Abstract 1818: ZEB1 expression is associated with the PTEN loss and TMPRSS2 ERG fusion immune evasion phenotype in prostate cancer
Authors: Chaves Luiz P. , Caliari Andre L. , Melo Camila M. , Saggioro Fabiano P. , Squire Jeremy A. 
Published: July 2021

Abstract
Prostate cancer (PCa) is considered immunologically cold with a tumor microenvironment (TME) that evades effective immune responses. PTEN loss and TMPRSS2-ERG fusion are common somatic mutations in PCa and both alterations have recently been suggested to impact TME immune infiltration. Interestingly, both mutations are considered to play a role in epithelial to mesenchymal transition (EMT). ZEB1, a stemness and EMT driver has also been associated with immune evasion in different types of tumors. In this study, we investigated the role of ZEB1 in the immune TME of prostate cancer and the putative cooperation between ZEB1 expression, PTEN loss and TMPRSS2-ERG fusion. Immunohistochemistry for PTEN, ERG and ZEB1 were analyzed in 43 PCa cases collected after radical prostatectomy, correlation analysis of expression and immune cell abundance prediction were accessed using PCa expression data from TCGA (n=494). Correlation analysis between ZEB1 expression and 395 genes involved in immune response showed a positive correlation with ERG (r=0.1941, P&lt;0.0001), PTEN (r=0.3514, P&lt;0.0001), STAT3 (r=0.3129, P&lt;0.0001), BRCA2 (r=0.2381, P&lt;0.0001), CSF1R (r=0.6041, P&lt;0.0001), PDCD1 (r=0.2536, P&lt;0.0001), CD274 (r=0.4044, P&lt;0.0001), IL10 (r=0.3655, P&lt;0.0001), IL2 (r=0.1973, P&lt;0.0001), CCR7 (r=0.3325, P&lt;0.0001) and CXCL8 (r=0.424, P&lt;0.0001). When the cohort was dichotomized to compare fusion-positive to fusion-negative samples, ZEB1 correlation with ERG remained positive in fusion-negative samples (r=0.6422, P&lt;0.0001) but was negative (r=-0.2147, P=0.0022) in fusion-positive samples. Immune cell abundance prediction showed a positive correlation between ZEB1 and Tregs (r=0.35, P&lt;0.0001), monocytes (r=0.3874, P&lt;0.0001), dendritic cells (r=0.3934, P&lt;0.0001) and macrophages M1 (r=0.2176, P&lt;0.0001) and a negative correlation with plasma cells (r=-0.2003, P&lt;0.0001), CD8+ naïve T cells (r=-0.3565, P&lt;0.0001), th1 cells (r=-0.4562, P&lt;0.0001) and pro B-cells (r=-0.3539, P&lt;0.0001). Immunohistochemistry analysis showed a high expression of ZEB1 in non-neoplastic basal epithelium plus variable intensitiy of expression in adenocarcinomas and corroborated the correlation between ZEB1, PTEN and ERG expression levels. ZEB1 correlation with immunosuppressive cytokines and receptors such as CCR7, IL2, IL10, IL8 and PD-L1 provides evidence that ZEB1 and EMT may play an immune evasive role in PCa. The positive correlation with Tregs also supports this putative role. ZEB1 expression may indicate that stemness is associated with activation of downstream pathways modulated by PTEN and ERG. The correlation with BRCA2 may indicate an increased stemness-related role for this DNA damage response pathway. These observations, and our IHC findings, are in agreement with recently published data showing that ZEB1 is critical to a subset of basal stem cells in murine prostate samples.
Citation Format: Luiz P. Chaves, Andre L. Caliari, Camila M. Melo, Fabiano P. Saggioro, Jeremy A. Squire. ZEB1 expression is associated with the PTEN loss and TMPRSS2 ERG fusion immune evasion phenotype in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1818.