bluuebunny/crossref_metadata_2025_split huggingface dataset:
Abstract 3368: A novel anti-CTLA-4 antibody with potent anti-tumor activity emerged using humanized CTLA-4 mouse model
Authors: Guo Chaoshe , Yang Yi , Li Zhihong , Li Yanan , Chen Yunyun 
Published: September 2020

Abstract
CTLA-4 (Cytotoxic T-lymphocyte antigen 4), also known as CD152, belongs to immunoglobulin superfamily. It is an intracellular protein expressed in resting T cells; CTLA-4 translocates to the cell surface and transmits an inhibitory signal to T cells. In addition, CTLA-4 competes with its homologous T-cell co-stimulatory protein CD28 for ligands expressed on APC, namely CD80 (B7-1) and CD86 (B7-2), thereby antagonizing CD28 and inhibiting CD28 signaling, resulting in inhibition of IL-2, IFN-γ, IL-4 cytokines production, IL-2 receptor expression and cell cycle progression. Because Tregs constitutively express CTLA-4 at high levels, anti-CTLA-4 therapy would be expected to have the greatest effect on these cells. Ipilimumab, a fully human IgG1 monoclonal antibody, is the only commercially available CTLA-4 antagonist. It has been approved by FDA for treatment of metastatic melanoma, adjuvant melanoma and advanced renal cell carcinoma, based on its significant effect of tumor suppression demonstrated in clinical trials.
We have interests in searching for potent CTLA-4 antagonists. We selected an antibody with the best efficacy, namely YH001, from the candidate molecules through Biocytoge's in vivo drug screening platform. YH001 is a recombinant humanized anti-CTLA-4 IgG1 monoclonal antibody and it can bind with human CTLA-4 potently and specifically, without reactivity with other CD28 family receptors. YH001 was able to block the CTLA-4/CD80 and CTLA-4/CD86 interactions and potentiate CD28 signaling in the presence of cognate TCR stimulation. Moreover, YH001 also induced stronger bioluminescence than ipilimumab in the reporter assay. YH001 showed more potent ADCC activities than ipilimumab. YH001 showed dose-dependent in vivo anti-cancer efficacy, as well as Treg depletion and increased CD8+/Treg ratio in human CTLA-4 knock-in mice bearing MC38 tumors.
Exposure to YH001 was dose proportional with a half-life of approximately 5 days in cynomolgus monkey. Our preclinical investigation of YH001 demonstrates Biocytogen's capability in discovering clinical candidates using its robust antibody discovery platform.
Citation Format: Chaoshe Guo, Yi Yang, Zhihong Li, Yanan Li, Yunyun Chen. A novel anti-CTLA-4 antibody with potent anti-tumor activity emerged using humanized CTLA-4 mouse model [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3368.
Abstract 3369: Rapid screening of novel OX40 agonistic antibodies for cancer immunotherapy
Authors: Shen Yuelei , Li Zhihong , Yang Yi , Chen Yunyun , Zhu Yu 
Published: September 2020

Abstract
OX40, also known as TNFRSF4 or CD134, is a member of the tumor necrosis factor receptor superfamily and is an important co-stimulator of T cell responses. OX40L expressed at high levels on activated antigen presenting cells (APCs) can result in higher order multimerization of OX40 receptors, leading to stronger activation in T cells. OX40 plays an important role in memory T cell formation. The highest levels of OX40 are found on effector and central memory CD4+ T cells and regulatory T cells (Treg). Given the duality of OX40 agonism in both stimulating effector T cell activity and suppressing Treg activity, OX40 agonists have been widely explored in the setting of cancer immunotherapy.
