Abstract 4681: Human Cancer Models Initiative (HCMI): A community resource of next-generation cancer models and associated data

The Human Cancer Models Initiative (HCMI) is an international consortium founded by National Cancer Institute (NCI), Cancer Research UK, Wellcome Sanger Institute, and the foundation Hubrecht Organoid Technology. The initiative has generated patient derived Next-generation Cancer Models (NGCMs) from diverse tumor types and subtypes including rare adult and pediatric cancers as a community resource. HCMI addresses deficiencies in traditional cell lines models by collecting patients’ clinical data, as well as the genomes and transcriptomes of the parent tumor, case-matched normal tissue, and the derived next-generation cancer model. NCI’s Center for Cancer Genomics (CCG) sponsors four Cancer Model Development Centers (CMDCs) who are managed by Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Inc. CCG also supports the downstream model development pipeline. The CMDCs are tasked with generating HCMI NGCMs. The model-associated clinical data are submitted to the Clinical Data Center. The models, their associated tumor, and normal samples are processed at the Biospecimen Processing Center (BPC). The nucleic acids isolated at BPC are sent to the Genomic Characterization Centers for molecular characterization. All biospecimen, clinical, and molecular characterization data are quality controlled and submitted to NCI’s Genomic Data Commons (GDC) for the research community. The HCMI models and culture protocols are made available to the research community through a single third-party distributor. The HCMI Searchable Catalog (https://hcmi-searchable-catalog.nci.nih.gov/) is an online resource that allows users to query and identify available models using various data elements including clinical and molecular characterization data, including WGS, WXS, RNA-seq, and methylation array. To date, over 250 HCMI models are available to query on the Searchable Catalog and are available to the research community through the NCI designated model distributor, ATCC. These models have been derived from several cancer types including glioblastoma, colorectal, pediatric, gastroesophageal, pancreatic, and more. Biospecimen, clinical, and molecular characterization data are available for over 100 models at NCI’s GDC, with additional cases released as the data completes the HCMI pipeline. Data, tools, and resources generated by CCG initiatives are made publicly available via the CCG website and GDC. The CCG website also provides available data types, data usage policies and guides to access data (https://www.cancer.gov/about-nci/organization/ccg).

Citation Format: Eva Tonsing-Carter, Rachana Agarwal, Cindy W. Kyi, Julyann Perez-Mayoral, Conrado T. Soria, Jean Claude Zenklusen. Human Cancer Models Initiative (HCMI): A community resource of next-generation cancer models and associated data. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4681.

Abstract 2224: NCI Office of Cancer Genomics: Multidisciplinary genomic research initiatives drive discoveries towards the clinic

The mission of the Office of Cancer Genomics (OCG) at the National Cancer Institute (NCI) is to advance the understanding of cancers to improve clinical outcomes. To accomplish this goal, OCG supports innovative and complementary initiatives that characterize and generate comprehensive genomic datasets from rare and pediatric cancers, develop bioinformatics tools to analyze large-scale genomic datasets and identify the underlying etiology of cancer, generate biologically relevant human tumor-derived next-generation cancer models (NGCMs), and advance technologies to better expand and utilize these NGCMs. The Cancer Genome Characterization Initiative (CGCI) and Therapeutically Applicable Research to Generate Effective Treatments (TARGET) programs aim to identify therapeutic targets and biomarkers in understudied, rare and high-risk adult and pediatric cancers. Clinically annotated tumor and normal matched tissues are characterized by whole-genome, whole-exome and transcriptome sequencing. The research community can access these datasets via the CGCI Data Matrix and TARGET Data Matrix, as well as through NCI's Genomic Data Commons (GDC). The Cancer Target Discovery and Development (CTD2) Network and Human Cancer Models Initiative (HCMI) are functional genomics programs. The CTD2 Network aims to understand tumor development, heterogeneity, drug resistance and metastasis to develop optimal combinations of treatments. The Network develops analytical tools, generates diverse raw/primary datasets that can be accessed through the CTD2 Data Portal and further validates subsets of these data which are shared on the CTD2 Dashboard. The Human Cancer Models Initiative (HCMI) is an international consortium generating patient-derived NGCMs from diverse tumor subtypes including rare adult and pediatric cancers as a community resource. The biospecimen, clinical and molecular characterization data from the derived model, originating tumor and normal tissue can be accessed through NCI's GDC. The HCMI Searchable Catalog allows users to query and identify available models using various data elements including clinical data and masked somatic MAF variants. The Next-Gen Technologies for Next-Gen Cancer Models (NGTfNGCM) program supports the development of technologies and tools that will enhance the use of HCMI and other models in research. The new tools and broader use of NCGMs will contribute to identification of mechanisms of resistance, novel therapeutic targets and development of diagnostic and/or predictive biomarkers for clinical applications. Data, tools, protocols and resources generated by the OCG initiatives are made publicly available via the OCG website (https://ocg.cancer.gov/). The OCG website also provides data usage policies, data access guides, experimental methods, standard operating procedures and helpful links.

