Clinically relevant inflammatory breast cancer patient-derived xenograft-derived ex vivo model for evaluation of tumor-specific therapies

Inflammatory breast cancer (IBC) is a rare and aggressive presentation of invasive breast cancer with a 62% to 68% 5-year survival rate. It is the most lethal form of breast cancer, and early recognition and treatment is important for patient survival. Like non-inflammatory breast cancer, IBC comprises multiple subtypes, with the triple-negative subtype being overrepresented. Although the current multimodality treatment regime of anthracycline- and taxane-based neoadjuvant therapy, surgery, and radiotherapy has improved the outcome of patients with triple-negative IBC, overall survival continues to be worse than in patients with non-inflammatory locally advanced breast cancer. Translation of new therapies into the clinics to successfully treat IBC has been poor, in part because of the lack of in vitro preclinical models that can accurately predict the response of the original tumor to therapy. We report the generation of a preclinical IBC patient-derived xenograft (PDX)-derived ex vivo (PDXEx) model and show that it closely replicates the tissue architecture of the original PDX tumor harvested from mice. The gene expression profile of our IBC PDXEx model had a high degree of correlation to that of the original tumor. This suggests that the process of generating the PDXEx model did not significantly alter the molecular signature of the original tumor. We demonstrate a high degree of similarity in drug response profile between a PDX mouse model and our PDXEx model generated from the same original PDX tumor tissue and treated with the same panel of drugs, indicating that our PDXEx model had high predictive value in identifying effective tumor-specific therapies. Finally, we used our PDXEx model as a platform for a robotic-based high-throughput drug screen of a 386-drug anti-cancer compound library. The top candidates identified from this drug screen all demonstrated greater therapeutic efficacy than the standard-of-care drugs used in the clinic to treat triple-negative IBC, doxorubicin and paclitaxel. Our PDXEx model is simple, and we are confident that it can be incorporated into a PDX mouse system for use as a first-pass screening platform. This will permit the identification of effective tumor-specific therapies with high predictive value in a resource-, time-, and cost-efficient manner.

Anti-Cryptococcus Phenalenones and Cyclic Tetrapeptides from Auxarthron pseudauxarthron

Auxarthrones A-E (1-5), five new phenalenones, and two new naturally occurring cyclic tetrapeptides, auxarthrides A (7) and B (8), were obtained from three different solvent extracts of cultures of the coprophilous fungus Auxarthron pseudauxarthron. Auxarthrones C (3) and E (5) possess an unusual 7a,8-dihydrocyclopenta[a]phenalene-7,9-dione ring system that has not been previously observed in natural products. Formation of 1-5 was found to be dependent on the solvent used for culture extraction. The structures of these new compounds were elucidated primarily by analysis of NMR and MS data. Auxarthrone A (1) was obtained as a mixture of chromatographically inseparable racemic diastereomers (1a and 1b) that cocrystallized, enabling confirmation of their structures by X-ray crystallography. The absolute configurations of 7 and 8 were assigned by analysis of their acid hydrolysates using Marfey's method. Compound 1 displayed moderate antifungal activity against Cryptococcus neoformans and Candida albicans, but did not affect human cancer cell lines.

Abstract 473: PRKRA/PACT expression promotes chemoresistance in mucinous ovarian cancer

Purpose: To investigate the mechanisms of chemotherapy resistance and developing strategies to enhance therapeutic responses in mucinous ovarian cancer (MOC).

Experimental design: We carried out a kinome-based siRNA screen using human MOC to identify novel targets to enhance the efficacy of chemotherapy in MOC cell lines. In vitro and in vivo validation studies were carried out using MOC models. We specifically interrogated the role of PRKRA in MOC based on our screen results.

Results: Among the 939 genes in the screen, we focused on PRKRA/PACT because it was one of the top 5 target genes that exhibited the greatest extent of synthetic lethality in the target gene-siRNA plus oxaliplatin group relative to the target gene-siRNA group. The combination of oxaliplatin plus siPRKRA treatment resulted in significantly reduced cell viability compared with oxaliplatin plus control siRNA in RMUG-L-ip1 or RMUG-S-ip1 MOC cells (p<0.001), while knockdown of PRKRA did not result in a significant change in cell viability compared with the control. We also observed a 2.1-fold increase in cell apoptosis in vitro after treatment with oxaliplatin plus siPRKRA in both MOC cells (p<0.05). Using orthotopic mouse models of MOC, we observed an 88% reduction (p<0.01) in tumor weight and 75% reduction in the number of tumor nodules (p<0.01) in the siPRKRA plus oxaliplatin group compared with the control siRNA plus oxaliplatin group. PRKRA expression in human MOC was significantly higher relative to high-grade serous ovarian tumors as evaluated by immunohistochemistry. Furthermore, we found that the interaction between PACT and Dicer can regulate maturation of microRNA. In particular, mature-miR-515-3p was found to be inhibited by the interaction between PACT and Dicer. Expression of miR-515-3p promotes chemosensitivity in MOC by targeting the mRNA of the anti-apoptotic gene AXL.

