Background: The Proviral Integration site for Moloney murine leukemia virus (PIM) kinases, a family of pro-survival kinases (PIM1, PIM2, and PIM3), are frequently overexpressed in prostate cancer (PC) and associated with PC aggressiveness and immune evasion. Preclinical data indicate that PIM1 overexpression increases macrophage infiltration and survival using in vivo models of PC. Here, we characterized the association of PIM1, PIM2, and PIM3 with PC immune signatures. Methods: 77 primary prostate and 11 metastatic lymph node samples from treatment-naive metastatic hormone-sensitive PC pts were analyzed by DNA next-generation sequencing (592-gene, NextSeq; WES, NovaSeq) and Whole Transcriptome Sequencing (WTS; NovaSeq) (Caris Life Sciences, Phoenix, AZ). PC with PIM1/PIM2/PIM3-high(H) and -low(L) expression were classified by top and bottom quartile, respectively. Androgen receptor (AR) signature and Neuroendocrine Prostate Cancer (NEPC) score were calculated based on the expression level of previously defined gene signatures (Hieronymus et al. 2006, Beltranet al. 2016). Pathway enrichment was determined by GSEA (Broad Inst). Immune cell fractions were calculated by deconvolution of WTS using Quantiseq. Statistical significance was determined by chi-square and Mann-Whitney U (p < 0.05) and adjusted for multiple comparisons (q < 0.05). Results:PIM1/PIM2/PIM3-H PC had a higher median MAPK activation score (MPAS) compared to PIM1/PIM2/PIM3-L PC (0.9, 1.3, 0 vs -1.6, -1.4, -1.1 respectively, all p < 0.05). There was no difference in AR signature or NEPC score between PIM-H and PIM-L PC. PIM3-H PC exhibited higher PSA expression (3.15-fold, p < 0.05). PIM1/PIM2-H PC had higher AR expression (1.9 and 3.5-fold, respectively, all p < 0.05). PIM2/PIM3-H PC had enrichment of PI3K/AKT/mTOR, IL2/STAT5, IL6/JAK/STAT3, KRAS, TGFβ, NOTCH, hypoxia signaling, and ROS, P53, OXPHOS pathway and EMT (NES: 1.3-1.5, all FDR < 0.25). PIM1/PIM2-H PC had higher expression of immunostimulatory genes (IL1β, TNF, and TNFSF13, FC: 1.1-3.1, p < 0.05). PIM1/PIM2/PIM3-H PC had higher expression of MHC class I (HLA-A, HLA-B, HLA-C, B2M, FC: 1.3-2.5, all p < 0.05) and MHC class II (HLA-DPA1, HLA-DRB1, HLA-DPB2, TAP1, TAP2, FC: 1.1-3.2, all p < 0.05) genes. PIM3-H PC had increased infiltration of M2 macrophages (8% vs 5.2%) and NK cells (5.2% vs 3.3%), while PIM2-H PC had increased Tregs (1.7% vs 0%) (all p < 0.05). Moreover, PIM1/PIM2/PIM3-H PC had a high T cell inflamed score compared to PIM1/PIM2/PIM3-L PC (66, 80, 56 vs -143, -157, -136, respectively, all p < 0.05). Conclusions: Our data suggest a strong association between PIM expression and increased MAPK activation score, T cell inflamed score, inflammatory, MHC class I and MHC class II gene expression, and differential immune cell infiltration. A better understanding of these differences will provide a rationale for tailored therapeutic approaches for PIM-expressing PC.