Citation Format: Cindy W. Kyi, Pamela C. Birriel, Tanja M. Davidsen, Martin L. Ferguson, Patee Gesuwan, Nicholas B. Griner, Yiwen He, Julyann Perez-Mayoral, Eva Tonsing-Carter, Daniela S. Gerhard. NCI Office of Cancer Genomics: Multidisciplinary genomic research initiatives drive discoveries towards the clinic [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2224.

Abstract 5862: NCI Office of Cancer Genomics supports multidisciplinary genomics research initiatives to advance precision oncology

The National Cancer Institute's (NCI) Office of Cancer Genomics' (OCG) mission is to advance the molecular understanding of cancers to improve clinical outcomes. To accomplish this goal, OCG develops and collaboratively manages molecular characterization and translational genomics research initiatives. OCG currently supports four innovative and complementary initiatives. These programs generate comprehensive genomic datasets, develop bioinformatics tools to analyze these datasets, create biologically-relevant human tumor-derived Next-Generation Cancer Models (NGCMs) and valuable experimental reagents and resources.

The Cancer Genome Characterization Initiative (CGCI) (https://ocg.cancer.gov/programs/cgci) and the Therapeutically Applicable Research to Generate Effective Treatments (TARGET) (https://ocg.cancer.gov/programs/target) are the molecular characterization programs. These programs aim to identify therapeutic targets and biomarkers in understudied, rare, and high-risk adult and pediatric cancers. Clinically annotated tumor and normal matched tissue samples are collected and analyzed by whole-genome, whole-exome, and transcriptome sequencing. The datasets are available to the research community through program-specific Data Matrices: CGCI Data Matrix and TARGET Data Matrix. CGCI and TARGET data are also available through NCI's Genomic Data Commons (GDC)(https://portal.gdc.cancer.gov/). The Pediatric Genomic Data Inventory (PGDI) is a global inventory of pediatric molecular and clinical datasets.

The CTD2 Network (https://ocg.cancer.gov/programs/ctd2) aims to understand cancer metastasis, tumor heterogeneity and drug resistance, and develop optimal combinations of pharmacologic and immunological agents. The CTD2 Network develops bioinformatics tools, generates diverse raw/primary datasets that can be accessed through the CTD2 Data Portal and further validates subsets of these data listed at the CTD2 Dashboard. The Human Cancer Models Initiative (HCMI) (https://ocg.cancer.gov/programs/HCMI) is an international consortium that is generating human tumor-derived NGCMs from diverse tumor subtypes including rare and pediatric cancers. The models, together with related clinical and genomic data, are available as a community resource. The HCMI Searchable Catalog allows users to search the list of available models and associated clinical and molecular data. The clinical and molecular data are stored at the NCI's GDC.

Data, analytical tools, and resources generated by OCG initiatives are made publicly available to further the collaborative goal of enabling precision oncology to improve patient care. The OCG website (https://ocg.cancer.gov/) also provides data usage policies, guides to access data, experimental methods, standard operating procedures, and educational and helpful links for the community.

Citation Format: Cindy W. Kyi, Pamela C. Birriel, Tanja M. Davidsen, Martin L. Ferguson, Patee Gesuwan, Nicholas B. Griner, Yiwen He, Lauren M. Hurd, Subhashini Jagu, Eva Tonsing-Carter, Daniela S. Gerhard. NCI Office of Cancer Genomics supports multidisciplinary genomics research initiatives to advance precision oncology [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 5862.

Glucocorticoid receptor modulation decreases ER-positive breast cancer cell proliferation and suppresses wild-type and mutant ER chromatin association

Background

Non-ER nuclear receptor activity can alter estrogen receptor (ER) chromatin association and resultant ER-mediated transcription. Consistent with GR modulation of ER activity, high tumor glucocorticoid receptor (GR) expression correlates with improved relapse-free survival in ER+ breast cancer (BC) patients.

Methods

In vitro cell proliferation assays were used to assess ER-mediated BC cell proliferation following GR modulation. ER chromatin association following ER/GR co-liganding was measured using global ChIP sequencing and directed ChIP analysis of proliferative gene enhancers.

