Characterization of HOXB13 expression patterns in localized and metastatic castration-resistant prostate cancer.

HOXB13 is a key lineage homeobox transcription factor that plays a critical role in the differentiation of the prostate gland. Several studies have suggested that HOXB13 alterations may be involved in prostate cancer development and progression. Despite its potential biological relevance, little is known about the expression of HOXB13 across the disease spectrum of prostate cancer. To this end, we validated a HOXB13 antibody using genetic controls and investigated HOXB13 protein expression in murine and human developing prostates, localized prostate cancers, and metastatic castration-resistant prostate cancers. We observed that HOXB13 expression increases during later stages of murine prostate development. All localized prostate cancers showed HOXB13 protein expression. Interestingly, lower HOXB13 expression levels were observed in higher-grade tumors, although no significant association between HOXB13 expression and recurrence or disease-specific survival was found. In advanced metastatic prostate cancers, HOXB13 expression was retained in the majority of tumors. While we observed lower levels of HOXB13 protein and mRNA levels in tumors with evidence of lineage plasticity, 84% of androgen receptor-negative castration-resistant prostate cancers and neuroendocrine prostate cancers (NEPCs) retained detectable levels of HOXB13. Notably, the reduced expression observed in NEPCs was associated with a gain of HOXB13 gene body CpG methylation. In comparison to the commonly used prostate lineage marker NKX3.1, HOXB13 showed greater sensitivity in detecting advanced metastatic prostate cancers. Additionally, in a cohort of 837 patients, 383 with prostatic and 454 with non-prostatic tumors, we found that HOXB13 immunohistochemistry had a 97% sensitivity and 99% specificity for prostatic origin. Taken together, our studies provide valuable insight into the expression pattern of HOXB13 during prostate development and cancer progression. Furthermore, our findings support the utility of HOXB13 as a diagnostic biomarker for prostate cancer, particularly to confirm the prostatic origin of advanced metastatic castration-resistant tumors. © 2023 The Pathological Society of Great Britain and Ireland.

Outcomes of 10 years of PSA screening for prostate cancer in Norwegian men with Lynch syndrome.

BACKGROUND: Pathogenic germline variants in the mismatch repair (MMR) genes are associated with an increased risk of prostate cancer (PCa). Since 2010 we have recommended MMR carriers annual PSA testing from the age of 40. Prospective studies of the outcome of long-term PSA screening are lacking. This study aimed to investigate the incidence and characteristics of PCa in Norwegian MMR carriers attending annual PSA screening (PSA threshold >3.0 ng/mL) to evaluate whether our recommendations should be continued. METHODS: This is a prospective observational study of 225 male MMR carriers who were recommended annual PSA screening by the Section of Inherited Cancer, Oslo University Hospital from 2010 and onwards. Incidence and tumor characteristics (age, PSA at diagnosis, Gleason score, TNM score) were described. IHC and MSI-analyses were done on available tumors. Standardized incidence ratio (SIR) was calculated based on data from the Cancer Registry of Norway. RESULTS: Twenty-two of 225 (9.8%) had been diagnosed with PCa, including 10/69 (14.5%) MSH2 carriers and 8/61 (13.1%) MSH6 carriers. Ten of 20 (50%) tumors had Gleason score ≥4 + 3 on biopsy and 6/11 (54.5%) had a pathological T3a/b stage. Eight of 17 (47.1%) tumors showed abnormal staining on IHC and 3/13 (23.1%) were MSI-high. SIR was 9.54 (95% CI 5.98-14.45) for all MMR genes, 13.0 (95% CI 6.23-23.9) for MSH2 and 13.74 for MSH6 (95% CI 5.93-27.08). CONCLUSIONS: Our results indicate that the MMR genes, and especially MSH2 and MSH6, are associated with a significant risk of PCa, and a high number of tumors show aggressive characteristics. While the impact of screening on patient outcomes remains to be more firmly established, the high SIR values we observe provide support for continued PSA screening of MSH2 and MSH6 carriers. Studies are needed to provide optimal recommendations for PSA-threshold and to evaluate whether MLH1 and PMS2 carriers should not be recommended screening.

