Prostate Cancer Tumor Microenvironment Research Articles

Abstract 4987: TREM2 is a radiation-induced target for immunomodulation of tumor-associated macrophages in the prostate cancer tumor microenvironment

Abstract Background: The prostate cancer (PCa) tumor microenvironment (TME) is characterized by a predominance of myeloid cells that may have a key role in immunosuppression and disease progression. Stereotactic Body Radiation Therapy (SBRT) is utilized for treatment of localized and metastatic PCa and promotes inflammatory remodeling of the TME. We analyzed human PCa specimens at acute post-SBRT timepoints to identify radiation-induced targets in the PCa TME and used in vitro and in vivo models to test and validate our findings. Methods: We performed 10X single-cell RNA sequencing (scRNA-seq) on prostatectomy specimens from men with high-risk localized PCa; 12,988 cells from 4 patients that underwent pre-operative SBRT and 47,314 cells from 6 patients that underwent prostatectomy alone. THP-1 monocytes polarized into macrophage (Mɸ) states [M0, M1, M2 and tumor-associated macrophages (TAM), were used to characterize TREM2 expression and immune responses to radiation or conditioned media (CM) derived from irradiated PC3 cells. In vivo studies with C57BL/6 mice inoculated with MC38 flank tumors or PTEN-/- SPOPmut CHD1del mouse prostate organoid line were used to analyze intratumoral myeloid populations in response to SBRT (37.5Gy in 5 fractions). Results: scRNA-seq analysis (Cell Ranger 7.1.0 pipelines; Seurat v5 R package) revealed enrichment of a cluster of myeloid cells defined by a damage-associated Mɸ gene signature (TREM2, APOE, SPP1, LGALS3, CD9) in response to SBRT compared with non-irradiated specimens (35.6% vs 5.7%). TREM2 expression was significantly upregulated in THP-1 cells polarized in M2 (p<0.001) and TAM (p<0.001) conditions, compared to M1 conditions. Irradiation (20Gy x1) of THP-1 cells significantly increased TREM2 expression in M0 (p<0.01), M1 (p<0.001), and TAM (p<0.01) conditions. Proliferation of PC3 cells exposed to CM from irradiated TAMs was significantly increased (p<0.0001) compared to CM from non-irradiated TAM. Alternatively, CM derived from irradiated PC3 cells significantly increased (p<0.05) TREM2 expression in M0-polarized Mɸ. In vivo studies, in MC38 and organoid models, noted a significant reduction (p<0.0001) in tumor volume at day 7 post-SBRT. Multi-parametric flow cytometry demonstrated robust myeloid infiltration in response to SBRT dominated by CD11b+F4/80+ TAMs in irradiated tumors. Among irradiated tumors, TREM2 expression was markedly elevated in TAMs (organoid and MC38, p<0.0001). Conclusion: Preliminary data in human irradiated PCa and validation studies in preclinical models suggest TREM2 expression on myeloid cells is a radiation-induced target. Further studies are underway to understand the functional and immunological implications of SBRT-induced TREM2 expression on TAMs and whether this can be therapeutically targeted to enhance anti-tumor immunity in PCa. Citation Format: Janny A. Villa-Pulgarin, Un In Chan, Francesca Khani, Fabio Socciarelli, Jiansheng Wu, Ryan Carelli, Jeffrey Kraynak, Silvia C. Formenti, Luigi Marchionni, Massimo Loda, Himanshu Nagar, Ariel E. Marciscano, Christopher E. Barbieri. TREM2 is a radiation-induced target for immunomodulation of tumor-associated macrophages in the prostate cancer tumor 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 4987.

Abstract 1240: Enhancing NK cell function in the ‘cold’ tumor microenvironment of prostate cancer with a novel tri-specific killer engager