We hoped to develop novel OX40 agonists that can effectively inhibit tumor growth. YH002 is a recombinant, humanized IgG1 monoclonal antibody that specifically targets OX40. In vitro studies demonstrated that YH002 bound specifically and potently to human and monkey OX40 proteins. YH002 was able to dose-dependently potentiate the activation of human OX40 on reporter cells in the presence of FcγRIIB-expressing accessory cells. YH002 mediated ADCC activity in vitro. YH002 demonstrated robust anti-tumor efficacy with a bell-shaped dose response relationship against established MC38 syngeneic tumors in human OX40 transgenic mice (B-hOX40 mice) and Treg depletion were noted in tumor-infiltrating lymphocyte analysis using the same murine model. In conclusion, YH002 enhances anti-tumor activities by stimulating effector T cells and overcoming immune suppressions via suppressing or depleting regulatory T cells. Furthermore, we showed that YH002 works in concert with Pembrolizumab in double humanized model of h-OX40 and h-PD1. The combination of YH002 and ipilimumab is synergistic in double humanized model of h-OX40 and h-CTLA4. In the GLP-compliant single-dose toxicology study, the MTD of a single i.v. dose of YH002 in cynomolgus monkeys was considered to be 200 mg/kg/day. Repeated i.v. infusions of YH002 to male and female cynomolgus monkeys at 10, 30, or 90 mg/kg for 29 days (QW×5) were tolerated, the HNSTD was considered to be 90 mg/kg.
Citation Format: Yuelei Shen, Zhihong Li, Yi Yang, Yunyun Chen, Yu Zhu. Rapid screening of novel OX40 agonistic antibodies for cancer immunotherapy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3369.
Abstract 340: ABI1 and androgen dependence in prostate cancer
Authors: Kotula Leszek , Porter Baylee A. , Li Xiang , Ortiz Maria A. , Khanna Rakesh , Zhang Fan , Kung Sonia H. , Fazli Ladan , Gleave Martin E. , Bratslavsky Gennady , Ross Jeffrey S. 
Published: September 2020

Abstract
Background: Androgen independence is the most challenging problem in the treatment of advanced prostate cancer. Although most patients with early-stage prostate cancer can be cured with surgical and/or radiation treatment, the remainder of patients ultimately recur with metastatic disease upon development of resistance to anti-androgen therapy. Epithelial mesenchymal transition (EMT) and lineage plasticity has been proposed as key mechanisms underlying resistance in treatment-induced prostate cancer with neuroendocrine features (NEPC). There has been a rise in treatment-induced NEPC with increased use of anti-androgen therapies. ABI1 regulates EMT by suppressing FYN-STAT3 activation downstream from noncanonical WNT pathway, but the interaction of ABI1 with androgen pathway is not known. We sought to determine the effect of neoadjuvant hormone treatment (NHT) on ABI1 expression levels in different tumor types.
Methods: Here we analyzed ABI1 expression (IHC) in tissue microarray containing 75 tumors with no prior treatment, 198 patients subjected to NHT prior to surgery and 39 castration resistant tumors (total n=307). Androgen-induced ABI1 expression was determined upon R1881 treatment by Western blotting and immunofluorescence in hormone- sensitive LNCaP cells.
Results: ABI1 expression was significantly downregulated in tumors from patients undergoing NHT(p&lt;0.05). ABI1 expression was significantly increased in CRPC tumors developed while on hormone therapy compared to ABI1 expression in tumors undergoing NHT (p&lt;0.001), or with NEPC (p&lt;0.001). Consistently with these observations, ABI1 expression was upregulated upon treatment of LNCaP cells with R1881 and downregulated by treatment of cells with enzalutamide.
Conclusion: ABI1 is an androgen sensitive gene. ABI1 expression is increased in CRPC, most likely secondary to androgen receptor reactivation. It is subsequently downregulated in NEPC, hence, we hypothesize that this may be a key mechanism driving the NEPC phenotype through promoting EMT. Further understanding of the role ABI1 may play in this transformation will provide a more mechanistic understanding of prostate cancer progression and maylead to improved targeted treatment options.
Citation Format: Leszek Kotula, Baylee A. Porter, Xiang Li, Maria A. Ortiz, Rakesh Khanna, Fan Zhang, Sonia H. Kung, Ladan Fazli, Martin E. Gleave, Gennady Bratslavsky, Jeffrey S. Ross. ABI1 and androgen dependence in prostate cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 340.
