A phase I prospective, non-randomized trial of autologous dendritic cell-based cryoimmunotherapy in patients with metastatic castration-resistant prostate cancer

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.

GM-CSF, Flt3-L and IL-4 affect viability and function of conventional dendritic cell types 1 and 2

Conventional type 1 dendritic cells (cDC1) and conventional type 2 dendritic cells (cDC2) have attracted increasing attention as alternatives to monocyte-derived dendritic cells (moDCs) in cancer immunotherapy. Use of cDCs for therapy has been hindered by their low numbers in peripheral blood. In the present study, we found that extensive spontaneous apoptosis and cDC death in culture within 24hrs represent an additional challenge. Different media conditions that maintain cDC viability and function were investigated. CD141+ cDC1 and CD1c+ cDC2 were isolated from healthy blood donor buffy coats. Low viabilities were found with CellGenix DC, RPMI-1640, and X-VIVO 15 standard culture media and with several supplements at 24hrs and 48hrs. Among multiple factors it was found that GM-CSF improved both cDC1 and cDC2 viability, whereas Flt3-L and IL-4 only increased viability of cDC1 and cDC2, respectively. Combinations of these three cytokines improved viability of both cDCs further, both at 24hrs and 48hrs time points. Although these cytokines have been extensively investigated for their role in myeloid cell differentiation, and are also used clinically, their effects on mature cDCs remain incompletely known, in particular effects on pro-inflammatory or tolerogenic cDC features. HLA-DR, CD80, CD83, CD86, PD-L1 and PD-L2 cDC membrane expressions were relatively little affected by GM-CSF, IL-4 and Flt3-L cytokine supplements compared to the strong induction following Toll-like receptor (TLR) stimulation for 24hrs. With minor exceptions the three cytokines appeared to be permissive to the TLR-induced marker expression. Allogeneic mixed leukocyte reaction showed that the cytokines promoted T-cell proliferation and revealed a potential to boost both Th1 and Th2 polarizing cytokines. GM-CSF and Flt3-L and their combination improved the capability of cDC1 for dextran uptake, while in cDC2, dextran capture was improved by GM-CSF. The data suggest that GM-CSF, IL-4 and Flt3-L and combinations might be beneficial for DC viability and function in vitro. Limited viability of cDCs could be a confounding variable experimentally and in immunotherapy.

Abstract 1404: Novel STAT3 inhibitors targeting the STAT3 dimerization

Background The STAT3 pathway may drive prostate cancer (PCa) progression to metastatic castration-resistant prostate cancer (mCRPC). STAT3 may serve as a good target for the treatment of prostate cancer. The function of STAT3 relies significantly on its SH2 domain, which promotes STAT3 homo- or hetero-dimerization, protein-protein interaction and nuclear translocation of the STAT3 dimers needed for transcription. Due to this important role, the STAT3 SH2 domain becomes an attractive therapeutic target. In a drug discovery and development program we have found two small molecular compounds named 323-1 and 323-2 that were identified as novel STAT3 SH2 domain inhibitors in a series of experiments.

Material and methods In silico computational modeling, Drug Affinity Responsive Target Stability (DARTS) and Fluorescence Polarization (FP) assays were performed to examine whether compounds 323-1 and 323-2 could bind to the STAT3 protein. The antitumor activity of compounds 323-1 and 323-2 was firstly determined by clonogenic assays in different prostate tumor cells, then validated in the humanised NOD/SCID mouse CRPC model. Effects of compound 323-1 and 323-2 on STAT3 transcriptional activity were determined by the luciferase assay and protein levels by western blotting.