Abstract Introduction: Natural killer (NK) cells are associated with good prognosis in patients with metastatic castration-resistant prostate cancer (mCRPC). However, NK cell function is hindered in the immunosuppressive and hypoxic tumor microenvironment (TME) of mCRPC. To improve NK cell-mediated responses against mCRPC, we designed a novel Tri-specific Killer Engager (TriKE®) that engages with NK cell activating receptor CD16, binds to prostate-specific membrane antigen (PSMA) that is highly and specifically expressed on mCRPC, and has an interleukin (IL)-15 moiety that is essential for NK cell survival, proliferation, and priming. Methods: PSMA TriKE was produced using the mammalian expression system and tested using healthy donor and prostate cancer patient-derived NK cells. Flow cytometry-based functional and dye dilution proliferation assays were used to compare activation and proliferation of NK cells treated with PSMA TriKE or IL-15. NK cell cytolytic capacity against C4-2 cells, a PSMA-expressing prostate cancer line, was measured using IncuCyte live cell imaging. In various assays, hypoxic (1% oxygen) culture condition and cytokine-induced myeloid-derived suppressor cells (MDSC) were incorporated to better examine PSMA TriKE function in the physiological setting of mCRPC. In vivo testing of the PSMA TriKE was performed using C4-2 xenograft model and expanded NK cells in NSG mice. Results: PSMA TriKE significantly enhanced expansion of peripheral blood NK cells derived from healthy donors up to 8-fold. Additionally, PSMA TriKE induced significantly higher NK cell degranulation and intracellular IFNγ and TNFα buildup, when compared to IL-15 treatment, after incubation with C4-2 cells. Responses of NK cells derived from prostate cancer patients were equivalent to healthy controls. Although NK cell activation was not observed against PSMA knockout (KO) C4-2, indicating specificity of PSMA TriKE treatment, bystander killing of PSMA-KO C4-2 was achieved with PSMA TriKE treatment when wildtype C4-2 cells were cocultured. This suggests potential PSMA TriKE benefit in controlling tumor antigen escape, through natural cytotoxicity once primed. In settings that mimic the TME of mCRPC, NK cells treated with PSMA TriKE in prolonged exposure to hypoxia showed retention of cytotoxicity against C4-2 while IL-15 treated NK cells showed greatly impaired cytotoxicity. Similarly, MDSC suppressed NK cell cytotoxicity in the presence of IL-15, but PSMA TriKE treatment abrogated MDSC-induced suppression. Finally, PSMA TriKE enhanced tumor control and improved survival of mice as compared to IL-15 and no treatment groups in vivo. Conclusion: PSMA TriKE demonstrates potential in overcoming suppression of NK cells in the TME of mCRPC and is a promising candidate for advanced prostate cancer therapy. Citation Format: Shee Kwan Phung, Yvette Soignier, Nicholas Zorko, Rhett L. Waller, Josh Walker, Trygve Nelson, Carly Selleck, Laura Bendzick, Philippa Kennedy, Jeffrey S. Miller, Martin Felices. Enhancing NK cell function in the ‘cold’ tumor microenvironment of prostate cancer with a novel tri-specific killer engager [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 1240.

Abstract 5362: Targeting IRE1α alleviates the immunosuppressive tumor microenvironment in prostate cancer

Abstract Unfolded protein response (UPR) is a central stress response pathway in normal cells that is hijacked by tumor cells for their survival. However, how activation of UPR in cancer cells shapes the tumor microenvironment (TME) remain largely unexplored. Here, we investigated the role of IRE1α-XBP1s pathway on modulation of TME dynamics in prostate cancer (PCa). We found that IRE1α is increased in PCa patients and genetic or pharmacological inhibition of IRE1α signaling in the immunocompetent syngeneic mouse PCa model dramatically reduced tumor growth. Multiomics analysis of tumor samples upon IRE1α deletion in cancer cells showed significantly potentiated interferon (IFN) response and activation of immune system related pathways in the TME. Single-cell RNA sequencing (scRNA-seq) analysis revealed that the abundance of immunosuppressive cells, such as tumor-associated macrophages (TAMs) and T regulatory cells were markedly reduced in the IRE1α deficient tumors. Analysis of differentially expressed genes in the annotated cell types in the TME demonstrated that expression signatures associated with IFN responses were significantly enriched in TAMs, cancer cells, and dendritic cells. In addition, a novel scRNA-seq derived TAM gene signature is strongly associated with poor PCa survival. Furthermore, IRE1α inhibition by the small molecule MKC8866 (ORIN1001) that is in clinical trials significantly enhanced anti-PD-1 checkpoint inhibitor therapy in mice. Our findings indicate that IRE1α not only promotes cancer cell growth and survival, but it also strongly inhibits anti-tumor immunity in the PCa TME. Citation Format: Bilal Unal, Omer Faruk Kuzu, Yang Jin, Daniel Camilo Hurtado, Marieke Lydia Kuijjer, Mads Daugaard, Htoo Zarni Oo, John B. Patterson, Fahri Saatcioglu. Targeting IRE1α alleviates the immunosuppressive tumor microenvironment 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 5362.

Abstract 7351: Delineating the prostate cancer tumor microenvironment through scRNA-seq profiling at different timepoints

Abstract Distant metastasis remains the leading cause of death in patients with prostate cancer (PCa), however, the underlying mechanisms of this process remain unclear. Using samples from genetically-engineered mouse models (GEMMs) of PCa, we have identified eight different stromal cell states linked to epithelial mutations that may impact PCa progression to metastatic stages. To further investigate the unique intercellular interactions in the tumor microenvironment (TME) involved in mediating disease progression, we use single cell RNA sequencing (scRNA-seq) to profile primary PCa samples from different GEMMs including TRAMP, Hi-MYC, and FVBN, at different timepoints. Analysis of the scRNA-seq data revealed a significant enrichment of three clusters, designated as stromal c6 (s6), epithelial c7 (e7), and epithelial c10 (e10), exclusively in TRAMP, each expressing proliferative markers such as Mki67 and Top2a. To investigate the intercellular interactions among these clusters, we conducted ligand-receptor (LR) interaction analysis using CellChat. Notably, s6 is expressing the genes encoding ligands Bmp4, Fn1, and Igf1, which interact with the receptors Bmpr1b/Bmpr2, Itga3/Itgb1, and Igf1r, respectively expressed in e7. Subsequently, the transcriptomic profiles of these cells were used to build and validate a robust gene signature that can predict metastasis and survival in patients with PCa using a large cohort of 1239 samples, 930 of which were used for training while the remaining 309 samples were used for testing the model’s performance. In conclusion, these results underscore the role of the TME mediating PCa progression and highlight the potential of leveraging the TME to extract predictive and prognostic features which can be later employed to build predictive and prognostic models for patients with PCa. Citation Format: Itzel Valencia, Hubert Pakula, Mohamed Omar, Massimo Loda, Luigi Marchionni. Delineating the prostate cancer tumor microenvironment through scRNA-seq profiling at different timepoints [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 7351.

