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.

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.

Clinical and Functional Analyses of an African-ancestry Gain-of-function HOXB13 Variant Implicated in Aggressive Prostate Cancer.

BACKGROUND: Recent reports have uncovered a HOXB13 variant (X285K) predisposing to prostate cancer in men of West African ancestry. The clinical relevance and protein function associated with this inherited variant are unknown. OBJECTIVE: To determine the clinical relevance of HOXB13 (X285K) in comparison with HOXB13 (G84E) and BRCA2 pathogenic/likely pathogenic (P/LP) variants, and to elucidate the oncogenic mechanisms of the X285K protein. DESIGN, SETTING, AND PARTICIPANTS: Real-world data were collected from 21,393 men with prostate cancer undergoing genetic testing from 2019 to 2022, and in vitro cell-line models were established for the evaluation of oncogenic functions associated with the X285K protein. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Genetic testing results were compared among patient groups according to self-reported race/ethnicity, Gleason scores, and American Joint Committee on Cancer stages using the exact test. Oncogenic functions of X285K were evaluated by RNA sequencing, chromatin immunoprecipitation sequencing, and Western blot analyses. RESULTS AND LIMITATIONS: HOXB13 (X285K) was significantly enriched in self-reported Black (1.01%) versus White (0.01%) patients. We observed a trend of more aggressive disease in the HOXB13 (X285K) and BRCA2 P/LP carriers than in the HOXB13 (G84E) carriers. Replacement of the wild-type HOXB13 protein with the X285K protein resulted in a gain of an E2F/MYC signature, validated by the elevated expression of cyclin B1 and c-Myc, without affecting the androgen response signature. Elevated expression of cyclin B1 and c-Myc was explained by enhanced binding of the X285K protein to the promoters and enhancers of these genes. The limitations of the study are the lack of complete clinical outcome data for all patients studied and the use of a single cell line in the functional analysis. CONCLUSIONS: HOXB13 (X285K) is significantly enriched in self-reported Black patients, and X285K carriers detected in the real-world clinical setting have aggressive prostate cancer features similar to the BRCA2 carriers. Functional studies revealed a unique gain-of-function oncogenic mechanism of X285K protein in regulating E2F/MYC signatures. PATIENT SUMMARY: The HOXB13 (X285K) variant is clinically and functionally linked to aggressive prostate cancer, supporting genetic testing for X285K in Black men and early disease screening of carriers of this variant.

A novel method for detection of exfoliated prostate cancer cells in urine by RNA in situ hybridization.

BACKGROUND: In the current study, we explore the feasibility of detecting exfoliated prostate cancer cells in urine using an RNA in situ hybridization (RISH) assay. We hypothesized that robust and specific labeling of prostate cancer cells could be achieved in post-digital rectal examination (DRE) urine samples using RISH. METHODS: We focused on method development, optimization, and analytical evaluation of RISH-based detection of prostate cancer in urine. We optimized a sample collection, processing, and target detection workflow for urine cytology specimens in conjunction with RNA target detection by RISH. We screened a panel of 11 prostate-specific RNA targets, and selected NKX3-1 and PRAC1 as markers for cells of prostate origin and PCA3 as a marker of prostate malignancy. Following analytical validation of a multiplexed NKX3-1/PRAC1/PCA3 assay, we evaluated whether prostate cancer cells can be detected in a pilot cohort of 19 post-DRE specimens obtained from men diagnosed with prostate cancer. RESULTS: Using cytology specimens prepared from spiked urine samples, we established the analytical validity of the RISH assay for detection and visualization of prostate cells in urine. Cells of prostate origin could be readily and specifically identified and separated into benign and malignant cell populations based on the multiplex test that consisted of markers specific for prostate cells (NKX3-1, PRAC1) and prostate cancer cells (PCA3). Upon evaluation of post-DRE urine from a pilot cohort of prostate cancer patients, we identified 11 samples in which prostate cells were present, 6 of which were also positive for prostate cancer cells. CONCLUSIONS: Multiplex RISH enables the direct visualization and molecular characterization of individual exfoliated prostate cells in urine. This proof-of-principle study provides evidence supporting the application of RISH as a potential noninvasive tool for prostate cancer detection.

Approaches to urinary detection of prostate cancer.

BACKGROUND: Prostate cancer is the most common cancer in American men that ranges from low risk states amenable to active surveillance to high-risk states that can be lethal especially if untreated. There is a critical need to develop relatively non-invasive and clinically useful methods for screening, detection, prognosis, disease monitoring, and prediction of treatment efficacy. In this review, we focus on important advances as well as future efforts needed to drive clinical innovation in this area of urine biomarker research for prostate cancer detection and prognostication. METHODS: We provide a review of current literature on urinary biomarkers for prostate cancer. We evaluate the strengths and limitations of a variety of approaches that vary in sampling strategies and targets measured; discuss reported urine tests for prostate cancer with respect to their technical, analytical, and clinical parameters; and provide our perspectives on critical considerations in approaches to developing a urine-based test for prostate cancer. RESULTS: There has been an extensive history of exploring urine as a source of biomarkers for prostate cancer that has resulted in a variety of urine tests that are in current clinical use. Importantly, at least three tests have demonstrated high sensitivity (~90%) and negative predictive value (~95%) for clinically significant tumors; however, there has not been widespread adoption of these tests. CONCLUSIONS: Conceptual and methodological advances in the field will help to drive the development of novel urinary tests that in turn may lead to a shift in the clinical paradigm for prostate cancer diagnosis and management.