CT26 Murine Colon Carcinoma Cells Research Articles

Abstract 4896: Role of CDK8 in colon cancer hepatic metastasis

Abstract About half of all colon cancer patients will develop liver metastases and the 5-year survival for these patients is less than 13%, making colon cancer the second most lethal cancer worldwide. Cyclin dependent kinase 8 (CDK8), which regulates transcription but not cell cycle progression, has been identified as an oncogene amplified in many colon cancers. CDK8 acts as a positive mediator of oncogenic transcription pathways regulated by Wnt/beta-catenin and TGF-beta, both of which are strongly associated with tumor metastasis. In a colon cancer liver metastasis model based on splenic injection of CT26 murine colon carcinoma cells, treatment with Senexin B, a highly selective small-molecule inhibitor of CDK8 and its paralog CDK19, strongly inhibited metastatic growth in the liver and prolonged the survival of mice with hepatic metastases. In contrast to the effect on liver metastasis, CDK8 inhibition had little or no effect on cell growth in culture or at primary tumor sites. Hepatic metastasis was inhibited to the same extent when Senexin B was administered starting from the time of tumor injection or only during a later part of the study, suggesting that the drug affected metastatic growth in the liver rather than just initial colonization. Liver metastasis was similarly decreased by CDK8 knockdown in CT26 cells, suggesting that the anti-metastatic activity of Senexin B was due at least in part to its effect on tumor cells. Transcription profiling indicated that CDK8 inhibition by shRNA or Senexin B strongly decreased the expression of metastasis-associated metalloproteinases MMP 13, MMP10, and MMP3 and at the same time drastically increased the expression of TIMP3, a metalloproteinase inhibitor. TIMP3 overexpression in CT26 cells, like CDK8 inhibition, decreased hepatic metastasis. CDK8 inhibition also blocked TGF-beta or Wnt3a-stimulated transwell Matrigel invasion of CT26 cells in vitro. Knockdown of beta-catenin in CT26 cells decreased the expression of MMP3 and MMP13, while knockdown of SMAD4 (transcriptional mediator of TGF-beta pathway) induced TIMP3 expression. Beta-catenin knockdown decreased both the primary tumor growth in the spleen and metastatic growth in the liver, whereas SMAD4 knockdown, like that of CDK8, selectively inhibited liver metastasis. Senexin B also suppressed hepatic metastasis after splenic injection of human HCT116 colon carcinoma cells. In summary, our data identified CDK8 as a key transcriptional regulator of colon cancer metastatic growth in the liver, interacting with TGF-beta and Wnt/beta-catenin pathways and regulating the expression of MMPs and Timp3. CDK8/19 inhibitors, which are now entering clinical trials, may be effective for the treatment of hepatic metastasis of colon cancer. Citation Format: Jiaxin Liang, Mengqian Chen, Mythreye Karthikeyan, M. Marjorette Pena, Daniel Hughes, Vimala Kaza, Chang-Uk Lim, Eugenia Broude, Igor B. Roninson. Role of CDK8 in colon cancer hepatic metastasis [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 4896. doi:10.1158/1538-7445.AM2017-4896

Abstract LB-198: Combination of PEGylated recombinant hyaluronidase PH20 (PEGPH20) with live-attenuated, double-deleted (LADD) Listeria enhances tumor infiltrating CD8+ T cell response and antitumor efficacy in mice