TUMOR MICROENVIRONMENT-ASSOCIATED miR-7-5p, miR-19a-3p, AND miR-23b-3p EXPRESSION IN PROSTATE CANCER WITH DIFFERENT PROGRESSION RISK.

The tumor microenvironment (TME) plays an important role in the occurrence and progression of prostate cancer (PCa). At the same time, the mechanisms and features of the interaction between tumor cells and individual components of the TME in PCa remain not fully elucidated. The aim was to study the expression levels of tumor-associated miR-7-5p, miR-19a-3p, and miR-23b-3p in the PCa tissue and to analyze their relationship with the features of TME. The work is based on the analysis of the results of the examination and treatment of 50 patients with PCa of stages II-IV. The expression of miRNA in the PCa tissue was analyzed by the real-time polymerase chain reaction. The expression of alpha-smooth muscle actin (α-SMA), vimentin (VIM), and CD68 in PCa tissue was determined by the immunohistochemical method. The identification of mast cells in the PCa tissue was assessed by the histochemical method. The analysis of the expression levels of tumor-associated miRNAs demonstrated that the tumor tissue of patients with a high risk of PCa progression was characterized by 4.93 (p < 0.01) and 8.97 (p < 0.05) times higher levels of miR-19a-3p and miR-23b-3p, respectively, compared to similar indicators in the group of patients with a low risk of PCa progression. The levels of miR-7-5p and miR-19a-3p expression in the PCa tissue correlated with the expression level of α-SMA (r = 0.49 and r = 0.45, respectively; p < 0.05) and VIM (r = 0.45 and r = 0.46; respectively, p < 0.05). A direct relationship (r = 0.44; p < 0.05) was established between the level of miR-7-5p expression and the degree of infiltration of the prostate gland tissue by tumor-associated macrophages. The features of the expression of tumor-associated miR-7-5p, miR-19a-3p, and miR-23b-3p indicated the prospect of their use as markers of the aggressiveness of the PCa course.

Autophagy-related long non-coding RNAs act as prognostic biomarkers and associate with tumor microenvironment in prostate cancer

Autophagy-related long non-coding RNAs act as prognostic biomarkers and associate with tumor microenvironment in prostate cancer

Targeting MerTK decreases efferocytosis and increases anti-tumor immune infiltrate in prostate cancer

The prostate cancer tumor microenvironment (TME) is comprised of many cell types that can contribute to and influence tumor progression. Some of the most abundant prostate cancer TME cells are macrophages, which can be modeled on a continuous spectrum of M1-like (anti-tumor macrophages) to M2-like (pro-tumor macrophages). A function of M2-like macrophages is efferocytosis, the phagocytosis of apoptotic cells. Based on literature from other models and contexts, efferocytosis further supports the M2-like macrophage phenotype. MerTK is a receptor tyrosine kinase that mediates efferocytosis by binding phosphatidylserine on apoptotic cells. We hypothesize efferocytosis in the prostate cancer TME is a tumor-promoting function of macrophages and that targeting MerTK-mediated efferocytosis will slow prostate cancer growth and promote an anti-tumor immune infiltrate. The aims of this study are to measure efferocytosis of prostate cancer cells by in vitro human M1/M2 macrophage models and assess changes in the M2-like, pro-tumor macrophage phenotype following prostate cancer efferocytosis. Additionally, this study aims to demonstrate that targeting MerTK decreases prostate cancer efferocytosis and promotes an anti-tumor immune infiltrate. We have developed methodology using flow cytometry to quantify efferocytosis of human prostate cancer cells using the LNCaP cell line. We observed that M2 macrophages efferocytose the LNCaP cell line more than M1 macrophages. Following efferocytosis of LNCaP cells by M2 human monocyte-derived macrophages (HMDMs), we observed an increase in the M2-like, pro-tumor phenotype by flow cytometry cell surface marker analysis. By qRT-PCR, flow cytometry, and Western blot, we detected greater MerTK expression in M2 than M1 macrophages. Targeting MerTK with antibody Mer590 decreased LNCaP efferocytosis by M2 HMDMs, establishing the role of MerTK in prostate cancer efferocytosis. In the prostate cancer mouse model hi-myc, Mertk KO increased anti-tumor immune infiltrate including CD8 T cells. These findings support targeting MerTK-mediated efferocytosis as a novel therapy for prostate cancer.

