Implication of β2-adrenergic receptor and miR-196a correlation in neurite outgrowth of LNCaP prostate cancer cells

The β2-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 β2-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 β2-adrenergic receptor after stably transfection with three different shRNAs. Furthermore, treatment with β-blockers showed that this upregulation is strictly related to the low levels of β2-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 β2-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 β2-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.

Serum levels of inflammation-related markers and metabolites predict response to neoadjuvant chemotherapy with and without bevacizumab in breast cancers

Angiogenesis is necessary for tumor growth and has been targeted in breast cancer; however, it is unclear which patients will respond and benefit from antiangiogenic therapy. We report noninvasive monitoring of patient response to neoadjuvant chemotherapy given alone or in combination with anti-vascular endothelial growth factor (bevacizumab) in a randomized clinical trial. At four time points during neoadjuvant chemotherapy ± bevacizumab of receptor tyrosine-protein kinase erbB-2-negative breast cancers, we measured metabolites and inflammation-related markers in patient's serum. We report significant changes in the levels of several molecules induced by bevacizumab, the most prominent being an increase in pentraxin 3 (PTX3) and von Willebrand factor (VWF). Serum levels of AXL, VWF and pulmonary and activation-regulated cytokine (PARC/CCL18) reflected response to chemotherapy alone or in combination with bevacizumab. We further analyzed serum cytokines in relation to tumor characteristics such as gene expression, tumor metabolites and tumor infiltrating leukocytes. We found that VWF and growth-differentiation factor 15 tumor mRNA levels correlated with their respective serum protein levels suggesting that these cytokines may be produced by tumors and outflow to the bloodstream while influencing the tumor microenvironment locally. Finally, we used binomial logistic regression which allowed to predict patient's response using only 10 noninvasive biomarkers. Our study highlights the potential of monitoring circulating levels of cytokines and metabolites during breast cancer therapy.

Low Expression of miR-424-3p is Highly Correlated with Clinical Failure in Prostate Cancer

Prostate cancer (PC) is a highly heterogenous disease and one of the leading causes of mortality in developed countries. Recently, studies have shown that expression of immune checkpoint proteins are directly or indirectly repressed by microRNAs (miRs) in many types of cancers. The great advantages of using miRs based therapy is the capacity of these short transcripts to target multiple molecules for the same- or different pathways with synergistic immune inhibition effects. miR-424 has previously been described as a biomarker of poor prognosis in different types of cancers. miR-424 is also found to target both the CTLA-4/CD80- and PD-1/PD-L1 axis. In the present study, the clinical significance of miR-424-3p expression in PC tissue was evaluated. Naïve radical prostatectomy specimens from 535 patients was used for tissue microarray construction. In situ hybridization was used to evaluate the expression of miR-424-3p and immunohistochemistry was used for CTLA-4 protein detection. In univariate- and multivariate analyses, low expression of miR-424-3p was significant associated with clinical failure-free survival, (p = 0.004) and p = 0.018 (HR:0.44, CI95% 0.22-0.87). Low expression of miR-424-3p also associated strongly with aggressive phenotype of PC. This highlight the importance of miR-424-3p as potential target for therapeutic treatment in prostate cancer.

Abstract B015: Potential systemic effects of beta-blocker use in prostate cancer patients

Background: In 2014, our group published an association between use of beta-blockers and superior prostate cancer (PCa) specific survival. Although debated, the association has also been observed in other cancer forms such as breast cancer and malignant melanoma. Although several potential mechanisms have been suggested, a biologic mechanism explaining these associations is still unknown. However, the diversity of cancer forms in which the association has been observed suggests that systemic mechanisms not directly related to prostate biology might play a role.

Aim: In this project, we will look for potential biologic mechanisms explaining increased PCa specific survival time among beta-blocker users. Specifically, we will look for associations between known oncologic/immunologic markers and beta-blocker use prior to diagnosis.

Method: We have selected 90 serum samples from PCa patients treated with radical prostatectomy at Oslo University Hospital, Aker, in the period 2006-2011. Clinical and pathologic information were coupled with data from the Norwegian Prescription Database, which records all use of prescription drugs by the Norwegian population. We calculated a propensity score, based on observed baseline characteristics including age, BMI and T-stage, using beta-blocker use as the outcome. We then selected the 45 beta-blocker users with most aggressive PCAs, and identified suitable controls using the propensity score.

The serum samples were analyzed by OLINK Proteomics, using a semiquantitative reagent kit designed to measure 92 predefined and separate protein analytes related to immuno-oncology.

Results and Conclusion: The statistical analysis is currently ongoing as of September 12th, 2017. Interesting finds, together with a brief overview of the method, will be presented at the conference.

Based on previous findings on two different multiplex platforms, we have indications that serum levels of the proteins VEGF, IL6 and TNF might be different between beta-blocker users and non-users. Hence, we have a priori hypotheses regarding these proteins.

After finishing the analysis of these proteins, we will run an open approach analysis to reveal if any other analytes differ with beta-blocker usage. We will also look for clustering of related proteins. The study design also allows for a more explorative analysis of associations between the analyzed proteins and prognostic factors, as well as follow-up (both biochemical recurrence free- and overall survival), not related to beta-blocker use.

We consider this type of study to be a necessary step towards a potential future randomized clinical trial to assess beta blockers’ utility as adjuvant treatment for aggressive PCa.

Citation Format: Helene H. Grytli, Haakon Ramberg, Peder R. Braadland, Heidi K. Nielsen, Ingrid J. Guldvik, Kristin A. Taskén. Potential systemic effects of beta-blocker use in prostate cancer patients [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr B015.

Levels and prognostic impact of circulating markers of inflammation, endothelial activation and extracellular matrix remodelling in patients with lung cancer and chronic obstructive pulmonary disease

Background

The development of both chronic obstructive pulmonary disease (COPD) and lung cancer (LC) is influenced by smoking related chronic pulmonary inflammation caused by an excessive innate immune response to smoke exposure. In addition, the smoking induced formation of covalent bonds between the carcinogens and DNA and the accumulation of permanent somatic mutations in critical genes are important in the carcinogenic processes, and can also induce inflammatory responses.

