PBX3 is a putative biomarker of aggressive prostate cancer.

There is a great need to identify new and better prognostic and predictive biomarkers to stratify prostate cancer patients for optimal treatment. The aims of this study were to characterize the expression profile of pre-B cell leukemia homeobox (PBX) transcription factors in prostate cancer with an emphasis on investigating whether PBX3 harbours any prognostic value. The expression profile of PBX3 and PBX1 in prostate tissue was determined by immunohistochemical and immunoblot analysis. Furthermore, the expression of PBX3 transcript variants was analyzed by RT-PCR, NanoString Technologies®, and by analyzing RNA sequence data. The potential of PBX3 to predict prognosis, either at mRNA or protein level, was studied in four independent cohorts. PBX3 was mainly expressed in the nucleus of normal prostate basal cells, while it showed cytosolic expression in prostatic intraepithelial neoplasia and cancer cells. We detected four PBX3 transcript variants in prostate tissue. Competing risk regression analysis revealed that high PBX3 expression was associated with slower progression to castration resistant prostate cancer (sub-hazard ratio (SHR) 0.18, 95% CI: 0.081-0.42, p values < 0.001). PBX3 expression had a high predictive accuracy (area under the curve (AUC) = 0.82) when combined with Gleason score and age. Patients undergoing radical prostatectomy, with high levels of PBX3 mRNA, had improved prostate cancer specific survival compared to patients expressing low levels (SHR 0.21, 95% CI: 0.46-0.93, p values < 0.001, and AUC = 0.75). Our findings strongly indicate that PBX3 has potential as a biomarker, both as part of a larger gene panel and as an immunohistochemical marker, for aggressive prostate cancer.

Use of ß-blockers is associated with prostate cancer-specific survival in prostate cancer patients on androgen deprivation therapy.

BACKGROUND: Experimental evidence suggests a role for the ß(2) -adrenergic receptor pathway in prostate cancer (PCa). We have investigated the association of ß-blocker use with PCa incidence and survival in a Norwegian cohort. METHODS: Data from the Oslo II study in 2000 (n = 6515) were linked with information from the Cancer Registry of Norway and Statistics Norway. PCa risk and overall- and PCa-specific mortality were analyzed using uni- and multi-variable Cox- and competing risk regression models. RESULTS: At baseline, 776 men (11.9%) reported using a ß-blocker. 212 men (3.3%) were diagnosed with PCa before the survey, leaving 6,303 eligible for incidence analysis. During a median follow-up of 122 months, 448 (7.1%) men were diagnosed with PCa. ß-blocker use was not associated with PCa risk [hazard ratio (HR): 1.05, 95% CI: 0.79-1.40]. For all patients (n = 655; including med diagnosed before the survey), ß-blocker use was not associated with PCa-specific mortality (HR: 0.55, 95% CI 0.24-1.26, P = 0.16). However, in the subgroup of men planned to receive androgen deprivation therapy (ADT), as reported to the Cancer Registry (n = 263), ß-blocker use was associated with reduced PCa-specific mortality (HR: 0.14, 95% CI 0.02-0.85, P = 0.032). No effect on overall mortality was seen (HR, all patients: 0.88, 95% CI 0.56-1.38, P = 0.57). ß-blocker use did not appear to affect PSA level, Gleason score, or T-stage at diagnosis; however, these variables were missing for many cases. CONCLUSIONS: Our findings demonstrate a possible benefit of ß-blocker use for men treated with ADT, suggesting the need for investigation in larger cohorts.

Association of ß-Blocker Use at Time of Radical Prostatectomy With Rate of Treatment for Prostate Cancer Recurrence.

Importance: The perioperative period has gained attention as a window of opportunity to prevent cancer recurrence. Evidence in support of a role for nonselective ß-blockers (nsBBs) in cancer treatment is increasing, and counteracting cancer recurrence associated with perioperative stress and catecholamine is one of the suggested mechanisms of action. Objective: To explore whether use of nsBBs at the time of radical prostatectomy is associated with a lower rate of treatment for prostate cancer recurrence. Design, Setting, and Participants: This cohort study analyzed prospectively collected data from the Cancer Registry of Norway, Norwegian Patient Registry, Norwegian Prescription Database, and Norwegian Cause of Death Registry. Of 12 298 eligible patients, this study included 11 117 treatment-naive patients with prostate cancer (ie, no prior hormonal therapy, radiotherapy, or chemotherapy) who underwent radical prostatectomy in Norway from January 1, 2008, to December 31, 2015, with a minimum progression-free follow-up of 6 months. Data analysis was performed from April 20, 2020, to April 30, 2021. Exposures: Use of nsBBs and selective ß-blockers (sBBs) at time of radical prostatectomy. Main Outcomes and Measures: Treatment for cancer recurrence after radical prostatectomy (defined as initiation of hormonal therapy, radiotherapy, or chemotherapy) or, if no treatment was identified, cancer-specific mortality. Results: The study included 11 117 men with prostate cancer (median [IQR] age at radical prostatectomy, 64.8 [60.4-68.3] years). Of these, 1622 (14.6%) later received treatment for cancer recurrence during a median follow-up of 4.3 years (IQR, 2.4-6.3 years). Use of nsBBs at time of surgery among 209 patients was significantly associated with a lower risk of treatment for cancer recurrence (adjusted hazard ratio [aHR], 0.64; 95% CI, 0.42-0.96; P = .03). No such association was observed for use of sBBs (aHR, 0.96; 95% CI, 0.84-1.11; P = .62). Subanalyses with (1) relaxed inclusion criteria allowing for inclusion also of patients with early progression (within 6 months) and (2) only the healthiest patients (Eastern Cooperative Oncology Group performance status of 0) supported the main findings. Conclusions and Relevance: In this cohort study, use of nsBB but not sBBs at the time of radical prostatectomy was associated with less treatment initiation for cancer recurrence. This finding, together with accumulated preclinical and clinical evidence, provides a foundation for initiation of an interventional study.

