Lethal prostate cancer migrates through hypoxic regions and contractile muscle using mechanosensitive integrin receptors (specifically, β1 integrin heterodimers) to escape the organ. Kindlin-2 (K2) binds and activates β1 integrin for focal adhesion (FA) assembly and is central to these functions. In live cells, we assessed K2's role in tumor cell-cell and cell-ECM (extracellular matrix) resistance and capacitance using electric cell-substrate impedance sensing (ECIS) in hypoxia (1% oxygen), before and after wounding. Reduction of K2 expression by 44% (DU145-shK2) increased the wound closure rates detected by ECIS under hypoxia-133% for cell-ECM adhesion and 127% for cell-cell adhesion. Despite increased response rates, restoration of cell-cell resistance after the wound to the pre-wound levels did not occur under hypoxia if K2 was limited. Since the wound closure rate was accelerated when K2 was limited under hypoxia, we determined the dynamics and size of integrin:K2 complexes and K2-containing FA structures under hypoxia. During the early response to hypoxia (4-8 h), α6β1:K2 complexes increased 2-fold and then returned to normal levels. The α5β1:K2 complexes remained constant until increasing at 12-16 h in hypoxia. High-resolution immunofluorescence microscopy confirmed α6β1:K2 colocalization at lamellipodial protrusions during the early response to hypoxia, with elevated α5β1:K2 complexes observed in FAs 12 h post exposure. FA abundance increased 2-fold as determined by paxillin staining, but FA size decreased up to 45% in hypoxia, persisting up to 16 h. Our collective findings suggest that under hypoxia, the biophysical cell-cell and cell-ECM interactions of cancer cells depend on K2, contain dynamic assemblies of α6β1 and α5β1 integrin:K2 complexes, and favor smaller and more numerous FAs.

PIM kinases are overexpressed in castration resistant prostate cancer (CRPC) and many small molecule PIM kinase inhibitors (smPIM inhibitors) have been designed to block the catalytic activity of PIM. However, smPIM inhibitors have shown limited efficacy in solid tumors. Notably, all these inhibitors share the common property that they increase total PIM protein levels, which limits their efficacy because PIM1 has kinase-independent pro-survival effects. Here, we identify high mobility box group 1 (HMGB1) as a novel PIM1 binding partner. Stabilization of PIM1 by smPIM inhibitors increases the cytosolic accumulation of HMGB1, which leads to activation of mitophagy and suppresses oxidative-stress induced cell death. Knockdown of PIM1/2/3 and/or HMGB1 sensitizes cancer cells to smPIM inhibitors. In contrast, treatment with a PIM PROTAC (PIMTAC) that we developed overcomes the kinase-independent pro-survival effects of PIM1 and is more effective than smPIM inhibitors in vitro and in vivo. These results uncover a mechanism of resistance that has limited the success of smPIM inhibitors and provides compelling evidence that targeted degradation of PIM is needed to realize its potential as an anti-cancer target.

Abstract The tumor-suppressor p53 prevents cancer development via initiating cell-cycle arrest, cell death, repair, or antiangiogenesis processes. Over 50% of human cancers harbor cancer-causing mutant p53. p53 mutations not only abrogate its tumor-suppressor function, but also endow mutant p53 with a gain of function (GOF), creating a proto-oncogene that contributes to tumorigenesis, tumor progression, and chemo- or radiotherapy resistance. Thus, targeting mutant p53 to restore a wild-type p53 signaling pathway provides an attractive strategy for cancer therapy. We demonstrate that small-molecule NSC59984 not only restores wild-type p53 signaling, but also depletes mutant p53 GOF. NSC59984 induces mutant p53 protein degradation via MDM2 and the ubiquitin–proteasome pathway. NSC59984 restores wild-type p53 signaling via p73 activation, specifically in mutant p53-expressing colorectal cancer cells. At therapeutic doses, NSC59984 induces p73-dependent cell death in cancer cells with minimal genotoxicity and without evident toxicity toward normal cells. NSC59984 synergizes with CPT11 to induce cell death in mutant p53-expressing colorectal cancer cells and inhibits mutant p53-associated colon tumor xenograft growth in a p73-dependent manner in vivo. We hypothesize that specific targeting of mutant p53 may be essential for anticancer strategies that involve the stimulation of p73 in order to efficiently restore tumor suppression. Taken together, our data identify NSC59984 as a promising lead compound for anticancer therapy that acts by targeting GOF-mutant p53 and stimulates p73 to restore the p53 pathway signaling. Cancer Res; 75(18); 3842–52. ©2015 AACR.