How chronic inflammation is mirrored by serum markers in COPD and LC and if these markers reflect prognosis in patients with LC is, however, largely unknown.

Methods

Serum levels of 18 markers reflecting inflammation, endothelial activation and extracellular matrix remodelling were analysed in 207 patients with non-small lung carcinoma (NSCLC) before surgery and 42 COPD patients. 56% of the LC patients also suffered from COPD. The serum samples were analysed by enzyme immunoassays.

Results

Serum levels of OPG, PTX3, AXL, ALCAM, sCD163, CD147, CatS and DLL1 were significantly higher in patients with COPD as compared to patients with LC. High sTNFR1 levels were associated with improved progression free survival (PFS) and overall survival (OS) in LC patients with (PFS hazard ratio (HR) 0.49, OS HR 0.33) and without COPD (OS HR 0.30). High levels of OPG were associated with improved PFS (HR 0.17) and OS (HR 0.14) for LC with COPD. CRP was significantly associated with overall survival regardless of COPD status.

Conclusion

Several markers reflecting inflammation, endothelial activation and extracellular matrix remodelling are elevated in serum from patients with COPD compared to LC patients. Presence of COPD might influence the levels of circulating biomarkers. Some of these markers are also associated with prognosis.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4659-0) contains supplementary material, which is available to authorized users.

Ex vivo metabolic fingerprinting identifies biomarkers predictive of prostate cancer recurrence following radical prostatectomy

Background:

Robust biomarkers that identify prostate cancer patients with high risk of recurrence will improve personalised cancer care. In this study, we investigated whether tissue metabolites detectable by high-resolution magic angle spinning magnetic resonance spectroscopy (HR-MAS MRS) were associated with recurrence following radical prostatectomy.

Methods:

We performed a retrospective ex vivo study using HR-MAS MRS on tissue samples from 110 radical prostatectomy specimens obtained from three different Norwegian cohorts collected between 2002 and 2010. At the time of analysis, 50 patients had experienced prostate cancer recurrence. Associations between metabolites, clinicopathological variables, and recurrence-free survival were evaluated using Cox proportional hazards regression modelling, Kaplan–Meier survival analyses and concordance index (C-index).

Results:

High intratumoural spermine and citrate concentrations were associated with longer recurrence-free survival, whereas high (total-choline+creatine)/spermine (tChoCre/Spm) and higher (total-choline+creatine)/citrate (tChoCre/Cit) ratios were associated with shorter time to recurrence. Spermine concentration and tChoCre/Spm were independently associated with recurrence in multivariate Cox proportional hazards modelling after adjusting for clinically relevant risk factors (C-index: 0.769; HR: 0.72; P=0.016 and C-index: 0.765; HR: 1.43; P=0.014, respectively).

Conclusions:

Spermine concentration and tChoCre/Spm ratio in prostatectomy specimens were independent prognostic markers of recurrence. These metabolites can be noninvasively measured in vivo and may thus offer predictive value to establish preoperative risk assessment nomograms.

Abstract 2210: Scavenging for lethal prostate cancer biomarkers in FFPE tissue

The aim of this study was to identify protein biomarkers that can be used to stratify indolent and aggressive prostate cancer using formalin-fixed paraffin-embedded tissue (FFPE) from radical prostatectomy specimens. The protein expression profiles of benign and malign samples from 23 patients, who had either died of prostate cancer or were alive 10 years after diagnosis, were determined using an Easy nLC1000 Nano-LC system connected to a quadrupole-Orbitrap (Q Exactive) mass spectrometer equipped with a nanoelectrospray ion source. The generated MS raw files were submitted to MaxQuant software for protein identification. Differential expression of LFQ-normalized intensities was tested by Cox proportional hazards modeling and LASSO (least absolute shrinkage and selection operator) regression analysis within the R software environment. The label free Orbitrap analysis identified 3523 unique proteins from the FFPE tissue samples. LASSO of protein expression profiles of indolent and aggressive prostate cancer tissue samples identified ten proteins which could stratify the groups. Seven of the proteins were significantly correlated with time to prostate cancer specific mortality in Cox proportional hazards modeling (p-value < 0.05). The selected proteins were found to be linked to NFkappaB signaling, cell structure, translation and metabolic pathways. Finally, proteins capable of distinguishing benign from malignant prostate tissue were identified by LASSO, and 22 of these were significantly different between the groups (Bonferroni-adjusted p-value < 0.05). Selected candidate biomarkers are currently being validated by immunohistochemical analyses of 535 radical prostatectomy specimens from two independent Norwegian cohorts with long follow-up time.

Citation Format: Håkon Ramberg, Peder R. Braadland, Maria E. Stensland, Mehrdad Rakaee, Ståle Nygård, Olov Øgren, Viktor Berge, Aud Svindland, Elin Richardsson, Gustavo A. de Souza, Sigve Andersen, Kristin A. Taskén. Scavenging for lethal prostate cancer biomarkers in FFPE tissue [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2210. doi:10.1158/1538-7445.AM2017-2210

Tomato-based randomized controlled trial in prostate cancer patients: Effect on PSA

BACKGROUND & AIMS

The effect of lycopene-containing foods in prostate cancer development remains undetermined. We tested whether a lycopene-rich tomato intervention could reduce the levels of prostate specific antigen (PSA) in prostate cancer patients.

METHODS

Prior to their curative treatment, 79 patients with prostate cancer were randomized to a nutritional intervention with either 1) tomato products containing 30 mg lycopene per day; 2) tomato products plus selenium, omega-3 fatty acids, soy isoflavones, grape/pomegranate juice, and green/black tea (tomato-plus); or 3) control diet for 3 weeks.

