Tumors In Athymic Nude Mice Research Articles

A roadmap from research to clinical testing of mesenchymal stromal cell exosomes in the treatment of psoriasis

The most clinically trialed cells, mesenchymal stromal cells (MSCs), are now known to mainly exert their therapeutic activity through paracrine secretions, which include exosomes. To mitigate potential regulatory concerns on the scalability and reproducibility in the preparations of MSC exosomes, MSC exosomes were produced using a highly characterized MYC-immortalized monoclonal cell line. These cells do not form tumors in athymic nude mice or exhibit anchorage-independent growth, and their exosomes do not carry MYC protein or promote tumor growth. Unlike intra-peritoneal injections, topical applications of MSC exosomes in a mouse model of IMQ-induced psoriasis alleviate interleukin (IL)-17, IL-23 and terminal complement complex, C5b9 in psoriatic skin. When applied on human skin explants, fluorescence from covalently labeled fluorescent MSC exosomes permeated and persisted in the stratum corneum for about 24 hours with negligible exit out of the stratum corneum into the underlying epidermis. As psoriatic stratum corneums are uniquely characterized by activated complements and Munro microabscesses, we postulated that topically applied exosomes permeate the psoriatic stratum corneum to inhibit C5b9 complement complex through CD59, and this inhibition attenuated neutrophil secretion of IL-17. Consistent with this, we demonstrated that assembly of C5b9 on purified human neutrophils induced IL-17 secretion and this induction was abrogated by MSC exosomes, which was in turn abrogated by a neutralizing anti-CD 59 antibody. We thus established the mechanism of action for the alleviation of psoriatic IL-17 by topically applied exosomes.

Pre-Clinical Efficacy of Targeting TBL1/R-β-Catenin-TCF7L2 Axis Against AML with 3q26 Lesions and EVI1 Overexpression

EVI1 gene maps to the MECOM locus at chromosome 3q26.2 and encodes for a zinc finger domain-containing transcriptional regulator. EVI1 supports hematopoietic stem cell self-renewal and blocks hematopoietic differentiation. EVI1 is overexpressed in up to 10% of AML, including those harboring chromosome translocation t(3;3)(q21;q26.2) or inv(3)(q21;q26.2), where the distal GATA2 hematopoietic enhancer is repositioned to induce EVI1 overexpression while repressing GATA2. EVI1 overexpression due to 3q26.2 lesions in MDS and AML is frequently associated with monosomy 7 and confers poor response to therapy and inferior relapse-free and overall survival. We had previously reported the pre-clinical efficacy of targeting TBL1/R1-nuclear β-catenin-TCF7L2 by tegavivint (BC-2059, Iterion Therapeutics) against AML stem/progenitor cells. This led us to interrogate the anti-AML activity of tegavivint (TV) in AML models harboring 3q26.2 lesions, where EVI1 overexpression has been documented to drive the biology of AML stem/progenitor cells. For this, we utilized AML cell lines with 3q26.2 lesions with/without monosomy 7 (UCSD-AML1, OCI-AML20, AML191 / MUTZ-3, AML194, HNT34), as well as patient-derived (PD) AML cells with 3q26 lesions with or without monosomy 7. Treatment with TV (10 to 100 nM) dose-dependently induced apoptosis in these cellular models. This was associated with attenuation of protein levels (determined by immunoblot analyses) of EVI1, TCF7L2, c-Myc, c-Myb, RUNX1, CEBPα, c-KIT, BCL2, Bcl-xL and MCL1, but upregulation of CD11b, BIM and cleaved PARP levels. Additionally, pan-BET protein inhibitor OTX015 (100 to 1000 nM) dose-dependently induced apoptosis of AML cell lines and PD AML cells with t(3:3)/inv(3). Following TV treatment, RNA-Seq and gene set enrichment analysis in UCSD-AML1 and OCI-AML20 cells showed log2 fold-changes in gene expression and positive enrichment of pathway genes and/or reactomes of inflammatory response, TNFα and interferon signaling, TGFβ, NOTCH and apoptosis signaling, as well as negative enrichment of gene sets of c-Myc, E2F, G2M checkpoint, DNA replication and repair and chromosome maintenance (all with FDR q-values < 0.1). QPCR analysis showed repression of EVI1, MYC and KIT, but upregulation of Axin2 mRNAs. Following TV treatment, confocal microscopy showed reduction of nuclear protein levels of EVI1 and β-catenin, as well as disrupted their co-localization with TBL1. Proximity ligation assay also demonstrated that exposure to TV significantly reduced the proximity of TBL1 and EVI1 as well as of TBL1 and β-catenin. Mass cytometry (CyTOF) analysis of patient-derived (PD) AML samples with t(3:3)/inv(3) confirmed that TV treatment attenuated protein levels of EVI1, c-Myc, RUNX1, β-catenin, TBL1/R1, Bcl-xL, BCL2, MCL1 and Ki67, but augmented protein levels of APC and cleaved PARP in phenotypically characterized AML stem cells (with high expression of CLEC12A, CD123, CD244, CD99, but low expression of CD11b). Consistent with effects of TV on gene-expressions that regulate cell death pathways, in vitro co-treatment with TV and BCL2 inhibitor venetoclax or OTX015 synergistically induced apoptosis (as determined by the SynergyFinder algorithm) of AML cell lines and PD AML cells with t(3:3)/inv(3) and EVI1 overexpression. In the in vivo HNT-34 model of flank-implanted and established tumors in athymic nude mice, treatment with TV (50 mg/kg, TIW, IP) and venetoclax (30 mg/kg, PO, daily) for 5-weeks yielded more tumor growth delay than vehicle control or TV alone. Additionally, following tail vein infusion and engraftment of luciferized AML191 cells in NSG mice, treatment with TV and/or venetoclax or OTX015 (30 mg/kg, PO, daily) was evaluated for 6 weeks. Co-treatment with TV and venetoclax or TV and OTX015 significantly reduced AML growth (determined by reduction in bioluminescence by Xenogen camera) (p < 0.05), as well as improved overall survival of the NSG mice more than treatment with each drug alone or vehicle control, without any toxicity. Collectively, these findings highlight that targeted inhibition of TBL1/R1-nuclear β-catenin-TCF7L2 by treatment with TV also inhibits EVI1 and its targets. They also demonstrate superior pre-clinical efficacy of novel TV-based combinations with BCL2 or BET protein inhibitor against AML models harboring 3q26 lesion and EVI1 overexpression. DisclosuresDiNardo: Celgene, a Bristol Myers Squibb company: Honoraria, Research Funding; Forma: Honoraria, Research Funding; Foghorn: Honoraria, Research Funding; GlaxoSmithKline: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Honoraria, Research Funding; ImmuneOnc: Honoraria, Research Funding; Notable Labs: Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria; Novartis: Honoraria; AbbVie: Consultancy, Research Funding; Agios/Servier: Consultancy, Honoraria, Research Funding. Takahashi: Symbio Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; GSK: Consultancy; Novartis: Consultancy; Celgene/BMS: Consultancy. Horrigan: Iterion Therapeutics: Current Employment. Kadia: Astellas: Other; Cure: Speakers Bureau; Genfleet: Other; Ascentage: Other; Jazz: Consultancy; Sanofi-Aventis: Consultancy; Dalichi Sankyo: Consultancy; Cellonkos: Other; Novartis: Consultancy; AstraZeneca: Other; BMS: Other: Grant/research support; Liberum: Consultancy; Amgen: Other: Grant/research support; Pulmotech: Other; Pfizer: Consultancy, Other; Genentech: Consultancy, Other: Grant/research support; Aglos: Consultancy; AbbVie: Consultancy, Other: Grant/research support.