Prostate cancer is the most common non-cutaneous malignancy in men and is the second leading cause of male cancer-related mortality. Unlike many cancers, prostate cancer lacks clear genetic driver mutations, suggesting that factors in the tumor microenvironment contribute to the genesis and progression of this disease. Hypoxia, or a physiological state of low oxygen, is a universal characteristic of solid tumors that enhances disease progression and therapeutic resistance. Prostate cancer develops in a hypoxic microenvironment and primarily metastasizes to bone, where oxygen availability is similarly limited. Therefore, hypoxia is a major obstacle to the effective treatment of prostate cancer across all disease stages. Clinically, hypoxia is correlated with worse patient outcomes, largely because it drives resistance to the frontline therapies used to treat both primary and metastatic prostate cancer. Despite the established role of hypoxia in prostate cancer progression and drug resistance, it has not been successfully targeted therapeutically. Emerging evidence indicates that exposure to distinct temporal patterns of hypoxia (acute, cyclic, and chronic) elicits unique cellular adaptations that dictate tumor growth and survival. This review synthesizes current evidence regarding the role of hypoxia in promoting resistance to therapy in prostate cancer.

Prostate cancer cell invasion into the surrounding muscle capsule, known as extracapsular extension (ECE), is associated with a significantly worse prognosis (5-year survival reduction: 98% to 31%). Using a live ECE mouse xenograft model with DU145 tumor cells, our group previously demonstrated that functional heterogeneity among adhesion subtypes within invasive clusters is essential for muscle invasion. Bulk RNA sequencing from three spatial compartments (pre-invasive, invasive, and post-invasive) revealed distinct gene expression profiles, with hypoxia-related and cell–cell/cell–ECM interaction genes prominently dysregulated in muscle-invasive disease. In this study, we sought to define the single-cell transcriptional heterogeneity across the three ECE compartments and compare these patterns to a human patient-derived xenograft (PDX) model. Spatial transcriptomic analysis (STA) was performed using the Bruker CosMx platform with a 6K gene panel. Data was preprocessed (quality control and dimensional reduction) and analyzed in R 4.4.0 using Seurat v5. Notable downstream analyses included unsupervised Louvain clustering, trajectory inference with Monocle 3, and cluster-specific differential gene expression. In the ECE model, STA resolved at least 11 distinct tumor cell identity clusters previously undetectable by bulk methods and revealed a clear spatial demarcation between pre-invasive and invasive populations crossing the muscle barrier. Trajectory analysis identified a pre-invasive population branching into two invasive fates with unique expression profiles. Dispersion scores, calculated using principal component embeddings, exhibited progressively increasing intracluster heterogeneity along one branch. Strong expression enrichment of the Prolaris 31-gene prognostic panel, a clinically established marker of aggressiveness, was observed at the bifurcation point of tumor evolution. STA of the human PDX model similarly revealed a high-dispersion invasive cluster branching into two fates, one exhibiting decreased heterogeneity consistent with specialization of invasive phenotypes. Together, these findings reveal, for the first time, that tumor invasion of the extracapsular muscle layer induces substantial transcriptional heterogeneity. This dynamic process highlights potential therapeutic vulnerabilities during the transition to extracapsular extension. Targeting tumor cells at this critical juncture may represent a key strategy for preventing ECE and improving prostate cancer outcomes. Supported by P30CA023074, University of Arizona Comprehensive Cancer Center Support Grant. Saptarshi Mallick, Rafael Sainz, Jayati Chakrabarti, Kendra D. Marr, Noel A. Warfel, Gregory C. Rogers, Beatrice S. Knudsen, Rashid Sayyid, Kelvin W. Pond, Anne E. Cress. Single cell spatial transcriptomics identifies unique cell populations driving muscle invasive prostate adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Innovations in Prostate Cancer Research and Treatment; 2026 Jan 20-22; Philadelphia PA. Philadelphia (PA): AACR; Cancer Res 2026;86(2_Suppl):Abstract nr B045.