Abstract 3401: Targeting lysosomal homeostasis in ovarian cancer through drug repurposing
Authors: Marastoni Stefano , Pesic Aleksandra , Nair Sree Narayanan , Li Zhu Juan , Madani Ali , Haibe-Kains Benjamin , Wouters Bradly G. , Joshua Anthony 
Published: September 2020

Abstract
Background: Drug repurposing has become increasingly attractive as it avoids the long processes and costs associated with drug discovery. Itraconazole (Itra) is a broad-spectrum anti-fungal agent which has an established broad spectrum of activity in human cell lines including cholesterol antagonism and inhibition of Hedgehog and mTOR pathways. Many in vitro, in vivo and clinical studies have suggested anti-proliferative activity both alone and in combination with other chemotherapeutic agents, in particular in ovarian cancer. This study is aimed at supporting the therapeutic potential of Itra and discovering and repurposing new drugs that can increase Itra anticancer activity as well as identifying new targets in the treatment of ovarian cancer.
Methods: We tested a panel of 32 ovarian cancer cell lines with different doses of Itra and identified a subset of cells which showed significant sensitivity to the drug. To identify genetic vulnerabilities and find new therapeutic targets to combine with Itra, we performed a whole genome sensitivity CRISPR screen in 2 cell lines (TOV1946 and OVCAR5) treated with non-toxic (IC10) concentrations of Itra.
Results: Pathway analysis on the top hits from both the screens showed a significant involvement of lysosomal compartments, and in particular dynamics between trans Golgi network and late endosomes/lysosomes, pathways that are affected by the autophagy inhibitor Chloroquine (CQ). We subsequently demonstrated that the combination of Itra and CQ had a synergistic effect in many ovarian cancer cell lines, even in those resistant to Itra. Further, genetic and pharmacological manipulation of autophagy indicated that upstream inhibition of autophagy is not a key mediator of the Itra/CQ mechanism of action. However, combination of Itra with other lysosomotropic agents (Concanamycin A, Bafilomycin A and Tamoxifen) displayed overlapping activity with Itra/CQ, supporting the lysosomal involvement in sensitizing cells to Itra resulted from the CRISPR screens. Analysis of lysosomal pattern and function showed a combined effect of Itra and CQ in targeting lysosomes and neutralizing their activity.
Conclusion: We identified two FDA approved drugs – CQ and Tamoxifen - that can be used in combination with Itra and exert a potent anti-tumor effect in ovarian cancer by affecting lyosomal function and suggesting a likely dependency of these cells on lysosomal biology. Further studies are in progress.
Citation Format: Stefano Marastoni, Aleksandra Pesic, Sree Narayanan Nair, Zhu Juan Li, Ali Madani, Benjamin Haibe-Kains, Bradly G. Wouters, Anthony Joshua. Targeting lysosomal homeostasis in ovarian cancer through drug repurposing [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3401.
Abstract 3427: Finding critical cancer driving and cancer suppressing genes using functional genomics screening in vivo
Authors: Herold Marco Josef , Mizutani Shinsuke , Deng Yexuan , Janic Ana , Kueh Andrew , Pal Martin , Wilcox Stephen , Tai Lin , Kelly Gemma L. , Strasser Andreas 
Published: September 2020

Abstract
P53 is one of the most potent tumour suppressors and its activity is also required for cancer cells to respond to diverse chemotherapeutic drugs. Focused functional genetic screens in haematopoietic cells in vivo revealed DNA repair to be one of the most critical downstream pathways for p53's tumour suppressive function. Recently, we extended our search for novel tumour suppressor genes acting potentially outside the p53 tumour suppressor pathway. To this end, we performed whole genome CRISPR/Cas9 knockout screening in vivo, using the Eµ-Myc transgenic mouse model. This identified previously unknown genes and hence pathways, which upon deletion/mutation lead to the acceleration of tumour onset. Amongst these novel tumour suppressor genes, we identified the GATOR1 members DEPDC5 and NPRL3, which are known inhibitors of the mTOR pathway. Interestingly, drug mediated inhibition of mTOR activity with rapamycin or Torin1 in GATOR1 deficient Eµ-Myc cells led to efficient killing of these malignant cells, which was in striking contrast to control Eµ-Myc lymphoma cells that were resistant to this treatment. In parallel we conducted CRISPR/Cas9 screens for identifying p53 bound promoter and enhancer elements in haematopoietic cells in vivo. Excitingly, we observed that targeting the NPRL3 promoter led to accelerated tumour onset in the Eµ-Myc transgenic model, suggesting that NPRL3 is under direct transcriptional control of p53. These results indicate that p53 mediated shutdown of the mTOR pathway through upregulation of the GATOR1 member NPRL3 is a critical tumour suppressive function of p53.