A First-In-Class, Humanized Antibody Targeting Alternatively Spliced Tissue Factor: Preclinical Evaluation in an Orthotopic Model of Pancreatic Ductal Adenocarcinoma

In 2021, pancreatic ductal adenocarcinoma (PDAC) is the 3rd leading cause of cancer deaths in the United States. This is largely due to a lack of symptoms and limited treatment options, which extend survival by only a few weeks. There is thus an urgent need to develop new therapies effective against PDAC. Previously, we have shown that the growth of PDAC cells is suppressed when they are co-implanted with RabMab1, a rabbit monoclonal antibody specific for human alternatively spliced tissue factor (asTF). Here, we report on humanization of RabMab1, evaluation of its binding characteristics, and assessment of its in vivo properties. hRabMab1 binds asTF with a KD in the picomolar range; suppresses the migration of high-grade Pt45.P1 cells in Boyden chamber assays; has a long half-life in circulation (~ 5 weeks); and significantly slows the growth of pre-formed orthotopic Pt45.P1 tumors in athymic nude mice when administered intravenously. Immunohistochemical analysis of tumor tissue demonstrates the suppression of i) PDAC cell proliferation, ii) macrophage infiltration, and iii) neovascularization, whereas RNAseq analysis of tumor tissue reveals the suppression of pathways that promote cell division and focal adhesion. This is the first proof-of-concept study whereby a novel biologic targeting asTF has been investigated as a systemically administered single agent, with encouraging results. Given that hRabMab1 has a favorable PK profile and is able to suppress the growth of human PDAC cells in vivo, it comprises a promising candidate for further clinical development.

Abstract 908: Preclinical in vivo characterization of a first-in-class humanized antibody targeting alternatively spliced tissue factor

Abstract Tissue Factor, the initiator of the extrinsic pathway of coagulation, and its isoform alternatively spliced Tissue Factor (asTF) are often overexpressed in cancer cells. Previously, we have shown that RabMab1, a rabbit monoclonal antibody specific for human asTF, disrupts the binding of asTF to beta-integrins and thereby inhibits the growth of breast cancer and pancreatic ductal adenocarcinoma (PDAC) cell lines in vitro and in vivo. Here, we report on humanization of RabMab1, assessment of its binding characteristics, and determination of its in vivo properties. The variable regions of the heavy and light chains of hybridoma derived RabMab1 were cloned and used to generate a rabbit/human chimera (cRabMab1). Substitutions of species-specific residues were then carried out to produce humanized RabMab1 (hRabMab1; IgG1 isotype). Antigen binding was assessed via anti-human IgG Fc capture biosensor assays. cRabMab1 was found to have a KD of 4.24 nM whereas hRabMab1 was found to have a KD in the low picomolar range, which could not be precisely measured due to an extremely slow off-rate. The in vivo half-lives of each were determined to be 280 and 908 hours, respectively. Orthotopic co-implantation of cRabMab1 with high-grade, human PDAC cell line Pt45.P1 in athymic nude mice resulted in tumors that were 82% and 92% smaller than tumors in the vehicle and IgG control group groups, respectively, with no statistical difference between vehicle and IgG isotype control groups. Intravenous administration of hRabMab1 slowed the growth of pre-formed orthotopic Pt45.P1 tumors in athymic nude mice by 64% and 61% compared to vehicle and isotype control groups, respectively; again, there was no difference between vehicle and IgG isotype control groups. Immunohistochemical analysis of tumor tissue revealed a statistically significant 68% reduction in neovascularization (CD31), a 58% reduction in M2-polarized macrophages (CD206), and a 24% reduction in proliferating cells (Ki67) in the hRabMab1 cohort. RNAseq analysis of tumor tissue revealed that components of the focal adhesion system were the most affected by hRabMab1 treatment. In addition, a significant suppression of pathways that promote mitosis and the cell cycle was seen in hRabMab1-treated tumors. By qRT-PCR, we validated a greater than 82% reduction in the expression of HBEGF, a gene encoding a cell surface mitogen, and a greater than 68% reduction in the expression of STN1, a gene encoding a component of the CST-complex, a telomere replication and maintenance structure. This is the first proof-of-concept study whereby a novel biologic that inhibits asTF has been used as a systemically administered single agent, with encouraging results. Because hRabMab1 has a favorable pharmacokinetic profile and is able to suppress PDAC tumor cell growth in vivo, it is an attractive candidate for further clinical development. Citation Format: Clayton S. Lewis, Aniruddha Karve, Kateryna Matiash, Timothy Stone, Jingxing Li, Jordan Wang, Henri Versteeg, Bruce Aronow, Syed Ahmad, Pankaj Desai, Vladimir Bogdanov. Preclinical in vivo characterization of a first-in-class humanized antibody targeting alternatively spliced tissue factor [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 908.