RESULTS

The main analysis, which included patients in all risk categories, did not reveal differences in changes of PSA-values between the intervention and control groups. Post-hoc, exploratory analyses within intermediate risk (n = 41) patients based on tumor classification and Gleason score post-surgery, revealed that median PSA decreased significantly in the tomato group as compared to controls (-2.9% and +6.5% respectively, p = 0.016). In separate post-hoc analyses, we observed that median PSA-values decreased by 1% in patients with the highest increases in plasma lycopene, selenium and C20:5 n-3 fatty acid, compared to an 8.5% increase in the patients with the lowest increase in lycopene, selenium and C20:5 n-3 fatty acid (p = 0.003). Also, PSA decreased in patients with the highest increase in lycopene alone (p = 0.009).

CONCLUSIONS

Three week nutritional interventions with tomato-products alone or in combination with selenium and n-3 fatty acids lower PSA in patients with non-metastatic prostate cancer. Our observation suggests that the effect may depend on both aggressiveness of the disease and the blood levels of lycopene, selenium and omega-3 fatty acids.

The star chart to Ta bladder cancer: an unsophisticated analysis of two-dimensional gel electrophoresis proteome maps

OBJECTIVE

To explore the use of two-dimensional gel electrophoresis (2DE) for analysing the proteome of clinically relevant tissue samples such as biopsies from transurethral resections of the bladder (TURB), by generating a Ta proteome map, possibly identifying technical or biological artefacts, and searching for biological subgroups associated with clinical data.

MATERIAL AND METHODS

Biopsies from 23 patients were homogenized and the protein content was separated by 2DE. The gels were silver stained and scanned, and the resulting pictures were analysed for similarities in the spot pattern.

RESULTS

A majority of 18 patients displayed a consistent protein expression profile and a Ta proteome map was constructed by averaging the grey value of each pixel in all 18 pictures. Spot detection was performed on a project proteome map (based on all 23 samples) and resulted in 1583 detected spots. 416 of these which were positively detected in all 18 "Ta-map" samples. Three patients displayed a pattern with some marked alterations to the majority profile, possibly artefacts of yet unknown heredity. One patient revealed a protein pattern deemed to constitute a separate group, later revealed as a blinded control from a T4 tumour. Only one sample was sparse in protein spots, probably containing mostly blood owing to inadequate sampling. No biological subgroups associated with clinical data were identified.

CONCLUSIONS

A Ta proteome map was successfully created from TURB samples. Deviating protein expression profiles were identified, indicating a future potential to reveal biologically relevant subgroups in this or other stages of urothelial cell carcinomas.

Expression of Serotonin Receptors 2B and 4 in Human Prostate Cancer Tissue and Effects of Their Antagonists on Prostate Cancer Cell Lines

OBJECTIVES

Overexpression of receptors to neuroendocrine (NE) cell products has been suggested to contribute to development of hormone-refractory prostate cancer (HRPC). In this study, we evaluated the expression of 5-HTR2B and 5-HTR4 in HRPC, and the effects of their antagonist on PC cell line growth.

METHODS

Proteins and mRNA expression was determined by immunohistochemistry, western blot and RT-PCR. Growth inhibition of PC cell lines was determined in vitro using ELISA-BrdU proliferation assay and cell cycle was evaluated by flow cytometry.

RESULTS

Immunostaining of 5-HTR2B was observed in low-grade and high-grade tumours, PIN and BPH cells, and in vascular endothelial cells, whereas 5-HTR4 was found predominantly in high-grade tumours. This result was confirmed by western blot analysis. At the mRNA level, 5-HTR4 mRNA was expressed in DU145 and LNCaP cells. Antagonists to both receptor subtypes inhibited proliferation of PC cells in a dose-dependent manner.

CONCLUSIONS

The present result indicate that 5-HTRs are present at various tumour stages and that antagonists to these receptors can inhibit the proliferative activity of androgen-independent PC cell lines.

Protein kinase A-anchoring protein AKAP95 interacts with MCM2, a regulator of DNA replication

Protein kinase A (PKA)-anchoring protein AKAP95 is localized to the nucleus in interphase, where it primarily associates with the nuclear matrix. A yeast two-hybrid screen for AKAP95 interaction partners identified the minichromosome maintenance (MCM) 2 protein, a component of the pre-replication complex. AKAP95-MCM2 interaction was mapped to residues 1-195 of AKAP95 and corroborated by glutathione S-transferase precipitation and immunoprecipitation from chromatin. Disruption of AKAP95-MCM2 interaction with an AKAP95-(1-195) peptide within HeLa cell nuclei abolishes initiation of DNA replication in G1 phase and the elongation phase of replication in vitro without affecting global nuclear organization or import. Disruption of the C-terminal zinc finger of AKAP95 reduces efficiency of replication initiation. Disruption of the PKA-binding domain does not impair replication in G1- or S-phase nuclei, whereas a PKA inhibitor affects the initiation but not the elongation phase of replication. Depleting AKAP95 from nuclei partially depletes MCM2 and abolishes replication. Recombinant AKAP95 restores intranuclear MCM2 and replication in a dose-dependent manner. Our results suggest a role of AKAP95 in DNA replication by providing a scaffold for MCM2.

