Mannose Receptor-positive Macrophage Infiltration Correlates with Prostate Cancer Onset and Metastatic Castration-resistant Disease

Targeting the tumor microenvironment, a new therapeutic approach for prostate cancer

BACKGROUND

A growing number of studies have shown that in addition to adaptive immune cells such as CD8 + T cells and CD4 + T cells, various other cellular components within prostate cancer (PCa) tumor microenvironment (TME), mainly tumor-associated macrophages (TAMs), cancer-associated fibroblasts (CAFs) and myeloid-derived suppressor cells (MDSCs), have been increasingly recognized as important modulators of tumor progression and promising therapeutic targets.

OBJECTIVE

In this review, we aim to delineate the mechanisms by which TAMs, CAFs and MDSCs interact with PCa cells in the TME, summarize the therapeutic advancements targeting these cells and discuss potential new therapeutic avenues.

METHODS

We searched PubMed for relevant studies published through December 10 2023 on TAMs, CAFs and MDSCs in PCa.

RESULTS

TAMs, CAFs and MDSCs play a critical role in the tumorigenesis, progression, and metastasis of PCa. Moreover, they substantially mediate therapeutic resistance against conventional treatments including anti-androgen therapy, chemotherapy, and immunotherapy. Therapeutic interventions targeting these cellular components have demonstrated promising effects in preclinical models and several clinical trials for PCa, when administrated alone, or combined with other anti-cancer therapies. However, the lack of reliable biomarkers for patient selection and incomplete understanding of the mechanisms underlying the interactions between these cellular components and PCa cells hinder their clinical translation and utility.

CONCLUSION

New therapeutic strategies targeting TAMs, CAFs, and MDSCs in PCa hold promising prospects. Future research endeavors should focus on a more comprehensive exploration of the specific mechanisms by which these cells contribute to PCa, aiming to identify additional drug targets and conduct more clinical trials to validate the safety and efficacy of these treatment strategies.

m6A modification-dependent upregulation of WNT2 facilitates M2-like macrophage polarization and perpetuates malignant progression of nasopharyngeal carcinoma

The development and progression of nasopharyngeal carcinoma (NPC) involves intricate interactions between tumor cells and other surrounding cells in the tumor microenvironment (TME). Tumor-associated macrophages (TAMs) play pivotal roles in the progression of NPC, but their interactions remain largely unexplored. In this study, we revealed that NPC promoted M2-like polarization of TAMs through enhanced synthesis and secretion of WNT2. These M2-type macrophages, in turn, significantly boosted the proliferation and metastasis of NPC. This vicious cycle perpetuated the malignant progression of NPC. Mechanistically, elevated m6A modification of WNT2 in NPC stabilized its mRNA and facilitated its protein expression, which is coordinately regulated by the m6A "eraser" ALKBH5 and the "reader" YTHDF1. NPC promoted M2-like polarization of macrophages by activating the FZD2/β-catenin signaling axis through paracrine WNT2. Furthermore, elevated WNT2 can also trigger the WNT/β-catenin signaling pathway in NPC cells through autocrine signaling, synergically contributing to NPC development. The research reveals that WNT2 is upregulated in an m6A modification-dependent manner and promotes M2-like macrophages polarization of TAMs and malignant progression of NPC. This discovery provides novel potential molecular markers and therapeutic targets for the diagnosis and treatment of NPC.

A review of the efficacy of prostate cancer therapies against castration-resistant prostate cancer

The standard treatments for prostate cancer (PCa) include chemotherapy, hormone therapy, targeted therapies based on androgen receptor (AR) and/or gonadotropin-releasing hormone (GnRH) receptor antagonists, and radiation therapy. But PCa therapeutic resistance remains an unsolved challenge, leading to progression to castration-resistant prostate cancer (CRPC). Emerging PCa therapies - including poly(ADP-ribose) polymerase (PARP) inhibitors, AR crosstalk signalling pathway inhibitors, B-cell lymphoma 2 (BCL-2) inhibitors, cyclin-dependent kinase 4 (CDK4)/CDK6 inhibitors, CRISPR/Cas9, epigenetic inhibitors, and nanotechnology-based drug-delivery approaches - provide promising targeted solutions. Targeted protein degradation therapy, particularly AR degradation therapies, effectively inhibits resistance at its source. This review summarises the established and emerging PCa therapies, focusing on discussing their efficacy in terms of PCa resistance with supporting experimental findings and the mechanisms of PCa drug resistance.

The human RNASET2 alarmin-like molecule differentially affects prostate cancer cells behavior in both cell autonomous and non-cell autonomous manners

The identification of molecules that make cancer cells detectable by the immune system represents a major challenge in tumor immunology. Alarmins, endogenous, stress-induced molecules, serve as early warning signals triggering immune responses. The human RNASET2 protein has demonstrated both oncosuppressive and immunoregulatory functions across various cancer types, yet its role as an oncosuppressor or alarmin-like molecule in prostate cancer (PCa) is unexplored. Here, we investigated the effects of the human RNASET2 alarmin in two different human PCa cell lines focusing on cell proliferation, colony formation, adhesion, migration rates, and release of soluble immune-modulatory factors. In vivo studies were also carried out on nude mice to assess the immune regulatory impact. Our findings indicate that RNASET2 overexpression reduced cell proliferation and colony formation in 22Rv1 cells, through downregulation of cyclin D1. RNASET2 overexpression in 22Rv1 cells was also associated with decreased levels of TWIST, CTNNB1, YAP, and MMP-9. By contrast, PC-3 cells were largely unresponsive to RNASET2. RNASET2 overexpression also promoted the release of soluble factors related to monocyte/macrophage recruitment/activation and cytokines/chemokines, linked to immune cell-mediated anti-tumor responses. This effect was more pronounced in RNASET2-overexpressing 22Rv1 cells and involved both innate (NK cells, dendritic cells) and adaptive (T cells) immune activation, compared to PC-3 cells. RNASET2 overexpression also affected the cytoskeletal organization in both PCa models. RNASET2 overexpression in vivo induced a shift toward M1-like macrophage polarization pattern, while decreasing the M2-like polarization in mice challenged with 22Rv1 cells, indicating a potential tumor-suppressive role in PCa. Finally, silencing of RNASET2 in THP-1 macrophages unveiled their phagocytic activities against PCa cells. Our findings underscore the RNASET2's dual functionality, acting through both cell-autonomous and non-cell autonomous mechanisms in PCa in vitro and in vivo models and suggest its potential as a therapeutic target in a subset of PCa.

Inhibition of PIM Kinase in Tumor-Associated Macrophages Suppresses Inflammasome Activation and Sensitizes Prostate Cancer to Immunotherapy

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.

Neutrophil-and-monocyte-to-lymphocyte ratio is positively associated with elevated prostate-specific antigen levels and high-risk prostate cancer: evidence from the NHANES (2003-2008)

Introduction

Prostate cancer (PCa) is a prevalent malignancy in men globally. The total prostate-specific antigen (TPSA) test is essential for PCa screening. The neutrophil-and-monocyte-to-lymphocyte ratio (NMLR) has emerged as a potential biomarker for various diseases, but its relationship with PCa and TPSA is yet to be studied. This research aims to explore the connection between NMLR and TPSA levels, as well as high-risk prostate cancer (HRPCa), utilizing data from the National Health and Nutrition Examination Survey (NHANES) spanning 2003 to 2008.

Methods

The study included 4,248 U.S. adult males. NMLR was calculated as the ratio of the combined counts of peripheral neutrophils and monocytes to the counts of peripheral lymphocytes. Weighted multiple linear and logistic regression models were used to analyze the relationship between NMLR, TPSA levels, and HRPCa.

Results

A significant positive association was found between elevated NMLR levels and increased TPSA (β = 0.35, 95% CI: 0.21-0.49), as well as higher odds of HRPCa (OR = 2.04, 95% CI: 1.55-2.68). Smooth curve fitting results indicate that there is a nonlinear positive correlation between NMLR and TPSA, as well as between NMLR and HRCa.

Conclusion

This study reveals a significant relationship between NMLR, TPSA levels, and HRPCa odds among U.S. males, suggesting that NMLR could be a valuable biomarker for assessing PCa risk, underscoring inflammation's role in prostate health. Further research is encouraged to explore its applications in early detection, treatment efficacy evaluation and risk stratification.

