug sensitivity of 864 unique drugs (0-3.1 µM) divided into 51 classes based on their targets in 33 squamous cancer cell lines using a parameter that is independent of cell division. Only one class of drugs, Aurora kinase inhibitors, was more effective in HPV+ than HPV- cell lines. To validate our screening results, we tested two Aurora kinase inhibitors (Alisertib, Barasertib) and observed significant cell death in HPV+ cells, but not in HPV- cells. Alisertib reduced tumor volume in HPV+ PDX mouse models without toxicity. To investigate the underlying mechanism, we compared the expression of ~300 proteins, using RPPA, to drug efficacy and validated the results using immunoblotting. The expression of Rb, pRb(S807/811), and p16 correlated with drug sensitivity. To establish role for Rb, we used a bidirectional approach to manipulate RB1. Reduction in RB1 levels using either shRNA or stable E7 overexpression in HPV- cells resulted in increased Alisertib-induced apoptosis. We also used siRNA to knock down E7 expression in two HPV+ cell lines which resulted in elevated levels of Rb, thereby rescuing the cells from Alisertib-induced apoptosis. Studies have shown Rb-deficient cells have elevated levels of the mitotic-checkpoint protein MAD2, that may impact cell fitness. To test the role of MAD2, we depleted the levels of MAD2 and observed diminishing levels of cyclin B1 accumulation and reduced Alisertib-induced apoptosis. Additionally, we altered the activated levels of MAD2 protein by overexpression of TRIP13 that resulted in partially rescuing cells from undergoing Alisertib-induced apoptosis. These results indicate that Rb- deficient MAD2 overexpressing cells require a finely tuned balance of MAD2 and TRIP13 levels for their mitotic exit. Furthermore, we observed combined inhibition of TRIP13 with Aurora A led to more apoptosis in Rb-deficient cells than the single agents. Our results demonstrate that Rb-deficient cancers are sensitive to Aurora A inhibition due to an imbalance between MAD2 and TRIP13. Based on the above finding, our present study shows that TRIP13 inhibition in combination with Aurora kinase inhibitors leads to more apoptosis and can pave a path for novel therapies in the management of HPV+ tumors.
Citation Format: Soma Ghosh, Tuhina Mazumdar, Wei Xu, Reid T. Powell, Clifford Stephan, Li Shen, Curtis R. Pickering, Jing Wang, Faye M. Johnson. Rb deficient HPV+ HNSCC experienced enhanced sensitivity to aurora kinase inhibitors by altering the balance of MAD2 and TRIP13 levels [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1858.