Systemic interrogation of immune-oncology-related proteins in patients with locally advanced prostate cancer undergoing androgen deprivation and intensity-modulated radiotherapy.

PURPOSE: The primary objective was to establish whether blood-based leucine-rich alpha-2-glycoprotein (LRG1) can predict outcomes in patients with locally advanced prostate cancer undergoing androgen-deprivation therapy (ADT) and radiotherapy (RT) and to determine how it may relate to 92 immune-oncology (I-O)-related proteins in this setting. METHODS: Baseline blood level of LRG1 from patients treated with ADT and RT enrolled in the CuPCa (n = 128) and IMRT (n = 81) studies was measured using ELISA. A longitudinal cohort with matched blood samples from start of ADT, start of RT, and end of RT protocol from 47 patients from the IMRT cohort was used to establish levels of I-O proteins by high-multiplexing Proximal Extension Assay by Olink Proteomics. Statistical analyses using Kaplan-Meier, Cox regression, and LIMMA analyses were applied to predict the prognostic value of LRG1 and its correlation to I-O proteins. RESULTS: High baseline levels of LRG1 predicted a low frequency of treatment failure in patients undergoing ADT + RT in both the CuPCa and the IMRT cohorts. LRG1 was moderately correlated with CD4, IL6, and CSF1. We identified I-O proteins predicting metastatic failure (MF) at different timepoints. CONCLUSION: LRG1 biomarker is associated with I-O proteins and can be used to improve stratification and monitoring of prostate cancer patients undergoing ADT + RT. This work will require further in-depth analyses in independent cohorts with treatment outcome data.

Correlation of expression of Major Vault Protein with androgen receptor and immune checkpoint protein B7-H3, and with poor prognosis in prostate cancer.

Prostate cancer diagnosis and early stratification is an important aspect to avoid undertreatment of high-risk prostate cancer patients. Major Vault Protein (MVP) has been proposed as a prognostic biomarker in prostate cancer. PTEN and the immune checkpoint protein B7-H3 interact with MVP and are important in prostate cancer progression and therapy response. We evaluated the expression of MVP by immunohistochemistry of tissue microarray samples from a retrospective cohort consisting of 119 prostate cancer patients. We correlated the protein expression of MVP with clinicopathological characteristics, and protein expression of androgen receptor (AR), PTEN, immune checkpoint proteins B7-H3 and PD-L1. We found MVP to be expressed in 53 % of prostate tumors, and correlated positively with biochemical recurrence (ρ = 0.211/p = 0.021). Furthermore, we found positive correlation of MVP expression with expression of AR (ρ = 0.244/p = 0.009) and the immune checkpoint protein B7-H3 (ρ = 0.200/p = 0.029), but not with PD-L1 (ρ = 0.152/p = 0.117) or PTEN expression (ρ = - 0.034/p = 0.721). Our findings support the notion that expression of MVP is associated with poor prognosis in prostate cancer. The correlation between MVP and immune checkpoint protein B7-H3 in prostate cancer suggests a role for MVP in immunoregulation and drug resistance.

Low Blood Levels of LRG1 Before Radical Prostatectomy Identify Patients with High Risk of Progression to Castration-resistant Prostate Cancer.

Background: After radical prostatectomy (RP), depending on stage, up to 40% of patients with prostate cancer (PCa) will experience biochemical failure (BF). Despite salvage therapy, approximately one-third of these patients will need permanent hormone therapy (pHT) and are at risk of progression to castration-resistant PCa (CRPC). Prognostic markers herald the need for neoadjuvant, adjuvant, or multimodal treatment. Objective: To evaluate the added value of blood LRG1 in predicting treatment failure in patients who have undergone radical prostatectomy (RP). Design setting and participants: We quantified LRG1 in serum or plasma sampled before radical prostatectomy from patients from the Martini-Klinik (Martini; n = 423), the Danish CuPCa cohort (CuPCa; n = 182), and Oslo University Hospital (OUH; n = 145). Outcome measurements and statistical analysis: The endpoints were BF, pHT, and CRPC. The association between LRG1 and survival outcomes was evaluated using Kaplan-Meier estimation and Cox proportional-hazards modeling. The added predictive value of LRG1 in nested models was estimated using the concordance index, time-dependent area under the receiver operating characteristic curve, and decision curve analysis. Results and limitations: In multivariable Cox models using preoperative characteristics, LRG1 was associated with an estimated lower risk of BF in the Martini cohort (adjusted hazard ratio [aHR] 0.68, 95% confidence interval [CI] 0.52-0.90) and in the CuPCa cohort (aHR 0.47, 95% CI 0.30-0.73). Using preoperative prognostic variables, our data showed that doubling of LRG1 was also associated with a lower risk of pHT receipt in the CuPCa cohort (aHR 0.43, 95% CI 0.20-0.93) and of CRPC development in the OUH cohort (aHR 0.32, 95% CI 0.15-0.69). Similar aHR values were observed using either preoperative or postoperative variables for all endpoints. Conclusions: PCa patients with high blood LRG1 are at lower risk of BF, pHT receipt, and progression to CRPC. Since LRG1 adds value to established prognostic models, new prognostic factor combinations including LRG1 should be considered in future studies. Patient summary: We measured concentrations of the blood-based protein LRG1 before surgery for prostate cancer. Patients with high LRG1 levels had better disease-free survival, suggesting that LRG1 can help in predicting prognosis.

