Orthotopic Tumor Growth Research Articles

VERU-111 suppresses tumor growth and metastatic phenotypes of cervical cancer cells through the activation of p53 signaling pathway.

In this study, we investigated the therapeutic efficacy of VERU-111 in vitro and in vivo model systems of cervical cancer. VERU-111 treatment inhibited cell proliferation and, clonogenic potential, induce accumulation of p53 and down regulated the expression of HPV E6/E7 expression in cervical cancer cells. In addition, VERU-111 treatment also decreased the phosphorylation of Jak2(Tyr1007/1008) and STAT3 at Tyr705 and Ser727. VERU-111 treatment arrested cell cycle in the G2/M phase and modulated cell cycle regulatory proteins (cyclin B1, p21, p34cdc2 and pcdk1). Moreover, VERU-111 treatment induced apoptosis and modulated the expression of Bid, Bcl-xl, Survivin, Bax, Bcl2 and cleavage in PARP. In functional assays, VERU-111 markedly reduced the migratory and invasive potential of cervical cancer cells via modulations of MMPs. VERU-111 treatment also showed significant (P<0.05) inhibition of orthotopic xenograft tumor growth in athymic nude mice. Taken together, our results demonstrate the potent anti-cancer efficacy of VERU-111 in experimental cervical cancer models.Thus, VERU-111 can be explored as a promising therapeutic agent for the treatment of cervical cancer.

A polymeric paste-drug formulation for intratumoral treatment of prostate cancer.

Focal therapy has emerged as a treatment option for low- to intermediate-risk localized prostate cancer (PCa) patients, to balance the risks for urinary and sexual morbidity of radical treatment with the psychological burden of active surveillance. In this context, we developed ST-4PC, an injectable, polymeric paste formulation containing docetaxel (dtx) and bicalutamide (bic) for image-guided focal therapy of PCa. The objective of this work was to evaluate the in vitro characteristics and in vivo toxicity and efficacy of ST-4PC. In vitro drug release was evaluated using high-performance liquid chromatography. In vivo toxicity of blank- and drug-loaded ST-4PC was assessed in mice and rats. Tumor growth inhibition was evaluated in LNCaP subcutaneous (s.c.) and LNCaP-luc orthotopic xenograft models. Using the s.c. model, mice were monitored weekly for weight loss, tumor volume (TV) and serum PSA. For the orthotopic model, mice were additionally monitored for bioluminescence as measure of tumor growth. ST-4PC demonstrated a sustained and steady release of incorporated drugs with 50% dtx and 20% bic being released after 14 days. While no systemic toxicity was observed, dose-dependent local side effects from dtx developed in the s.c. but not in the orthotopic model, illustrating the limitations of s.c. models for evaluating local cytotoxic therapy. In the s.c. model, 0.1%/4% and 0.25%/4% dtx/bic ST-4PC paste significantly reduced PSA progression, but did not have a significant inhibitory effect on TV. ST-4PC loaded with 1%/4% dtx/bic significantly reduced TV, serum PSA, and bioluminescence in the orthotopic xenograft model. Compared with drugs dissolved in DMSO, ST-4PC significantly delayed tumor growth. Image-guided focal therapy using ST-4PC demonstrated promising inhibition of PSA progression and orthotopic tumor growth in vivo without significant toxicity, and warrants further clinical evaluation.

