FASN Gene Methylation is Associated with Fatty Acid Synthase Expression and Clinical-genomic Features of Prostate Cancer

Fatty acid synthase (FASN) catalyzes the synthesis of long-chain saturated fatty acids and is overexpressed during prostatic tumorigenesis, where it is the therapeutic target in several ongoing trials. However, the mechanism of FASN upregulation in prostate cancer remains unclear. Here, we examine FASN gene CpG methylation pattern by InfiniumEPIC profiling and whole-genome bisulfite sequencing across multiple racially diverse primary and metastatic prostate cancer cohorts, comparing with FASN protein expression as measured by digitally quantified IHC assay and reverse phase protein array analysis or FASN gene expression. We demonstrate that the FASN gene body is hypomethylated and overexpressed in primary prostate tumors compared with benign tissue, and FASN gene methylation is significantly inversely correlated with FASN protein or gene expression in both primary and metastatic prostate cancer. Primary prostate tumors with ERG gene rearrangement have increased FASN expression and we find evidence of FASN hypomethylation in this context. FASN expression is also significantly increased in prostate tumors from carriers of the germline HOXB13 G84E mutation compared with matched controls, consistent with a report that HOXB13 may contribute to epigenetic regulation of FASN in vitro. However, in contrast to previous studies, we find no significant association of FASN expression or methylation with self-identified race in models that include ERG status across two independent primary tumor cohorts. Taken together, these data support a potential epigenetic mechanism for FASN regulation in the prostate which may be relevant for selecting patients responsive to FASN inhibitors.

SIGNIFICANCE

Here, we leverage multiple independent primary and metastatic prostate cancer cohorts to demonstrate that FASN gene body methylation is highly inversely correlated with FASN gene and protein expression. This finding may shed light on epigenetic mechanisms of FASN regulation in prostate cancer and provides a potentially useful biomarker for selecting patients in future trials of FASN inhibitors.

Intratumoral Bacteria as Mediators of Cancer Immunotherapy Response

Multiple lines of evidence spanning from animal models to human clinical trials indicate that the microbiome influences cancer immunotherapy response. Whereas initial studies focused exclusively on the gastrointestinal (gut) microbiota-tumor axis, more recent studies have examined the possibility that bacteria located within tumor cells or within the tumor microenvironment mediate cancer treatment response. Strikingly, this phenomenon has been demonstrated in cancers that arise in anatomic locations that are traditionally thought to be devoid of resident microbiota. In this issue of Cancer Research, Wu and colleagues examine the effects of intratumoral bacterial signatures on treatment response in the setting of neoadjuvant chemotherapy combined with immunotherapy (NACI) in the treatment of esophageal squamous cell carcinoma (ESCC). The study reports that intratumoral Streptococcus, presumably due to bacterial translocation from the gut, predicts the treatment efficacy of NACI in murine models as well as individuals with ESCC. These new findings further highlight the possibility that the presence of intratumoral microbes as well as their associated metabolites influence both the tumor immune microenvironment and immunotherapy efficacy. These findings also raise the intriguing possibility of cross-reactivity between tumor and bacterial antigens. Given that the gut microbiome is potentially a modifiable factor via diet, prebiotics/probiotics, and fecal microbiota transplantation, among other strategies, further exploration into the mechanisms by which gut and/or intratumoral bacteria influence antitumor immunity is certainly warranted. See related article by Wu et al., p. 3131.

Club-like cells in proliferative inflammatory atrophy of the prostate

Club cells are a type of bronchiolar epithelial cell that serve a protective role in the lung and regenerate damaged lung epithelium. Single-cell RNA sequencing (scRNA-seq) of young adult human prostate and urethra identified cell populations in the prostatic urethra and collecting ducts similar in morphology and transcriptomic profile to lung club cells. We further identified club cell-like epithelial cells by scRNA-seq of prostate peripheral zone tissues. Here, we aimed to identify and spatially localize club cells in situ in the prostate, including in the peripheral zone. We performed chromogenic RNA in situ hybridization for five club cell markers (CP, LTF, MMP7, PIGR, SCGB1A1) in a series of (1) nondiseased organ donor prostate and (2) radical prostatectomy specimens from individuals with prostate cancer. We report that expression of club cell genes in the peripheral zone is associated with inflammation and limited to luminal epithelial cells classified as intermediate cells in proliferative inflammatory atrophy (PIA). Club-like cells were enriched in radical prostatectomy specimens compared to nondiseased prostates and associated with high-grade prostate cancer. We previously reported that luminal epithelial cells in PIA can rarely harbor oncogenic TMPRSS2:ERG (ERG+) gene fusions, and we now demonstrate that club cells are present in association with ERG+ PIA that is transitioning to early adenocarcinoma. Finally, prostate epithelial organoids derived from prostatectomy specimens demonstrate that club-like epithelial cells can be established in organoids and are sensitive to anti-androgen-directed treatment in vitro in terms of decreased androgen signaling gene expression signatures compared to basal or hillock cells. Overall, our study identifies a population of club-like cells in PIA and proposes that these cells play an analogous role to that of club cells in bronchiolar epithelium. Our results further suggest that inflammation drives lineage plasticity in the human prostate and that club cells in PIA may be prone to oncogenic transformation. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Association of self-identified race and genetic ancestry with the immunogenomic landscape of primary prostate cancer

The genomic and immune landscapes of prostate cancer differ by self-identified race. However, few studies have examined the genome-wide copy number landscape and immune content of matched cohorts with genetic ancestry data and clinical outcomes. Here, we assessed prostate cancer somatic copy number alterations (sCNA) and tumor immune content of a grade-matched, surgically treated cohort of 145 self-identified Black (BL) and 145 self-identified White (WH) patients with genetic ancestry estimation. A generalized linear model adjusted with age, preoperative prostate-specific antigen (PSA), and Gleason Grade Group and filtered for germline copy number variations (gCNV) identified 143 loci where copy number varied significantly by percent African ancestry, clustering on chromosomes 6p, 10q, 11p, 12p, and 17p. Multivariable Cox regression models adjusted for age, preoperative PSA levels, and Gleason Grade Group revealed that chromosome 8q gains (including MYC) were significantly associated with biochemical recurrence and metastasis, independent of genetic ancestry. Finally, Treg density in BL and WH patients was significantly correlated with percent genome altered, and these findings were validated in the TCGA cohort. Taken together, our findings identify specific sCNA linked to genetic ancestry and outcome in primary prostate cancer and demonstrate that Treg infiltration varies by global sCNA burden in primary disease.

Localization of macrophage subtypes and neutrophils in the prostate tumor microenvironment and their association with prostate cancer racial disparities

BACKGROUND

Black men are two to three times more likely to die from prostate cancer (PCa) than White men. This disparity is due in part to discrepancies in socioeconomic status and access to quality care. Studies also suggest that differences in the prevalence of innate immune cells and heightened function in the tumor microenvironment of Black men may promote PCa aggressiveness.

METHODS

We evaluated the spatial localization of and quantified CD66ce⁺ neutrophils by immunohistochemistry and CD68⁺ (pan), CD80⁺ (M1), and CD163⁺ (M2) macrophages by RNA in situ hybridization on formalin-fixed paraffin-embedded tissues from organ donor "normal" prostate (n = 9) and radical prostatectomy (n = 38) tissues from Black and White men. Neutrophils were quantified in PCa and matched benign tissues in tissue microarray (TMA) sets comprised of 560 White and 371 Black men. Likewise, macrophages were quantified in TMA sets comprised of tissues from 60 White and 120 Black men. The phosphatase and tensin homolog (PTEN) and ETS transcription factor ERG (ERG) expression status of each TMA PCa case was assessed via immunohistochemistry. Finally, neutrophils and macrophage subsets were assessed in a TMA set comprised of distant metastatic PCa tissues collected at autopsy (n = 6) sampled across multiple sites.

RESULTS

CD66ce⁺ neutrophils were minimal in normal prostates, but were increased in PCa compared to benign tissues, in low grade compared to higher grade PCa, in PCa tissues from White compared to Black men, and in PCa with PTEN loss or ERG positivity. CD163⁺ macrophages were the predominant macrophage subset in normal organ donor prostate tissues from both Black and White men and were significantly more abundant in organ donor compared to prostatectomy PCa tissues. CD68,⁺  CD80,⁺ and CD163⁺ macrophages were significantly increased in cancer compared to benign tissues and in cancers with ERG positivity. CD68⁺ and CD163⁺ macrophages were increased in higher grade cancers compared to low grade cancer and CD80 expression was significantly higher in benign prostatectomy tissues from Black compared to White men.

CONCLUSIONS

Innate immune cell infiltration is increased in the prostate tumor microenvironment of both Black and White men, however the composition of innate immune cell infiltration may vary between races.

Composition of gastrointestinal microbiota in association with treatment response in individuals with metastatic castrate resistant prostate cancer progressing on enzalutamide and initiating treatment with anti-PD-1 (pembrolizumab)

Recent studies in cancer patients and animal models demonstrate that intestinal microbiota influence the therapeutic efficacy of cancer treatments, including immune checkpoint inhibition. However, no studies to-date have investigated relationships between gastrointestinal microbiota composition and response to checkpoint inhibition in advanced metastatic castrate resistant prostate cancer (mCRPC). We performed 16S rRNA gene sequencing of fecal DNA from 23 individuals with mCRPC progressing on enzalutamide and just prior to treatment with anti-PD-1 (pembrolizumab) to determine whether certain features of the microbiome are associated with treatment response (defined as serum PSA decrease >50% at any time on treatment or radiographic response per RECIST V.1.1). Global bacterial composition was similar between responders and non-responders, as assessed by multiple alpha and beta diversity metrics. However, certain bacterial taxa identified by sequencing across multiple 16S rRNA hypervariable regions were consistently associated with response, including the archetypal oral bacterium Streptococcus salivarius. Quantitative PCR (qPCR) of DNA extracts from fecal samples confirmed increased Streptococcus salivarius fecal levels in responders, whereas qPCR of oral swish DNA extracts showed no relationship between oral Streptococcus salivarius levels and response status. Contrary to previous reports in other cancer types, Akkermansia muciniphila levels were reduced in responder samples as assessed by both 16S rRNA sequencing and qPCR. We further analyzed our data in the context of a previously published “integrated index” describing bacteria associated with response and non-response to checkpoint inhibition. We found that the index was not reflective of response status in our cohort. Lastly, we demonstrate little change in the microbiome over time, and with pembrolizumab treatment. Our results suggest that the association between fecal microbiota and treatment response to immunotherapy may be unique to cancer type and/or previous treatment history.