Mechanisms of FOXC2- and FOXD1-mediated regulation of the RI alpha subunit of cAMP-dependent protein kinase include release of transcriptional repression and activation by protein kinase B alpha and cAMP

We have reported recently that mice overexpressing the forkhead/winged helix transcription factor FOXC2 are lean and show increased responsiveness to insulin due to sensitization of the beta-adrenergic cAMP-PKA(+) pathway and increased levels of the RI alpha subunit of cAMP-dependent protein kinase (PKA) (Cederberg, A., Grønning, L. M., Ahren, B., Taskén, K., Carlsson, P., and Enerbäck, S. (2001) Cell 106, 563-573). In this present study, we reveal that FOXC2 and a related factor, FOXD1, specifically activate the 1b promoter of the RI alpha gene in adipocytes and testicular Sertoli cells, respectively. By deletional mapping, we discovered two different mechanisms by which the Fox proteins activated expression from the RI alpha 1b promoter. In 3T3-L1 adipocytes, an upstream region represses promoter activity under basal conditions. Bandshift experiments indicate that overexpression of FOXC2 promotes the release of a potential repressor from this region. In Sertoli cells, sequences downstream of the transcription start sites mediate the activating effect of FOXD1, and protein kinase B alpha/Akt1 strongly induces this effect. Furthermore, we show that an inactive FOXD1 mutant lowers the cAMP-mediated induction of the RI alpha 1b reporter construct. In summary, winged helix transcription factors of the FOXC/FOXD families function as regulators of the RI alpha subunit of PKA and may integrate hormonal signals acting through protein kinase B and cAMP in a cell-specific manner.

Distinct but overlapping domains of AKAP95 are implicated in chromosome condensation and condensin targeting

A-kinase (or PKA)-anchoring protein AKAP95 is a zinc-finger protein implicated in mitotic chromosome condensation by acting as a targeting molecule for the condensin complex. We have identified determinants of chromatin-binding, condensin-targeting and chromosome-condensation activities of AKAP95. Binding of AKAP95 to chromatin is conferred by residues 387-450 and requires zinc finger ZF1. Residues 525-569 are essential for condensation of AKAP95-free chromatin and condensin recruitment to chromosomes. Mutation of either zinc finger of AKAP95 abolishes condensation. However, ZF1 is dispensable for condensin targeting, whereas the C-terminal ZF2 is required. AKAP95 interacts with Xenopus XCAP-H condensin subunit in vitro and in vivo but not with the human hCAP-D2 subunit. The data illustrate the involvement of overlapping, but distinct, domains of AKAP95 for condensin recruitment and chromosome condensation and argue for a key role of ZF1 in chromosome condensation and ZF2 in condensin targeting. Moreover, condensin recruitment to chromatin is not sufficient to promote condensation.

Cyclic AMP regulates expression of the RI alpha subunit of cAMP-dependent protein kinase through an alternatively spliced 5' UTR

The present study examines novel mechanisms that regulate levels of the RI alpha subunit of cAMP-dependent protein kinase. We found that RI alpha protein is induced threefold by 8-(4-chlorophenyl)thio-cAMP in hormone responsive rat Sertoli cells, while total RI alpha mRNA is not correspondingly induced. Two RI alpha mRNA isoforms with different 5' untranslated sequences (RI alpha 1a and RI alpha 1b) are produced from the RI alpha gene in Sertoli cells. Deletion/mutation analysis of the cAMP-response-element-containing promoter upstream of the RI alpha exon 1b revealed that while mutation of the cAMP response element had no effects on cAMP-mediated induction, a 73-bp region of the RI alpha exon 1b itself conferred a fivefold to eightfold induction of reporter activity to homologous and heterologous promoters. The responsiveness of this region was dependent on a sense orientation downstream of the promoter start sites and had no effect on reporter mRNA, indicating that the cAMP-mediated induction occurs at the post-transcriptional level. Modeling of the RI alpha 1b 5' UTR secondary structure revealed a 5' CAP-proximal, strong stem-loop presenting an element similar to multiple start-site element downstream-1 (GCTCGG) in the loop region. RNA-EMSAs performed with the labeled RI alpha 1b 5' UTR showed stabilization of a protein/RNA complex in extracts from 8-(4-chlorophenyl)thio-cAMP stimulated Sertoli cells. This complex was abolished by mutation of the multiple start-site element downstream-1-like element. Our findings indicate that there is a cAMP-mediated induction of RI alpha expression at the post-transcriptional level, dependent on the 5' UTR of RI alpha 1b mRNA.

Phosphodiesterase 4D and protein kinase a type II constitute a signaling unit in the centrosomal area

The mediation of cAMP effects by specific pools of protein kinase A (PKA) targeted to distinct subcellular domains raises the question of how inactivation of the cAMP signal is achieved locally and whether similar targeting of phosphodiesterases (PDEs) to sites of cAMP/PKA action could be observed. Here, we demonstrate that Sertoli cells of the testis contain an insoluble PDE4D3 isoform, which is shown by immunofluorescence to target to centrosomes. Staining of PDE4D and PKA shows co-localization of PDE4D with PKA-RIIalpha and RIIbeta in the centrosomal region. Co-precipitation of RII subunits and PDE4D3 from cytoskeletal extracts indicates a physical association of the two proteins. Distribution of PDE4D overlaps with that of the centrosomal PKA-anchoring protein, AKAP450, and AKAP450, PDE4D3, and PKA-RIIalpha co-immunoprecipitate. Finally, both PDE4D3 and PKA co-precipitate with a soluble fragment of AKAP450 encompassing amino acids 1710 to 2872 when co-expressed in 293T cells. Thus, a centrosomal complex that includes PDE4D and PKA constitutes a novel signaling unit that may provide accurate spatio-temporal modulation of cAMP signals.

Novel alternatively spliced mRNA (1c) of the protein kinase A RIα subunit is implicated in haploid germ cell specific expression

By using 5' RACE on rat testis cDNA we identified three alternatively spliced mRNAs of the RIalpha subunit of cAMP-dependent protein kinase that differed in their 5' untranslated regions. Two of these 5'-regions showed similarity with the human RIalpha exons 1a and 1b, while the third (1c) constituted a novel mRNA splice variant. Northern blot analysis showed that the 1c mRNA was specifically expressed in testis and only in postmeiotic germ cells. In contrast, the RIalpha 1b and RIalpha 1a mRNAs were present both in premeiotic germ cells and somatic cells of the testis, and the expression of both RIalpha 1a and 1b mRNAs were stimulated by cAMP in Sertoli cells. In sperm, the RIalpha protein was expressed after meiosis, and targeted to various subcellular structures via anchoring proteins. The RIalpha 1c haploid-specific mRNA, therefore, may be important for the regulation of RIalpha expression in sperm.