Results In silico computational modeling, DARTS and FP assays altogether determined 323-1 and 323-2 as direct STAT3 inhibitors targeting the STAT3 SH2 domain and inhibiting both phosphorylated and non-phosphorylated STAT3 dimerization. Computational docking predicted that both 323 compounds bind to three subpockets of the STAT3 SH2 domain with full inhibition of STAT3. FP assay further confirmed that 323s target the STAT3 SH2 domain by competitively abrogating the interaction between STAT3 and the SH2-binding peptide GpYLPQTV. Compared with S3I-201, the 323 compounds exhibited stronger inhibition of STAT3 and reduced the level of IL-6-stimulated phosphorylation of STAT3 (Tyr705) in LNCaP cells over the phosphorylation of STAT1 (Tyr701) induced by IFN-ɣ in PC3 cells or the phosphorylation of STAT1 (Ser727) in DU145 cells. Both compounds down-regulated STAT3 target genes MCL1 and cyclin D1. The in-vivo data supported that 323s significantly inhibited LNCaP cell generated CRPC tumor growth. Thus, the two compounds are promising leading compounds for the treatment of cancers with hyper-activated STAT3.

Conclusions Here we report that these compounds modulate the IL-6/STAT3 pathway by 1) inhibition of STAT3 phosphorylation on Tyr705 and 2) disruption of STAT3 dimerization by directly targeting its SH2 domain; 3) inhibition of STAT3 transcriptional activity. Thus, the compounds 323-1 and 323-2 are promising new leading compounds for therapeutic STAT3 inhibition.

Citation Format: Yaping Hua, Waqas Azeem, Anne Margrete Øyan, Karl-Henning Kalland. Novel STAT3 inhibitors targeting the STAT3 dimerization [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1404.

Abstract 3568: Robust and potent dendritic cells for cancer immunotherapy

Background: Dendritic cells (DCs) are fundamental to adaptive immunity by detecting, engulfing and presenting foreign or changed antigenic peptides to lymphocytes that thereafter initiate antigen-specific immune attacks. DC-based immunotherapy against cancer has been promising for a long time, but has not yet met expectations. Cancer cell heterogeneity and numerous immune evasion mechanisms represent challenges. According to textbook renderings, DCs may induce either tolerance or immune activation depending upon the nature of the encountered antigen and the status of the microenvironment. Recently, we have discovered a more complicated scenario according to which monocyte-derived DCs (moDCs) exhibit dual pro- and anti-inflammatory features, suggesting that selected conditions that enhance pro-inflammatory features and counteract tolerogenic features could generate more robust and potent DCs for cancer therapy.

Materials and Methods: Healthy blood donor buffy coats were used for the isolation of monocytes and conventional CD141+ and CD1c+ natural circulating DCs. IL-4 and GM-CSF were used to differentiate monocytes into immature moDCs. Toll-like receptor agonists were used to induce DC maturation, and specific agonists and inhibitors were tested in different DC variants. Flow cytometry, ELISA determination of cytokine secretion, HPLC-based quantitation of kynurenine secretion, genome-wide gene expression analyses and functional assays, such as antigen uptake, migration and the mixed leukocyte reaction were used for evaluation of treated DCs.

Results: Conventional DCs were more susceptible to apoptosis, and dependent upon culture conditions, than moDCs. Inhibition of β-catenin signaling stimulated several pro-inflammatory features, e.g. increased IL-12 and decreased IL-10 secretion, with reciprocal effects caused by β-catenin stimulation. Maturation of moDCs was accompanied by very strong induction of indoleamine 2, 3-dioxygenase 1 (IDO1) transcription and paralleled by increased kynurenine secretion, but this was partially counteracted by β-catenin stimulation.

Conclusions: Preparation of more potent DCs for cancer therapy needs to take into account DC longevity and conflicting activation patterns of pro- and anti-inflammatory abilities.

Citation Format: Waqas Azeem, Seyed Mohammad Lellahi, Yaping Hua, Anne Margrete Øyan, Benjamin Gabriel, Karl-Henning Kalland. Robust and potent dendritic cells for cancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3568.