Immune checkpoint inhibitors (ICI) have changed the treatment paradigm for many cancers but have not shown benefit in prostate cancer. Chronic inflammation contributes to the immunosuppressive prostate tumor microenvironment and is associated with poor response to ICIs. The primary source of inflammatory cytokine production is the inflammasome. In this study, we identify the proviral integration site for Moloney murine leukemia virus (PIM) kinases as regulators of inflammasome activation in tumor-associated macrophages (TAM). The analysis of clinical data from a cohort of patients with treatment-naïve, hormone-responsive prostate cancer revealed that tumors from patients with high PIM1/2/3 displayed an immunosuppressive tumor microenvironment characterized by high inflammation and a high density of repressive immune cells, most notably TAMs. Macrophage-specific knockout of PIM reduced tumor growth in syngeneic models of prostate cancer. Transcriptional analyses indicated that eliminating PIM from macrophages enhanced the adaptive immune response and increased cytotoxic immune cells. Combined treatment with PIM inhibitors and ICIs synergistically reduced tumor growth. Immune profiling revealed that PIM inhibitors sensitized prostate cancer tumors to ICIs by increasing tumor suppressive TAMs and increasing the activation of cytotoxic T cells. Our data implicate macrophage PIM as a driver of inflammation that limits ICI potency and provide preclinical evidence that PIM inhibitors are an effective strategy to improve the ICI efficacy in prostate cancer.

In 2024, prostate cancer (PCa) remains the most common non-skin cancer in males within the United States, with an estimated 299,010 new cases, the highest increase incident trend rate (3.8%) of all cancers, and one of the eight deadliest. PCa cases are projected to double from 1.8 million to 2.9 million per year between 2020 and 2040. According to the National Comprehensive Cancer Network (NCCN) treatment guidelines, most cases (65%) are intermediate risk (Gleason sum score <7 [3 + 4, 4 + 3], prostate organ-confined, and PSA < 20) with treatment options limited to active surveillance, external beam radiation, and/or surgery to prevent metastasis in the long term (>10 years). It is increasingly recognized that the two most common subtypes of intermediate risk PCa are cribriform architecture (CA) and intraductal carcinoma of the prostate (IDC-P), which can occur together, and both are associated with increased metastatic risk, biochemical recurrence, and disease-specific mortality. Both subtypes display hypoxia, genomic instability, and are identified as Gleason 4 in pathology reports. However, since false negatives are common (up to 50%) in these subtypes on biopsy, more research is needed to reliably detect these subtypes that have an increased risk for invasive disease. We note that even with mpMRI-guided biopsies, the sensitivity is 54% for cribriform architecture and only 37% for IDC-P. The presence of these PCa subtypes in biopsy or radical prostatectomy (RP) tissue can exclude patients from active surveillance and from designation as intermediate risk disease, further underscoring the need for increased molecular understanding of these subtypes for diagnostic purposes. Understanding the heterogeneity of intermediate risk primary PCa phenotypes, using computational pathology approaches to evaluate the fixed biopsy specimen, or video microscopy of the surgical specimen with AI-driven analysis is now achievable. New research associating the resulting phenotypes with the different therapeutic choices and vulnerabilities will likely prevent extracapsular extension, the definition of high-risk disease, and upstaging of the final pathologic stage.

