Abstract B036: Immune cell profiling of human prostate tumors identifies a protective and pathological role for intratumoral mast cells in the development of biochemical recurrence and metastasis
Authors: Schafer Cara , Jiang Jiji , Elsamanoudi Sally , Nousome Darryl , Young Denise , Song Yingjie , Sesterhenn Isabell , Chesnut Gregory , Tan Shyh-Han 
Published: June 2023

Abstract
Background: Immunobiological factors may, in part, contribute to racial disparities in prostate cancer (PCa), the second leading cause of cancer-related death for US men. African American (AA) men face a greater risk of developing PCa and having a poorer outcome of this disease, compared to Caucasian American (CA) men. The goal of this study is to identify immune-specific differences influencing PCa health disparity as well as PCa progression. Methods: Ex vivo tumor biopsies were obtained following radical prostatectomy (RP) from 51 treatment-naïve patients (26 AA, 25 CA) under approved IRB protocols. Total RNA from fresh frozen tissue was isolated and amplified by PCR using NanoString multiplexed target enrichment protocols. We evaluated differences in resulting transcripts by self-reported race, pathology, and other clinical and pathologic features. Relative abundances of immune cell subsets were determined using computational methods, including previously published deconvolution algorithms, to estimate cellular content. Results: We identified differentially expressed genes between AA and CA tumors that are characterized by genes regulating Natural Killer (NK) cell function and Wnt signaling cancer pathways. Among the entire cohort, high expression of two of these differentially expressed genes, DVL2 and MAP3K5, were associated with worse biochemical recurrence (BCR)-free and metastasis-free survival. No difference in immune cell abundance was observed by self-reported race. Strikingly, among the entire cohort, low abundance of intratumoral mast cells was also associated with worse PCa pathology and poorer BCR-free and metastasis-free survival. Conclusions: Using a race-matched military cohort, we found that AA and CA tumors differ in the expression levels of Wnt and NK signaling-related pathways, yet cellular estimations of immune abundance did not significantly differ. Remarkably, the level of mast cell abundance within tumors at time of RP may be protective and prolong BCR-free and metastasis-free survival of patients. These types of in-depth immune profiling assessments have the potential to guide precision medicine and treatment decisions in the clinic. Disclaimer: The contents of this publication are the sole responsibility of the author(s) and do not necessarily reflect the views, opinions or policies of Uniformed Services University of the Health Sciences (USUHS), The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., the Department of Defense (DoD), the Departments of the Army, Navy, or Air Force. Mention of trade names, commercial products, or organizations does not imply endorsement by the U.S. Government.
Citation Format: Cara Schafer, Jiji Jiang, Sally Elsamanoudi, Darryl Nousome, Denise Young, Yingjie Song, Isabell Sesterhenn, Gregory Chesnut, Shyh-Han Tan. Immune cell profiling of human prostate tumors identifies a protective and pathological role for intratumoral mast cells in the development of biochemical recurrence and metastasis [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr B036.