A Four-kallikrein Panel and ß-Microseminoprotein in Predicting High-grade Prostate Cancer on Biopsy: An Independent Replication from the Finnish Section of the European Randomized Study of Screening for Prostate Cancer.

BACKGROUND: A panel of four kallikrein markers (total, free, and intact prostate-specific antigen [PSA] and human kallikrein-related peptidase 2 [hK2]) improves predictive accuracy for Gleason score ≥7 (high-grade) prostate cancer among men biopsied for elevated PSA. A four-kallikrein panel model was originally developed and validated by the Dutch center of the European Randomized Study of Screening for Prostate Cancer (ERSPC). The kallikrein panel is now commercially available as 4Kscore™. OBJECTIVE: To assess whether these findings could be replicated among participants in the Finnish section of ERSPC (FinRSPC) and whether ß-microseminoprotein (MSP), a candidate prostate cancer biomarker, adds predictive value. DESIGN, SETTING, AND PARTICIPANTS: Among 4861 biopsied screening-positive participants in the first three screening rounds of FinRSPC, a case-control subset was selected that included 1632 biopsy-positive cases matched by age at biopsy to biopsy-negative controls. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: The predictive accuracy of prespecified prediction models was compared with biopsy outcomes. RESULTS AND LIMITATIONS: Among men with PSA of 4.0-25ng/ml, 1111 had prostate cancer, 318 of whom had high-grade disease. Total PSA and age predicted high-grade cancer with an area under the curve of 0.648 (95% confidence interval [CI] 0.614-0.681) and the four-kallikrein panel increased discrimination to 0.746 (95% CI 0.717-0.774). Adding MSP to the four-kallikrein panel led to a significant (Wald test; p=0.015) but small increase (0.003) in discrimination. Limitations include a risk of verification bias among men with PSA of 3.0-3.99ng/ml and the absence of digital rectal examination results. CONCLUSIONS: These findings provide additional evidence that kallikrein markers can be used to inform biopsy decision-making. Further studies are needed to define the role of MSP. PATIENT SUMMARY: Four kallikrein markers and ß-microseminoprotein in blood improve discrimination of high-grade prostate cancer at biopsy in men with elevated prostate-specific antigen.

Androgen Receptor Deregulation Drives Bromodomain-Mediated Chromatin Alterations in Prostate Cancer.

Global changes in chromatin accessibility may drive cancer progression by reprogramming transcription factor (TF) binding. In addition, histone acetylation readers such as bromodomain-containing protein 4 (BRD4) have been shown to associate with these TFs and contribute to aggressive cancers including prostate cancer (PC). Here, we show that chromatin accessibility defines castration-resistant prostate cancer (CRPC). We show that the deregulation of androgen receptor (AR) expression is a driver of chromatin relaxation and that AR/androgen-regulated bromodomain-containing proteins (BRDs) mediate this effect. We also report that BRDs are overexpressed in CRPCs and that ATAD2 and BRD2 have prognostic value. Finally, we developed gene stratification signature (BROMO-10) for bromodomain response and PC prognostication, to inform current and future trials with drugs targeting these processes. Our findings provide a compelling rational for combination therapy targeting bromodomains in selected patients in which BRD-mediated TF binding is enhanced or modified as cancer progresses.

Microseminoprotein-Beta Expression in Different Stages of Prostate Cancer.

Microseminoprotein-beta (MSMB, MSMB) is an abundant secretory protein contributed by the prostate, and is implicated as a prostate cancer (PC) biomarker based on observations of its lower expression in cancerous cells compared with benign prostate epithelium. However, as the current literature on MSMB is inconsistent, we assessed the expression of MSMB at the protein and mRNA levels in a comprehensive set of different clinical stages of PC. Immunohistochemistry using monoclonal and polyclonal antibodies against MSMB was used to study protein expression in tissue specimens representing prostatectomies (n = 261) and in diagnostic needle biopsies from patients treated with androgen deprivation therapy (ADT) (n = 100), and in locally recurrent castration-resistant PC (CRPC) (n = 105) and CRPC metastases (n = 113). The transcript levels of MSMB, nuclear receptor co-activator 4 (NCOA4) and MSMB-NCOA4 fusion were examined by qRT-PCR in prostatectomy samples and by RNA-sequencing in benign prostatic hyperplasia, PC, and CRPC samples. We also measured serum MSMB levels and genotyped the single nucleotide polymorphism rs10993994 using DNA from the blood of 369 PC patients and 903 controls. MSMB expression in PC (29% of prostatectomies and 21% of needle biopsies) was more frequent than in CRPC (9% of locally recurrent CRPCs and 9% of CRPC metastases) (p<0.0001). Detection of MSMB protein was inversely correlated with the Gleason score in prostatectomy specimens (p = 0.024). The read-through MSMB-NCOA4 transcript was detected at very low levels in PC. MSMB levels in serum were similar in cases of PC and controls but were significantly associated with PC risk when adjusted for age at diagnosis and levels of free or total PSA (p<0.001). Serum levels of MSMB in both PC patients and controls were significantly associated with the rs10993994 genotype (p<0.0001). In conclusion, decreased expression of MSMB parallels the clinical progression of PC and adjusted serum MSMB levels are associated with PC risk.

Recurrent SKIL-activating rearrangements in ETS-negative prostate cancer.

Prostate cancer is the third most common cause of male cancer death in developed countries, and one of the most comprehensively characterized human cancers. Roughly 60% of prostate cancers harbor gene fusions that juxtapose ETS-family transcription factors with androgen regulated promoters. A second subtype, characterized by SPINK1 overexpression, accounts for 15% of prostate cancers. Here we report the discovery of a new prostate cancer subtype characterized by rearrangements juxtaposing the SMAD inhibitor SKIL with androgen regulated promoters, leading to increased SKIL expression. SKIL fusions were found in 6 of 540 (1.1%) prostate cancers and 1 of 27 (3.7%) cell lines and xenografts. 6 of 7 SKIL-positive cancers were negative for ETS overexpression, suggesting mutual exclusivity with ETS fusions. SKIL knockdown led to growth arrest in PC-3 and LNCaP cell line models of prostate cancer, and its overexpression led to increased invasiveness in RWPE-1 cells. The role of SKIL as a prostate cancer oncogene lends support to recent studies on the role of TGF-ß signaling as a rate-limiting step in prostate cancer progression. Our findings highlight SKIL as an oncogene and potential therapeutic target in 1-2% of prostate cancers, amounting to an estimated 10,000 cancer diagnoses per year worldwide.