Conclusion: The PRKRA/PACT axis represents an important therapeutic opportunity in MOC for enhancing oxaliplatin efficacy.

Citation Format: Takeshi Hisamatsu, Michael McGuire, Sherry Y. Wu, Rajesha Rupaimoole, Sunila Pradeep, Kyunghee Noh, Justyna Filant, Jean M. Hansen, Yasmin Lyons, Kshipra M. Gharpure, Archana S. Nagaraja, Lingegowda S. Mangala, Takashi Mitamura, Cristian Rodriguez-Aguayo, Geoffrey A. Bartholomeusz, Cristina Ivan, Ju-Seong Lee, Koji Matsuo, Michael Frumovitz, Kwong K. Wong, Gabriel Lopez-Berestein, Anil K. Sood. PRKRA/PACT expression promotes chemoresistance in mucinous ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 473. doi:10.1158/1538-7445.AM2017-473

Benzophenone and Fimetarone Derivatives from the Coprophilous Fungus Delitschia confertaspora

Studies of the genome-sequenced, flutimide-producing coprophilous fungus Delitschia confertaspora (ATCC 74209), originally obtained from a sample of rock hyrax (Procavia capensis) dung collected in Namibia, led to the discovery of three new highly aromatic natural products named delicoferones A-B (1-2) and fimetarone B (3). The new benzophenone derivatives 1 and 2 have a somewhat unusual skeleton that incorporates three aromatic rings linked via two ketone carbonyl groups, while 3 contains a spiro[chroman-3,7'-isochromene]-4,6'(8'H) skeleton reported only once previously. The structures of these compounds were assigned mainly by analysis of 2D NMR and HRESITOFMS data.

Synthesis and cytotoxic activity of novel A-ring cleaved ursolic acid derivatives in human non-small cell lung cancer cells

Ursolic acid (UA) is a pentacyclic triterpenoid with recognized anticancer properties. We prepared a series of new A-ring cleaved UA derivatives and evaluated their antiproliferative activity in non-small cell lung cancer (NSCLC) cell lines using 2D and 3D culture models. Compound 17, bearing a cleaved A-ring with a secondary amide at C3, was found to be the most active compound, with potency in 2D systems. Importantly, even in 3D systems, the effect was maintained albeit a slight increase in the IC50. The molecular mechanism underlying the anticancer activity was further investigated. Compound 17 induced apoptosis via activation of caspase-8 and caspase-7 and via decrease of Bcl-2. Moreover, induction of autophagy was also detected with increased levels of Beclin-1 and LC3A/B-II and decreased levels of mTOR and p62. DNA synthetic capacity and cell cycle profiles were not affected by the drug, but total RNA synthesis was modestly but significantly decreased. Given its activity and mechanism of action, compound 17 might represent a potential candidate for further cancer research.

H19 Noncoding RNA, an Independent Prognostic Factor, Regulates Essential Rb-E2F and CDK8-β-Catenin Signaling in Colorectal Cancer

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High H19 expression in primary tumors is an independent predictor of short overall survival in CRC patients.

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RB1-E2F and CDK8-β-catenin signaling are essential in mediating the oncogenic activity of H19 in CRC.

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Combined analysis of H19 and its targets further improved the prediction power on overall survival of CRC patients.

Long noncoding RNAs (lncRNAs) are transcripts at least 200 nucleotides long that do not code for proteins. The clinical relevance of lncRNAs in colorectal cancer (CRC) is largely unknown. Here we identified that H19 expression in primary tumors is an independent prognostic predictor of poor prognosis of CRC patients and further proved its oncogenic role. To characterize the mechanisms, we profiled gene expression changes following H19 modulation in CRC cell lines and analyzed gene expression association in clinical datasets. Our data revealed important cancer-signaling pathways, including the RB1-E2F and the CDK8-β-catenin signaling, underlying H19 function.