Establishing a Prognostic Model Correlates to Inflammatory Response Pathways for Prostate Cancer via Multiomic Analysis of Lactylation-Related Genes

Prostate cancer (PCa) continues to pose substantial clinical challenges, with molecular heterogeneity significantly impacting therapeutic decision-making and disease trajectories. Emerging evidence implicates protein lactylation-a novel epigenetic regulatory mechanism-in oncogenic processes, though its prognostic relevance in PCa remains underexplored. Through integrative bioinformatics interrogation of lactylation-associated molecular signatures, we established prognostic correlations using multivariable feature selection methodologies. Initial screening via differential expression analysis (limma package) coupled with Cox proportional hazards modeling revealed 11 survival-favorable regulators and 16 hazard-associated elements significantly linked to biochemical recurrence. To enhance predictive precision, ensemble machine learning frameworks were implemented, culminating in a 10-gene lactylation signature demonstrating robust discriminative capacity (concordance index = 0.738) across both primary (TCGA-PRAD) and external validation cohorts (DKFZ). Multivariable regression confirmed the lactylation score's prognostic independence, exhibiting prominent associations with clinicopathological parameters including tumor staging and metastatic potential. The developed clinical-molecular nomogram achieved superior predictive accuracy (C - index > 0.7) through the synergistic integration of biological and clinical covariates. Tumor microenvironment deconvolution uncovered distinct immunological landscapes, with high-risk stratification correlating with enriched stromal infiltration and immunosuppressive phenotypes. Pathway enrichment analyses implicated chromatin remodeling processes and cytokine-mediated inflammatory cascades as potential mechanistic drivers of prognostic divergence. Therapeutic vulnerability profiling demonstrated differential response patterns: low-risk patients exhibited enhanced immune checkpoint inhibitor responsiveness, whereas high-risk subgroups showed selective chemosensitivity to docetaxel and mitoxantrone. Functional validation in PC-3 models revealed AK5 silencing induced proapoptotic effects, suppressed metastatic potential of migration and invasion, and modulated immune checkpoint regulation through CD276 coexpression. These multimodal findings position lactylation dynamics, particularly AK5-mediated pathways, as promising therapeutic targets and stratification biomarkers in PCa management.

Overexpression of fibroblast activation protein (FAP) in the stroma of proliferative inflammatory atrophy (PIA) and primary adenocarcinoma of the prostate

Fibroblast activation protein (FAP) is a serine protease upregulated at sites of tissue remodelling and cancer that represents a promising therapeutic and molecular imaging target. In prostate cancer, studies of FAP expression using tissue microarrays are conflicting, such that its clinical potential is unclear. Furthermore, little is known regarding FAP expression in benign prostatic tissues. Here we demonstrated, using a novel iterative multiplex immunohistochemistry assay in standard tissue sections, that FAP was nearly absent in normal regions ​but was increased consistently in regions of proliferative inflammatory atrophy (PIA). In carcinoma, FAP was expressed in all cases ​but was highly heterogeneous. High FAP levels were associated with increased pathological stage and cribriform morphology. We verified that FAP levels in cancer correlated with CD163+ M2 macrophage density. In this first report to quantify FAP protein in benign prostate and primary tumours, using standard large tissue sections, we clarify that FAP is present in all primary prostatic carcinomas, supporting its potential clinical relevance. The finding of high levels of FAP within PIA supports the injury/regeneration model for its pathogenesis and suggests that it harbours a protumourigenic stroma, yet ​high levels of FAP in benign regions could lead to false-positive FAP-based molecular imaging results in clinically localised prostate cancer.

Personalized Medicine: Leave no Patient Behind; Report From the 2024 Coffey-Holden Prostate Cancer Academy Meeting

INTRODUCTION

The 11th Annual 2024 Coffey - Holden Prostate Cancer Academy (CHPCA) Meeting, was themed "Personalized Medicine: Leave No Patient Behind," and was held from June 20 to 23, 2024 at the University of California, Los Angeles, Luskin Conference Center, in Los Angeles, CA.

METHODS

The CHPCA Meeting is an academy-styled annual conference organized by the Prostate Cancer Foundation, to focus discussion on the most critical emerging research that have the greatest potential to advance knowledge of prostate cancer biology and treatment. The 2024 CHPCA Meeting was attended by 75 academic investigators and included 37 talks across 8 sessions.

RESULTS

The meeting sessions focused on: novel human, mouse and systems biology research models, novel immunotherapies for prostate cancer, efforts to overcome treatment resistance, the role of metabolism and diet in prostate cancer biology and as a therapeutic target, mechanisms that drive differentiation into neuroendocrine cancer subtypes, the evolving prostate cancer epigenome in disease progression and treatment resistance, and machine learning and advanced computational approaches for precision oncology.

DISCUSSION

This article summarizes the presentations and discussions from the 2024 CHPCA Meeting. We hope that sharing this knowledge will inspire and accelerate research into new discoveries and solutions for prostate cancer.

Tumors in the setting of dupilumab use: A review of the literature

Dupilumab is the first monoclonal antibody approved for treating moderate-to-severe atopic dermatitis (AD) and has significantly improved the quality of life of AD patients. However, the safety of dupilumab is yet unclear in the context of cancer. Therefore, we aimed to investigate the safety of dupilumab and its relationship with the progression and occurrence of tumors. By reviewing relevant medical records of 90 patients who had pre-existing tumors before dupilumab treatment or presented new tumors after dupilumab treatment, we found that dupilumab probably had no significant negative effects on most tumors, but several patients with Cutaneous T-cell lymphomas (CTCLs) had relatively unfavorable outcomes during dupilumab treatment. Besides, CTCLs and lymphomas accounted for the majority of patients who presented new tumors after dupilumab treatment. Several patients were first diagnosed with presumed AD and probably were the presentations of CTCL at an early stage, and they developed typical CTCL symptoms after dupilumab treatment. Finally we came to the conclusion that dupilumab is safe for most patients with cancer. However, the effect of dupilumab on CTCLs is disputable. The use of dupilumab requires individual evaluation and closely monitored. When the efficacy is poor, re-evaluation of the diagnosis, especially of CTCLs and related diseases, is necessary.

A specific and adaptable approach to track CD206+ macrophages by molecular MRI and fluorescence imaging

Rationale: The mannose receptor (CD206, expressed by the gene Mrc1) is a surface marker overexpressed by anti-inflammatory and pro-tumoral macrophages. As such, CD206+ macrophages play key roles in the immune response to different pathophysiological conditions and represent a promising diagnostic and therapeutic target. However, methods to specifically target these cells remain challenging. In this study, we describe a multi-mannose approach to develop CD206-targeting fluorescent and MRI agents that specifically and sensitively detect and monitor CD206+ macrophage immune response in different disease conditions. Methods: We designed and synthesized fluorescent agents MR1-cy5 and MR2-cy5, and MRI agents Mann2-DTPA-Gd and MannGdFish. Cellular assays using pro-inflammatory and anti-inflammatory macrophages differentiated from RAW 264.7 cells were performed, and signals were detected by fluorescence microscopy and inductively coupled plasma mass spectrometry (ICP-MS) to validate specificity in vitro. In vivo specificity and efficacy of the agents were evaluated by MRI in a subcutaneous wound healing model and experimental glioma with Mrc1 +/+ without and with D-mannose treatment, Mrc1 +/-, and Mrc1 -/- mice, and in stroke. One-way ANOVA and two-way ANOVA tests were used for data analysis. P < 0.05 was considered statistically different. Results: Both in vitro fluorescence imaging with MR2-cy5, ICP-MS with Mann2-DTPA-Gd, and in vivo MRI in Mrc1 -/- mice confirmed the specificity of our approach. Mann2-DTPA-Gd MRI can track the changes of CD206+ macrophages at different stages of wound healing, correlating well with flow cytometry data using another anti-inflammatory macrophage marker (arginase-1). The specificity and efficacy of Mann2-DPTA-Gd were further validated in experimental glioma, in which Mann2-DTPA-Gd imaging detected CD206+ tumor-associated macrophages (TAMs), demonstrated significantly decreased signals in Mrc1 +/- mice and Mrc1 -/- mice, and tracked treatment changes in D-mannose-treated Mrc1 +/+ mice. Furthermore, Mann2-DTPA-Gd can report microglia/macrophages and correlate with histology in stroke. The more Gd-stable agent MannGdFish demonstrated similar efficacy as Mann2-DTPA-Gd in vivo with favorable biodistribution and pharmacokinetics. Conclusion: We have developed a fluorescent agent (MR2-cy5) and MRI agents (Mann2-DTPA-Gd and MannGdFish) with two mannose moieties that are highly specific to CD206 and can track CD206+ macrophages in disease models of wound healing, tumor, and neurological disease. Importantly, MannGdFish, with its high specificity, stability, favorable biodistribution, and pharmacokinetics, is a promising translational candidate to noninvasively monitor CD206+ macrophages in repair/regeneration and tumors in patients. In addition, with the specific binding motif to CD206, other imaging modalities and therapeutic agents could also be introduced for theranostic applications.

Inhibition of PIM kinase in tumor associated macrophages suppresses inflammasome activation and sensitizes prostate cancer to immunotherapy

Immunotherapy has changed the treatment paradigm for many types of cancer, but immune checkpoint inhibitors (ICIs) have not shown benefit in prostate cancer (PCa). Chronic inflammation contributes to the immunosuppressive prostate tumor microenvironment (TME) and is associated with poor response to ICIs. The primary source of inflammatory cytokine production is the inflammasome. Here, we identify PIM kinases as important regulators of inflammasome activation in tumor associated macrophages (TAMs). Analysis of clinical data from a cohort of treatment naïve, hormone responsive PCa patients revealed that tumors from patients with high PIM1/2/3 display an immunosuppressive TME characterized by high inflammation (IL-1β and TNFα) and a high density of repressive immune cells, most notably TAMs. Strikingly, macrophage-specific knockout of PIM reduced tumor growth in syngeneic models of prostate cancer. Transcriptional analyses indicate 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 PCa tumors to ICIs by increasing tumor suppressive TAMs and increasing the activation of cytotoxic T cells. Collectively, our data implicate macrophage PIM as a driver of inflammation that limits the potency of ICIs and provides preclinical evidence that PIM inhibitors are an effective strategy to improve the efficacy of immunotherapy in prostate cancer.

