Abstract B12: HPV-positive tumor cell lines exhibit major alterations in Toll-like receptor pathways and depend on HMGB1 expression

Abstract

Abstract Cervical cancer is one of the leading causes of cancer death in women worldwide. Persistent infection with high-risk human papillomavirus (HPV) types is the main risk factor for the development of cervical cancer precursor lesions and is usually characterized by innate immune system evasion. The innate immune system is the first line of defense against pathogens and homeostatic changes. Toll-like receptors (TLR) are a family of membrane proteins that actively participate in this process by recognizing molecular patterns derived from pathogens and from cellular danger signals. Alterations in TLR expression and activation may be important for the control of HPV infections and could play a role in the progression of HPV-associated lesions and cancers. In the present study, we analyzed the expression of 84 genes involved in TLR signaling pathways in cervical cancer cell lines and primary human keratinocytes. We observed that 80% of the differentially expressed genes were downregulated in cervical cancer cell lines relative to normal keratinocytes. Major alterations were detected in genes coding for several TLR signaling proteins, including adaptor molecules MyD88 and SARM1, NFκB activation complex components such as Ube2N and TRAF6, and effector proteins such as HMGB1. Specifically, HMGB1, a protein related to stimulation of inflammation after TLR activation, showed increased expression levels in the HPV-positive cell lines HeLa and SiHa relative to normal keratinocytes. HMGB1 silencing also reduced cell viability, proliferation, and colony formation capacity of cervical cancer cell lines. In addition, silenced cervical cancer cell lines exhibited increased activated caspase-3 levels and hypodiploid cell population suggestive of apoptosis triggering. HPV infection may interfere with TLR pathways at different levels, resulting in the impairment of their activation and function and potentially leading to innate immune system evasion. Our results suggest that TLR pathway proteins such as TLR4, SARM1, and HMGB1 may play other roles related to tumor development. In conclusion, HMGB1 is a key factor in the survival of HPV-positive tumor cells, which warrants further studies to evaluate its potential as a therapeutic target or tumor biomarker. Citation Format: Mirian Galliote Morale, Walason da Silva Abjaude, Aline Montenegro da Silva, Luisa Lina Villa, Enrique Boccardo. HPV-positive tumor cell lines exhibit major alterations in Toll-like receptor pathways and depend on HMGB1 expression [abstract]. In: Proceedings of the AACR International Conference held in cooperation with the Latin American Cooperative Oncology Group (LACOG) on Translational Cancer Medicine; May 4-6, 2017; São Paulo, Brazil. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(1_Suppl):Abstract nr B12.