Association of rare, recurrent nonsynonymous variants in the germline of prostate cancer patients of African ancestry.

BACKGROUND: Although men of African ancestry (AA) have the highest mortality rate from prostate cancer (PCa), relatively little is known about the germline variants that are associated with PCa risk in AA men. The goal of this study is to systematically evaluate rare, recurrent nonsynonymous variants across the exome for their association with PCa in AA men. METHODS: Whole exome sequencing (WES) of germline DNA in two AA PCa patient cohorts of Johns Hopkins Hospital (N = 960) and Wayne State University (N = 747) was performed. All nonsynonymous variants present in both case cohorts, with a carrier rate between 0.5% and 1%, were identified. Their carrier rates were compared with rates from 8128 African/African American (AFR) control subjects from The Genome Aggregation Database (gnomAD) using Fisher's exact test. Significant variants, defined as false discovery rate (FDR) adjusted p-value ≤ 0.05, were further evaluated in AA PCa cases (N = 132) and controls (N = 1184) from the UK Biobank (UKB). RESULTS: Two variants reached a pre-specified statistical significance level. The first was p.R14Q in GPRC5C (found in 0.47% of PCa cases and 0.01% of population controls); odds ratio (OR) for PCa was 37.46 (95% confidence interval CI 4.68-299.72), pexact = 7.01E-06, FDR-adjusted p-value = 0.05. The second was p.R511Q in IGF1R (found in 0.53% of PCa cases and 0.01% of population controls); OR for PCa was 21.54 (95%CI 4.65-99.76), pexact = 5.51E-06, FDR-adjusted p-value = 0.05. The mean percentage of African ancestry was similar between variant carriers and noncarriers of each variant, p > 0.05. In the UKB AA men, GPRC5C R14Q was 0.76% and 0.08% in cases and controls, respectively, OR for PCa was 9.00 (95%CI 0.56-145.23), pexact = 0.19. However, IGF1R R511Q was not found in cases or controls. CONCLUSIONS: This WES study identified two rare, recurrent nonsynonymous PCa risk-associated variants in AA. Confirmation in additional large populations of AA PCa cases and controls is required.

Association of germline rare pathogenic mutations in guideline-recommended genes with prostate cancer progression: A meta-analysis.

BACKGROUND: Germline mutations in several genes, mainly DNA repair genes, have been associated with prostate cancer (PCa) progression. However, primarily due to the rarity of mutations, statistical evidence for these associations is not consistently established. The objective of this study is to synthesize evidence from multiple studies using a meta-analysis. METHODS: Genes analyzed were chosen based on National Comprehensive Cancer Network guidelines recommendations (10 genes) and a commonly reported gene (NBN). PCa progression in this analysis was defined as either having metastases or PCa-specific mortality. We searched PubMed for papers published before April 26, 2021, using selected keywords. Pooled odds ratio (OR) was estimated in all races and Caucasians-only using both fixed- and random-effect models. RESULTS: The search identified 1028 papers and an additional five from a manual review of references. After a manual process that excluded noneligible studies, 11 papers remained, including a total of 3944 progressors and 20,054 nonprogressors. Combining results from these eligible studies, mutation carrier rates were significantly higher in progressors than nonprogressors for NBN, BRCA2, ATM (under both fixed- and random-effect models), for CHEK2 (under fixed-effect model only), and for PALB2 (under random-effect model only), p < 0.05. Pooled OR (95% confidence interval) was 6.38 (2.25-18.05), 3.41 (2.31; 5.03), 1.93 (1.17-3.20), and 1.53 (1.00-2.33) for NBN, BRCA2, ATM, and CHEK2, respectively, under fixed-effect model and 2.63 (1.12-6.13) for PALB2 under random-effect model. No significant association was found for the six remaining genes. Certainty of evidence was low for many genes due primarily to the limited number of eligible studies and mutation carriers. CONCLUSIONS: Statistical evidence for five genes was obtained in this first meta-analysis of germline mutations and PCa progression. While these results may help urologists and genetic counselors interpret germline testing results for PCa progression, more original studies are needed.

