Heterogeneity of human prostate carcinoma-associated fibroblasts implicates a role for subpopulations in myeloid cell recruitment.

BACKGROUND: Carcinoma-associated fibroblasts (CAF) are a heterogeneous group of cells within the tumor microenvironment (TME) that can promote tumorigenesis in the prostate. By understanding the mechanism(s) by which CAF contributes to tumor growth, new therapeutic targets for the management of this disease may be identified. These studies determined whether unique sub-populations of human prostate CAF can be identified and functionally characterized. METHODS: Single-cell RNA-seq of primary human prostate CAF followed by unsupervised clustering was utilized to generate cell clusters based on differentially expressed (DE) gene profiles. Potential communication between CAF and immune cells was analyzed using in vivo tissue recombination by combining CAF or normal prostate fibroblasts (NPF) with non-tumorigenic, initiated prostate epithelial BPH-1 cells. Resultant grafts were assessed for inflammatory cell recruitment. RESULTS: Clustering of 3321 CAF allows for visualization of six subpopulations, demonstrating heterogeneity within CAF. Sub-renal capsule recombination assays show that the presence of CAF significantly increases myeloid cell recruitment to resultant tumors. This is supported by significantly increased expression of chemotactic chemokines CCL2 and CXCL12 in large clusters compared to other subpopulations. Bayesian analysis topologies also support differential communication signals between chemokine-related genes of individual clusters. Migration of THP-1 monocyte cells in vitro is stimulated in the presence of CAF conditioned medium (CM) compared with NPF CM. Further in vitro analyses suggest that CAF-derived chemokine CCL2 may be responsible for CAF-stimulated migration of THP-1 cells, since neutralization of this chemokine abrogates migration capacity. CONCLUSIONS: CAF clustering based on DE gene expression supports the concept that clusters have unique functions within the TME, including a role in immune/inflammatory cell recruitment. These data suggest that CCL2 produced by CAF may be involved in the recruitment of inflammatory cells, but may also directly regulate the growth of the tumor. Further studies aimed at characterizing the subpopulation(s) of CAF which promote immune cell recruitment to the TME and/or stimulate prostate cancer growth and progression will be pursued.

Distinct expression patterns of SULT2B1b in human prostate epithelium.

BACKGROUND: SULT2B1b (sulfotransferase family cytosolic 2B member 1b) catalyzes the sulfate conjugation of substrates such as cholesterol and oxysterols. Our laboratory has previously shown that SULT2B1b inhibition modulates androgen receptor signaling and induces apoptosis in prostate cancer cells. However, the functions of SULT2B1b in the prostate remain poorly understood. METHODS: We characterized the expression pattern of SULT2B1b in human benign prostate hyperplasia (BPH) as well as prostate cancer to determine the relationship between SULT2B1b and prostate diseases, using immunohistochemistry, immunofluorescence staining, immunoblot, and real-time polymerase chain reaction. RESULTS: SULT2B1b was strongly detected in the prostate epithelium but was absent in the stroma. Significantly lower SULT2B1b was found in primary cancer cells compared with adjacent normal epithelial cells. SULT2B1b further decreased in metastatic cancer cells. Most interestingly, we found, for the first time, that SULT2B1b was much more concentrated in the luminal layer than in the basal layer in both normal prostate and BPH samples. The stronger presence of SULT2B1b in luminal epithelial cells was confirmed by costaining with luminal and basal markers and in sorted paired luminal and basal cells. SULT2B1b expression was induced with prostate organoid differentiation. CONCLUSIONS: SULT2B1b inversely correlates with prostate cancer status, with the highest level in the normal epithelium and lowest in the advanced metastatic prostate cancer. Furthermore, SULT2B1b is mostly located within the luminal layer of the prostate epithelium, suggesting that it may be implicated in luminal differentiation.

PREVALENCE AND SIGNIFICANCE OF AN ULTRASONOGRAPHIC COLONIC MUSCULARIS HYPERECHOIC BAND PARALLELING THE SEROSAL LAYER IN DOGS.

