The inflammatory microenvironment and microbiome in prostate cancer development

Chronic inflammation promotes the development of several types of solid cancers and might contribute to prostate carcinogenesis. This hypothesis partly originates in the frequent observation of inflammatory cells in the prostate microenvironment of adult men. Inflammation is associated with putative prostate cancer precursor lesions, termed proliferative inflammatory atrophy. Inflammation might drive prostate carcinogenesis via oxidative stress and generation of reactive oxygen species that induce mutagenesis. Additionally, inflammatory stress might cause epigenetic alterations that promote neoplastic transformation. Proliferative inflammatory atrophy is enriched for proliferative luminal epithelial cells of intermediate phenotype that might be prone to genomic alterations leading to prostatic intraepithelial neoplasia and prostate cancer. Studies in animals suggest that inflammatory changes in the prostate microenvironment contribute to reprogramming of prostate epithelial cells, a possible step in tumour initiation. Prostatic infection, concurrent with epithelial barrier disruption, might be a key driver of an inflammatory microenvironment; the discovery of a urinary microbiome indicates a potential source of frequent exposure of the prostate to a diverse number of microorganisms. Hence, current evidence suggests that inflammation and atrophy are involved in prostate carcinogenesis and suggests a role for the microbiome in establishing an inflammatory prostate microenvironment that might promote prostate cancer development and progression.

Profiling the Urinary Microbiome in Men with Positive versus Negative Biopsies for Prostate Cancer

PURPOSE

Studies demonstrating bacterial DNA and cultivable bacteria in urine samples have challenged the clinical dogma that urine is sterile. Furthermore, studies now indicate that dysbiosis of the urinary microbiome is associated with pathological conditions. We propose that the urinary microbiome may influence chronic inflammation observed in the prostate, leading to prostate cancer development and progression. Therefore, we profiled the urinary microbiome in men with positive vs negative biopsies for prostate cancer.

MATERIALS AND METHODS

Urine was collected from men prior to biopsy for prostate cancer. DNA was extracted from urine pellet samples and subjected to bacterial 16S rDNA Illumina® sequencing and 16S rDNA quantitative polymerase chain reaction. We determined the association between bacterial species and the presence or absence of cancer, cancer grade, and type and degree of prostate inflammation.

RESULTS

Urine samples revealed diverse bacterial populations. There were no significant differences in α or β diversity and no clear hierarchical clustering of benign or cancer samples. We identified a cluster of pro-inflammatory bacteria previously implicated in urogenital infections in a subset of samples. Many species, including known uropathogens, were significantly and differentially abundant among cancer and benign samples, in low vs higher grade cancers and in relation to prostate inflammation type and degree.

CONCLUSIONS

To our knowledge we report the most comprehensive study to date of the male urinary microbiome and its relationship to prostate cancer. Our results suggest a prevalence of pro-inflammatory bacteria and uropathogens in the urinary tract of men with prostate cancer.

AIM1 is an actin-binding protein that suppresses cell migration and micrometastatic dissemination

A defining hallmark of primary and metastatic cancers is the migration and invasion of malignant cells. These invasive properties involve altered dynamics of the cytoskeleton and one of its major structural components β-actin. Here we identify AIM1 (absent in melanoma 1) as an actin-binding protein that suppresses pro-invasive properties in benign prostate epithelium. Depletion of AIM1 in prostate epithelial cells increases cytoskeletal remodeling, intracellular traction forces, cell migration and invasion, and anchorage-independent growth. In addition, decreased AIM1 expression results in increased metastatic dissemination in vivo. AIM1 strongly associates with the actin cytoskeleton in prostate epithelial cells in normal tissues, but not in prostate cancers. In addition to a mislocalization of AIM1 from the actin cytoskeleton in invasive cancers, advanced prostate cancers often harbor AIM1 deletion and reduced expression. These findings implicate AIM1 as a key suppressor of invasive phenotypes that becomes dysregulated in primary and metastatic prostate cancer.

Invasion of malignant cells involves changes in cytoskeleton dynamics. Here the authors identify absent in melanoma 1 as an actin binding protein and show that it regulates cytoskeletal remodeling and cell migration in prostate epithelial cells, acting as a metastatic suppressor in cancer cells.

A Novel Functional Splice Variant of AKT3 Defined by Analysis of Alternative Splice Expression in HPV-Positive Oropharyngeal Cancers

The incidence of HPV-related oropharyngeal squamous cell carcinoma (OPSCC) has increased more than 200% in the past 20 years. Recent genetic sequencing efforts have elucidated relevant genes in head and neck cancer, but HPV-related tumors have consistently shown few DNA mutations. In this study, we sought to analyze alternative splicing events (ASE) that could alter gene function independent of mutations. To identify ASE unique to HPV-related tumors, RNA sequencing was performed on 46 HPV-positive OPSCC and 25 normal tissue samples. A novel algorithm using outlier statistics on RNA-sequencing junction expression identified 109 splicing events, which were confirmed in a validation set from The Cancer Genome Atlas. Because the most common type of splicing event identified was an alternative start site (39%), MBD-seq genome-wide CpG methylation data were analyzed for methylation alterations at promoter regions. ASE in six genes showed significant negative correlation between promoter methylation and expression of an alternative transcriptional start site, including AKT3 The novel AKT3 transcriptional variant and methylation changes were confirmed using qRT-PCR and qMSP methods. In vitro silencing of the novel AKT3 variant resulted in significant growth inhibition of multiple head and neck cell lines, an effect not observed with wild-type AKT3 knockdown. Analysis of ASE in HPV-related OPSCC identified multiple alterations likely involved in carcinogenesis, including a novel, functionally active transcriptional variant of AKT3 Our data indicate that ASEs represent a significant mechanism of oncogenesis with untapped potential for understanding complex genetic changes that result in the development of cancer. Cancer Res; 77(19); 5248-58. ©2017 AACR.