Abstract GMM-021: UTILIZATION OF PATIENT-DERIVED TUMOR XENOGRAFT (PDX) MODELS IN ONCOLOGY

Abstract BACKGROUND: The 5-year survival rate of patients with recurrent epithelial ovarian cancer is only 30%, in part due to relapse and resistance to first-line platinum-based chemotherapy. Even with marked progress toward understanding ovarian cancer biology, the translation of research findings into new therapies is still an enormous barrier to progress. Recent data suggests a 90% failure rate for new oncology drugs in the clinic. Development and preclinical testing of new cancer therapies has been limited by the availability of clinically relevant models that recapitulate the molecular and phenotypic characteristics of primary ovarian cancers. To overcome this barrier, we have initiated collaborative project between Stephenson Cancer Center (SCC) and Oklahoma Medical Research Foundation (OMRF) with the goal to generate a biobank of patient-derived xenograft (PDX) models derived directly from ovarian cancer patients undergoing therapy. RESULTS: PDX tumor models are generated in the Patient-Derived Xenograft and Preclinical Therapeutics (PDX-PCT) Core at OMRF and used to improve preclinical evaluation of new drugs towards more personalized medicine. We have collected blood samples and tumor tissues from consenting patients having primary debulking surgery at Stephenson Cancer Center since 2015 (&amp;gt;140 unique patients). Fresh tumor tissue is minced into small tumor chunks (~2 mm) and implanted into immunocompromised mice. PDXs are expanded for 3-4 passages and characterized based on tumor type, histology and molecular characteristics. Immunohistochemical and molecular analysis showed that histology of the original patient tumors as well as the expression of commonly used markers for high-grade serous ovarian cancer such as cytokeratin, PAX8 and WT1 are perfectly maintained in the derivative PDX lines. Genotyping of patients' tumors and their corresponding PDXs using Illumina's Exome Array revealed that single nucleotide polymorphism (SNP) profile found in the original tumors is perfectly maintained in PDX lines. One of the PDX limitations is that human tumor stromal and immune cells are being replaced with mouse equivalents upon in vivo propagation of PDXs, which negatively affects quality of genomic or proteomic analyses. To overcome this challenge, we optimized a method to deplete mouse cells from PDX tumors by magnetic cells separation. Our data showed that ovarian cancer PDXs contain around 28-54% of human tumor cells, where the rest are mouse cells. We also optimized protocols to utilize pure population of human tumor cells isolated from PDXs to transduce these with lentiviral vectors expressing GFP and/or luciferase to generate luciferized PDXs. Luciferized ovarian PDXs are excellent models used for non-invasive orthotopic tumor growth and drug response monitoring. CONCLUSIONS: Collection of our PDXs illustrates heterogeneity and diversity of human ovarian tumors. However, each PDX maintains essential molecular features of the original patients' tumor. Our goal is to generate clinically faithful ovarian tumor models that will provide a platform to learn more about cancer biology and to screen these for new better therapies. Citation Format: Magdalena Cybula, Katherine Moxley, Lin Wang, Luyao Wang, Magdalena Bieniasz. UTILIZATION OF PATIENT-DERIVED TUMOR XENOGRAFT (PDX) MODELS IN ONCOLOGY [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr GMM-021.

GENE-43. TARGETING GABPb1L INHIBITS IN VIVO GROWTH OF TERT PROMOTER MUTANT GLIOBLASTOMA

Abstract Understanding cancer cell immortality in primary glioblastoma (GBM) is essential for the development of more informed treatments. Multiple cancer types, including &gt;80% of GBMs, undergo immortalization by reactivating Telomerase Reverse Transcriptase (TERT) through acquired mutations in the TERT promoter. TERT, the catalytically active and rate-limiting subunit of telomerase, functions to maintain telomeres, which cap and protect the ends of chromosomes. Our past work has demonstrated that the transcription factor GABP - and specifically its tetramer-forming isoform GABPb1L - binds and activates the mutant TERT promoter. The generation of CRISPR-induced indels in GABPb1L results in a gradual loss of cell viability in TERT promoter mutant but not TERT promoter wild type tumor cells in vitro, but the extent to which GABPb1L function is compromised in this setting is unclear. Thus, the potential for use of GABPb1L as an effective therapeutic target for TERT promoter mutant GBM requires further investigation. Here, we use CRISPR-based strategies to demonstrate that full knockout of GABPb1L is rapidly lethal in TERT promoter mutant cells in vitro, in association with a decrease in both TERT mRNA and telomerase activity. Heterozygous deletion of GABPb1L in the context of TERT promoter mutations leads to slowed growth of orthotopic xenograft tumors in mice, and prolonged survival. Additionally, inducible RNAi-mediated inhibition of GABPb1L in growing tumors is also capable of decreasing tumor burden and increasing survival, further strongly suggesting that targeting GABPb1L in patient tumors could be a viable treatment strategy. Finally, reduced GABPb1L synergizes with temozolomide (TMZ) therapy such that TMZ treatment in the context of low GABPb1L and low TERT leads to a complete ablation of orthotopic GBM xenografts. These results highlight the potential to improve disease outcomes by targeting TERT through inhibition of GABPb1L, particularly in conjunction with TMZ treatment.

STEM-21. INVESTIGATING DOT1L AS AN EPIGENETIC VULNERABILITY IN BRAIN TUMOR STEM CELLS

Abstract Glioblastoma (GBM), the most common and aggressive primary adult brain cancer, is thought to be driven by a small subpopulation of brain tumor stem cells (BTSCs). BTSCs exhibit shared properties with normal stem cells such as self-renewal and multilineage differentiation. These stem cell properties have been proposed to underlie GBM tumorigenicity, treatment evasion and contribute to tumor heterogeneity. To investigate the biology underlying the stem cell properties of GBM, we compared gene essentiality profiles for a panel of BTSCs, fetal neural stem cells and non-GBM cell lines using a CRISPR Cas9 knockout library. Interestingly, from these screens, we identified the histone methyltransferase disrupter of telomeric silencing-1-like (DOT1L) as an essential gene for the growth of BTSCs and fetal neural stem cells but not for non-GBM cell lines. DOT1L is the only known histone methyltransferase responsible for histone 3 lysine 79 methylation, an epigenetic mark associated with active gene transcription. The role of this epigenetic regulator in BTSCs was investigated in depth using EPZ-5676, a clinically relevant small molecule inhibitor. Short-term treatment with EPZ-5676 in BTSCs showed minimal effects on cell viability but led to striking morphological changes, increased neuronal and astrocytic differentiation and a reduction in self-renewal. Longer treatment periods with EPZ-5676 led to a decrease in BTSC proliferation and an increase in apoptosis. Furthermore, BTSCs pretreated with EPZ-5676 led to slowed orthotopic tumor growth and improved overall survival in a SCID mouse model. Overall, these findings suggest DOT1L epigenetically regulates GBM stem cell properties and tumor growth. We are further investigating the mechanisms underlying DOT1L regulation of gene expression in BTSCs with the goal of improving the field’s understanding of epigenetics and the therapeutic implications of targeting epigenetic processes in GBM.