A tumour-associated macrophage-based signature for deciphering prognosis and immunotherapy response in prostate cancer

For the multistage progression of prostate cancer (PCa) and resistance to immunotherapy, tumour-associated macrophage is an essential contributor. Although immunotherapy is an important and promising treatment modality for cancer, most patients with PCa are not responsive towards it. In addition to exploring new therapeutic targets, it is imperative to identify highly immunotherapy-sensitive individuals. This research aimed to establish a signature risk model, which derived from the macrophage, to assess immunotherapeutic responses and predict prognosis. Data from the UCSC-XENA, GEO and TISCH databases were extracted for analysis. Based on both single-cell datasets and bulk transcriptome profiles, a macrophage-related score (MRS) consisting of the 10-gene panel was constructed using the gene set variation analysis. MRS was highly correlated with hypoxia, angiogenesis, and epithelial-mesenchymal transition, suggesting its potential as a risk indicator. Moreover, poor immunotherapy responses and worse prognostic performance were observed in the high-MRS group of various immunotherapy cohorts. Additionally, APOE, one of the constituent genes of the MRS, affected the polarisation of macrophages. In particular, the reduced level of M2 macrophage and tumour progression suppression were observed in PCa xenografts which implanted in Apolipoprotein E-knockout mice. The constructed MRS has the potential as a robust prognostic prediction tool, and can aid in the treatment selection of PCa, especially immunotherapy options.

Unveiling the Inflammatory Landscape of Recurrent Glioblastoma through Histological-Based Assessments

The glioblastoma (GBM) tumor microenvironment consists of a heterogeneous mixture of neoplastic and non-neoplastic cells, including immune cells. Tumor recurrence following standard-of-care therapy results in a rich landscape of inflammatory cells throughout the glioma-infiltrated cortex. Immune cells consisting of glioma-associated macrophages and microglia (GAMMs) overwhelmingly constitute the bulk of the recurrent glioblastoma (rGBM) microenvironment, in comparison to the highly cellular and proliferative tumor microenvironment characteristic of primary GBM. These immune cells dynamically interact within the tumor microenvironment and can contribute to disease progression and therapy resistance while also providing novel targets for emerging immunotherapies. Within these varying contexts, histological-based assessments of immune cells in rGBM, including immunohistochemistry (IHC) and immunofluorescence (IF), offer a critical way to visualize and examine the inflammatory landscape. Here, we exhaustively review the available body of literature on the inflammatory landscape in rGBM as identified through histological-based assessments. We highlight the heterogeneity of immune cells throughout the glioma-infiltrated cortex with a focus on microglia and macrophages, drawing insights from canonical and novel immune-cell histological markers to estimate cell phenotypes and function. Lastly, we discuss opportunities for immunomodulatory treatments aiming to harness the inflammatory landscape in rGBM.

Disrupting prostate cancer research: Challenge accepted; report from the 2023 Coffey-Holden Prostate Cancer Academy Meeting

INTRODUCTION

The 2023 Coffey-Holden Prostate Cancer Academy (CHPCA) Meeting, themed "Disrupting Prostate Cancer Research: Challenge Accepted," was convened at the University of California, Los Angeles, Luskin Conference Center, in Los Angeles, CA, from June 22 to 25, 2023.

METHODS

The 2023 marked the 10th Annual CHPCA Meeting, a discussion-oriented scientific think-tank conference convened annually by the Prostate Cancer Foundation, which centers on innovative and emerging research topics deemed pivotal for advancing critical unmet needs in prostate cancer research and clinical care. The 2023 CHPCA Meeting was attended by 81 academic investigators and included 40 talks across 8 sessions.

RESULTS

The central topic areas covered at the meeting included: targeting transcription factor neo-enhancesomes in cancer, AR as a pro-differentiation and oncogenic transcription factor, why few are cured with androgen deprivation therapy and how to change dogma to cure metastatic prostate cancer without castration, reducing prostate cancer morbidity and mortality with genetics, opportunities for radiation to enhance therapeutic benefit in oligometastatic prostate cancer, novel immunotherapeutic approaches, and the new era of artificial intelligence-driven precision medicine.

DISCUSSION

This article provides an overview of the scientific presentations delivered at the 2023 CHPCA Meeting, such that this knowledge can help in facilitating the advancement of prostate cancer research worldwide.

Sialic acid blockade inhibits the metastatic spread of prostate cancer to bone

BACKGROUND

Bone metastasis is a common consequence of advanced prostate cancer. Bisphosphonates can be used to manage symptoms, but there are currently no curative treatments available. Altered tumour cell glycosylation is a hallmark of cancer and is an important driver of a malignant phenotype. In prostate cancer, the sialyltransferase ST6GAL1 is upregulated, and studies show ST6GAL1-mediated aberrant sialylation of N-glycans promotes prostate tumour growth and disease progression.

METHODS

Here, we monitor ST6GAL1 in tumour and serum samples from men with aggressive prostate cancer and using in vitro and in vivo models we investigate the role of ST6GAL1 in prostate cancer bone metastasis.

FINDINGS

ST6GAL1 is upregulated in patients with prostate cancer with tumours that have spread to the bone and can promote prostate cancer bone metastasis in vivo. The mechanisms involved are multi-faceted and involve modification of the pre-metastatic niche towards bone resorption to promote the vicious cycle, promoting the development of M2 like macrophages, and the regulation of immunosuppressive sialoglycans. Furthermore, using syngeneic mouse models, we show that inhibiting sialylation can block the spread of prostate tumours to bone.

INTERPRETATION

Our study identifies an important role for ST6GAL1 and α2-6 sialylated N-glycans in prostate cancer bone metastasis, provides proof-of-concept data to show that inhibiting sialylation can suppress the spread of prostate tumours to bone, and highlights sialic acid blockade as an exciting new strategy to develop new therapies for patients with advanced prostate cancer.

FUNDING

Prostate Cancer Research and the Mark Foundation For Cancer Research, the Medical Research Council and Prostate Cancer UK.

Overexpression of Fibroblast Activation Protein (FAP) in stroma of proliferative inflammatory atrophy (PIA) and primary adenocarcinoma of the prostate

Fibroblast activation protein (FAP) is a serine protease upregulated at sites of tissue remodeling and cancer that represents a promising therapeutic and molecular imaging target. In prostate cancer, studies of FAP expression using tissue microarrays are conflicting, such that its clinical potential is unclear. Furthermore, little is known regarding FAP expression in benign prostatic tissues. Here we demonstrated, using a novel iterative multiplex IHC assay in standard tissue sections, that FAP was nearly absent in normal regions, but was increased consistently in regions of proliferative inflammatory atrophy (PIA). In carcinoma, FAP was expressed in all cases, but was highly heterogeneous. High FAP levels were associated with increased pathological stage and cribriform morphology. We verified that FAP levels in cancer correlated with CD163+ M2 macrophage density. In this first report to quantify FAP protein in benign prostate and primary tumors, using standard large tissue sections, we clarify that FAP is present in all primary prostatic carcinomas, supporting its potential clinical relevance. The finding of high levels of FAP within PIA supports the injury/regeneration model for its pathogenesis and suggests that it harbors a protumorigenic stroma. Yet, high levels of FAP in benign regions could lead to false positive FAP-based molecular imaging results in clinically localized prostate cancer.

Taurine Inhibits Ferroptosis Mediated by the Crosstalk between Tumor Cells and Tumor-Associated Macrophages in Prostate Cancer

Tumor-associated macrophages (TAMs) play an essential role in tumor therapeutic resistance. Although the lethal effect of ferroptosis on tumor cells is well reported, how TAMs inhibit the effect of ferroptosis in tumors has not been clearly defined. In this study, it is demonstrated that TAM-secreted taurine suppresses ferroptosis in prostate cancer (PCa) by activating the Liver X receptor alpha/Stearoyl-Coenzyme A desaturase 1 (LXRα/SCD1) pathway. Blocking taurine intake via inhibition of taurine transporter TauT restores the sensitivity to ferroptosis in tumors. Furthermore, LXRα activates the transcription of both miR-181a-5p and its binding protein FUS to increase the recruitment of miR-181a-5p in tumor-derived extracellular vesicles (EVs). It is observed that macrophages appear to be recipient cells of the miR-181a-5p-enriched EVs. Intake of miR-181a-5p in macrophages promotes their M2 polarization and enhances the taurine export by inhibiting expression of its target gene lats1, which in turn inactivates the hippo pathway and results in a Yes-associated protein (YAP) nuclear translocation for transcriptional activation of both M2 polarization-related genes such as ARG1 and CD163 and the taurine transport gene TauT. Taken together, the findings indicate a reciprocal interaction between PCa cells and TAMs as a positive feedback-loop to repress ferroptosis in PCa, mediated by TAM-secreted taurine and tumor EV-delivered miR-181a-5p.