Novel STAT3 Inhibitors Targeting STAT3 Dimerization by Binding to the STAT3 SH2 Domain

Our drug discovery model has identified two novel STAT3 SH2 domain inhibitors 323–1 and 323–2 (delavatine A stereoisomers) in a series of experiments. In silico computational modeling, drug affinity responsive target stability (DARTS), and fluorescence polarization (FP) assays altogether determined that 323–1 and 323–2 directly target the STAT3 SH2 domain and inhibited both phosphorylated and non-phosphorylated STAT3 dimerization. Computational docking predicted that compound 323s bind to three subpockets of the STAT3 SH2 domain. The 323s inhibition of STAT3 dimerization was more potent than the commercial STAT3 SH2 domain inhibitor S3I-201 in the co-immunoprecipitation assay, correlating with computational docking data. The fluorescence polarization assay further confirmed that the compound 323s target the STAT3 SH2 domain by competitively abrogating the interaction between STAT3 and the SH2-binding peptide GpYLPQTV. Compared with S3I-201, the 323 compounds exhibited stronger inhibition of STAT3 and reduced the level of IL-6-stimulated phosphorylation of STAT3 (Tyr705) in LNCaP cells over the phosphorylation of STAT1 (Tyr701) induced by IFN-ɣ in PC3 cells or the phosphorylation of STAT1 (Ser727) in DU145 cells. Both compounds downregulated STAT3 target genes MCL1 and cyclin D1. Thus, the two compounds are promising lead compounds for the treatment of cancers with hyper-activated STAT3.

Proteasome-Mediated Regulation of GATA2 Expression and Androgen Receptor Transcription in Benign Prostate Epithelial Cells

GATA2 has been shown to be an important transcription factor together with androgen receptor (AR) in prostate cancer cells. Less is known about GATA2 in benign prostate epithelial cells. We have investigated if GATA2 exogenous expression in prostate epithelial basal-like cells could induce AR transcription or luminal differentiation. Prostate epithelial basal-like (transit amplifying) cells were transduced with lentiviral vector expressing GATA2. Luminal differentiation markers were assessed by RT-qPCR, Western blot and global gene expression microarrays. We utilized our previously established AR and androgen-dependent fluorescence reporter assay to investigate AR activity at the single-cell level. Exogenous GATA2 protein was rapidly and proteasome-dependently degraded. GATA2 protein expression was rescued by the proteasome inhibitor MG132 and partly by mutating the target site of the E3 ligase FBXW7. Moreover, MG132-mediated proteasome inhibition induced AR mRNA and additional luminal marker gene transcription in the prostate transit amplifying cells. Different types of intrinsic mechanisms restricted GATA2 expression in the transit amplifying cells. The appearance of AR mRNA and additional luminal marker gene expression changes following proteasome inhibition suggests control of essential cofactor(s) of AR mRNA expression and luminal differentiation at this proteolytic level.

Role of digital health in improving physical and mental well-being during COVID-19 pandemic

Introduction

Due to the COVID-19 pandemic, there is a steep rise in the acceptance of telemedicine and digital health, including increased interest in pursuing mental health treatment through telepsychiatry. Digital health helps following social distancing measures and increases the health outcomes.

Objectives

To see the role of digital health in improving physical and mental well-being during COVID-19 Pandemic

Methods

This study is a part of a large global project where 240 people inquired advice on phone app during COVID-19-Pandemic. Later on, a short study was conducted on the same population through survey to evaluate the effectiveness of digital health/tele-mental health. We also searched PubMed, Google Scholar, PsychInfo, and Medline for words “Digital Health, Tele-mental health, COVID-19-Pandemic”. Reviewed 40 articles and included 3 in this review1,4,5.

Results

We received a total of 98 responses. 65.6% people reported that online health resources are helpful in relieving pandemic-induced anxiety/stress, 66.2% reported to continue online health services after pandemic, 37.7% noted that digital health saves times in waiting areas, 46% reported lack of physical interaction with doctor as a disadvantage of digital health, and 40.3% reported comfort in using tele-mental health. Our literature review has shown barriers like privacy concerns and technological issues1. Provision of tele-psychiatry is safe and effective in continuity of mental health care.4,5

Conclusions

There has been an increased inclination towards digital health during any disaster. During COVID-19-Pandemic, digital health has increased access to mental health care and reduced risk of infection. The drawbacks include poor patient-doctor relationship, reimbursement concerns, and lack of confidentiality.