The long non-coding RNA GHSROS facilitates breast cancer cell migration and orthotopic xenograft tumour growth.

Recent evidence suggests that numerous long non-coding RNAs (lncRNAs) are dysregulated in cancer, and have critical roles in tumour development and progression. The present study investigated the ghrelin receptor antisense lncRNA growth hormone secretagogue receptor opposite strand (GHSROS) in breast cancer. Reverse transcription-quantitative polymerase chain reaction revealed that GHSROS expression was significantly upregulated in breast tumour tissues compared with normal breast tissue. Induced overexpression of GHSROS in the MDA-MB-231 breast cancer cell line significantly increased cell migration in vitro, without affecting cell proliferation, a finding similar to our previous study on lung cancer cell lines. Microarray analysis revealed a significant repression of a small cluster of major histocompatibility class II genes and enrichment of immune response pathways; this phenomenon may allow tumour cells to better evade the immune system. Ectopic overexpression of GHSROS in the MDA-MB-231 cell line significantly increased orthotopic xenograft growth in mice, suggesting that in vitro culture does not fully capture the function of this lncRNA. This study demonstrated that GHSROS may serve a relevant role in breast cancer. Further studies are warranted to explore the function and therapeutic potential of this lncRNA in breast cancer progression.

Generation and evaluation of a chimeric antibody against coxsackievirus and adenovirus receptor for cancer therapy.

Coxsackievirus and adenovirus receptor (CAR) is a single‐pass transmembrane protein that is associated with adenoviral infection. CAR is involved in the formation of epithelial tight junctions and promotes tumor growth in some cancers. Previously, we developed mouse monoclonal antibodies against human CAR and found that one, mu6G10A, significantly inhibited tumor growth in xenografts of human cancer cells. Herein, we generated and characterized a mouse‐human chimeric anti‐CAR antibody (ch6G10A) from mu6G10A. ch6G10A had binding activity, inducing antibody‐dependent cellular cytotoxicity and complement‐dependent cytotoxicity, and in vivo anti‐tumor activity against CAR‐expressing prostate cancer DU‐145 cells. In addition, cancer tissue array analysis confirmed that CAR is highly expressed in neuroendocrine lung cancers including small cell lung cancer, and treatment with ch6G10A effectively inhibited in vivo subcutaneous tumor growth of NCI‐H69 small cell lung cancer cells in nude mice. Moreover, treatment with mu6G10A effectively inhibited both in vivo orthotopic tumor growth and distant metastatic formation in mouse xenograft models of a highly metastatic subline of human small cell lung cancer DMS273 cells. These results suggest that targeting therapy to CAR with a therapeutic antibody might be effective against several cancer types including small cell lung cancer.

Recombinant virus-like particles presenting IL-33 successfully modify the tumor microenvironment and facilitate antitumor immunity in a model of breast cancer

Recently, interleukin (IL)-33 has been closely associated with a variety of clinical cancers. IL-33 presents both protumorigenic, and less frequently, antitumorigenic functions depending on disease conditions. IL-33 signaling appears to be a possible target for the treatment of applicable tumor diseases. This study aimed to develop an effective approach to intervene in IL-33 functioning in tumors and reveal the immunotherapeutic potential of anti-IL-33 active immunization. Recombinant truncated hepatitis B virus core antigen (HBcAg), presenting mature IL-33 molecules on the surface of virus-like particles (VLPs), was prepared and used to immunize BALB/c mice in a model of murine 4T1 breast cancer. The immunization was performed through either a preventive or therapeutic strategy in two separate studies. Anti-IL-33 immunization with VLPs elicited a persistent and highly titrated specific antibody response and significantly suppressed orthotopic tumor growth in the preventive study and lung metastasis in both studies. The underlying mechanisms might include promoting tumor-specific Th1 and CTL-mediated cellular responses and the expression of the effector molecule interferon-γ (IFN-γ), suppressing T-helper type 2 (Th2) responses, and significantly reducing the infiltration of immunosuppressive Treg (regulatory T) cells and myeloid-derived suppressor cells (MDSCs) into tumor tissues in the immunized mice. In conclusion, anti-IL-33 active immunization employing recombinant VLPs as an antigen delivery platform effectively modified the tumor microenvironment and promoted antitumor immunity, indicating the potential of this approach as a new and promising immunotherapeutic strategy for the treatment of cancers where IL-33 plays a definite protumorigenic role. Statement of SignificanceInterleukin (IL)−33 is closely associated with a variety of clinical cancers. IL-33 signaling appears to be a possible target for the treatment of applicable tumor diseases. Recombinant truncated hepatitis B virus core antigen (HBcAg), presenting mature IL-33 molecules on the surface of virus-like particles (VLPs), was prepared and used to immunize BALB/c mice in a model of murine 4T1 breast cancer. The immunization was performed through either a preventive or therapeutic strategy in two separate studies. Anti-IL-33 immunization with VLPs elicited a persistent and highly titrated specific antibody response and significantly suppressed orthotopic tumor growth and lung metastasis in both studies. Furthermore, anti-IL-33 active immunization employing recombinant VLPs as an antigen delivery platform effectively modified the tumor microenvironment and promoted antitumor immunity, indicating its potential as a new and promising immunotherapeutic strategy for the treatment of cancers where IL-33 plays a definite protumorigenic role.