The HOXB13 variant X285K is associated with clinical significance and early age at diagnosis in African American prostate cancer patients.

BACKGROUND: Recently, a novel HOXB13 variant (X285K) was observed in men of African descent with prostate cancer (PCa) in Martinique. Little is known about this or other variants in HOXB13 which may play a role in PCa susceptibility in African-American (AA) men. METHODS: We sequenced HOXB13 in an AA population of 1048 men undergoing surgical treatment for PCa at Johns Hopkins Hospital. RESULTS: Seven non-synonymous germline variants were observed in the patient population. While six of these variants were seen only once, X285K was found in eight patients. In a case-case analysis, we find that carriers of this latter variant are at increased risk of clinically significant PCa (1.2% carrier rate in Gleason Score ≥7 PCa vs. 0% in Gleason Score <7 PCa, odds ratio, OR = inf; 95% Confidence Interval, 95%CI:1.05-inf, P = 0.028), as well as PCa with early age at diagnosis (2.4% carrier rate in patients <50 year vs. 0.5% carrier rate in patients ≥50 year, OR = 5.25, 95% CI:1.00-28.52, P = 0.03). CONCLUSIONS: While this variant is rare in the AA population (~0.2% MAF), its ancestry-specific occurrence and apparent preferential association with risk for the more aggressive disease at an early age emphasizes its translational potential as an important, novel PCa susceptibility marker in the high-risk AA population.

Association between pathogenic germline mutations in BRCA2 and ATM and tumor-infiltrating lymphocytes in primary prostate cancer.

Pathogenic mutations in homologous recombination (HR) DNA repair genes may be associated with increased tumor mutational burden and numbers of tumor-infiltrating lymphocytes (TIL). Though HR-deficient prostate tumors have been anecdotally associated with improved responses to immunotherapy, it is unclear whether HR mutations or HR deficiency (HRD) scores predict for increased T-cell densities in this cancer. We evaluated 17 primary prostate tumors from patients with pathogenic germline BRCA2 mutations (gBRCA2) and 21 primary prostate tumors from patients with pathogenic germline ATM (gATM) mutations, which were compared to 19 control tumors lacking HR gene mutations, as well as the TCGA prostate cancer cohort. HRD score was estimated by targeted sequencing (gBRCA2 and gATM) or by SNP microarray (TCGA). Tumor-associated T-cell densities were assessed using validated automated digital image analysis of CD8 and FOXP3 immunostaining (gBRCA2 or gATM) or by methylCIBERSORT (TCGA). CD8 + and FOXP3 + T-cell densities were significantly correlated with each other in gBRCA2 and gATM cases. There was no significant difference between CD8 + or FOXP3 + TIL densities in gBRCA2 or gATM cases compared to controls. In the TCGA cohort, HRD score was associated with predicted CD8 + and FOXP3 + TILs. Associations were also seen for HRD score and TIL density among the germline-mutated cases. In contrast to mismatch repair-deficient primary prostate tumors, cancers from germline BRCA2 or ATM mutation carriers do not appear to be associated with elevated TIL density. However, measures of genomic scarring, such as HRD score, may be associated with increased tumor-infiltrating T-cells.

The role of genetic testing in prostate cancer screening, diagnosis, and treatment.

PURPOSE OF REVIEW: This review provides an overview of the current role of genetic testing in prostate cancer screening, diagnosis, and treatment. RECENT FINDINGS: Recent studies have uncovered few but highly penetrant rare pathogenic mutations (RPMs), in genes, such as BRCA2, with strong prostate cancer risk and outcomes associations. Over 260 single nucleotide polymorphisms (SNPs) have also been identified, each associated with small incremental prostate cancer risk and when combined in a polygenic risk score (PRS), they provide strong prostate cancer risk prediction but do not seem to predict outcomes. Tumor tissue sequencing can also help identify actionable somatic mutations in many patients with advanced prostate cancer and inform on their risk of harboring a germline pathogenic mutation. SUMMARY: RPM testing, PRS testing, and tumor sequencing all have current and/or potential future roles in personalized prostate cancer care.