Fibroblast-derived exosomal microRNA regulates NKX3-1 expression in androgen-sensitive, androgen receptor-dependent prostate cancer cells.

Androgen deprivation therapy (ADT) targeting androgen production and androgen receptor (AR) signaling is the primary antihormonal therapy in the treatment of advanced prostate cancer (PCa). However, no clinically established molecular biomarkers have been identified to predict the effectiveness of ADT before starting ADT. The tumor microenvironment of PCa contains fibroblasts that regulate PCa progression by producing multiple soluble factors. We have previously reported that AR-activating factor-secreted fibroblasts increase the responsiveness of androgen-sensitive, AR-dependent PCa cells to ADT. Thus, we hypothesized that fibroblast-derived soluble factors may affect cancer cell differentiation by regulating cancer-related gene expression in PCa cells and that the biochemical characteristics of fibroblasts may be used to predict the effectiveness of ADT. Here, we investigated the effects of normal fibroblasts (PrSC cells) and three PCa patient-derived fibroblast lines (pcPrF-M5, -M28, and -M31 cells) on the expression of cancer-related genes in androgen-sensitive, AR-dependent human PCa cells (LNCaP cells) and three sublines showing different androgen sensitivities and AR dependencies. The mRNA expression of the tumor suppressor gene NKX3-1 in LNCaP cells and E9 cells (which show low androgen sensitivity and AR dependency) was significantly increased by treatment with conditioned media from PrSC and pcPrF-M5 cells but not from pcPrF-M28 and pcPrF-M31 cells. Notably, no upregulation of NKX3-1 was observed in F10 cells (AR-V7-expressing, AR-independent cells with low androgen sensitivity) and AIDL cells (androgen-insensitive, AR-independent cells). Among 81 common fibroblast-derived exosomal microRNAs that showed 0.5-fold lower expression in pcPrF-M28 and pcPrF-M31 cells than in PrSC and pcPrF-M5 cells, miR-449c-3p and miR-3121-3p were found to target NKX3-1. In only LNCaP cells, the NKX3-1 mRNA expression was significantly increased by transfection of an miR-3121-3p mimic but not that of the miR-449c-3p mimic. Thus, fibroblast-derived exosomal miR-3121-3p may be involved in preventing the oncogenic dedifferentiation of PCa cells by targeting NKX3-1 in androgen-sensitive, AR-dependent PCa cells.

Abstract B027: Elevated mitochondrial reactive oxygen species dysregulate the tumor microenvironment in prostate cancer of African American men

Abstract African American men (AAM) are more than twice as likely to die of prostate cancer (PCa) compared to European American men (EAM). While socioeconomics, access to optimal care and life-style factors contribute towards these disparities, underlying biologic differences in AAM remain important drivers of PCa disparities. In the current work, we aimed to explore the interplay between oxidative stress and inflammatory signaling in promoting progression of PCa in AAM. Oxidative stress results from excessive reactive oxygen species (ROS) generated mainly via membrane bound oxidases, the mitochondrial electron transport chain (ETC) or peroxisomes. We performed a robust comparative genomics to determine whether there is a race dependent expression of genes related to ROS in publicly available PCa datasets. We then prospectively examined the differential gene expression of these genesets in PCa from clinically matched AAM and EAM in VANDAAM, a validation study of Decipher genomic testing in 243 men with localized PCa. We then combined computational and experimental approaches to explore the molecular mechanisms and consequences of exacerbated oxidative stress. We found that ETC complex I, III related genes are the most differentially expressed in AAM compared with EAM. To examine whether AAM vs EAM cell lines exhibits differential sensitivity to ETC modulation, we blocked key ETC enzymes using complex I inhibitor, rotenone, and complex III inhibitor, antimycin A. We used 2 types of mitochondria-specific labels that distinguish respiring and ROS-generating mitochondria. While the relative levels of respiring mitochondria remain constant, we found that antimycin A induced higher level of mitochondrial ROS in AAM PCa cell lines compared with EAM PCa cell lines. To understand the interplay between mitochondrial ETC complex I &amp; III and immune microenvironment, we computed the correlational discordance of ETC complex I &amp; III expression scores and expression of &amp;gt;1200 immune-related genes between AAM vs EAM in the VANDAAM cohort. These analyses suggest that ETC complex I &amp; III correlate with several immunosuppressive genes including the macrophage markers CD68 and CD163 and T cell exhaustion markers. In addition, intersecting discordant genes from several datasets suggests enrichment of inflammatory cytokines and type I interferon signature which we then validated using ex vivo culture of PCa tissues. In summary, we discovered a role of mitochondrial electron transport chain in regulating inflammatory circuits in PCa of AAM. Unraveling roles of mitochondria in promoting immune suppression will have significant impact on understanding the intersection between social pressures and biological stress responses in minority populations. Citation Format: Asmaa El-Kenawi, Ryan Putney, Shivanshu Awasthi, Amparo Serna, Corrado Caslini, Jasreman Dhillon, Kosj Yamoah. Elevated mitochondrial reactive oxygen species dysregulate the tumor microenvironment in prostate cancer of African American men [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr B027.

