Abstract 4410: Neutralizing Endosialin antibody, MORAb-004, enhances efficacy of TAXOTERE in a metastatic melanoma model

Endosialin/Tumor Endothelial Marker-1 (TEM1) is a cell surface glycoprotein that is expressed on cells involved in the development of tumor vasculature, primarily pericytes and stromal fibroblasts. Studies have found it to play a key role in tumor growth and neo-vessel formation in numerous cancer types. We are currently evaluating the safety and therapeutic potential of MORAb-004, a humanized monoclonal IgG targeting endosialin/TEM-1, in clinical trials. Because MORAb-004 only recognizes human antigen and has no cross-reactivity with rodent endosialin/TEM-1, we generated a human endosialin/TEM-1 knock-in mouse in order to assess its activity in vivo. Previously, in this transgenic model, we found that MORAb-004 significantly inhibited subcutaneous B16-F10 melanoma progression by ∼70% when administered intravenously for 5 consecutive days. Moreover, using the Lewis Lung Carcinoma model of metastatic disease our results showed that MORAb-004 had a significant inhibitory effect on the number of lung metastases. For these studies, supporting clinical trials for using MORAb-004 in combination with standard of care chemotherapeutics, we developed a B16-F10 melanoma lung colonization model. In this model, the human endosialin/TEM-1 knock-in mice were implanted intravenously with B16F10 cells adapted for in vivo lung colonization. These mice were treated with Docetaxel, MORAb-004, or the combination of the two agents, respectively. A group of the tumor-bearing mice receiving PBS served as control. At the end of the study, the lungs of each mouse were harvested. A ratio of the area of tumor nodules versus total lung surface area is calculated as tumor burden. MORAb-004, at 50 mg/kg three times weekly for a total of 7 i.v. injections reduced tumor burden by 45%. Treatment of Docetaxel, at 3mg/kg twice weekly for a total of 5 i.p. injections, reduced less than 20% of tumor burden in the lungs. When MORAb004 was added to Docetaxel treatment, a significant enhancement of efficacy was observed. The reduction of tumor nodules in the lungs was increased to approximately 70%. A similar trend is seen in combination therapy where MORAb-004 was added to gemcitabine regimen. Our results demonstrate the ability of MORAb-004 to inhibit tumor growth in a murine model. Moreover, when added to the chemotherapeutic regimen, it significantly enhances the therapeutic effect of traditional chemotherapy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4410. doi:1538-7445.AM2012-4410

Curcumin-induced HDAC inhibition and attenuation of medulloblastoma growth in vitro and in vivo

Background

Medulloblastoma is the most common brain tumor in children, and its prognosis is worse than for many other common pediatric cancers. Survivors undergoing treatment suffer from serious therapy-related side effects. Thus, it is imperative to identify safer, effective treatments for medulloblastoma. In this study we evaluated the anti-cancer potential of curcumin in medulloblastoma by testing its ability to induce apoptosis and inhibit tumor growth in vitro and in vivo using established medulloblastoma models.

Methods

Using cultured medulloblastoma cells, tumor xenografts, and the Smo/Smo transgenic medulloblastoma mouse model, the antitumor effects of curcumin were tested in vitro and in vivo.

Results

Curcumin induced apoptosis and cell cycle arrest at the G2/M phase in medulloblastoma cells. These effects were accompanied by reduced histone deacetylase (HDAC) 4 expression and activity and increased tubulin acetylation, ultimately leading to mitotic catastrophe. In in vivo medulloblastoma xenografts, curcumin reduced tumor growth and significantly increased survival in the Smo/Smo transgenic medulloblastoma mouse model.

Conclusions

The in vitro and in vivo data suggest that curcumin has the potential to be developed as a therapeutic agent for medulloblastoma.

Abstract 4573: Inhibition of tumor growth by human IgM-isotype monoclonal antibody to ganglioside GD2

Monoclonal antibody, MORAb-028, a human IgM derived from patients with melanoma, specifically binds to tumor cell surface ganglioside-GD2 with high specificity, and kills GD2-expressing target cells via complement-mediated cytotoxicity (CDC). This CDC-mediated anti-tumor activity of MORAb-028 has been confirmed in vitro using various GD2-expressing tumor cells in presence of rat sera.

