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Metastatic castration-resistant prostate cancer (mCRPC) is an immunologically cold disease with dismal outcomes. Cryoablation destroys cancer tissue, releases tumor-associated antigens and creates a pro-inflammatory microenvironment, while dendritic cells (DCs) activate immune responses through processing of antigens. Immunotherapy combinations could enhance the anti-tumor efficacy. This open-label, single-arm, single-center phase I trial determined the safety and tolerability of combining cryoablation and autologous immature DC, without and with checkpoint inhibitors. Immune responses and clinical outcomes were evaluated. Patients with mCRPC, confirmed metastases and intact prostate gland were included. The first participants underwent prostate cryoablation with intratumoral injection of autologous DCs in a 3 + 3 design. In the second part, patients received cryoablation, the highest acceptable DC dose, and checkpoint inhibition with either ipilimumab or pembrolizumab. Sequentially collected information on adverse events, quality of life, blood values and images were analyzed by standard descriptive statistics. Neither dose-limiting toxicities nor adverse events > grade 3 were observed in the 18 participants. Results indicate antitumor activity through altered T cell receptor repertoires, and 33% durable (> 46 weeks) clinical benefit with median 40.7 months overall survival. Post-treatment pain and fatigue were associated with circulating tumor cell (CTC) presence at inclusion, while CTC responses correlated with clinical outcomes. This trial demonstrates that cryoimmunotherapy in mCRPC is safe and well tolerated, also for the highest DC dose (2.0 × 108) combined with checkpoint inhibitors. Further studies focusing on the biologic indications of antitumor activity and immune system activation could be considered through a phase II trial focusing on treatment responses and immunologic biomarkers.

Prostate cancer (PCa) often recurs as incurable castration‐resistant prostate cancer (CRPC) after the failure of androgen deprivation therapy. CRPC development relies on androgen receptor (AR) signaling. The IL6/STAT3 pathway is also a key driver of CRPC. The crosstalk between IL6/STAT3 and the AR pathways provides opportunities to explore next‐generation agents to treat PCa. Through screening of around 600 natural compounds in our newly established prostate tumorigenesis model, potential STAT3 signaling inhibitors were found and additionally examined for effects on AR signaling. The small molecular compound 154 exhibited dual effects on IL6/STAT3 and AR pathways. We show here that compound 154 inhibits AR and STAT3 transcriptional activity, reduces the expression of phosphorylation of STAT3 (Y705) and downregulates the mRNA levels of AR target genes. Compound 154 also inhibits protein expression of AR and AR splice variants (ARv567es and AR‐V7) without altering AR mRNA levels. Compound 154 binds to AR directly, but not to STAT3 and is identified as an antagonist of the AR amino‐terminal domain (NTD) by disrupting protein‐protein interactions between STAT3 and the AR NTD. Moreover, compound 154 does not reduce AR nuclear translocation. Compound 154 possesses the potential to become a leading compound in novel therapies against CRPC.

Human prostate cancer is initiated in a benign prostate epithelial cell which gains the potential to progress to metastatic disease. The exact cell of origin of prostate cancer has been debated in recent years based upon different models. Primary prostate epithelial cells have restricted life-spans in culture, but can be immortalized. Prostate cancer cell lines have been difficult to establish and new ones are desirable. Attempts to transform benign prostate epithelial cells in vitro have proved difficult without the use of strong carcinogens or oncogenes in processes not likely to mimic closely carcinogenesis in the aging human prostate. Models of epithelial-to-mesenchymal transition (EMT) and cancer stem cells in prostate carcinogenesis have become available, and advances in three-dimensional organoid culture technology represent a breakthrough in prostate cancer research. Organoids may recapitulate multiple features of prostate cancer and have the potential to replace costly and laborious animal experiments. Still, animal models are needed to investigate and validate molecular mechanisms and to develop therapeutic principles in the pipeline between in vitro experiments and clinical applications. Although mice represent the most common experimental animal in prostate cancer research, species like rat, dog, and zebrafish may have advantages depending upon the hypothesis or question. Animal models can generally be categorized into spontaneous or induced development of cancer, immunodeficient animals with xenografts, and genetically engineered animals. In prostate cancer, neuroendocrine differentiation and bone metastases are prevalent in the final stages of cancer progression and animal models that recapitulate these processes are available.