Results

We found that GR liganding with either a pure agonist or a selective GR modulator (SGRM) slowed estradiol (E2)-mediated proliferation in ER+ BC models. SGRMs that antagonized transcription of GR-unique genes both promoted GR chromatin association and inhibited ER chromatin localization at common DNA enhancer sites. Gene expression analysis revealed that ER and GR co-activation decreased proliferative gene activation (compared to ER activation alone), specifically reducing CCND1, CDK2, and CDK6 gene expression. We also found that ligand-dependent GR occupancy of common ER-bound enhancer regions suppressed both wild-type and mutant ER chromatin association and decreased corresponding gene expression. In vivo, treatment with structurally diverse SGRMs also reduced MCF-7 Y537S ER-expressing BC xenograft growth.

Conclusion

These studies demonstrate that liganded GR can suppress ER chromatin occupancy at shared ER-regulated enhancers, including CCND1 (Cyclin D1), regardless of whether the ligand is a classic GR agonist or antagonist. Resulting GR-mediated suppression of ER+ BC proliferative gene expression and cell division suggests that SGRMs could decrease ER-driven gene expression.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1164-6) contains supplementary material, which is available to authorized users.

Abstract 4341: NCI Office of Cancer Genomics: Promoting multidisciplinary research to translate findings into the clinic and advance precision oncology

The mission of the National Cancer Institute’s (NCI) Office of Cancer Genomics (OCG) is to advance the molecular understanding of cancers in order to improve clinical outcomes through precision medicine. Although vast amounts of genomic data are available for many types of cancers, identifying genetic alterations in rare and pediatric cancers is still a challenge. Efficient bioinformatics tools to analyze, manage, store, and access data are also necessary for the research community. To develop effective and targeted treatments, clinically accurate genotypic and phenotypic research models are much needed. OCG’s programs focus on addressing these challenges through multidisciplinary, collaborative research efforts.

The four initiatives of OCG support research on structural, functional, and translational genomics, as well as development of next-generation cancer models. The Cancer Genome Characterization Initiative (CGCI) and the Therapeutically Applicable Research to Generate Effective Treatments (TARGET) programs use transcriptomic, genomic, and epigenomic approaches to examine genetic alterations between various tumors and matched normal tissues. CGCI projects focus on HIV-associated and rare cancers such as Burkitt lymphoma, while TARGET focuses on high-risk childhood cancers. The goals of these programs are to attain insights into key mutations that drive tumors and genetic abnormalities specific to cancer subtypes and to develop effective and less toxic therapies for patients. CGCI and TARGET data are available to the research community through data matrices on the OCG website. OCG also recently launched the Pediatric Genomic Data Inventory (PGDI) as a new resource for investigators to access molecular characterization data.The Cancer Target Discovery and Development (CTD2) Network advances cancer research by bridging the knowledge gap between cancer genomics and precision oncology. The Network aims to understand the cancer metastasis, tumor heterogeneity, and drug resistance to develop optimal combinations of small-molecules or immunotherapy with small molecules. As a community resource program, the CTD2 Network develops and provides access to data, tools, methods, and reagents through the Data Portal and the Dashboard. The Human Cancer Models Initiative (HCMI) is an international consortium that is generating novel human tumor-derived culture models from a wide variety of cancer types including rare and understudied cancers. The models, together with related clinical and genomic data, will be available as a resource to the world-wide research community.

OCG’s policies on data usage, as well as guides to accessing data, are explained on the OCG website (https://ocg.cancer.gov/). Researchers, potential collaborators, and interested members of the public are encouraged to visit the OCG webpages or contact OCG at ocg@mail.nih.gov.

Citation Format: Cindy W. Kyi, Pamela C. Birriel, Tanja M. Davidsen, Martin L. Ferguson, Patee Gesuwan, Nicholas B. Griner, Yiwen He, Subhashini Jagu, Eva Tonsing-Carter, Daniela S. Gerhard. NCI Office of Cancer Genomics: Promoting multidisciplinary research to translate findings into the clinic and advance precision oncology [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 4341.

Abstract 2541: Combined androgen and glucocorticoid receptor (AR/GR) activity drives TNBC progression