Abstract IA019: Tumor microenvironment modulation is critical for cellular immunotherapy efficacy

Abstract Background: Chimeric antigen receptor (CAR)-engineered T cell therapies are being pursued for the treatment of prostate cancer, among other solid tumors. However the role of lymphodepletion was uncertain for application outside of heme malignancies. We studied the effect of chemotherapy preconditioning on the tumor immune microenvironment along with the impact on CAR-T cell activity. Methods: Immunocompetent mice bearing RM9 prostate tumors lentivirally transduced to express human prostate stem cell antigen (PSCA) and treated with PSCA targeted CAR T cells alone, or after 100 mg/kg cyclophosphamide (Cy). Tumors were evaluated for immune cell subsets infiltration in addition to clinical response. As part of a phase 1 dose escalation trial patients received 100 M PSCA-targeted CAR T cells, manufactured at City of Hope’s cGMP facility, alone or after Cy. CAR T persistence and cytokine levels were evaluated by flow cytometry and luminex, respectively. Results: CAR T cells alone had minimal anti-tumor effect in immune competent mice. Cy was associated with increased CD11c+ DCs and reduced CD206+ M2 macrophages in the tumors. With Cy pre-conditioning followed by infusion of PSCA-CAR T cells, over 40% of mice had complete response (CR) and rejected rechallenge of tumor. 10-fold greater T cell infiltration was noted in tumors after Cy preconditioning, with lesser increase and no anti-tumor effect noted with Cy + mock CAR T cells. In the phase 1 human trial greater CAR T cell expansion and cytokine induction were noted with Cy + PSCA-CAR T compared to PSCA-CAR T alone. Conclusion: Cy functions as a modifier of the prostate cancer tumor microenvironment, facilitating CAR T cell infiltration and expansion. This has resulted in greater activity of PSCA-CAR T cells both in murine models and preliminary human testing. Further study of manipulations to optimize the tumor immune microenvironment will likely be important to maximizing efficacy of cellular immunotherapy in prostate cancer. Citation Format: Tanya B Dorff, M Suzette Blanchard, John Murad, Lauren Adkins, Gaurav Dhaploa, Stephen Forman, Saul Priceman. Tumor microenvironment modulation is critical for cellular immunotherapy efficacy [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr IA019.

CHRM4/AKT/MYCN upregulates interferon alpha-17 in the tumor microenvironment to promote neuroendocrine differentiation of prostate cancer

Current treatment options for prostate cancer focus on targeting androgen receptor (AR) signaling. Inhibiting effects of AR may activate neuroendocrine differentiation and lineage plasticity pathways, thereby promoting the development of neuroendocrine prostate cancer (NEPC). Understanding the regulatory mechanisms of AR has important clinical implications for this most aggressive type of prostate cancer. Here, we demonstrated the tumor-suppressive role of the AR and found that activated AR could directly bind to the regulatory sequence of muscarinic acetylcholine receptor 4 (CHRM4) and downregulate its expression. CHRM4 was highly expressed in prostate cancer cells after androgen-deprivation therapy (ADT). CHRM4 overexpression may drive neuroendocrine differentiation of prostate cancer cells and is associated with immunosuppressive cytokine responses in the tumor microenvironment (TME) of prostate cancer. Mechanistically, CHRM4-driven AKT/MYCN signaling upregulated the interferon alpha 17 (IFNA17) cytokine in the prostate cancer TME after ADT. IFNA17 mediates a feedback mechanism in the TME by activating the CHRM4/AKT/MYCN signaling-driven immune checkpoint pathway and neuroendocrine differentiation of prostate cancer cells. We explored the therapeutic efficacy of targeting CHRM4 as a potential treatment for NEPC and evaluated IFNA17 secretion in the TME as a possible predictive prognostic biomarker for NEPC.

Prostrate malignant tumor and benign prostatic hyperplasia microenvironments in black African men: Limited infiltration of CD8+ T lymphocytes, NK-cells, and high frequency of CD73+ stromal cells.

Anti-cancerous immunology has yet to be investigated in the African black population, despite being the dawn of precision medicine. Here we investigated the tumor microenvironment of prostate cancer and benign prostatic hyperplasia (BPH) in black Africans. Through immunohistochemistry analysis of prostate cancer and BPH patients' biopsies, we investigated the expression and distribution of CD73, CCD8 T-lymphocytes, and natural killer cells. In addition, we looked at tumor-infiltrating features CD8 T-lymphocytes and natural killer cells. We show for the first time in black Africans a high expression of CD73 in epithelial-stromal cells and virtually no infiltration of CD8 T lymphocytes and natural killer cells in the tumoral area. In addition, CD73 was seven (7) times more likely to be expressed in prostate cancer stromal tissues than in benign prostatic hyperplasia tissues (odds ratio = 7.2; χ2 = 21; p < .0001). In addition, PSA concentration was significantly higher in prostate cancer patients than in BPH patients (p < .001). Also, the PSA-based ROC. analysis showed an area under the curve of 0.87 (p < .0001). CD73 expression is more likely expressed in prostate cancer stromal tissues than in benign prostatic hyperplasia tissues. The features of prostate cancer in Black Africans suggest CD73 expression as a possible target for immunotherapy in this population.