Abstract 2411: Di-ganglioside GD2 expression and role in promoting tumorigenicity in prostate cancer

Background & Significance: Prostate cancer (PCa) is the second leading cause of cancer deaths (~34,000 in 2021 (ACS)) in American men. Castration resistance and resistance  to the next-gen androgen receptor (AR) targeted drugs are major challenges. Castration resistance involves multiple mechanisms, including androgen-independent signaling by androgen receptor (AR)- or its variants, and lineage plasticity (LP) with AR-indifferent neuroendocrine (NE) differentiation. Identifying new vulnerabilities across these multitude mechanisms could provide new therapeutic avenues against castration-resistant PCa (CRPC). The cell-surface di-ganglioside GD2 is overexpressed in neural crest cell tumors such as neuroblastoma & melanoma and chimeric (Dinutuximab) or humanized (Naxitamab) anti-GD2 antibodies are now FDA-approved for high-risk neuroblastoma therapy. GD2 expression is reported in other cancers such as breast cancer and glioma and is linked to cancer stem cell behavior. While limited prior studies have detected GD2 expression in PCa cell lines or tumor tissues, nothing is known about the functional role of GD2 in PCa.

Objectives: We hypothesized that GD2 overexpression in PCa could play a pro-tumorigenic role and that linkage of GD2 overexpression with CRPC progression may reveal the potential of targeting GD2 for CRPC therapy.

Study Design & Results: Immunohistochemical analysis of PCa patient and patient-derived xenograft tissue microarrays (TMAs) revealed GD2 expression in a subset of tumor cells. Fluorescence-activated cell sorter analysis of PCa cell lines showed strong constitutive GD2 expression on murine CRPC cell line RM-1 (derived from mutant Ras and c-Myc overexpressing prostatic epithelial cells) and human PCa line 22Rv1 (overexpresses wild-type AR and ARv7 splice variant). GD2 expression was induced de novo upon induction of lineage plasticity in GD2-negative LNCaP C4-2 prostate adenocarcinoma cell line by shRNA knockdown (KD) of RB1 or TP53. High GD2 expression was also induced when C4-2B cells were made enzalutamide resistant (C4-2BER). Induction of GD2 expression correlated with increased expression of rate-limiting GD2 biosynthetic pathway enzyme GD3 synthase (GD3S). CRISPR-Cas9 mediated stable GD3S knockout (KO) in the RM1 cell line led to the loss of GD2 expression. The GD3S-KO RM1 cells exhibited reduced proliferation, migration, invasion, and tumor sphere forming ability compared to the control cells. Intratibial injections in castrated male C57BL/6 mice showed a significant reduction in tumor development by GD3S KO RM1 cells compared to control cells.

Conclusions: Our studies demonstrate that GD2 is expressed in a subset of prostate cancers. Cell line-based studies show that GD2 expression promotes pro-tumorigenic traits. Future studies will assess the biological roles of GD2 in PCa and the potential of targeting GD2+ CRPC with antibody-based approved therapeutic agents.

Citation Format: Aaqib M. Bhat, Bhopal C. Mohapatra, Insha Mushtaq, Sukanya Chakraborty, Samikshan Dutta, Sameer Mirza, Matthew D. Storck, Subodh M. Lele, Ming-Fong Lin, Bruce J. Trock, Karen S. Sfanos, Colm Morrissey, Eva Corey, Jonathan Melamed, Leah Cook, Kaustubh Datta, Jane Meza, Jawed Siddiqui, Surinder K. Batra, Vimla Band, Hamid Band. Di-ganglioside GD2 expression and role in promoting tumorigenicity in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2411.

P2 purinergic receptor dysregulation in urologic disease

P2 purinergic receptors are involved in the normal function of the kidney, bladder, and prostate via signaling that occurs in response to extracellular nucleotides. Dysregulation of these receptors is common in pathological states and often associated with disease initiation, progression, or aggressiveness. Indeed, P2 purinergic receptor expression is altered across multiple urologic disorders including chronic kidney disease, polycystic kidney disease, interstitial cystitis, urinary incontinence, overactive bladder syndrome, prostatitis, and benign prostatic hyperplasia. P2 purinergic receptors are likewise indirectly associated with these disorders via receptor-mediated inflammation and pain, a common characteristic across most urologic disorders. Furthermore, select P2 purinergic receptors are overexpressed in urologic cancer including renal cell carcinoma, urothelial carcinoma, and prostate adenocarcinoma, and pre-clinical studies depict P2 purinergic receptors as potential therapeutic targets. Herein, we highlight the compelling evidence for the exploration of P2 purinergic receptors as biomarkers and therapeutic targets in urologic cancers and other urologic disease. Likewise, there is currently optimism for P2 purinergic receptor-targeted therapeutics for the treatment of inflammation and pain associated with urologic diseases. Further exploration of the common pathways linking P2 purinergic receptor dysregulation to urologic disease might ultimately help in gaining new mechanistic insight into disease processes and therapeutic targeting.

Modeling Human Prostate Cancer Metastasis in Mice via Resection of Subcutaneous Allografts

The 5-year survival rate for patients diagnosed with distant metastatic prostate cancer in the United States is 30.6%. Therefore, there is a great need to develop in vivo model systems to study prostate cancer metastasis and to test potential therapeutics. Most murine prostate cancer metastatic models involve intracardiac or intraosseous implantation of cancer cells, which bypass the early stages of tumor cell migration and invasion. Herein we provide a detailed protocol for a novel method of resecting subcutaneous prostate cancer allografts in immunocompetent mice to produce spontaneous metastases and describe a pilot study using this method of tumor resection. Intact male FVB/NCrl mice (n = 9) were inoculated subcutaneously with Myc-CaP cells. Tumors were surgically resected, and mice were monitored for tumor recurrence. Animals were euthanized or died, and a full set of tissues was collected for histopathologic examination. Tumors took an average of 44 days (range 23–61) to reach 1.7 cm in any direction. All tumors were resectable, and resection of the tumors increased the study length by 70 days (range 30–121). One mouse was euthanized early of an unrelated cause, and of eight remaining mice, four developed tumor recurrence at the site of resection. One mouse developed bone metastases, one mouse developed metastases to the abdominal cavity, and two mice showed signs of local invasion. This study demonstrates that resection of subcutaneous Myc-CaP cell allografts in mice results in local tumor recurrence and the development of distant metastases, providing a new model system to study prostate cancer metastasis in vivo.

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.

Identification of novel biomarkers differentially expressed between African-American and Caucasian-American prostate cancer patients

Prostate cancer (PCa) incidence and mortality rate vary among racial and ethnic groups with the highest occurrence in African American (AA) men who have mortality rates twice that of Caucasians (CA). In this study, we focused on differential expression of proteins in AA prostate cancer compared to CA using Protein Pathway Array Analysis (PPAA), in order to identify protein biomarkers associated with PCa racial disparity. Fresh frozen prostate samples (n=90) obtained from radical prostatectomy specimens with PCa, including 25 AA tumor, 21 AA benign, 23 CA tumor, 21 CA benign samples were analyzed. A total of 286 proteins and phosphoproteins were assessed using PPAA. By PPAA analysis, 33 proteins were found to be significantly differentially expressed in tumor tissue (n=48, including both CA and AA) in comparison to benign tissue (n=42). We further compared protein expression levels between AA and CA tumor groups and found that 3 proteins were differentially expressed (P<0.05 and q<5%). Aurora was found to be significantly increased in AA tumors, while Cyclin D1 and HNF-3a proteins were downregulated in AA tumors. Predicted risk score was significantly different between AA and CA ethnic groups using logistic regression analysis. In conclusion, we identified Aurora, Cyclin D1 and HNF-3a proteins as being differentially expressed between AA and CA in PCa tissue. Our study suggests that these proteins might be involved in different pathways that lead to aggressive PCa behavior in AA patients, potentially serving as biomarkers for the PCa racial disparity.

Incorporation of Data From Multiple Hypervariable Regions when Analyzing Bacterial 16S rRNA Gene Sequencing Data

Short read 16 S rRNA amplicon sequencing is a common technique used in microbiome research. However, inaccuracies in estimated bacterial community composition can occur due to amplification bias of the targeted hypervariable region. A potential solution is to sequence and assess multiple hypervariable regions in tandem, yet there is currently no consensus as to the appropriate method for analyzing this data. Additionally, there are many sequence analysis resources for data produced from the Illumina platform, but fewer open-source options available for data from the Ion Torrent platform. Herein, we present an analysis pipeline using open-source analysis platforms that integrates data from multiple hypervariable regions and is compatible with data produced from the Ion Torrent platform. We used the ThermoFisher Ion 16 S Metagenomics Kit and a mock community of twenty bacterial strains to assess taxonomic classification of six amplicons from separate hypervariable regions (V2, V3, V4, V6-7, V8, V9) using our analysis pipeline. We report that different amplicons have different specificities for taxonomic classification, which also has implications for global level analyses such as alpha and beta diversity. Finally, we utilize a generalized linear modeling approach to statistically integrate the results from multiple hypervariable regions and apply this methodology to data from a representative clinical cohort. We conclude that examining sequencing results across multiple hypervariable regions provides more taxonomic information than sequencing across a single region. The data across multiple hypervariable regions can be combined using generalized linear models to enhance the statistical evaluation of overall differences in community structure and relatedness among sample groups.