Implication of ß2-adrenergic receptor and miR-196a correlation in neurite outgrowth of LNCaP prostate cancer cells.

The ß2-adrenergic receptor has been shown to be involved in neuroendocrine differentiation and to contribute to the development of aggressive prostate cancer. In this study we have investigated whether miR-196a plays a role in the regulation of the ß2-adrenergic receptor in the LNCaP prostate cancer cell line. Our results show that the expression of miR-196a is elevated in LNCaP prostate cancer cells with reduced levels of ß2-adrenergic receptor after stably transfection with three different shRNAs. Furthermore, treatment with ß-blockers showed that this upregulation is strictly related to the low levels of ß2-adrenergic receptor and not to the inhibition of the receptor signaling activity. Finally, we found that the reduced ability of LNCaP cells with low levels of ß2-adrenergic receptor to initiate neuroendocrine differentiation under androgen depletion conditions is mediated by miR-196a. In conclusion, this study provides the rational for a role of miR-196a in the ß2-adrenergic receptor mediated neuroendocrine differentiation of LNCaP prostate cancer cells.

Proteomic analyses identify major vault protein as a prognostic biomarker for fatal prostate cancer.

The demographic shift toward an older population will increase the number of prostate cancer cases. A challenge in the treatment of prostate cancer is to avoid undertreatment of patients at high risk of progression following curative treatment. These men can benefit from early salvage treatment. An explorative cohort consisting of tissue from 16 patients who underwent radical prostatectomy, and were either alive or had died from prostate cancer within 10 years postsurgery, was analyzed by mass spectrometry analysis. Following proteomic and bioinformatic analyses, major vault protein (MVP) was identified as a putative prognostic biomarker. A publicly available tissue proteomics dataset and a retrospective cohort of 368 prostate cancer patients were used for validation. The prognostic value of the MVP was verified by scoring immunohistochemical staining of a tissue microarray. High level of MVP was associated with more than 4-fold higher risk for death from prostate cancer (hazard ratio = 4.41, 95% confidence interval: 1.45-13.38; P = 0.009) in a Cox proportional hazard models, adjusted for Cancer of the Prostate Risk Assessments Post-surgical (CAPRA-S) score and perineural invasion. Decision curve analyses suggested an improved standardized net benefit, ranging from 0.06 to 0.18, of adding MVP onto CAPRA-S score. This observation was confirmed by receiver operator characteristics curve analyses for the CAPRA-S score versus CAPRA-S and MVP score (area under the curve: 0.58 versus 0.73). From these analyses, one can infer that MVP levels in combination with CAPRA-S score might add onto established risk parameters to identify patients with lethal prostate cancer.

Identification and Validation of Leucine-rich α-2-glycoprotein 1 as a Noninvasive Biomarker for Improved Precision in Prostate Cancer Risk Stratification.

BACKGROUND: More accurate risk assessments are needed to improve prostate cancer management. OBJECTIVE: To identify blood-based protein biomarkers that provided prognostic information for risk stratification. DESIGN SETTING AND PARTICIPANTS: Mass spectrometry was used to identify biomarker candidates from blood, and validation studies were performed in four independent cohorts retrospectively collected between 1988 and 2015. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: The primary outcome objectives were progression-free survival, prostate cancer-specific survival (PCSS), and overall survival. Statistical analyses to assess survival and model performance were performed. RESULTS AND LIMITATION: Serum leucine-rich α-2-glycoprotein 1 (LRG1) was found to be elevated in fatal prostate cancer. LRG1 provided prognostic information independent of metastasis and increased the accuracy in predicting PCSS, particularly in the first 3 yr. A high LRG1 level is associated with an average of two-fold higher risk of disease-progression and mortality in both high-risk and metastatic patients. However, our study design, with a retrospective analysis of samples spanning several decades back, limits the assessment of the clinical utility of LRG1 in today's clinical practice. Thus, independent prospective studies are needed to establish LRG1 as a clinically useful biomarker for patient management. CONCLUSIONS: High blood levels of LRG1 are unfavourable in newly diagnosed high-risk and metastatic prostate cancer, and LRG1 increased the accuracy of risk stratification of prostate cancer patients. PATIENT SUMMARY: High blood levels of leucine-rich α-2-glycoprotein 1 are unfavourable in newly diagnosed high-risk and metastatic prostate cancer.