Single-cell RNA sequencing uncovers heterogeneous transcriptional signatures in tumor-infiltrated dendritic cells in prostate cancer

Prostate cancer (PCa) is one of the two solid malignancies in which a higher T cell infiltration in the tumor microenvironment (TME) corresponds with a worse prognosis for the tumor. The inability of T cells to eliminate tumor cells despite an increase in their number reinforces the possibility of impaired antigen presentation. In this study, we investigated the TME at single-cell resolution to understand the molecular function and communication of dendritic cells (DCs) (as professional antigen-presenting cells). According to our data, tumor cells stimulate the migration of immature DCs to the tumor site by inducing inflammatory chemokines. Many signaling pathways such as TNF-α/NF-κB, IL2/STAT5, and E2F up-regulated after DCs enter the tumor location. In addition, some molecules such as GPR34 and SLCO2B1 decreased on the surface of DCs. The analysis of molecular and signaling alterations in DCs revealed some suppression mechanisms of tumors, such as removing mature DCs, reducing the DC's survival, inducing anergy or exhaustion in the effector T cells, and enhancing the differentiation of T cells to Th2 and Tregs. In addition, we investigated the cellular and molecular communication between DCs and macrophages in the tumor site and found three molecular pairs including CCR5/CCL5, CD52/SIGLEC10, and HLA-DPB1/TNFSF13B. These molecular pairs are involved in the migration of immature DCs to the TME and disrupt the antigen-presenting function of DCs. Furthermore, we presented new therapeutic targets by the construction of a gene co-expression network. These data increase our knowledge of the heterogeneity and the role of DCs in PCa TME.

Targeting advanced prostate cancer with STEAP1 chimeric antigen receptor T cell and tumor-localized IL-12 immunotherapy

Six transmembrane epithelial antigen of the prostate 1 (STEAP1) is a cell surface antigen for therapeutic targeting in prostate cancer. Here, we report broad expression of STEAP1 relative to prostate-specific membrane antigen (PSMA) in lethal metastatic prostate cancers and the development of a STEAP1-directed chimeric antigen receptor (CAR) T cell therapy. STEAP1 CAR T cells demonstrate reactivity in low antigen density, antitumor activity across metastatic prostate cancer models, and safety in a human STEAP1 knock-in mouse model. STEAP1 antigen escape is a recurrent mechanism of treatment resistance and is associated with diminished tumor antigen processing and presentation. The application of tumor-localized interleukin-12 (IL-12) therapy in the form of a collagen binding domain (CBD)-IL-12 fusion protein combined with STEAP1 CAR T cell therapy enhances antitumor efficacy by remodeling the immunologically cold tumor microenvironment of prostate cancer and combating STEAP1 antigen escape through the engagement of host immunity and epitope spreading.

Abstract 1956: Stress-mediated reactive oxygen species from mitochondria dysregulates the tumor microenvironment in prostate cancer of African American men

Abstract Prostate cancer (PCa) is the second leading cause of cancer-related death in men in United States. African American men (AAM) have higher rates of PCa incidence and mortality compared with European American men (EAM). While socioeconomics, access to optimal care and life-style factors contribute towards these disparities, underlying biologic differences in AAM remain important drivers of PCa disparities. In the current work, we aimed to explore the interplay between oxidative stress and inflammatory signaling in promoting progression of PCa in AAM. Oxidative stress results from excessive reactive oxygen species (ROS) generated mainly via membrane bound oxidases, peroxisomes or the mitochondrial electron transport chain (ETC). We performed a robust comparative genomics to determine whether there is a race dependent expression of genes related to ROS in publicly available PCa datasets. We then prospectively examined the differential gene expression of these genesets in PCa from clinically matched AAM and EAM in the VANDAAM prospective study. VANDAAM is a validation study of DecipherTM genomic testing in 243 men with localized PCa. We then combined computational and experimental approaches to explore the molecular mechanisms and consequences of exacerbated oxidative stress. We found that ETC complex I, III related genes are the most differentially expressed in AAM compared with EAM. To examine whether AAM vs EAM cell lines exhibits differential sensitivity to ETC modulation, we blocked key ETC enzymes using complex I inhibitor, rotenone, and complex III inhibitor, antimycin A. We used 2 types of mitochondria-specific labels that distinguish respiring and ROS-generating mitochondria. While the relative levels of respiring mitochondria remain constant, we found that antimycin A induced higher level of mitochondrial ROS in AAM PCa cell lines compared with EAM PCa cell lines. To understand the interplay between mitochondrial ETC complex I &amp; III and immune microenvironment, we computed the correlational discordance of ETC complex I &amp; III expression scores and expression of &amp;gt;1200 immune-related genes between AAM vs EAM in VANDAAM cohort. These analyses suggest that ETC complex I &amp; III correlate with several immunosuppressive genes including the macrophage markers CD68 and CD163 and T cell exhaustion markers. In addition, intersecting discordant genes from several datasets suggests enrichment of inflammatory cytokines and type I interferon signature which we then validated using ex vivo culture of PCa tissues. In summary, we discovered a role of mitochondrial electron transport chain in regulating inflammatory circuits in PCa of AAM. Unraveling roles of mitochondria in promoting immune suppression will have significant impact on understanding the intersection between social pressures and biological stress responses. Citation Format: Asmaa El-Kenawi, Ryan Putney, Shivanshu Awasthi, Amparo Serna, Corrado Caslini, Jasreman Dhillon, Kosj Yamoah. Stress-mediated reactive oxygen species from mitochondria dysregulates the tumor microenvironment in prostate cancer of African American men [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1956.