Regulation of tissue inhibitor of metalloproteinases-1 in rat Sertoli cells: induction by germ cell residual bodies, interleukin-1alpha, and second messengers

In the testis, FSH has been shown to induce the expression and secretion of tissue inhibitor of metalloproteinases-1 (TIMP-1) from Sertoli cells in vitro. This study was performed to elucidate further the cellular origin of testicular TIMP-1 and its expression by hormonal and paracrine factors. This is the first report on the expression of testicular TIMP-1 in vivo. TIMP-1 mRNA in whole testis was decreased after hypophysectomy and strongly increased by the injection of FSH-S17 to hypophysectomized rats. Primary cultures of both peritubular and Sertoli cells showed basal expression of TIMP-1 mRNA. In contrast, we were unable to detect TIMP-1 mRNA in Leydig cells, freshly isolated immature germ cells (primary spermatocytes and spermatids), or residual bodies. We further show that treatment of Sertoli cells with 8-(4-chlorophenyl)thio-cAMP (8-CPTcAMP) in combination with 12-O-tetradecanoylphorbol 13-acetate (TPA) or Ca(2+) inducers (calcium ionophore A23187 or thapsigargin) had additive (TPA) and synergistic effects (Ca(2+)) on the level of TIMP-1 mRNA and secreted protein. We also show that both the level of TIMP-1 mRNA and secreted protein from Sertoli cells were strongly increased by residual bodies, as well as by the cytokine interleukin-1alpha. TIMP-1 was not up-regulated by either 8-CPTcAMP or interleukin-1alpha in peritubular cells. In contrast to the regulated secretory fraction of TIMP-1, we also detected constitutively expressed immunoreactive TIMP-1 in the nucleus of Sertoli cells, suggesting a role of nuclear TIMP-1 in these cells. In conclusion, our data show that secretion of TIMP-1 from Sertoli cells is highly regulated by hormonal and local processes in the testis, indicating that TIMP-1 is of physiological importance during both testicular development and spermatogenesis.

Method of transfection affects the cAMP-mediated induction of the RIIbeta subunit of protein kinase A in Sertoli cells: inhibition of response by increase in intracellullar calcium

mRNA for the regulatory subunit RIIbeta of cAMP-dependent protein kinase is stimulated more than 50-fold by cAMP in primary cultures of rat Sertoli cells. We have previously shown that this induction involves regulation of transcriptional activation as well as mRNA stabilization. The rat RIIbeta gene contains no cAMP response element (CRE), and the induction of RIIbeta mRNA is slow and requires on-going protein synthesis. When a construct containing the 5'-flanking region of the RIIbeta gene upstream of a CAT reporter was transfected into Sertoli cells by the calcium phosphate method, low and variable responses to cAMP (three- to fivefold) were observed, whereas a 15- to 20-fold increase in reporter activity by cAMP was observed after lipofectamine transfection. Interestingly, when a vector containing CRE elements upstream of a reporter gene was transfected into Sertoli cells, the responses to cAMP were similar regardless of the transfection method used. We have also demonstrated that increased intracellular levels of calcium by A23187 and thapsigargin dramatically inhibit cAMP-mediated induction of RIIbeta mRNA, but not the mRNA for the CRE-containing RIalpha gene. Furthermore, decreased cAMP responsiveness of endogenous RIIbetamRNA (but not RIalpha) was also observed in calcium phosphate-transfected Sertoli cells but not in lipofectamine-transfected cells. Thus, calcium-mediated reduction in cAMP response appears to be a gene-specific phenomenon.

Calcium/phospholipid-dependent protein kinases in rat Sertoli cells: regulation of androgen receptor messenger ribonucleic acid

The possibility that Sertoli cell responses to testosterone are modulated by the calcium/phospholipid-dependent protein kinase (protein kinase C; PKC) was examined in rat Sertoli cells in culture. Both soluble and particulate cell fractions showed low constitutive phosphotransferase activity. Incubation with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA; 10(-7) M) was associated with a transient induction in both cell fractions of calcium/phosphatidylserine-dependent PKC activity, which was elevated from 15 min to 1 h. Consistent with this, mRNAs for the calcium/phospholipid-dependent isomeric forms of PKC (alpha, beta, and gamma) were detected. The expression levels of mRNAs for PKCalpha and PKCbeta were also up-regulated (2.5- to 3-fold) by TPA (10(-7) M), but these effects were much slower (peaking after 12 h) than those on phosphotransferase activity. In the presence of TPA (10(-7) M), expression of androgen receptor (AR) mRNA showed a transient time-dependent down-regulation ( approximately 70%), in which the nadir was reached after 6 h and baseline expression was again obtained after 12 h. The regulatory effect of PKC activation on AR mRNA was confirmed by the absence of response to a biologically inactive phorbol ester. A concentration-dependent decrease (half-maximal effect at approximately 10(-8) M TPA) of AR mRNA was also observed. These data suggest that Sertoli cell responses to testosterone may be inhibited by a transiently active PKC with a wide intracellular distribution.