Observed evidence for guideline-recommended genes in predicting prostate cancer risk from a large population-based cohort.

BACKGROUND: Germline testing for prostate cancer (PCa) is now recommended by the National Comprehensive Cancer Network. While multi-gene testing has been proposed, evidence for their association with PCa risk is not well established. METHODS: We tested associations of pathogenic/likely pathogenic mutations in 10 guideline-recommended genes (ATM, BRCA1, BRCA2, CHEK2, PALB2, MLH1, MSH2, MSH6, PMS2, and HOXB13) with PCa risk in the UK Biobank, a population-based cohort. Mutations were annotated based on prostate-specific transcripts using the American College of Medical Genetics and Genomics standards. Associations were tested in 4399 PCa cases and 85,403 unaffected male controls using logistic regression adjusting for age and genetic background. p < .005 was considered significant based on Bonferroni correction. RESULTS: Among the 10 tested genes, significantly higher mutation carrier rates in PCa cases versus controls were found for four genes at p < .005; HOXB13, BRCA2, ATM, and CHEK2, with odds ratios (95% confidence interval) estimated at 4.96 (3.62-6.69), 3.23 (2.23-4.56), 2.95 (2.01-4.22), 1.94 (1.43-2.58), respectively. No significant association was found between mutation carrier status and age at PCa diagnosis or family history of PCa. Despite the large sample size of this study, statistical power remains limited, especially for genes where pathogenic mutation carrier rates are extremely rare (<0.03%). CONCLUSION: Observed evidence for PCa risk was found for four of the 10 guideline-recommended genes in this large population-based study. Mutations in these four genes can be interpreted with confidence in genetic counseling for PCa risk assessment. Evidence for the remaining six genes needs to be further evaluated in larger studies.

Association of prostate cancer polygenic risk score with number and laterality of tumor cores in active surveillance patients.

BACKGROUND: Prostate cancer (PCa) is characterized by its tendency to be multifocal. However, few studies have investigated the endogenous factors that explain the multifocal disease. The primary objective of the current study is to test whether inherited PCa risk is associated with multifocal tumors in PCa patients. METHODS: Subjects in this study were PCa patients of European ancestry undergoing active surveillance at Johns Hopkins Hospital (N = 805) and NorthShore University HealthSystem (N = 432). The inherited risk was measured by genetic risk score (GRS), an odds ratio-weighted and population-standardized polygenic risk score based on known risk-associated single nucleotide polymorphisms. PCa multifocality was indirectly measured by the number and laterality of positive tumor cores from a 12-core systematic biopsy. RESULTS: In the combined cohort, 35.7% and 66.3% of patients had ≥2 tumor cores at the initial diagnostic biopsy and on at least one subsequent surveillance biopsy, respectively. For tumor laterality, 7.8% and 47.8% of patients had bilateral tumor cores at diagnostic and surveillance biopsies, respectively. We found, for the first time, that patients with higher numbers of positive cores at diagnostic and surveillance biopsies, respectively, had significantly higher mean GRS values; p = .01 and p = 5.94E-04. Additionally, patients with bilateral tumors at diagnostic and surveillance biopsies, respectively, had significantly higher mean GRS values than those with unilateral tumors; p = .04 and p = .01. In contrast, no association was found between GRS and maximum core length of tumor or tumor grade at diagnostic/surveillance biopsies (all p > .05). Finally, we observed a modest trend that patients with higher GRS quartiles had a higher risk for tumor upgrading on surveillance biopsies. The trend, however, was not statistically significant (p > .05). CONCLUSIONS: The associations of GRS with two measurements of PCa multifocality (core numbers and laterality) provide novel and consistent evidence for the link between inherited PCa risk and multifocal tumors.

Homologous recombination deficiency (HRD) score in germline BRCA2- versus ATM-altered prostate cancer.