Background: A recent effort to distinguish early-stage TNBC based on outcome and to expose driver pathways using gene profiling/cluster analysis divided TNBC into four subtypes- basal-like, mesenchymal, immunomodulatory, and luminal androgen receptor (LAR). The clinical AR+ TNBC subtype (>10% AR by IHC) comprises up to 35% of metastatic disease. The discovery of this TNBC subtype and the concomitant development of potent new anti-androgens for prostate cancer have led to several clinical trials evaluating AR antagonists in TNBC. In parallel, glucocorticoid receptor (GR) expression and activation have been shown to mediate anti-apoptotic gene expression in TNBC. However, to our knowledge, no one has examined the coordinate expression of GR and AR activity and the potential crosstalk downstream of dual GR and AR activation. We hypothesized that AR/GR cooperative gene expression pathways may induce TNBC therapy resistance and tumor progression. Methods and Results: We analyzed GR+ TNBC primary tumor gene expression from TCGA samples and found a wide range of AR expression. To examine whether GR-associated gene expression differed in high versus low AR+ TNBC, we divided TCGA TNBC primary tumors (N=123) at the AR median into “high” versus “low” AR expression. We then identified relative GR target gene expression levels in those genes identified from a previous TNBC meta-analysis. Invasion, motility and proliferation pathways were found to be most significantly expressed among GR-associated genes in AR high TNBC (top 5 significant pathways). Similarly, we found that GR and AR co-activation in AR+ MDA-MB-453 TNBC cells significantly increased cell migration compared to GR or AR activation alone. In addition, when MDA-MB-453 cells were exposed to the AR antagonist enzalutamide (enza) for more than 30 days (long-term, LT), the magnitude of increase in cell migration following GR activation increased, suggesting that increased GR activity may compensate for long-term AR blockade. Furthermore, long-term enza exposure (LTenza) in AR+ MFM-223 and MDA-MB-453 cells resulted in increased GR mRNA and protein levels. The magnitude of GR-mediated target gene expression was also significantly increased in LTEnza versus control-treated cells. In vivo, LTenza-treated MDA-MB-453 xenografts were relatively insensitive to paclitaxel chemotherapy treatment, consistent with increased GR activity compared to control cells. Conclusions: We conclude that coordinate GR and AR expression in TNBC contributes to a particularly poor outcome in TNBC. Downstream AR/GR gene expression favoring cell survival and invasive phenotypes may contribute to this outcome. Consideration of dual AR/GR inhibition in TNBC may increase the effectiveness of anti-androgen therapy.

Citation Format: Deniz N. Dolcen, Eva Tonsing-Carter, Ryan Harkless, Caroline Kim, Kathleen Bowie, Gini Fleming, Suzanne Conzen. Combined androgen and glucocorticoid receptor (AR/GR) activity drives TNBC progression [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 2541.

Abstract P3-05-09: Glucocorticoid receptor modulation affects ER+ breast cancer cell proliferation

Early-stage ER+ breast cancer with high tumor glucocorticoid receptor (GR) expression is associated with improved long term relapse-free survival compared to tumors with low GR expression. In addition, activation of GR inhibits estradiol-mediated ER+ BC cell proliferation. This finding led us to hypothesize that GR and ER engage in nuclear receptor cross-talk to affect pro-proliferative gene expression, thus contributing to a better outcome in ER+/GR+ BC patients. To better understand the mechanisms by which ER/GR co-activation contributes to this more indolent phenotype, we performed ChIP-sequencing and gene expression analyses in ER+/GR+ BC cell lines (MCF-7 and T47D).

We found that co-activation of ER and GR led to decreased ER+ BC cell proliferation in vitro. Furthermore, following co-activation of ER/GR, there was decreased gene expression of key cell cycle genes (e.g. CDK6, CDK2 and CCNE1) compared to ER-activation alone. Studies are underway to determine if this decrease in gene expression is associated with less CDK activity as well as a slowing of cell cycle progression.

We also wanted to know if GR activation with a pure agonist versus a mixed GR modulator was required for decreasing ER-mediated cell proliferation. Based on our previous work (DC West et al. MCR 2016), we hypothesized that ligand-mediated GR activation could be working by preventing access of ER to regulatory regions of pro-proliferative genes rather than causing direct GR agonist-mediated gene expression. To examine this question, we used a GR modulator, mifepristone (expected to alter ER-mediated gene expression indirectly). Indeed we found that a GR modulator also reduced ER-mediated cell proliferation. We are currently testing the mechanisms by which GR modulators affect estradiol-mediated cell cycle gene expression.

Taken together, these studies suggest that modulation of GR activity could be an effective approach to decrease ER+ tumor cell proliferation. Xenograft studies are underway to examine whether the addition of GR modulation to tamoxifen will improve tumor shrinkage compared to tamoxifen alone.

Citation Format: Tonsing-Carter E, Bowie KR, West DC, Harkless RV, Hernandez KM, Conzen SD. Glucocorticoid receptor modulation affects ER+ breast cancer cell proliferation [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-05-09.