Isoform-specific regulation of the CCAAT/enhancer-binding protein family of transcription factors by 3',5'-cyclic adenosine monophosphate in Sertoli cells

The C/EBP (CCAAT/enhancer-binding protein) family of transcription factors is important for differentiation, lipid biosynthesis, and metabolism. Here, we demonstrate for the first time the presence of C/EBP alpha, beta, delta, and zeta messenger RNA (mRNA) and protein in Sertoli cell primary cultures. Treatment with FSH or 8-CPTcAMP strongly induced C/EBP beta mRNA above basal levels with rapid and transient kinetics in Sertoli cell primary cultures as well as in whole testes from hypophysectomized rats. Whereas C/EBP beta mRNA was induced approximately 50-fold, C/EBP delta mRNA was induced 5- to 8-fold by cAMP in Sertoli cells. Messenger RNA for C/EBP beta and delta were induced by inhibition of protein synthesis with cycloheximide and cycloheximide acted synergistically with cAMP. Immunoblots with C/EBP antibodies demonstrated a strong induction of C/EBP beta, delta, and zeta by cAMP. Electrophoretic mobility shift analysis of nuclear proteins from cAMP-treated Sertoli cells using a C/EBP consensus oligonucleotide and antibodies revealed specific binding of C/EBP/DNA complexes, the majority of which were supershifted by C/EBP beta antibody. Transfections of Sertoli cells with a C/EBP reporter construct showed approximately 3-fold induction of reporter gene activity by cAMP. In contrast, the reporter gene vector with a mutated form of the C/EBP binding site, was almost unresponsive to cAMP in transfections of Sertoli cells. Furthermore, C/EBP beta expression increased the activities of two promoters known to be cAMP-responsive in Sertoli cells. Thus, the early induction of C/EBP isoforms by cAMP may play a role in FSH-dependent regulation of late response genes in Sertoli cells.

Structure, function, and regulation of human cAMP-dependent protein kinases

A large number of hormones, neurotransmitters, and other signaling substances that bind to G-protein-coupled cell-surface receptors have their signals converge at one sole second messenger, cAMP. The question of how specificity can be maintained in a signal-transduction system in which many extracellular signals leading to a vast array of intracellular responses are all mediated through one second-messenger system has been the subject of thorough investigation and a great deal of speculation. An increasing number of cAK isozymes, consisting of homo- or heterodimers of R subunits (RIalpha, RIbeta, RIIalpha, RIIbeta) with associated catalytic subunits (C alpha, Cbeta, Cgamma), may, at least in part, explain this specificity. The various cAK isozymes display distinct biochemical properties, and the heterogeneous subunits of cAK reveal cell-specific expression and differential regulation at the level of gene transcription, mRNA stability, and protein stability in response to a wide range of hormones and other signaling substances. The existence of a number of anchoring proteins specific to either RIIalpha or RIIbeta, and which localize cAKII isozymes toward distinct substrates at defined subcellular loci, strongly supports the idea that specific functions can be assigned to the various cAK isozymes. The demonstration that selective activation of cAKI is necessary and sufficient for cAMP-mediated inhibition of T-cell proliferation, and the observation that T-cell activation is associated with redistribution and colocalization of cAKI to the TCR, is also compatible with the notion of isozyme-specific effects.

Characterization of the 5'-flanking region of the gene for the cAMP-inducible protein kinase A subunit, RIIbeta, in Sertoli cells

Activation of cyclic AMP-dependent protein kinases (protein kinase A, PKA) by gonadotropins and cyclic AMP (cAMP) plays an important role in the regulation of testicular functions. A regulatory subunit, RIIbeta, of PKA is transcriptionally induced in rat Sertoli cells in response to treatment with cAMP. The present study addresses regulatory mechanisms leading to increased transcription of the rat RIIbeta gene. We have localized a footprint which overlaps one of the major transcription initiation sites in the basal promoter (-293 to -123). One of the proteins binding this sequence belongs to the NF-1 family of transcription factors. We also observed binding to a basic helix-loop-helix (bHLH) response element. Furthermore, transfection studies of various 5'-deletions of the rat RIIbeta gene in primary cultures of rat Sertoli cells and in peritubular cells revealed the presence of an upstream region (-723 to -395, cAMP-responsive region) inhibiting basal expression from the rat RIIbeta gene only in Sertoli cells. This region was found to enhance cAMP responsiveness in Sertoli cells but not in peritubular cells. Interactions with downstream elements seemed to be important for the function of the cAMP-responsive region. Although some short stretches reveal homology to the cAMP-responsive regions of other slowly cAMP-responding genes, and an AP-1-like element is present, no strong resemblance to any known regulatory element responsive to cAMP is found.

Regulation of protein kinase A subunits by cyclic adenosine 3',5'-monophosphate in a mouse Sertoli cell line (MSC-1): induction of RII beta messenger ribonucleic acid is independent of continuous protein synthesis

We report the basal and cAMP-regulated expression of protein kinase A (PKA) subunits in a mouse Sertoli cell line (MSC-1). Of the PKA subunits expressed by these cells (RI alpha, RII alpha, RII beta, C alpha, C beta), only RII beta was regulated by cAMP. An approximately 8-fold induction of RII beta mRNA and a 3-fold induction of RII beta protein was observed during 48 h of cAMP-stimulation. This cAMP-mediated RII beta mRNA induction, reaching maximal levels after approximately 12 h, did not require ongoing protein synthesis. Fairly rapid decay of maximally induced RII beta mRNA was observed after removal of cAMP (t1/2 approximately 5 h). Further, ongoing transcription and translation were necessary for rapid degradation of RII beta mRNA. Thus, the MSC-1 cells expressed all the PKA subunits present in primary cultures of Sertoli cells and responded to cAMP with increased levels of RII beta at both mRNA and protein levels. Although the nature of some of these responses distinguished the observations in MSC-1 cells from previously described responses in primary cultures, these cells may prove to be useful in future studies addressing cAMP-mediated gene regulation.

The alpha-subunit mRNAs for Gs and Go2 are differentially regulated by protein kinase A and protein kinase C in rat Sertoli cells

In the present study, we have examined regulatory effects of protein kinase A and protein kinase C activation by 8-CPTcAMP and TPA, respectively, on mRNAs for various G protein alpha-subunits and corresponding immunoreactive proteins in rat Sertoli cells. Gs alpha and Go alpha mRNA levels were transiently increased 1.5-fold and 4-fold, respectively, by 8-CPTcAMP in cultured Sertoli cells. This up-regulation of mRNAs for Gs alpha and Go alpha was also observed when Sertoli cells were incubated in the presence of FSH. When protein synthesis was inhibited by cycloheximide, the cAMP-mediated stimulation of Gs alpha mRNA was abolished, whereas Go alpha mRNA was superinduced to a 50- to 100-fold higher level than basal. Activation of protein kinase C with TPA had a strong, synergistic effect on cAMP-mediated stimulation of Gs alpha mRNA, whereas the cAMP-mediated stimulation of Go alpha mRNA was completely blocked. Surprisingly, changes in mRNA levels were not accompanied by any alterations in the levels of immunoreactive Gs alpha and Go alpha proteins.