The homologous recombination deficiency (HRD) score integrates three DNA-based measures of genomic instability, and has been understudied in prostate cancer. Given the recent FDA approval of two PARP inhibitors for prostate cancer, HRD score analysis could help to refine treatment selection. We assessed HRD score (defined as the sum of loss-of-heterozygosity, telomeric allelic imbalance, and large-scale state transitions) in three cohorts of primary prostate cancer, including a Johns Hopkins University (JHU) cohort with germline mutations in BRCA2, ATM, or CHEK2 (n = 64), the TCGA cohort (n = 391), and the PROGENE cohort (n = 102). In the JHU cohort, tumors with germline BRCA2 mutations had higher HRD scores (median = 27) than those with germline ATM or CHEK2 mutations (median = 16.5 [p = 0.029] and 9 [p < 0.001], respectively). For TCGA tumors without underlying HR pathway mutations, the median HRD score was 11, significantly lower than ovarian carcinoma lacking BRCA1/2 mutations (median = 28). In the absence of HR gene mutations, the median HRD score was unexpectedly higher among prostate cancers with TP53 mutations versus those without (17 vs. 11; p = 0.015); this finding was confirmed in the PROGENE cohort (24 vs. 16; p = 0.001). Finally, among eight BRCA2-altered patients who received olaparib, progression-free survival trended longer in those with HRD scores above versus below the median (14.9 vs. 9.9 months). We conclude that HRD scores are low in primary prostate cancer and higher in cases with germline BRCA2 or somatic TP53 mutations. Germline BRCA2-altered cases have significantly higher HRD scores than germline ATM-altered or CHEK2-altered cases, consistent with the lower efficacy of PARP inhibitors among the latter.

Specific Detection of Prostate Cancer Cells in Urine by RNA In Situ Hybridization.

PURPOSE: Noninvasive tests that can accurately detect prostate cancer are urgently needed for prostate cancer diagnosis, surveillance and prognosis. Exfoliated prostate cells captured in urine represent a promising resource for noninvasive detection of prostate cancer. We investigated performance of a novel cell-based urine test for detection of clinically significant prostate cancer. MATERIALS AND METHODS: We previously developed a multiplex RNA in situ hybridization assay targeting NKX3-1, PRAC1 and PCA3 that enables identification and quantification of malignant and benign prostate cells released into urine. We investigated application of the assay for prostate cancer detection in a cohort of 98 patients suspected of harboring prostate cancer. Urine was collected following digital rectal examination, and the sediment was isolated and evaluated by RNA in situ hybridization. Samples were scored based on cellular expression of RNA in situ hybridization targets. Cells of prostate origin were defined by positivity for NKX3-1 and/or PRAC1, and prostate cancer cells by positivity for PCA3. RESULTS: Prostate cells (NKX3-1/PRAC1+ cells) were detected in 69 samples, among which 20 were positive for PCA3 (ie positive for prostate cancer cells). Comparison of RNA in situ hybridization results with biopsy outcome and clinical variables revealed that positivity for cancer by RNA in situ hybridization significantly correlated with intermediate/high risk cancer (p=0.003), PSA density (p=0.022), significant disease (p <0.0001) and Gleason score (p=0.003). The test was 95% specific and 51% sensitive for detection of clinically significant prostate cancer. CONCLUSIONS: Identification of exfoliated prostate cancer cells in urine by RNA in situ hybridization provides a novel tool for highly specific and noninvasive detection of prostate cancer.

Germline BLM mutations and metastatic prostate cancer.