SPOP Mutations Target STING1 Signaling in Prostate Cancer and Create Therapeutic Vulnerabilities to PARP Inhibitor-Induced Growth Suppression

PURPOSE

Speckle-type POZ protein (SPOP) is important in DNA damage response (DDR) and maintenance of genomic stability. Somatic heterozygous missense mutations in the SPOP substrate-binding cleft are found in up to 15% of prostate cancers. While mutations in SPOP predict for benefit from androgen receptor signaling inhibition (ARSi) therapy, outcomes for patients with SPOP-mutant (SPOPmut) prostate cancer are heterogeneous and targeted treatments for SPOPmut castrate-resistant prostate cancer (CRPC) are lacking.

EXPERIMENTAL DESIGN

Using in silico genomic and transcriptomic tumor data, proteomics analysis, and genetically modified cell line models, we demonstrate mechanistic links between SPOP mutations, STING signaling alterations, and PARP inhibitor vulnerabilities.

RESULTS

We demonstrate that SPOP mutations are associated with upregulation of a 29-gene noncanonical (NC) STING (NC-STING) signature in a subset of SPOPmut, treatment-refractory CRPC patients. We show in preclinical CRPC models that SPOP targets and destabilizes STING1 protein, and prostate cancer-associated SPOP mutations result in upregulated NC-STING-NF-κB signaling and macrophage- and tumor microenvironment (TME)-facilitated reprogramming, leading to tumor cell growth. Importantly, we provide in vitro and in vivo mechanism-based evidence that PARP inhibitor (PARPi) treatment results in a shift from immunosuppressive NC-STING-NF-κB signaling to antitumor, canonical cGAS-STING-IFNβ signaling in SPOPmut CRPC and results in enhanced tumor growth inhibition.

CONCLUSIONS

We provide evidence that SPOP is critical in regulating immunosuppressive versus antitumor activity downstream of DNA damage-induced STING1 activation in prostate cancer. PARPi treatment of SPOPmut CRPC alters this NC-STING signaling toward canonical, antitumor cGAS-STING-IFNβ signaling, highlighting a novel biomarker-informed treatment strategy for prostate cancer.

A tumor-associated macrophages related model for predicting biochemical recurrence and tumor immune environment in prostate cancer

OBJECTIVE

To identify tumor-associated macrophages (TAMs) related molecular subtypes and develop a TAMs related prognostic model for prostate cancer (PCa).

METHODS

Consensus clustering analysis was used to identify TAMs related molecular clusters. A TAMs related prognostic model was developed using univariate and multivariate Cox analysis.

RESULTS

Three TAMs related molecular clusters were identified and were confirmed to be associated with prognosis, clinicopathological characteristics, PD-L1 expression levels and tumor microenvironment. A TAMs related prognostic model was constructed. Patients in low-risk group all showed a more appreciable biochemical recurrence-free survival (BCRFS) than patients in high-risk group in train cohort, test cohort, entire TCGA cohort and validation cohort. SLC26A3 attenuated progression of PCa and prevented macrophage polarizing to TAMs phenotype, which was initially verified.

CONCLUSIONS

We successfully identified molecular clusters related to TAMs. Additionally, we developed a prognostic model involving TAMs that exhibits excellent predictive performance for biochemical recurrence-free survival in PCa.

Androgen receptor blockade resistance with enzalutamide in prostate cancer results in immunosuppressive alterations in the tumor immune microenvironment

BACKGROUND

Emerging data suggest that patients with enzalutamide-treated prostate cancer with increased programmed death-ligand 1 (PD-L1) expression may benefit from anti-PD-L1 treatment. Unfortunately, the Phase III IMbassador250 clinical trial revealed that the combination of atezolizumab (a PD-L1 inhibitor) and enzalutamide failed to extend overall survival in patients with castration-resistant prostate cancer (CRPC). However, the mechanisms underlying treatment failure remain unknown.

METHODS

Human CRPC C4-2B cells and murine Myc-CaP cells were chronically exposed to increasing concentrations of enzalutamide and the cells resistant to enzalutamide were referred to as C4-2B MDVR and Myc-CaP MDVR, respectively. The mechanisms of action in drug-resistant prostate cancer cells were determined using RNA sequencing analyses, RNA interference, real-time PCR, western blotting, and co-culturing technologies. Myc-CaP and Myc-CaP MDVR tumors were established in syngeneic FVB mice, and tumor-infiltrating leukocytes were isolated after enzalutamide treatment. The stained immune cells were determined by flow cytometry, and the data were analyzed using FlowJo.

RESULTS

Immune-related signaling pathways (interferon alpha/gamma response, inflammatory response, and cell chemotaxis) were suppressed in human enzalutamide-resistant prostate cancer cells. PD-L1 was overexpressed and negatively regulated by androgen receptor signaling in resistant cells and patient with CRPC cohorts. Enzalutamide treatment decreased CD8+ T-cell numbers but increased monocytic myeloid-derived suppressor cell (M-MDSC) populations and PD-L1 expression within murine Myc-CaP tumors. Similarly, chemotaxis and immune response-regulating signaling pathways were suppressed, and PD-L1 expression was also increased using enzalutamide-resistant Myc-CaP MDVR cells. Notably, MDSC populations were significantly increased in Myc-CaP MDVR orthotopic tumors compared with those in Myc-CaP parental tumors. Co-culturing bone marrow cells with Myc-CaP MDVR cells significantly promoted MDSC differentiation and shifted towards M2 macrophage skewing.

CONCLUSIONS

Our study suggests that immunosuppressive signaling can be promoted directly by enzalutamide-resistant prostate cancer cells and may be a potential means by which the efficacy of immune checkpoint inhibitors in enzalutamide-resistant prostate cancer is diminished.

TRIM28 promotes luminal cell plasticity in a mouse model of prostate cancer

The Tripartite motif-containing 28 (TRIM28) transcriptional cofactor is significantly upregulated in high-grade and metastatic prostate cancers. To study the role of TRIM28 in prostate cancer progression in vivo, we generated a genetically-engineered mouse model, combining prostate-specific inactivation of Trp53, Pten and Trim28. Trim28 inactivated NPp53T mice developed an inflammatory response and necrosis in prostate lumens. By conducting single-cell RNA sequencing, we found that NPp53T prostates had fewer luminal cells resembling proximal luminal lineage cells, which are cells with progenitor activity enriched in proximal prostates and prostate invagination tips in wild-type mice with analogous populations in human prostates. However, despite increased apoptosis and reduction of cells expressing proximal luminal cell markers, we found that NPp53T mouse prostates evolved and progressed to invasive prostate carcinoma with a shortened overall survival. Altogether, our findings suggest that TRIM28 promotes expression of proximal luminal cell markers in prostate tumor cells and provides insights into TRIM28 function in prostate tumor plasticity.

Radiotherapy Induces Innate Immune Responses in Patients Treated for Prostate Cancers

PURPOSE

Radiotherapy is a curative therapeutic modality used to treat cancers as a single agent or in combination with surgery and chemotherapy. Advanced radiotherapy technologies enable treatment with large fractions and highly conformal radiation doses to effect free-radical damage to cellular DNA leading to cell-cycle arrest, cell death, and innate immune response (IIR) stimulation.

EXPERIMENTAL DESIGN

To understand systemic clinical responses after radiation exposure, proteomic and metabolomic analyses were performed on plasma obtained from patients with cancer at intervals after prostate stereotactic body radiotherapy. Pathway and multivariate analyses were used to delineate molecular alterations following radiotherapy and its correlation with clinical outcomes.

RESULTS

DNA damage response increased within the first hour after treatment and returned to baseline by 1 month. IIR signaling also increased within 1 hour of treatment but persisted for up to 3 months thereafter. Furthermore, robust IIR and metabolite elevations, consistent with an early proinflammatory M1-mediated innate immune activation, were observed in patients in remission, whereas patients experiencing prostate serum antigen-determined disease progression demonstrated less robust immune responses and M2-mediated metabolite elevations.

CONCLUSIONS

To our knowledge, these data are the first report of longitudinal proteomic and metabolomic molecular responses in patients after radiotherapy for cancers. The data supports innate immune activation as a critical clinical response of patients receiving radiotherapy for prostate cancer. Furthermore, we propose that the observed IIR may be generalized to the treatment of other cancer types, potentially informing multidisciplinary therapeutic strategies for cancer treatment.

Association between Intratumoral CD8+ T Cells with FoxP3+ and CD163+ Cells: A Potential Immune Intrinsic Negative Feedback Mechanism for Acquired Immune Resistance

Acquired immune resistance (AIR) describes a situation in which cancer patients who initially responded clinically to immunotherapies, after a certain period of time, progress with their disease. Considering that AIR represents a feedback response of the tumor against the immune attack generated during the course of immunotherapies, it is conceivable that AIR may also occur before treatment initiation as a mechanism to escape endogenous adaptive antitumor immunity (EAAI). In the present study, we assessed the EAAI in paraffin-embedded breast primary tumor tissue samples and drew correlations with the clinical outcomes. In particular, we analyzed densities of CD8+ cells as elements mediating antitumor cytotoxicity, and of CD163+ and FoxP3+ cells as suppressor elements. We found a direct correlation between the densities of CD8+ cells and of CD163+ and/or FoxP3+ cells in the vast majority of patients' tumors. Importantly, the vast majority of patients whose tumors were overpopulated by CD8+ cells developed AIR, which was characterized by high intratumoral CD163+ and/or FoxP3+ cell densities and reduced overall survival (OS). We also showed that AIR depends on the levels of CD8+ cell-ratios in the tumor center to the invasive margin. Our data suggest that tumors develop AIR only when under a robust endogenous immune pressure.