Association of B7-H3 expression with racial ancestry, immune cell density, and androgen receptor activation in prostate cancer

Background

B7 homolog 3 (B7‐H3) is an immunomodulatory molecule that is highly expressed in prostate cancer (PCa) and belongs to the B7 superfamily, which includes PD‐L1. Immunotherapies (antibodies, antibody‐drug conjugates, and chimeric antigen receptor T cells) targeting B7‐H3 are currently in clinical trials; therefore, elucidating the molecular and immune microenvironment correlates of B7‐H3 expression may help to guide trial design and interpretation. The authors tested the interconnected hypotheses that B7‐H3 expression is associated with genetic racial ancestry, immune cell composition, and androgen receptor signaling in PCa.

Methods

An automated, clinical‐grade immunohistochemistry assay was developed by to digitally quantify B7‐H3 protein expression across 2 racially diverse cohorts of primary PCa (1 with previously reported transcriptomic data) and pretreatment and posttreatment PCa tissues from a trial of intensive neoadjuvant hormonal therapy.

Results

B7‐H3 protein expression was significantly lower in self‐identified Black patients and was inversely correlated with the percentage African ancestry. This association with race was independent of the significant association of B7‐H3 protein expression with ERG/ETS and PTEN status. B7‐H3 messenger RNA expression, but not B7‐H3 protein expression, was significantly correlated with regulatory (FOXP3‐positive) T‐cell density. Finally, androgen receptor activity scores were significantly correlated with B7‐H3 messenger RNA expression, and neoadjuvant intensive hormonal therapy was associated with a significant decrease in B7‐H3 protein expression.

Conclusions

The current data underscore the importance of studying racially and molecularly diverse PCa cohorts in the immunotherapy era. This study is among the first to use genetic ancestry markers to add to the emerging evidence that PCa in men of African ancestry may have a distinct biology associated with B7‐H3 expression.

Lay Summary

B7‐H3 is an immunomodulatory molecule that is highly expressed in prostate cancer and is under investigation in clinical trials.

The authors determined that B7‐H3 protein expression is inversely correlated with an individual's proportion of African ancestry.

The results demonstrate that B7‐H3 messenger RNA expression is correlated with the density of tumor T‐regulatory cells.

Finally, in the first paired analysis of B7‐H3 protein expression before and after neoadjuvant intensive hormone therapy, the authors determined that hormone therapy is associated with a decrease in B7‐H3 protein levels, suggesting that androgen signaling may positively regulate B7‐H3 expression.

These results may help to guide the design of future clinical trials and to develop biomarkers of response in such trials.

B7‐H3 protein expression was significantly lower in self‐identified Black patients and was inversely correlated with the percentage African ancestry. Androgen receptor activity scores were significantly correlated with B7‐H3 messenger RNA expression, and neoadjuvant intensive hormonal therapy was associated with a significant decrease in B7‐H3 protein expression, consistent with a presumed androgen receptor binding site upstream of the B7‐H3 promoter.

Health inequity drives disease biology to create disparities in prostate cancer outcomes

Prostate cancer exerts a greater toll on African American men than on White men of European descent (hereafter referred to as European American men): the disparity in incidence and mortality is greater than that of any other common cancer. The disproportionate impact of prostate cancer on Black men has been attributed to the genetics of African ancestry, to diet and lifestyle risk factors, and to unequal access to quality health care. In this Review, all of these influences are considered in the context of the evolving understanding that chronic or recurrent inflammatory processes drive prostatic carcinogenesis. Studies of inherited susceptibility highlight the contributions of genes involved in prostate cell and tissue repair (BRCA1/2, ATM) and regeneration (HOXB13 and MYC). Social determinants of health appear to accentuate these genetic influences by fueling prostate inflammation and associated cell and genome damage. Molecular characterization of the prostate cancers that arise in Black versus White men further implicates this inflammatory microenvironment in disease behavior. Yet, when Black and White men with similar grade and stage of prostate cancer are treated equally, they exhibit equivalent outcomes. The central role of prostate inflammation in prostate cancer development and progression augments the impact of the social determinants of health on disease pathogenesis. And, when coupled with poorer access to high-quality treatment, these inequities result in a disparate burden of prostate cancer on African American men.

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.

Abstract PO-100: Association of B7-H3 expression with racial ancestry, immune cell density and AR activation in prostate cancer

Background: B7-H3 (CD276, PD-L3) is an immunomodulatory molecule highly expressed in prostate cancer and belonging to the B7 superfamily that also includes PD-L1 (B7-H1). Immunotherapies (antibodies, antibody-drug conjugates, and CAR-T cells) targeting B7-H3 are currently in clinical trials; thus elucidating the clinical, molecular and tumor immune microenvironment correlates of B7-H3 expression may help to guide trial design and interpretation. Methods: We developed an automated, clinical-grade immunohistochemistry assay to digitally quantify B7-H3 protein expression across two racially diverse cohorts of primary prostate cancer (including one with previously reported transcriptomic data), a set of prostatic neuroendocrine small cell carcinoma, and pre- and post-treatment tumor tissues from a trial of intensive neoadjuvant hormonal therapy. Results: B7-H3 protein expression is significantly lower in self-identified Black patients and inversely correlates with percent African ancestry by ancestry-informative markers. This association with race is independent of the significant association of B7-H3 expression with ERG/ETS and PTEN status. CD276 mRNA level, but not B7-H3 protein expression, is significantly correlated with regulatory (FOXP3+) T-cell density. Finally, androgen receptor activity (AR-A) scores are significantly correlated with CD276 mRNA expression, and neoadjuvant intensive hormonal therapy is associated with a significant decrease in B7-H3 protein expression. Conclusion: These data underscore the importance of studying racially and molecularly diverse prostate cancer cohorts in the era of immunotherapy. Our study is among the first to use genetic ancestry markers to add to emerging evidence that prostate tumors from men of African ancestry may have a distinct immune milieu associated with B7-H3 expression.

Citation Format: Adrianna A. Mendes, Jiayun Lu, Harsimar B Kaur, Siqun Zheng, Jianfeng Xu, Edward M. Schaeffer, Karen S. Sfanos, Janielle Maynard, Ashley E. Ross, Steven P. Balk, Mary-Ellen Taplin, Emmanuel S. Antonarakis, Corinne E. Joshu, Eugene Shenderov, Tamara L. Lotan. Association of B7-H3 expression with racial ancestry, immune cell density and AR activation in prostate cancer [abstract]. In: Proceedings of the AACR Virtual Conference: 14th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2021 Oct 6-8. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr PO-100.

Examining the Effects of 4He Exposure on the Gut-Brain Axis

Beyond low-Earth orbit, space radiation poses significant risks to astronaut health. Previous studies have shown that the microbial composition of the gastrointestinal (GI) microbiome changes upon exposure to high-linear energy transfer radiation. Interestingly, radiation-induced shifts in GI microbiota composition are linked to various neuropsychological disorders. Herein, we aimed to study changes in GI microbiota and behaviors of rats exposed to whole-body radiation (0, 5 or 25 cGy 4He, 250 MeV/n) at approximately 6 months of age. Fecal samples were collected 24 h prior to 4He irradiation and 24 h and 7 days postirradiation for quantitative PCR analyses to assess fecal levels of spore-forming bacteria (SFB), Bifidobacterium, Lactobacillus and Akkermansia. Rats were also tested in the social odor recognition memory (SORM) test at day 7 after 4He exposure. A subset of rats was euthanized 90 min after completion of the SORM test, and GI tissue from small intestine to colon were prepared for examining overall histological changes and immunohistochemical staining for serotonin (5-HT). No notable pathological changes were observed in GI tissues. Akkermansia spp. and SFB were significantly decreased in the 25 cGy group at 24 h and 7 days postirradiation compared to pre-exposure, respectively. Bifidobacterium and Lactobacillus spp. showed no significant changes. 5-HT production was significantly higher in the proximal small intestine and the cecum in the 25 cGy group compared to the sham group. The 25 cGy group exhibited deficits in recognition in SORM testing at day 7 postirradiation. Taken together, these results suggest a connection between GI microbiome composition, serotonin production, and neurobehavioral performance, and that this connection may be disrupted upon exposure to 25 cGy of 4He ions.

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.

Pathology Residency Program Special Expertise Tracks Meet the Needs of an Evolving Field

Pathologists who enter the workforce must have a diverse skill set beyond that of clinical diagnostics alone. Anticipating this need, the Johns Hopkins Pathology Residency Program developed Special Expertise Tracks to enhance training in relevant subspecialty domains. Using a combination of discussions and surveys, we assessed: (1) our current resident curriculum; (2) perceived curricular strengths and needs; (3) resident career preferences and ultimate career paths; (4) perceived barriers to implementing an advanced elective curriculum; and (5) available departmental/institutional resources. Additionally, we utilized the Accreditation Council for Graduate Medical Education Pathology Milestones as a curricular guide. Six professional residency training Special Expertise Tracks were established: Education, Physician-Scientist Research, Informatics, Quality Improvement/Quality Assurance/Value-Based Care, Health Policy/Hospital Management and Global Health. After implementation in 2017, the Education track has had 4 residents complete the curriculum successfully; the Physician-Scientist Research track has had 2 residents and the Informatics and Global Health tracks have each had one resident successfully complete their respective curricula. Currently, 5 residents are pursuing the Education track, one is pursuing the Physician-Scientist Research track, one is pursuing the Informatics track, and 2 residents are pursuing the Global Health track. Five residents have completed long-term projects including developing several e-learning modules, an online free digital cytopathology atlas, peer-reviewed articles, book chapters, and books. The Johns Hopkins Pathology Resident Special Expertise Track program provides pathology residents an opportunity to gain meaningful experience and additional skills tailored to their individual career interests.