BACKGROUND: Biallelic loss-of-function BLM mutations result in Bloom syndrome: a genetic disorder characterized by growth deficiencies, photosensitivity, and multiple cancer susceptibilities. There are conflicting reports about whether or not heterozygous BLM carriers are at a higher risk of various cancers. Without BLM protein functionality, there is evidence of increased sister chromatid exchange and chromosomal instability. METHODS: Metastatic prostate cancer patients (N = 796) underwent germline genetic testing as part of routine care at three academic centers. Patients with heterozygous BLM mutations were identified. Tumor tissue was analyzed for somatic alterations in those patients who had a germline pathogenic mutation. Control data using a population sample were extracted from the Genome Aggregation Database. RESULTS: Heterozygous BLM germline mutations in 5 of 796 patients (prevalence, 0.63%). All mutations were loss-of-function truncating alterations. None of the mutations were BLMAsh . The control population (gnomAD) frequency of pathogenic or likely pathogenic BLM mutations was 0.18% (212 of 116 653). The relative risk (RR) of BLM mutations in metastatic prostate cancer patients was 3.4 (95% CI, 1.42-8.33; P < .0062) compared to gnomAD controls. Tumor DNA sequencing in the BLM carriers showed no evidence of somatic BLM mutations. Interestingly, 3 of 5 BLM germline carriers had bi-allelic BRCA2 inactivation evident on tumor sequencing. One patient had both germline and somatic mutations in BRCA2. Excluding the patient with the germline BRCA2 mutation (BLM prevalence, 4 of 796: 0.50%) still yielded a statistically significant finding vs the gnomAD controls (RR, 2.8; 95% CI, 1.02-7.39; P < .04). CONCLUSION: Truncating BLM germline mutations occur at a higher frequency in patients with advanced prostate cancer as compared to control populations. Though no biallelic loss of BLM was no noted in cancers, a surprising number of the BLM germline heterozygotes had pathogenic BRCA2 mutations in their tumor.

Feasibility and performance of a novel probe panel to detect somatic DNA copy number alterations in clinical specimens for predicting prostate cancer progression.

BACKGROUND: To assess the feasibility of a novel DNA-based probe panel to detect copy number alterations (CNAs) in prostate tumor DNA and its performance for predicting clinical progression. METHODS: A probe panel was developed and optimized to measure CNAs in trace amounts of tumor DNA (2 ng) isolated from formalin-fixed paraffin-embedded tissues. Ten genes previously associated with aggressive disease were targeted. The panel's feasibility and performance were assessed in 175 prostate cancer (PCa) patients who underwent radical prostatectomy with a median 10-year follow-up, including 42 men who developed disease progression (either metastasis and/or PCa-specific death). Association with disease progression was tested using univariable and multivariable analyses. RESULTS: The probe panel detected CNAs in all 10 genes in tumor DNA isolated from either diagnostic biopsies or surgical specimens. A four-gene model (PTEN/MYC/BRCA2/CDKN1B) had the strongest association with disease progression; 64.3% of progressors and 22.5% of non-progressors had at least one CNA in these four genes, odds ratio (OR) (95% confidence interval) = 6.21 (2.77-13.87), P = 8.48E-06. The association with disease progression remained significant after adjusting for known clinicopathological variables. Among the seven progressors of the 65 patients with clinically low-risk disease, three (42.9%) had at least one CNA in these four genes. CONCLUSIONS: The probe panel can detect CNAs in trace amounts of tumor DNA from biopsies or surgical tissues at the time of diagnosis or surgery. CNAs independently predict metastatic/lethal cancer, particularly among men with clinically low-risk disease at diagnosis. If validated, this may improve current abilities to assess tumor aggressiveness.

Germline HOXB13 G84E mutation carriers and risk to twenty common types of cancer: results from the UK Biobank.

Germline HOXB13 G84E mutation has been consistently associated with prostate cancer (PCa) risk, but its association with other cancers is controversial. We systematically tested its association with the 20 most common cancer types in subjects from the UK Biobank. The G84E mutation was found in 1,545 (0.34%) of 460,224 participants of European ancestry. While mutation status did not associate with cancer risk in females, it was significantly associated with increased risk in males; odds ratio (OR) (95% confidence interval) for overall cancer diagnosis was 2.19 (1.89-2.52), P = 2.5E-19. The association remained after excluding PCa; OR = 1.4 (1.16-1.68), P = 0.003, suggesting association with other cancers. Indeed, suggestive novel associations were found for two other cancer types; rectosigmoid cancer, OR = 2.25 (1.05-4.15), P = 0.05 and non-melanoma skin cancer (NMSC), OR = 1.40 (1.12-1.74), P = 0.01. For NMSC, the association was found only in basal cell carcinoma, OR = 1.37 (1.07-1.74), P = 0.03. These findings have potential clinical utility for genetic counselling regarding HOXB13.