Oncogenic mutations of the Wnt (wingless)/β-catenin pathway are frequently observed in major cancer types. Thus far, however, no therapeutic agent targeting Wnt/β-catenin signaling is available for clinical use. Here we demonstrate that axitinib, a clinically approved drug, strikingly blocks Wnt/β-catenin signaling in cancer cells, zebrafish, and Apc(min/+) mice. Notably, axitinib dramatically induces Wnt asymmetry and nonrandom DNA segregation in cancer cells by promoting nuclear β-catenin degradation independent of the GSK3β (glycogen synthase kinase3β)/APC (adenomatous polyposis coli) complex. Using a DARTS (drug affinity-responsive target stability) assay coupled to 2D-DIGE (2D difference in gel electrophoresis) and mass spectrometry, we have identified the E3 ubiquitin ligase SHPRH (SNF2, histone-linker, PHD and RING finger domain-containing helicase) as the direct target of axitinib in blocking Wnt/β-catenin signaling. Treatment with axitinib stabilizes SHPRH and thereby increases the ubiquitination and degradation of β-catenin. Our findings suggest a previously unreported mechanism of nuclear β-catenin regulation and indicate that axitinib, a clinically approved drug, would provide therapeutic benefits for cancer patients with aberrant nuclear β-catenin activation.

Wnt (wingless)/β-catenin signaling is critical for tumor progression and is frequently activated in colorectal cancer as a result of the mutation of adenomatous polyposis coli (APC); however, therapeutic agents targeting this pathway for clinical use are lacking. Here we report that nitazoxanide (NTZ), a clinically approved antiparasitic drug, efficiently inhibits Wnt signaling independent of APC. Using chemoproteomic approaches, we have identified peptidyl arginine deiminase 2 (PAD2) as the functional target of NTZ in Wnt inhibition. By targeting PAD2, NTZ increased the deamination (citrullination) and turnover of β-catenin in colon cancer cells. Replacement of arginine residues disrupted the transcriptional activity, and NTZ induced degradation of β-catenin. In Wnt-activated colon cancer cells, knockout of either PAD2 or β-catenin substantially increased resistance to NTZ treatment. Our data highlight the potential of NTZ as a modulator of β-catenin citrullination for the treatment of cancer patients with Wnt pathway mutations.

Background Expression of the androgen receptor (AR) is associated with androgen-dependent proliferation arrest and terminal differentiation of normal prostate epithelial cells. Additionally, activation of the AR is required for survival of benign luminal epithelial cells and primary cancer cells, thus androgen deprivation therapy (ADT) leads to apoptosis in both benign and cancerous tissue. Escape from ADT is known as castration-resistant prostate cancer (CRPC). In the course of CRPC development the AR typically switches from being a cell-intrinsic inhibitor of normal prostate epithelial cell proliferation to becoming an oncogene that is critical for prostate cancer cell proliferation. A clearer understanding of the context dependent activation of the AR and its target genes is therefore desirable. Methods Immortalized human prostate basal epithelial EP156T cells and progeny cells that underwent epithelial to mesenchymal transition (EMT), primary prostate epithelial cells (PrECs) and prostate cancer cell lines LNCaP, VCaP and 22Rv1 were used to examine context dependent restriction and activation of the AR and classical target genes, such as KLK3. Genome-wide gene expression analyses and single cell protein analyses were applied to study the effect of different contexts. Results A variety of growth conditions were tested and found unable to activate AR expression and transcription of classical androgen-dependent AR target genes, such as KLK3, in prostate epithelial cells with basal cell features or in mesenchymal type prostate cells. The restriction of androgen- and AR-dependent transcription of classical target genes in prostate basal epithelial cells was at the level of AR expression. Exogenous AR expression was sufficient for androgen-dependent transcription of AR target genes in prostate basal epithelial cells, but did not exert a positive feedback on endogenous AR expression. Treatment of basal prostate epithelial cells with inhibitors of epigenetic gene silencing was not efficient in inducing androgen-dependent transcription of AR target genes, suggesting the importance of missing cofactor(s). Conclusions Regulatory mechanisms of AR and androgen-dependent AR target gene transcription are insufficiently understood and may be critical for prostate cancer initiation, progression and escape from standard therapy. The present model is useful for the study of context dependent activation of the AR and its transcriptome. Electronic supplementary material The online version of this article (doi:10.1186/s12885-016-2453-4) contains supplementary material, which is available to authorized users.

