Abstract 1728: Single cell RNA-seq analysis reveals a role of pro-inflammatory tumor-associated macrophages in driving prostate cancer progression

Abstract

Abstract Genomic amplification and increased expression of C-MYC are found in high-grade intraepithelial neoplasm (HGPIN) and primary prostate adenocarcinoma. What role C-MYC plays in the initiation and progression of prostate cancer remains unclear. A genetically engineered mouse model with a high level of human C-MYC protein expression under a probasin promoter (Hi-Myc model) was developed that captures prostate cancer progression from hyperplasia at 6-week-old, to HGPIN at 3-6 month-old, and ultimately to invasive adenocarcinoma at 8-month-old. Applying single-cell RNA sequencing (scRNA-seq) technology, we have carefully studied the temporal transcriptional change in MYC-expressing tumor-initiating cells and the tumor-infiltrating immune cells to understand the cell-intrinsic and -extrinsic mechanisms by which C-MYC promotes the transition from HGPIN to invasive prostate cancer. We have identified a particular type of luminal cells, Prom1+ L1 cells, as the likely tumor initiating cells in the Hi-Myc model. The MYC-expressing L1 tumor initiating cells were more abundant and cycling more often in the invasive cancer at 8-month-old, compared to the pre-invasive stage. Interestingly, significant infiltration of novel M1-like tumor-associated macrophages (TAMs) correlated with the histologic tumor progression from HGPIN to invasive cancer. Targeting TAMs with anti-CSF1R antibody delayed prostate cancer progression and invasion, which appears to be independent of CD8 T-cells. Mechanistically, TAMs expressed a high level of IL-1b, which stimulated Hi-Myc prostate cell proliferation in an organoid co-culture system. More importantly, depleting IL-1b with a neutralizing antibody slowed prostate cancer progression in Hi-Myc mice. Lastly, we found that increased macrophage gene expression was associated with higher Gleason scores and worse disease-free survival in a TCGA clinical patient cohort. In summary, we have identified a molecular mechanism involving pro-inflammatory TAMs and IL-1b in driving early prostate cancer progression in a MYC-driven prostate cancer model, opening a potential therapeutic avenue to target TAMs and pro-inflammatory cytokine in preventing early prostate cancer progression. Citation Format: Jimmy L. Zhao, Joseph Chan, Max Land, Perianne Smith, Anuradha Gopalan, Michael Haffner, Dana Pe'er, Charles Sawyers. Single cell RNA-seq analysis reveals a role of pro-inflammatory tumor-associated macrophages in driving prostate cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1728.