BIMG-20. METABOLIC BIOMARKERS IN MICRODIALYSATE OF IDH-1 MUTANT TUMORS

Glioblastoma (GBM) is a common deadly malignant brain cancer of the central nervous system, with a median survival of 12–15 months. Scientific advancements are lacking in developing effective therapies for both primary GBM, as well as secondary GBMs, that typically originate as malignant transformation of lower-grade isocitrate dehydrogenase (IDH) 1-mutant tumors. The unique metabolomic profile of IDH1-mutant tumors presents opportunities to develop biomarker signatures of therapeutic efficacy. Microdialysis is an extracellular fluid sampling collection technique utilizing a perfused semipermeable catheter to permit diffusion of molecules between brain interstitium and the perfusate. We hypothesized that microdialysis may identify a metabolomics-based biomarker response to therapy in IDH1-mutant tumors. To test this hypothesis, orthotopic xenografts were generated from patient-derived xenografts (PDX) harboring mutant IDH-1 (R132H). Perfusates were collected from intra-cranial tumors in athymic nude mice sampled at baseline and 72h post treatment with temozolomide (TMZ), an oral alkylating agent used to treat IDH1-mutant gliomas, compared with vehicle treatment. Perfusates were analyzed via untargeted metabolomic profiling using liquid chromatography-mass spectrometry. Tumor specific metabolites such as (D)-2 hydroxyglutarate, were detected in microdialysate from IDH-1 mutant tumor bearing mice compared to non-tumor bearing mice. We also found high levels of metabolites such as 5-methylthioadenosine, and dimethylarginine and wide range of amino acids in microdialysate from IDH-1 mutant tumor bearing mice. TMZ treatment induced changes to metabolites in creatine and histidine metabolism. Our results indicate that microdialysis is a feasible technology to identify metabolomics-based biomarkers in IDH1-mutant gliomas and their response to therapy. We suggest that in vivo intratumoral microdialysis over several days could yield metabolic pharmacodynamic biomarkers of value to therapeutic translation for IDH-mutant gliomas.

Anthocyanins Derived from Vitis coignetiae Pulliat Contributes Anti-Cancer Effects by Suppressing NF-κB Pathways in Hep3B Human Hepatocellular Carcinoma Cells and In Vivo.

We previously demonstrated that anthocyanins from the fruits of Vitis coignetiae Pulliat (AIMs) induced the apoptosis of hepatocellular carcinoma cells. However, many researchers argued that the concentrations of AIMs were too high for in vivo experiments. Therefore, we performed in vitro at lower concentrations and in vivo experiments for the anti-cancer effects of AIMs. AIMs inhibited the cell proliferation of Hep3B cells in a dose-dependent manner with a maximum concentration of 100 µg/mL. AIMs also inhibited the invasion and migration at 100 µg/mL concentration with or without the presence of TNF-α. To establish the relevance between the in vitro and in vivo results, we validated their effects in a Xenograft model of Hep3B human hepatocellular carcinoma cells. In the in vivo test, AIMs inhibited the tumorigenicity of Hep3B cells in the xenograft mouse model without showing any clinical signs of toxicity or any changes in the body weight of mice. AIMs inhibited the activation NF-κB and suppressed the NF-κB-regulated proteins, intra-tumoral microvessel density (IMVD) and the Ki67 activity of Hep3B xenograft tumors in athymic nude mice. In conclusion, this study indicates that AIMs have anti-cancer effects (inhibition of proliferation, invasion, and angiogenesis) on human hepatocellular carcinoma xenograft through the inhibition of NF-κB and its target protein.

Abstract PO-041: Preclinical in vivo characterization of a first-in-class humanized antibody targeting alternatively spliced Tissue Factor