Stk10 Deficiency in Mice Promotes Tumor Growth by Dysregulating the Tumor Microenvironment

Serine-threonine kinase 10 (STK10) is a member of the STE20/p21-activated kinase (PAK) family and is predominantly expressed in immune organs. Our previous reports suggested that STK10 participates in the growth and metastasis of prostate cancer via in vitro and in vivo data. However, the correlation between STK10 and the tumor microenvironment (TME) remains unclear. In this study, we assessed the relationship between STK10 and the immune cells in the tumor microenvironment of prostate cancer through bioinformatic analysis, and investigated the role of Stk10 in tumor growth using an Stk10 knockout mouse model. The results showed that STK10 is significantly associated with the tumor-infiltrating immune cells including lymphocytes, neutrophils, macrophages and dendritic cells. The target deletion of host Stk10 results in increased tumor growth, due to decreased activated/effector cytotoxic T lymphocytes (CTLs) and increased vessel density in the TME. In conclusion, we demonstrate that host Stk10 is involved in the host anti-tumor response by modulating the activated tumor-infiltrated CTLs and angiogenesis.

FLG Gene Mutation Up-regulates the Abnormal Tumor Immune Response and Promotes the Progression of Prostate Cancer.

Prostate Cancer (PCa) ranks sixth with regard to the cause of cancerinduced male diseases worldwide, and inflammation is closely associated with its morbidity, deterioration, and prognosis. Tumor Mutation Burden (TMB) is identified to be the most common biomarker for the prediction of immunotherapy. But it is still unclear about the relationship of gene mutations in PCa with TMB and immune response. To study the relationship between gene mutation and anti-tumor immune response in the prostate cancer tumor microenvironment. In the present work, the PCa somatic mutation data were collected from the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA) datasets. As a result, 8 genes with high mutation frequency, including TP53, PTEN, TTN, FLG, CTNNB1, SPOP, MUC16, and KMT2C, were discovered to be covered by 4 cohorts from the United States, Canada, the United Kingdom, and China. Overall, the FLG mutation was related to a greater TMB, which predicted the dismal prognostic outcome. Besides, the CIBERSORT algorithm and Gene Set Enrichment Analysis (GSEA) were adopted for analysis, which revealed that FLG mutation remarkably promoted immune response in the context of PCa and accelerated cancer development. To sum up, FLG shows a high mutation frequency in PCa, and is related to the increase in TMB, up-regulation of abnormal immune responses in tumors, and promotion of tumor progression. Therefore, it may be used as a biomarker to predict the abnormal immune responses and provide a therapeutic target for immunotherapy in the treatment of PCa.

A novel signature based on pyroptosis-related genes for predicting prognosis and treatment response in prostate cancer patients.

Background: Pyroptosis is a form of programmed cell death accompanied by specific inflammatory and immune responses, and it is closely related to the occurrence and progression of various cancers. However, the roles of pyroptosis-related genes (PRGs) in the prognosis, treatment response, and tumor microenvironment (TME) of prostate cancer (PCa) remain to be investigated. Methods: The mRNA expression data and clinical information of PCa patients were obtained from the Cancer Genome Atlas database (TCGA) and the cBioPortal for Cancer Genomics website, and the 52 PRGs were obtained from the published papers. The univariate, multivariate, and LASSO Cox regression algorithms were used to obtain prognostic hub PRGs. Meanwhile, qRT-PCR was used to validate the expression of hub genes between PCa lines and normal prostate epithelial cell lines. We then constructed and validated a risk model associated with the patient's disease-free survival (DFS). Finally, the relationships between risk score and clinicopathological characteristics, tumor immune microenvironment, and drug treatment response of PCa were systematically analyzed. Results: A prognostic risk model was constructed with 6 hub PRGs (CHMP4C, GSDMB, NOD2, PLCG1, CYCS, GPX4), and patients were divided into high and low-risk groups by median risk score. The risk score was confirmed to be an independent prognostic factor for PCa in both the training and external validation sets. Patients in the high-risk group had a worse prognosis than those in the low-risk group, and they had more increased somatic mutations, higher immune cell infiltration and higher expression of immune checkpoint-related genes. Moreover, they were more sensitive to cell cycle-related chemotherapeutic drugs and might be more responsive to immunotherapy. Conclusion: In our study, pyroptosis played a significant role in the management of the prognosis and tumor microenvironment of PCa. Meanwhile, the established model might help to develop more effective individual treatment strategies.