Castration-mediated IL-8 promotes myeloid infiltration and prostate cancer progression

Unlike several other tumor types, prostate cancer rarely responds to immune checkpoint blockade (ICB). To define tumor cell intrinsic factors that contribute to prostate cancer progression and resistance to ICB, we analyzed prostate cancer epithelial cells from castration-sensitive and -resistant samples using implanted tumors, cell lines, transgenic models and human tissue. We found that castration resulted in increased expression of interleukin-8 (IL-8) and its probable murine homolog Cxcl15 in prostate epithelial cells. We showed that these chemokines drove subsequent intratumoral infiltration of tumor-promoting polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs), which was largely abrogated when IL-8 signaling was blocked genetically or pharmacologically. Targeting IL-8 signaling in combination with ICB delayed the onset of castration resistance and increased the density of polyfunctional CD8 T cells in tumors. Our findings establish a novel mechanism by which castration mediates IL-8 secretion and subsequent PMN-MDSC infiltration, and highlight blockade of the IL-8/CXCR2 axis as a potential therapeutic intervention.

GSTP1 positive prostatic adenocarcinomas are more common in Black than White men in the United States

GSTP1 is a member of the Glutathione-S-transferase (GST) family silenced by CpG island DNA hypermethylation in 90-95% of prostate cancers. However, prostate cancers expressing GSTP1 have not been well characterized. We used immunohistochemistry against GSTP1 to examine 1673 primary prostatic adenocarcinomas on tissue microarrays (TMAs) with redundant sampling from the index tumor from prostatectomies. GSTP1 protein was positive in at least one TMA core in 7.7% of cases and in all TMA cores in 4.4% of cases. The percentage of adenocarcinomas from Black patients who had any GSTP1 positive TMA cores was 14.9%, which was 2.5 times higher than the percentage from White patients (5.9%; P < 0.001). Further, the percentages of tumors from Black patients who had all TMA spots positive for GSTP1 (9.5%) was 3-fold higher than the percentage from White patients (3.2%; P<0.001). In terms of association with other molecular alterations, GSTP1 positivity was enriched in ERG positive cancers among Black men. By in situ hybridization, GSTP1 mRNA expression was concordant with protein staining, supporting the lack of silencing of at least some GSTP1 alleles in GSTP1-positive tumor cells. This is the first report revealing that GSTP1-positive prostate cancers are substantially over-represented among prostate cancers from Black compared to White men. This observation should prompt additional studies to determine whether GSTP1 positive cases represent a distinct molecular subtype of prostate cancer and whether GSTP1 expression could provide a biological underpinning for the observed disparate outcomes for Black men.

Feasibility of integrating canine olfaction with chemical and microbial profiling of urine to detect lethal prostate cancer

Prostate cancer is the second leading cause of cancer death in men in the developed world. A more sensitive and specific detection strategy for lethal prostate cancer beyond serum prostate specific antigen (PSA) population screening is urgently needed. Diagnosis by canine olfaction, using dogs trained to detect cancer by smell, has been shown to be both specific and sensitive. While dogs themselves are impractical as scalable diagnostic sensors, machine olfaction for cancer detection is testable. However, studies bridging the divide between clinical diagnostic techniques, artificial intelligence, and molecular analysis remains difficult due to the significant divide between these disciplines. We tested the clinical feasibility of a cross-disciplinary, integrative approach to early prostate cancer biosensing in urine using trained canine olfaction, volatile organic compound (VOC) analysis by gas chromatography-mass spectroscopy (GC-MS) artificial neural network (ANN)-assisted examination, and microbial profiling in a double-blinded pilot study. Two dogs were trained to detect Gleason 9 prostate cancer in urine collected from biopsy-confirmed patients. Biopsy-negative controls were used to assess canine specificity as prostate cancer biodetectors. Urine samples were simultaneously analyzed for their VOC content in headspace via GC-MS and urinary microbiota content via 16S rDNA Illumina sequencing. In addition, the dogs' diagnoses were used to train an ANN to detect significant peaks in the GC-MS data. The canine olfaction system was 71% sensitive and between 70-76% specific at detecting Gleason 9 prostate cancer. We have also confirmed VOC differences by GC-MS and microbiota differences by 16S rDNA sequencing between cancer positive and biopsy-negative controls. Furthermore, the trained ANN identified regions of interest in the GC-MS data, informed by the canine diagnoses. Methodology and feasibility are established to inform larger-scale studies using canine olfaction, urinary VOCs, and urinary microbiota profiling to develop machine olfaction diagnostic tools. Scalable multi-disciplinary tools may then be compared to PSA screening for earlier, non-invasive, more specific and sensitive detection of clinically aggressive prostate cancers in urine samples.

Why Do Epidemiologic Studies Find an Inverse Association Between Intraprostatic Inflammation and Prostate Cancer: A Possible Role for Colliding Bias?

Inflammation is an emerging risk factor for prostate cancer based largely on evidence from animal models and histopathologic observations. However, findings from patho-epidemiologic studies of intraprostatic inflammation and prostate cancer have been less supportive, with inverse associations observed in many studies of intraprostatic inflammation and prostate cancer diagnosis. Here, we propose collider stratification bias as a potential methodologic explanation for these inverse findings and provide strategies for conducting future etiologic studies of intraprostatic inflammation and prostate cancer.

Differential mast cell phenotypes in benign versus cancer tissues and prostate cancer oncologic outcomes

We reported previously that high numbers of mast cells in benign (extra-tumoral) regions of the prostate are associated with worse outcomes after radical prostatectomy including biochemical recurrence and the development of metastases. Herein, with a cohort of 384 men, we performed mast cell subtyping and report that higher minimum number of the tryptase-only (MC_T ) subset of extra-tumoral mast cells is associated with increased risk of biochemical recurrence (comparing highest to lowest tertiles: HR 2.32, 95% CI 1.37-3.93; P-trend = 0.002), metastases (HR 3.62, 95% CI 1.75-7.47; P-trend 0.001), and death from prostate cancer (HR 2.87, 95% CI 1.19-6.95; P-trend = 0.02). Preliminary RNA sequencing and comparison of benign versus cancer tissue mast cells revealed differential expression of additional site-specific genes. We further demonstrate that the genes CXCR4 and TFE3 are more highly expressed in tumor-infiltrating mast cells as well as other tumor-infiltrating immune cells and in tumor cells, respectively, and represent an altered tumor microenvironment. KIT variants were also differentially expressed in benign versus cancer tissue mast cells, with KIT variant 1 (GNNK⁺ ) mast cells identified as more prevalent in extra-tumoral regions of the prostate. Finally, using an established mouse model, we found that mast cells do not infiltrate Hi-Myc tumors, providing a model to specifically examine the role of extra-tumoral mast cells in tumorigenesis. Hi-Myc mice crossed to mast cell knockout (Wsh) mice and aged to 1 year revealed a higher degree of pre-invasive lesions and invasive cancer in wild-type mice versus heterozygous and knockout mice. This suggests a dosage effect where higher numbers of extra-tumoral mast cells resulted in higher cancer invasion. Overall, our studies provide further evidence for a role of extra-tumoral mast cells in driving adverse prostate cancer outcomes. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Obesity is Associated with Shorter Telomere Length in Prostate Stromal Cells in Men with Aggressive Prostate Cancer

In our prior studies, obesity was associated with shorter telomeres in prostate cancer-associated stromal (CAS) cells, and shorter CAS telomeres were associated with an increased risk of prostate cancer death. To determine whether the association between obesity and shorter CAS telomeres is replicable, we conducted a pooled analysis of 790 men who were surgically treated for prostate cancer, whose tissue samples were arrayed on five tissue microarray (TMA) sets. Telomere signal was measured using a quantitative telomere-specific FISH assay and normalized to 4',6-diamidino-2-phenylindole for 351 CAS cells (mean) per man; men were assigned their median value. Weight and height at surgery, collected via questionnaire or medical record, were used to calculate body mass index (BMI; kg/m²) and categorize men as normal (<25), overweight (25 ≤ BMI < 30), or obese (≥30). Analyses were stratified by grade and stage. Men were divided into tertiles of TMA- (overall) or TMA- and disease aggressiveness- (stratified) specific distributions; short CAS telomere status was defined by the bottom two tertiles. We used generalized linear mixed models to estimate the association between obesity and short CAS telomeres, adjusting for age, race, TMA set, pathologic stage, and grade. Obesity was not associated with short CAS telomeres overall, or among men with nonaggressive disease. Among men with aggressive disease (Gleason≥4+3 and stage>T2), obese men had a 3-fold increased odds of short CAS telomeres (OR: 3.06; 95% confidence interval: 1.07-8.75; P _trend = 0.045) when compared with normal weight men. Telomere shortening in prostate stromal cells may be one mechanism through which lifestyle influences lethal prostate carcinogenesis. PREVENTION RELEVANCE: This study investigates a potential mechanism underlying the association between obesity and prostate cancer death. Among men with aggressive prostate cancer, obesity was associated with shorter telomeres prostate cancer associated stromal cells, and shorter CAS telomeres have been associated with an increased risk of prostate cancer death.