The ß2-Adrenergic Receptor Is a Molecular Switch for Neuroendocrine Transdifferentiation of Prostate Cancer Cells.

The incidence of treatment-related neuroendocrine prostate cancer (t-NEPC) is rising as more potent drugs targeting the androgen signaling axis are clinically implemented. Neuroendocrine transdifferentiation (NEtD), an putative initial step in t-NEPC development, is induced by androgen-deprivation therapy (ADT) or anti-androgens, and by activation of the ß2-adrenergic receptor (ADRB2) in prostate cancer cell lines. Thus, understanding whether ADRB2 is involved in ADT-initiated NEtD may assist in developing treatment strategies that can prevent or reverse t-NEPC emergence, thereby prolonging therapeutic responses. Here we found that in primary, treatment-naïve prostate cancers, ADRB2 mRNA was positively correlated with expression of luminal differentiation markers, and ADRB2 protein levels were inversely correlated with Gleason grade. ADRB2 mRNA was upregulated in metastatic prostate cancer, and progressively downregulated during ADT and t-NEPC emergence. In androgen-deprivated medium, high ADRB2 was required for LNCaP cells to undergo NEtD, measured as increased neurite outgrowth and expression of neuron differentiation and neuroendocrine genes. ADRB2 overexpression induced a neuroendocrine-like morphology in both androgen receptor (AR)-positive and -negative prostate cancer cell lines. ADRB2 downregulation in LNCaP cells increased canonical Wnt signaling, and GSK3α/ß inhibition reduced the expression of neuron differentiation and neuroendocrine genes. In LNCaP xenografts, more pronounced castration-induced NEtD was observed in tumors derived from high than low ADRB2 cells. In conclusion, high ADRB2 expression is required for ADT-induced NEtD, characterized by ADRB2 downregulation and t-NEPC emergence. IMPLICATIONS: This data suggest a potential application of ß-blockers to prevent cancer cells committed to a neuroendocrine lineage from evolving into t-NEPC.

Observed correlation between the expression levels of catalytic subunit, Cß2, of cyclic adenosine monophosphate-dependent protein kinase and prostate cancer aggressiveness.

BACKGROUND: Today overtreatment of indolent prostate cancers and undertreatment of aggressive prostate cancer are a major concern for patients, their families, and the health care system. New biomarkers distinguishing indolent and aggressive prostate cancer are needed to improve precision medicine. In prostate cancer, protein kinase A (PKA) is known to activate the androgen receptor and published data indicate that PKA subunits can act as predictive markers for response to radiation and chemotherapy. We have previously shown that the catalytic subunit, Cß2, of PKA is up-regulated in prostate cancer and we would in this study investigate the potential of Cß2 to become a prognostic biomarker in prostate cancer. METHODS: Data were sampled from a total of 241 patients from 3 independent cohorts. We measured and compared Cß2 messenger RNA (mRNA) levels in prostate tumor and nontumor samples (n = 22), and exon levels in a cohort of 50 tumor samples, as well as acquiring mRNA data from the publicly available database The cancer genome atlas (n = 169). RESULTS: Cß2 mRNA was up-regulated in prostate cancer in all 3 cohorts, measured by 3 different methods. Furthermore, the relative Cß2 mRNA expression levels were lower in prostate cancer samples with Gleason score 8 to 10 compared with samples with Gleason score<8 (P = 0.004). Finally, low expression of Cß2 mRNA in prostate cancer biopsies correlated with poor survival (hazard ratio = 0.20; 95% CI: 0.048-0.86; P = 0.031), adjusted for risk group and age. CONCLUSIONS: We suggest that Cß2 mRNA expression may be used as a biomarker together with established prognostic markers to more precisely predict aggressiveness in patients diagnosed with prostate cancer.