Ferroptosis is a mode of cell death that relies on iron metabolism and lipid peroxidation. Preclinical and clinical studies indicate that ferroptosis suppresses tumor growth, and dysregulation of ferroptosis promotes treatment resistance in cancer. Hypoxia is a universal feature of solid tumors that is particularly relevant to prostate cancer (PCa), which arises in the hypoxic peripheral zone of the organ. Hypoxia has been implicated in resistance to ferroptosis and other forms of cell death, but how hypoxia impacts the sensitivity of PCa to ferroptosis inducing agents (FINs) has not been well studied. Here, we show that hypoxia dramatically reduces the sensitivity of PCa cell lines to mechanistically distinct FINs, Erastin (xCT inhibitor) and RLS3 (GPX4 inhibitor) by inducing lipid droplet (LD) accumulation. Transcriptomic analysis revealed that hypoxia significantly reduced the expression of genes related to incorporating polyunsaturated fatty acids into phospholipids (ACSL4, LPCAT3), and parallel lipidomic analysis demonstrated that hypoxia significantly decreased the levels of the ferroptosis-prone lipid class, phosphatidylethanolamine (PE) and increased production of neutral lipid species, cholesteryl ester (ChE (22:5)) and triglycerides (TG(48:1), TG:(50:4), and TG(58:4)). Targeting LD biogenesis and de novo lipogenesis did not alter sensitivity to RSL3 under hypoxia. These findings suggest that hypoxia promotes ferroptosis resistance in PCa by altering lipid metabolism at the transcriptional level, by producing lipids that are less susceptible to peroxidation, and at the cellular level, by increasing storage in LDs. Thus, manipulating LD dynamics represents a promising strategy to overcome hypoxia-induced resistance to ferroptosis and improve the success of PCa treatment.

Lipid droplets (LDs) are dynamic organelles with a neutral lipid core surrounded by a phospholipid monolayer. Solid tumors exhibit LD accumulation, and it is believed that LDs promote cell survival by providing an energy source during energy deprivation. However, the precise mechanisms controlling LD accumulation and utilization in prostate cancer are not well known. Here, we show peroxisome proliferator-activated receptor α (PPARα) acts downstream of PIM1 kinase to accelerate LD accumulation and promote cell proliferation in prostate cancer. Mechanistically, PIM1 inactivates glycogen synthase kinase 3 beta (GSK3β) via serine 9 phosphorylation. GSK3β inhibition stabilizes PPARα and enhances the transcription of genes linked to peroxisomal biogenesis (PEX3 and PEX5) and LD growth (Tip47). The effects of PIM1 on LD accumulation are abrogated with GW6471, a specific inhibitor for PPARα. Notably, LD accumulation downstream of PIM1 provides a significant survival advantage for prostate cancer cells during nutrient stress, such as glucose depletion. Inhibiting PIM reduces LD accumulation in vivo alongside slow tumor growth and proliferation. Furthermore, TKO mice, lacking PIM isoforms, exhibit suppression in circulating triglycerides. Overall, our findings establish PIM1 as an important regulator of LD accumulation through GSK3β-PPARα signaling axis to promote cell proliferation and survival during nutrient stress.

Abstract Introduction: Castration-resistant prostate cancer (CRPC) is an incurable and lethal progression of the disease that does not respond to any treatment options. Cell adhesion to the extracellular matrix (ECM) activates survival pathways, allowing cancer cells to evade anti-cancer therapy, a phenomenon known as cell adhesion-mediated drug resistance. Bone, which is the primary site of prostate cancer metastasis, is known to be enriched in laminin, a ubiquitous ECM protein. In addition, laminin binding integrins, α6β1 and α3β1, are the major integrins expressed in CRPC, suggesting that laminin-dependent adhesion provides a survival advantage. Based on these findings, activation of the laminin-binding integrin, α6β1, is an intriguing factor mediating resistance to therapy in CRPC. PIM1 is an oncogenic Ser/Thr kinase that is elevated in CRPC and is known to promote resistance to therapy. In contrast, to many pro-survival kinases, PIM kinases do not possess any obvious regulatory domains. Current evidence suggests that PIM1 is constitutively active when it is expressed, so PIM1 expression level directly correlates with its catalytic activity. Despite this fact, little is known about the internal and external mechanisms that dictate PIM1 protein levels and spatial activation in cancer cells. Here, we identify PIM1 as a key survival signal that contributes to cell adhesion-mediated drug resistance. Experimental procedures: Supporting the importance of this signaling axis in human tumors, multiplex IHC of a TMA containing prostate adenocarcinoma and CRPC bone metastases to show that integrin α6 and PIM1 are coexpressed and spatially correlated in primary and metastatic prostate cancer. To examine the spatiotemporal dynamics of PIM1 during cell adhesion, We developed a kinase activity reporter (PIMKAR) to monitor PIM catalytic activity in live cells. Because we observed PIM was highly localized to the membrane in patient tumors, we tagged PIMKAR with a myristylation sequence to specifically measure PIM activity at the membrane vs cytosol. Immunofluorescence and biochemical techniques were used to demonstrate the effect of PIM1 on mitophagy and oxidative stress. Conclusions: We demonstrate that activation of integrin α6β1 downstream of cell adhesion stabilizes PIM1 by blocking its proteasomal degradation. The resulting upregulation of PIM1 serves to reduce oxidative stress through complementary mechanisms reducing mitochondrial fragmentation and increasing the removal of damaged mitochondria by increasing mitophagy. Mechanistically, PIM1 upregulates BNIP3 to enhance mitophagy and thereby reduce oxidative stress in the cell. Together, these results expand our understanding of the mechanisms regulating PIM1 activation and provide evidence for the use of PIM inhibitors in bone mCRPC and other cancers where laminin is a major component of the ECM Citation Format: Caitlyn Flores, Shailender Chauhan, Cynthia Miranti, Anne Cress, Gregory Rogers, Noel Warfel. PIM kinases drive cell adhesion mediated drug resistance in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4618.