The muscularis layer of the canine colon has been reported to appear homogeneously hypoechoic on ultrasonography. A hyperechoic band in the muscularis layer paralleling the serosal surface has been observed by authors in routine canine abdominal ultrasound examinations. The purpose of this prospective and retrospective cross-sectional study was to determine the prevalence of this lesion, characterize its ultrasonographic and postmortem histologic features, and correlate its presence with clinical signs of gastrointestinal disease. In the prospective study, all dogs that underwent routine abdominal ultrasonography by one of two observers during a 4-week period were included without any exclusion criteria. One observer reviewed ultrasound images and recorded the presence or absence of this lesion and its distribution, e.g. focal (< 2 cm long) or diffuse (> 2 cm long). In the retrospective study, all dogs that had both abdominal ultrasonography and necropsy from January 2011 to December 2013 were included without any exclusion criteria. Histologic examinations were performed by two observers and Masson's trichrome stain was used to identify fibrous collagen. Prevalence for the hyperechoic band was 32% in the prospective and 4.8% in the retrospective sample populations, respectively. The hyperechoic band appeared as diffuse, focal, or a combination of both. Histologic sections were available for six dogs. In a few cases, the lesion corresponded to the presence of fibrous tissue in the myenteric plexus or in the tunica muscularis. None of the dogs had a history of diarrhea. Findings supported the hypothesis that a colonic muscularis hyperechoic band paralleling the serosal layer in dogs could be a normal variant rather than a marker of disease.

Infiltrating lipid-rich macrophage subpopulations identified as a regulator of increasing prostate size in human benign prostatic hyperplasia.

Macrophages exhibit marked phenotypic heterogeneity within and across disease states, with lipid metabolic reprogramming contributing to macrophage activation and heterogeneity. Chronic inflammation has been observed in human benign prostatic hyperplasia (BPH) tissues, however macrophage activation states and their contributions to this hyperplastic disease have not been defined. We postulated that a shift in macrophage phenotypes with increasing prostate size could involve metabolic alterations resulting in prostatic epithelial or stromal hyperplasia. Single-cell RNA-seq of CD45+ transition zone leukocytes from 10 large (>90 grams) and 10 small (<40 grams) human prostates was conducted. Macrophage subpopulations were defined using marker genes. BPH macrophages do not distinctly categorize into M1 and M2 phenotypes. Instead, macrophages with neither polarization signature preferentially accumulate in large versus small prostates. Specifically, macrophage subpopulations with altered lipid metabolism pathways, demarcated by TREM2 and MARCO expression, significantly accumulate with increased prostate volume. TREM2 + and MARCO + macrophage abundance positively correlates with patient body mass index and urinary symptom scores. TREM2+ macrophages have significantly higher neutral lipid than TREM2- macrophages from BPH tissues. Lipid-rich macrophages were observed to localize within the stroma in BPH tissues. In vitro studies indicate that lipid-loaded macrophages increase prostate epithelial and stromal cell proliferation compared to control macrophages. These data define two new BPH immune subpopulations, TREM2+ and MARCO+ macrophages, and suggest that lipid-rich macrophages may exacerbate lower urinary tract symptoms in patients with large prostates. Further investigation is needed to evaluate the therapeutic benefit of targeting these cells in BPH.

Inflammation Impacts Androgen Receptor Signaling in Basal Prostate Stem Cells Through Interleukin 1 Receptor Antagonist.

The majority of patients with benign prostate hyperplasia (BPH) exhibit chronic prostate inflammation and the extent of inflammation correlates with the severity of symptoms. How inflammation contributes to prostate enlargement and/or BPH symptoms and the underlying mechanisms are not clearly understood. We established a unique mouse model Prostate Ovalbumin Expressing Transgenic 3 (POET3) that mimics chronic non-bacterial prostatitis in men to study the role of inflammation in prostate hyperplasia. After the injection of ovalbumin peptide-specific T cells, POET3 prostates exhibited an influx of inflammatory cells and an increase in pro-inflammatory cytokines that led to epithelial and stromal hyperplasia. We have previously demonstrated with the POET3 model that inflammation expands the basal prostate stem cell (bPSC) population and promotes bPSC differentiation in organoid cultures. In this study, we investigated the mechanisms underlying the impact of inflammation on bPSC. We found that AR activity was enhanced in inflamed bPSC and was essential for bPSC differentiation in organoid cultures. Most importantly, we identified, for the first time, interleukin 1 receptor antagonist (IL-1RA) as a key regulator of AR in basal stem cells. IL-1RA was one of the top genes upregulated by inflammation and inhibition of IL-1RA abrogated the enhanced AR nuclear accumulation and activity in organoids derived from inflamed bPSC. The mirroring effects of IL-1RA recombinant protein and IL-1α neutralizing antibody suggest that IL-1RA may function by antagonizing IL-1α inhibition of AR expression. Furthermore, we established a lineage tracing model to follow bPSC during inflammation and under castrate conditions. We found that inflammation induced bPSC proliferation and differentiation into luminal cells even under castrate conditions, indicating that AR activation driven by inflammation in bPSC is sufficient for their proliferation and differentiation under androgen-deprived conditions. However, proliferation of the differentiated bPSC in the luminal layer significantly diminished with castration, suggesting inflammation may not maintain AR activity in stromal cells, as stromal cells deprived of androgen after castration could no longer provide paracrine growth factors essential for luminal proliferation. Taken together, we have discovered novel mechanisms through which inflammation modulates AR signaling in bPSC and induces bPSC luminal differentiation that contributes to prostate hyperplasia.