Abstract 2415: Genome-wide alterations in gene expression of prostate cancer (PC) cells surviving neo-adjuvant androgen deprivation therapy

Background: Although androgen deprivation therapy initially decreases PC tumor burden, resistance to further androgen receptor (AR)-directed treatments or chemotherapy is inevitable once CRPC is established. We postulated that the stress of ADT triggers widespread alterations in expression that renders a metastable physiologic state conditioned by epigenetic changes that might be initially reversible by targeting non-androgen pathways. We conducted a pilot study to explore genome-wide expression alterations in PC foci surviving 3 months ADT (eADT).

Methods: mRNA from 7 frozen microdissected PC foci and normal counterparts (NC) were processed for RNA-seq. RNA-seq changes in eADT specimens were compared first with NC and the untreated PC in the TCGA PRAD (TCGA) database to castrate resistant (mCRPC) specimens in the dbGAP study phs000915.v1.p1database. The raw data (fastq files) was quantified using kallisto, normalized by TMM using R package edgeR, batch effects corrected using R package SVA. Analysis of differential gene expression by R package sleuth. Pathway and gene set by GSEA, GAGE/pathview packages for Gene Ontology (GO) and KEGG.

Results: TMPRSS2-ERG+, 5/7. Highest DEG in eADT vs. TCGA vs mCRPC were non-coding RNA’s. Among 17431 differentially regulated paths; GSEA of eADT vs TCGA or mCRPC: 341 (1.95%) and 1366 (7.84%) up- vs 46 (0.26%) and 59 (0.34%) down-regulated. KEGG paths, eADT vs. TCGA or mCRPC, 11 and 53 up vs. 2 and 3 down- respectively. Highly down- path in eADT vs TCGA (log q<10-17) was ribosomal vs. cell cycle and DNA replication in mCRPC. Six paths significantly up- in eADT vs TCGA or mCRPC: Wnt, adherence junction, steroid biosynthesis, unsaturated fatty acids, citrate cycle, ErbB. Calcium, MAPK, insulin, GnRH and Hedgehog were also up- in eADT vs mCRPC. AR full-length was marginally higher in eADT than TCGA and lower than mCRPC, no differences in gene targets.

Conclusions: This pilot data shows that ADT triggers a wide range of gene expression alterations that support PC cell survival and may be vulnerable to therapeutic targeting in addition to the androgen pathway. Validation of these findings is planned in a larger set of samples from the same bank.

Citation Format: Anna C. Ferrari, Hatem Sabaawy, Mark Stein, David Foran, Ying Chen, Srinivasan Yegnasubramanian. Genome-wide alterations in gene expression of prostate cancer (PC) cells surviving neo-adjuvant androgen deprivation therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2415. doi:10.1158/1538-7445.AM2017-2415

Androgen Receptor Splice Variants Are Not Substrates of Nonsense-Mediated Decay

BACKGROUND

Androgen receptor (AR) splice variants have been clinically associated with progressive cancer, castration-resistance, and resistance to AR antagonists and androgen synthesis inhibitors. AR variants can be generated by genomic alterations and alternative splicing, and their expression is androgen-regulated. There has been a suggestion that AR variants bearing premature termination codons and coding for truncated proteins should be regulated by the nonsense-mediated decay (NMD) mRNA surveillance pathway, suggesting that either the NMD pathway is dysfunctional in variant-expressing cell lines or that variants are somehow able to evade degradation by NMD.

METHODS

We first used siRNA knockdown of the NMD regulator, UPF1, in an NMD reporter assay to determine if this surveillance pathway is functioning normally in AR variant-expressing cell lines. We then used UPF1 knockdown to determine if expression of the AR variants ARV3 and ARV7 is affected by inhibition of NMD. Next, we analyzed androgen regulation of UPF1 and used transcript expression analysis to determine if there is any association between UPF1 expression, resistance, and ARV3 or ARV7 expression.

RESULTS

We found that the NMD pathway functions normally in the AR variant-expressing cell line 22Rv1 and that inhibition of NMD does not increase expression of ARV3 or ARV7. Furthermore, we found that expression of UPF1 is not androgen-regulated. We also found that UFP1 expression levels do not differentiate castration-sensitive from resistant cell line and that UPF1 expression does not correlate with expression of ARV3 or ARV7 in cells in which these variants are highly expressed.