Abstract PO-226: Localization of macrophages and neutrophils in the prostate tumor microenvironment and their association with prostate cancer racial disparities

African American (AA) men are two to three times more likely to die from prostate cancer (PCa) than European American (EA) men. This disparity may be due in part to socioeconomic status and discrepancies in access to quality care. Studies also suggest that differences in innate immune effector cells and function in the tumor microenvironment of AA men may promote PCa aggressiveness. Increased tumor- associated macrophages are associated with poorer outcomes and a high neutrophil- to-lymphocyte ratio is significantly associated with poorer survival in men with PCa. However, the prevalence of innate immune cells, their spatial localization, and their relationship to PCa racial disparities is largely unknown. We evaluated CD66ce+ neutrophils and CD68+ (pan), CD80+ (M1), and CD163+ (M2) macrophages using RNA in situ hybridization or immunohistochemistry on formalin-fixed paraffin-embedded whole tissue sections from prostate donor tissues with no cancer (n=4) and radical prostatectomy tissues from AA and EA men with low grade (Gleason ≤ 3+4) and higher grade (Gleason ≥ 4+3) PCa (n=38). Tissue microarray (TMA) sets containing radical prostatectomy tissues (n=932) or distant metastatic tissues obtained at autopsy (n=6) were also evaluated. Immune marker expression in TMAs was quantified using TMAJ and FrIDA software. CD66ce+ neutrophils were primarily localized to blood vessels in organ donor prostate specimens as well as normal appearing, non-inflamed regions of radical prostatectomy specimens. Increased CD66ce+ neutrophils were present in inflamed regions of benign tissues from both races. In analysis of TMAs, there was significantly increased CD66ce+ neutrophils in tissues from EA men compared to AA men (p &lt; 0.0001). There was also increased CD66ce expression in cancer compared to benign tissue spots (p &lt;0.01), in low grade compared to higher grade cancer (p &lt; 0.0001), in cancer with PTEN loss versus intact PTEN (p &lt; 0.0001), and in ERG positive versus ERG negative cancer (p = 0.0011).

There was no association between CD66ce+ neutrophils and risk of metastasis or biochemical recurrence. CD68+ and CD163+ macrophages were abundant in organ donor specimens, while CD80 expression was minimal. Similar expression patterns were observed in benign regions of radical prostatectomy specimens. In analysis of TMAs, CD68, CD80 and CD163 were significantly increased in cancer compared to benign tissues (p &lt; 0.0001). CD163 expression was comparable between races, while CD80 expression was significantly higher in benign tissues from AA men compared to EA men (p = 0.0004). CD68, CD80 and CD163 expression were all significantly increased in benign spots from ERG positive versus ERG negative cases. In conclusion, there is increased infiltration of innate immune cells in the prostate tumor microenvironment of both AA and EA men, however the composition of innate immune cell infiltration varies between races. Our future studies aim to determine the influence of innate immune effector cells on PCa aggressiveness and outcomes.

Citation Format: Janielle P. Maynard, Jiayun Lu, Igor Vidal, Corinne E. Joshu, Angelo M. De Marzo, Karen S. Sfanos. Localization of macrophages and neutrophils in the prostate tumor microenvironment and their association with prostate cancer racial disparities [abstract]. In: Proceedings of the AACR Virtual Conference: Thirteenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2020 Oct 2-4. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(12 Suppl):Abstract nr PO-226.

Distinct Genomic Alterations in Prostate Tumors Derived from African American Men

We aim to understand, from acquired genetic alterations in tumors, why African American (AA) men are more likely to develop aggressive prostate cancer. By analyzing somatic mutations in 39 genes using deeper next-generation sequencing with an average depth of 2,522 reads for tumor DNA and genome-wide DNA copy-number alterations (CNA) in prostate cancer in a total of 171 AA/black men and comparing with those in 860 European American (EA)/white men, we here present several novel findings. First, >35% of AA men harbor damaging mutations in APC, ATM, BRCA2, KDM6A, KMT2C, KMT2D, MED12, ZFHX3, and ZMYM3, each with >1% of mutated copies. Second, among genes with >10% of mutated copies in tumor cells, ZMYM3 is the most frequently mutated gene in AA prostate cancer. In a patient's tumor with >96% frameshift mutations of ZMYM3, we find allelic imbalances in 10 chromosomes, including losses of five and gains of another four chromosomes, suggesting its role in maintaining genomic integrity. Third, when compared to prostate cancer in EA/white men, a higher frequency of CNAs of MYC, THADA, NEIL3, LRP1B, BUB1B, MAP3K7, BNIP3L and RB1, and a lower frequency of deletions of RYBP, TP53, and TMPRSS2-ERG are observed in AA/black men. Finally, for the above genes with higher frequency of CNAs in AA than in EA, deletion of MAP3K7, BNIP3L, NEIL3 or RB1, or gain of MYC significantly associates with both higher Gleason grade and advanced pathologic stage in AA/black men. Deletion of THADA associates with advanced pathologic stage only. IMPLICATIONS: A higher frequency of damaging mutation in ZMYM3 causing genomic instability along with higher frequency of altered genomic regions including deletions of MAP3K7, BNIP3L, RB1, and NEIL3, and gain of MYC appear to be distinct somatically acquired genetic alterations that may contribute to more aggressive prostate cancer in AA/black men.

Dickkopf-1 Can Lead to Immune Evasion in Metastatic Castration-Resistant Prostate Cancer

PURPOSE

Metastatic castration-resistant prostate cancer (mCRPC) with low androgen receptor (AR) and without neuroendocrine signaling, termed double-negative prostate cancer (DNPC), is increasingly prevalent in patients treated with AR signaling inhibitors and is in need of new biomarkers and therapeutic targets.

METHODS

Candidate genes enriched in DNPC were determined using differential gene expression analysis of discovery and validation cohorts of mCRPC biopsies. Laboratory studies were carried out in human mCRPC organoid cultures, prostate cancer (PCa) cell lines, and mouse xenograft models. Epigenetic studies were carried out in a rapid autopsy cohort.

RESULTS

Dickkopf-1 (DKK1) expression is increased in DNPC relative to prostate-specific antigen (PSA)-expressing mCRPC in the Stand Up to Cancer/Prostate Cancer Foundation discovery cohort (11.2 v 0.28 reads per kilobase per million mapped reads; q < 0.05; n = 117) and in the University of Washington/Fred Hutchinson Cancer Research Center cohort (9.2 v 0.99 fragments per kilobase of transcript per million mapped reads; P < .0001). DKK1 expression can be regulated by activated Wnt signaling in vitro and correlates with activating canonical Wnt signaling mutations and low PSA mRNA in mCRPC biopsies (P < .05). DKK1 hypomethylation was associated with increased DKK1 mRNA expression (Pearson r = -0.66; P < .0001) in a rapid autopsy cohort (n = 7). DKK1-high mCRPC biopsies are infiltrated with significantly higher numbers of quiescent natural killer (NK) cells (P < .005) and lower numbers of activated NK cells (P < .0005). Growth inhibition of the human PCa model PC3 by the anti-DKK1 monoclonal antibody DKN-01 depends on the presence of NK cells in a severe combined immunodeficient xenograft mouse model.

CONCLUSION

These results support DKK1 as a contributor to the immunosuppressive tumor microenvironment of DNPC. These data have provided the rationale for a clinical trial targeting DKK1 in mCRPC (ClinicalTrials.gov identifier: NCT03837353).

Prostate carcinogenesis: inflammatory storms

Prostate cancer is a major cause of cancer morbidity and mortality. Intra-prostatic inflammation is a risk factor for prostate carcinogenesis, with diet, chemical injury and an altered microbiome being causally implicated. Intra-prostatic inflammatory cell recruitment and expansion can ultimately promote DNA double-strand breaks and androgen receptor activation in prostate epithelial cells. The activation of the senescence-associated secretory phenotype fuels further 'inflammatory storms', with free radicals leading to further DNA damage. This drives the overexpression of DNA repair and tumour suppressor genes, rendering these genes susceptible to mutagenic insults, with carcinogenesis accelerated by germline DNA repair gene defects. We provide updates on recent advances in elucidating prostate carcinogenesis and explore novel therapeutic and prevention strategies harnessing these discoveries.

High Extratumoral Mast Cell Counts Are Associated with a Higher Risk of Adverse Prostate Cancer Outcomes

BACKGROUND

Given our previous findings that low intratumoral and high extratumoral mast cell numbers are associated with higher risk of biochemical recurrence after radical prostatectomy, we now assessed this relationship with race and the development of metastases.

METHODS

We stained for mast cell tryptase via IHC and fluorescent immunolabeling in 885 men across multiple tissue microarray sets designed to assess biomarkers in association with race and prostate cancer outcomes (median follow-up, 7.0 years).

RESULTS

Intratumoral and extratumoral mast cell counts were significantly lower in tissues from African-American compared with European-American men, but not within strata of cancer grade. There was no association between mast cell counts and ERG positivity, PTEN loss, or TP53 missense mutation. Higher minimum extratumoral mast cells were associated with an increased risk of biochemical recurrence [comparing highest with lowest tertiles: HR, 1.61; 95% confidence interval (CI), 1.12-2.29; P trend = 0.01]; this pattern was similar among European-American and African-American men and by grade of disease. There was no significant association between minimum intratumoral mast cell count and biochemical recurrence, overall or within strata of race and grade. Finally, high minimum number of extratumoral mast cells was associated with prostate cancer metastases (comparing highest with lowest tertiles: HR, 2.12; 95% CI, 1.24-3.63; P trend = 0.01).

CONCLUSIONS

High extratumoral mast cell numbers are associated with biochemical recurrence and the development of metastases after radical prostatectomy.

IMPACT

Higher numbers of benign tissue mast cells are associated with a higher risk of adverse outcomes after radical prostatectomy, including metastatic prostate cancer.