Epithelial to mesenchymal transition (EMT) is pivotal in tumor metastasis. Our previous work reported an EMT model based on primary prostate epithelial cells (EP156T) which gave rise to cells with mesenchymal phenotype (EPT1) without malignant transformation. To promote prostate cell transformation, cells were maintained in saturation density cultures to select for cells overriding quiescence. Foci formed repeatedly following around 8 weeks in confluent EPT1 monolayers. Only later passage EPT1, but not EP156T cells of any passage, could form foci. Cells isolated from the foci were named EPT2 and formed robust colonies in soft agar, a malignant feature present neither in EP156T nor in EPT1 cells. EPT2 cells showed additional malignant traits in vitro, including higher ability to proliferate following confluence, higher resistance to apoptosis and lower dependence on exogenous growth factors than EP156T and EPT1 cells. Microarray profiling identified gene sets, many of which belong to cell junction modules, that changed expression from EP156T to EPT1 cells and continued to change from EPT1 to EPT2 cells. Our findings provide a novel stepwise cell culture model in which EMT emerges independently of transformation and is associated with subsequent accumulation of malignant features in prostate cells. Reprogramming of cell junction modules is involved in both steps.

Interim analysis data are presented for 13 patients with metastatic castration resistant prostate cancer treated with dendritic cell based cryoimmunotherapy (CryoIT) and at least three months follow-up (FU). In CryoIT autologous immature dendritic cells (iDCs) mature in cryoablated tumor tissue and engulf tumor associated antigens and thereafter migrate to lymph nodes to instruct systemic immune attacks on heterogenous cancer cells. Primary endpoint of the trial is to investigate safety of CryoIT while secondary aims include clinical, radiological and immunological responses to treatment. Adverse events (AEs) and blood analyses were registered at all visits and imaging performed before and three months post-treatment. Norwegian regulatory authorities have approved the study. CryoIT of the prostate was performed as a freeze-thaw process under anesthesia and autologous iDCs injected after last thawing cycle. Radiologic responses according to RECISTv1.1 could categorize participants into either Group 1; stable disease (n=5) or Group 2; progressive cancer (n=4). Three patients showed mixed response and one had no follow-up imaging. Hematologic and immunologic values were evaluated according to response group. To identify peripheral blood leukocyte subsets and circulating tumor cells (CTCs), ultradeep T-cell receptor (TCR) β-chain sequences of complementarity-determining region 3, we utilized flow / mass cytometry, Cellsearch System, and TCRSafe Technology, respectively. At inclusion median age was 69 (62-73) years, BMI 25.9 (25-35), ECOG score 0 (0-1) and median PSA 8 (5-11). Group 2 demonstrated higher PSA (p=0.03), median 3.9 (IQR 2.7-6.8) and 74.6 (IQR 47.4-99.0) for Group 1 and Group 2, respectively. In total, 13 possible iDC-related AEs were reported by 10 individuals, whereof one severe and 12 mild-to-moderate, with urinary retention in seven subjects. All but one resolved by use of indwelling urinary catheter for median 8 (1-40) days. Participants with high CTC numbers (>5) before therapy had higher rates of progression, moderate pre-treatment CTC counts (3-5) decreased and no patient acquired CTCs after therapy. Ultradeep TCR-sequencing showed more prevalent and higher expression (>5-fold) of new TCR clonotypes 2-6 weeks after treatment in Group 1. The treatment seems safe and well tolerated. Higher PSA indicates more advanced disease at baseline for Group 2. The data indicate immune responses to treatment with higher increases in TCR clonotypes in radiologic stable disease. Clinical trial ID: NCT02423928. Citation Format: Liv Cecilie V. Thomsen, Alfred Honorè, Bjarte Almås, Lars A. Reisæter, Jannicke Frugård, Einar K. Kristoffersen, Guro Melve, Torjan Haslerud, Jarle Rørvik, Martin Biermann, Svein Inge Helle, Gunnar Kvalheim, Waqas Azeem, Jan Roger Olsen, Ole Johan Halvorsen, Lars Akslen, Duke K. Bahn, Klaus Pantel, Sabine Riethdorf, Haakon Ragde, Bjørn Tore Gjertsen, Anne M. Øyan, Karl-Henning Kalland, Christian Beisland. Dendritic cell based cryoimmunotherapy associates with clinical variables and changes in T-cell receptor expression in a prospective phase I trial of metastatic castration resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT066.