CONCLUSION

This study eliminates a possible mechanism of regulation of certain AR variants. Future research into the regulation of AR variants should focus on other mechanisms to better understand the origin of these variants and to possibly inhibit their expression for the resensitization of resistant cancers. Prostate 77:829-837, 2017. © 2017 Wiley Periodicals, Inc.

c-Myc Antagonises the Transcriptional Activity of the Androgen Receptor in Prostate Cancer Affecting Key Gene Networks

Prostate cancer (PCa) is the most common non-cutaneous cancer in men. The androgen receptor (AR), a ligand-activated transcription factor, constitutes the main drug target for advanced cases of the disease. However, a variety of other transcription factors and signaling networks have been shown to be altered in patients and to influence AR activity. Amongst these, the oncogenic transcription factor c-Myc has been studied extensively in multiple malignancies and elevated protein levels of c-Myc are commonly observed in PCa. Its impact on AR activity, however, remains elusive. In this study, we assessed the impact of c-Myc overexpression on AR activity and transcriptional output in a PCa cell line model and validated the antagonistic effect of c-MYC on AR-targets in patient samples. We found that c-Myc overexpression partially reprogrammed AR chromatin occupancy and was associated with altered histone marks distribution, most notably H3K4me1 and H3K27me3. We found c-Myc and the AR co-occupy a substantial number of binding sites and these exhibited enhancer-like characteristics. Interestingly, c-Myc overexpression antagonised clinically relevant AR target genes. Therefore, as an example, we validated the antagonistic relationship between c-Myc and two AR target genes, KLK3 (alias PSA, prostate specific antigen), and Glycine N-Methyltransferase (GNMT), in patient samples. Our findings provide unbiased evidence that MYC overexpression deregulates the AR transcriptional program, which is thought to be a driving force in PCa.

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c-MYC and AR share one third of chromatin binding with enhancer-like features.

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c-MYC can repress the expression of a subset prostate cancer biomarkers, including PSA.

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c-MYC and AR antagonize the expression of, Glycine N-Methyltransferase (GNMT), responsible for sarcosine biosynthesis.

Prostate cancer is a heterogeneous disease. The most frequently used biomarker in clinical setting, a well described androgen receptor target gene, PSA, still performs poorly in stratifying patients at real risk of death due to the disease. Despite this, therapeutic approaches focus on suppressing androgen receptor signaling. However, this is only one of the recurrent alterations found in patients. This study focuses on c-MYC and the effects of its deregulation in advanced prostate cancer. We find that there is an inverse relationship between established biomarkers expression, including PSA. This inverse relationship could be used in clinics to select beneficial therapeutic approaches for a subset of prostate cancer cases.

Prostate cancer epigenetics and its clinical implications

Normal cells have a level of epigenetic programming that is superimposed on the genetic code to establish and maintain their cell identity and phenotypes. This epigenetic programming can be thought as the architecture, a sort of cityscape, that is built upon the underlying genetic landscape. The epigenetic programming is encoded by a complex set of chemical marks on DNA, on histone proteins in nucleosomes, and by numerous context-specific DNA, RNA, protein interactions that all regulate the structure, organization, and function of the genome in a given cell. It is becoming increasingly evident that abnormalities in both the genetic landscape and epigenetic cityscape can cooperate to drive carcinogenesis and disease progression. Large-scale cancer genome sequencing studies have revealed that mutations in genes encoding the enzymatic machinery for shaping the epigenetic cityscape are among the most common mutations observed in human cancers, including prostate cancer. Interestingly, although the constellation of genetic mutations in a given cancer can be quite heterogeneous from person to person, there are numerous epigenetic alterations that appear to be highly recurrent, and nearly universal in a given cancer type, including in prostate cancer. The highly recurrent nature of these alterations can be exploited for development of biomarkers for cancer detection and risk stratification and as targets for therapeutic intervention. Here, we explore the basic principles of epigenetic processes in normal cells and prostate cancer cells and discuss the potential clinical implications with regards to prostate cancer biomarker development and therapy.

Abstract LB-160: Human telomerase RNA component (hTR/TERC) is consistently overexpressed in prostate cancer, required for cell proliferation and is positively regulated by MYC

Introduction: Telomerase activity (TA) is increased in most human cancers (80 - 90%) as a mechanism to maintain telomere function, yet the complex regulatory mechanisms driving TA in different cancer types remain obscure. Telomerase consists of at least two essential elements, a catalytic component (TERT) and an RNA subunit (hTR or TERC). Early data showed that TERC was constitutively expressed at similar levels in different tissues and cancer and that TERT mRNA levels best correlated with enzymatic activity across normal tissues and cancer cells. However, accumulating evidence suggests a more important role for the regulation of TERC in telomere maintenance, as well as possible telomerase activity-independent functions. MYC (c-Myc) is overexpressed in most prostate cancers and is known to regulate TERT mRNA levels in a number of cell types and hence to drive TA. However, there are no prior studies of MYC regulation of TERC. We performed a comprehensive study of TERC expression in cancer cell lines and prostatic tissue, across normal, high grade prostatic intraepithelial neoplasia (PIN), primary carcinomas (PCa), and castrate resistant metastatic disease. We further explored MYC regulation of TERC in Pca and examined cell proliferation in TERC-depleted Pca cell lines.