Abstract Successful immunotherapy is highly dependent on inducing an efficient CD8+ T cell-mediated antitumor immune response. The trafficking and activation of these effector CD8+ T cells are often inhibited by various immunosuppressive mechanisms in the tumor microenvironment (TME). Hyaluronan (HA), a glycosaminoglycan that accumulates in the TME of many solid tumors, is associated with rapid tumor progression, poor prognosis and increased immunosuppression. We have previously demonstrated in nonclinical models that enzymatic degradation of TME HA by intravenous PEGylated recombinant human hyaluronidase PH20 (PEGPH20) facilitates delivery of chemotherapeutics to tumors and enhances checkpoint inhibitor efficacy. Based on these observations we hypothesized that PEGPH20 may improve current cancer immunotherapies by increasing immune cell infiltration into tumors. To test this hypothesis we used CT26/HAS3 tumors, CT26 murine colon carcinoma cells engineered to over-express hyaluronan synthase-3, and treated them with PEGPH20 in combination with recombinant live-attenuated double-deleted strains of Listeria monocytogenes expressing AH1 (gp70423-431, SPSYVYHQF), the immunodominant CD8+ T cell epitope of CT26 (LADD-AH1). PEGPH20 (1mpk), which results in nearly complete removal of HA at 24hrs, was administered 24hrs prior to LADD-AH1. In this model, LADD-AH1 alone inhibited tumor growth which correlated with an increase in IFNγ+ (p=0.0019) and granzyme B+ CD8+ tumor infiltrating lymphocytes (TILs) (p=0.0006). Tumor-associated macrophages (TAMs) from LADD-AH1 treated tumors were more immunostimulatory with a decrease in MHCIIlow (p=0.0205) and CD206+ TAMs (p=0.0003). Moreover, the combination of PEGPH20 and LADD-AH1 resulted in enhanced anti-tumor activity compared to either PEGPH20 (p=0.0047) or LADD-AH1 alone (p=0.0002). Significant TME changes were observed in the combination treatment with an increase in CD8+ TILs (p=0.0200, of which 88% were granzyme B+), NK cells (p=0.0205) and an increase in CD8:Treg ratio (p=0.0007).These findings were corroborated by immunohistochemical analysis demonstrating an increase in CD3+ T cells with PEGPH20 treatment. Taken together, these data suggest that HA accumulation in tumors may act as a barrier to immune cell access and that reduction of HA by PEGPH20 facilitates increased accumulation of tumor antigen-specific CD8+ effector T cells induced by LADD immunotherapy. Our findings reveal a benefit of PEGPH20 in enhancing tumor infiltration of cytotoxic CD8+ T cells induced by LADD that translate into a significant improvement in efficacy in a murine model of HA-high tumors. Citation Format: Jisook Lee, Meredith Leong, Yujun Huang, Benjamin J. Thompson, Sanna Rosengren, Barbara Blouw, Dirk G. Brockstedt, Curtis B. Thompson. Combination of PEGylated recombinant hyaluronidase PH20 (PEGPH20) with live-attenuated, double-deleted (LADD) Listeria enhances tumor infiltrating CD8+ T cell response and antitumor efficacy in mice [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 LB-198. doi:10.1158/1538-7445.AM2017-LB-198

Arsenic trioxide inhibits lung metastasis of mouse colon cancer via reducing the infiltration of regulatory T cells.

The purpose of this study was to investigate the effects of arsenic trioxide (As2O3) on the infiltration of regulatory T cells (Tregs) in the local lung metastasis of mouse colon cancer in vivo and the regulation of Tregs in cytokine-induced killer cells (CIKs) in vitro. A high Tregs infiltration mouse colon cancer lung metastasis model was established by intravenous injection of CT26 murine colon carcinoma cells. Tumor-bearing mice were randomly divided into three groups: control group, low-dose As2O3 group, and high-dose As2O3 group. For in vitro studies, CIKs were treated with vehicle control or 0.1, 1, or 5 μM As2O3. The level of Tregs was detected via flow cytometry, Foxp3 expression was assessed by immunohistochemistry and reverse transcription–polymerase chain reaction (RT-PCR), the level of interferon gamma (IFN-γ) was evaluated by enzyme-linked immunoassay (ELISA), and the cytotoxic activity of As2O3-treated CIKs was assessed through a lactate dehydrogenase (LDH) release assay. Obvious lung metastasis was observed 3 days after CT26 murine colon carcinoma cell injection. The numbers of Tregs in the lungs and spleens of tumor-bearing mice were significantly higher than those of the normal group (p < 0.01). As2O3 treatment increased the mouse weight as well as reduced the number of metastatic lung nodules and the lung/body weight ratio (p < 0.01). Moreover, As2O3 treatment significantly reduced the Tregs proportion and the Foxp3 messenger RNA (mRNA) levels in metastatic lung tissues (p < 0.01). In vitro, As2O3 significantly reduced the Tregs proportion and the Foxp3 mRNA levels (p < 0.01) and significantly increased the cytotoxic activity of CIKs and the IFN-γ levels in the supernatant of cultured CIKs (p < 0.01). As2O3 might inhibit lung metastasis of colon cancer by reducing the local infiltration of Tregs and increase the cytotoxic activity of CIKs by suppressing Tregs.

Enhancement of oxaliplatin-induced cell apoptosis and tumor suppression by 3-methyladenine in colon cancer.

