Abstract 2392: Genomic and immune heterogeneity in synchronous melanoma metastases is associated with differential tumor growth and response to therapy
Authors: Reuben Alexandre , Spencer Christine N. , Prieto Peter A. , Miller John P. , Mao Xizeng , Chen Wei-Shen , Cheung Hannah , Jiang Hong , Haymaker Cara , Petaccia De Macedo Mariana , Garber Haven R. , Chen Pei-Ling , Gopalakrishnan Vancheswaran , Austin-Breneman Jacob , Hudgens Courtney W. , Roszik Jason , Hwu Patrick , Woodman Scott E. , Chin Lynda , Davies Michael A. , Amaria Rodabe N. , Patel Sapna P. , Lazar Alexander J. , Tetzlaff Michael T. , Dwyer Karen C. , Wistuba Ignacio I. , Sharma Padmanee , Allison James P. , Zhang Jianhua , Futreal Andrew , Cooper Zachary A. , Wargo Jennifer A. 
Published: July 2016

Abstract
There have been significant advances in the treatment of metastatic melanoma through targeted and immunotherapy, however a significant proportion of patients still progress on these regimens with many experiencing mixed responses. Intense research efforts to better understand resistance are underway, and multiple molecular resistance mechanisms to targeted therapy have been identified. The appreciation of genetic heterogeneity as a contributor to resistance to therapy has grown, though immune heterogeneity has been poorly characterized. The goal of the present study is to better understand the molecular and immune heterogeneity in synchronous melanoma metastases at the time of disease progression. In this study, we prospectively evaluated 32 tumors from 15 patients who were treatment-naïve (n = 4), or had received prior targeted (n = 4) or immunotherapy (n = 7). Whole exome sequencing demonstrated between 4-41% of non-synonymous exonic mutations (NSEM) were restricted to individual tumors within a patient. Deep profiling of infiltrating immune cell subsets by flow cytometry and immunohistochemistry analyses confirmed the immune infiltrate between synchronous metastases to be highly heterogeneous, specifically in regards to CD4 and CD8 T lymphocytes. In aggregate, 92% of these T cell clones were unique to distinct tumors within the same patient, with limited overlap with clones detected in the blood. NetMHC3.4 neoantigen prediction demonstrated a large fraction of predicted neoantigens were restricted to individual tumors, with over 10% of these presenting extremely high predicted affinity. Importantly, analysis of RECIST measurements of individual lesions within the same patient suggested this molecular and immune heterogeneity could contribute to differential tumor growth and response to therapy within the same patient. This has important clinical implications, and suggests a single tumor biopsy may not be sufficiently representative of the molecular and immune landscape of multiple tumors within the same individual.
Citation Format: Alexandre Reuben, Christine N. Spencer, Peter A. Prieto, John P. Miller, Xizeng Mao, Wei-Shen Chen, Hannah Cheung, Hong Jiang, Cara Haymaker, Mariana Petaccia De Macedo, Haven R. Garber, Pei-Ling Chen, Vancheswaran Gopalakrishnan, Jacob Austin-Breneman, Courtney W. Hudgens, Jason Roszik, Patrick Hwu, Scott E. Woodman, Lynda Chin, Michael A. Davies, Rodabe N. Amaria, Sapna P. Patel, Alexander J. Lazar, Michael T. Tetzlaff, Karen C. Dwyer, Ignacio I. Wistuba, Padmanee Sharma, James P. Allison, Jianhua Zhang, Andrew Futreal, Zachary A. Cooper, Jennifer A. Wargo. Genomic and immune heterogeneity in synchronous melanoma metastases is associated with differential tumor growth and response to therapy. [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 2392.