Experiments and results: Using a novel chromogenic In Situ Hybridization (CISH) RNA assay in FFPE tissues, validated in cell lines by RT-PCR, we found consistent TERC overexpression in nuclei of PIN (p<0.001, N = 26 patients) and Pca cells (p<0.001, N = 66 patients), that was confirmed by qRT-PCR (n = 25) and RNAseq (n = 12) in tumor/benign frozen tissue pairs. There was no association with Gleason score or pathologic stage, and a weak correlation between TERC and TERT levels by RT-PCR. There was a correlation between TERC CISH and MYC protein expression in prostate tissue (Spearman 0.4540, p<0.0001). Further, we show: i) that forced reductions of MYC resulted in decreased TERC levels in 8 cancer cell lines (prostate, lung, breast, and colorectal); ii) MYC occupies the TERC locus by chromatin immunoprecipitation (ChIP); iii) there is a decrease in human TERC promoter activity with MYC silencing; iv) increased Terc levels in PIN and carcinoma in 2 different mouse models of prostate-restricted overexpression of MYC; and v) knockdown of TERC by siRNA resulted in reduced growth and decreased Ki-67 in TERC depleted human prostate cancer cells.

Conclusions: We report consistent overexpression of TERC in PIN and PCa and show the first evidence of MYC regulation of TERC. These studies suggest an important role for MYC-regulated TERC overexpression in human prostate cancer development and progression. Further studies are required to better understand the functional roles of TERC (e.g. TA mediated vs. other activity) in carcinogenesis of the prostate and other organ sites and its regulation by MYC.

Citation Format: Javier A. Baena Del Valle, Qizhi Zheng, Michael Rubenstein, Alan K. Meeker, Christopher M. Heaphy, Gretchen Hubbard, Charles J. Bieberich, Srinivasan Yegnasubramanian, David Esopi, Sarah J. Wheelan, Angelo M. De Marzo. Human telomerase RNA component (hTR/TERC) is consistently overexpressed in prostate cancer, required for cell proliferation and is positively regulated by MYC. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-160.

Abstract LB-379: A targeted, next-generation bisulfite sequencing approach to evaluate the influence of maternal pre-pregnancy body mass index and gestational weight gain on umbilical cord blood DNA methylation levels

Introduction: Offspring born to obese mothers and/or mothers who gain excess weight during pregnancy are at increased risk of obesity and metabolic disease later in life, both of which are risk factors for certain cancers. While the biological mechanisms underlying these associations are not well understood, evidence from animal models and limited data from human studies suggests that DNA methylation may play an important role. Thus, we evaluated the association of maternal pre-pregnancy body mass index (BMI) and gestational weight gain (GWG) with DNA methylation in umbilical cord blood DNA using a candidate gene approach.

Methods: This study includes 112 black and white mothers and their neonates in the Hormones in Umbilical Cord Blood Extended Study. Participants were enrolled in 2006-2007 from a prenatal clinic in Baltimore, MD. Self-reported, pre-pregnancy BMI was categorized as normal (<25.0 kg/m2), overweight (25.0 to <30.0 kg/m2) or obese (?30 kg/m2). GWG was obtained from the medical record and categorized with respect to pre-pregnancy BMI, according to U.S. guidelines. Data on demographics, lifestyle, and pregnancy characteristics were obtained from a prenatal questionnaire and the medical record. Candidate genes were chosen based on literature review (n = 29) and those genes related to obesity and cancer were prioritized. Cord blood leukocyte DNA methylation at these genes was quantified using bisulfite sequencing carried out with high-throughput, microfluidic PCR of bisulfite-converted DNA followed by next-generation sequencing. Generalized linear models with a binomial distribution were fit to assess associations of pre-pregnancy BMI (overweight/obese vs. normal) and GWG (more than vs. within/less than recommended) with DNA methylation. Models were adjusted for maternal and gestational age, smoking, parity, race, and infant sex. We adjusted p-values for the false discovery rate (FDR) and stratified all significant results by maternal race and infant sex.

Results: A total of 29 CpG sites in 14 genes were differentially methylated with respect to pre-pregnancy BMI (FDR p-value ?0.05). A total of 30 CpG sites in 15 genes were differentially methylated with respect to GWG (FDR p-value ?0.05). Four CpG sites were significantly differentially methylated in the same direction with respect to both maternal pre-pregnancy BMI and GWG (ANAPC7, CAB39, HEYL and SAPCD2). We observed differences by race and sex. In particular, in males, pre-pregnancy overweight/obesity and excess GWG were associated with increased DNA methylation patterns at a majority of the significant CpG sites.

Discussion: To our knowledge this study is one of the first to use targeted, next-generation bisulfite sequencing to quantify methylation in cord blood DNA. Our findings suggest maternal adiposity and GWG may influence DNA methylation of offspring genes, in a sex-specific manner. These findings warrant replication in large, prospective studies.

Funding: NCI T32 CA009314, P30 CA006973, U54 CA091409, and the JHSPH Doctoral Thesis Research Fund.