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.

HOXB13 interaction with MEIS1 modifies proliferation and gene expression in prostate cancer.

BACKGROUND: The recurrent p.Gly84Glu germline mutation (G84E) in HOXB13 is consistently associated with prostate cancer (PCa), although the mechanisms underlying such linkage remain elusive. The majority of the PCa-associated HOXB13 mutations identified are localized to two conserved domains in HOXB13 that have been shown to mediate the interaction with MEIS cofactors belonging to the TALE family of homeodomain transcription factors. In this study, we sought to interrogate the biochemical and functional interactions between HOXB13 and MEIS in prostatic cells with a goal of defining how the HOXB13-MEIS complex impacts PCa pathobiology and define the extent to which the oncogenic activity of G84E is related to its effect on HOXB13-MEIS interaction/function. METHODS: HOXB13 and MEIS paralog expression in prostate epithelial cells and PCa cell lines was characterized by qPCR and immunoblot analyses. HOXB13 and MEIS1 co-expression in human prostate tissue was confirmed by IHC, followed by co-IP mapping of HOXB13-MEIS1 interactions. Proliferation of the PCa cell line LAPC4 following shRNA-mediated knockdown of each gene or both genes was assessed using DNA- and metabolic-based assays. Transcriptional targets of HOXB13 and MEIS1 were identified by gene expression profiling and qPCR. Finally, protein stability of HOXB13 in the context of MEIS1 was determined using pulse-chase assays. RESULTS: HOXB13 and MEIS1 are co-expressed and interact in prostate cells. Both of the putative MEIS interacting domains (MID) within HOXB13 were shown to be capable of mediating the interaction between HOXB13 and MEIS1 independently and such interactions were not influenced by the G84E mutation. The inhibitory effect of either HOXB13 or MEIS1 knockdown on cellular proliferation was augmented by knockdown of both genes, and MEIS1 knockdown abolished HOXB13-driven regulation of BCHE and TNFSF10 mRNA expression. Notably, we demonstrated that MEIS1 stabilized the HOXB13 protein in LAPC4 cells. CONCLUSIONS: Our study provides evidence for functional HOXB13-MEIS1 interactions in PCa. MEIS1 may contribute to the cancer-promoting actions of HOXB13 in cellular proliferation and gene regulation by prolonging HOXB13 half-life. Our data demonstrates that G84E is not a loss-of-function mutation that interferes with HOXB13 stability or ability to interact with MEIS1.

Concept and benchmarks for assessing narrow-sense validity of genetic risk score values.

BACKGROUND: While higher genetic risk score (GRS) has been statistically associated with increased disease risk (broad-sense validity), the concept and tools for assessing the validity of reported GRS values from tests (narrow-sense validity) are underdeveloped. METHODS: We propose two benchmarks for assessing the narrow-sense validity of GRS. The baseline benchmark requires that the mean GRS value in a general population approximates 1.0. The calibration benchmark assesses the agreement between observed risks and estimated risks (GRS values). We assessed benchmark performance for three prostate cancer (PCa) GRS tests, derived from three SNP panels with increasing stringency of selection criteria, in a PCa chemoprevention trial where 714 of 3225 men were diagnosed with PCa during the 4-year follow-up. RESULTS: GRS from Panels 1, 2, and 3 were all statistically associated with PCa risk; P = 5.58 × 10-3 , P = 1 × 10-3 , and P = 1.5 × 10-13 , respectively (broad-sense validity). For narrow-sense validity, the mean GRS value among men without PCa was 1.33, 1.09, and 0.98 for Panels 1, 2, and 3, respectively (baseline benchmark). For assessing the calibration benchmark, observed risks were calculated for seven groups of men with GRS values <0.3, 0.3-0.79, 0.8-1.19, 1.2-1.49, 1.5-1.99, 2-2.99, and ≥3. The calibration slope (higher is better) was 0.15, 0.12, and 0.60, and the bias score (lower is better) between the observed risks and GRS values was 0.08, 0.08, and 0.02 for Panels 1, 2, and 3, respectively. CONCLUSION: Performance differed considerably among GRS tests. We recommend that all GRS tests be evaluated using the two benchmarks before clinical implementation for individual risk assessment.