Low ß2-adrenergic receptor level may promote development of castration resistant prostate cancer and altered steroid metabolism.

The underlying mechanisms responsible for the development of castration-resistant prostate cancer (CRPC) in patients who have undergone androgen deprivation therapy are not fully understood. This is the first study to address whether ß2-adrenergic receptor (ADRB2)- mediated signaling may affect CRPC progression in vivo. By immunohistochemical analyses, we observed that low levels of ADRB2 is associated with a more rapid development of CRPC in a Norwegian patient cohort. To elucidate mechanisms by which ADRB2 may affect CRPC development, we stably transfected LNCaP cells with shRNAs to mimic low and high expression of ADRB2. Two UDP-glucuronosyltransferases, UGT2B15 and UGT2B17, involved in phase II metabolism of androgens, were strongly downregulated in two LNCaP shADRB2 cell lines. The low-ADRB2 LNCaP cell lines displayed lowered glucuronidation activities towards androgens than high-ADRB2 cells. Furthermore, increased levels of testosterone and enhanced androgen responsiveness were observed in LNCaP cells expressing low level of ADRB2. Interestingly, these cells grew faster than high-ADRB2 LNCaP cells, and sustained their low glucuronidation activity in castrated NOD/SCID mice. ADRB2 immunohistochemical staining intensity correlated with UGT2B15 staining intensity in independent TMA studies and with UGT2B17 in one TMA study. Similar to ADRB2, we show that low levels of UGT2B15 are associated with a more rapid CRPC progression. We propose a novel mechanism by which ADRB2 may affect the development of CRPC through downregulation of UGT2B15 and UGT2B17.

ß-Adrenergic Receptor Signaling in Prostate Cancer.

Enhanced sympathetic signaling, often associated with obesity and chronic stress, is increasingly acknowledged as a contributor to cancer aggressiveness. In prostate cancer, intact sympathetic nerves are critical for tumor formation, and sympathectomy induces apoptosis and blocks tumor growth. Perineural invasion, involving enrichment of intra-prostatic nerves, is frequently observed in prostate cancer and is associated with poor prognosis. ß2-adrenergic receptor (ADRB2), the most abundant receptor for sympathetic signals in prostate luminal cells, has been shown to regulate trans-differentiation of cancer cells to neuroendocrine-like cells and to affect apoptosis, angiogenesis, epithelial-mesenchymal transition, migration, and metastasis. Epidemiologic studies have shown that use of ß-blockers, inhibiting ß-adrenergic receptor activity, is associated with reduced prostate cancer-specific mortality. In this review, we aim to present an overview on how ß-adrenergic receptor and its downstream signaling cascade influence the development of aggressive prostate cancer, primarily through regulating neuroendocrine differentiation.

Association between use of ß-blockers and prostate cancer-specific survival: a cohort study of 3561 prostate cancer patients with high-risk or metastatic disease.

BACKGROUND: We recently reported reduced prostate cancer (PCa)-specific mortality for ß-blocker users among patients receiving androgen-deprivation therapy in a health survey cohort including 655 PCa patients. Information on clinical characteristics was limited. OBJECTIVE: To assess the association between ß-blockers and PCa-specific mortality in a cohort of 3561 prostate cancer patients with high-risk or metastatic disease, and to address potential confounding from the use of statins or acetylsalicylic acid (ASA). DESIGN, SETTING, AND PARTICIPANTS: Clinical information from all men reported to the Cancer Registry of Norway with a PCa diagnosis between 2004 and 2009 (n=24 571) was coupled with information on filled prescriptions between 2004 and 2011 from the Norwegian Prescription Database. Exclusion criteria were low- or intermediate-risk disease; planned radiotherapy or radical prostatectomy; initiation of ß-blocker, ASA, or statin use after diagnosis where applicable; missing information on baseline Gleason score, prostate-specific antigen level, T stage or performance status; and missing follow-up. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Cox proportional hazards modelling and competing risk regression modelling were used to analyse the effects of ß-blocker use on all-cause and PCa-specific mortality, respectively. Differences between ß-blocker users and nonusers regarding baseline clinical characteristics were assessed by the Wilcoxon-Mann-Whitney U test, Pearson chi-square test, and Student t test. RESULTS AND LIMITATIONS: Median follow-up was 39 mo. ß-Blocker use was associated with reduced PCa mortality (adjusted subhazard ratio: 0.79; 95% confidence interval [CI], 0.68-0.91; p value: 0.001). The observed reduction in PCa mortality was independent of the use of statins or ASA. We observed no association with all-cause mortality (adjusted hazard ratio: 0.92; 95% CI, 0.83-1.02). The main limitations of the study were the observational study design and short follow-up. CONCLUSIONS: ß-Blocker use was associated with reduced PCa-specific mortality in patients with high-risk or metastatic disease at the time of diagnosis. Our findings need validation from further observational studies.