Reciprocal regulation of mRNA and protein for subunits of cAMP-dependent protein kinase (RI alpha and C alpha) by cAMP in a neoplastic B cell line (Reh)

The present study examines the activity, levels of expression and regulation of cAMP-dependent protein kinase subunits during cAMP-mediated inhibition of Reh cell proliferation. Human Reh cells express mRNAs for the RI alpha and C alpha subunits of cAK at high levels and are practically devoid of cAMP-dependent protein kinase type II. Treatment with isoproterenol, forskolin, or a cAMP analog increased RI alpha mRNA in a time- and concentration-dependent manner (maximal, 4-fold, at 4-8 h). Messenger RNA for C alpha was also stimulated by cAMP, although with slower kinetics (maximal, 2-fold, at 16-24 h). Nuclear run-on assays showed a 2-fold increase in RI alpha gene transcription, whereas that of C alpha was unchanged. In spite of the stimulatory effects of cAMP on mRNAs for both RI alpha and C alpha, phosphotransferase activity and specific [3H]cAMP binding decreased rapidly after treatment with either cAMP or forskolin. Interestingly, the decrease in R and C activity preceded the increase in RI alpha and C alpha mRNA levels, raising the question whether increased mRNA levels may be secondary to the decrease in RI alpha or C alpha protein. The finding that the protein synthesis inhibitor cycloheximide gave changes in RI alpha and C alpha mRNA similar to cAMP and that co-treatment with cycloheximide and cAMP resulted in additive effects tend to support this notion.

Protein kinase C activation and positive and negative agonist regulation of 3',5'-cyclic adenosine monophosphate levels in cultured rat Sertoli cells

The present study examines the effects of 12-O-tetradecanoylphorbol-13-acetate (TPA) on agonist-regulated 3',5'-cyclic adenosine monophosphate (cAMP) formation and cAMP-mediated effects in cultured Sertoli cells from immature rats. Concentration-dependent stimulation of cAMP levels by follicle-stimulating hormone (FSH) was inhibited dramatically by the coaddition of 100 nmol/l TPA, which exerted a similar inhibition of glucagon- and isoproterenol-stimulated cAMP production. These results show that protein kinase C (PKC) activation by TPA attenuates Gs-protein-mediated agonist activation of cAMP production. (-)-N6(R)-Phenylisopropyladenosine (L-PIA), an A1-adenosine receptor agonist, inhibited cAMP stimulation by FSH in a concentration-dependent manner. When L-PIA was added in increasing concentrations simultaneously with 100 nmol/l TPA, the L-PIA still inhibited FSH-stimulated cAMP production in a concentration-dependent manner. In the presence of TPA, the half-inhibitory concentration (IC50) for L-PIA inhibition of cAMP formation was reduced by more than one order of magnitude, indicating that PKC activation by TPA increases the sensitivity of Sertoli cells to Gi-protein-mediated agonist inhibition of cAMP production. The inhibitory effects of TPA on FSH-stimulated cAMP production were still observed when cAMP phosphodiesterase activity was inhibited by 1 mmol/l methylisobutylxanthine or when the activity of G alpha i-protein was eliminated by pretreatment with 100 micrograms/l pertussis toxin. Taken together, the results indicate that PKC activation inhibits agonist-dependent stimulation of cAMP production by phosphorylation of components common to all the activating agonists used, and not via stimulation of G(i)-protein activity or degradation of cAMP by cAMP phosphodiesterase activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Half-lives of different sized mRNAs for the PKA subunit RI alpha are regulated differently in response to inhibition of transcription and translation

The RI alpha mRNA level is induced 3-5 times by FSH or cAMP analogs in primary cultures of rat Sertoli cells. In rat tissues, the RI alpha gene gives rise to three different mRNAs of different size: 3.2, 2.9 and 1.7 kb. In the present study we report that the 1.7 kb transcript has a shorter half-life than the two other mRNAs. In cells which had been pre-stimulated with a cAMP analog, inhibition of transcription stabilizes the two larger, but not the smaller sized RI alpha mRNA. However, in contrast, inhibition of protein synthesis stabilizes all the RI alpha mRNAs. Thus, degradation of various mRNAs coding for the same protein reveals different dependencies on transcription and translation.

Inhibitors of RNA and protein synthesis stabilize messenger RNA for the RII beta subunit of protein kinase A in different cellular compartments

Messenger RNA for RII beta is transiently induced (greater than 50-fold) by cAMP analogs in primary cultures of rat Sertoli cells. The induction is dependent on protein synthesis. We have previously shown that mRNA for RII beta is stabilized by cAMP, as well as inhibitors of transcription and translation. This indicated that rapid degradation of RII beta mRNA involved a protein with a rapid turnover and its corresponding mRNA. The two RNA synthesis inhibitors used in the present study stabilized both nuclear and cytoplasmic RII beta mRNA, whereas inhibition of protein synthesis stabilized RII beta mRNA in the cytoplasm only. These results indicate that only cytoplasmic degradation of RII beta mRNA is dependent on a protein with high turnover. In contrast, nuclear degradation appears to be dependent on an RNA with a short half-life, not involving protein synthesis.