In this study: Adapting to the new normal in COVID-19 pandemic; a global survey & literature review

Introduction

Globally, governments have enforced protective measures of social distancing to prevent COVID-19 spread. The lifestyles of public have essentially transformed due to these actions. This study evaluates the effects of COVID-19 on connections and behavior/life adaptations.

Objectives

Changes in life style and behavior in COVID-19-Pandemic

Methods

We conducted a global cross-sectional study via survey on phone apps and social media platforms in population aged ≥ 16, including questions regarding demographic data and lifestyle changes. We also searched databases APA PsycNet, PubMed, PsycINFO, and Medline; reviewed 40 articles and included 3 in this review, a cross-sectional online survey1, a planned questionnaire2, and a study on 600 adolescents, age 10-19 in Palestine3

Results

Our survey data showed total of 1002 responses, 31.7% decreased sleep, 42.1% increased appetite, 70.6% bulk-buying, and 50.2% weight gain. 43.1% less socialization than before, 78.7% increased screen time, 53.5% excessive hand washing/wiping surfaces, 45% reported social distancing facilitated in overpowering the fear of contracting infection, 29.4% negative impact on relationships, 80.7% noticed changes in behavior including shaking hands/hugging/speaking with a mask on, 49.5% adopted new hobbies, 34.9% showed increase in meditation. The literature review revealed that since COVID-19, there is an increase in screen time, weight, appetite, sleep, and a decrease in physical activity1-3, and greater adherence to the Mediterranean diet in younger population2

Conclusions

COVID-19 induced quarantine has caused increased screen time, appetite, weight gain, adoption of new hobbies, bulk-buying, hand washing, meditation, reduced sleep, and negatively impacted interaction/relationships. COVID-19 pandemic is ongoing and our data needs further assessment in more population studies.

Disclosure

No significant relationships.

A prospective phase I trial of dendritic cell-based cryoimmunotherapy in metastatic castration-resistant prostate cancer

3029

Background: Dendritic cell (DC)-based cryoimmunotherapy (CryoIT) was used to treat metastatic castration-resistant prostate cancer in a Phase I clinical trial. Primary objective was safety of treatment. Secondarily, clinical, radiological and immunological treatment responses were investigated. Methods: In 18 patients cryoablation by a freeze-thaw process under general anesthesia was performed, followed by intratumoral autologous immature DC injection. In the last 9 patients checkpoint inhibition of either CTLA-4 or PD-1 was added. Subjects had minimum 46 weeks follow-up. Adverse events (AEs) and blood analyses were registered at all visits. Disease progression was determined by three imaging modalities according to (i)RECISTv1.1 and progression-free survival (PFS) by Kaplan-Meier method. Circulating tumor cells (CTC/7.5 mL, CellSearch) and ultradeep T-cell receptor (TCR) b-chain sequences (TCRSafe) were enumerated. Patients were separated by CTC into none (n=10), 1-4 (n=4) and ≥ 5 (n=4). Health related quality of life (HRQoL) measured by EORTC-QLQ C30 questionnaire were answered at inclusion, and 10, 22 and 46 weeks post CryoIT. Scores were calculated according to the EORTC manual. Results: Subjects progressing within 22 weeks had higher PSA (p=0.03). AE profile of the total cohort (n=18) was comparable with interim reports (n=13); of 20 possible DC-related AEs one was severe (urinary retention) and 19 mild-to-moderate, and spread independent of treatment regime. Maximum tolerated dose of DC was not reached. By 46 weeks, imaging showed 6 patients partial response or stable disease. Median PFS was 150 days in total cohort. Pretreatment CTC counts ≥5 indicated higher progression rates and recurring CTC. Ultradeep TCR-sequencing showed more prevalent and higher expressed (>5-fold) new TCR clonotypes at 2-6 weeks in men without progression. Participants reported high and stable HRQoL scores throughout the study. However, presence of CTC was associated with worse HRQoL scores at week 10 (p=0.031) and 22 (p=0.005). Conclusions: DC treatment seems safe and well tolerated, also combined with checkpoint inhibitors. Effect is indicated in subjects with moderate pre-treatment PSA levels. Immune responses are suggested by higher number of novel TCR clonotypes in men with non-progressive disease. Clinical trial information: NCT02423928 .