Racial Difference in Prostate Cancer Cell Telomere Lengths in Men with Higher Grade Prostate Cancer: A Clue to the Racial Disparity in Prostate Cancer Outcomes

BACKGROUND

Black men have worse prostate cancer outcomes following treatment than White men even when accounting for prognostic factors. However, biological explanations for this racial disparity have not been fully identified. We previously showed that more variable telomere lengths among cancer cells and shorter telomere lengths in cancer-associated stromal (CAS) cells individually and together ("telomere biomarker") are associated with prostate cancer-related death in surgically treated men independent of currently used prognostic indicators. Here, we hypothesize that Black-White differences in the telomere biomarker and/or in its components may help explain the racial disparity in prostate cancer outcomes.

METHODS

Black [higher grade (Gleason ≥4+3) = 34 and lower grade = 93] and White (higher grade = 34 and lower grade = 89) surgically treated men were frequency matched on age, pathologic stage, and grade. We measured telomere lengths in cancer and CAS cells using a robust telomere-specific FISH assay. Tissue microarray and grade-specific distributional cutoff points without regard to race were evaluated.

RESULTS

Among men with higher grade disease, the proportion of Black men (47.1%) with more variable cancer cell telomere lengths was 2.3-times higher (P = 0.02) than that in White men (20.6%). In contrast, among men with lower grade disease, cancer cell telomere length variability did not differ by race. The proportion of men with shorter CAS cell telomeres did not differ by race for either higher or lower grade disease.

CONCLUSIONS

A greater proportion of Black men with higher grade disease have an adverse prostate cancer cell telomere phenotype than White men with higher grade disease.

IMPACT

Our findings suggest a possible explanation for the racial disparity in prostate cancer outcomes.

Lactoferrin CpG Island Hypermethylation and Decoupling of mRNA and Protein Expression in the Early Stages of Prostate Carcinogenesis

Lactoferrin (LTF) is an iron-binding protein canonically known for its innate and adaptive immune functions. LTF may also act as a tumor suppressor with antiproliferative action. LTF is inactivated genetically or epigenetically in various cancers, and a CpG island spanning the transcriptional start site of LTF is hypermethylated in prostate cancer cell lines. We, therefore, hypothesized that LTF expression is silenced via CpG island hypermethylation in the early stages of prostate tumorigenesis carcinogenesis. Targeted methylation analysis was performed using a combination of methylated-DNA precipitation and methylation-sensitive restriction enzymes, and laser-capture microdissection followed by bisulfite sequencing on DNA isolated from prostate tissue samples, including both primary and metastatic disease. LTF mRNA in situ hybridization and LTF protein immunohistochemistry were also performed. We report that the LTF CpG island is frequently and densely methylated in high-grade prostatic intraepithelial neoplasia, primary prostate carcinoma, and metastases. We further report a decoupling of lactoferrin mRNA and protein expression, including in lesions where LTF mRNA has presumably been silenced via CpG island methylation. We conclude that LTF mRNA expression is silenced in prostate tumorigenesis via hypermethylation, supporting a role for LTF as a prostate cancer tumor suppressor gene. Likewise, the frequency at which the LTF CpG island is methylated across samples suggests it is an important and conserved step in prostate cancer initiation.

Inflammation-associated pathologies in a case of prostate schistosomiasis: Implications for a causal role in prostate carcinogenesis

BACKGROUND

Urogenital infection with Schistosoma haematobium is a risk factor for the development of squamous cell carcinoma of the urinary bladder. The pathophysiology is thought to be mediated in part by inflammation, cellular damage, and bladder regeneration induced by the parasitic infection. Herein, we report an unusual case of schistosomiasis of the prostate that was found concurrent with prostate adenocarcinoma in a radical prostatectomy specimen from a man in the United States.

METHODS

The infecting Schistosoma species was characterized via histomorphology and acid-fast stain. The concurrent Gleason score 6 prostate cancer was assessed for ETS transcription factor ERG (ERG), phosphatase and tensin homolog (PTEN), p27, and p53 status using immunohistochemistry (IHC). Cellular proliferation and the presence of intermediate cells in prostatic atrophy were assessed via immunostaining for Ki67 and CK903, respectively.

RESULTS

Histomorphology and acid-fast stain of the infecting species were consistent with S. haematobium. We classified the Gleason score 6 prostate adenocarcinoma via IHC as ERG positive, PTEN intact, p27 intact, and without p53 nuclear accumulation. The prostatic epithelium immediately adjacent to the schistosomiasis-related granulomatous inflammation was atrophic and accompanied by increased cellular proliferation and the presence of intermediate cells. Upon literature review, we determined that prostate schistosomiasis is associated with a young age of prostate cancer diagnosis and highly aggressive prostate cancer.

CONCLUSIONS

This is a rare case of prostate schistosomiasis in the United States; however, prostate schistosomiasis occurs frequently in endemic areas. The patient had traveled to a Schistosoma-endemic region, which was the likely location of exposure to the parasite. To our knowledge, this is the first report of the association of proliferative inflammatory atrophy and intermediate cells with schistosomiasis of the prostate. We propose that prostate schistosomiasis may be considered as a risk factor for the development of prostate cancer in geographic regions where Schistosoma species are endemic.

A Prospective Study of the Urinary and Gastrointestinal Microbiome in Prepubertal Males

OBJECTIVE

To determine if urinary microbial communities similar to those described in adults exist in children and to profile the urinary and gastrointestinal microbiome in children presenting to urology for both routine and complex urologic procedures.

METHODS

Prepubertal boys (n = 20, ages 3 months-8 years; median age 15 months) who required elective urologic procedures were eligible. Urine samples were collected via sterile catheterization and fecal samples were obtained by rectal swabs. DNA was extracted from urine pellet and fecal samples and subjected to bacterial profiling via 16S rDNA Illumina sequencing and 16S rDNA quantitative polymerase chain reaction. We assessed within and between sample diversity and differential species abundance between samples.

RESULTS

Urine samples had low bacterial biomass that reflected the presence of bacterial populations. The most abundant genera detected in urine samples are not common to skin microbiota and several of the genera have been previously identified in the urinary microbiome of adults. We report presumably atypical compositional differences in both the urinary and gastrointestinal microbiome in children with prior antibiotic exposure and highlight an important case of a child who had undergone lifelong antibiotic treatment as prophylaxis for congenital abnormalities.

CONCLUSION

This study provides one of the first characterizations of the urinary microbiome in prepubertal males. Defining the baseline healthy microbiome in children may lay the foundation for understanding the long-term impact of factors such as antibiotic use in the development of a healthy microbiome as well as the development of future urologic and gastrointestinal diseases.

Molecular Pathology of High-Grade Prostatic Intraepithelial Neoplasia: Challenges and Opportunities

A better understanding of the early stages of prostate cancer initiation, potentially arising from precursor lesions, may fuel development of powerful approaches for prostate cancer prevention or interception. The best-known candidate for such a precursor lesion has been referred to as high-grade prostatic intraepithelial neoplasia (HGPIN). Although there is significant evidence supporting the notion that such HGPIN lesions can give rise to invasive adenocarcinomas of the prostate, there are also numerous complicating considerations and evidence that cloud the picture in many instances. Notably, recent evidence has suggested that some fraction of such lesions that are morphologically consistent with HGPIN may actually be invasive carcinomas masquerading as HGPIN-a state that we term "postinvasive intraepithelial carcinoma" (PIC). Although the prevalence of such PIC lesions is not fully understood, this and other factors can confound the potential of identifying prostate precursors that can be targeted for disease prevention, interception, or treatment. Here, we review our current understanding of the morphological and molecular pathological features of prostate cancer precursor lesions.

A role for paracrine interleukin-6 signaling in the tumor microenvironment in prostate tumor growth

BACKGROUND

Interleukin-6 (IL-6) is a mediator of inflammation that can facilitate prostate cancer progression. We previously demonstrated that IL-6 is present in the prostate tumor microenvironment and is restricted almost exclusively to the stromal compartment. The present study examined the influence of paracrine IL-6 signaling on prostate tumor growth using allograft models of mouse prostate cancer (TRAMP-C2), colon cancer (MC38), and melanoma (B16) cell lines in wildtype (WT) and IL-6 knockout (IL-6^-/- ) mice.

METHODS

Cells were implanted into WT or IL-6^-/- mice and tumor sizes were measured at a 3 to 4 day interval. Serum, tumors, and other organs were collected for IL-6 analysis by ELISA and RNA in situ hybridization (RISH).

RESULTS

There was a significant reduction in TRAMP-C2 and B16 tumor size grown in IL-6^-/- mice versus WT mice (P = 0.0006 and P = 0.02, respectively). This trend was not observed for the MC38 cell line. RISH analysis of TRAMP-C2 tumors grown in WT mice showed that cells present in the tumor microenvironment were the primary source of IL-6 mRNA, not the TRAMP-C2 cells. Serum IL-6 ELISA analyses showed an increase in the circulating levels of IL-6 in WT mice bearing TRAMP-C2 tumors. Similar phospho-STAT3 expression and tumor vascularization were observed in TRAMP-C2 tumors grown in WT and IL-6^-/- mice.

CONCLUSIONS

Our results are consistent with previous studies in prostate cancer patients demonstrating that paracrine IL-6 production in the tumor microenvironment may influence tumor growth. Additionally, these data provide evidence that elevated systemic IL-6 levels may be involved in tumor growth regulation in prostate cancer, and are not simply caused by or indicative of tumor burden.

