Abstract P1-03-09: Combination of nab-Paclitaxel and Bevacizumab Inhibited Tumor Growth and Metastasis of New Inflammatory Breast Cancer Models

Background: Inflammatory breast cancer (IBC) is a highly lethal form of breast cancer which is characterized by skin redness, irritation, swelling, pain, as well as extensive lymph nodes (LN) and hematogenous metastasis. Animal models of IBC are highly desirable for studying its pathology and for designing effective therapies. In this study, we established two new luciferase-and fluorescently-labeled IBC models and tested the efficacy of the novel drug combination nab-paclitaxel and bevacizumab. Methods: Inflammatory SUM149 breast cancer cells were stably transfected with Red Fluorescent Protein (RFP) and Renilla luciferase to establish SUM149-RR, or infected with lentivirus encoding Green Fluorescent Protein (GFP) and Firefly luciferase to establish SUM149- GL. The new cell lines were characterized both in vitro and in vivo. Immunodeficient mice bearing SUM149-RR tumors of 150mm3 in size were treated with saline (control), bevacizumab (4 mg/kg, i.p., twice a week, for 10 weeks), nab-paclitaxel (10 mg/kg, i.v., qdx5), or the combination. Metastasis was analyzed by measuring luciferase activity in the lymph nodes (LN) and lungs.

Results: Luciferase measurements and in vivo imaging showed that both SUM149-RR and-GL clones were highly metastatic to LN, lungs, liver, brain, and spleen. SUM149-RR tumors in control mice displayed ulcerations, edema and redness similar to the clinical disease, while tumors in mice treated with bevacizumab or combination therapy showed no signs of inflammation. Bevacizumab alone decreased tumor growth at later but not early stages of tumor growth, whereas nab-paclitaxel alone inhibited tumor growth by 73%. Combination therapy increased inhibition to 96%, and resulted in 22% (2/9) complete responses. Histologically, tumors from bevacizumab treated groups were more morphologically intact with reduced vascular abnormalities than tumors from control or nab-paclitaxel treated mice. LN and lung metastasis was significantly reduced in all treated groups as compared with control.

Conclusions: The SUM149-RR and SUM149-GL lines are new double-tagged models of human IBC that allow organ visualization and accurate quantification of metastasis. These models can be used to study the biology and treatment of IBC. Combination of nab-paclitaxel with bevacizumab was highly effective against SUM149-RR, suggesting the potential usefulness of this regimen for treatment of IBC patients.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P1-03-09.

Abstract P1-03-11: Combination of nab-Paclitaxel and Bevacizumab Inhibited Tumor Growth and Metastasis of a New Triple Negative Breast Cancer Model

Background: Triple-negative breast cancers are highly aggressive and resistant to chemotherapy. In this study, we established a new model of triple-negative breast cancer and used it to test the novel combination of nab-paclitaxel with anti-VEGF antibody bevacizumab, which has been effective in treating other metastatic cancer types. Methods: The triple-negative HCC1806 beast cancer cells were stably transfected with dual reporters Red Fluorescent Protein (RFP) and Renilla luciferase to establish the new HCC1806-RR model. Immunodeficient mice bearing orthotopic HCC1806-RR tumors of 150mm3 in size were treated with saline (control), bevacizumab (4 mg/kg. i.p., twice a week, for 10 weeks), nab-paclitaxel (10 mg/kg, i.v., qdx5), or with combination of nab-paclitaxel and bevacizumab. Metastasis was analyzed by measuring luciferase activity in the lymph nodes (LN) and lungs. Results: The HCC1806-RR cells had identical morphology, proliferation rates and sensitivity to nab-paclitaxel as the parental HCC1806 cell line. HCC1806-RR tumors primarily metastasized to LN, with lung being a secondary metastatic site. Combination therapy of nab-paclitaxel and bevacizumab inhibited tumor growth by 100%, as compared to 0% for bevacizumab (P < 0.001) and 90% for nab-paclitaxel (P = 0.024). Importantly, only combination therapy reduced incidence of LN and lung metastases by 50% (P = 0.007) and 87% (P = 0.001). Overall, 50% of the mice in the combination therapy group (n = 10) had complete regressions of both primary tumors and metastases at both regional and distant sites. Conclusions : The HCC1806-RR is a new triple-negative breast model with dual reporters to allow for quantitative assessment of metastatic spread. This model can be used to study the biology and treatment of triple-negative breast cancer. Combination of nab-paclitaxel with bevacizumab was highly effective against HCC 1806-RR tumors, suggesting that this regimen could provide clinical benefits to patients with triple-negative breast cancers.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P1-03-11.

A replication defective recombinant Ad5 vaccine expressing Ebola virus GP is safe and immunogenic in healthy adults

Ebola virus causes irregular outbreaks of severe hemorrhagic fever in equatorial Africa. Case mortality remains high; there is no effective treatment and outbreaks are sporadic and unpredictable. Studies of Ebola virus vaccine platforms in non-human primates have established that the induction of protective immunity is possible and safety and human immunogenicity has been demonstrated in a previous Phase I clinical trial of a 1st generation Ebola DNA vaccine. We now report the safety and immunogenicity of a recombinant adenovirus serotype 5 (rAd5) vaccine encoding the envelope glycoprotein (GP) from the Zaire and Sudan Ebola virus species, in a randomized, placebo-controlled, double-blinded, dose escalation, Phase I human study. Thirty-one healthy adults received vaccine at 2×10(9) (n=12), or 2×10(10) (n=11) viral particles or placebo (n=8) as an intramuscular injection. Antibody responses were assessed by ELISA and neutralizing assays; and T cell responses were assessed by ELISpot and intracellular cytokine staining assays. This recombinant Ebola virus vaccine was safe and subjects developed antigen specific humoral and cellular immune responses.