Combination therapy in a xenograft model of glioblastoma: enhancement of the antitumor activity of temozolomide by an MDM2 antagonist

OBJECTIVE Improvement in treatment outcome for patients with glioblastoma multiforme (GBM) requires a multifaceted approach due to dysregulation of numerous signaling pathways. The murine double minute 2 (MDM2) protein may fulfill this requirement because it is involved in the regulation of growth, survival, and invasion. The objective of this study was to investigate the impact of modulating MDM2 function in combination with front-line temozolomide (TMZ) therapy in GBM. METHODS The combination of TMZ with the MDM2 protein-protein interaction inhibitor nutlin3a was evaluated for effects on cell growth, p53 pathway activation, expression of DNA repair proteins, and invasive properties. In vivo efficacy was assessed in xenograft models of human GBM. RESULTS In combination, TMZ/nutlin3a was additive to synergistic in decreasing growth of wild-type p53 GBM cells. Pharmacodynamic studies demonstrated that inhibition of cell growth following exposure to TMZ/nutlin3a correlated with: 1) activation of the p53 pathway, 2) downregulation of DNA repair proteins, 3) persistence of DNA damage, and 4) decreased invasion. Pharmacokinetic studies indicated that nutlin3a was detected in human intracranial tumor xenografts. To assess therapeutic potential, efficacy studies were conducted in a xenograft model of intracranial GBM by using GBM cells derived from a recurrent wild-type p53 GBM that is highly TMZ resistant (GBM10). Three 5-day cycles of TMZ/nutlin3a resulted in a significant increase in the survival of mice with GBM10 intracranial tumors compared with single-agent therapy. CONCLUSIONS Modulation of MDM2/p53-associated signaling pathways is a novel approach for decreasing TMZ resistance in GBM. To the authors' knowledge, this is the first study in a humanized intracranial patient-derived xenograft model to demonstrate the efficacy of combining front-line TMZ therapy and an inhibitor of MDM2 protein-protein interactions.

Abstract A26: Inhibition of MDM2 and AKT signaling networks synergize to activate Forkhead box O-class transcription factors and promote cell death in mutant p53 GBM cells

A multi-targeted approach will be necessary to eradicate glioblastoma multiforme (GBM) cells due to the immense genetic heterogeneity associated with GBM. Mouse double minute-2 (MDM2) regulates multiple signaling pathways and is a promising therapeutic target in GBM. In wild type (wt) p53 cells, MDM2 binds to wtp53, ubiquitinates it, and negatively regulates p53-mediated downstream events. In wtp53 and mutant (mt) p53 cells, MDM2 binds to and sequesters p73α thereby blocking p73α-mediated signaling. Our objective in the present studies was to determine if the p73α-MDM2 axis could be exploited to increase death of mtp53 GBM cells. We utilized MDM2 antagonists nutlin3a or RG7112 to block protein-protein interactions between MDM2-p53 and MDM2-p73α. In a panel of GBM cell lines, TMZ resistance was reduced in both wt53 and mt53 cells in the presence of MDM2 antagonists. In mtp53 cells, siRNA knockdown of p73α indicated that sensitivity to treatment was dependent on p73α levels. Isobologram analysis indicated that while dose-ratios of TMZ to MDM2 antagonists were additive to synergistic in inhibiting growth of wtp53 GBM cells, this was not the case in mtp53 GBM cells (SF118, GBM43, gain-of-function-mtp53 R273H U373 and MHBT32). Analysis of intracellular targets in mtp53 GBM cells exposed to TMZ and MDM2 antagonists indicated that p73α and MDM2 expression increased by 24 hours post-treatment. In addition, AKT activity was increased or sustained in mtp53 GBM cells following treatment with TMZ in the absence or presence of MDM2 antagonists. Since increased AKT activity may render cells resistant to therapy, the AKT inhibitor GDC0068 was evaluated in combination with TMZ and RG7112. As a measure of AKT-downstream target modulation, phosphorylation status of the Forkhead box O-class (FoxO) transcription factors (TFs) was determined. In the non-phosphorylated state, FoxO TFs upregulate expression of proteins involved in cell-death pathways. While phospho-FoxO1/FoxO3a TFs were increased in TMZ/RG7112-treated mtp53 GBM cells compared to controls, it was decreased in GDC0068-, TMZ/GDC0068- and TMZ/RG7112/GDC0068-treated mtp53 GBM cells which is consistent with inactivation of AKT and activation of FoxO TFs. Isobologram analysis of mtp53 GBM cell growth indicated that combination RG7112 and GDC0068 inhibited growth in a synergistic manner even in the absence of TMZ. For in vivo studies, an intermittent dosing regimen of TMZ/RG7112/GDC0068 was developed to avoid normal tissue toxicity. GBM43 flank tumor growth was significantly inhibited in mice with tumors treated with RG7112/GDC0068 and inhibited to a larger extent by the triple combination TMZ/RG7112/GDC0068 compared to vehicle and single-agent exposure (n=9-10 mice per group; single agent vs GDC0068/RG7112 or TMZ/RG7112/GDC0068, p<0.05). The present data indicate that targeting the p73α-MDM2 and AKT-FoxO signaling networks inhibit mtp53 GBM cell growth and with an appropriate dosing schedule can be utilized in vivo with an acceptable toxicity profile.