Abstract Tissue Factor, the initiator of the extrinsic pathway of coagulation, and its isoform alternatively spliced Tissue Factor (asTF) are often overexpressed in cancer cells. While asTF is only minimally procoagulant, it activates both the extracellular mechanical and intracellular signaling functions of beta-integrins. This leads to activation of multiple MAPK pathways thereby promoting increases in proliferation, migration, and angiogenesis. Previously, we have shown that RabMab1, a rabbit monoclonal antibody specific for human asTF, disrupts the binding of asTF to beta-integrins and thereby inhibits the growth of breast cancer and pancreatic ductal adenocarcinoma (PDAC) cell lines in vitro and in vivo. Here, we report on humanization of RabMab1, assessment of its binding characteristics, and determination of its in vivo properties. The variable regions of the heavy and light chains of hybridoma derived RabMab1 were cloned and used to generate a rabbit/human chimera (cRabMab1). Substitutions of species-specific residues were then carried out to produce humanized RabMab1 (hRabMab1; IgG1 isotype). Antigen binding was assessed via anti-human IgG Fc capture biosensor assays. cRabMab1 was found to have a KD of 4.24 nM whereas hRabMab1 was found to have a KD in the low picomolar range, which could not be precisely measured due to an extremely slow off-rate. The in vivo half-lives of each were determined to be 280 and 908 hours, respectively. Orthotopic co-implantation of cRabMab1 with high-grade, human PDAC cell line Pt45.P1 in athymic nude mice resulted in tumors that were 82% and 92% smaller than tumors in the vehicle and IgG control group groups, respectively, with no statistical difference between vehicle and IgG isotype control groups. Intravenous administration of hRabMab1 slowed the growth of pre-formed orthotopic Pt45.P1 tumors in athymic nude mice by 64% and 61% compared to vehicle and isotype control groups, respectively; again, there was no difference between vehicle and IgG isotype control groups. Immunohistochemical analysis of tumor tissue revealed a statistically significant 68% reduction in neovascularization (CD31), a 58% reduction in M2-polarized macrophages (CD206), and a 24% reduction in proliferating cells (Ki67) in the hRabMab1 cohort. RNAseq analysis of tumor tissue revealed a significant suppression of pathways that promote mitosis and the cell cycle. By qRT-PCR, we validated a greater than 82% reduction in the expression of HBEGF, a gene encoding a cell surface mitogen, and a greater than 68% reduction in the expression of STN1, a gene encoding a component of the CST-complex, a telomere replication and maintenance structure. This is the first proof-of-concept study whereby a novel biologic that targets asTF has been used as a systemically administered single agent, with encouraging results. Because hRabMab1 has a favorable pharmacokinetic profile and is able to suppress PDAC tumor growth in vivo, it comprises an attractive candidate for further clinical development. Citation Format: Clayton S. Lewis, Aniruddha Karve, Kateryna Matiash, Timothy Stone, Pankaj Desai, Vladimir Y. Bogdanov. Preclinical in vivo characterization of a first-in-class humanized antibody targeting alternatively spliced Tissue Factor [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2020 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2020;80(22 Suppl):Abstract nr PO-041.

Role of the PI3K/Akt pathway in cadmium induced malignant transformation of normal prostate epithelial cells

This study investigated the role of the PI3K/Akt pathway in cadmium (Cd) induced malignant transformation of normal prostate epithelial (PWR1E and RWPE1) cells. Both PWR1E and RWPE1 cells were exposed to 10 μM Cd for one year and designated as Cd-PWR1E and Cd-RWPE1. Cd-RWPE1 cells robustly formed tumors in athymic nude mice. Functionally, Cd-exposure induced tumorigenic attributes indicated by increased wound healing, migration and invasion capabilities in both cell lines. RT2-array analysis revealed many oncogenes including P110α, Akt, mTOR, NFKB1 and RAF were induced whereas tumor suppressor (TS) genes were attenuated in Cd-RWPE1. This was validated by individual quantitative-real-time-PCR at transcriptional and by immunoblot at translational levels. These results were consistent in Cd-PWR1E vs parental PWR1E cells. Gene Set Enrichment Analysis revealed that five prostate cancer (PCa) related pathways were enriched in Cd-exposed cells compared to their normal controls. These pathways include the KEGG- Pathways in cancer, Prostate Cancer Pathway, ERBB, Apoptosis and MAPK pathways. We selected up- and down-regulated genes randomly from the PI3K/Akt pathway array and profiled these in the TCGA/GDC prostate-adenocarcinoma (PRAD) patient cohort. An upregulation of oncogenes and downregulation of TS genes was observed in PCa compared to their normal controls. Taken together, our study reveals that the PI3K/Akt signaling is one of the main molecular pathways involved in Cd-driven transformation of normal prostate epithelial cells to malignant form. Understanding the molecular mechanisms involved in the Cd-driven malignant transformation of normal prostate cells will provide a significant insight to develop better therapeutic strategies for Cd-induced prostate cancer.

Abstract 1776: Exploring anetumab ravtansine in a preclinical model of thymic carcinoma

Abstract Thymic epithelial tumors (TETs) are a group of rare tumors (0.13 per 100,000 persons), comprised of thymomas and thymic carcinoma, arising from the epithelial cells of the thymus. The biology of these tumors is not well understood, and there are no approved targeted therapies against TETs. One promising drug target is mesothelin (MSLN), which is a surface glycoprotein that is cleaved to produce two proteins: mature MSLN (mMSLN) and megakaryocyte potentiating factor (MPF). In normal physiology, expression of MSLN is limited to mesothelial cells lining the pleura, pericardium, and peritoneum. Its expression is also present in various cancers, including thymic carcinoma, where it is expressed in 79% of cases. In this study, we investigate the ability of the MSLN targeting, fully human monoclonal antibody-drug conjugate (ADC) anetumab ravtansine (ARav) to inhibit growth of thymic carcinoma in in-vitro and in-vivo models. We utilized immunoblotting and RT-qPCR to characterize MSLN expression in human thymoma and thymic carcinoma derived cell lines. Binding of anetumab, the antibody moiety in ARav, to thymoma and thymic carcinoma cell lines was assessed by flow cytometry. In-vitro, ARav's effect on cell proliferation was tested against MP57 cells (thymic carcinoma), stably transfected with MSLN, utilizing CellTiter-Glo. ARav's activity in-vivo as a monotherapy, and as a combination therapy with cisplatin, was tested against MSLN expressing T1889 xenograft tumors in athymic nude mice and compared to vehicle, isotype control ADC, and standard-of-care (SoC) cisplatin. Using the anetumab antibody, thymoma (T1682) and thymic carcinoma (T1889) cell lines were shown to express MSLN on the cell surface. In-vitro, ARav was effective at inhibiting growth of MP57 cells stably transfected with mMSLN. In-vivo, 15 mg/kg ARav inhibited T1889 xenograft tumor growth more efficaciously than vehicle, the isotype control ADC (all given every 2 weeks), and 4 mg/kg cisplatin (given every week). Combining ARav at a dose of 7.5 mg/kg with 4 mg/kg cisplatin yielded an additive effect on inhibiting tumor growth. MSLN is expressed in thymoma and thymic carcinoma derived cell lines. Anetumab ravtansine inhibits growth of MSLN positive thymic carcinoma in our preclinical model; when combined with SoC cisplatin, ARav confers enhanced tumor growth inhibition. Citation Format: Vincent Chen, Anette Sommer, Christoph Schatz, Sabine Zitzmann-Kolbe, In-Kyu Kim, Giuseppe Giaccone. Exploring anetumab ravtansine in a preclinical model of thymic carcinoma [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 1776.