Overcoming Immunological Resistance Enhances the Efficacy of A Novel Anti-tMUC1-CAR T Cell Treatment against Pancreatic Ductal Adenocarcinoma.

Chimeric antigen receptor (CAR) T cells have shown remarkable success in treating hematologic cancers. However, this efficacy has yet to translate to treatment in solid tumors. Pancreatic ductal adenocarcinoma (PDA) is a fatal malignancy with poor prognosis and limited treatment options. We have developed a second generation CAR T cell using the variable fragments of a novel monoclonal antibody, TAB004, which specifically binds the tumor-associated-MUC1 (tMUC1). tMUC1 is overexpressed on ~85% of all human PDA. We present data showing that TAB004-derived CAR T cells specifically bind to tMUC1 on PDA cells and show robust killing activity; however, they do not bind or kill normal epithelial cells. We further demonstrated that the tMUC1-CAR T cells control the growth of orthotopic pancreatic tumors in vivo. We witnessed that some PDA cells (HPAFII and CFPAC) were refractory to CAR T cell treatment. qPCR analysis of several genes revealed overexpression of indoleamine 2, 3-dioxygenases-1 (IDO1), cyclooxygenase 1 and 2 (COX1/2), and galectin-9 (Gal-9) in resistant PDA cells. We showed that combination of CAR T cells and biological inhibitors of IDO1, COX1/2, and Gal-9 resulted in significant enhancement of CAR T cell cytotoxicity against PDA cells. Overcoming PDA resistance is a significant advancement in the field.

Dual Blockade of CD47 and HER2 Re-sensitizes Resistant Breast Cancer Cells to Radiation Therapy

Cancer cells with acquired resistance grow aggressively with a capacity to escape immune surveillance. Here, we aimed to report that CD47, a "do not eat” signal against Mφ-mediated phagocytosis, was concurrently up-regulated with HER2 in radio-resistant breast cancer cells and recurrent tumors, and co-expression of CD47 and HER2 is associated with a worse prognosis. In this study, we aimed to investigate the effect of radiation therapy in CD47 expression and whether NF-kB and/or HER2 is involved in the regulation of CD47 expression in breast cancer. Furthermore, we investigated the enhancement of in vivo phagocytosis in dual knock out cell lines (CD47-/- , HER2-/-) or after dual targeted therapy (anti-CD47, anti-Her2) post radiation. A panel of breast cancer cells, colon cancer cells, and glioblastoma were employed in this study. The cultured cells were irradiated by 5Gy, and the expression of CD47 was analyzed post-irradiation via immunohistochemistry and western blotting. DDAO-labeled wild type and radio resistant MCF7/C6 cells were co-cultured with mature human Mφ derived from the THP1 cell lines with or without CD47 antibody. The tumor aggressiveness phenotype was analyzed by mammosphere formation and matrigel invasion. NF-kB and HER2 in CD47 expression was studied by treating the cells with their respective inhibitors and/or siRNA-mediated depletion and testing the CD47 expression as well as macrophage-mediated phagocytosis of breast cancer cells. The use of anti-CD47 antibody as a strategy to inhibit “don’t eat me” signals was also analyzed by flow cytometry to look at macrophage-based phagocytosis. We generated a radio-resistant mouse breast tumor 4T1/C2 cell, and we used CRISPER technology to establish CD47 and HER2 knock out cell lines. The infiltration of inflammatory cells in the tumor were examined by CD11b+Mφ expression assay. The coordinate induction of CD47 and HER2 was achieved partly by a HER2-NF-κB loop. Antibody blockade of CD47 augmented Mφ-mediated phagocytosis and inhibited an aggressive phenotype. Dual antibody blockade or CRISPR-based dual gene suppression of CD47 and HER2 synergized radiation-mediated inhibition of clonogenicity and growth of orthotopic breast tumors, compared to blockading either receptor alone. These results suggest a network by which cancer cells enhance their aggressive behavior via CD47-mediated suppression of immune surveillance linked with HER2-initiated cell proliferation. Thus, dual blockade of CD47 and HER2 may enhance the eradication of resistant breast cancer cells during radiotherapy.