Trichomonas vaginalis infection and prostate-specific antigen concentration: Insights into prostate involvement and prostate disease risk.

BACKGROUND: The protist Trichomonas vaginalis causes a common, sexually transmitted infection and has been proposed to contribute to the development of chronic prostate conditions, including benign prostatic hyperplasia and prostate cancer. However, few studies have investigated the extent to which it involves the prostate in the current antimicrobial era. We addressed this question by investigating the relation between T. vaginalis antibody serostatus and serum prostate-specific antigen (PSA) concentration, a marker of prostate infection, inflammation, and/or cell damage, in young, male, US military members. METHODS: We measured T. vaginalis serum IgG antibodies and serum total PSA concentration in a random sample of 732 young, male US active duty military members. Associations between T. vaginalis serostatus and PSA were investigated by linear regression. RESULTS: Of the 732 participants, 341 (46.6%) had a low T. vaginalis seropositive score and 198 (27.0%) had a high score, with the remainder seronegative. No significant differences were observed in the distribution of PSA by T. vaginalis serostatus. However, slightly greater, nonsignificant differences were observed when men with high T. vaginalis seropositive scores were compared with seronegative men, and when higher PSA concentrations were examined (≥0.70 ng/mL). Specifically, 42.5% of men with high seropositive scores had a PSA concentration greater than or equal to 0.70 ng/mL compared with 33.2% of seronegative men (adjusted P = .125). CONCLUSIONS: Overall, our findings do not provide strong support for prostate involvement during T. vaginalis infection, although our suggestive positive findings for higher PSA concentrations do not rule out this possibility entirely. These suggestive findings may be relevant for prostate condition development because higher early- to mid-life PSA concentrations have been found to predict greater prostate cancer risk later in life.

REVEL: An Ensemble Method for Predicting the Pathogenicity of Rare Missense Variants.

The vast majority of coding variants are rare, and assessment of the contribution of rare variants to complex traits is hampered by low statistical power and limited functional data. Improved methods for predicting the pathogenicity of rare coding variants are needed to facilitate the discovery of disease variants from exome sequencing studies. We developed REVEL (rare exome variant ensemble learner), an ensemble method for predicting the pathogenicity of missense variants on the basis of individual tools: MutPred, FATHMM, VEST, PolyPhen, SIFT, PROVEAN, MutationAssessor, MutationTaster, LRT, GERP, SiPhy, phyloP, and phastCons. REVEL was trained with recently discovered pathogenic and rare neutral missense variants, excluding those previously used to train its constituent tools. When applied to two independent test sets, REVEL had the best overall performance (p < 10-12) as compared to any individual tool and seven ensemble methods: MetaSVM, MetaLR, KGGSeq, Condel, CADD, DANN, and Eigen. Importantly, REVEL also had the best performance for distinguishing pathogenic from rare neutral variants with allele frequencies <0.5%. The area under the receiver operating characteristic curve (AUC) for REVEL was 0.046-0.182 higher in an independent test set of 935 recent SwissVar disease variants and 123,935 putatively neutral exome sequencing variants and 0.027-0.143 higher in an independent test set of 1,953 pathogenic and 2,406 benign variants recently reported in ClinVar than the AUCs for other ensemble methods. We provide pre-computed REVEL scores for all possible human missense variants to facilitate the identification of pathogenic variants in the sea of rare variants discovered as sequencing studies expand in scale.

Updated insights into genetic contribution to prostate cancer predisposition: focus on HOXB13.

This presentation for the Philadelphia Prostate Cancer Consensus 2019 will focus on recent findings regarding the role of HOXB13 as a prostate cancer susceptibility gene. Factors affecting the frequency of HOXB13 mutations in different prostate cancer populations will be reviewed. A number of these factors are relevant for prostate cancer susceptibility genes in general.