BACKGROUND: The ubiquitin-proteasome system regulates protein degradation and the development of pulmonary arterial hypertension (PAH), but knowledge about the role of deubiquitinating enzymes in this process is limited. UCHL1 (ubiquitin carboxyl-terminal hydrolase 1), a deubiquitinase, has been shown to reduce AKT1 (AKT serine/threonine kinase 1) degradation, resulting in higher levels. Given that AKT1 is pathological in pulmonary hypertension, we hypothesized that UCHL1 deficiency attenuates PAH development by means of reductions in AKT1. METHODS: Tissues from animal pulmonary hypertension models as well as human pulmonary artery endothelial cells from patients with PAH exhibited increased vascular UCHL1 staining and protein expression. Exposure to LDN57444, a UCHL1-specific inhibitor, reduced human pulmonary artery endothelial cell and smooth muscle cell proliferation. Across 3 preclinical PAH models, LDN57444-exposed animals, Uchl1 knockout rats ( Uchl1 −/− ), and conditional Uchl1 knockout mice ( Tie2Cre-Uchl1 fl/fl ) demonstrated reduced right ventricular hypertrophy, right ventricular systolic pressures, and obliterative vascular remodeling. Lungs and pulmonary artery endothelial cells isolated from Uchl1 −/− animals exhibited reduced total and activated Akt with increased ubiquitinated Akt levels. UCHL1-silenced human pulmonary artery endothelial cells displayed reduced lysine(K)63-linked and increased K48-linked AKT1 levels. RESULTS: Supporting experimental data, we found that rs9321, a variant in a GC-enriched region of the UCHL1 gene, is associated with reduced methylation (n=5133), increased UCHL1 gene expression in lungs (n=815), and reduced cardiac index in patients (n=796). In addition, Gadd45α (an established demethylating gene) knockout mice ( Gadd45α −/− ) exhibited reduced lung vascular UCHL1 and AKT1 expression along with attenuated hypoxic pulmonary hypertension. CONCLUSIONS: Our findings suggest that UCHL1 deficiency results in PAH attenuation by means of reduced AKT1, highlighting a novel therapeutic pathway in PAH.