Albumin-Binding and Angiogenic Domains of SPARC Located at Its C-Terminus

Background: SPARC (Secreted Protein Acidic and Rich in Cysteine) is an albumin-binding glycoprotein overexpressed in breast cancer and is associated with poor prognosis and shorter overall survival. We have previously shown that SPARC expression appeared to correlate with response to nanoparticle albumin-bound (nab) paclitaxel (Abraxane) in head-and-neck and pancreatic-cancer patients. To further define the role of SPARC, recombinant-human SPARC (rhSPARC) was characterized to identify its albumin-binding and angiogenic domain.Materials and methods: The albumin-binding site on SPARC was defined by testing the binding of Alexa 488-labeled BSA to immobilized rhSPARC in a solid-phase-binding assay and in a competitive-binding assay in presence of increasing concentration of various SPARC-derived peptides. The angiogenic activity of rhSPARC was evaluated using a HUVEC tube-formation assay.Results: The SPARC albumin-binding assay revealed a pattern of saturable and specific binding with an estimated Kd of 700 µM very near the known plasma concentration of albumin (600 µM). Competitive binding with Cathepsin K-digested SPARC and SPARC-derived peptides defined the albumin-binding domain to be amino acids 209-223 in the C-terminal region. In the HUVEC tube-formation assay, rhSPARC was pro-angiogenic at 10 µg/ml and anti-angiogenic at 100 µg/ml. The angiogenic domain of SPARC was located to the C-terminal of SPARC.Discussion: The albumin-binding domain of SPARC was located to residues aa209-223, supporting its role as a target for nab-technology-based drug delivery. We confirmed that SPARC can promote angiogenesis at physiological concentrations, contributing to the role of SPARC in a more aggressive tumor phenotype. The angiogenic domain of SPARC is located within a 54-aa sequence of its C-terminus. SPARC could be a potential therapeutic target and a biomarker for predicting response to nab-paclitaxel.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2144.

Combination Regimens of nab-Rapamycin (ABI-009) Effective Against MDA-MB-231 Breast-Tumor Xenografts

Background: The mammalian target of Rapamycin (mTOR) is a key intracellular kinase integrating cell proliferation and survival and is an attractive target for cancer therapy. Nab-rapamycin (ABI-009) was developed using proprietary nab-technology and showed dose-linear pharmacokinetics, safety up to 90 mg/kg and effective antitumor activity at 40 mg/kg in the human-tumor-xenograft panel. The goal of this study was to test the effectiveness of different combination regimens for ABI-009 against MDA-MB-231 breast-tumor xenografts.Materials and methods: Subcutaneous human-breast (MDA-MB-231) tumors were grown in athymic nude mice and treated intravenously (IV) with ABI-009 alone at 40 mg/kg (3xwkly/4wks) and in combination with Erlotinib (50 and 100 mg/kg/day/4wks, IP), Cetuximab (20 and 40 mg/kg, 3xwkly/4wks, IP), Doxorubicin (2 and 5 mg/kg, wkly/10 wks, IV), Oxaliplatin (5 and 10 mg/kg wkly/4 wks, IV), SAHA (50 mg/kg, qdx7 or qdx14, IP), and Perifosine (30 and 60 mg/kg, 3xwkly/4wks, PO). The animal weights and tumor measurements were recorded three times weekly and adverse observations recorded.Results: ABI-009 was highly effective as a single agent against MDA-MB-231 breast tumor xenografts with 75% tumor-growth inhibition (TGI). Combination with Erlotinib resulted in TGI of 85% and 95% (50 and 100 mg/kg, respectively), 83% and 87% for Cetuximab (20 and 40 mg/kg, respectively), 83% and 90% for Doxorubicin (2.5 and 5 mg/kg, respectively), 82% and 85% for Oxaliplatin (5 and 10 mg/kg, respectively), 82% and 90% for SAHA (7 and 14 day treatment, respectively), and 92% and 96% for Perifosine (30 and 60 mg/kg, respectively). Notably, Erlotinib and Perifosine were found to synergize with ABI-009 resulting in maximum TGI and tumor growth delay.Discussion: ABI-009 (nab-rapamycin) alone was highly effective against MDA-MB-231 human-breast-tumor xenografts. Antitumor activity of ABI-009 was significantly increased in combination with kinase inhibitors, Erlotinib (EGFR-kinase inhibitor) and Perifosine (AKT inhibitor). Antitumor activity of ABI-009 was also significantly increased in combination with Doxorubicin – a topoisomerase inhibitor, and SAHA – an HDAC inhibitor, but not in combination with Oxaliplatin – a DNA crosslinker. In contrast, combination of ABI-009 with anti-EGFR monoclonal antibody, Cetuximab was not effective. The synergy of these combinations confirmed that rapamycin is active only on TORC1 and that suppression of TORC2 via AKT or PI3K pathways is a means of increasing activity of mTOR inhibitors with potential relevance to breast cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6106.