The clinical significance of long noncoding RNAs (lncRNAs) in colorectal cancer (CRC) remains largely unexplored. Here, we analyzed a large panel of lncRNA candidates with The Cancer Genome Atlas (TCGA) CRC dataset, and identified H19 as the most significant lncRNA associated with CRC patient survival. We further validated such association in two independent CRC cohorts. H19 silencing blocked G1-S transition, reduced cell proliferation, and inhibited cell migration. We profiled gene expression changes to gain mechanism insight of H19 function. Transcriptome data analysis revealed not only previously identified mechanisms such as Let-7 regulation by H19, but also RB1-E2F1 function and β-catenin activity as essential upstream regulators mediating H19 function. Our experimental data showed that H19 affects phosphorylation of RB1 protein by regulating gene expression of CDK4 and CCND1. We further demonstrated that reduced CDK8 expression underlies changes of β-catenin activity, and identified that H19 interacts with macroH2A, an essential regulator of CDK8 gene transcription. However, the relevance of H19-macroH2A interaction in CDK8 regulation remains to be experimentally determined. We further explored the clinical relevance of above mechanisms in clinical samples, and showed that combined analysis of H19 with its targets improved prognostic value of H19 in CRC.

Three-Dimensional Spheroid Cell Culture Model for Target Identification Utilizing High-Throughput RNAi Screens

The intrinsic limitations of 2D monolayer cell culture models have prompted the development of 3D cell culture model systems for in vitro studies. Multicellular tumor spheroid (MCTS) models closely simulate the pathophysiological milieu of solid tumors and are providing new insights into tumor biology as well as differentiation, tissue organization, and homeostasis. They are straightforward to apply in high-throughput screens and there is a great need for the development of reliable and robust 3D spheroid-based assays for high-throughput RNAi screening for target identification and cell signaling studies highlighting their potential in cancer research and treatment. In this chapter we describe a stringent standard operating procedure for the use of MCTS for high-throughput RNAi screens.

Abstract 3836: A 3D high throughput RNA1 screen identifies the TLR4 kinase which alters spheroid architecture: a promising therapeutic strategy for pancreatic cancer

Background: Pancreatic Ductal Adenocarcinoma (PDA) ranks fourth among cancer-related deaths in the United States. The poor prognosis of PDA is due to resistance to current therapies. Contributing to this resistance is the tumor architecture comprising dense desmoplastic stroma, extracellular matrix (ECM), tumor cells and tumor hypoxia. We hypothesized that destabilizing the compact tumor architecture by weakening the interactions between tumor cells alone or tumor cells along with the ECM may result in more effective therapies for PDA.

Methods and Results: Using the pancreatic cell line Panc1, we developed a three dimensional (3D) spheroid model system, that exhibits oxygen gradients and hypoxia that mimics the tumor microenvironment. We used the pancreatic cancer cell line PANC1-HRE that stably expresses HRE-luciferase and detects HIF-1α activation, and a platform comprising a non-matrix nano-structured scaffold, to generate compact spheroids with hypoxic inner cores and HIF-1α activation. A high throughput siRNA screen using the kinome siRNA library and our 3D spheroid modal system identified kinases whose silencing reduced both the level of hypoxia and activity of HIF-1α. The positive control, siRNA against HIF-1α, reduced activity of HIF-1α with no effect on the levels of hypoxia within the spheroids. We identified the kinases Toll-like receptor 4 (TLR4) and its downstream target spleen tyrosine kinase (SYK) as our lead candidates following target validation. Image analysis of spheroids transfected with siRNA against both TLR4 and SYK resulted in the loss of compactness of the spheroids. In addition, these spheroids also demonstrated a significant reduction in the levels of hypoxia determined by the hypoxia probe Lox-1. These findings suggest that the alteration of the spheroid architecture resulted in the reduction in hypoxia. Previous studies have shown that SYK is a direct target of TLR4. Therefore to determine the mechanism through which TLR4 dependent signaling regulates the integrity of the spheroidal architecture we are generating stable cell lines in Panc1 of shRNA targeting TLR4 under an inducible system. We will use our inducible shRNA targeting TLR4 and the two 3D model systems, the hanging drop system (analogous to a primary tumor) and the nanoculture plate system (analogous to the progression of a metastatic loci) to further confirm our findings.

Conclusion: TLR4 mediated signaling regulates the integrity of spheroid architecture. Inhibiting this pathway destabilized the tumor architecture altering the hypoxic state of the spheroid. Our long-term goals are to use known pharmacological inhibitors of TLR4 to study the mechanisms by which this kinase regulates tumor architecture, determine the pre-clinical significance of targeting TLR4 utilizing autochtonous mouse models for PDA and develop TLR4-targeted therapy for PDA.