Oxaliplatin (OX) has been widely used in adjuvant and palliative treatments of advanced colon cancer; however, cancer cells ultimately become resistant in the majority of cases. Therefore, the development of a novel strategy to overcome this resistance is important for the effective treatment of colon cancer. Cell autophagy reduces the sensitivity of cancer cells to therapeutic reagents in various types of human cancer; therefore, the present study used murine CT26 colon carcinoma cells to explore whether inhibition of autophagy by 3-methyladenine (3-MA) is able to enhance OX-induced apoptosis in vitro and OX-suppressed tumor growth in vivo. CT26 cells were treated with 3-MA, OX, or 3-MA plus OX, and the autophagy, apoptosis and proliferation of the CT26 cells was investigated. Additionally, the therapeutic efficiency of the combination of 3-MA and OX treatment was evaluated in vivo by determining the survival time of the tumor-bearing mice and, thus, tumor growth rate. The treatment of CT26 cells in vitro with OX alone increased autophagy as well as apoptosis, whereas treatment with 3-MA plus OX markedly inhibited OX-induced autophagy, but increased OX-induced cell apoptosis. Furthermore, the combination of OX and 3-MA treatment significantly suppressed tumor growth in vivo and prolonged mouse survival time when compared with OX treatment alone. Similarly, 3-MA increased OX-induced cell apoptosis and decreased autophagy in xenograft tumor tissues. Thus, the administration of 3-MA may increase tumor cell sensitivity to OX by reducing its autophagic effects and enhancing its apoptotic effects. Data obtained in the present study indicates that the clinical combination of an autophagy inhibitor with OX may increase the therapeutic effect of OX and improve the clinical outcome of patients with colon cancer.

Hyper-IL-15 suppresses metastatic and autochthonous liver cancer by promoting tumour-specific CD8+ T cell responses

Liver cancer has a very dismal prognosis due to lack of effective therapy. Here, we studied the therapeutic effects of hyper-interleukin15 (hyper-IL-15), which is composed of IL-15 and the sushi domain of the IL-15 receptor α chain, on metastatic and autochthonous liver cancers. Liver metastatic tumour models were established by intraportally injecting syngeneic mice with murine CT26 colon carcinoma cells or B16-OVA melanoma cells. Primary hepatocellular carcinoma (HCC) was induced by diethylnitrosamine (DEN). A hydrodynamics-based gene delivery method was used to achieve sustained hyper-IL-15 expression in the liver. Liver gene delivery of hyper-IL-15 robustly expanded CD8(+) T and NK cells, leading to a long-term (more than 40 days) accumulation of CD8(+) T cells in vivo, especially in the liver. Hyper-IL-15 treatment exerted remarkable therapeutic effects on well-established liver metastatic tumours and even on DEN-induced autochthonous HCC, and these effects were abolished by depletion of CD8(+) T cells but not NK cells. Hyper-IL-15 triggered IL-12 and interferon-γ production and reduced the expression of co-inhibitory molecules on dendritic cells in the liver. Adoptive transfer of T cell receptor (TCR) transgenic OT-1 cells showed that hyper-IL-15 preferentially expanded tumour-specific CD8(+) T cells and promoted their interferon-γ synthesis and cytotoxicity. Liver delivery of hyper-IL-15 provides an effective therapy against well-established metastatic and autochthonous liver cancers in mouse models by preferentially expanding tumour-specific CD8(+) T cells and promoting their anti-tumour effects.

IGF1R blockade with ganitumab results in systemic effects on the GH–IGF axis in mice

Ganitumab is a fully human MAB to the human type 1 IGF receptor (IGF1R). Binding assays showed that ganitumab recognized murine IGF1R with sub-nanomolar affinity (KD=0.22 nM) and inhibited the interaction of murine IGF1R with IGF1 and IGF2. Ganitumab inhibited IGF1-induced activation of IGF1R in murine lungs and CT26 murine colon carcinoma cells and tumors. Addition of ganitumab to 5-fluorouracil resulted in enhanced inhibition of tumor growth in the CT26 model. Pharmacological intervention with ganitumab in naïve nude mice resulted in a number of physiological changes described previously in animals with targeted deletions of Igf1 and Igf1r, including inhibition of weight gain, reduced glucose tolerance and significant increase in serum levels of GH, IGF1 and IGFBP3. Flow cytometric analysis identified GR1/CD11b-positive cells as the highest IGF1R-expressing cells in murine peripheral blood. Administration of ganitumab led to a dose-dependent, reversible decrease in the number of peripheral neutrophils with no effect on erythrocytes or platelets. These findings indicate that acute IGF availability for its receptor plays a critical role in physiological growth, glucose metabolism and neutrophil physiology and support the presence of a pituitary IGF1R-driven negative feedback loop that tightly regulates serum IGF1 levels through Gh signaling.