Citation Format: Marco Josef Herold, Shinsuke Mizutani, Yexuan Deng, Ana Janic, Andrew Kueh, Martin Pal, Stephen Wilcox, Lin Tai, Gemma L. Kelly, Andreas Strasser. Finding critical cancer driving and cancer suppressing genes using functional genomics screening in vivo [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3427.
Abstract 3428: The role of methylthioadenosine phosphorylase in melanoma
Authors: Hsiao Jennifer Jia-An , Andreu-Perez Pedro , Hejna Miroslav , Kemény Lajos V. , Song Jun , Fisher David E. 
Published: September 2020

Abstract
Methylthioadenosine phosphorylase (MTAP) is an enzyme that is expressed in virtually all normal tissues but lost in many cancers. MTAP deficiency can be due to either deletion of the MTAP gene or methylation of the MTAP promoter. In normal cells, MTAP catalyzes the conversion of methylthioadenosine (MTA), produced during polyamine biosynthesis, to adenine and 5-methylthioribose-1-phosphate, which is subsequently converted to methionine. Although recent genome wide association studies (GWAS) have associated the MTAP locus with melanoma risk, the molecular mechanisms linking MTAP loss to increased tumorigenesis are not yet fully understood. In this study, we hypothesized that loss of MTAP and the resulting accumulation of MTA would have an effect on microphthalmia transcription factor (MITF), the master regulator of melanocytes that has been shown to be an oncogene in melanoma. We present a novel signaling mechanism in which loss of MTAP and subsequent accumulation of MTA induces expression of MITF via inhibition of the phosphodiesterase PDE4D3 by MTA. Inhibition of PKA abolishes the induction of MITF, suggesting that the PKA pathway is hyperactivated when MTAP levels are low. We show that downregulation of MTAP expression leads to increased proliferation of melanoma cells. Using a melanoma xenograft mouse model, we observed that downregulation of MTAP expression leads to increased tumor growth in vivo. These data all point to MTAP as a tumor suppressor in melanoma, and indicate that MTAP loss is an alternative mechanism of dysregulating MITF, a known oncogene in melanoma.
Citation Format: Jennifer Jia-An Hsiao, Pedro Andreu-Perez, Miroslav Hejna, Lajos V. Kemény, Jun Song, David E. Fisher. The role of methylthioadenosine phosphorylase in melanoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3428.
Abstract 3430: The protein phosphatase 4 complex is a tumor suppressor in prostate cancer
Authors: Watson Philip A. , Lawrence Kayla E. , Nadkarni Tejasveeta V. , Ishmael Taslima F. , Lee Eugine , Rivera Aura C. Agudelo , Love Jillian R. , Wongvipat John , Cai Ling , Nazir Abbas , Iaquinta Phillip J. , Chang Kenneth , Liang Yupu , Hannon Greg J. , Sawyers Charles L. 
Published: September 2020

Abstract
Regions of recurring chromosomal deletions have been annotated in clinical prostate cancer (PCa), but for many of them there is an incomplete understanding of their contributions to disease progression. From an in vivo shRNA enrichment screen of the PCa deletome, we identified the serine threonine protein phosphatase 4 (PP4) regulatory subunit 2 (PPP4R2) as a candidate tumor suppressor, which undergoes copy number loss in 16% of primary PCa. Knockdown or CRISPR-Cas9 mediated knockout of PPP4R2 increased the growth rate of PCa xenograft tumors. Along with the catalytic subunit PP4C and an additional regulatory subunit (either PP4R3A or PP4R3B), PP4R2 forms two distinct heterotrimeric phosphatase holoenzymes. PP4R2 was critical for holoenzyme stability, as its deletion resulted in rapid, moderate downregulation of the other PP4 subunit proteins. The increased tumor growth rate and downregulation of PP4C resulting from loss of PP4R2 could be replicated by combined deletion of PPP4R3A and PPP4R3B, or by directly targeting PPP4C itself. Collectively, these findings implicated PP4C as the likely direct mediator of tumor suppression through the PP4 complex. This was confirmed in both PPP4R2 and PPP4R3A/PPP4R3B knockout cells in vivo by restoring PP4C to its normal physiological level through a dox-inducible cDNA, which reversed the accelerated tumor growth rate conferred by the deletion of the regulatory subunits. Phosphatase activity of PP4C was critical, as add-back of a catalytically dead PP4C mutant (D82A) was unable to reverse the growth rate of PPP4C knockout tumors. Interestingly, we found that the androgen receptor (AR), which is the principal therapeutic target for PCa, was co-immunoprecipitated by PP4C and its regulatory subunits. This suggests that AR could be a substrate for PP4C and is potentially present in a hyperphosphorylated and hyperactivated state in PCa that have decreased PP4 phosphatase activity. Our findings highlight a previously unappreciated tumor suppressor role for the PP4 complex in PCa, with the regulatory subunit PP4R2 providing a key function in stabilizing PP4C and thereby preserving its phosphatase activity.