RNA Polymerase II-Associated Factor 1 Regulates Stem Cell Features of Pancreatic Cancer Cells, Independently of the PAF1 Complex, via Interactions With PHF5A and DDX3

It is not clear how pancreatic cancer stem cells (CSCs) are regulated, resulting in ineffective treatments for pancreatic cancer. PAF1, a RNA polymerase II-associated factor 1 complex (PAF1C) component, maintains pluripotency of stem cells, by unclear mechanisms, and is a marker of CSCs. We investigated mechanisms by which PAF1 maintains CSCs and contributes to development of pancreatic tumors. Pancreatic cancer cell lines were engineered to knockdown PAF1 using inducible small hairpin RNAs. These cells were grown as orthotopic tumors in athymic nude mice and PAF1 knockdown was induced by administration of doxycycline in drinking water. Tumor growth and metastasis were monitored via IVIS imaging. CSCs were isolated from pancreatic cancer cell populations using flow cytometry and characterized by tumor sphere formation, tumor formation in nude mice, and expression of CSC markers. Isolated CSCs were depleted of PAF1 using the CRISPR/Cas9 system. PAF1-regulated genes in CSCs were identified via RNA-seq and PCR array analyses of cells with PAF1 knockdown. Proteins that interact with PAF1 in CSCs were identified by immunoprecipitations and mass spectrometry. We performed chromatin immunoprecipitation sequencing of CSCs to confirm the binding of the PAF1 sub-complex to target genes. Pancreatic cancer cells depleted of PAF1 formed smaller and fewer tumor spheres in culture and orthotopic tumors and metastases in mice. Isolated CSCs depleted of PAF1 downregulated markers of self-renewal (NANOG, SOX9, and β-CATENIN), of CSCs (CD44v6, and ALDH1), and the metastasis-associated gene signature, compared to CSCs without knockdown of PAF1. The role of PAF1 in CSC maintenance was independent of its RNA polymerase II-associated factor 1 complex component identity. We identified DDX3 and PHF5A as proteins that interact with PAF1 in CSCs and demonstrated that the PAF1-PHF5A-DDX3 sub-complex bound to the promoter region of Nanog, whose product regulates genes that control stemness. Levels of the PAF1-DDX3 and PAF1-PHF5A were increased and co-localized in human pancreatic tumor specimens, human pancreatic tumor-derived organoids, and organoids derived from tumors of KPC mice, compared with controls. Binding of DDX3 and PAF1 to the Nanog promoter, and the self-renewal capacity of CSCs, were decreased in cells incubated with the DDX3 inhibitor RK-33. CSCs depleted of PAF1 downregulated genes that regulate stem cell features (Flot2, Taz, Epcam, Erbb2, Foxp1, Abcc5, Ddr1, Muc1, Pecam1, Notch3, Aldh1a3, Foxa2, Plat, and Lif). In pancreatic CSCs, PAF1 interacts with DDX3 and PHF5A to regulate expression of NANOG and other genes that regulate stemness. Knockdown of PAF1 reduces the ability of orthotopic pancreatic tumors to develop and progress in mice and their numbers of CSCs. Strategies to target the PAF1-PHF5A-DDX3 complex might be developed to slow or inhibit progression of pancreatic cancer.

Tunicamycin Interferes With Wnt Signaling and Inhibits Angiogenesis

Wnt signaling supports cellular proliferation. The transcription co‐author β‐catenin is also associated with the tissue development. Recent studies have shown Wnt signaling plays a significant role in vascular development, an important event in tumor progression. Our laboratory has established protein N‐glycosylation inhibitor, Tunicamycin reduces angiogenesis. It also reduces the progression of ER−/PR−/HER2+ and ER−/PR−/HER2− breast tumors in athymic nude mice. Tunicamycin is a competitive inhibitor of N‐acetylglucosaminyl 1‐phosphate transferase (GPT) activity and down regulates Glc3Man9GlcNAc2‐PP‐Dol biosynthesis. The consequence is “ER stress” and the cell cycle arrest in G1. We have then hypothesized that Tunicamycin negatively impacts Wnt signaling and the objective is to delineate this dynamic relationship. We have used western blotting, immunofluorescence microscopy and capillary endothelial cells as a model, and observed down regulated expression of Wnt proteins. We, therefore, conclude that Tunicamycin‐induced ER interferes with the Wnt signaling and inhibits angiogenesis.

In Vitro and In Vivo Antitumor Activity of Cucurbitacin C, a Novel Natural Product From Cucumber.

Cucurbitacin C (CuC), a novel analogue of triterpenoids cucurbitacins, confers a bitter taste in cucumber. Genes and signaling pathways responsive for biosynthesis of CuC have been identified in the recent years. In the present study, we explored the anti-cancer effects of CuC against human cancers in vitro and in vivo. CuC inhibited proliferation and clonogenic potential of multiple cancer cells in a dose-dependent manner. Low-dose CuC treatment induced cell cycle arrest at G1 or G2/M stage in different cancer lines, whereas high-dose treatment of CuC caused apoptosis in cancer cells. PI3K-Akt signaling pathway was found to be one of the major pathways involved in CuC-induced cell growth arrest and apoptosis by RNA-Seq and Western blotting. Mechanistic dissection further confirmed that CuC effectively inhibited the Akt signaling by inhibition of Akt phosphorylation at Ser473. In vivo CuC treatment (0.1 mg/kg body weight) effectively inhibited growth of cancer cell-derived xenograft tumors in athymic nude mice and caused significant apoptosis. Our findings for the first time demonstrated the potential therapeutic significance of CuC against human cancers.