Changes of T Cells and Cytokines TGF-β1 and IL-10 in Mice During Liver Metastasis of Colon Carcinoma: Implications for Liver Anti-tumor Immunity

BackgroundThe local and systemic regulation of the immune system may play important roles in the process of liver metastasis of colorectal carcinoma. The aim of this study was to establish a reproducible experimental liver metastasis model, to identify changes in T cells and cytokines TGF-β1 and IL-10, and to explore a possible mechanism of liver metastasis of colon carcinoma. MethodsWe used a colon carcinoma liver metastasis model, in which different numbers of CT-26 murine colon carcinoma cells (1 × 103, 5 × 103, 1 × 104, 5 × 104, and 1 × 105) were injected into the spleen. The liver and spleen tissues were examined for T cell markers using flow cytometry. Liver tissues were analyzed for IL-10 and transforming growth factor beta 1 (TGF-β1) expression using immunohistochemistry. ResultsSpleen injection of colon carcinoma cells is a reproducible animal model for liver metastases, which resulted in quantity-dependent metastatic growth. We provided a snapshot of the hepatic immune microenvironment in the mouse liver metastasis model. Injection of A large number of tumor cells (5 × 104 and 1 × 105) decreased anti-tumor cell counts, such as CD4+ and CD8+ T cells, and increased immune-suppressive cell counts (CD4+CD25+ Treg cells). In addition, the expression levels of immunosuppressive cytokines IL-10 and TGF-β1 were also increased with the number of tumor cells. ConclusionsChanges in the systemic and local immunological environment contribute to immunological escape mechanisms during liver metastasis of colon carcinoma, and therapies aiming at immune microenvironment may prove a useful strategy in the treatment of metastatic disease in the future.

Hericium erinaceus (Lion’s Mane) Mushroom Extracts Inhibit Metastasis of Cancer Cells to the Lung in CT-26 Colon Cancer-Tansplanted Mice

This study investigated the antimetastatic activity of four Hericium erinaceus edible mushroom extracts using CT-26 murine colon carcinoma cells as an indicator of inhibition of cell migration to the lung. Hot water (HWE) and microwaved 50% ethanol (MWE) extracts of H. erinaceus strongly elicited cancer cell death through apoptosis and inhibited metastasis of cancer cells to the lungs by 66% and 69%, respectively. HWE and MWE reduced the expression of matrix metalloproteinases MMP-2 and MMP-9 in cells and their activities in culture media. Urokinase-type plasminogen activator (u-PA), another extracellular matrix (ECM)-degrading proteinase, also showed decreased protein expression. In CT-26 cells, HWE and MWE down-regulated extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 mitogen-activated protein kinase (MAPK) phosphorylations. The reduced phosphorylations seem to cause reduction of activity of the MMPs, thereby blocking migration and invasion of cells. Dietary administration of HWE and MWE reduced the formation of tumor nodules in the lung by about 50% and 55%, respectively, and prevented increases in lung weight caused by cancer cell metastasis. These results demonstrate the effectiveness of HWE and MWE as beneficial antimetastatic agents, targeting their upstream signaling molecules for mediating the expression of the ECM-degrading proteinases. Acidic and alkaline extracts were not bioactive. Bioactivity seems to be related to composition. H. erinaceus edible mushrooms have the potential to serve as a health-promoting functional food.

Abstract 5347: MiRNA expression profile of tumor microenvironment in murine liver metastatic model.

Abstract Colorectal cancer (CRC) is the second most recurrent cancer type and one of the most lethal diseases around the worldwide. The lethality of the CRC is due to the metastasis and the principal target is the liver. Although the main responsible of the metastasis is the cancer cell we can not obviate the crucial role of the host organ and how the cells of the host organ support the progression of the disease. The crosstalk of the tumor microenvironment with the tumor has been deeply studied from the cellular point of view but the regulatory pathways of these processes still remain unknown. The epigenetic regulation has been postulated as one important process implicated in the regulation of cellular changes. The microRNA (miRNA) expression is one of the variants of the epigenetic regulation. In this work we study the deregulation of the miRNA expression in the metastasized liver respect to healthy condition using a murine in vivo liver metastasis model. We inoculated CT26 murine colon carcinoma cell intrasplenically in BALB/c mice and after 15 days we sacrificed the animals to obtain four liver cell types (hepatocytes, liver sinusoidal endothelial cells, Kupffer cells and hepatic stellate cells). Then we isolated the total RNA and performed gene expression and miRNA expression microarrays (Agilent) comparing the tumor received cells with control cells (PBS injected animal's cells). The gene expression microarray helps us finding the biological and cellular sense of the deregulated miRNAs and could be an important data source to elucidate the therapeutic option of each deregulated miRNAs. An in vivo approach is a more realistic model that can show more elements implicated in the crosstalk of the different liver cell types. This fact show us several results in the different cell types with expected and unexpected new miRNA deregulations. For instance downregulation of miR-16 and miR-15b and upregulation of miR-138 has been found in hepatic stellate cells with important role in activation proliferation and apoptosis of this cell type and we also observed deregulation of miR-135 in liver sinusoidal cells. These are some of the examples of a large amount of miRNA identified. Nowadays we are checking the role of each deregulated miRNA in the cellular processes to verify their implication in the metastatic progression and postulate them as therapeutic targets. Citation Format: Joana Marquez, Arianne Schaub, Maite Unzurrunzaga, Patricia Garcia, Iker Badiola. MiRNA expression profile of tumor microenvironment in murine liver metastatic model. [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 5347. doi:10.1158/1538-7445.AM2013-5347