Targeted elastin-like polypeptide fusion protein for near-infrared imaging of human and canine urothelial carcinoma.

Cystoscopic visualization of bladder cancer is an essential method for initial bladder cancer detection and diagnosis, transurethral resection, and monitoring for recurrence. We sought to develop a new intravesical imaging agent that is more specific and sensitive using a polypeptide based NIR (near-infrared) probe designed to detect cells bearing epidermal growth factor receptors (EGFR) that are overexpressed in 80% of urothelial carcinoma (UC) cases. The NIR imaging agent consisted of an elastin like polypeptide (ELP) fused with epidermal growth factor (EGF) and conjugated to Cy5.5 to give Cy5.5-N24-EGF as a NIR contrast agent. In addition to evaluation in human cells and tissues, the agent was tested in canine cell lines and tissue samples with naturally occurring invasive UC. Flow cytometry and confocal microscopy were used to test cell-associated fluorescence of the probe in T24 human UC cells, and in K9TCC-SH (high EGFR expression) and K9TCC-Original (low EGF expression) canine cell lines. The probe specifically engages these cells through EGFR within 15 min of incubation and reached saturation within a clinically relevant 1 h timeframe. Furthermore, ex vivo studies with resected canine and human bladder tissues showed minimal signal from normal adjacent tissue and significant NIR fluorescence labeling of tumor tissue, in good agreement with our in vitro findings. Differential expression of EGFR ex vivo was revealed by our probe and confirmed by anti-EGFR immunohistochemical staining. Taken together, our data suggests Cy5.5-ELP-EGF is a NIR probe with improved sensitivity and selectivity towards BC that shows excellent potential for clinical translation.

TNF is a potential therapeutic target to suppress prostatic inflammation and hyperplasia in autoimmune disease.

Autoimmune (AI) diseases can affect many organs; however, the prostate has not been considered to be a primary target of these systemic inflammatory processes. Here, we utilize medical record data, patient samples, and in vivo models to evaluate the impact of inflammation, as seen in AI diseases, on prostate tissue. Human and mouse tissues are used to examine whether systemic targeting of inflammation limits prostatic inflammation and hyperplasia. Evaluation of 112,152 medical records indicates that benign prostatic hyperplasia (BPH) prevalence is significantly higher among patients with AI diseases. Furthermore, treating these patients with tumor necrosis factor (TNF)-antagonists significantly decreases BPH incidence. Single-cell RNA-seq and in vitro assays suggest that macrophage-derived TNF stimulates BPH-derived fibroblast proliferation. TNF blockade significantly reduces epithelial hyperplasia, NFκB activation, and macrophage-mediated inflammation within prostate tissues. Together, these studies show that patients with AI diseases have a heightened susceptibility to BPH and that reducing inflammation with a therapeutic agent can suppress BPH.

Folate Receptor Beta Designates Immunosuppressive Tumor-Associated Myeloid Cells That Can Be Reprogrammed with Folate-Targeted Drugs.

