Abstract 225: Tumor-infiltrating CD8-positive T-lymphocytes in tubo-ovarian high-grade serous cancer are associated with multiple germline variants in 22q12.1 in a genome-wide association analysis

Abstract

Abstract Tubo-ovarian high-grade serous cancer (HGSC) is the most common histotype of epithelial ovarian cancer (70%-80%) and the leading cause of death from gynecological malignancy. Novel monoclonal antibody and adoptive cell transfer immunotherapies have found success in cancer in the past five years; however success in HGSC treatment has been elusive thus far. We have recently shown that CD8+ T-lymphocytes infiltrating the tumor proper (TILs) associate in a dose response manner with longer patient survival time regardless of age, stage or residual disease. As understanding host factors associated with this clinically relevant tumor phenotype will contribute to the development of targeted therapies, we sought to identify germline genetic factors associated with CD8+ TIL levels in HGSC. We performed a germline genome-wide association study (GWAS) of CD8+ TILs using 1204 HGSC patients of European ancestry from twelve studies with centralized genotyping, immunohistochemistry, and harmonization of clinical data. Germline genotypes were assayed using the Illumina Infinium OncoArray Beadchip and were imputed to over 11.4 million variants based on the 1000 Genomes Project reference panel. CD8 immunohistochemistry was performed on tissue microarrays using the Leica Bond Rx stainer and scored into four levels of CD8+ TILs per x400 magnification of a 0.55-mm diameter field for each tumor hotspot: none (no CD8+ TILs), low (1-2 CD8+ TILs), moderate (3-19 CD8+ TILs), high (20 or more CD8+ TILs). GWAS used multinomial regression modelling of these four CD8+ TIL levels adjusted for study site, age, and European ancestry principal components. On the average, CD8+ TIL levels were 18%, 19%, 44% and 18% for none, low, moderate and high levels, respectively. As expected, CD8+ TIL levels associated with overall survival time (p < 2.6x10-8), and CD8+ TIL levels and age at diagnosis were similarly distributed across study sites. We identified a region on chromosome 22 with multiple, correlated variants (MAF > 20%) associated with CD8+ TIL levels at p-value < 2.0x10-5. The most statistically significant variant was an indel (rs557925408) located in the an intron of the MYO18B gene (Myosin XVIIIB, p-value < 8.7x10-6). Each copy of this variant associated with a reduced extent of CD8+ TIL infiltration (OR low v none = 0.92; OR moderate v none = 0.61). An independent set of 1200 OncoArray genotyped HGSC cases are undergoing CD8+ TIL scoring in December 2017 and will be included in final genome-wide analysis. This will provide improved statistical power and enable consideration of additional genetic models (e.g., linear trend tests). Comprehensive integrative analysis of germline, tumor, and clinical features provides a model for clinical molecular epidemiology studies and will be key to increasing our understanding of this important HGSC immunophenotype. Citation Format: Yanina Natanzon, Martin Köbel, Stacey J. Winham, Sebastian M. Armasu, Bryan M. McCauley, Robert A. Vierkant, Julie M. Cunningham, David Bowtell, Ian G. Campbell, Jenny Chang-Claude, Anna deFazio, Peter A. Fasching, Mark T. Goodman, Beth Y. Karlan, Francesmary Modugno, Kirsten B. Moysich, Roberta B. Ness, Weiva Sieh, Paul D. Pharoah, Susan J. Ramus, Ellen L. Goode. Tumor-infiltrating CD8-positive T-lymphocytes in tubo-ovarian high-grade serous cancer are associated with multiple germline variants in 22q12.1 in a genome-wide association analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 225.