Preparation and Characterization of Chitosan/β-cyclodextrin Nanoparticles Containing Plasmid DNA Encoding Interleukin-12

Interleukin-12 (IL-12) as a cytokine has been proved to possess antitumor effects via stimulating the immune system. Non-viral gene delivery systems offer several advantages, including easiness in production, low cost, safety; low immunogenicity and can carry higher amounts of genetic material without limitation on their sizes.pUMVC3-hIL12 loaded Low Molecular Weight chitosan/β-cyclodextrin (LMW CS/CD) nanoparticles were prepared using ionotropic gelation method and characterized in terms of size, zeta potential, polydispersity index, morphology, loading efficiency and cytotoxicity against the CT-26 colon carcinoma cell line.All prepared particles were spherical in shape and nano-sized (171.3±2.165 nm, PdI: 0.231±0.014) and exhibited a positive zeta potential (34.3±1.55). The nanoparticles demonstrated good DNA encapsulation efficiencies (83.315%±2.067). Prepared pUMVC3-hIL12 loaded LMW CS/CD nanoparticles showed no cell toxicity in murine CT-26 colon carcinoma cells. At the concentration of 0.1 µg/ml of nanoparticles, the transfection ability was obviously higher than that of the naked DNA.LMW CS/CD-plasmid DNA nanoparticles encoding IL-12 prepared using ionotropic gelation method with no toxic effect on the tested cells can be considered as a basis for further gene delivery studies both in vitro and in vivo to enhance the expression of IL-12.

Preparation of Chitosan-Plasmid DNA Nanoparticles Encoding Interleukin-12 and their Expression in CT-26 Colon Carcinoma Cells

Interleukin-12 (Il-12) as a cytokine has been proved to possess antitumor effects via stimulating the immune system. Non-viral gene delivery systems exhibit low toxicity and are easier to prepare compared to their viral counterparts. In this study, we aimed to prepare plasmid DNA loaded chitosan nanoparticles for expression of Il-12 and to evaluate their physicochemical characteristics, cytotoxicity and transfection efficiency in Murine CT-26 colon carcinoma cells. Nanoparticles were prepared using a complex coacervation process at different N/P ratios and characterized in terms of size, zeta potential, polydispersity index, morphology, encapsulation efficiency and polyplex formation. The cytotoxicities and transfection efficiencies of the prepared polyplexes were evaluated by MTT assay and ELISA (for hIL-12, p70), respectively. Size and zeta potential varied from 76.73 to 867.03 nm and between 5.68 and 16.77 mV, respectively. Strong attachment of the DNA to chitosan was observed after polyplex preparation. Encapsulation efficiencies were high (72.97-94.87%). The transfection efficiencies of the prepared complexes were obviously higher than those of naked pDNA when N/P ratios were between 16 and 60. Maximum level of phIL-12 expression was obtained at (N/P = 16) with mean particle size of 381.83±82.77 nm (polydispersity index=0.44) indicating the improved transfection of pUMVC3-hIL12 about 2.80 times compared to that of the naked pUMVC3-hIL12. Prepared polyplexes were nontoxic to CT-26 cells. Chitosan-DNA nanoparticles at N/P = 16 with minimal cytotoxicity, can be used as suitable candidate for Il-12 delivery. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

Involvement of oxidative stress in simvastatin-induced apoptosis of murine CT26 colon carcinoma cells