Dual Pro- and Anti-Inflammatory Features of Monocyte-Derived Dendritic Cells

The transcription factor β-catenin is able to induce tolerogenic/anti-inflammatory features in different types of dendritic cells (DCs). Monocyte-derived dendritic cells (moDCs) have been widely used in dendritic cell-based cancer therapy, but so far with limited clinical efficacy. We wanted to investigate the hypothesis that aberrant differentiation or induction of dual pro- and anti-inflammatory features may be β-catenin dependent in moDCs. β-catenin was detectable in both immature and lipopolysaccharide (LPS)-stimulated DCs. The β-catenin inhibitor ICG-001 dose-dependently increased the pro-inflammatory signature cytokine IL-12p70 and decreased the anti-inflammatory signature molecule IL-10. The β-catenin activator 6-bromoindirubin-3′-oxime (6-BIO) dose-dependently increased total and nuclear β-catenin, and this was associated with decreased IL-12p70, increased IL-10, and reduced surface expression of activation markers, such as CD80 and CD86, and increased expression of inhibitory markers, such as PD-L1. 6-BIO and ICG-001 competed dose-dependently regarding these features. Genome-wide mRNA expression analyses further underscored the dual development of pro- and anti-inflammatory features of LPS-matured moDCs and suggest a role for β-catenin inhibition in production of more potent therapeutic moDCs.

Abstract 2340: Differentiation of pro- and anti-inflammatory features of monocyte-derived dendritic cells

Background: Dendritic cells (DCs) are the most potent antigen-presenting cells of the immune system and are consequently exploited in cancer immunotherapy in order to present tumor-associated antigens to lymphocytes. The ability of tumor cells to induce tolerogenic DCs and avoid the immune system challenges DC-based immunotherapies. Utilizing buffycoats of healthy blood donors we have investigated the activation of gene expression programs conventionally associated with either pro- or anti-inflammatory features of monocyte-derived DCs.

Methodology: Following isolation of monocytes from buffycoats, various culture conditions were tested to generate immature DCs and to mature and activate them in vitro. Genome-wide gene expression, secretion of cytokines and tryptophan metabolites, surface expression of maturation and activation markers, and functional abilities were analyzed. Specifically, beta-catenin and indoleamine 2,3-dioxigenase 1 (IDO-1) activation were examined using both agonists and inhibitors of those pathways.

Results: A considerable variability among buffycoats of different healthy blood donors was observed regarding DC yield and cytokine secretion. Induction time to generate immature DCs with interleukin-4 and granulocyte-macrophage colony-stimulating factor affected DC differentiation. Several maturation conditions induced strong IDO-1 expression. Activation of beta-catenin during DC maturation induced anti-inflammatory features that could be competed by adding beta-catenin inhibitors during cultivation of the cells. Pro- and anti-inflammatory features often co-existed in mature DCs.

Conclusions: Beta-catenin and IDO-1 activation are prevalent according to different conditions of monocyte-derived DC maturation and associated with anti-inflammatory features. Both pathways can be inhibited by specific antagonists. More robust pro-inflammatory DC generation is desirable for more effective cancer immunotherapy.

Citation Format: Ragnhild Maukon Bakke, Waqas Azeem, Silke Appel, Karl-Henning Kalland, Anne Margrete Oyan. Differentiation of pro- and anti-inflammatory features of monocyte-derived dendritic cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2340.

Dual androgen receptor (AR) and STAT3 inhibition by a compound targeting the AR amino-terminal domain

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.

Abstract CT066: 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

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.

Abstract 2902: Assays for androgen receptor activity using cell based ARE reporter systems

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.

Abstract 1824: Context dependent regulatory patterns of the androgen receptor (AR) and androgen receptor target genes

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.

Context dependent regulatory patterns of the androgen receptor and androgen receptor target genes

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.

Abstract 79: An androgen response element-based reporter assay for the detection of androgen receptor activity in prostate cells

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