Ginsenoside Rg3 Prolongs Survival of the Orthotopic Hepatocellular Carcinoma Model by Inducing Apoptosis and Inhibiting Angiogenesis.

Aim Microvessel density is a marker of tumor angiogenesis activity for development and metastasis. Our preliminary study showed that ginsenoside Rg3 (Rg3) induces apoptosis in hepatocellular carcinoma (HCC) in vitro. The aim of this study was to investigate the cross-link for apoptosis induction and antiangiogenesis effect of Rg3 on orthotopic HCC in vivo. Methods The murine HCC cells Hep1-6 were implanted in the liver of mouse. With oral feeding of Rg3 (10 mg/kg once a day for 30 days), the quantitative analysis of apoptosis was performed by using pathology and a transmission electron microscope and microvessel density was quantitatively measured by immunohistochemical staining of the CD105 antibody. The mice treated with Rg3 (n = 10) were compared with the control (n = 10) using Kaplan-Meier analysis. Animal weight and tumor weight were measured to determine the toxicity of Rg3 and antitumor effect on an orthotopic HCC tumor model. Results With oral feeding of Rg3 daily in the first 30 days on tumor implantation, Rg3 significantly decreased the orthotopic tumor growth and increased the survival of animals (P < 0.05). Rg3-treated mice showed a longer survival than the control (P < 0.05). Rg3 treatment induced apoptosis and inhibited angiogenesis. They contributed to the tumor shrinkage. Rg3 initialized the tumor apoptotic progress, which then weakened the tumor volume and its capability to produce the vascularized network for further growth of the tumor and remote metastasis. Conclusion Rg3 inhibited the activation of microtumor vessel formation in vivo besides its apoptosis induction. Rg3 may be used as an adjuvant agent in the clinical HCC treatment regimen.

The Histone Demethylase KDM3A, Increased in Human Pancreatic Tumors, Regulates Expression of DCLK1 and Promotes Tumorigenesis in Mice

The histone lysine demethylase 3A (KDM3A) demethylates H3K9me1 and H3K9Me2 to increase gene transcription and is upregulated in tumors, including pancreatic tumors. We investigated its activities in pancreatic cancer cell lines and its regulation of the gene encoding doublecortin calmodulin-like kinase 1 (DCLK1), a marker of cancer stem cells. We knocked down KDM3A in MiaPaCa-2 and S2-007 pancreatic cancer cell lines and overexpressed KDM3A in HPNE cells (human noncancerous pancreatic ductal cell line); we evaluated cell migration, invasion, and spheroid formation under hypoxic and normoxic conditions. Nude mice were given orthotopic injections of S2-007 cells, with or without (control) knockdown of KDM3A, and HPNE cells, with or without (control) overexpression of KDM3A; tumor growth was assessed. We analyzed pancreatic tumor tissues from mice and pancreatic cancer cell lines by immunohistochemistry and immunoblotting. We performed RNA-sequencing analysis of MiaPaCa-2 and S2-007 cells with knockdown of KDM3A and evaluated localization of DCLK1 and KDM3A by immunofluorescence. We analyzed the cancer genome atlas for levels of KDM3A and DCLK1 messenger RNA in human pancreatic ductal adenocarcinoma (PDAC) tissues and association with patient survival time. Levels of KDM3A were increased in human pancreatic tumor tissues and cell lines, compared with adjacent nontumor pancreatic tissues, such as islet and acinar cells. Knockdown of KDM3A in S2-007 cells significantly reduced colony formation, invasion, migration, and spheroid formation, compared with control cells, and slowed growth of orthotopic tumors in mice. We identified KDM3A-binding sites in the DCLK1 promoter; S2-007 cells with knockdown of KDM3A had reduced levels of DCLK1. HPNE cells that overexpressed KDM3A formed foci and spheres in culture and formed tumors and metastases in mice, whereas control HPNE cells did not. Hypoxia induced sphere formation and increased levels of KDM3A in S2-007 cells and in HPNE cells that overexpressed DCLK1, but not control HPNE cells. Levels of KDM3A and DCLK1 messenger RNA were higher in human PDAC than nontumor pancreatic tissues and correlated with shorter survival times of patients. We found human PDAC samples and pancreatic cancer cell lines to overexpress KDM3A. KDM3A increases expression of DCLK1, and levels of both proteins are increased in human PDAC samples. Knockdown of KDM3A in pancreatic cancer cell lines reduced their invasive and sphere-forming activities in culture and formation of orthotopic tumors in mice. Hypoxia increased expression of KDM3A in pancreatic cancer cells. Strategies to disrupt this pathway might be developed for treatment of pancreatic cancer.