Tumor Cell-Surface Binding of Immune Stimulating Polymeric Glyco-Adjuvant via Cysteine-Reactive Pyridyl Disulfide Promotes Antitumor Immunity

Immune stimulating agents like Toll-like receptor 7 (TLR7) agonists induce potent antitumor immunity but are limited in their therapeutic window due to off-target immune activation. Here, we developed a polymeric delivery platform that binds excess unpaired cysteines on tumor cell surfaces and debris to adjuvant tumor neoantigens as an in situ vaccine. The metabolic and enzymatic dysregulation in the tumor microenvironment produces these exofacial free thiols, which can undergo efficient disulfide exchange with thiol-reactive pyridyl disulfide moieties upon intratumoral injection. These functional monomers are incorporated into a copolymer with pendant mannose groups and TLR7 agonists to target both antigen and adjuvant to antigen presenting cells. When tethered in the tumor, the polymeric glyco-adjuvant induces a robust antitumor response and prolongs survival of tumor-bearing mice, including in checkpoint-resistant B16F10 melanoma. The construct additionally reduces systemic toxicity associated with clinically relevant small molecule TLR7 agonists.

Targeting interleukin 4 receptor alpha on tumor-associated macrophages reduces the pro-tumor macrophage phenotype

Tumor-associated macrophages (TAMs) are an abundant tumor-promoting cell type in the tumor microenvironment (TME). Most TAMs exhibit a pro-tumor M2-like phenotype supportive of tumor growth, immune evasion, and metastasis. IL-4 and IL-13 are major cytokines that polarize macrophages to an M2 subset and share a common receptor, IL-4 receptor alpha (IL-4R alpha). Treatment of human ex vivo polarized M2 macrophages and M2 macrophage precursors with IL-4R alpha antagonist antibody Dupilumab (Dupixent^Ⓡ) reduces M2 macrophage features, including a shift in cell surface marker protein expression and gene expression. In animal models of prostate cancer, both pharmacologic inhibition of IL-4R alpha and genetic deletion of IL-4R alpha utilizing an Il4ra -/- mouse model result in decreased CD206 on TAMs. These data support IL-4R alpha as a target to reduce the pro-tumor, M2-like macrophage phenotype as a novel adjunct cancer therapy.

The Roles of Tumor-Associated Macrophages in Prostate Cancer

The morbidity of prostate cancer (PCa) is rising year by year, and it has become the primary cause of tumor-related mortality in males. It is widely accepted that macrophages account for 50% of the tumor mass in solid tumors and have emerged as a crucial participator in multiple stages of PCa, with the huge potential for further treatment. Oftentimes, tumor-associated macrophages (TAMs) in the tumor microenvironment (TME) behave like M2-like phenotypes that modulate malignant hallmarks of tumor lesions, ranging from tumorigenesis to metastasis. Several clinical studies indicated that mean TAM density was higher in human PCa cores versus benign prostatic hyperplasia (BPH), and increased biopsy TAM density potentially predicts worse clinicopathological characteristics as well. Therefore, TAM represents a promising target for therapeutic intervention either alone or in combination with other strategies to halt the “vicious cycle,” thus improving oncological outcomes. Herein, we mainly focus on the fundamental aspects of TAMs in prostate adenocarcinoma, while reviewing the mechanisms responsible for macrophage recruitment and polarization, which has clinical translational implications for the exploitation of potentially effective therapies against TAMs.

Prostate cancer immunotherapy: a review of recent advancements with novel treatment methods and efficacy

Immunotherapy remains to be an appealing treatment option for prostate cancer with some documented promise. Prostate cancer is traditionally considered as an immunologically "cold" tumor with low tumor mutation burden, low expression of PD-L1, sparse T-cell infiltration, and a immunosuppressive tumor microenvironment (TME). Sipuleucel-T (Provenge) is the first FDA approved immunotherapeutic agent for the treatment of asymptomatic or minimally symptomatic metastatic castrate resistant prostate cancer (mCRPC); demonstrating a benefit in overall survival. However various clinical trials by immune checkpoint inhibitors (ICIs) and their combinations with other drugs have shown limited responses in mCRPC. Up to now, only a small subset of patients with mismatch repair deficiency/microsatellite instability high and CDK12 mutations can clinically benefit from ICIs and/or their combinations with other agents, such as DNA damage agents. The existence of a large heterogeneity in genomic alterations and a complex TME in prostate cancer suggests the need for identifying new immunotherapeutic targets. As well as designing personalized immunotherapy strategies based on patient-specific molecular signatures. There is also a need to adjust strategies to overcome histologic barriers such as tissue hypoxia and dense stroma. The racial differences of immunological responses between men of diverse ethnicities also merit further investigation to improve the efficacy of immunotherapy and better patient selection in prostate cancer.

Comprehensive Analysis of m5C Methylation Regulatory Genes and Tumor Microenvironment in Prostate Cancer

Background

5-Methylcytidine (m5C) methylation is an emerging epigenetic modification in recent years, which is associated with the development and progression of various cancers. However, the prognostic value of m5C regulatory genes and the correlation between m5C methylation and the tumor microenvironment (TME) in prostate cancer remain unknown.

Methods

In the current study, the genetic and transcriptional alterations and prognostic value of m5C regulatory genes were investigated in The Cancer Genome Atlas and Gene Expression Omnibus datasets. Then, an m5C prognostic model was established by LASSO Cox regression analysis. Gene set variation analyses (GSVA), gene set enrichment analysis (GSEA), clinical relevance, and TME analyses were conducted to explain the biological functions and quantify the TME scores between high-risk and low-risk subgroups. m5C regulatory gene clusters and m5C immune subtypes were identified using consensus unsupervised clustering analysis. The Cell-type Identification By Estimating Relative Subsets of RNA Transcripts algorithm was used to calculate the contents of immune cells.

Results

TET3 was upregulated at transcriptional levels in PCa compared with normal tissues, and a high TET3 expression was associated with poor prognosis. An m5C prognostic model consisting of 3 genes (NSUN2, TET3, and YBX1) was developed and a nomogram was constructed for improving the clinical applicability of the model. Functional analysis revealed the enrichment of pathways and the biological processes associated with RNA regulation and immune function. Significant differences were also found in the expression levels of m5C regulatory genes, TME scores, and immune cell infiltration levels between different risk subgroups. We identified two distinct m5C gene clusters and found their correlation with patient prognosis and immune cell infiltration characteristics. Naive B cells, CD8+ T cells, M1 macrophages and M2 macrophages were obtained and 2 m5C immune subtypes were identified. CTLA4, NSUN6, TET1, and TET3 were differentially expressed between immune subtypes. The expression of CTLA4 was found to be correlated with the degree of immune cell infiltration.

Conclusions

Our comprehensive analysis of m5C regulatory genes in PCa demonstrated their potential roles in the prognosis, clinical features, and TME. These findings may improve our understanding of m5C regulatory genes in the tumor biology of PCa.

Deep Learning-Based Multi-Omics Integration Robustly Predicts Relapse in Prostate Cancer

Objective

Post-operative biochemical relapse (BCR) continues to occur in a significant percentage of patients with localized prostate cancer (PCa). Current stratification methods are not adequate to identify high-risk patients. The present study exploits the ability of deep learning (DL) algorithms using the H2O package to combine multi-omics data to resolve this problem.

Methods

Five-omics data from 417 PCa patients from The Cancer Genome Atlas (TCGA) were used to construct the DL-based, relapse-sensitive model. Among them, 265 (63.5%) individuals experienced BCR. Five additional independent validation sets were applied to assess its predictive robustness. Bioinformatics analyses of two relapse-associated subgroups were then performed for identification of differentially expressed genes (DEGs), enriched pathway analysis, copy number analysis and immune cell infiltration analysis.

Results

The DL-based model, with a significant difference (P = 6e-9) between two subgroups and good concordance index (C-index = 0.767), were proven to be robust by external validation. 1530 DEGs including 678 up- and 852 down-regulated genes were identified in the high-risk subgroup S2 compared with the low-risk subgroup S1. Enrichment analyses found five hallmark gene sets were up-regulated while 13 were down-regulated. Then, we found that DNA damage repair pathways were significantly enriched in the S2 subgroup. CNV analysis showed that 30.18% of genes were significantly up-regulated and gene amplification on chromosomes 7 and 8 was significantly elevated in the S2 subgroup. Moreover, enrichment analysis revealed that some DEGs and pathways were associated with immunity. Three tumor-infiltrating immune cell (TIIC) groups with a higher proportion in the S2 subgroup (p = 1e-05, p = 8.7e-06, p = 0.00014) and one TIIC group with a higher proportion in the S1 subgroup (P = 1.3e-06) were identified.