Abstract 3619: Nanoparticle formulation of VERU 111 for pancreatic cancer treatment

Abstract Background: Pancreatic cancer (PanCa) is one of the leading causes of cancer-related mortality in the United States due to very limited therapeutic options. Thus, developing novel therapeutic strategies will help for the management of this disease. We recently identified VERU-111, a novel synthetic molecule which showed potent anti-cancer effect against PanCa via targeting clinically important βIII and βIV tubulin isoforms. In this study, we synthesized and characterized its novel nanoformulation (MNP-VERU) and evaluated its therapeutic effects in vitro and xenograft mouse model. Methods: MNPs were prepared by chemical precipitation method and loaded with VERU-111 using diffusion method. This formulation was characterized for particle size, chemical composition, and drug loading efficiency, using various physico-chemical methods (TEM, FT-IR, DSC, TGA, and HPLC). The internalization of MNP-VERU was achieved after 6 hours incubation with MNP-VERU in PanCa cells. To determine therapeutic efficacy of MNP-VERU, we performed various in vitro (MTS, wound healing, boyden chamber real-time xCELLigence, and apoptosis assays) and in vivo (mouse tumor xenograft) studies using PanCa. Effect of MNP-VERU on various key oncogenic signaling pathways, and miRNAs was evaluated by Western blot, immunohistochemistry (IHC), confocal microscopy, qRT-PCR and in situ hybridization (ISH) analyses respectively. Result: Our novel MNP-VERU formulation provided average size of 110 nm in dynamic light scattering (DLS) and exhibited -8.23 to -11.65 mV zeta potential with an outstanding loading efficiency (94%). Cellular uptake and internalization studies demonstrate that MNP-VERU escape lysosomal degradation, providing efficient endosomal release to cytosol. MNP-VERU showed remarkable anti-cancer potential in various PanCa cells (Panc-1, AsPC-1, HPAF-II, BxPC-3, MiaPaca) and more effectively repressed βIII and βIV tubulin isoforms via restoring the expression of miR-200c. MNP-VERU more effectively suppressed AsPC-1 cells derived xenograft tumors in athymic nude mice. Conclusions: Taken together, our results suggest that MNP-VERU has more anti-cancer potential than free VERU-111 against PanCa. MNP-VERU may reduce the toxicity and improve the bioavailability of free VERU-111 and could be used for the management of PanCa. Citation Format: Vivek K. Kashyap, Bilal B. Hafeez, Qinghui Wang, Neeraj Chauhan, Prashanth K. Nagesh, Murali M. Yallapu, Duane D. Miller, Wei Li, Meena Jaggi, Subhash C. Chauhan. Nanoparticle formulation of VERU 111 for pancreatic cancer treatment [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 3619.

Interleukin-24 (IL24) Is Suppressed by PAX3-FOXO1 and Is a Novel Therapy for Rhabdomyosarcoma.

Alveolar rhabdomyosarcoma (ARMS) patients have a poor prognosis, and this is primarily due to overexpression of the oncogenic fusion protein PAX3-FOXO1. Results of RNA-sequencing studies show that PAX3-FOXO1 represses expression of interleukin-24 (IL24), and these two genes are inversely expressed in patient tumors. PAX3-FOXO1 also regulates histone deacetylase 5 (HDAC5) in ARMS cells, and results of RNA interference studies confirmed that PAX3-FOXO1-mediated repression of IL24 is HDAC5-dependent. Knockdown of PAX3-FOXO1 decreases ARMS cell proliferation, survival, and migration, and we also observed similar responses in cells after overexpression of IL24, consistent with results reported for this tumor suppressor-like cytokine in other solid tumors. We also observed in double knockdown studies that the inhibition of ARMS cell proliferation, survival, and migration after knockdown of PAX3-FOXO1 was significantly (>75%) reversed by knockdown of IL24. Adenoviral-expressed IL24 was directly injected into ARMS tumors in athymic nude mice, and this resulted in decreased tumor growth and weight. Because adenoviral IL24 has already successfully undergone phase I in clinical trials, this represents an alternative approach (alone and/or combination) for treating ARMS patients who currently undergo cytotoxic drug therapies.

Development of patient-derived orthotopic xenografts from metastatic colorectal cancer in nude mice

Liver metastasis is the major cause of death for patients with colorectal cancer. Despite treatment with surgery and chemotherapy, patient outcomes are quite unfavourable. Thus, there is an urgent need to develop new treatment strategies with the associated establishment of good animal models. Metastatic disease can be modelled using patient-derived orthotopic xenografts, which accurately replicate intra-tumoral heterogeneity so that various chemotherapeutic agents can be tested on individual tumours to aid in clinical decision-making. The objective of this study was to develop metastatic colorectal tumours in athymic nude mice by implanting fresh tumour fragments into mouse liver parenchyma. Metastatic tumours were successfully propagated in mice following transplantation from human patients, then serially implanted in second and third-generation mice. Morphologic and immunohistochemical characteristics indicate that xenografts recreate the tumour architecture and mismatch repair gene expression for MLH1, MSH2, MSH1, and PMS2. After tumour implantation during the first passage, the time of tumour growth decreased without loss of tumour identity. Post-transplantation lymphoproliferative disease was observed in one case. This pilot study was successful in establishing the institutional PDX preclinical platform to study new therapeutic strategies, disease progression biomarkers, and treatment responsiveness.