We wish to acknowledge Dr. Sarah Wheelan and Jennifer Meyers from the SKCCC Next Generation Sequencing Lab

Citation Format: Megan A. Clarke, David Esopi, Srinivasan Yegnasubramanian, Elizabeth A. Platz, Corinne E. Joshu. A targeted, next-generation bisulfite sequencing approach to evaluate the influence of maternal pre-pregnancy body mass index and gestational weight gain on umbilical cord blood DNA methylation levels. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-379.

Simultaneous quantitative determination of 5-aza-2'-deoxycytidine genomic incorporation and DNA demethylation by liquid chromatography tandem mass spectrometry as exposure-response measures of nucleoside analog DNA methyltransferase inhibitors

The epigenetic and anti-cancer activities of the nucleoside analog DNA methyltransferase (DNMT) inhibitors decitabine (5-aza-2'-deoxycytidine, DAC), azacitidine, and guadecitabine are thought to require cellular uptake, metabolism to 5-aza-2'-deoxycytidine triphosphate, and incorporation into DNA. This genomic incorporation can then lead to trapping and degradation of DNMT enzymes, and ultimately, passive loss of DNA methylation. To facilitate measurement of critical exposure-response relationships of nucleoside analog DNMT inhibitors, a sensitive and reliable method was developed to simultaneously quantitate 5-aza-2'-deoxycytidine genomic incorporation and genomic 5-methylcytosine content using LC-MS/MS. Genomic DNA was extracted and digested into single nucleosides. Chromatographic separation was achieved with a Thermo Hyperpcarb porous graphite column (100mm×2.1mm, 5μm) and isocratic elution with a 10mM ammonium acetate:acetonitrile with 0.1% formic acid (70:30, v/v) mobile phase over a 5min total analytical run time. An AB Sciex 5500 triple quadrupole mass spectrometer operated in positive electrospray ionization mode was used for the detection of 5-aza-2'-deoxycytidine, 2'-deoxycytidine, and 5-methyl-2'-deoxycytidine. The assay range was 2-400ng/mL for 5-aza-2'-deoxycytidine, 50-10,000ng/mL for 2'-deoxycytidine, and was 5-1000ng/mL for 5-methyl-2'-deoxycytidine. The assay proved to be accurate (93.0-102.2%) and precise (CV≤6.3%) across all analytes. All analytes exhibited long-term frozen digest matrix stability at -70°C for at least 117 days. The method was applied for the measurement of genomic 5-aza-2'-deoxycytidine and 5-methyl-2'-deoxycytidine content following exposure of in vitro cell culture and in vivo animal models to decitabine.

Androgen Deprivation Followed by Acute Androgen Stimulation Selectively Sensitizes AR-Positive Prostate Cancer Cells to Ionizing Radiation

PURPOSE

The current standard of care for patients with locally advanced prostate cancer is a combination of androgen deprivation and radiation therapy. Radiation is typically given with androgen suppression when testosterone levels are at their nadir. Recent reports have shown that androgen stimulation of androgen-deprived prostate cancer cells leads to formation of double-strand breaks (DSB). Here, we exploit this finding and investigate the extent and timing of androgen-induced DSBs and their effect on tumor growth following androgen stimulation in combination with ionizing radiation (IR).

EXPERIMENTAL DESIGN

Androgen-induced DNA damage was assessed by comet assays and γH2A.X foci formation. Effects of androgen stimulation and radiation were determined in vitro and in vivo with xenograft models.

RESULTS

We document that androgen treatment of androgen-deprived prostate cancer cell lines resulted in a dose- and time-dependent induction of widespread DSBs. Generation of these breaks was dependent on androgen receptor and topoisomerase II beta but not on cell-cycle progression. In vitro models demonstrated a synergistic interaction between IR and androgen stimulation when IR is given at a time point corresponding with high levels of androgen-induced DSB formation. Furthermore, in vivo studies showed a significant improvement in tumor growth delay when radiation was given shortly after androgen repletion in castrated mice.

CONCLUSIONS

These results suggest a potential cooperative effect and improved tumor growth delay with androgen-induced DSBs and radiation with implications for improving the therapeutic index of prostate cancer radiation therapy. Clin Cancer Res; 22(13); 3310-9. ©2016 AACRSee related commentary by Chua and Bristow, p. 3124.

GSTP1 Loss results in accumulation of oxidative DNA base damage and promotes prostate cancer cell survival following exposure to protracted oxidative stress

BACKGROUND

Epigenetic silencing of glutathione S-transferase π (GSTP1) is a hallmark of transformation from normal prostatic epithelium to adenocarcinoma of the prostate. The functional significance of this loss is incompletely understood. The present study explores the effects of restored GSTP1 expression on glutathione levels, accumulation of oxidative DNA damage, and prostate cancer cell survival following oxidative stress induced by protracted, low dose rate ionizing radiation (LDR).

METHODS

GSTP1 protein expression was stably restored in LNCaP prostate cancer cells. The effect of GSTP1 restoration on protracted LDR-induced oxidative DNA damage was measured by GC-MS quantitation of modified bases. Reduced and oxidized glutathione levels were measured in control and GSTP1 expressing populations. Clonogenic survival studies of GSTP1- transfected LNCaP cells after exposure to protracted LDR were performed. Global gene expression profiling and pathway analysis were performed.