The androgen receptor (AR) transcription factor plays a key role in the development and progression of prostate cancer, as is evident from the efficacy of androgen-deprivation therapy, AR is also the most frequently mutated gene, in castration resistant prostate cancer (CRPC). AR has therefore become an even more attractive therapeutic target in aggressive and disseminated prostate cancer. To investigate mechanisms of AR and AR target gene activation in different subpopulations of prostate cancer cells, a toolkit of AR expressor and androgen response element (ARE) reporter vectors were developed. Three ARE reporter vectors were constructed with different ARE consensus sequences in promoters linked to either fluorescence or luciferase reporter genes in lentiviral vector backbones. Cell lines transduced with the different vectors expressed the reporters in an androgen-dependent way according to fluorescence microscopy, flow cytometry and multi-well fluorescent and luminescence assays. Interestingly, the background reporter activity in androgen-depleted medium was significantly higher in LNCaP cells compared to the prostate transit amplifying epithelial cell lines, EP156T-AR and 957E/hTERT-AR with exogenous AR. The androgen-induced signal to background was much higher in the latter benign prostate cells than in LNCaP cells. Androgen-independent nuclear localization of AR was seen in LNCaP cells and reduced ARE-signaling was seen following treatment with abiraterone, an androgen synthesis inhibitor. The ARE reporter activity was significantly stronger when stimulated by androgens than by β-estradiol, progesterone and dexamethasone in all tested cell types. Finally, no androgen-induced ARE reporter activity was observed in tumorigenic mesenchymal progeny cells of EP156T cells following epithelial to mesenchymal transition. This underscores the observation that expression of the classical luminal differentiation transcriptome is restricted in mesenchymal type cells with or without AR expression, and presence of androgen.

In recent years there has been a large increase in suggested controllers and observers for attitude determination and control of rigid bodies such as spacecraft. On the other hand there are very little experimental data where they are tested on actual flight hardware because of risk mitigation for commercial satellites and due to the high cost of launching pure experimental satellites. In this paper we propose a new Cube-Sat concept where the satellite is ascended using an ordinary weather balloon up to about 20 km altitude and then dropped. The attitude control system is then tested during the free-fall period of about five minutes where on board data is continuously transmitted to a nearby receiving station. The design is based on the requirement that the system shall be reusable. Thus it is equipped with a parachute and small balloons for buoyancy, and a GPS providing data to help locate the hardware after touchdown. As the weather balloons only cost some tens of dollars the presented system will provide a cheap and effective platform for excessive testing of advanced attitude control laws.