Protein kinase C activation by 12-O-tetradecanoylphorbol 13-acetate modulates messenger ribonucleic acid levels for two of the regulatory subunits of 3',5'-cyclic adenosine monophosphate-dependent protein kinases (RII beta and RI alpha) via multiple and distinct mechanisms

Messenger RNAs (mRNA) for two of the regulatory subunits of cAMP-dependent protein kinases (PKA), RII beta and RI alpha, are transiently (maximal levels at 6 h) stimulated by 12-O-tetradecanoylphorbol 13-acetate (TPA) in cultured rat Sertoli cells in a time- and concentration-dependent manner. Whereas TPA (10(-7) M) stimulated RII beta mRNA 11 +/- 2.8 fold (mean +/- SEM), mRNA levels for RI alpha increased only 2.5 +/- 0.6-fold (mean +/- SEM). No effects of TPA on the other subunits of PKA (RII alpha, C alpha) were observed. TPA-dependent accumulation of mRNAs for RII beta and RI alpha was observed to the same extent in nucleus and cytoplasm. We have previously shown that mRNA levels for all the PKA subunits are increased by cAMP, particularly that of RII beta (greater than 50-fold). TPA modulated the stimulatory effects of cAMP on RII beta and RI alpha mRNAs in opposite directions. Whereas treatment with both 8-CPTcAMP and TPA gave an additive effect on RI alpha mRNA, TPA reduced the cAMP-dependent increase in RII beta mRNA. Although the mRNA for RII beta had returned to basal levels after 24 h of incubation with TPA, the presence of TPA still inhibited cAMP-dependent induction of mRNA for RII beta. In contrast, similar TPA treatment did not influence the subsequent cAMP-dependent stimulation of RI alpha mRNA. Preincubation with 8-CPTcAMP did not influence TPA-dependent stimulation of mRNAs for either RII beta or RI alpha. TPA induction of RII beta mRNA was completely blocked by cycloheximide (an inhibitor of protein synthesis), whereas that of RI alpha was not. The inhibitory effect of TPA on cAMP stimulation of RII beta mRNA was independent of ongoing protein synthesis. These results indicate that TPA induction of mRNAs for RI alpha and RII beta involves multiple and distinct mechanisms. The stimulatory effect of TPA on RI alpha mRNA levels and the inhibitory effect of TPA on cAMP-stimulated RII beta mRNA expression are probably mediated through stable factors, whereas proteins with rapid turnover or factors induced by TPA are involved in the stimulatory effect of TPA on RII beta mRNA.

Adenosine 3',5'-monophosphate-dependent stabilization of messenger ribonucleic acids (mRNAs) for protein kinase-A (PKA) subunits in rat Sertoli cells: rapid degradation of mRNAs for PKA subunits is dependent on ongoing RNA and protein synthesis

cAMP treatment of primary cultures of Sertoli cells is associated with a transient stimulatory effect on mRNA levels for various protein kinase-A (PKA) subunits. We have previously shown that the induction of mRNA for regulatory subunit II beta (RII beta) is due at least partly to transcriptional activation. In the present study we investigate possible regulatory effects of (Bu)2cAMP on the degradation of mRNAs for various PKA subunits in rat Sertoli cells. We demonstrate subunit specific differences in the decay of mRNAs for the various PKA subunits. When (Bu)2cAMP was removed from Sertoli cell cultures after 6 h of stimulation, there was a rapid decay of mRNAs for both RII beta and RI alpha (half-lives, approximately 3 h). In contrast, mRNA levels for RII alpha continued to increase. Removal of (Bu)2cAMP after a longer period of treatment revealed a similar decay of mRNAs for all of the PKA subunits, with half-lives of approximately 3 h. Incubation of Sertoli cells for 12 h with (Bu)2cAMP, followed by continued incubation in the absence and presence of (Bu)2cAMP as well as in the presence of actinomycin-D (an inhibitor of RNA synthesis), revealed (Bu)2cAMP mediated stabilization of mRNA for the RII beta subunit. Interestingly, actinomycin-D as such stabilized mRNAs for all PKA subunits. Similar treatment with cycloheximide (an inhibitor of protein synthesis) revealed distinct differences between the RI alpha and C alpha subunits vs. the RII subunits; cycloheximide reduced the decay of both RII beta and RII alpha mRNAs, whereas steady state levels of mRNAs for RI alpha and C alpha actually increased after cycloheximide treatment of previously (Bu)2cAMP-stimulated cultures. Cycloheximide treatment also increased basal levels of mRNAs for RI alpha and C alpha, whereas basal levels of RII beta and RII alpha mRNAs were not influenced. These studies indicate that the degradation of mRNAs for the various PKA subunits is subject to different regulation by (Bu)2cAMP, and that ongoing RNA and protein synthesis is required for rapid degradation of all PKA subunits.

Different mechanisms are involved in cAMP-mediated induction of mRNAs for subunits of cAMP-dependent protein kinases

The present study addresses possible mechanisms through which cAMP mediates its effects on mRNA levels for the subunits of protein kinase A (PKA) and the cellular protooncogene, c-fos. Messenger RNAs for the PKA subunits (RI alpha, RII alpha, RII beta, and C alpha) were regulated by cAMP with similar kinetics in Sertoli cells. However, effects of cAMP on the PKA mRNAs were slow compared to a well characterized cAMP responsive gene, c-fos. The magnitude of stimulation was dramatically different between the various PKA subunits, in that RII beta mRNA increased more than 50-fold while the mRNAs for the other subunits were induced only two to four times. Separation of nuclear and cytoplasmic RNA demonstrated that mRNAs for PKA subunits were stimulated to the same extent in these two cellular compartments. The more rapid induction of c-fos mRNA by cAMP, compared to the mRNA for RII beta, was also seen at the level of transcription. Maximal transcription rate for c-fos, RI alpha, and C alpha were observed after 30 min, whereas that for RII beta was increasing during the 2-h period examined. Transcriptional activation of the RI alpha gene also appeared faster than that for RII beta. When Sertoli cells were incubated with 8-(4-chlorophenylthio) cAMP and cycloheximide, a potent inhibitor of protein synthesis, we observed a super-induction of the mRNAs for c-fos (10-fold) and RI alpha (2-fold).(ABSTRACT TRUNCATED AT 250 WORDS)