Abstract B032: Proteomic analysis reveals alterations in apoptotic signaling machinery in HPV-associated cancers and identifies BRD4 and BCL2 as potential therapeutic targets in HPV-positive HNSCCs

Abstract

Abstract Human papillomaviruses (HPV) are among the most common viral causes of cancer; infections account for a majority of cervical squamous cell carcinomas and endocervical adenocarcinomas (CESCs) and oropharyngeal squamous cell carcinomas. HPV-positive cancers demonstrate well-established differences in histopathology and clinical outcome compared to HPV-negative cancers, yet the biological mechanisms underlying these differences are not fully characterized. In this analysis, we highlight key pathways and candidate targets differentially expressed in HPV-positive head and neck squamous cell carcinomas (HNSCCs) and CESCs and investigate potential contributors to these differences, including microRNA (miRNA). Methods: We conducted an analysis of mRNA and protein expression in HPV-positive and HPV-negative HNSCCs and CESCs from the Cancer Genome Atlas (TCGA) to investigate the potential pathways that are differentially expressed between HPV-positive and HPV-negative cancers. mRNA levels were measured by RNA Seq and protein levels by reverse phase protein arrays (RPPA). We also analyzed miRNA levels for both HNSCCs and CESCs, then used TargetScan to identify potential targets for miRNA that were differentially expressed. Results: Proteins involved in extracellular matrix (ECM) adherence including Paxillin and Fibronectin were higher in HPV-negative HNSCCs and CESCs (Paxillin’s p-value= 0.04 for CESCs and p-value<.01 for HNSCCs; Fibronectin’s p=.04 for CESCS and p<.01 for HNSCCs). In addition, Rb, a cell-cycle protein which is known to be degraded by HPV’s E7 protein, was lower in HPV-positive HNSCCs and CESCs (p=.015 for CESCs and p<.01 for HNSCCs). Consistent with its role as a marker for HPV-positive cancers, cell cycle regulator P16INK4A was also notably elevated in HPV+ HNSCCs and CESCs (p<.01). Several genes involved in apoptotic pathways were higher in HPV+ HNSCCs and CESCs, including BIM (p<.01 for CESCs and for HNSCCs) and cleaved caspase 7 (p<.01 for CESCs and for HNSCCs). BRD4 was also higher in HPV-positive HNSCCs (p<.01). Multiple miRNA predicted to target BIM were also significantly lower in HPV+ HNSCCs and/or CESCs . For instance, Mir-891a is lower in HPV+ CESCs (p<.01, fold change=3.11) and potentially targets BIM (total context score=-.61). mir-3200, which potentially targets Lck, is lower in HPV+ CESCs (p<.01). Conclusions: Analyses of protein expression in HPV+ HNSCCs and CESCs reveal differences in HPV-induced and non-HPV-induced cancers, including differences in pathways related to apoptosis, extracellular matrix adherence, cell-cycle regulation, and immune markers. This includes increased expression of potentially druggable targets such as BIM and BRD4. miRNA may contribute to some of the differential expression of these pathways. Citation Format: Claudia Heymach, Robert Cardnell, Lixia Diao, Jing Wang, Kwok-Shing Ng, Lauren Byers. Proteomic analysis reveals alterations in apoptotic signaling machinery in HPV-associated cancers and identifies BRD4 and BCL2 as potential therapeutic targets in HPV-positive HNSCCs [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr B032. doi:10.1158/1535-7163.TARG-19-B032