RESULTS

GSTP1 expressing cells accumulated less oxidized DNA base damage and exhibited decreased survival compared to control LNCaP-Neo cells following oxidative injury induced by protracted LDR. Restoration of GSTP1 expression resulted in changes in modified glutathione levels that correlated with GSTP1 protein levels in response to protracted LDR-induced oxidative stress. Survival differences were not attributable to depletion of cellular glutathione stores. Gene expression profiling and pathway analysis following GSTP1 restoration suggests this protein plays a key role in regulating prostate cancer cell survival.

CONCLUSIONS

The ubiquitous epigenetic silencing of GSTP1 in prostate cancer results in enhanced survival and accumulation of potentially promutagenic DNA adducts following exposure of cells to protracted oxidative injury suggesting a protective, anti-neoplastic function of GSTP1. The present work provides mechanistic backing to the tumor suppressor function of GSTP1 and its role in prostate carcinogenesis.

Premalignancy in Prostate Cancer: Rethinking What we Know

High-grade prostatic intraepithelial neoplasia (PIN) has been accepted as the main precursor lesion to invasive adenocarcinoma of the prostate, and this is likely to be the case. However, in an unknown number of cases, lesions fulfilling the diagnostic criteria for high-grade PIN may actually represent intra-acinar or intraductal spread of invasive carcinoma. Intriguingly, this possibility would not contradict many of the findings of previous epidemiologic studies linking high-grade PIN to carcinoma or molecular pathologic studies showing similar genomic (e.g., TMPRSS2-ERG gene fusion) as well as epigenomic and molecular phenotypic alterations between high-grade PIN and carcinoma. Also, this possibility would be consistent with previous anatomic studies in prostate specimens linking high-grade PIN and carcinoma in autopsy and other whole prostate specimens. In addition, if some cases meeting morphologic criteria for PIN actually represent intra-acinar spread of invasive carcinoma, this could be an important potential confounder of the interpretation of past clinical trials enrolling patients presumed to be without carcinoma, who are at high risk of invasive carcinoma. Thus, in order to reduce possible bias in future study/trial designs, novel molecular pathology approaches are needed to decipher when an apparent PIN lesion may be intra-acinar/intra-ductal spread of an invasive cancer and when it truly represents a precursor state. Similar approaches are needed for lesions known as intraductal carcinoma to facilitate better classification of them as true intra-ductal/acinar spread on one hand or as precursor high-grade PIN (cribriform type) on the other hand; a number of such molecular approaches (e.g., coevaluating TMPRSS-ERG fusion and PTEN loss) are already showing excellent promise. Cancer Prev Res; 9(8); 648-56. ©2016 AACR.

Global 5-Hydroxymethylcytosine Levels Are Profoundly Reduced in Multiple Genitourinary Malignancies

Solid tumors are characterized by a plethora of epigenetic changes. In particular, patterns methylation of cytosines at the 5-position (5mC) in the context of CpGs are frequently altered in tumors. Recent evidence suggests that 5mC can get converted to 5-hydroxylmethylcytosine (5hmC) in an enzymatic process involving ten eleven translocation (TET) protein family members, and this process appears to be important in facilitating plasticity of cytosine methylation. Here we evaluated the global levels of 5hmC using a validated immunohistochemical staining method in a large series of clear cell renal cell carcinoma (n = 111), urothelial cell carcinoma (n = 55) and testicular germ cell tumors (n = 84) and matched adjacent benign tissues. Whereas tumor-adjacent benign tissues were mostly characterized by high levels of 5hmC, renal cell carcinoma and urothelial cell carcinoma showed dramatically reduced staining for 5hmC. 5hmC levels were low in both primary tumors and metastases of clear cell renal cell carcinoma and showed no association with disease outcomes. In normal testis, robust 5hmC staining was only observed in stroma and Sertoli cells. Seminoma showed greatly reduced 5hmC immunolabeling, whereas differentiated teratoma, embryonal and yolk sack tumors exhibited high 5hmC levels. The substantial tumor specific loss of 5hmC, particularly in clear cell renal cell carcinoma and urothelial cell carcinoma, suggests that alterations in pathways involved in establishing and maintaining 5hmC levels might be very common in cancer and could potentially be exploited for diagnosis and treatment.

Combined MYC Activation and Pten Loss Are Sufficient to Create Genomic Instability and Lethal Metastatic Prostate Cancer