In the present study, intraperitoneal (i.p) and intratumoral (i.t.) treatment models in nude rats were developed to investigate in vivo anti-tumor activity of MORAb-028. These compartmental models provide an in vivo system to monitor IgM anti-tumor activity that has not been possible in previous studies due to the rodent poly-Ig-Receptor (PIgR) that is able to sequester systemically administered hIgM in the liver thereby lowering serum IgM steady-state levels that in turn lowers distribution of IgM to targeted tumors.

In the present study, murine EL4-luc2 cells that express high levels of GD2 were engineered to express a luciferase-reporter-gene enabling in vivo bioluminescent detection for monitoring tumor status. These cells were used in two different models to test the ability of MORAb-028 to impact tumor growth.

An i.p. model was developed whereby tumor cells were injected directly into the peritoneal cavity of nude rats followed immediately by a single i.p. dose of MORAb-028 at 3mg/kg, a dose that has showed activity in vitro. Tumor progression was monitored by bioluminescence using IVIS living imaging system. On day 24 post treatment, a significant reduction in tumor progression was observed in the MORAb-028-treated animals in comparison to the control. Only minimal tumor growth (∼3 to 5 mm3) was observed in MORAb-028-treated animals in contrast to control animals, in which tumor occupied the entire peritoneal cavity.

In a second model EL-4-luc cells were implanted subcutaneously and antibody was directly administered to palpable tumors. Here, a single intratumoral injection of MORAb-028 was administered into established (300-400 mm3) tumors. Results showed that MORAb-028 treatment significantly inhibited tumor growth and eradicated nearly the entire tumor in ∼30% of the animals. Six days post treatment the tumor volume in MORAb-028-treated animals was ∼250 mm3, whereas the tumor volume was >1500mm3 in control animals. Animals with eradicated tumors showed no sign of recurrence at day 30 when the study was terminated.

These data indicate that MORAb-028 is a potent agent to treat GD2-positive tumors in rat models. These results also suggest that this antibody may be useful in clinical applications for the treatment of GD2-positive human cancers.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4573. doi:10.1158/1538-7445.AM2011-4573

Selective inhibition of eosinophil influx into the lung by small molecule CC chemokine receptor 3 antagonists in mouse models of allergic inflammation

CC chemokine receptor (CCR) 3 is a chemokine receptor implicated in recruiting cells, particularly eosinophils (EPhi), to the lung in episodes of allergic asthma. To investigate the efficacy of selective, small molecule antagonists of CCR3, we developed a murine model of EPhi recruitment to the lung. Murine eotaxin was delivered intranasally to mice that had previously received i.p. injections of ovalbumin (OVA), and the effects were monitored by bronchoalveolar lavage. A selective eosinophilic influx was produced in animals receiving eotaxin but not saline. Furthermore, the number of EPhi was concentration- and time-dependent. Although anti-CCR3 antibody reduced the number of EPhi, the effect of eotaxin in OVA-sensitized mice was not a direct chemotactic stimulus because mast cell deficiency (in WBB6F1-Kitw/Kitw-v mice) significantly reduced the response. Two representative small molecule CCR3 antagonists from our program were characterized as being active at mouse CCR3. They were administered p.o. to wild-type mice and found to reduce eotaxin-elicited EPhi selectively in a dose-dependent manner. Pump infusion of one of the inhibitors to achieve steady-state levels showed that efficacy was not achieved at plasma concentrations equivalent to the in vitro chemotaxis IC90 but only at much higher concentrations. To extend the results from our recruitment model, we tested one of the inhibitors in an allergenic model of airway inflammation, generated by adoptive transfer of OVA-sensitive murine T helper 2 cells and aerosolized OVA challenge of recipient mice, and found that it inhibited EPhi recruitment. We conclude that small molecule CCR3 antagonists reduce pulmonary eosinophilic inflammation elicited by chemokine or allergenic challenge.

The characterization of potent novel warfarin analogs

Racemic sodium warfarin, Coumadin, is widely used in the prevention of thromboembolic disease. The present study was undertaken to characterize three novel classes of warfarin analogs, and to compare them with the warfarin enantiomers. All three classes of compounds inhibit vitamin K epoxide reductase, the enzyme inhibited by racemic warfarin. The alcohol and the ester analogs have reduced protein binding compared with R-(+)-warfarin. The ester and the fluoro-derivatives have similar in vivo anticoagulant activity in the rat to that of S-(-)-warfarin. Thus, it is possible to synthesize novel warfarin analogs that differ from racemic warfarin or its enantiomers in certain selected properties.