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.

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.

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.

TWIST1, A novel androgen-regulated gene, is a target for NKX3-1 in prostate cancer cells.

BACKGROUND: TWIST1 plays a key role in EMT-mediated tumor invasion and metastasis. Since bone metastasis is a hallmark of advanced prostate cancer and is detected in at least 85% of patients who die of this disease, it is of great importance to understand the regulation of the cellular signaling pathways involved in the metastatic process. METHODS: Prostatic cell lines were analyzed using real time RT-PCR, chromatin immunoprecipitations (ChIP) and transfection of siRNA's and reporter constructs. RESULTS: We report in this paper that TWIST1 is an androgen-regulated gene under tight regulation of NKX3-1. Androgens repress the expression of TWIST1 via NKX3-1, which is a prostate-specific tumor suppressor that is down-regulated in the majority of metastatic prostate tumors. We show that NKX3-1 binds to the TWIST1 promoter and that NKX3-1 over-expression reduces the activity of a TWIST1 promoter reporter construct, whereas NKX3-1 siRNA up-regulates endogenous TWIST1 mRNA in prostate cancer cells. CONCLUSION: Our finding that NKX3-1 represses TWIST1 expression emphasizes the functional importance of NKX3-1 in regulating TWIST1 expression during prostate cancer progression to metastatic disease.

The effects of short-term genistein intervention on prostate biomarker expression in patients with localised prostate cancer before radical prostatectomy.

Nutritionally relevant levels of genistein, the predominant isoflavone in soyabean associated with lower risk of prostate cancer (PCa), may modulate the expression of prostate tissue biomarkers associated with cancer prediction and progression. A phase 2 placebo-controlled, randomised, double-blind clinical trial was conducted in forty-seven Norwegian patients before prostatectomy. Intervention was 30 mg genistein or placebo capsules daily for 3-6 weeks. Luminal cells from malignant and benign glands were isolated with laser capture microdissection and the mRNA levels of androgen-related biomarkers (androgen receptor, NK3 homeobox 1, kallikrein-related peptide 4 (KLK4)) and cell cycle-related genes (p21 Waf1/Cip1 , p27 Kip1 , p53) were analysed with real-time semiquantitative PCR. Immunohistochemistry of androgen-, cell cycle-, proliferative- (Ki67 nuclear antigen), apoptotic- (B-cell CLL/lymphoma 2 (BCL-2) and BCL-2-associated X protein) and neuroendocrine differentiation-related biomarkers (neuron-specific enolase and cytoplasmic chromogranin A) was performed using tissue microarrays containing normal, Gleason grade 3 and grade 4 prostate tissues. There were no significant effects by genistein intervention on proliferation-, cell cycle-, apoptosis- or neuroendocrine biomarkers. Genistein intervention, however, significantly reduced the mRNA level of KLK4 in tumour cells (P = 0·033) and there was a non-significant reduction in androgen and cell cycle-related biomarkers, except for p27Kip1, whose expression in the nuclear compartment was increased. Genistein intervention modulated the expression of several biomarkers which may be related to PCa prediction and progression. The present study supports genistein as a chemopreventive agent in PCa. Further investigation is warranted in larger and longer-duration studies.

Efficacy and safety of short-term genistein intervention in patients with localized prostate cancer prior to radical prostatectomy: a randomized, placebo-controlled, double-blind Phase 2 clinical trial.

We conducted a placebo-controlled, block-randomized double-blind Phase 2 study to examine the effect of 30 mg synthetic genistein daily on serum and tissue biomarkers in patients with localized prostate cancer (CaP). Fifty-four study subjects were recruited and randomized to treatment with genistein (n = 23) or placebo (n = 24) for 3 to 6 wk prior to prostatectomy. Seven study subjects were noncompliant to the study protocol. Adverse events were few and mild. Serum prostate specific antigen (PSA) decreased by 7.8% in the genistein arm and increased by 4.4% in the placebo arm (P = 0.051). The PSA level was reduced in tumor tissue compared to normal tissue in the placebo arm. In the genistein arm, the PSA level in tumor and normal tissue was comparable. Total cholesterol was significantly lower in the genistein arm (P = 0.013). There were no significant effects on thyroid or sex hormones. Plasma concentrations of total genistein were on average 100-fold higher in the genistein arm after treatment (P < 0.001). Genistein at a dose that can be easily obtained from a diet rich in soy reduced the level of serum PSA in patients with localized CaP, without any effects on hormones. It was well tolerated and had a beneficial effect on blood cholesterol.