Genetic instability, a hallmark feature of human cancers including prostatic adenocarcinomas, is considered a driver of metastasis. Somatic copy number alterations (CNA) are found in most aggressive primary human prostate cancers, and the overall number of such changes is increased in metastases. Chromosome 10q23 deletions, encompassing PTEN, and amplification of 8q24, harboring MYC, are frequently observed, and the presence of both together portends a high risk of prostate cancer-specific mortality. In extant genetically engineered mouse prostate cancer models (GEMM), isolated MYC overexpression or targeted Pten loss can each produce early prostate adenocarcinomas, but are not sufficient to induce genetic instability or metastases with high penetrance. Although a previous study showed that combining Pten loss with focal MYC overexpression in a small fraction of prostatic epithelial cells exhibits cooperativity in GEMMs, additional targeted Tp53 disruption was required for formation of metastases. We hypothesized that driving combined MYC overexpression and Pten loss using recently characterized Hoxb13 transcriptional control elements that are active in prostate luminal epithelial cells would induce the development of genomic instability and aggressive disease with metastatic potential. Neoplastic lesions that developed with either MYC activation alone (Hoxb13-MYC) or Pten loss alone (Hoxb13-Cre∣Pten(Fl/Fl)) failed to progress beyond prostatic intraepithelial neoplasia and did not harbor genomic CNAs. By contrast, mice with both alterations (Hoxb13-MYC∣Hoxb13-Cre∣Pten(Fl/Fl), hereafter, BMPC mice) developed lethal adenocarcinoma with distant metastases and widespread genome CNAs that were independent of forced disruption of Tp53 and telomere shortening. BMPC cancers lacked neuroendocrine or sarcomatoid differentiation, features uncommon in human disease but common in other models of prostate cancer that metastasize. These data show that combined MYC activation and Pten loss driven by the Hoxb13 regulatory locus synergize to induce genomic instability and aggressive prostate cancer that phenocopies the human disease at the histologic and genomic levels.

Molecular evidence that invasive adenocarcinoma can mimic prostatic intraepithelial neoplasia (PIN) and intraductal carcinoma through retrograde glandular colonization

Prostate cancer often manifests as morphologically distinct tumour foci and is frequently found adjacent to presumed precursor lesions such as high-grade prostatic intraepithelial neoplasia (HGPIN). While there is some evidence to suggest that these lesions can be related and exist on a pathological and morphological continuum, the precise clonal and temporal relationships between precursor lesions and invasive cancers within individual tumours remain undefined. Here, we used molecular genetic, cytogenetic, and histological analyses to delineate clonal, temporal, and spatial relationships between HGPIN and cancer lesions with distinct morphological and molecular features. First, while confirming the previous finding that a substantial fraction of HGPIN lesions associated with ERG-positive cancers share rearrangements and overexpression of ERG, we found that a significant subset of such HGPIN glands exhibit only partial positivity for ERG. This suggests that such ERG-positive HGPIN cells either rapidly invade to form adenocarcinoma or represent cancer cells that have partially invaded the ductal and acinar space in a retrograde manner. To clarify these possibilities, we used ERG expression status and TMPRSS2-ERG genomic breakpoints as markers of clonality, and PTEN deletion status to track temporal evolution of clonally related lesions. We confirmed that morphologically distinct HGPIN and nearby invasive cancer lesions are clonally related. Further, we found that a significant fraction of ERG-positive, PTEN-negative HGPIN and intraductal carcinoma (IDC-P) lesions are most likely clonally derived from adjacent PTEN-negative adenocarcinomas, indicating that such PTEN-negative HGPIN and IDC-P lesions arise from, rather than give rise to, the nearby invasive adenocarcinoma. These data suggest that invasive adenocarcinoma can morphologically mimic HGPIN through retrograde colonization of benign glands with cancer cells. Similar clonal relationships were also seen for intraductal carcinoma adjacent to invasive adenocarcinoma. These findings represent a potentially undervalued indicator of pre-existing invasive prostate cancer and have significant implications for prostate cancer diagnosis and risk stratification.

Androgen-Regulated SPARCL1 in the Tumor Microenvironment Inhibits Metastatic Progression

Prostate cancer is a leading cause of cancer death in men due to the subset of cancers that progress to metastasis. Prostate cancers are thought to be hardwired to androgen receptor (AR) signaling, but AR-regulated changes in the prostate that facilitate metastasis remain poorly understood. We previously noted a marked reduction in secreted protein, acidic and rich in cysteine-like 1 (SPARCL1) expression during invasive phases of androgen-induced prostate growth, suggesting that this may be a novel invasive program governed by AR. Herein, we show that SPARCL1 loss occurs concurrently with AR amplification or overexpression in patient-based data. Mechanistically, we demonstrate that SPARCL1 expression is directly suppressed by androgen-induced AR activation and binding at the SPARCL1 locus via an epigenetic mechanism, and these events can be pharmacologically attenuated with either AR antagonists or HDAC inhibitors. We establish using the Hi-Myc model of prostate cancer that in Hi-Myc/Sparcl1(-/-) mice, SPARCL1 functions to suppress cancer formation. Moreover, metastatic progression of Myc-CaP orthotopic allografts is restricted by SPARCL1 in the tumor microenvironment. Specifically, we show that SPARCL1 both tethers to collagen in the extracellular matrix (ECM) and binds to the cell's cytoskeleton. SPARCL1 directly inhibits the assembly of focal adhesions, thereby constraining the transmission of cell traction forces. Our findings establish a new insight into AR-regulated prostate epithelial movement and provide a novel framework whereby SPARCL1 in the ECM microenvironment restricts tumor progression by regulating the initiation of the network of physical forces that may be required for metastatic invasion of prostate cancer.