Recent studies have suggested that oxidative stress may play a role in the cytotoxic activity of statins against cancer cells. The objective of this study was to elucidate the role of oxidative stress in the cytotoxicity of simvastatin in murine CT26 colon carcinoma cells and B16BL6 melanoma cells. We found that CT26 cells were more sensitive to simvastatin than B16BL16 cells. Interestingly, exposure to simvastatin causes significant apoptotic cell death and perturbations in parameters indicative of oxidative stress in CT26 cells. Moreover, the increase in oxidative stress parameters and cell death were suppressed by isoprenoids including mevalonolactone, farnesyl pyrophosphate ammonium salt, geranylgeranyl pyrophosphate ammonium salt, and coenzyme Q10, and by antioxidants including N-acetyl cysteine, reduced glutathione, superoxide dismutases (SOD), and catalase (CAT) alone or in combination, but were promoted by an inhibitor of glutathione synthesis, l-buthionine-sulfoximine. The signaling pathway induced by simvastatin breaks down the antioxidant defense system by suppressing the expression of reactive oxygen species scavengers, particularly Mn-SOD, CAT, GPx1, and SESN 3, thereby inducing oxidative stress and apoptotic cell death. Collectively, our results demonstrate that simvastatin induces colon cancer cell death at least in part by increasing intracellular oxidative stress and inducing apoptosis.

Chemotherapy-induced myelotoxicity and incidence of lung metastasis in an animal model

We examined how chemotherapy-induced myelotoxicity and the associated leukopaenia affect cancer metastasis in an animal model. Myelotoxicity was induced by a single injection of 5-fluorouracil (5-FU) or Cisplatin, administered to 7-week-old BALB/c mice. CT-26 murine colon carcinoma cells were injected into the lateral tail vein on days 0, 1, 3, 5, and 7 after anticancer drug injection. On day 14 after cancer cell injection, the number of pulmonary colonies was measured in a double-blind setting. Compared with Cisplatin, 5-FU induced severe leukopaenia and bone marrow suppression, while on day 5, both drugs induced severe myelotoxicity. The number of pulmonary colonies did not correlate with the severity of leukopaenia, regardless of the type or time of drug injection, except in the group pretreated with Cisplatin (3 days prior to cancer cell injection). Our results suggest that chemotherapy-induced myelotoxicity does not increase the incidence of cancer metastasis in this animal model.

RNAPc2 Inhibits Colorectal Cancer in Mice through Tissue Factor

Recombinant nematode anticoagulant protein c2 (rNAPc2) is a specific inhibitor of tissue factor (TF)/factor VIIa complex with novel antithrombotic activity. TF is highly expressed in human colorectal tumors, and levels are positively correlated with disease progression. To explore the therapeutic potential and mechanism of action of rNAPc2 during tumor growth and metastasis, we tested rNAPc2 in several experimental colorectal cancer models in mice. Administration of rNAPc2 inhibited pulmonary metastasis in mice systemically disseminated with CT26 murine colon carcinoma cells in a dose-dependent fashion. Combining rNAPc2 with the cytotoxic agent 5-fluorouracil or bevacizumab (humanized anti-vascular endothelial growth factor monoclonal antibody) resulted in additive growth inhibition and simultaneous reduction of microvessel density in HCT116 human colorectal tumor xenografts in nude mice. Furthermore, rNAPc2 potentiated CPT-11 in inhibiting hepatic metastasis in nude mice with portal vein injection of HCT116 tumor cells. Long-term administration of rNAPc2 significantly suppressed spontaneous formation of intestinal tumors in Apc(Min/+) mice. Using a RNA interference approach, we showed that TF expression is necessary for rNAPc2-mediated inhibition of HCT116 human colorectal tumor xenograft growth in nude mice, indicating that the antitumor effect of rNAPc2 may be transduced through TF that is expressed on tumor cells. rNAPc2 is a potent anticancer agent when used in combination with chemotherapy or antiangiogenic therapy in mouse models of colorectal cancer, and TF positivity appears to be required for its activity.

RNAPc2, a Novel Inhibitor of Tissue Factor/Factor VIIa Complex, Inhibits Tumor Growth and Metastasis in Mouse Models of Colorectal Cancer.

