High-resolution immune atlas of murine healthy prostate and prostate cancer from neoplasia to adenocarcinoma stage in the inducible PTEN(i)pe-/- mice

Prostate cancer (PCa) is the most commonly diagnosed cancer and the second leading cause of cancer-related mortility among men in western societies. PCa exhibits a protracted progression, initiating as Prostatic Intraepithelial Neoplasia (PIN), advancing to adenocarcinoma, and eventually culminating in metastatic dissemination. The advent of Immune Checkpoint Inhibitors (ICI) has been revolutionized the field of cancer immunology. However, the efficacy of immunotherapy in PCa has been limited, and the role of immune cells in prostate tumorigenesis has only recently been explored. In this study, we performed an in-depth characterization of immune cells in healthy murine prostate and during PCa progression in PTEN(i)pe-/- mice. In this model, the PTEN gene is selectively ablated in prostatic luminal epithelial cells at adulthood (PSA-CreERT2), closely mimicking human PCa development. Notably, tumor progression in this model is gradual, with the PIN stage manifesting at 3 months post-gene invalidation and the adenocarcinoma stage at 9 months. The strict temporal control of PTEN depletion coupled with the slow tumor progression, makes the PTEN(i)pe-/- mouse model an invaluable tool for delineating immune infiltration during tumor development and evaluating therapeutic interventions. Here we performed scRNAseq on CD45+ immune cells residing in the dorsolateral lobes of prostate at respectively 3 and 9 months post tamoxifen treatment of PTEN(i)pe-/- and control mice, allowing to establish a high-resolution immune atlas of murine PCa from neoplasia to adenocarcinoma. Our findings reveal significant heterogeneity among mononuclear phagocytes (dendritic cells and macrophages), neutrophils and lymphoid immune cells in the prostate. Various neutrophil clusters exhibit an immunosuppressive signature from the PIN stage onward. We observed the recruitment of Trem2+ tumor-associated macrophage subset during PCa, potentially contributing to tumorigenesis. Additionally, there was an increase in CD8+ T lymphocytes in PCa, which exhibited an activated/exhausted phenotype. Our study elucidates the intricate dynamics of immune cell behavior in PCa from early to late stages. These insights pave the way for novel immunotherapeutic strategies to treat prostate cancer, thereby advancing the field of tumor immunology. To establish a high-resolution immune atlas of healthy prostate and prostate cancer we performed scRNA-seq on sorted tissue resident CD45+ immune cells from the inducible adult PTEN(i)pe-/- mice at the Prostatic Intraepithelila Neoplasia stage (PIN) and Adenocarcinoma stages, and age-matched healthy PTENL2/L2 control individuals at 3months and 9months post tamoxifen administration respectively. Few minutes prior sacrifice, mice were injected intravenously with fluorescent anti-CD45.2 antibodies to perform blood/tissue partitioning, allowing to exclude cells present in the vasculature and ensure to study solely the immune cells present in prostate parenchyma. Cells were extracted from DLV prostate lobes by enzymatic digestion. Prostate samples from three PTEN(i)pe-/- mice at 3months post tamoxifen were pooled prior to sorting. Similarly, prostate samples from five sex-matched PTENL2/L2 control littermates at 3months post-tamoxifen were also pooled prior to sorting. The same approach was applied for the 9months samples of PTEN(i)pe-/- and control mice respectively. Tissue resident CD45+ immune cells were sorted by fluorescence-activated cell sorting (FACS). As we found previously that neutrophils were prevalent within the leukocyte infiltrate from PIN to adenocarcinoma stages of Pten(i)pe-/-prostate, neutrophils were sorted separately from the other CD45+ immune cells and cells were mixed again at a 25% ratio of neutrophils with 75% of CD45+ non neutrophil immune cells prior 10X Genomics Chromium System encapsulation and scRNAsequencing. We included 8 independent samples encompassing 2 replicates of PtenL2/L2 control 3 months, PtenL2/L2 control 9 months, Pten(i)pe-/- 3 months PIN and Pten(i)pe-/- 9 months adenocarcinoma.