Citation Format: Mohammad Reza Saadatzadeh, Haiyan Wang, Jixin Ding, Barbara J. Bailey, Eva Tonsing-Carter, Shanbao Cai, Nimita Dave, Harlan E. Shannon, Aaron Cohen- Gadol, Karen E. Pollok. Inhibition of MDM2 and AKT signaling networks synergize to activate Forkhead box O-class transcription factors and promote cell death in mutant p53 GBM cells. [abstract]. In: Proceedings of the AACR Special Conference: Advances in Brain Cancer Research; May 27-30, 2015; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2015;75(23 Suppl):Abstract nr A26.

Potentiation of Carboplatin-Mediated DNA Damage by the Mdm2 Modulator Nutlin-3a in a Humanized Orthotopic Breast-to-Lung Metastatic Model

Triple-negative breast cancers (TNBC) are typically resistant to treatment, and strategies that build upon frontline therapy are needed. Targeting the murine double minute 2 (Mdm2) protein is an attractive approach, as Mdm2 levels are elevated in many therapy-refractive breast cancers. The Mdm2 protein-protein interaction inhibitor Nutlin-3a blocks the binding of Mdm2 to key signaling molecules such as p53 and p73α and can result in activation of cell death signaling pathways. In the present study, the therapeutic potential of carboplatin and Nutlin-3a to treat TNBC was investigated, as carboplatin is under evaluation in clinical trials for TNBC. In mutant p53 TMD231 TNBC cells, carboplatin and Nutlin-3a led to increased Mdm2 and was strongly synergistic in promoting cell death in vitro. Furthermore, sensitivity of TNBC cells to combination treatment was dependent on p73α. Following combination treatment, γH2AX increased and Mdm2 localized to a larger degree to chromatin compared with single-agent treatment, consistent with previous observations that Mdm2 binds to the Mre11/Rad50/Nbs1 complex associated with DNA and inhibits the DNA damage response. In vivo efficacy studies were conducted in the TMD231 orthotopic mammary fat pad model in NOD.Cg-Prkdc(scid)Il2rg(tm1Wjl)/SzJ (NSG) mice. Using an intermittent dosing schedule of combined carboplatin and Nutlin-3a, there was a significant reduction in primary tumor growth and lung metastases compared with vehicle and single-agent treatments. In addition, there was minimal toxicity to the bone marrow and normal tissues. These studies demonstrate that Mdm2 holds promise as a therapeutic target in combination with conventional therapy and may lead to new clinical therapies for TNBC.

Abstract 5196: Histologic and whole slide quantitative image analysis of lung metastases in a mouse breast cancer model using carboplatin and Nutlin 3A alone and in combination

Breast cancer will affect 1 in 8 women in their lifetime. Approximately 20-30% of all breast cancer cases become metastatic. This study was designed to evaluate the effect of tumor met knockdown with individual and combination drug therapy. In this mouse model, with 3 per group, we used the following chemotherapeutic agents: a vehicle control, carboplatin (20mg/kg i.p.), Nutlin-3a (200mg/kg p.o.) and a combination group with the same doses. Nutlin-3 is a small-molecule inhibitor that binds to the p53-binding pocket of MDM2, and activates the p53 pathway. This has been shown to be effective in mouse models of cancer that have a wild-type p53, including prostate, leukemia and multiple myeloma.

The lungs were removed and examined for metastatic lung lesions, fixed in 10% neutral buffered formalin (NBF), processed into a paraffin block, microtomed, and slides were stained with H&E. Ki67 immunostain was performed to clearly define the met lesions and the whole slide was imaged with an Aperio Digital Imaging System. The Image Scope positive pixel algorithm was used to quantitate the met lesions in the lungs. The data revealed upon drug treatment the number of mets in the lungs were unchanged in the carboplatin and nutlin-3a individual treatment groups compared to the vehicle group. The lungs in the combination group had the lowest number of tumors with both visual and quantitative image analysis compared to the vehicle control group.

The Aperio automated positive pixel count for Ki67 immunostain was consistent with the H&E pathology read. The values decreased with combination treatment (control vs. combination 20mg/kg carboplatin, 200mg/kg nutlin 3a) and were 6% and 1.7% respectively.