THER-12. PRECLINICAL EVALUATION OF NERATINIB PLUS T-DM1 IN ORTHOTOPIC PDX MODELS OF HER2-POSITIVE BREAST CANCER BRAIN METASTASES

Breast cancer brain metastases (BCBM) are a major cause of morbidity and mortality, despite multimodal management including surgery, radiotherapy, and systemic therapies. There is an urgent need to develop novel, efficacious alternatives. Neratinib is an orally bioavailable, irreversible pan-HER tyrosine kinase inhibitor that is FDA-approved in the extended adjuvant treatment setting for HER2-positive, early breast cancer (NCT00878709). Ado-trastuzumab emtansine (T-DM1) is an antibody-drug conjugate with reported single-agent activity against HER2-positive BCBM. Here, we used HER2-positive orthotopic patient derived xenograft (PDX) models of BCBM to test if combining neratinib with T-DM1 could improve tumor response. PDX cells are labelled with luciferase to allow tumor growth measurement in vivo. We found that neratinib is able to reduce phosphorylated HER2 in an orthotopic PDX tumor derived from HER2-positive BCBM, indicating that neratinib can cross the BBB and inhibit HER2 activation in BCBM PDX tissues. However, in both HER2-positive DF-BM354 and DF-BM355 PDX models, single agent neratinib did not block orthotopic tumor growth compared to vehicle control as monitored by bioluminescence measurements. In contrast, combined treatment of neratinib with T-DM1 significantly reduced tumor growth compared to single agent treatment with neratinib or T-DM1 at earlier time points in both models. At later time points, the combined treatment is comparable to T-DM1 alone in DF-BM354 model, but significantly prolong the survival of mice bearing DF-BM355 tumors. These data warrant further testing of neratinib alone and in combination with T-DM1 in additional BCBM PDX models to better understand drivers of resistance and susceptibility to HER2-inhibitors in HER2-positive BCBMs. Furthermore, they support the launch of a prospective clinical trial (NCT01494662) to test the efficacy and tolerability of T-DM1 in combination with neratinib in patients with progressive HER2-positive BCBM.

Abstract 5296: DNAJA1 promotes cancer progression by stabilizing mutant p53

Abstract The tumor suppressor p53 is mutated in approximately 50% of human cancers. Majority of them are missense mutations, which results in accumulation of dysfunctional p53 proteins in tumors. Increasing evidence suggests that accumulation of mutant p53 is crucial for its oncogenic gain-of-function activities, such as proliferation, metastasis, and chemotherapy resistance. Previous work from our lab has revealed that DNAJA1, a HSP40 family member, specifically binds to and stabilizes conformational/misfolded mutant p53. DNAJA1 downregulation induces ubiquitination and proteasomal degradation of conformational p53 mutants, but does not affect the levels of wild-type p53 or DNA contact mutants. Based on these observations, we hypothesize that DNAJA1 promotes cancer progression in a manner dependent on conformational/misfolded mutant p53. To test this hypothesis, we examined the effects of DNAJA1 deletion/knockdown on malignant properties of head and neck squamous cell carcinoma (HNSCC) cells. Genetic deletion/knockdown of DNAJA1 resulted in reduced proliferation, colony formation, migration, and orthotopic tumor growth of HNSCC cells expressing conformational mutant p53, but not DNA contact mutant p53. These cellular phenotypes induced by DNAJA1 knockdown/knockout were substantially rescued by overexpression of DNAJA1 or mutant p53. We also conducted RNA sequencing analyses using HN31 cells (control, DNAJA1 knockdown or mutant p53 knockdown). Notably, 77.2% of downregulated genes by p53 knockdown were overlapped with genes downregulated by DNAJA1 knockdown. Moreover, genes involved in cancer-related pathways, including adhesion and actin cytoskeleton organization, were commonly downregulated. These results strongly suggest that DNAJA1 promotes HNSCC progression mostly dependent on conformational mutant p53. Our results may also suggest that DNAJA1 could be a novel therapeutic target for cancers carrying conformational/misfolded mutant p53. Citation Format: Tomoo Iwakuma. DNAJA1 promotes cancer progression by stabilizing mutant p53 [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 5296.