The transcription factor p63 is central for epithelial homeostasis and development. In our model of epithelial to mesenchymal transition (EMT) in human prostate cells, p63 was one of the most down-regulated transcription factors during EMT. We therefore investigated the role of p63 in EMT. Over-expression of the predominant epithelial isoform ΔNp63α in mesenchymal type cells of the model led to gain of several epithelial characteristics without resulting in a complete mesenchymal to epithelial transition (MET). This was corroborated by a reciprocal effect when p63 was knocked down in epithelial EP156T cells. Global gene expression analyses showed that ΔNp63α induced gene modules involved in both cell-to-cell and cell-to-extracellular-matrix junctions in mesenchymal type cells. Genome-wide analysis of p63 binding sites using ChIP-seq analyses confirmed binding of p63 to regulatory areas of genes associated with cell adhesion in prostate epithelial cells. DH1 and ZEB1 are two elemental factors in the control of EMT. Over-expression and knock-down of these factors, respectively, were not sufficient alone or in combination with ΔNp63α to reverse completely the mesenchymal phenotype. The partial reversion of epithelial to mesenchymal transition might reflect the ability of ΔNp63α, as a key co-ordinator of several epithelial gene expression modules, to reduce epithelial to mesenchymal plasticity (EMP). The utility of ΔNp63α expression and the potential of reduced EMP in order to counteract metastasis warrant further investigation.

Background: Expression of the androgen receptor (AR) is associated with androgen-dependent proliferation arrest and terminal differentiation of normal prostate epithelial cells. Additionally, activation of the AR is required for survival of benign luminal epithelial cells and primary cancer cells. Androgen deprivation therapy (ADT) leads to apoptosis in both benign and cancerous tissue. Cancer cell escape from ADT is known as castration-resistant prostate cancer (CRPC). In the course of CRPC development the AR typically switches from being a cell-intrinsic inhibitor of normal prostate epithelial cell proliferation to becoming an oncogene that is critical for prostate cancer cell proliferation. Methods: Immortalized human prostate basal epithelial EP156T cells and progeny cells that underwent epithelial to mesenchymal transition (EMT), primary prostate epithelial cells (PrECs) and prostate cancer cell lines LNCaP, VCaP and 22Rv1 were used to examine context dependent restriction and activation of the AR and classical target genes, such as KLK3. Genome-wide gene expression analyses and single cell protein analyses were applied to study the effect of different contexts. Results: A variety of growth conditions were tested and found unable to activate AR expression and transcription of classical androgen-dependent AR target genes, such as KLK3, in prostate epithelial cells with basal cell features or in mesenchymal type prostate cells. The restriction of androgen and AR dependent transcription of classical target genes in prostate basal epithelial cells was at the level of AR expression. Exogenous AR expression was sufficient for androgen-dependent transcription of AR target genes in prostate basal epithelial EP156T-AR cells, but did not exert a positive feedback on endogenous AR expression. Mesenchymal type prostate EPT3-AR cells with exogenous AR expression, in contrast to epithelial type EP156T-AR cells, were androgen non-responsive and were unable to produce detectable PSA in the culture supernatants even with higher levels of exogenous AR protein than in EP156T-AR and LNCaP cells for up to 2 weeks in androgen containing growth medium. The restricted PSA expression in the mesenchymal context suggests that if ADT increases the pool of mesenchymal type prostate cancer cells, then this might go undetected during PSA monitoring of disease progression. Citation Format: Jan Roger Olsen, Waqas Azeem, Margrete R. Hellem, Kristo Marvyin, Yaping Hua, Yi Qu, Lisha Li, Biaoyang Lin, XiSong Ke, Anne Margrete Oyan, Karl-Henning Kalland. Context dependent regulatory patterns of the androgen receptor (AR) and androgen receptor target genes. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1824.