Regulation of PBX3 expression by androgen and Let-7d in prostate cancer.

BACKGROUND: The pre-leukemia transcription factor 3 (PBX) is part of the PBX family of transcription factors, which is known to regulate genes involved in differentiation of urogenital organs and steroidogenesis. This is of interest with regard to prostate cancer progression as regulation of steroidogenesis is one of the mechanisms involved in the development of castration-resistant prostate cancer. In light of this we wanted to investigate the possible involvement of androgen regulation of PBX3 expression in prostate cancer. RESULTS: In this study, we show that PBX3 is post-transcriptionally regulated by androgen in prostate cancer cells and that the effect might be independent of the androgen receptor. Furthermore, PBX3 was identified as a target of Let-7d, an androgen regulated microRNA. Let-7d was down-regulated in malignant compared to benign prostate tissue, whereas up-regulation of PBX3 expression was observed. CONCLUSIONS: We demonstrate that PBX3 is up-regulated in prostate cancer and post- transcriptionally regulated by androgen through Let-7d.

Hormonal regulation of beta2-adrenergic receptor level in prostate cancer.

BACKGROUND: Androgen deprivation is the only effective systemic therapy available for patients with prostatic carcinoma, but is associated with a gradual transition to a hormone-refractory prostate cancer (HRCAP) in which ligand-independent activation of the androgen receptor has been implicated. The beta(2)-adrenergic receptor (beta(2)-AR) is a well-known activator of the androgen receptor. METHODS: Prostatic cell lines were analyzed using cDNA micro-array, real time RT-PCR, radioligand binding assay, cAMP measurements, transfection and thymidine incorporation assay. Clinical specimens were studied by immunohistochemistry and Affymetrix microarrays. RESULTS: Here, we show that beta(2)-AR was transiently down-regulated both at mRNA- and protein levels when hormone-sensitive prostate cancer cells, LNCaP, were cultured in steroid stripped medium (charcoal-stripped fetal calf serum) or when the cells were treated with the anti-androgen, bicalutamide (Casodex). The number of beta-adrenergic receptors was modestly up-regulated in androgen independent cell lines (LNCaP-C4, LNCaP-C4-2 and DU145) compared to LNCaP. Triiodothyronine (T3) increased the level of beta(2)-AR and the effect of T3 was inhibited by bicalutamide. Immunohistochemical staining of human prostate specimens showed high expression of beta(2)-AR in glandular, epithelial cells and increased expression in malignant cells compared to benign hyperplasia and normal tissue. Interestingly, beta(2)-AR mRNA was strongly down-regulated by androgen ablation therapy of prostate cancer patients. CONCLUSION: The level of beta(2)-AR was increased by T3 in prostatic adenocarcinoma cells and reduced in prostate cancer patients who had received androgen ablation therapy for 3 months.

Androgen dependent regulation of protein kinase A subunits in prostate cancer cells.

Neuroendocrine (NE) cells may play a role in prostate cancer progression. Both androgen deprivation and cAMP are well known inducers of NE differentiation (NED) in the prostate. Gene-expression profiling of LNCaP cells, incubated in androgen stripped medium, showed that the Cbeta isoform of PKA is up-regulated during NE differentiation. Furthermore, by using semi-quantitative RT-PCR and immunoblotting analysis, we observed that the Cbeta splice variants are differentially regulated during this process. Whereas the Cbeta2 splice variant is down-regulated in growth arrested LNCaP cells, the Cbeta1, Cbeta3 and Cbeta4 variants, as well as the RIIbeta subunit of PKA, are induced in NE-like LNCaP cells. The opposite effect of Cbeta expression could be mimicked by androgen stimulation, implying the Cbeta gene of PKA as a putative new target gene for the androgen receptor in prostate cancer. Moreover, to investigate expression of PKA subunits during prostate cancer progression, we did immunoblotting of several prostatic cell lines and normal and tumor tissue from prostate cancer patients. Interestingly, multiple Cbeta subunits were also observed in human prostate specimens, and the Cbeta2 variant was up-regulated in tumor cells. In conclusion, it seems that the Cbeta isoforms play different roles in proliferation and differentiation and could therefore be potential markers for prostate cancer progression.