Abstract 4832: Preclinical evaluation of neratinib plus T-DM1 in orthotopic PDX models of HER2-positive breast cancer brain metastases

Abstract Up to half of patients with metastatic HER2-positive breast cancer will develop brain metastases. Breast cancer brain metastases (BCBM) are a major cause of morbidity and mortality, despite multimodal management including surgery, radiotherapy, and systemic therapies. Therefore, there is an urgent need to develop novel, efficacious therapies. Neratinib is an orally bioavailable, irreversible pan-HER tyrosine kinase inhibitor that is FDA-approved in the extended adjuvant treatment setting for HER2-positive, early breast cancer. Neratinib has only modest activity as a single agent in clinical trials of patients with HER2-positive brain metastases. Though the combination of neratinib and capecitabine results in CNS responses in up to half of patients, patients eventually develop drug resistance, and toxicities have been a concern-thus exploration of alternative neratinib combinations is of significant clinical interest. Ado-trastuzumab emtansine (T-DM1) is an antibody-drug conjugate with reported single-agent activity against HER2-positive BCBM. Here, we used HER2-positive orthotopic patient derived xenograft (PDX) models of BCBM to test if combining neratinib with T-DM1 could improve tumor response. PDX cells are labelled with luciferase to allow tumor growth measurement in vivo. We found that neratinib is able to reduce phosphorylated HER2 in an orthotopic PDX tumor derived from HER2-positive BCBM, indicating that neratinib can cross the BBB and inhibit HER2 activation in BCBM PDX tissues. However, in the HER2-positive DF-BM354 PDX model, single agent neratinib did not block orthotopic tumor growth compared to vehicle control as monitored by bioluminescence measurements. In contrast, combined treatment of neratinib with T-DM1 significantly reduced tumor growth compared to single agent treatment of neratinib or T-DM1 alone at earlier time points. At later time points, the combined treatment is comparable to T-DM1 alone. These data warrant further testing of neratinib alone or in combination with T-DM1 in additional BCBM PDX models to better understand drivers of resistance and susceptibility to HER2-inhibitors in HER2-positive BCBMs. Furthermore, they support the launch of a prospective clinical trial (NCT01494662) to test the efficacy and tolerability of T-DM1 in combination with neratinib in patients with progressive HER2-positive BCBM. Citation Format: Jing Ni, Yanzhi Wang, Irmina Diala, Sheheryar Kabraji, Rachel Freedman, Nancy Lin, Jean Zhao. Preclinical evaluation of neratinib plus T-DM1 in orthotopic PDX models of HER2-positive breast cancer brain metastases [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 4832.

MicroRNA-301a promotes pancreatic cancer invasion and metastasis through the JAK/STAT3 signaling pathway by targeting SOCS5.

Pancreatic cancer is one of the most lethal digestive malignant tumors. We had previously found that microRNA-301a (miR-301a) is a oncogenic microRNA whose recognized conduce to nuclear factor-kappa B (NF-κB) activation in pancreatic cancer, yet the underlying mechanisms of miR-301a in promoting pancreatic cancer invasion and migration is obscure. In this work we found that high expression of miR-301a in human pancreatic cancer patients is related to poor survival. Overexpression of miR-301a enhances pancreatic cancer cell invasion, angiogenesis and migration, whereas inhibition of miR-301a suppresses pancreatic cancer cell invasion and reduces orthotopic pancreatic tumor growth and metastasis. Furthermore, suppressor of cytokine signaling 5 (SOCS5) is identified as a target gene of miR-301a. We found that miR-301a suppressed the expression of SOCS5 leads to janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3) activation and is related to poor overall survival of pancreatic cancer patients. Taken together, our data show for the first time that the feedback loop between miR-301a and JAK/STAT3 pathway may play a significant role in pancreatic cancer invasion and metastasis. Targeting the loop may prove beneficial to prevent metastasis and provide a more effective therapeutic strategy for pancreatic cancer.

LncRNA HCP5 promotes triple negative breast cancer progression as a ceRNA to regulate BIRC3 by sponging miR-219a-5p.

Emerging evidence has suggested that long noncoding RNAs (lncRNA) involved in the development and progression of cancer. Triple negative breast cancer (TNBC) was an aggressive type of breast cancer with high rates of cancer recurrence and metastasis. The pathogenesis of TNBC is largely unknown. Recent studies suggested that lncRNA HCP5 plays an important role in carcinogenesis. The purpose of this study was to examine the function and mechanism of HCP5 in TNBC. We observed that HCP5 was upregulated in TNBC cell lines and specimens. HCP5 knockdown induced TNBC cell apoptosis, and inhibited cell proliferation and orthotopic xenograft tumor growth. RNA sequencing and antibody array suggested that HCP5 achieves its functions through regulating apoptosis pathway. Bioinformatics, luciferase and RIP experiments proved that both HCP5 and BIRC3 could competitively bind to miR‐219a‐5p. Increased BIRC3 and decreased miR‐219a‐5p were observed in TNBC tissues and cell lines. We then performed gain‐ and loss‐of‐function studies as well as rescue experiments in TNBC cells. The decrease of proliferation and migration due to HCP5 knockdown could be rescued when miR‐219a‐5p inhibitor or BIRC3 was transfected and vice versa. Our study suggested that lncRNA HCP5 promotes TNBC progression as a ceRNA to regulate BIRC3 by sponging miR‐219a‐5p. In a word, we revealed a new signaling pathway to mediate TNBC, and provided HCP5 as a new target for improving treatment of TNBC.