The androgen receptor (AR) transcription factor plays a key role in the development and progression of prostate cancer. Inhibition of its ligand by androgen deprivation therapy (ADT) is consequently the main medical treatment of invasive prostate cancer. AR is activated and maintained throughout prostate cancer progression even in castration resistant prostate cancer (CRPC). Prostate cancer cells escape from ADT using a variety of mechanisms. The AR and target genes have therefore become even more focused therapeutic targets in aggressive and disseminated prostate cancer. AR and its classical target genes, such as KLK3 (PSA) are, however, efficiently shut off in basal epithelial prostate cells and possibly in prostate cancer stem cells (CSCs). To investigate mechanisms of AR and AR target gene activation in different subpopulations of prostate cancer cells, several androgen response elements (ARE) reporter vectors were developed. Three ARE reporter vectors were constructed with different ARE consensus sequences in promoters linked to either fluorescence or luciferase reporter genes in lentiviral vector backbones. Cell lines transduced with the different vectors expressed the reporters in an androgen-dependent way according to fluorescence microscopy, flow cytometry and multi-well fluorescent and luminescence recording. The 241B promoter sequence reporter was selected among the constructed ARE reporters on the basis of higher activity in initial screenings. The AR positive and androgen responsive prostate cancer cell line, LNCaP, and the prostate transit amplifying epithelial cell line, EP156T-AR with exogenous AR, were transduced with the lentiviral 241B-mCherry fluorescence reporter. Flow cytometry, multi-well reader and fluorescence microscopy results corresponded when reporter cells were treated with androgen and with the AR antagonist, enzalutamide, and with the anti-androgen, abiraterone. An SV40-promoter GFP reporter element was next cloned into the 241B-mCherry reporter. Constitutive expression of GFP facilitated normalization of ARE driven mCherry fluorescent signals. Furthermore, AR expression vectors were also constructed with the AR open reading frames cloned into lentiviral expression vectors and used in co-transfection and co-transduction experiments in AR negative cell types. The developed ARE reporter system will help us to investigate the role of the AR in differentiation and proliferation of prostate cells and to study the AR activity in two and three dimensional cell cultures. This system can also be useful in screening for drugs with activity against the AR. Citation Format: Waqas Azeem, Margrete R. Hellem, Jan R. Olsen, Yaping Hua, Kristo Marvyin, Lisha Li, Yi Qu, Biaoyang Lin, Xisong Ke, Anne M. Oyan, Karl-Henning Kalland. Assays for androgen receptor activity using cell based ARE reporter systems. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2902.

Background: The androgen receptor (AR) transcription factor plays pivotal roles in the development and progression of prostate cancer. AR is activated and maintained throughout prostate cancer progression even in castration-resistant prostate cancer (CRPC). AR and its classical target genes such as PSA (KLK3) are, however, efficiently shut off in basal epithelial prostate cells and possibly in prostate cancer stem cells (CSCs). There is limited information on the mechanisms that keep the AR OFF in these cells, and the conditions that turn the AR and target genes ON. Results: Fluorescent and luminescent reporters were constructed to develop a functional assay for AR activity. These reporters contain the repeated AR binding promoter sequences and were designed in a way that the AR can activate these AR element (ARE) reporters. The 241B reporter was selected among the constructed ARE reporters on the basis of higher activity. The AR positive prostate cancer cell line, LNCaP, was transduced with the lentiviral 241B-mCherry fluorescence reporter. FACS analysis quantitated the ARE reporter activity when reporter cells were treated with androgen and with the AR antagonist, enzalutamide, or the anti-androgen, abiraterone. AR expression vectors were also constructed with the AR open reading frames cloned into lentiviral expression vectors. All constructs were sequenced to verify the correct AR DNA sequence and their activity were tested using ARE reporter system. Conclusion: The developed ARE reporter system is useful to understand the mechanisms of AR and AR target gene activation in different subpopulations of prostate cancer cells. It will help us to investigate the role of the AR in differentiation and proliferation of prostate cells and to study the AR activity in two and three dimensional cell cultures. This system can also be useful in screening for drugs with activity against the AR. Citation Format: Waqas Azeem, Margrete R. Hellem, Jan R. Olsen, Yaping Hua, Kristo Marvyin, Lisha Li, Yi Qu, Biaoyang Lin, Xisong Ke, Anne M. Oyan, Karl-Henning Kalland. An androgen response element-based reporter assay for the detection of androgen receptor activity in prostate cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 79. doi:10.1158/1538-7445.AM2015-79