Spatial Profiling of the Prostate Cancer Tumor Microenvironment Reveals Multiple Differences in Gene Expression and Correlation with Recurrence Risk.

Simple SummaryIn prostate cancer (PCa), the tumor microenvironment plays a crucial role in both the development and progression of the disease. We used Digital Spatial Profiling multiplex technology to assess the expression of 58 protein and 1825 RNA transcripts in traditionally challenging samples (i.e., archived FFPE samples) while maintaining the spatial context of expression. First, we identified differences in protein and RNA expression among multiple cell types (stromal, epithelial, and immune cells). Second, we used a PCa tissue microarray of 1547 cores (97 patients) to further validate the protein expression of selected genes in a larger cohort of prostate cancer patients. We also computed survival models testing the relationship between OX40L, CTLA4, and CD11c protein expression in both tumor and tumor-adjacent stroma samples with time to biochemical relapse.The tumor microenvironment plays a crucial role in both the development and progression of prostate cancer. Furthermore, identifying protein and gene expression differences between different regions is valuable for treatment development. We applied Digital Spatial Profiling multiplex analysis to formalin-fixed paraffin embedded prostatectomy tissue blocks to investigate protein and transcriptome differences between tumor, tumor-adjacent stroma (TAS), CD45+ tumor, and CD45+ TAS tissue. Differential expression of an immunology/oncology protein panel (n = 58) was measured. OX40L and CTLA4 were expressed at higher levels while 22 other proteins, including CD11c, were expressed at lower levels (FDR < 0.2 and p-value < 0.05) in TAS as compared to tumor epithelia. A tissue microarray analysis of 97 patients with 1547 cores found positive correlations between high expression of CD11c and increased time to recurrence in tumor and TAS, and inverse relationships for CTLA4 and OX40L, where higher expression in tumor correlated with lower time to recurrence, but higher time to recurrence in TAS. Spatial transcriptomic analysis using a Cancer Transcriptome Atlas panel (n = 1825 genes) identified 162 genes downregulated and 69 upregulated in TAS versus tumor, 26 downregulated and 6 upregulated in CD45+ TAS versus CD45+ tumor. We utilized CIBERSORTx to estimate the relative immune cell fractions using CD45+ gene expression and found higher average fractions for memory B, naïve B, and T cells in TAS. In summary, the combination of protein expression differences, immune cell fractions, and correlations of protein expression with time to recurrence suggest that closely examining the tumor microenvironment provides valuable data that can improve prognostication and treatment techniques.

High expression of MYBL2 promotes progression and predicts a poor survival outcome of prostate cancer

To explore the correlation of MYB proto-oncogene like 2 (MYBL2) with biological behaviors and clinical prognosis of prostate cancer (PCa). We detected Mybl2 mRNA expression in 45 pairs of PCa and adjacent tissues using real-time quantitative PCR, and analyzed the correlation of high (23 cases) and low expression (22 cases) of Mybl2 with clinicopathological features and prognosis of the patients using nonparametric test, Kaplan-Meier survival analysis and univariate and multivariate Cox regression. The results were verified by analysis of the data from Cancer Genome Atlas (TCGA) microarray database, and the molecular pathways were identified by gene set enrichment analysis (GSEA). The CIBERPORT algorithm was used to identify the correlations between Mybl2 expression and tumor microenvironment of PCa. We also tested the effects of MYBL2 knockdown on proliferation and invasion of PCa cell lines using cell counting kit-8 and Transwell assays and observed the growth of PC3 cell xenograft with MYBL2 knockdown in nude mice and the expression levels of Ki-67 in the xenograft using immunohistochemistry. Mybl2 expression was significantly elevated in PCa tissues in close correlation with Gleason score and clinical and pathological stage of the tumor (P < 0.01) but not with the patients' age. Kaplan-Meier analysis indicated a significant negative correlation of high Mybl2 expression with recurrence-free survival (P < 0.05), but not with the overall survival of the patients. The data from TCGA suggested that clinical and pathological stages were independent prognostic factors for recurrence-free survival, and our data indicated that clinical stage and Gleason score were independent prognostic factors of PCa (P < 0.05). GSEA suggested that Mybl2 expression was related with the pathways involving immune function, cell adhesion, and cytokine secretion; CIBERPORT analysis suggested the involvement of Mybl2 expression with memory B cells and resting mast cells (P < 0.05). In LNCaP and PC-3 cells, MYBL2 knockdown significantly inhibited cell proliferation and invasion (P < 0.05); in the tumor-bearing nude mice, the xenografts derived from PC-3 cells with MYBL2 knockdown exhibited a lowered mean tumor weight and positivity rate for Ki67 (P < 0.05). Mybl2 is an oncogene related with multiple pathological indicators of PCa and can serve as a potential prognostic marker as well as a therapeutic target for patients with PCa.