Recombinant nematode anticoagulant protein c2 (rNAPc2) is a specific inhibitor of tissue factor (TF)/factor VIIa complex with novel anti-metastatic, anti-angiogenic, and anti-thrombotic activities. TF is highly expressed in human colorectal tumors and the level of TF expression positively correlates with disease stage and inversely correlates with survival. To explore the therapeutic potential of rNAPc2 during tumor growth and metastasis, we tested rNAPc2 efficacy in experimental colorectal cancers in mice. Administration of rNAPc2 inhibited pulmonary metastasis in mice systemically disseminated with CT26 murine colon carcinoma cells in a dose-dependent fashion, as measured by either number of lung surface metastases or lung mass. While rNAPc2 treatment alone moderately reduced primary tumor growth, combining rNAPc2 with the cytotoxic agent 5-fluorouracil (5-FU) resulted in synergistic growth inhibition of HCT116 human colorectal tumor xenografts in nude mice. Likewise, rNAPc2 further reduced tumor growth in HCT116 human colorectal tumor xenograft-bearing mice receiving bevacizumab (humanized anti-vascular endothelial growth factor monoclonal antibody). Using CD31 and Ki67 immunohistochemisty, we found that rNAPc2 synergized with either 5-FU or bevacizumab in inhibiting microvessel density and tumor cell proliferation in HCT116 human colorectal tumor xenografts. Furthermore, rNAPc2 synergized with CPT-11 in inhibiting hepatic metastasis in nude mice with portal vein injection of HCT116 human colorectal tumor cells. Long-term administration of rNAPc2 also significantly suppressed formation of intestinal adenomas and adenocarcinomas in ApcMin/+ mice. The dosing regimens of rNAPc2 used in these studies were well tolerated up to a three-month period by recipient mice without major hemorrhage or other adverse effects. In conclusion, the synergistic tumor inhibitory activity of rNAPc2 in pre-clinical colorectal cancer models suggests that rNAPc2 may be an effective anti-tumor agent in human colorectal cancer patients to potentiate chemo- or anti-angiogenic therapies.

Inhibition of In Vivo Tumor Angiogenesis and Growth Via Systemic Delivery of an Angiopoietin 2-Specific RNA Aptamer

Cellular events mediated by the Tie2 receptor are important to tumor neovascularization. Despite the complex interplay of the best-characterized Tie2 ligands, angiopoietins 1 and 2, Ang2 is purportedly "proangiogenic" in the presence of vascular endothelial growth factor. We examined whether in vivo administration of an RNA aptamer that specifically blocks Ang 2 would inhibit tumor angiogenesis and growth. Ang2-mediated Tie2 receptor phosphorylation was assessed in vitro in the absence and presence of aptamer coupled to polyethylene glycol. IN VIVO ANGIOGENESIS ASSAY: CT26 murine colon carcinoma cells expressing green fluorescent protein were delivered into mouse dorsal skinfold window chambers. Animals received daily intraperitoneal injections of phosphate-buffered saline, low-dose (Ang2 aptamer-LD; 1 mg/kg/d), or high-dose aptamer (Ang2 aptamer-HD; 10 mg/kg/d). Vascular length density was measured under fluorescence microscopy. PRIMARY TUMOR GROWTH: CT26 cells expressing luciferase were injected into flanks of BALB/c mice to allow tumor growth monitoring by bioluminescence imaging. Animals received continuous phosphate-buffered saline or aptamer (1 mg/kg/d) via ALZET pumps. Tumors were assessed for CD31/PECAM-1 immunostaining and Hoechst dye uptake. Pegylated aptamer inhibited Tie2 phosphorylation. Systemic aptamer administration reduced vascular length density (P < or = 0.03) and decreased bioluminescence emission (P < 0.04), corresponding to 50% decrease in tumor volume (P = 0.04). Control tumors displayed abundant vascular marker staining, in contrast to tumors from aptamer-treated animals. in vivo administration of a clinically relevant, pegylated RNA aptamer specifically designed against Ang2 inhibited tumor angiogenesis and growth. These findings support targeted Ang2 inhibition as a relevant anti-angiogenic, anti-neoplastic strategy.

Attenuation of Colon Carcinoma Tumor Spread by Intravenous Immunoglobulin

The impact of IVIg on metastatic capacity of CT26 murine colon carcinoma cells was studied using in vitro and in vivo methods. IVIg inhibited CT26 cell proliferation and invasion through an extracellular matrix in a dose- and time-dependent manner. Systemic treatment of mice with IVIg significantly inhibited metastatic potential of CT26 colon carcinoma cells observed as tumor nodules and lung weight reduction. Treating CT26 cell-implanted rabbit corneas with IVIg led to shrinking and complete disappearance of tumor mass in 10 days. These results provide the evidence that IVIg may be considered as a supportive therapy for inhibition of colon carcinoma tumor spread.