211 Background: The Proviral Integration site for Moloney murine leukemia virus ( PIM1, 2, and 3) kinases are frequently overexpressed in prostate cancer (PC) and associated with aggressiveness and immune evasion. PIM overexpression increases macrophage infiltration and survival in in vivo models of PC. Here, we characterized the association of PIM1/2/3 triplet-combined High versus Low with PC immune signatures on real-world patients' clinical presentation. Methods: 44 patients of treatment-naive metastatic hormone-sensitive PC (mHSPC) patients (pts) samples were analyzed by next-generation sequencing (592, NextSeq; WES, NovaSeq), (WTS; NovaSeq) (Caris Life Sciences, Phoenix, AZ). PC with PIM1/2/3-high(H) (N=28) and -low(L) (N=16) expressions were classified by top and bottom quartile, respectively. Pathway enrichment was determined by GSEA (Broad Inst). Immune cell fractions were calculated by deconvolution of WTS using Quantiseq. Statistical significance was determined by Mann-Whitney U and adjusted for multiple comparisons (p<0.05). Continuous and categorical variables were evaluated using t-tests or Kruskal-Wallis Rank sum tests and Chi-square or Fisher’s exact tests, respectively. Results: mHSPC pts median ages were 67.28 (SD 10.65), 88% White, 44% non-Hispanic, ECOG <2 95% and other demographics showed no differences between PIM-H and L. PIM-H vs L tumors presentation was 48 vs 35% Gleason >9, 82 vs 57% T>3, 76 vs 69% N1, and 92 vs 81% M1, all p>0.05. Median PSA levels at diagnosis were 66.0 [14.0-450.7] vs 24.0 [6.6-95.0] by PIM-H and L, p=0.14. PIM-H had a higher median MAPK activation score compared to PIM-L PC (0.85 vs -1.38, q<0.05). PIM-H PC exhibited higher PSA (548.2 vs 213.2) and AR (118.6 vs 50.8) expression, all q<0.05. PIM-H had enrichment of protein secretion signaling pathway (NES: 1.2; FDR <0.25). PIM-H had higher expression of immunostimulatory ( IL1β, TNF, IL-2, and TNFSF13, FC: 1.9-3.1, p<0.05) and hypoxia-related genes ( HIF1⍺, ARNT, VEGFA, PDGFB, LDHA, NDRG1, SLC2A, PGK1, and DDIT4, FC: 1.3-2.4, p<0.05). PIM-H had higher expression of MHC class I (HLA-A, -B, -C, TAP1, TAP2, B2M, FC: 1.9-2.2, all p<0.05) and MHC class II (HLA-DPA1, -DRB1, -DPB2, -DQB2, -DBP1, -DQB1 FC: 1.8-3.2, all p<0.05) genes. PIM-H had increased infiltration of B cells, M2 MØ and NK cells (all p <=0.05). PIM-H PC had a higher T cell inflamed score (70 vs -138, p<0.05). Conclusions: These data indicate a strong association of PIM expression with increased MAPK activation score, T cell inflamed score, inflammatory, PSA, AR, MHC class I and MHC class II gene expression, and differential immune cell infiltration. However, this did not significantly translate to a worse clinical presentation of mHSPC. A better understanding of these differences with additional research may provide a rationale for tailored therapeutic approaches for PIM-expressing mHSPC.

Abstract The PIM kinase family are serine/threonine kinases known to be overexpressed in castration-resistant prostate cancer (CRPC). PIM1, an isoform of PIM, is known to regulate cell survival, migration, and proliferation. Uniquely, PIM kinases are constitutively active due to the lack of a regulatory domain. Therefore, PIM protein levels are reflected in PIM activity and are regulated by protein degradation and synthesis. PIM inhibitors have been developed, targeting the PIM kinase activity and inhibiting phosphorylation of downstream targets, but have had limited efficacy. Our lab and others demonstrate that PIM inhibitor treatment increases total PIM protein levels, suggesting that PIM kinases control protein stability via autophosphorylation. To elucidate the mechanism of autophosphorylation dependent regulation of PIM1, we used phospho-proteomics to identify potential autophosphorylation sites on PIM1. We have identified overexpression of deubiquitinase USP28 inhibiting degradation of PIM1, leading to the investigation of the role of F-box protein Fbw7 in regulating PIM1. Dominant-negative expression of Fbw7 results in increased PIM1 total protein. Additionally, coimmunoprecipitation of Fbw7 knockdown cells resulted in decreased PM1 ubiquitination compared to control. Therefore, we have identified Fbw7 as a putative E3 ligase responsible for PIM1 degradation. To address the limited efficacy of PIM inhibitors, we have developed the first PIM-PROTAC (PIMTAC) with our collaborators. Proteolysis targeting chimera (PROTAC) is a promising approach to eliminating the pro-tumorigenic effects of PIM. The PIMTAC selectively targets PIM kinases for degradation and we have demonstrated in vitro efficacy. PIMTAC successfully maintains degradation of all isoforms of PIM for over 72 hours. In vitro assessment of anti-tumor efficacy demonstrated increased apoptotic death with PIMTAC alone compared to PIM inhibitor or docetaxel. Furthermore, dual treatment of PIMTAC and docetaxel had more apoptotic death compared to PIM inhibitor with docetaxel. We aim to develop the PIMTAC for pre-clinical testing. Citation Format: Hope Liou, John Brognard, Rolf Swenson, Pedro Torres-Ayuso, Noel Warfel. Defining PIM kinase protein regulation and PROTAC for pre-clinical testing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4508.