It was concluded that mice treated with carboplatin and Nutlin-3a combination therapy had fewer metastatic breast cancer mets in the lungs. The individual drug doses were low compared to previous studies and did not have an effect as was expected. This finding suggests that the combination of a traditional chemotherapy with a small protein inhibitor could inhibit the spread of metastatic breast cancer.

Citation Format: Margaret Strack, Eva Tonsing-Carter, Tony Sinn, Tiaishia Spragin, Kacie Peterson, Barbara Bailey, Karen Pollok, George Sandusky. Histologic and whole slide quantitative image analysis of lung metastases in a mouse breast cancer model using carboplatin and Nutlin 3A alone and in combination. [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 5196. doi:10.1158/1538-7445.AM2015-5196

Abstract 1680: Modulation of MDM2 in context of DNA damage enhances cell death in a metastatic breast-to-lung xenograft model

Metastatic breast cancer is highly refractive to current treatment strategies, and new multi-targeted treatments need to be elucidated. In metastatic disease, inhibiting key protein-protein interactions with the murine double minute 2 (MDM2) could be beneficial for developing new treatment modalities since this signaling pathway is a critical regulatory point in cancer progression. Inhibition of protein binding to the hydrophobic pocket of MDM2 by Nutlin-3a can activate pro-apoptotic proteins such p73 and E2F1 as well as decrease pro-angiogenic Hif-1α. Since the DNA damaging agent carboplatin is currently being studied in clinical trials of triple-negative breast cancers (TNBCs), our objective was to evaluate the effects of carboplatin and Nutlin-3a in combination in TNBC in a mutant p53 background. Using a TNBC cell line TMD231 derived from the MDA-MB-231 human breast cancer cell line, we performed combination studies using different ratios of carboplatin to Nutlin-3a in vitro to evaluate the range of carboplatin-mediated DNA damage required to obtain synergism with inhibition of MDM2 function. A fixed ratio of 1:1 carboplatin:Nutlin-3a was strongly synergistic with a combination index of <0.5. In cell proliferation assays there was increased sensitivity to the drugs when given in combination (p<0.05). TMD231 cells implanted into the mammary fat pad of NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice showed enhanced tumor growth, and metastasis was evident in the lungs. Dose-finding studies were performed to determine an optimal carboplatin dosing schema. NSG mice were randomized based on fluorescent imaging of E2-crimson expressing TMD231 cells allowing for a sensitive measurement of early tumor burden. Following Nutlin-3a and carboplatin combination treatment in vivo, there was a statistically significant reduction in tumor volume and lung metastases compared to vehicle and single drug treated mice (p<0.001). Following Kaplan-Meier analysis, the combination treated mice had a significant increase in survival, (54.3±1.5 days) compared to the vehicle (39.3±0.6 days) and each single drug (Nutlin-3a: 39±1 and carboplatin: 47.5±1.8 days) (p<0.001). While there was a decrease in bone-marrow cellularity, this did not lead to bone-marrow aplasia, and body weights recovered to normal levels within 7 days post-treatment. Pharmacodynamic studies are ongoing to further understand at the molecular level how the DNA damage response and repair is modulated by MDM2 resulting in a robust synergistic response. These studies will lead to a better understanding of how to potentiate DNA damage and may lead to new clinical therapies in the future for metastatic breast cancer.

Citation Format: Eva Tonsing-Carter, Harlan E. Shannon, Barbara J. Bailey, Anthony L. Sinn, Kacie M. Peterman, Lindsey D. Mayo, Karen E. Pollok. Modulation of MDM2 in context of DNA damage enhances cell death in a metastatic breast-to-lung xenograft model. [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 1680. doi:10.1158/1538-7445.AM2014-1680

Abstract 4639: Blockade of MDM2-mediated signaling in context of DNA damage increases E2F1 expression and enhances cell death in triple-negative breast cancer cells