Abstract PR09: Alterations in cell junctions and neuroendocrine differentiation are key early steps in Crebbp/Ep300 mutation-driven SCLC development

Abstract The abundance and heterogeneity of somatic alterations in small cell lung cancer (SCLC) present immense challenges in identifying key mechanisms of tumor development. Functional characterization of recurrent mutations is an essential step towards understanding the early stages of SCLC development, but this remains extremely difficult due to the scarcity of relevant and tractable models for defining oncogenic drivers and molecular pathways. In a previous study, we derived precancerous cells (preSCs) from the Rb/p53/Rbl2-mutant mouse model of SCLC and developed an engineered preSC-based model of early tumor development. In this model, activation of oncogenic drivers transforms preSCs into tumorigenic cells that form spheroid clusters characteristic of SCLC in culture and subcutaneous tumors in athymic nude mice. Using this streamlined approach, we found that both retroviral amplification of the Myc family members and CRISPR/Cas9-mediated mutation of Crebbp/Ep300 were sufficient to cause transformation of preSCs into SCLC cells. Notably, both sets of mutant preSC underwent a similar phenotypic change from adherent monolayers to spheroid aggregates, suggesting that the two different types of alterations interact with or converge on common molecular pathways. Comparative profiling of control preSCs and mutant preSCs carrying either a Myc family amplification or Crebbp/Ep300 mutation revealed that alterations in cell junctions and neuroendocrine differentiation are the most significant molecular changes during cellular transformation. The transformed preSCs exhibited decreased expression of adhesion-related genes, including Cdh1 and Dsp, but increased expression of mesenchymal genes Vim and Twist1. The transformed cells also showed reduced expression of neuroendocrine (NE) differentiation genes, including Ascl1, Chga, and Syp. Furthermore, these changes coincided with increased expression of Notch receptors and decreased expression of their ligands Dlls and Jags. Taken together, these novel findings suggest that a phenotypic switch from Dll/Jag-expressing NE cells to Notch-expressing non-NE cells is a key event in early SCLC development. This study also demonstrated that the preSC-based model can facilitate functional validation of recurrent mutations in SCLC and molecular pathways that will be further explored for mechanistic elucidation and development of targeted therapies. This abstract is also being presented as Poster A09. Citation Format: Dong-Wook Kim, Keebeom Kim, Colin T. Dunn, Kwon-Sik Park. Alterations in cell junctions and neuroendocrine differentiation are key early steps in Crebbp/Ep300 mutation-driven SCLC development [abstract]. In: Proceedings of the Fifth AACR-IASLC International Joint Conference: Lung Cancer Translational Science from the Bench to the Clinic; Jan 8-11, 2018; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(17_Suppl):Abstract nr PR09.

Abstract B07: Characterization of branched-chain aminotransferase 1 as a novel therapeutic target for small cell lung cancer

Abstract Few studies have explored tumor metabolism to target small cell lung cancer (SCLC), for which treatment options are limited and eventually fail with resistance. The objective of this study is to identify novel biomarkers and therapeutic targets among molecular changes specific to the cancer cells relative to precancerous precursor cells. In our previous study, comparative profiling of precancerous cells with SCLC cells revealed branched-chain aminotransferase1 (Bcat1) as one of the most upregulated genes in the cancer cells relative to their precursors as well as normal lung. Based on this result, we hypothesize that the elevated Bcat1 plays a role in promoting SCLC. Here, we confirmed elevated Bcat1 protein expression in mouse SCLC cells relative to precancerous cells and in human SCLC lines. Targeting Bcat1 in mouse and human SCLC cells with shRNA or small-molecule inhibitors significantly reduced colony expansion in soft agar and formation of subcutaneous tumors in athymic nude mice. Inhibition of Bcat1 also reduced protein synthesis rate as measured by puromycin incorporation into protein. Additionally, we found Bcat1 plays a significant role in leucine catabolism in mouse SCLC using a coupled enzymatic assay. Taken together, these novel findings suggest that elevated Bcat1 promotes SCLC growth by supporting protein synthesis, which is necessary for proliferating cells. Given the proven safety profile of existing inhibitors of Bcat1, our findings are significant in supporting the concept of targeting Bcat1 as a novel and particularly valuable therapeutic strategy for SCLC. Citation Format: Napoleon B. Butler, Keebeom Kim, Dong-wook Kim, Kwon Park. Characterization of branched-chain aminotransferase 1 as a novel therapeutic target for small cell lung cancer [abstract]. In: Proceedings of the Fifth AACR-IASLC International Joint Conference: Lung Cancer Translational Science from the Bench to the Clinic; Jan 8-11, 2018; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(17_Suppl):Abstract nr B07.

Abstract 356: Polyadenyaltion of canonical histone mRNA: A potential mechanism of arsenic-induced carcinogenesis

Abstract Naturally occurring inorganic arsenic has been identified as a prominent causal agent in lung, bladder, liver, and prostate cancers. Although arsenic (As) has long been known to induce carcinogenicity via epigenetic mechanisms, alteration in histone gene expression has not been explored. The replication-dependent histone genes (also known as canonical histone genes) are the only genes found in multicellular organisms whose messenger RNA (mRNA) does not terminate with a poly(A) tail at the 3' end. Instead, they contain a conserved 26-nucleotide sequence that forms a stem-loop structure, and serves as the binding site for the Stem-loop binding protein (SLBP). SLBP is critical for canonical histone pre-mRNA processing and histone mRNA translation. Our previous studies demonstrated that arsenic exposure increases polyadenylation of histone H3.1 mRNA (a canonical histone H3) and its presence outside of S phase of the cell cycle due to the loss of SLBP protein and mRNA. Here we report that ectopic expression of polyadenylated H3.1 mRNA induces cell transformation and that the transformed cells are able to form tumors in athymic nude mice. These carcinogenic effects are dependent on the level of polyadenylation of canonical H3.1 mRNA. Notably, transfection of H3.1 cDNA with a stem-loop sequence in the front of the poly(A) signal generates less polyadenylated H3.1 mRNA and thereby attenuates cell transformation. Furthermore, the increase in polyadenylated H3.1 mRNA is able to antagonize histone H3.3 (a non-canonical variant of H3) in the promoter of active genes and perturb expression of cancer-related genes. In addition transfection of H3.1 with a poly(A) tail causes mitotic block in the cell cycle as well as chromosome instability. Furthermore, acute arsenic exposure by inhalation in mice results in the loss of SLBP and gain of polyadenylated H3.1 mRNA in lung tissues. These results suggest that the polyadenylation of canonical histone mRNAs induce by Arsenic is very disruptive to cellular genomic integrity and contributes to development of human cancers. Citation Format: Qiao Yi Chen, Danqi Chen, Thomas Kluz, Feng Wu, Yusha Zhu, Thomas Des Marais, Jinquan Li, Xiaoru Zhang, Ashley Jordan, Hong Sun, Chunyuan Jin, Max Costa. Polyadenyaltion of canonical histone mRNA: A potential mechanism of arsenic-induced carcinogenesis [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 356.