Although immunotherapies of tumors have demonstrated promise for altering the progression of malignancies, immunotherapies have been limited by an immunosuppressive tumor microenvironment (TME) that prevents infiltrating immune cells from performing their anticancer functions. Prominent among immunosuppressive cells are myeloid-derived suppressor cells (MDSC) and tumor-associated macrophages (TAM) that inhibit T cells via release of immunosuppressive cytokines and engagement of checkpoint receptors. Here, we explore the properties of MDSCs and TAMs from freshly isolated mouse and human tumors and find that an immunosuppressive subset of these cells can be distinguished from the nonimmunosuppressive population by its upregulation of folate receptor beta (FRß) within the TME and its restriction to the TME. This FRß+ subpopulation could be selectively targeted with folate-linked drugs. Delivery of a folate-targeted TLR7 agonist to these cells (i) reduced their immunosuppressive function, (ii) increased CD8+ T-cell infiltration, (iii) enhanced M1/M2 macrophage ratios, (iv) inhibited tumor growth, (v) blocked tumor metastasis, and (vi) improved overall survival without demonstrable toxicity. These data reveal a broadly applicable strategy across tumor types for reprogramming MDSCs and TAMs into antitumorigenic immune cells using a drug that would otherwise be too toxic to administer systemically. The data also establish FRß as the first marker that distinguishes immunosuppressive from nonimmunosuppressive subsets of MDSCs and TAMs. Because all solid tumors accumulate MDSCs and TAMs, a general strategy to both identify and reprogram these cells should be broadly applied in the characterization and treatment of multiple tumors. SIGNIFICANCE: FRß serves as both a means to identify and target MDSCs and TAMs within the tumor, allowing for delivery of immunomodulatory compounds to tumor myeloid cells in a variety of cancers.

Identification of LIMK2 as a therapeutic target in castration resistant prostate cancer.

This study identified LIMK2 kinase as a disease-specific target in castration resistant prostate cancer (CRPC) pathogenesis, which is upregulated in response to androgen deprivation therapy, the current standard of treatment for prostate cancer. Surgical castration increases LIMK2 expression in mouse prostates due to increased hypoxia. Similarly, human clinical specimens showed highest LIMK2 levels in CRPC tissues compared to other stages, while minimal LIMK2 was observed in normal prostates. Most notably, inducible knockdown of LIMK2 fully reverses CRPC tumorigenesis in castrated mice, underscoring its potential as a clinical target for CRPC. We also identified TWIST1 as a direct substrate of LIMK2, which uncovered the molecular mechanism of LIMK2-induced malignancy. TWIST1 is strongly associated with CRPC initiation, progression and poor prognosis. LIMK2 increases TWIST1 mRNA levels upon hypoxia; and stabilizes TWIST1 by direct phosphorylation. TWIST1 also stabilizes LIMK2 by inhibiting its ubiquitylation. Phosphorylation-dead TWIST1 acts as dominant negative and fully prevents EMT and tumor formation in vivo, thereby highlighting the significance of LIMK2-TWIST1 signaling axis in CRPC. As LIMK2 null mice are viable, targeting LIMK2 should have minimal collateral toxicity, thereby improving the overall survival of CRPC patients.

Targeting Plk1 to Enhance Efficacy of Olaparib in Castration-Resistant Prostate Cancer.

Olaparib is an FDA-approved PARP inhibitor (PARPi) that has shown promise as a synthetic lethal treatment approach for BRCA-mutant castration-resistant prostate cancer (CRPC) in clinical use. However, emerging data have also shown that even BRCA-mutant cells may be resistant to PARPi. The mechanistic basis for these drug resistances is poorly understood. Polo-like kinase 1 (Plk1), a critical regulator of many cell-cycle events, is significantly elevated upon castration of mice carrying xenograft prostate tumors. Herein, by combination with Plk1 inhibitor BI2536, we show a robust sensitization of olaparib in 22RV1, a BRCA1-deficient CRPC cell line, as well as in CRPC xenograft tumors. Mechanistically, monotherapy with olaparib results in an override of the G1-S checkpoint, leading to high expression of Plk1, which attenuates olaparib's overall efficacy. In BRCA1 wild-type C4-2 cells, Plk1 inhibition also significantly increases the efficacy of olaparib in the presence of p53 inhibitor. Collectively, our findings not only implicate the critical role of Plk1 in PARPi resistance in BRCA-mutant CRPC cells, but also shed new light on the treatment of non-BRCA-mutant patient subgroups who might also respond favorably to PARPi. Mol Cancer Ther; 16(3); 469-79. ©2017 AACR.