If this is true, what does it imply? How end-user antibody validation facilitates insights into biology and disease

Antibodies are employed ubiquitously in biomedical sciences, including for diagnostics and therapeutics. One of the most important uses is for immunohistochemical (IHC) staining, a process that has been improving and evolving over decades. IHC is useful when properly employed, yet misuse of the method is widespread and contributes to the "reproducibility crisis" in science. We report some of the common problems encountered with IHC assays, and direct readers to a wealth of literature documenting and providing some solutions to this problem. We also describe a series of vignettes that include our approach to analytical validation of antibodies and IHC assays that have facilitated a number of biological insights into prostate cancer and the refutation of a controversial association of a viral etiology in gliomas. We postulate that a great deal of the problem with lack of accuracy in IHC assays stems from the lack of awareness by researchers for the critical necessity for end-users to validate IHC antibodies and assays in their laboratories, regardless of manufacturer claims or past publications. We suggest that one reason for the pervasive lack of end-user validation for research antibodies is that researchers fail to realize that there are two general classes of antibodies employed in IHC. First, there are antibodies that are "clinical grade" reagents used by pathologists to help render diagnoses that influence patient treatment. Such diagnostic antibodies, which tend to be highly validated prior to clinical implementation, are in the vast minority (e.g. < 500). The other main class of antibodies are "research grade" antibodies (now numbering >3 800 000), which are often not extensively validated prior to commercialization. Given increased awareness of the problem, both the United States, National Institutes of Health and some journals are requiring investigators to provide evidence of specificity of their antibody-based assays.

Corpora amylacea in prostatectomy tissue and associations with molecular, histological, and lifestyle factors

BACKGROUND

Corpora amylacea are amyloid bodies commonly found adjacent to damaged prostate epithelium. Little is known about their formation or function. The current study sought to characterize corpora amylacea in prostate tissue and to describe their relationship with clinical, histological, molecular, and lifestyle factors, especially with chronic inflammation which is associated with aggressive disease.

METHODS

We studied a cohort of 355 men with prostate cancer and tissue specimens from the Health Professionals Follow-Up Study. Pathologists examined H&E slides and undertook a standardized review for histologic data and inflammation. Trained observers counted corpora amylacea within the benign and predominately tumor areas. Immunohistochemistry biomarkers were available from tissue microarrays. We used multivariable logistic regression to estimate odds ratios (OR) and 95% confidence intervals (CI) to assess associations of chronic inflammation, clinical, histological, molecular, and lifestyle factors with the presence of corpora amylacea.

RESULTS

Corpora amylacea were present in benign tissue area for 298 men (84%). Specimens with moderate-to-severe chronic inflammation were more likely to have corpora amylacea in benign regions (OR = 5.4 95%CI 1.9, 15.6). Moreover, corpora amylacea were more common in men with higher body mass index (OR = 1.13 95%CI 1.01, 1.26). In contrast, Gleason grade (OR = 0.4 95%CI 0.2, 0.8), proliferation index (OR = 0.6 95%CI 0.3, 1.2) and the presence of the TMPRSS2:ERG fusion (OR = 0.4 95%CI 0.2, 0.8) were inversely associated with corpora amylacea presence. TURP specimens were less likely to have corpora amylacea than prostatectomy specimens (OR = 0.12 95%CI 0.03, 0.47). Age, PSA, stage, biomarkers of angiogenesis and PTEN, and vasectomy were not significantly associated with corpora amylacea.

CONCLUSION

Corpora amylacea were common among men with prostate cancer and were associated with pro-inflammatory factors, some markers of less aggressive disease, and lack of the TMPRSS2:ERG fusion.

Association of tumor-infiltrating T-cell density with molecular subtype, racial ancestry and clinical outcomes in prostate cancer

The inflammatory microenvironment plays an important role in the pathogenesis and progression of tumors and may be associated with somatic genomic alterations. We examined the association of tumor-infiltrating T-cell density with clinical-pathologic variables, tumor molecular subtype, and oncologic outcomes in surgically treated primary prostate cancer occurring in patients of European-American or African-American ancestry. We evaluated 312 primary prostate tumors, enriched for patients with African-American ancestry and high grade disease. Tissue microarrays were immunostained for CD3, CD8, and FOXP3 and were previously immunostained for ERG and PTEN using genetically validated protocols. Image analysis for quantification of T-cell density in tissue microarray tumor spots was performed. Automated quantification of T-cell densities in tumor-containing regions of tissue microarray spots and standard histologic sections were correlated (r = 0.73, p < 0.00001) and there was good agreement between visual and automated T-cell density counts on tissue microarray spots (r = 0.93, p < 0.00001). There was a significant correlation between CD3+, CD8+, and FOXP3+ T-cell densities (p < 0.00001), but these were not associated with most clinical or pathologic variables. Increased T-cell density was significantly associated with ERG positivity (median 309 vs. 188 CD3+ T cells/mm2; p = 0.0004) and also with PTEN loss (median 317 vs. 192 CD3+ T cells/mm2; p = 0.001) in the combined cohort of matched European-American and African-American ancestry patients. The same association or a similar trend was present in patients of both ancestries when analyzed separately. When the African-American patients from the matched race set were combined with a separate high grade set of African-American cases, there was a weak association of increased FOXP3+ T-cell densities with increased risk of metastasis in multivariable analysis. Though high T-cell density is associated with specific molecular subclasses of prostate cancer, we did not find an association of T-cell density with racial ancestry.

Abstract 5136: Development of an RNA hybridization technique for the in situ visualization of bacteria in cancer tissues

There is currently a great interest in understanding direct interactions between human-associated microbial populations and the tumor microenvironment. In this study, we aimed to develop a chromogenic in situ hybridization (CISH) assay for universal detection of bacteria in formalin fixed paraffin embedded (FFPE) cancer tissues. This was accomplished using the RNAscope assay (Advanced Cell Diagnostics) with a CISH probe set designed to target the most highly conserved region in the bacterial 16S ribosomal RNA (rRNA) gene. Optimization of the 16S rRNA CISH assay was conducted using FFPE mouse colon, Mycobacterium tuberculosis infected rabbit lung, and Propionibacterium acnes infected mouse prostate tissues. Positive control (peptidylprolyl isomerase B- PPIB) and negative control (maize –Zm) stains were also conducted on the tissues. We additionally developed immunohistochemistry (IHC) assays with antibodies against lipopolysaccharide (LPS) and lipoteichoic acid (LTA) to visualize gram negative and gram positive bacteria, respectively, as a means to verify the results of the CISH assay. As our laboratory has a specific interest in the interactions between prostate infections and prostate cancer, we used this technique to interrogate a series of 10 radical prostatectomy specimens that contained a very high degree of acute and chronic inflammation, and were suspicious for the presence of an infectious organism. Both CISH and IHC were conducted in FFPE radical prostatectomy samples.

The 16S rRNA CISH assay detected bacteria in all of the control tissues. Interestingly, 3 of the 10 human radical prostatectomy samples that we examined showed bacterial 16S rRNA signal concentrated in areas with acute inflammation where the glandular lumens were filled with neutrophils. Two of the radical prostatectomy samples that showed positive bacterial 16S rRNA CISH signal also showed positive LPS staining indicative of the presence of gram negative bacteria. The remaining positive sample was suspicious for a gram positive intracellular organism. This study shows preliminary data supporting robust detection of bacteria in a subset of human prostate samples. We expect the frequency of bacterial infections of this nature present in radical prostatectomy specimens would be low, and that we were only able to identify these cases because we screened for samples with very high levels of inflammation. Detection of both bacterial RNA and protein in the tissues corroborates the strength and reliability of the 16S rRNA CISH. The use of these two methods concurrently can provide valuable information on bacterial presence in a range of clinical samples. In the future, we plan to use these methods to probe for bacterial presence and in understanding the spatial dynamics of the urinary microbiome. We expect that this method may also be of broader use in the study of many infection-associated cancers.

Citation Format: Eva Shrestha, Karen S. Sfanos. Development of an RNA hybridization technique for the in situ visualization of bacteria in cancer tissues [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5136.

Abstract B54: The inflammatory microenvironment in prostate cancer racial disparities

Introduction: Prostate cancer (PCa) is the third leading cause of cancer death in American men. African American (AA) men are more likely to be diagnosed with advanced prostate cancer and are 2-3 times more likely to die from the disease than Caucasian American (CA) men. Chronic inflammation is implicated as a major risk factor for PCa, and genes involved in inflammatory pathways are reported as more prevalent in tumors from AA men versus CA men. Specifically, interleukin-1β (IL-1β), IL-6, IL-8, and IL-10 have consistently been identified as overexpressed in the tumor microenvironment of AA men. These interleukins are in involved in the attraction, activation, or maintenance of innate immune cells such as neutrophils and macrophages. However, it is not well understood where these interleukins are expressed in the prostate and by what cell types they produced. We aim to address these specific questions using a novel in situ hybridization technique. Uncovering the inflammatory topography of PCa may contribute to our understanding of chronic inflammation in tumor development and progression, particularly among AA men.

Methods: The expression pattern and cellular localization of IL-1β, IL-6, IL-8, and IL-10 were evaluated using a highly specific RNA in situ hybridization assay (RNAscope) to analyze formalin-fixed, paraffin-embedded tissues of low-grade (Gleason ≤ 3+4) and higher-grade (Gleason ≥ 4+3) PCa from AA and CA men. Immunohistochemical analysis of neutrophils (CD66ce) and macrophages (CD68) was used to assess the expression pattern of these immune cells within the same cohort.