N-(4-iodophenyl)-N′-(2-chloroethyl)urea as a microtubule disrupter: in vitro and in vivo profiling of antitumoral activity on CT-26 murine colon carcinoma cell line cultured and grafted to mice

The antitumoral profile of the microtubule disrupter N-(4-iodophenyl)-N′-(2-chloroethyl)urea (ICEU) was characterised in vitro and in vivo using the CT-26 colon carcinoma cell line, on the basis of the drug uptake by the cells, the modifications of cell cycle, and β-tubulin and lipid membrane profiles. N-(4-iodophenyl)-N′-(2-chloroethyl)urea exhibited a rapid and dose-dependent uptake by CT-26 cells suggesting its passive diffusion through the membranes. Intraperitoneally injected ICEU biodistributed into the grafted CT-26 tumour, resulting thus in a significant tumour growth inhibition (TGI). N-(4-iodophenyl)-N′-(2-chloroethyl)urea was also observed to accumulate within colon tissue. Tumour growth inhibition was associated with a slight increase in the number of G2 tetraploid tumour cells in vivo, whereas G2 blockage was more obvious in vitro. The phenotype of β-tubulin alkylation that was clearly demonstrated in vitro was undetectable in vivo. Nuclear magnetic resonance analysis showed that cells blocked in G2 phase underwent apoptosis, as confirmed by an increase in the methylene group resonance of mobile lipids, parallel to sub-G1 accumulation of the cells. In vivo, a decrease of the signals of both the phospholipid precursors and the products of membrane degradation occurred concomitantly with TGI. This multi-analysis established, at least partly, the ICEU activity profile, in vitro and in vivo, providing additional data in favour of ICEU as a tubulin-interacting drug accumulating within the intestinal tract. This may provide a starting point for researches for future efficacious tubulin-interacting drugs for the treatment of colorectal cancers.

Carrier Cell-based Delivery of an Oncolytic Virus Circumvents Antiviral Immunity

Oncolytic viruses capable of tumor-selective replication and cytolysis have shown early promise as cancer therapeutics. However, the host immune system remains a significant obstacle to effective systemic administration of virus in a clinical setting. Here, we demonstrate the severe negative impact of the adaptive immune response on the systemic delivery of oncolytic vesicular stomatitis virus (VSV) in an immune-competent murine tumor model, an effect mediated primarily by the neutralization of injected virions by circulating antibodies. We show that this obstacle can be overcome by administering virus within carrier cells that conceal viral antigen during delivery. Infected cells were delivered to tumor beds and released virus to infect malignant cells while sparing normal tissues. Repeated administration of VSV in carrier cells to animals bearing metastatic tumors greatly improved therapeutic efficacy when compared with naked virion injection. Whole-body molecular imaging revealed that carrier cells derived from solid tumors accumulate primarily in the lungs following intravenous injection, whereas leukemic carriers disseminate extensively throughout the body. Furthermore, xenogeneic cells were equally effective at delivering virus as syngeneic cells. These findings emphasize the importance of establishing cell-based delivery platforms in order to maximize the efficacy of oncolytic therapeutics.

RNAPc2, a Novel Inhibitor of Tissue Factor/Factor VIIa Complex, Suppresses Lung Metastasis and Synergizes with 5-FU or Bevacizumab in Mouse Models of Colorectal Cancer.

Recombinant nematode anticoagulant protein c2 (rNAPc2) is a specific inhibitor of tissue factor (TF)/factor VIIa complex with novel anti-metastasis, anti-angiogenesis, and anti-thrombosis activities. rNAPc2 has been previously shown to inhibit both the primary growth and metastasis of murine B16 melanoma and Lewis lung carcinoma in mice. TF is highly expressed in human colorectal tumors and the level of TF expression positively correlates with the progression of malignancy. To explore the therapeutic potential of rNAPc2 during tumor growth and progression, we tested rNAPc2 efficacy in experimental colorectal cancer in mice. Both primary and metastatic colorectal tumor models were used in the current study and rNAPc2 was given to mice via daily intraperitoneal injections. Administration of rNAPc2 inhibited pulmonary metastasis in mice systemically disseminated with CT26 murine colon carcinoma cells in a dose-dependent fashion, as measured by either number of lung surface metastases or lung mass. While rNAPc2 treatment alone moderately reduced primary tumor growth, combining rNAPc2 with the cytotoxic agent 5-fluorouracil (5-FU) resulted in synergistic growth inhibition of HCT116 human colorectal tumor xenografts in nude mice. Likewise, rNAPc2 further reduced tumor growth in HCT116 human colorectal tumor xenograft-bearing mice receiving bevacizumab (humanized anti-vascular endothelial growth factor monoclonal antibody). The doses and dosing regimens of rNAPc2 used in these murine models of colorectal cancer were well tolerated by recipient mice without major complications of hemorrhage or any other adverse effects. In conclusion, the synergistic tumor inhibitory activity of rNAPc2 in pre-clinical colorectal cancer models suggests that rNAPc2 may be an effective anti-tumor agent in human colorectal cancer patients to potentiate chemo- or anti-angiogenic therapies.