Conclusion

We developed a novel, robust classification for understanding PCa relapse. This study validated the effectiveness of deep learning technique in prognosis prediction, and the method may benefit patients and prevent relapse by improving early detection and advancing early intervention.

PD-L1 blockade restores CAR T cell activity through IFN-γ-regulation of CD163+ M2 macrophages

BACKGROUND

The immune suppressive tumor microenvironment (TME) that inhibits T cell infiltration, survival, and antitumor activity has posed a major challenge for developing effective immunotherapies for solid tumors. Chimeric antigen receptor (CAR)-engineered T cell therapy has shown unprecedented clinical response in treating patients with hematological malignancies, and intense investigation is underway to achieve similar responses with solid tumors. Immunologically cold tumors, including prostate cancers, are often infiltrated with abundant tumor-associated macrophages (TAMs), and infiltration of CD163+ M2 macrophages correlates with tumor progression and poor responses to immunotherapy. However, the impact of TAMs on CAR T cell activity alone and in combination with TME immunomodulators is unclear.

METHODS

To model this in vitro, we utilized a novel co-culture system with tumor cells, CAR T cells, and polarized M1 or M2 macrophages from CD14+ peripheral blood mononuclear cells collected from healthy human donors. Tumor cell killing, T cell activation and proliferation, and macrophage phenotypes were evaluated by flow cytometry, cytokine production, RNA sequencing, and functional blockade of signaling pathways using antibodies and small molecule inhibitors. We also evaluated the TME in humanized mice following CAR T cell therapy for validation of our in vitro findings.

RESULTS

We observed inhibition of CAR T cell activity with the presence of M2 macrophages, but not M1 macrophages, coinciding with a robust induction of programmed death ligand-1 (PD-L1) in M2 macrophages. We observed similar PD-L1 expression in TAMs following CAR T cell therapy in the TME of humanized mice. PD-L1, but not programmed cell death protein-1, blockade in combination with CAR T cell therapy altered phenotypes to more M1-like subsets and led to loss of CD163+ M2 macrophages via interferon-γ signaling, resulting in improved antitumor activity of CAR T cells.

CONCLUSION

This study reveals an alternative mechanism by which the combination of CAR T cells and immune checkpoint blockade modulates the immune landscape of solid tumors to enhance therapeutic efficacy of CAR T cells.

Multiplex immunohistochemical phenotyping of T cells in primary prostate cancer

BACKGROUND

Most prostate cancers are "immune cold" and poorly responsive to immune checkpoint inhibitors. However, the mechanisms responsible for the lack of a robust antitumor adaptive immune response in the prostate are poorly understood, which hinders the development of novel immunotherapeutic approaches.

AIMS

Most inflammatory infiltrates in the prostate are centered around benign glands and stroma, which can confound the molecular characterization of the antitumor immune response. We sought to analytically validate a chromogenic-based multiplex immunohistochemistry (IHC) approach applicable to whole slide digital image analysis to quantify T cell subsets from the tumor microenvironment of primary prostatic adenocarcinomas. As an initial application, we tested the hypothesis that PTEN loss leads to an altered antitumor immune response by comparing matched regions of tumors within the same individual with and without PTEN loss.

MATERIALS & METHODS

Using the HALO Image Analysis Platform (Indica Labs), we trained a classifier to quantify the densities of eight T cell phenotypes separately in the tumor epithelial and stromal subcompartments.

RESULTS

The iterative chromogenic approach using 7 different antibodies on the same slide provides highly similar findings to results using individually stained slides with single antibodies. Our main findings in carcinomas (benign removed) include the following: i) CD4+ T cells are present at higher density than CD8+ T cells; ii) all T cell subsets are present at higher densities in the stromal compartment compared to the epithelial tumor compartment; iii) most CD4+ and CD8+ T cells are PD1+; iv) cancer foci with PTEN loss harbored increased numbers of T cells compared to regions without PTEN loss, in both stromal and epithelial compartments; and v) the increases in T cells in PTEN loss regions were associated with ERG gene fusion status.

DISCUSSION

This modular approach can apply to any IHC-validated antibody combination and sets the groundwork for more detailed spatial analyses.

CONCLUSION

Iterative chromogenic IHC can be used for whole slide analysis of prostate tissue samples and can complement transcriptomic results including those using single cell and spatial genomic approaches.

Sex steroid modulation of macrophages within the prostate tumor microenvironment

BACKGROUND

The role of androgens and other sex steroids is known to influence the prognosis and progression of prostate cancer through different disease states. While androgens are generally regarded as immunosuppressive and estrogens as inflammatory, the specific influence of sex steroids on the immune microenvironment of prostate tumors remains incompletely understood.

MATERIAL AND METHODS

In this study, we evaluate the link between sex steroids and prostate cancer immune cells, particularly macrophages. Using in vitro and in vivo models, as well as ex vivo culture of patient prostate tissue, we evaluated the influence of androgen, estrogen, and progesterone on immune cells of the prostate microenvironment.

RESULTS

In vitro, we observed sex steroids induced indirect changes on prostate cancer cell proliferation via THP-1 derived macrophages, but no clear changes were induced using human monocyte derived macrophages. Comparing immunohistochemistry for immunosuppressive macrophage marker CD163 with concomitant circulating sex steroids from the same patients, we observed a correlation with higher dehydroepiandrosterone (DHEA)-sulfate and estrone-sulfate levels associated with higher prostate CD163 expression. Similar relationships between DHEA and CD163 levels were observed in ex vivo cultured prostate biopsies. Finally, in a murine prostate cancer model of long-term sex steroids we observed significant differences in tumor growth in mice implanted with estrogen and DHEA diffusion tubes.

CONCLUSIONS

Our results highlight the complex influence of sex steroids on the immune cell composition of prostate tumors. Understanding this biology may help to further personalized therapy and improve patient outcomes.

Inflammation and Prostate Cancer: A Multidisciplinary Approach to Identifying Opportunities for Treatment and Prevention

Prostate cancer is a major cause of disease for men globally. Inflammation, an established hallmark of cancer, is frequently observed in the prostate, though its contribution to prostate cancer risks and outcomes is not fully understood. Prostate cancer is biologically and clinically heterogeneous, and there is now evidence that inflammation and immunological characteristics vary by the genomic and mutational landscape of the tumor. Moreover, it is now recognized that risk factor profiles vary between tumor subgroups, as defined by histopathological and molecular features. Here, we provide a review centered around the relationship between inflammation and prostate cancer, with a consideration of molecular tumor features and a particular focus on the advanced and lethal stages of disease. We summarize findings from epidemiological studies of the etiology and role of inflammation in prostate cancer. We discuss the pathology of prostate inflammation, and consider approaches for assessing the tumor immune microenvironment in epidemiological studies. We review emerging clinical therapies targeting immune biology within the context of prostate cancer. Finally, we consider potentially modifiable risk factors and corresponding lifestyle interventions that may affect prostate inflammation, impacting outcomes. These emerging insights will provide some hints for the development of treatment and prevention strategies for advanced and lethal prostate cancer.

Impact of HPV status on immune responses in head and neck squamous cell carcinoma

The main objective of our study was to understand the impact of immune cell composition and the tumor-reactivity of tumor infiltrating lymphocytes (TIL) in HPV-positive (HPV⁺) and HPV-negative (HPV^-) head and neck squamous cell carcinoma (HNSCC). TIL cultures were established from primary HNSCC tumors, the T cell subsets were phenotypically characterized using flow cytometry, and Interferon (IFN)-γ ELISA assay was used to determine TIL function. NanoString Immune Profiler was used to determine an immune signature by HPV-status, and multiplex immunohistochemistry (MIHC) was used to quantify immune cell distributions and their spatial relationships. Results showed that HPV⁺ and HPV^- HNSCC had similar capacity to expand IFN-γ reactive TIL populations, and these TIL populations had similar characteristics. NanoString analysis revealed increased differential expression of genes related to B cell functions in HPV⁺ HNSCC, which were significant at a Benjamini-Yekutieli adjusted p-value of < 0.001. MIHC also displayed increased CD8⁺ T cell and CD19/CD20⁺ B cell densities in the tumor region of HPV⁺ HNSCC as opposed to HPV^- HNSCC (p < 0.01). Increases in a combined metric of tumor B cell content and stromal plasma cell content was associated with increased progression-free survival in HPV^- HNSCC patients treated with immune checkpoint inhibitor therapy (p = 0.03). In summary, TIL populations expanded from HPV⁺ and HPV^- HNSCC displayed similar IFN-γ reactivity. However, we identified a strong B-cell signature present within HPV⁺ HNSCC, and higher B and plasma cell content associated with improved PFS in HPV^- HNSCC patients treated with immune checkpoint inhibitors.