Results: Limited IL-1β and IL-10 expression was observed across all samples. Consistent with our previous reports in CA men, IL-6 mRNA is not expressed in tumor cells and is largely confined to the stromal compartment. IL-6 expression was predominantly in endothelial cells and to a lesser extent in atrophic epithelial cells of both AA and CA men. IL-6 is also highly expressed in stromal cells in areas of acute inflammation. IL-8 was the most abundantly detected cytokine within our cohort. In benign regions, IL-8 expression was predominantly observed in epithelial cells in regions of prostatic atrophy. IL-8 expression was also apparent in multiple tumors, both in tumor cells and infiltrating immune cells. We also observed marked IL-8 expression in urothelial cells in a subset of cases. Interestingly, tumor-infiltrating neutrophils and a marked increase in tumor-infiltrating macrophages were observed within tumors in a subset of cases.

Conclusions: There is differential expression of cytokines among men with PCa. Our future studies aim to determine whether our results could help to explain the disparate burden of advanced PCa among AA men.

Citation Format: Janielle P. Maynard, Angelo M. De Marzo, Karen S. Sfanos. The inflammatory microenvironment in prostate cancer racial disparities [abstract]. In: Proceedings of the Tenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2017 Sep 25-28; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2018;27(7 Suppl):Abstract nr B54.

Abstract 5069: Inflammatory cytokine localization in the prostate tumor microenvironment and their association with prostate cancer racial disparities

Prostate cancer (PCa) is the 3rd leading cause of cancer-related deaths in American men. The major risk factors for PCa development include advanced age, family history and African ancestry. Chronic inflammation has been implicated as a major contributor to PCa and genes involved in inflammatory pathways are reported as more prevalent in tumors from African American (AA) versus Caucasian American (CA) men. Specifically, interleukin-1β (IL1β), IL6, IL8, and IL10 have been identified as over-expressed in the tumor microenvironment of AA men. These interleukins are in involved in the attraction, activation or maintenance of innate immune cells such as neutrophils and macrophages. However, it is not well understood where these interleukins are expressed in the prostate and what cell types produce them. We aim to address these specific questions in this study. The expression pattern and cellular localization of IL1β, IL6, IL8 and IL10 were evaluated using a highly specific RNA in situ hybridization (RISH) assay to analyze formalin-fixed paraffin-embedded tissues of low grade (Gleason ≤ 3+4) and higher grade (Gleason ≥ 4+3) PCa from AA and CA men. IL8 expression was additionally assessed by RISH in two unique tissue microarray (TMA) sets; i) primary prostate tumors obtained by radical prostatectomy from AA and CA men, matched for patient age, tumor grade and stage; ii) distant metastatic tissues obtained by autopsy. Immunohistochemical analysis of neutrophils (CD66ce) and RISH for macrophages (CD68) was used to assess the expression pattern of these immune cells within the same cohorts. Limited IL1β and IL10 expression was observed across all cases. IL6 expression was largely confined to the stromal compartment in endothelial cells and areas of acute inflammation. Modest IL6 expression was observed in atrophic epithelial cells. IL6 was never seen in tumor cells. IL8 was the most abundantly detected cytokine within our cohort and was significantly increased in higher grade cases. In benign regions, IL8 expression was predominantly observed in epithelial cells in regions of prostatic atrophy and in areas surrounding corpora amylacea. We observed marked IL8 expression in urothelial cells in most cases. IL8 expression was also apparent in multiple tumors, both in tumor cells and infiltrating immune cells. Tumor-infiltrating macrophages were markedly increased within a subset of tumors, but did not appear to express IL8. Conversely, a subset of neutrophils expressed IL8. Neutrophils were significantly increased in benign tissues from men with higher grade PCa, particularly in AA men. IL8 expression was also observed in a subset of distant metastases, particularly in liver metastases. There is differential expression of cytokines among men with PCa, and IL8 is the most abundant among the ones we analyzed. Our future studies aim to determine a role for IL8 in prostate carcinogenesis.

Citation Format: Janielle P. Maynard, Onur Ertunc, Angelo M. De Marzo, Karen S. Sfanos. Inflammatory cytokine localization in the prostate tumor microenvironment and their association with prostate cancer racial disparities [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5069.

Abstract 129: Biobanking and feasibility considerations for prostate cancer gastrointestinal microbiome studies

The human microbiome may play a role in prostate health and disease as both direct and indirect interactions. Direct interactions between microbiota and prostate cancer include prostate infections, inflammation, prostatitis, and potentially interactions with the urinary microbiome. Indirectly, the gastrointestinal (GI) microbiota may influence prostate cancer via xenobiotic metabolism, augmentation of treatment response, and contributions to systemic inflammation and cytokines. In the present study, we are seeking to understand how different prostate cancer treatments may be affected by the microbial composition of the GI tract. We are currently developing a biorepository of fecal specimens from prostate cancer patients in different clinical states of disease. A key question during the planning phase of this biorepository was if samples can be collected and banked in the form of a rectal swab, instead of the more traditional method of a stool sample. Rectal swabs provide an advantage over collection of stool specimens in that they are easily collected (the patient can self-collect) in a standardized, “on demand” fashion during routine patient visits. Therefore, a pilot study was undertaken to compare the microbial profile of samples collected via both methods from the same individual. We concomitantly collected both stool samples and rectal swabs from 6 patients undergoing active surveillance for prostate cancer at the Johns Hopkins Hospital. All samples were stored at -80°C until we were ready to isolate bacterial DNA. DNA was extracted with a phenol:chloroform based protocol that we have optimized for microbiome studies that includes multiple enzyme digest and bead beating. We conducted Illumina amplicon sequencing of PCR products amplified with universal primers designed against the V6 hypervariable region of the bacterial 16S rRNA gene. We tested our sequencing strategy against Microbiome Reference Standards obtained from American Type Culture Collection (ATCC). The results of our analysis from prostate cancer patients indicated high similarity of bacterial profiles obtained for matched stool and swabs in 4 of the 6 patients. In both of the cases that were dissimilar, there was a greater representation of Enterobacteriaceae in the stool sample versus the swab. We conclude that collection of rectal swabs is a more feasible and convenient means of sampling the GI microbiota in prostate cancer patients, especially when aiming to conduct longitudinal studies with multiple sample collections to correlate microbiota profiles to treatments and/or treatment response. Due to the differences that were identified, we recommend deciding on the sample collection method at the onset of biobanking, and keeping the sampling method consistent throughout.

Citation Format: Sarah E. Ernst, Mark C. Markowski, Anuj Gupta, Sarah J. Wheelan, H. Ballentine Carter, Alan W. Partin, Cynthia L. Sears, Karen S. Sfanos. Biobanking and feasibility considerations for prostate cancer gastrointestinal microbiome studies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 129.

Phage Therapy in Prostatitis: Recent Prospects

Prostatitis has various etiology including bacterial infection and dysregulated immunity; some of its forms remain a serious therapeutic challenge. Inflammation occurs in all forms of this disorder and is proposed to predispose to the development of prostate cancer (PC). There are reports that phage therapy is effective in chronic bacterial prostatitis. Recent findings suggest that phages not only eliminate bacteria, but also mediate immunomodulating (for example, anti-inflammatory) functions. The immunomodulating effects of phages could be beneficial in treating all forms of prostatitis and play some role in the prevention of the development of PC. As the etiological factors contributing to the majority of prostatitis cases remains largely unknown, and management options are often likewise limited, phage therapy merits further research as an attractive therapeutic option given its immunomodulating effects irrespective of the underlying causative factor(s).

The microbiome in prostate inflammation and prostate cancer

BACKGROUND

The human microbiome may influence prostate cancer initiation and/or progression through both direct and indirect interactions. To date, the majority of studies have focused on direct interactions including the influence of prostate infections on prostate cancer risk and, more recently, on the composition of the urinary microbiome in relation to prostate cancer. Less well understood are indirect interactions of the microbiome with prostate cancer, such as the influence of the gastrointestinal or oral microbiota on pro- or anti-carcinogenic xenobiotic metabolism, and treatment response.

METHODS

We review the literature to date on direct and indirect interactions of the microbiome with prostate inflammation and prostate cancer.

RESULTS

Emerging studies indicate that the microbiome can influence prostate inflammation in relation to benign prostate conditions such as prostatitis/chronic pelvic pain syndrome and benign prostatic hyperplasia, as well as in prostate cancer. We provide evidence that the human microbiome present at multiple anatomic sites (urinary tract, gastrointestinal tract, oral cavity, etc.) may play an important role in prostate health and disease.

CONCLUSIONS

In health, the microbiome encourages homeostasis and helps educate the immune system. In dysbiosis, a systemic inflammatory state may be induced, predisposing remote anatomical sites to disease, including cancer. The microbiome's ability to affect systemic hormone levels may also be important, particularly in a disease such as prostate cancer that is dually affected by estrogen and androgen levels. Due to the complexity of the potential interconnectedness between prostate cancer and the microbiome, it is vital to further explore and understand the relationships that are involved.

Targeting Toll-like Receptors in Cancer Prevention

There is a pressing need for the development of new prevention strategies for the most common worldwide malignancy, nonmelanoma skin cancer (NMSC), as sun protection efforts have not proven to be completely effective. Interestingly, despite the known circumstance that individuals undergoing chronic immunosuppression are at a substantially increased risk for developing NMSC, in this issue of Cancer Prevention Research, Blohm-Mangone and colleagues provide new evidence that topical application of the Toll-like receptor 4 (TLR4) antagonist resatorvid may be efficacious as a chemopreventive agent in NMSC specifically via blocking UV-induced inflammatory signaling. These new findings highlight a potentially delicate dichotomy between the role of innate immune receptors in the normal, protective immunosurveillance of damaged cells in the skin and the pathogenic UV-induced overstimulation of cutaneous inflammation that promotes photocarcinogenesis. Given the tremendous cancer burden incurred by NMSC, further exploration of the use of TLR4 antagonists in NMSC chemoprevention strategies is certainly warranted. Cancer Prev Res; 11(5); 251-4. ©2018 AACRSee related article by Blohm-Mangone et al., p. 265.