Background: The androgen receptor (AR) is activated and pathogenic in castration resistant prostate cancer (CRPC) due to a variety of escape mechanisms from anti-androgen treatment. The “cell of origin” of prostate cancer is not finally defined, but in different models prostate epithelial basal cells have been shown to develop into cancer with authentic prostate cancer features. The AR and target genes are effectively silenced in prostate epithelial basal cells. Given the importance of activated AR in prostate cancer we performed a reassessment of the basis of its silencing in prostate epithelial basal cells. Results: EP156T cells are derived from primary prostate epithelial basal cells and were propagated in monolayer cultures with features of transit amplifying cells in medium with low calcium concentration. The AR was not detectable in these cells and neither the AR nor target genes such as KLK3 (PSA), TMPRSS2 and NKX3-1 were induced following treatment with synthetic androgen (R1881) and a variety of growth factors and combinations as determined using sensitive Taqman real-time quantitative PCR assays, gene expression microarrays of cell lysates and PSA assays of cell supernatants. This was in contrast to LNCaP control cells where KLK3 was 12-fold and TMPRSS2 was 8-fold increased following R1881 induction. EP156T cells underwent epithelial to mesenchymal transition (EMT), and a series of progeny cells with an accumulating number of malignant hallmarks were derived. In these cells a spontaneous, but limited increase in AR mRNA was found. But the cells were neither androgen responsive nor androgen dependent as determined using R1881 stimulation and bicalutamide inhibitor, respectively. Shift to high calcium concentration in the medium rapidly induced morphological differentiation of basal cells, but still the AR and AR target gene expression was restricted. In 3-dimensional cultures in Matrigel structures with a distinct outer cell layer versus different inner cells were observed. A variety of methods was used to explore the molecular basis of restricted AR and target gene expression in these different culture conditions, including chromatin immunoprecipitation, indirect immunofluorescence, fluorescent promoter reporter constructs, gene expression and Western blot assays. Conclusion: In human prostate epithelial cells with basal cell traits we found strong restrictions to expression of the AR and AR target genes in monolayer cultures with a large variety of growth factors and combinations, including androgens. High calcium concentration induced morphological changes associated with epithelial differentiation, but with restricted AR and target gene expression. Growth of epithelial cells in Matrigel was associated with evidence of morphological differentiation. This model is useful for further identification of the molecular basis of restricted AR and target gene expression in prostate cells in comparison with malignant prostate cells. Citation Format: Margrete R. Hellem, Jan Roger Olsen, Yaping Hua, Yi Qu, Kristo Marvyin, Kari Rostad, Jie Liu, Lisha Li, Varda Rotter, Biaoyang Lin, Xisong Ke, Anne Margrete Oyan, Karl-Henning Kalland. Restriction of androgen receptor and target gene expression. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2329. doi:10.1158/1538-7445.AM2014-2329

Background: p63 is a transcription factor that is central for epithelial homeostasis and development. In our cell culture model of epithelial to mesenchymal transition (EMT) in a human prostate cells, p63 was one of the most down-regulated transcription factors during EMT. This led us to investigate the role of p63 in EMT by a gain and loss of function approach. Results: Over-expression of the predominant epithelial isoform ΔNp63α in mesenchymal EPT1 and EPT2 cells led to gain of several epithelial characteristics without resulting in a complete mesenchymal to epithelial transition (MET). When p63 was knocked down in epithelial EP156T cells complementary results were observed. Global gene expression analyses found that ΔNp63α induced gene modules involving cell adhesion genes in mesenchymal like cells. ChIP-seq analyses confirmed the enriched binding of p63 to regulatory areas of genes associated with cell adhesion in prostate epithelial cells. CDH1 and ZEB1 are two elemental factors in the control of EMT. Over-expression and knockdown of these factors, respectively, were not sufficient alone or in combination with ΔNp63α for full reversal of the mesenchymal phenotype in EPT cells. Conclusion: The partial reversion of epithelial to mesenchymal transition might reflect the ability of ΔNp63α, as a key co-ordinator of several epithelial gene expression modules, to reduce epithelial to mesenchymal plasticity (EMP). The potential of reduced EMP in order to counteract metastasis and the utility of ΔNp63α expression in this regard may provide a novel strategy to counteract the metastatic process. Citation Format: Jan Roger Olsen, Anne Margrete Øyan, Kari Rostad, Margrete R. Hellem, Jie Liu, Lisha Li, David Micklem, Hallvard Haugen, James B. Lorens, Xisong Ke, Varda Rotter, Biaoyang Lin, Karl-Henning Kalland. TP63 regulation of epithelial to mesenchymal transition in an experimental prostate cell model. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1820. doi:10.1158/1538-7445.AM2013-1820

