Abstract 4946: Comprehensive molecular profiling reveals distinct immunemicroenvironment subtypes of oropharyngeal cancers
Authors: Kim Min Hwan , Kim Jae-Hwan , Jung Dong Min , Choi Jae Woo , Heo Soo Jin , Pyo Kyoung-Ho , Hong Min Hee , Cho Byoung Chul , Kim Hye Ryun 
Published: August 2019

Abstract
Background The oropharyngeal cancer (OPC) constitutes a distinct clinical subset of head and neck squamous cell carcinoma with high prevalence of HPV-associated tumorigenesis. However, the relationship between tumor molecular types and immune microenvironment has not been systematically delineated in OPCs. In this study, we classified the OPCs into three different molecular subtypes regarding their immunological character by comprehensive molecular profiling by RNA-seq and multiplexed immunohistochemistry (IHC).
Methods The 37 surgically resected primary OPC tumors were analyzed, and the HPV status was evaluated by p16 IHC. The transcriptome profiling of tumors by RNA-seq classified OPCs into three molecular subtypes based on t-SNE plotting. The immune microenvironment of each subtype was investigated using VECTRA spectral imaging system in terms of CD8 T cell and macrophage infiltration patterns, as well as T cell exhaustion maker expressions. The 10 OPC patients treated with anti-PD-1/PD-L1 blockade were also classified into three subtypes and their therapy response was compared.
Results We divided OPCs into Immune-rich (IR), mesenchymal (MS), and classical (CL) subtypes by RNA-seq clustering analysis. All IR type tumors were HPV-positive, whereas most CL types (7 out of 8) were HPV-negative. MS type showed mixed HPV status (HPV-positive in 5/14). The IR type showed favorable prognosis compared with poor prognosis of CL type, and MS type showed intermediate survival outcome. The IR type tumors showed high enrichment of adaptive immune response, T cell exhaustion, and cell cycle gene signature implying their highly immunogenic properties. The multiplexed IHC confirmed plenty of PD-1+CD8 T cells and type I macrophages infiltrating tumor nest in IR types. The MS type was characterized by upregulation of muscle, extracellular matrix, and TGF-β signatures with scant CD8 T cell signature expression. The IHC analysis of MS type showed exclusion of CD8 T cells from tumor nest that might be related to their high TGF-β-response signature (TBRS) score. CL types were related to high xenobiotic catabolism signatures, and showed low level of CD8 T cell infiltrations with focal CD73 expression. Among 10 OPC patients with anti-PD-1/PD-L1 blockade treatment, the IR type patients showed durable therapy response (3 of 4 patients), whereas CL type patients showed early progression on the treatment (3 of 4 patients).
Conclusions Our comprehensive analysis reveals that OPCs can be classified into three distinct subtypes based on their immune microenvironment properties. The three molecular subtypes showed distinct therapy response on anti-PD-1/PD-L1 blockade. These findings are pertinent to develop predictive markers on immunotherapy and to design combination immunotherapy strategies in OPC patients.
Citation Format: Min Hwan Kim, Jae-Hwan Kim, Dong Min Jung, Jae Woo Choi, Soo Jin Heo, Kyoung-Ho Pyo, Min Hee Hong, Byoung Chul Cho, Hye Ryun Kim. Comprehensive molecular profiling reveals distinct immunemicroenvironment subtypes of oropharyngeal cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4946.