Metastatic breast cancer is highly refractive to current treatment strategies and new multi-targeted treatments need to be elucidated. In metastatic disease, blocking key protein-protein interactions with the murine double minute 2 (MDM2) could be beneficial for developing new treatment modalities since this signaling pathway is a critical regulatory point in cancer progression. Inhibition of protein binding to the hydrophobic pocket of MDM2 by Nutlin-3a can result in increases in pro-apoptotic proteins such as p53, p73, and E2F1. Since the DNA damaging agent carboplatin is being studied in clinical trials of triple-negative breast cancers (TNBCs), our objective was to evaluate the effects of carboplatin and Nutlin-3a in combination in TNBC cancer in a mutant p53 background. We utilized TMD231 breast cancer cells derived from the MDA-MB-231 human TNBC cancer line. TMD231 cells are highly metastatic in vivo and readily metastasize from the primary tumor to the lung. Combination studies were performed using different ratios of carboplatin to Nutlin-3a to evaluate the range of carboplatin-mediated DNA damage required to obtain synergism with inhibition of MDM2 function. A fixed ratio of 1:1 carboplatin:Nutlin-3a was strongly synergistic with a combination index of < 0.5. In cell proliferation assays there was increased sensitivity to the drugs when given together and a significant reduction in number of colonies in colony formation assays. In order to understand how DNA damage and inhibition of MDM2 signaling leads to enhanced cell death, dose-response and time-course studies were performed. Western analyses demonstrated increases in E2F1 when treated with carboplatin and Nutlin-3a alone, and a time-dependent increase in E2F1 following combination treatment at a fixed 1:1 ratio. Following DNA damage, E2F1 has been shown to promote the transcription of pro-apoptotic genes and repression of survival genes once E2F1 is released from interaction with Rb. Here, E2F1 levels correlated with Rb phosphorylation at serine 780, a phosphorylation site which inhibits binding of E2F1 to Rb. The E3 ubiquitin ligase Itch, which ubiquitinates p73, increased following treatment with carboplatin alone or in combination with Nutlin-3a in a dose- and time-dependent manner but appeared not to regulate p73 since p73 levels remained unchanged following combination treatment. Studies are ongoing to further understand how modulation of DNA damage by blockade of MDM2 results in a robust synergistic response and how upregulation of E2F1 affects downstream targets. The impact of the combination of DNA damaging carboplatin and MDM2 blockade by Nutlin-3a on DNA repair kinetics is currently being evaluated in an orthotopic TMD231 model. These studies will lead to a better understanding of how to potentiate DNA damage and may lead to new clinical therapies in the future.

Citation Format: Eva Tonsing-Carter, Harlan E. Shannon, Barbara J. Bailey, Lindsey D. Mayo, Karen E. Pollok. Blockade of MDM2-mediated signaling in context of DNA damage increases E2F1 expression and enhances cell death in triple-negative breast cancer cells. [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 4639. doi:10.1158/1538-7445.AM2013-4639

Abstract 1409: Real-time in vivo imaging for sensitive detection of primary and metastatic disease in a human breast-to-lung orthotopic model

Orthotopic mouse models of human disease are absolutely essential for validating therapeutic targets and assessing efficacy of emerging therapies. Early detection of in vivo tumor growth is a critical benchmark in humanized mouse models, for it reveals tumor take at a time of reasonable tumor burden. To develop an optimal mouse model of human metastatic breast cancer, we utilized TMD231 breast cancer cells (derived from MDA-MB-231) that have a high propensity to metastasize to the lung. TMD231 tumor take and improved kinetics of tumor growth and metastatic foci formation appeared more consistently and at a faster rate in NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) versus NOD/SCID mice. For in vivo detection of small tumor burden at study initiation and metastatic lesions over time, TMD231 breast cancer cells were transduced with lentiviral vectors that express either mCherry or E2-Crimson fluorescent proteins (FPs). Flow cytometric analysis indicated transduction efficiencies for the lentiviral vectors expressing mCherry and E2-Crimson in the TMD231 cells was >99% and >80%, respectively. TMD231 cells expressing either the mCherry or E2-Crimson FPs were implanted into NSG mice and were imaged weekly using the Optix MX3 (ART Technologies, Montreal, Canada) to assess to what degree fluorescently tagged cells could be longitudinally and non-invasively visualized at primary and secondary sites within the NSG mice. While photon emission from TMD231 tumors expressing mCherry could be detected, levels were low and did not correlate with tumor growth overtime. In contrast, high levels of photon emission were detected using TMD231-E2-Crimson cells. Non-palpable tumors expressing the E2-Crimson FP could be detected in NSG mice as early as 7 days post-implant into the mammary fat pad. Additionally, metastatic foci in the lung were detected via optical imaging as early as 2-3 weeks post-implant. Following imaging analysis, TMD231-E2-Crimson tumor size correlated to increased fluorescent intensity, tumor depth, and fluorescent concentration longitudinally. In vitro imaging analysis of TMD231-E2-Crimson cells confirmed the in vivo imaging results showing a linear relationship between cell number and fluorescent intensity. The discrepancy in the in vivo detection of mCherry versus E2-Crimson proteins is most likely due to the greater brightness of E2-Crimson, as well as the closer alignment of the excitation/emission spectra of E2-Crimson with the laser/filter set of the Optix MX3 imaging system. To confirm optical imaging results, H&E staining indicated the presence of numerous foci in the lungs post-mortem. The optimized orthotopic model described here is being used to investigate mechanisms of metastasis as well as novel therapeutic strategies in metastatic breast cancer.

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 1409. doi:1538-7445.AM2012-1409