Abstract Prostate cancer is the second leading cause of cancer-related deaths in American men. While prostate cancer patients typically respond to androgen-deprivation therapy, androgen receptor signaling inhibitor (ARSI), and/or taxane chemotherapy, patients inevitably develop resistance, and the disease progresses to an untreatable and lethal form known as castrate resistant prostate cancer (CRPC). Immunotherapy has changed the treatment paradigm for many types of cancer; however, immune checkpoint inhibitors have not shown clinical benefits in CRPC. Clinical and preclinical evidence indicates that this lack of efficacy can largely be attributed to the immunosuppressive tumor microenvironment. Tumor associated macrophages (TAMs) secrete factors that promote tumor progression and suppress antitumor immunity, making them a promising therapeutic target. The Proviral Integration site for Moloney murine leukemia virus (PIM) kinases are serine/threonine kinases that are overexpressed in prostate cancer. PIM regulates many signaling pathways that promote cell proliferation and survival. However, how PIM kinase alters the prostate tumor immune microenvironment and impacts immunotherapy resistance is not well understood. We analyzed primary prostate and metastatic lymph node samples from treatment-naive metastatic hormone-sensitive prostate cancer patients. Prostate cancer samples with PIM1/PIM2/PIM3-high and -low expression were classified by top and bottom quartile, respectively. PIM high tumors had higher expression of immunostimulatory genes (IL1β, TNF, and TNFSF13), increased infiltration of M2 macrophages, B cells, and NK Cells, and a higher T cell inflamed score compared to PIM-low tumors. Our results demonstrate that PIM overexpressing prostate tumors display increased inflammation and infiltration of immunosuppressive immune cells, including M2 macrophages. Due to the changes observed in inflammation, we hypothesized that PIM kinase may regulate macrophage inflammatory signaling. We treated bone marrow derived macrophages with a PIM kinase inhibitor and showed that PIM inhibition suppresses inflammasome signaling and the release of the pro-inflammatory cytokine, IL-1β. Chronic inflammation can lead to the recruitment of TAMs, further promoting resistance to immune checkpoint inhibitors. Utilizing a syngeneic mouse model of prostate cancer, we demonstrated that PIM inhibition in combination with immune checkpoint blockade synergistically decreased tumor growth. Furthermore, immunoprofiling demonstrated that combination treatment enhances T cell activity. Overall, our results suggest that PIM kinase plays an important role in regulating the prostate tumor immune microenvironment and that PIM kinase may be a potential target to enhance the efficacy of immunotherapy for the treatment of prostate cancer. Citation Format: Amber N. Clements, Kai Sutterby, Sachin Kumar Deshmukh, Sharon Wu, Joanne Xiu, Alex Farrell, Milan Radovich, Chadi Nabhan, Elisabeth I. Heath, Rana R. McKay, Alejandro Recio-Boiles, Noel A. Warfel. PIM kinases alter the prostate tumor immune microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6875.

Supplementary Figures S1-S5 from Nelfinavir, A Lead HIV Protease Inhibitor, Is a Broad-Spectrum, Anticancer Agent that Induces Endoplasmic Reticulum Stress, Autophagy, and Apoptosis In vitro and In vivo

Prostate 3D cell networks require expression of integrin α6, FAK, and uPAR