Genome-wide gene expression analysis identified p63 as one of the most consistently under-expressed transcription factors in prostate cancer samples compared to matched benign prostate tissue. Two alternative p63 promoters generate two different N-terminal variants, TA or ΔN which contains and lacks the transactivating domain, respectively. Differential splicing generates multiple additional isoforms. The activity and interactions of the different isoforms remain unresolved. Isoform-specific real-time quantitative PCR assays revealed that ΔNp63α is the predominant isoform in epithelial prostate tissues, but other isoforms are detectable. Our group has established an experimental cell culture model based upon primary, immortalized prostate epithelial cells (EP156T cells), where p63 was shut down when EP156T cells underwent epithelial-to-mesenchymal transition (EMT) to become EPT1 cells. Subsequently, several additional mesenchymal like cell subtypes with additional malignant features, including anchorage independent growth in soft agar and ability to grow at much higher density in monolayers, were derived from EPT1 cells. All of these subtypes exhibited very low p63 expression. To examine the potential of p63 to induce mesenchymal to epithelial transition (MET) in this EMT model, we have stably re-expressed the ΔNp63α and TAp63α isoforms in different mesenchymal like cells of the model using retroviral/lentiviral vector transductions. Genome-wide gene expression analyses and phenotypic cellular assays revealed that the ΔNp63α isoform induced re-expression of multiple genes involved in cell adhesion. But this was not associated with complete MET induction. Cells re-expressing ΔNp63α obtained an intermediate morphology with both epithelial and mesenchymal traits, and with actin filaments organized in stress fibers. ΔNp63α re-expression significantly compromised migratory but not invasive ability of the cells. Based upon these findings we want to investigate whether p63 may compromise epithelial to mesenchymal plasticity in an animal model of tumorigenic cells and if there is differential effect on primary tumor growth compared to metastatic growth. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1290. doi:1538-7445.AM2012-1290

A family of transcription factors is constituted by p53, p63 and p73. Unlike p53, which is expressed in response to environmental stress, p63 (TP73L) is constitutively expressed at high levels in a variety of epithelial tissues including prostate. Our genome-wide gene expression analysis identified p63 as one of the most consistently under-expressed genes in prostate cancer samples compared to matched benign prostate tissue. All benign prostate samples including benign prostate hyperplasias (BPH) exhibited high p63 expression. Two alternative p63 promoters generate two different N-terminal variants, TA or ΔN which contains and lacks the transactivating domain, respectively. Differential splicing generates multiple additional isoforms. The activity and interactions of the different isoforms remain unresolved. Using isoform-specific TaqMan real-time quantitative PCR assays, we have found that ΔNp63α is the predominant isoform in prostate tissues, but the other isoforms are detectable. Our group has established a new experimental cell culture model based upon primary, immortalized prostate epithelial cells (EP156T cells), where p63 was found to be shut-down as EP156T cells underwent epithelial-to-mesenchymal transition (EMT) to become EPT1 cells. Subsequently, EPT2 cells were derived from EPT1 cells and p63 stayed shut-down. EPT2 cells had acquired several malignant features in contrast to the progenitors, including anchorage independent growth in soft agar and ability to grow at much higher density in monolayers. To dissect the role of p63 in EMT and in gene expression modules associated with carcinogenesis, we have stably re-expressed the predominant isoform ΔNp63α in both EPT1 and EPT2 cells using retroviral vector transductions. Microarray analysis shows that p63 re-expression leads to re-expression of genes participating in several cell-junction components, such as hemidesmosomes, focal adhesions and gap junctions. These genes were down-regulated during EMT. There were also morphological changes and a decreased ability to migrate following p63 re-expression. This indicates that ΔNp63α re-expression might result in a partial mesenchymal-to-epithelial transition (MET). The present focus is to identify co-factors that may act complementary or synergetically with p63 to induce a complete MET in EPT1 cells and to identify p63 target genes and regulatory cross-talk with relevance for anti-cancer strategies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3089. doi:10.1158/1538-7445.AM2011-3089