Citation Format: Philip A. Watson, Kayla E. Lawrence, Tejasveeta V. Nadkarni, Taslima F. Ishmael, Eugine Lee, Aura C. Agudelo Rivera, Jillian R. Love, John Wongvipat, Ling Cai, Abbas Nazir, Phillip J. Iaquinta, Kenneth Chang, Yupu Liang, Greg J. Hannon, Charles L. Sawyers. The protein phosphatase 4 complex is a tumor suppressor in prostate cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3430.
Abstract 3438: Hypoxia inhibits BMP4-induced astrocytic differentiation in glioma stem cells
Authors: Wu Ronald S. , Liedtke Elisabeth , Mansouri Sheila , Brazier Samantha , Guilhamon Paul , Park Nicole I. , Chen Eric , Lupien Mathieu , De Carvalho Daniel D. , Dirks Peter G. , Zadeh Gelareh , Wouters Bradley G. 
Published: September 2020

Abstract
The tumor microenvironment is an important contributor to malignancy in glioblastoma (GBM) by influencing stemness properties in glioma stem cells (GSCs) and their capacity for differentiation into various cell types. Tumor hypoxia is a common feature of the GBM microenvironment and can influence cell state through a variety of processes including the inhibition of oxygen-dependent lysine histone demethylases (KDMs) and subsequent epigenetic changes required for differentiation or maintenance of the stem cell state. However, the precise mechanisms underlying hypoxic restriction of differentiation to specific neural lineages is unclear. Here, we show that hypoxia suppresses astrocytic differentiation induced by bone morphogenetic protein 4 (BMP4) in patient-derived GSCs. In 8/10 patient derived GSC lines, BMP4 induced expression of astrocytic markers, such as glial fibrillary acidic protein, and this induction was repressed by hypoxia in 7/10 lines. Interestingly, significant anti-proliferative effects of BMP4 induced differentiation were only observed in 3/10 lines and was rescued in only one GSC line by hypoxia, suggesting that these processes are uncoupled. Although hypoxia may directly limit the activity of oxygen-dependent KDMs important in this process, levels of S-2-hydroxyglutarate (S-2HG), an endogenous KDM inhibitor, were also increased in 5/8 GSC lines under hypoxia. Exogenous treatment with S-2HG or a small molecule KDM6 family inhibitor, phenocopied the repressive effects of hypoxia on BMP4 induced differentiation. In patient tumors, hypoxic areas surrounding pseudopalisading necrosis showed high expression of hypoxia markers, and these hypoxia markers were anti-correlated with markers of astrocytic differentiation. Together, these results demonstrate that the hypoxic tumor microenvironment in GBM, through multiple mechanisms limiting oxygen-dependent KDM activity, promote maintenance of the malignant stemness state by inhibiting astrocytic differentiation. This study implicates tumour hypoxia as a key regulator of stemness and a therapeutic target to promote differentiation in GBM. Treatment strategies that target hypoxic cells are urgently needed to overcome these challenges.
Citation Format: Ronald S. Wu, Elisabeth Liedtke, Sheila Mansouri, Samantha Brazier, Paul Guilhamon, Nicole I. Park, Eric Chen, Mathieu Lupien, Daniel D. De Carvalho, Peter G. Dirks, Gelareh Zadeh, Bradley G. Wouters. Hypoxia inhibits BMP4-induced astrocytic differentiation in glioma stem cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3438.