Co-Delivery of Natural Compounds with a Dual-Targeted Nanoparticle Delivery System for Improving Synergistic Therapy in an Orthotopic Tumor Model.

Various natural compounds including epigallocatechin gallate (EGCG) and curcumin (CU) have potential in developing anticancer therapy. However, their clinical use is commonly limited by instability and low tissue distribution. EGCG and CU combined treatment can improve the efficacy with synergistic effects. To improve the synergistic effect and overcome the limitations of low tissue distribution, we applied a dual cancer-targeted nanoparticle system to co-deliver EGCG and CU. Nanoparticles were composed of hyaluronic acid, fucoidan, and poly(ethylene glycol)-gelatin to encapsulate EGCG and CU. Furthermore, a dual targeting system was established with hyaluronic acid and fucoidan, which were used as agents for targeting CD44 on prostate cancer cells and P-selectin in tumor vasculature, respectively. Their effect and efficacy were investigated in prostate cancer cells and a orthotopic prostate tumor model. The EGCG/CU-loaded nanoparticles bound to prostate cancer cells, which were uptaken more into cells, leading to a better anticancer efficiency compared to the EGCG/CU combination solution. In addition, the releases of EGCG and CU were regulated by their pH value that avoided the premature release. In mice, treatment of the cancer-targeted EGCG/CU-loaded nanoparticles significantly attenuated the orthotopic tumor growth without inducing organ injuries. Overall, the dual-targeted nanoparticle system for the co-delivery of EGCG and CU greatly improved its synergistic effect in cancer therapy, indicating its great potential in developing treatments for prostate cancer therapy.

Recombinant Virus-Like Particles Presenting IL-33 Successfully Modify the Tumor Microenvironment and Facilitate Antitumor Immunity in a Model of Breast Cancer

Recently, interleukin (IL)-33 has been closely associated witha variety of clinical cancers. IL-33 presents both protumorigenic, and less frequently, antitumorigenic functions depending on disease conditions. IL-33 signaling appears to be a possible target for the treatment of applicable tumor diseases. This study aimed to develop an effective approach to intervene in IL-33 functioning in tumors and reveal the immunotherapeutic potential of anti-IL-33 active immunization. Recombinant truncated hepatitis B virus core antigen (HBcAg), presenting mature IL-33 molecules on the surface of virus-like particles (VLPs), was prepared and used to immunize BALB/c mice in a model of murine 4T1 breast cancer. The immunization was performed through either a preventive or therapeutic strategy in two separate studies. Anti-IL-33 immunization with VLPs elicited a persistent and highly titrated specific antibody response and significantly suppressed orthotopic tumor growth and lung metastasis in both studies. The underlying mechanisms might include promoting tumor-specific Th1/CTL cellular responses and the expression of the effector molecule IFN-γ, suppressing Th2 responses, and significantly reducing the infiltration of immunosuppressive Treg cells and MDSCs into tumor tissues in the immunized mice. In conclusion, anti-IL-33 active immunization employing recombinant VLPs as an antigen delivery platform effectively modified the tumor microenvironment and promoted antitumor immunity, indicating the potential of this approach as a new and promising immunotherapeutic strategy for the treatment of cancers where IL-33 plays a definite protumorigenic role.

Magnesium transporter protein solute carrier family 41 member 1 suppresses human pancreatic ductal adenocarcinoma through magnesium-dependent Akt/mTOR inhibition and bax-associated mitochondrial apoptosis.

The aim of this study was to identify the function of the Mg2+ transporter protein solute carrier family 41 member 1 SLC41A1 in pancreatic ductal adenocarcinoma and the underlying mechanisms. A total of 27 solute carrier proteins were differentially expressed in pancreatic ductal adenocarcinoma. Three of these proteins were correlated with clinical outcomes in patients, among which SLC41A1 was downregulated in tumour. Overexpression of SLC41A1 suppressed orthotopic tumour growth in a mouse model and reduced the cell proliferation, colony formation, and invasiveness of KP3 and Panc-1 cells, which may have been associated with the increased population of apoptotic-prone cells. Overexpression of SLC41A1 reduced the mitochondrial membrane potential, induced Bax while suppressed Bcl-2 expression. Suppression of Bax abrogated the tumour-suppressive effects of SLC41A1. Furthermore, overexpression of SLC41A1 promoted Mg2+ efflux and suppressed Akt/mTOR activity, which is the upstream regulator of Bax and Bcl-2. An increase in Akt activity and supplementation with Mg2+ abolished SLC41A1-induced tumour suppression. The results of this study suggest that SLC41A1 may be a potential target for the treatment of pancreatic ductal adenocarcinoma.