P2X4 purinergic receptors offer a therapeutic target for aggressive prostate cancer

Prostate cancer (PCa) remains a leading cause of cancer-related deaths in American men and treatment options for metastatic PCa are limited. There is a critical need to identify new mechanisms that contribute to PCa progression, that distinguish benign from lethal disease, and that have potential for therapeutic targeting. P2X4 belongs to the P2 purinergic receptor family that is commonly upregulated in cancer and is associated with poorer outcomes. We observed P2X4 protein expression primarily in epithelial cells of the prostate, a subset of CD66⁺ neutrophils, and most CD68⁺ macrophages. Our analysis of tissue microarrays representing 491 PCa cases demonstrated significantly elevated P2X4 expression in cancer- compared with benign-tissue spots, in prostatic intraepithelial neoplasia, and in PCa with ERG positivity or with PTEN loss. High-level P2X4 expression in benign tissues was likewise associated with the development of metastasis after radical prostatectomy. Treatment with the P2X4-specific agonist cytidine 5'-triphosphate (CTP) increased Transwell migration and invasion of PC3, DU145, and CWR22Rv1 PCa cells. The P2X4 antagonist 5-(3-bromophenyl)-1,3-dihydro-2H-benzofuro[3,2-e]-1,4-diazepin-2-one (5-BDBD) resulted in a dose-dependent decrease in viability of PC3, DU145, LNCaP, CWR22Rv1, TRAMP-C2, Myc-CaP, BMPC1, and BMPC2 cells and decreased DU145 cell migration and invasion. Knockdown of P2X4 attenuated growth, migration, and invasion of PCa cells. Finally, knockdown of P2X4 in Myc-CaP cells resulted in significantly attenuated subcutaneous allograft growth in FVB/NJ mice. Collectively, these data strongly support a role for the P2X4 purinergic receptor in PCa aggressiveness and identify P2X4 as a candidate for therapeutic targeting. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Subversion of infiltrating prostate macrophages to a mixed immunosuppressive tumor-associated macrophage phenotype

Tumor-associated macrophages (TAMs) support tumor progression within the tumor microenvironment (TME). Many questions remain as to the origin, development, and function of TAMs within the prostate TME. Evaluation of TAMs in prostate cancer (PCa) patients identified the immunosuppressive TAM marker CD163 in adjacent normal epithelium as an independent predictor of metastases or PCa death. Flow cytometry analyses identified prostate TAMs as frequently expressing both proinflammatory M1 (CCR7+) and immunosuppressive M2 (CD163+) markers. In vitro, we demonstrate PCa cells similarly subvert human M1 macrophages toward a mixed M1/M2 macrophage phenotype favoring tumor growth. Further the cytokine milieu-induced transition between immunosuppressive M2 to proinflammatory M1 (M2→M1) macrophages is abrogated by the presence of PCa cells. RNA sequencing suggests alterations in chemokine expression in prostate TAMs due to the presence of PCa cells. Together, our results suggest that prostate TAMs originate from inflammatory infiltrating macrophages, which are then reprogrammed mainly by PCa cells, but also the cytokine milieu. A better understanding of this subversion of macrophages within the prostate may lead to novel treatment strategies.

Immune cell infiltrates and prognosis in localized prostate cancer†

Multiple lines of evidence indicate that quantification of immune cell infiltrates in primary prostate cancer can predict outcomes after radical prostatectomy, including biochemical recurrence, metastasis, and death from prostate cancer. In a recent issue of The Journal of Pathology, Andersen et al explored the predictive value of cancer tissue infiltration of seven immune cell types (mast cells, M1 macrophages, M2 macrophages, B cells, T helper cells, cytotoxic T cells, and regulatory T cells) in association with biochemical recurrence after radical prostatectomy. In addition to reporting a potential association between cancer-infiltrating regulatory T cells and M1 and M2 macrophages and biochemical recurrence, the study also highlighted the use of multiplex digital pathology analyses to assess adverse predictors of prostate cancer outcomes. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Functionalized Nanoparticles Targeting Tumor-Associated Macrophages as Cancer Therapy

The tumor microenvironment (TME) plays a central role in regulating antitumor immune responses. As an important part of the TME, alternatively activated type 2 (M2) macrophages drive the development of primary and secondary tumors by promoting tumor cell proliferation, tumor angiogenesis, extracellular matrix remodeling and overall immunosuppression. Immunotherapy approaches targeting tumor-associated macrophages (TAMs) in order to reduce the immunosuppressive state in the TME have received great attention. Although these methods hold great potential for the treatment of several cancers, they also face some limitations, such as the fast degradation rate of drugs and drug-induced cytotoxicity of organs and tissues. Nanomedicine formulations that prevent TAM signaling and recruitment to the TME or deplete M2 TAMs to reduce tumor growth and metastasis represent encouraging novel strategies in cancer therapy. They allow the specific delivery of antitumor drugs to the tumor area, thereby reducing side effects associated with systemic application. In this review, we give an overview of TAM biology and the current state of nanomedicines that target M2 macrophages in the course of cancer immunotherapy, with a specific focus on nanoparticles (NPs). We summarize how different types of NPs target M2 TAMs, and how the physicochemical properties of NPs (size, shape, charge and targeting ligands) influence NP uptake by TAMs in vitro and in vivo in the TME. Furthermore, we provide a comparative analysis of passive and active NP-based TAM-targeting strategies and discuss their therapeutic potential.

Targeting the spectrum of immune checkpoints in prostate cancer

Introduction: The proven efficacy of the cellular vaccine sipuleucel-T in 2010 led to optimism about immunotherapeutic approaches for the treatment of prostate cancer. Some surmised that prostate cancer might be an ideal target for immune-mediated killing given that the prostate is not an essential organ and expresses unique proteins including prostate-specific antigen, prostate-specific membrane antigen, and prostatic acid phosphatase that could be targeted without side effects. Subsequently, antibodies that inhibit the T cell checkpoints PD1 and CTLA4 were shown to stimulate antitumor immune responses, leading to tumor regression in several cancer types. These therapies have since been tested in several studies as treatments for prostate cancer, but appear to have limited efficacy in molecularly unselected patients.Areas covered: In this review, we discuss these studies and evaluate features of prostate cancer and its host environment that may render it generally resistant to CTLA4 and PD1 blockade. We provide an overview of alternate immune checkpoints that may hold greater significance in this disease.Expert opinion: Combination therapies to target multiple layers of alternate immune checkpoints may be required for an effective immune response to prostate cancer. We discuss combination therapies currently being investigated.

Using ex vivo culture to assess dynamic phenotype changes in human prostate macrophages following exposure to therapeutic drugs

Within the prostate tumor microenvironment (TME) there are complex multi-faceted and dynamic communication occurring between cancer cells and immune cells. Macrophages are key cells which infiltrate and surround tumor cells and are recognized to significantly contribute to tumor resistance and metastases. Our understanding of their function in the TME is commonly based on in vitro and in vivo models, with limited research to confirm these model observations in human prostates. Macrophage infiltration was evaluated within the TME of human prostates after 72 h culture of fresh biopsies samples in the presence of control or enzalutamide. In addition to immunohistochemistry, an optimized protocol for multi-parametric evaluation of cellular surface markers was developed using flow cytometry. Flow cytometry parameters were compared to clinicopathological features. Immunohistochemistry staining for 19 patients with paired samples suggested enzalutamide increased the expression of CD163 relative to CD68 staining. Techniques to validate these results using flow cytometry of dissociated biopsies after 72 h of culture are described. In a second cohort of patients with Gleason grade group ≥ 3 prostate cancer, global macrophage expression of CD163 was unchanged with enzalutamide treatment. However, exploratory analyses of our results using multi-parametric flow cytometry for multiple immunosuppressive macrophage markers suggest subgroup changes as well as novel associations between circulating biomarkers like the neutrophil to lymphocyte ratio (NLR) and immune cell phenotype composition in the prostate TME. Further, we observed an association between B7–H3 expressing tumor-associated macrophages and the presence of intraductal carcinoma. The use of flow cytometry to evaluate ex vivo cultured prostate biopsies fills an important gap in our ability to understand the immune cell composition of the prostate TME. Our results highlight novel associations for further investigation.

Understanding the tumor-immune microenvironment in prostate cancer

PURPOSE OF REVIEW

This review aims to highlight recent advances in prostate cancer tumor-immune microenvironment research and summarize the state-of-the-art knowledge of immune checkpoint inhibitors in prostate cancer.

RECENT FINDINGS

Immune checkpoint inhibitors are the cornerstone of modern immunotherapy which have shown encouraging results across a spectrum of cancers. However, only limited survival benefit has been seen in patients with prostate cancer. Prostate cancer progression and its response to immunotherapies are strongly influenced by the tumor-immune microenvironment, whose feature can be summarized as low amounts of tumor-specific antigens, low frequency of tumor-infiltrating lymphocytes and high frequency of tumor-associated macrophages. To improve the therapeutic effect of immunotherapies, in recent years, many strategies have been applied, of which the most promising ones include the combination of multiple immunotherapeutic agents, the combination of an immunotherapeutic agent with other modalities in parallel or in sequential, and the development of biomarkers to find a subgroup of patients who may benefit the most from immunotherapeutic agents.

SUMMARY

The impact of immune content and specific immune cell types on prostate cancer biology is highly complex. Recent clinical trials have shed light on the optimal use of immunotherapies for prostate cancer.

