{
  "abstract": "Background Prostate cancer (PC) has historically been considered immunologically ‘cold’ due to low immune infiltration and a predominantly immunosuppressive tumor microenvironment (TME). 1 However, this understanding is largely based on immune profiling studies of metastatic, castration-resistant prostate cancer (mCRPC) and may not apply in earlier stages of disease.2–4 The composition and organization of the immune microenvironment in primary PC remains poorly defined, especially in relation to Gleason score, the gold standard of pathologic PC grading. We hypothesized that the localized PC immune microenvironment is more heterogeneous than previously appreciated, with distinct differences in immune composition and spatial organization between High Gleason (HG) and Low Gleason (LG) PC.Methods We analyzed 29 radical prostatectomy samples, comprising 15 LG and 14 HG PC. A 40-marker tissue-based multiplex cyclic immunofluorescence panel was used to characterize immune and tumor cells at single-cell resolution. Data were processed and analyzed in R to quantify immune subsets, assess spatial Treg distributions, and identify spatial interactions between immune populations.Results HG PC paradoxically exhibited significantly increased immune infiltration, with elevated CD4+, CD20+, CD68+, and CD163+ cell density in tumor regions and increased CD4+, CD8+, and FOXP3+CD4+ cell density in the stroma relative to LG PC. Intratumoral T cell infiltration and individual T cell subsets were increased with advancing Gleason grade ( figure 1). Notably, there were significantly more tertiary lymphoid structures (TLSs) in HG PC relative to LG PC, and the TLSs in Hg PC were more organized with lower spatial heterogeneity relative to LG PC. Treg abundance was significantly elevated in the stroma and intratumoral TLSs of HG PC, and there were non-statistically significant increases in T cell exhaustion in HG PC. TLS regions harbored higher proportions of exhausted CD4+ and CD8+ T cells compared to their respective tumor and stroma with enhanced localization surrounding Tregs (figure 2).Conclusions Our findings demonstrate significantly higher levels of immune infiltration, Tregs, and TLSs in HG vs. LG PC, challenging the notion that PC is immunologically ‘cold’ across all stages of disease. TLSs in HG PC are more organized, less spatially heterogenous, and harbor dense regions of exhausted effector T cells in close spatial proximity to Tregs. Mature TLSs are increasingly recognized as positive predictive biomarkers of immunotherapy response, 5 and these data collectively suggest that subsets of patients with HG PC could be susceptible to neoadjuvant immunotherapy approaches with the goal of minimizing recurrence and relapse in the high-risk setting.References Stultz J, Fong L. How to turn up the heat on the cold immune microenvironment of metastatic prostate cancer. Prostate Cancer Prostatic Dis. 2021;24:697-717.Bou-Dargham M, Sha L, Sang Q, Zhang J. Immune landscape of human prostate cancer: immune evasion mechanisms and biomarkers for personalized immunotherapy. BMC Cancer 2020;20:572.Topalian S, et al. Safety, Activity, and Immune Correlates of Anti-PD-1 Antibody in Cancer. N Engl J Med. 2012;366:2443-2454.Labrecque M, et al. Molecular profiling stratifies diverse phenotypes of treatment-refractory metastatic castration-resistant prostate cancer. J Clin Invest. 2019;129(10):4492–4505.Kim H, Bruno T. An introduction to tertiary lymphoid structures in cancer. Methods Mol Biol. 2025:2864:1-19.Ethics Approval The study was approved by The University of Chicago’s Ethics Board, approval number STU00009126-CR0003.Abstract 773 Figure 1Immune cell characterization. Immune cell fraction = sum of each immune cell subtype relative to the total number of cells in tumor and stroma sections. Tumor and stroma regions do not include TLSs. * = p < 0.05Abstract 773 Figure 2TLS count and size. B. Exhausted T cell distribution. C. Normalized distribution calculated by number of exhausted cells in 25um radius of Treg divided by total number of exhausted cells. Tumor and stroma regions exclude TLSs. *=p<0.05, ***=p< 0.001",
  "authors": [
    {
      "affiliations": [
        "University of Chicago, Chicago, IL, USA"
      ],
      "name": "Aishwarya Atmakuri"
    },
    {
      "affiliations": [
        "Dana-Farber Cancer Institute, Boston, MA, USA"
      ],
      "name": "Jeremiah Wala"
    },
    {
      "affiliations": [
        "Harvard University, Boston, MA, USA"
      ],
      "name": "Ali Amiryousefi"
    },
    {
      "affiliations": [
        "Harvard Medical School, Boston, MA, USA"
      ],
      "name": "Jia-Ren Lin"
    },
    {
      "affiliations": [
        "UChicago Medicine, Chicago, IL, USA"
      ],
      "name": "Brian Labadie"
    },
    {
      "affiliations": [
        "University of Chicago, Chicago, IL, USA"
      ],
      "name": "Kiranj Chaudagar"
    },
    {
      "affiliations": [
        "UChicago Medicine, Chicago, IL, USA"
      ],
      "name": "Madeleine Torcasso"
    },
    {
      "affiliations": [
        "Harvard Medical School, Boston, MA, USA"
      ],
      "name": "Peter K Sorger"
    },
    {
      "affiliations": [
        "University of Chicago Comprehensive Cancer Center, Chicago, IL, USA"
      ],
      "name": "Akash Patnaik"
    }
  ],
  "title": "773 Spatial characterization of the immune microenvironment of localized prostate cancer reveals an immunogenic subset of high-risk tumors",
  "uid": "baac938e-6ef3-5728-994d-97385451ba43"
}