Citation Format: Geoffrey A. Bartholomeusz, Alex Campos, Geoffrey Grandjean, Garth Powis. A 3D high throughput RNA1 screen identifies the TLR4 kinase which alters spheroid architecture: a promising therapeutic strategy for pancreatic cancer. [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 3836. doi:10.1158/1538-7445.AM2013-3836

Abstract 2303: The redox-active protein thioredoxin: A modulator of epithelial-mesenchymal transition

Human thioredoxin is a ubiquitous redox-active protein that induces the activation of many redox-sensitive transcription factors, inhibits the activity of the apoptosis-signal regulating kinase, and activates the AKT signaling pathway. Thioredoxin is thus associated with many biological processes, including the induction of cellular proliferation leading to cancer progression and metastasis. The morphogenetic changes occurring during the initial stage of metastasis is referred to as epithelial-mesenchymal transition (EMT). EMT results in the transition of cancer cells from an epithelial to a fibroblastic or mesenchymal phenotype, accompanied by a large number of changes in gene expression, particularly down regulation in the expression of the epithelial marker E-cadherin and induction of expression and activation of the mesenchymal marker vimentin, N-cadherin, or fibronectin. Transforming growth factor (TGF)-β is regarded as the prototype cytokine for induction of EMT both in vitro and in vivo. Using a high throughput functional genomic screen, we previously showed that members of the TGF-β signaling pathway induce the expression of thioredoxin in both pancreatic and breast cancer cells. In addition, we showed that TGF-β1 stimulation in these cells resulted in a two-fold induction of thioredoxin expression. Therefore, we hypothesized that thioredoxin is a modulator of EMT. We based this hypothesis on the finding that increased expression of thioredoxin is associated with metastasis and that TGF-β1 induces thioredoxin expression. Herein we present evidence in both breast cancer cells and human biopsy samples of breast tumors that support our hypothesis. In vitro three-dimensional cell cultures of the MDA-MB-231 breast cancer cell line undergo phenotypic changes similar to the morphogenetic changes associated with EMT. Treating MDA-MB-231 cells with PX12, a potent inhibitor of thioredoxin, blocked the onset of these morphogenetic changes. We show a correlation between the expression of thioredoxin and the EMT markers utilizing Reverse-Phase Protein Array of 250 fine-needle aspirates from breast tumor patients and the Pearson correlation coefficients. There was a positive correlation between thioredoxin and N-cadherin (p<0.0001), and a negative correlation between thioredoxin and E-cadherin (p<0.0001) as well as between thioredoxin and β-catenin (p<0.0001). High expression of thioredoxin correlate with decreased expression of E-cadherin and β-catenin and an increased expression of N-cadherin. Our data demonstrated that thioredoxin might be an important regulator of EMT in breast cancer. Based on our findings we propose a model indicating that thioredoxin modulates TGF-β-induced EMT by functioning to maintain EMT once it is initiated. Ongoing studies by our group will enable us to confirm this model.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2303.

Activation of a novel Bcr/Abl destruction pathway by WP1130 induces apoptosis of chronic myelogenous leukemia cells

Imatinib mesylate (Gleevec) is effective therapy against Philadelphia chromosome-positive leukemia, but resistance develops in all phases of the disease. Bcr/Abl point mutations and other alterations reduce the kinase inhibitory activity of imatinib mesylate; thus, agents that target Bcr/Abl through unique mechanisms may be needed. Here we describe the activity of WP1130, a small molecule that specifically and rapidly down-regulates both wild-type and mutant Bcr/Abl protein without affecting bcr/abl gene expression in chronic myelogenous leukemia (CML) cells. Loss of Bcr/Abl protein correlated with the onset of apoptosis and reduced phosphorylation of Bcr/Abl substrates. WP1130 did not affect Hsp90/Hsp70 ratios within the cells and did not require the participation of the proteasomal pathway for loss of Bcr/Abl protein. WP1130 was more effective in reducing leukemic versus normal hematopoietic colony formation and strongly inhibited colony formation of cells derived from patients with T315I mutant Bcr/Abl-expressing CML in blast crisis. WP1130 suppressed the growth of K562 heterotransplanted tumors as well as both wild-type Bcr/Abl and T315I mutant Bcr/Abl-expressing BaF/3 cells transplanted into nude mice. Collectively, our results demonstrate that WP1130 reduces wild-type and T315I mutant Bcr/Abl protein levels in CML cells through a unique mechanism and may be useful in treating CML.