Characterization of tumor-associated macrophages in prostate cancer transgenic mouse models

BACKGROUND

Tumor-associated macrophages (TAMs) are critical components of the tumor microenvironment (TME) in prostate cancer. Commonly used orthotopic models do not accurately reflect the complete TME of a human patient or the natural initiation and progression of a tumor. Therefore, genetically engineered mouse models are essential for studying the TME as well as advancing TAM-targeted therapies. Two common transgenic (TG) models of prostate cancer are Hi-Myc and transgenic adenocarcinoma of the mouse prostate (TRAMP), but the TME and TAM characteristics of these models have not been well characterized.

METHODS

To advance the Hi-Myc and TRAMP models as tools for TAM studies, macrophage infiltration and characteristics were assessed using histopathologic, flow cytometric, and expression analyses in these models at various timepoints during tumor development and progression.

RESULTS

In both Hi-Myc and TRAMP models, macrophages adopt a more pro-tumor phenotype in higher histological grade tumors and in older prostate tissue. However, the Hi-Myc and TRAMP prostates differ in their macrophage density, with Hi-Myc tumors exhibiting increased macrophage density and TRAMP tumors exhibiting decreased macrophage density compared to age-matched wild type mice.

CONCLUSIONS

The macrophage density and the adenocarcinoma cancer subtype of Hi-Myc appear to better mirror patient tumors, suggesting that the Hi-Myc model is the more appropriate in vivo TG model for studying TAMs and TME-targeted therapies.

Development and Validation of Novel Biomarkers Related to M2 Macrophages Infiltration by Weighted Gene Co-Expression Network Analysis in Prostate Cancer

M2-tumor-associated macrophages (TAMs) work as a promoter in the processes of bone metastases, chemotherapy resistance, and castration resistance in prostate cancer (PCa), but how M2-TAMs affect PCa has not been fully understood. In this study, we analyzed the proportion of tumor-infiltrating immune cells using the CIBERSORT algorithm, based on samples from the Cancer Genome Atlas database. Then we performed weighted gene co-expression network analysis to examine the modules concerning infiltrated M2-TAMs. Gene Ontology analysis and pathway enrichment analysis were performed for functional annotation and a protein–protein interaction network was constructed. The International Cancer Genomics Consortium cohort was used as a validation cohort. The red module showed the most correlation with M2-TAMs in PCa. Biological processes and pathways were mainly associated with the immune-related processes, as revealed by functional annotation. Four hub genes were screened: ACSL1, DLGAP5, KIF23 and NCAPG. Further validation showed that the four hub genes had a higher expression level in tumor tissues than that in normal tissues, and they were good prognosis biomarkers for PCa. In conclusion, these findings contribute to understanding the underlying molecular mechanisms of how M2-TAMs affect PCa, and looking for the potential biomarkers and therapeutic targets for PCa patients.

The interplay of growth differentiation factor 15 (GDF15) expression and M2 macrophages during prostate carcinogenesis

M2 (tumor-supportive) macrophages may upregulate growth differentiation factor 15 (GDF15), which is highly expressed in prostate tumors, but the combined utility of these markers as prognostic biomarkers are unclear. We retrospectively studied 90 prostate cancer cases that underwent radical prostatectomy as their primary treatment and were followed for biochemical recurrence (BCR). These cases also had a benign prostate biopsy at least 1 year or more before their prostate cancer surgery. Using computer algorithms to analyze digitalized immunohistochemically stained slides, GDF15 expression and the presence of M2 macrophages based on the relative density of CD204- and CD68-positive macrophages were measured in prostate: (i) benign biopsy, (ii) cancer and (iii) tumor-adjacent benign (TAB) tissue. Both M2 macrophages (P = 0.0004) and GDF15 (P < 0.0001) showed significant inter-region expression differences. Based on a Cox proportional hazards model, GDF15 expression was not associated with BCR but, in men where GDF15 expression differences between cancer and TAB were highest, the risk of BCR was significantly reduced (hazard ratio = 0.26; 95% confidence interval = 0.09-0.94). In addition, cases with high levels of M2 macrophages in prostate cancer had almost a 5-fold increased risk of BCR (P = 0.01). Expression of GDF15 in prostate TAB was associated with M2 macrophage levels in both prostate cancer and TAB and appeared to moderate M2-macrophage-associated BCR risk. In summary, the relationship of GDF15 expression and CD204-positive M2 macrophage levels is different in a prostate tumor environment compared with an earlier benign biopsy and, collectively, these markers may predict aggressive disease.

High Monocyte Count and Expression of S100A9 and S100A12 in Peripheral Blood Mononuclear Cells Are Associated with Poor Outcome in Patients with Metastatic Prostate Cancer

Increasing evidence indicates calcium-binding S100 protein involvement in inflammation and tumor progression. In this prospective study, we evaluated the mRNA levels of two members of this family, S100A9 and S100A12, in peripheral blood mononuclear cells (PBMCs) in a cohort of 121 prostate cancer patients using RT-PCR. Furthermore, monocyte count was determined by flow cytometry. By stratifying patients into different risk groups, according to TNM stage, Gleason score and PSA concentration at diagnosis, expression of S100A9 and S100A12 was found to be significantly higher in patients with metastases compared to patients without clinically detectable metastases. In line with this, we observed that the protein levels of S100A9 and S100A12 in plasma were higher in patients with advanced disease. Importantly, in patients with metastases at diagnosis, high monocyte count and high levels of S100A9 and S100A12 were significantly associated with short progression free survival (PFS) after androgen deprivation therapy (ADT). High monocyte count and S100A9 levels were also associated with short cancer-specific survival, with monocyte count providing independent prognostic information. These findings indicate that circulating levels of monocytes, as well as S100A9 and S100A12, could be biomarkers for metastatic prostate cancer associated with particularly poor prognosis.

Immune profiling of the bone marrow microenvironment in patients with high-risk localized prostate cancer

Bone marrow (BM) is a primary metastatic site in prostate cancer (PC) and bone invasion is considered incurable. T cell-mediated immune surveillance is essential in controlling both tumorigenesis and initiation of metastases. Beside tropism, dissemination of PC cells to the BM may be facilitated by defects in BM immune homeostasis predisposing this niche to colonization.

To evaluate the BM immune microenvironment in locally advanced, non-metastatic PC, we performed flow cytometry analysis of myeloid and lymphoid subsets in BM aspirates and peripheral blood collected during prostatectomy. Healthy BM aspirates served to establish a reference range for comparison.

We found alterations in BM immune composition of PC patients, including an increased CD4/CD8 ratio, enrichment of CD4⁺ T cells, increased CD56⁺CD3⁺ NKT and CD56⁺CD3^- NK yields compared to healthy controls. The lymphoid phenotype remained comparable regarding T cell activation and chemokine receptor-based polarization patterns. Additionally, we found increased B7H3 expression in the myeloid monocyte/macrophage subset and decreased DC infiltration in BM of PC patients.

These findings suggest that alterations in the immune milieu may limit immune surveillance that compromise the ability of the BM microenvironment to prevent tumor dissemination, and predispose development of bone metastases in a subset of patients with localized PC.

Tumor-Associated Macrophages in Human Breast, Colorectal, Lung, Ovarian and Prostate Cancers

Tumor-associated macrophages (TAMs) are major innate immune cells that constitute up to 50% of the cell mass of human tumors. TAMs are highly heterogeneous cells that originate from resident tissue-specific macrophages and from newly recruited monocytes. TAMs' variability strongly depends on cancer type, stage, and intratumor heterogeneity. Majority of TAMs are programmed by tumor microenvironment to support primary tumor growth and metastatic spread. However, TAMs can also restrict tumor growth and metastasis. In this review, we summarized the knowledge about the role of TAMs in tumor growth, metastasis and in the response to cancer therapy in patients with five aggressive types of cancer: breast, colorectal, lung, ovarian, and prostate cancers that are frequently metastasize into distant organs resulting in high mortality of the patients. Two major TAM parameters are applied for the evaluation of TAM correlation with the cancer progression: total amount of TAMs and specific phenotype of TAMs identified by functional biomarkers. We summarized the data generated in the wide range of international patient cohorts on the correlation of TAMs with clinical and pathological parameters of tumor progression including lymphatic and hematogenous metastasis, recurrence, survival, therapy efficiency. We described currently available biomarkers for TAMs that can be measured in patients' samples (tumor tissue and blood). CD68 is the major biomarker for the quantification of total TAM amounts, while transmembrane receptors (stabilin-1, CD163, CD206, CD204, MARCO) and secreted chitinase-like proteins (YKL-39, YKL-40) are used as biomarkers for the functional TAM polarization. We also considered that specific role of TAMs in tumor progression can depend on the localization in the intratumoral compartments. We have made the conclusion for the role of TAMs in primary tumor growth, metastasis, and therapy sensitivity for breast, colorectal, lung, ovarian, and prostate cancers. In contrast to other cancer types, majority of clinical studies indicate that TAMs in colorectal cancer have protective role for the patient and interfere with primary tumor growth and metastasis. The accumulated data are essential for using TAMs as biomarkers and therapeutic targets to develop cancer-specific immunotherapy and to design efficient combinations of traditional therapy and new immunomodulatory approaches.