Abstract 5021: Histopathologic and gene expression analysis in mouse models of long-term chronic prostatic inflammation using human prostate cancer-derived bacterial isolates

Prostate cancer is the second leading cause of cancer death in the U.S. and afflicts 1 in 6 men in their lifetime. Evidence suggests that inflammation contributes to cancer development by causing cellular and genome damage and contributing to a tumor microenvironment that promotes cellular replication and angiogenesis. In addition, infectious agents are known to be the driving force in many inflammation-associated cancers. For example, in adenocarcinomas of the distal stomach, long-term inflammation caused by Helicobacter pylori infection is frequently observed and implicated as a causative factor. Despite the independent observations of both inflammation and microorganisms in the prostates of cancer patients, to date, virtually no study has definitively demonstrated a causal role for microorganisms in the chronic inflammation observed in prostatectomy specimens. Furthermore, no study has localized these organisms to the inflammation-associated lesions that are the predicted precursor lesions to prostate cancer development. We hypothesize that pathogenic microorganisms play a role in the development of chronic inflammation in the prostate that in turn serves to initiate and/or promote prostate cancer development. In addition, we hypothesize that key molecular changes associated with disease progression are due to the presence of acute and/or chronic inflammation. We aim to study this hypothesis in novel animal models of long-term prostatic infection and inflammation using bacterial isolates from human prostate cancer tissues. To date, we have isolated over 30 strains of bacteria from human radical prostatectomy specimens, and 15 strains were chosen for infection studies in mice. This includes species of bacteria such as Corynebacterium, Neisseria, Propionibacterium, and Staphylococcus. Our results show that the induction of long-term chronic inflammation in the mouse prostate may be bacterial strain dependent. Furthermore, we have noted lesions consistent with prostatic remodeling in animals that have undergone bacteria-induced long-term prostatic inflammation. Finally, Illumina gene expression array analysis of dorsal prostate from mice inoculated with either PBS or P. acnes was used to identify genes differentially expressed in the presence of both acute and chronic inflammation. Early studies identify upregulated genes, including lactoferrin, that are known to be upregulated in both immune cells and in the epithelium in inflamed human prostate. Our ongoing studies evaluate gene expression changes associated with persistent inflammation present up to 6 months post-infection in these mouse models. The goal of these studies is to determine both short- and long-term gene expression profiles associated with bacteria-induced prostatic inflammation and to correlate molecular changes with phenotypic changes in the inflamed mouse prostate.

Citation Format: Gretchen K. Hubbard, Shu-Han Yu, Debika Biswal Shinohara, Ajay Vaghasia, William G. Nelson, Srinivasan Yegnasubramanian, Angelo M. De Marzo, Karen S. Sfanos. Histopathologic and gene expression analysis in mouse models of long-term chronic prostatic inflammation using human prostate cancer-derived bacterial isolates. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5021. doi:10.1158/1538-7445.AM2015-5021

Regulatory T cell DNA methyltransferase inhibition accelerates resolution of lung inflammation

Acute respiratory distress syndrome (ARDS) is a common and often fatal inflammatory lung condition without effective targeted therapies. Regulatory T cells (Tregs) resolve lung inflammation, but mechanisms that enhance Tregs to promote resolution of established damage remain unknown. DNA demethylation at the forkhead box protein 3 (Foxp3) locus and other key Treg loci typify the Treg lineage. To test how dynamic DNA demethylation affects lung injury resolution, we administered the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (DAC) to wild-type (WT) mice beginning 24 hours after intratracheal LPS-induced lung injury. Mice that received DAC exhibited accelerated resolution of their injury. Lung CD4(+)CD25(hi)Foxp3(+) Tregs from DAC-treated WT mice increased in number and displayed enhanced Foxp3 expression, activation state, suppressive phenotype, and proliferative capacity. Lymphocyte-deficient recombinase activating gene-1-null mice and Treg-depleted (diphtheria toxin-treated Foxp3(DTR)) mice did not resolve their injury in response to DAC. Adoptive transfer of 2 × 10(5) DAC-treated, but not vehicle-treated, exogenous Tregs rescued Treg-deficient mice from ongoing lung inflammation. In addition, in WT mice with influenza-induced lung inflammation, DAC rescue treatment facilitated recovery of their injury and promoted an increase in lung Treg number. Thus, DNA methyltransferase inhibition, at least in part, augments Treg number and function to accelerate repair of experimental lung injury. Epigenetic pathways represent novel manipulable targets for the treatment of ARDS.

Should Gleason 6 be labeled as cancer?

PUPOSE OF REVIEW

The review covers arguments for and against removing the label of 'cancer' in Gleason score 6 prostate tumors.

RECENT FINDINGS

While there are a number of factors that determine whether men elect active surveillance, the most powerful predictor remains the Gleason score. Gleason grading remains a robust and powerful predictor of outcome in patients with prostate cancer. A pure Gleason score 6 (GS6) tumor is exceedingly unlikely to cause harm in the near term, and there have been discussions regarding whether the term cancer should still be applied. In this review, we update the largely clinico-pathological arguments that have led to the suggestion to remove the cancer label from GS6 tumors, and we provide counter arguments on the basis of practical matters of needle biopsy sampling, classical histopathology, and molecular biology findings.

SUMMARY

The implications are that by retaining the label of cancer and implementing the recently proposed concept of prognostic groups, with patients harboring GS6 tumors placed into the lowest category, there is still a strong rationale in support of the choice of active surveillance or watchful waiting for most patients with GS6 lesions.