Abstract 679: ABI-231: A novel small molecule suppresses tumor growth and metastatic phenotypes of cervical cancer cells via targeting HPV E6 and E7

Abstract Objective: Cervical cancer is one of the most common and deadly cancers among women worldwide and is associated with persistent Human Papillomavirus (HPV) infection. Human papilloma virus (HPV) expressing E6 and E7 oncoproteins involved in carcinogenesis through their interactions with the p53 and pRB pathways, respectively. Therefore, non-toxic agents that have potential to inhibit the expression of E6 and E7 oncoproteins and their regulated oncogenic signaling pathways could be used in the management of cervical cancer. Microtubule targeting agents including paclitaxel, colchicine and vinca alkaloids are widely used in the treatment of various cancers but most of these agents have toxic side effects and develop chemoresistance. Herein, we investigated the potential anti-cancer effects of a novel tubulin targeting agent (ABI-231) in in vitro and in vivo model systems. Method: ABI-231 ((2-(1H-indol-3-yl)-1H-imidazol-4-yl)(3,4,5-trimethoxyphenyl))- methanone was synthesized in our home institution. Human cervical cancer cells (CaSki and SiHa) were used as in vitro model system. To determine the effect of ABI-231 on cell proliferation, migration and invasion, we performed MTS and wound healing assays. Effect of ABI-231 on the expression of HPV E6/E7 was determined by Western blot, qRT-PCR, and confocal microscopy. Xenograft study was performed to determine the effect of ABI-231 on cervical tumor growth. Results: ABI-231 treatment significantly (P&amp;lt;0.01) inhibited growth, clonogenic, invasive and migratory potential of cervical cancer cells. ABI-231 treatment was resulted in inhibition of HPV E6 and E7 expression at both mRNA and protein levels in both Caski and SiHa cells. ABI-231 inhibited phosphorylation of STAT3 at both Tyr705 and Ser727 residues. ABI-231 arrested cell cycle in G2/M phase as determined by flow cytometry and inhibited protein levels of cyclin B1, p21 and p27. Moreover, ABI-231 treatment SiHa and Caski was resulted in induction of apoptosis which was analyzed by enhance Annexin V staining. Western blot results demonstrated cleavage in PARP protein, Bid, and Bim. ABI-231 treatment also showed significant (P&amp;lt;0.01) inhibition of xenograft tumors in athymic nude mice. Excised xenograft tumors tissues were also analyzed for oncogenic signaling components which showed potent inhibition of aforementioned oncogenic signaling components compared to control. Conclusions: Taken together, our results demonstrate the potential anti-cancer efficacy of ABI-231 in in vivo and in vivo. ABI-231 can be explored as a potent therapeutic agent for the treatment of cervical cancer. Citation Format: Vivek K. Kashyap, Bilal B. Hafeez, Qinghai Wang, Neeraj Chauhan, Prashanth K. Nagesh, Nirnoy Dan, sonam kumari, Shabnam Malik, Saini Setua, Aditya Ganju, Murali M. Yallapu, Duane D. Miller, Wei Li, Meena Jaggi, Subhash C. Chauhan C. Chauhan. ABI-231: A novel small molecule suppresses tumor growth and metastatic phenotypes of cervical cancer cells via targeting HPV E6 and E7 [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 679.

Abstract 1045: Development of patient derived orthotopic xenografts from metastatic colorectal cancer

Abstract The occurrence of liver metastasis is the major cause of death in colorectal cancer patients. The treatment consists of surgery and chemotherapy. However, the patient outcome is very unfavorable. Thus, the development of new therapeutic regimens to treat this condition is urgent and demand the establishment of good animal models. Among the models that have being used, the patient-derived xenografts (PDX) have emerged as one of the most promising. PDXs are preclinical models that faithfully represent the individuality of human cancer, by grafting fresh human tumor in severely immunodeficient mice which allows for higher tumor implantation rates and growth. Metastatic disease could be also modeled using orthotopic implantation into the affected organ. The patient-derived orthotopic xenografts (PDOX) can be interrogated for different treatment strategies based on the individualized gene signature of the human tumor, and the results can inform clinically relevant treatment strategies for the patient. With the objective to establish a PDOX from metastatic colorectal tumors in athymic nude mice, we implanted fresh tumor fragments into mouse liver parenchyma and propagated tumors from three patients which could be serially implanted in second and third mice generations. The morphological and immunohistochemical characterization indicate that xenografts recapitulate the tumor architecture and the expression of mismatch repair genes (MLH1, MSH2, MSH1, PMS2). After tumor implantation in first passage, the time of tumor growth decrease from 150-250 days to 30-100 days without loss of tumor identity. The growth of a post-transplantation lymphoproliferative disease (PTLD) was observed in one case. This pilot study was successful to establish the institutional PDX preclinical platform to study new therapeutic strategies, biomarkers of disease progression and treatment responsiveness. Citation Format: Tiago Goss dos Santos, Bruno Roque, Caroline Roque, Maria Dirlei Begnani, Eduardo Lima, Felipe Coimbra, Rubens Chojniak. Development of patient derived orthotopic xenografts from metastatic colorectal 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 1045.