Combination of a monoclonal anti‐phosphatidylserine antibody with gemcitabine strongly inhibits the growth and metastasis of orthotopic pancreatic tumors in mice

Abstract

Pancreatic cancer continues to have a dismal prognosis and novel therapy is needed. In this study, we evaluate a promising new target for therapy, phosphatidylserine (PS). PS is an anionic phospholipid located normally on the inner leaflet of the plasma membrane in mammalian cells. In the tumor microenvironment, PS becomes externalized on vascular endothelium. The monoclonal antibody 3G4 binds PS and promotes an inflammatory response against tumor blood vessels, resulting in reduction of tumor growth. Mice with orthotopic pancreatic tumors were treated with 3G4, gemcitabine or a combination of both drugs. Tumor burden including pancreas weight and metastatic lesions (liver, lymph node and peritoneal) were reduced 3-to 5-fold by the combination therapy as compared with 1.5-to 2-fold with 3G4 and gemcitabine alone, respectively. Treatment of tumor-bearing animals with the combination therapy increased macrophage infiltration into the tumor mass 10-fold and reduced microvessel density in the tumor by 2.5-fold compared with tumors from untreated animals. Gemcitabine alone and 3G4 alone were less effective than the combination of the 2 agents together. The additive therapeutic effect of both agents appears to be because chemotherapy increases PS exposure on tumor vascular endothelium and amplifies the target for attack by 3G4. In conclusion, 3G4 enhanced the anti-tumor and anti-metastatic activity of gemcitabine without contributing to toxicity. ' 2005 Wiley-Liss, Inc.

The use of the orthotopic model to validate antivascular therapies for cancer

“…It has been shown that 2aG4 treatment not only has an antivascular action when combined with irradiation in this model, but also enhances the immunogenicity of the tumour leading to immunologic control of residual tumour cells. Moreover, antivascular effects and antitumour effects were accompanied by the recruitment of host immune cells in tumour vasculature and the subsequent infiltration into the tumour interstitium, as shown also by other studies (Beck, 2006;Tozer, 2008).…”

“…It has been shown that 2aG4 treatment not only has an antivascular action when combined with irradiation in this model, but also enhances the immunogenicity of the tumour leading to immunologic control of residual tumour cells. Moreover, antivascular effects and antitumour effects were accompanied by the recruitment of host immune cells in tumour vasculature and the subsequent infiltration into the tumour interstitium, as shown also by other studies (Beck, 2006;Tozer, 2008).To this regard, we evaluated a successful combination strategy in neuroblastoma model using liposomal formulations of DXR targeted against both tumour cells, via anti-GD 2 monoclonal antibodies, and against the tumour vasculature, via the NGR peptide (Pastorino, 2006). The anti-GD 2 -targeted liposomes resulted in direct cell kill, including cytotoxicity against cells that were at the tumour periphery and were independent of the tumour vasculature, whereas NGR peptide-targeted liposomal doxorubicin bind to and killed angiogenic blood vessels and, indirectly, the tumour cells that these vessels supported, mainly in the tumour core.…”

“…The effect of the combination of gemcitabine with 3G4 was significantly better than either therapy alone, suggesting that gemcitabine enhances 3G4 function, or viceversa (Beck, 2006). Similarly, Huang et al, reported that 3G4 enhanced the inhibitory effect of docetaxel on the growth of orthotopically-implanted breast tumour model, pointing out the conditions in the tumour microenvironment play an important role in docetaxel-induced exposure of anionic phospholipids on tumour vascular endothelium .…”

“…Effect of the combination therapy was investigated using the monoclonal antibody 3G4, direct to PS, and chemotherapeutic agents, such as gemcitabine and docetaxel, in pancreatic and breast orthotopic models, respectively (Beck, 2006;.…”

Monitoring Response to Anticancer Therapy by Targeting Microbubbles to Tumor Vasculature

“…The murine (Pan02) and human (MiaPaca-2) pancreatic adenocarcinoma cell lines were obtained from the Developmental Therapeutics Program (Division of Cancer Treatment and Diagnosis, National Cancer Institute, Frederick, MD) and the American Type Culture Collection (Manassas, VA), respectively, and maintained as described (21). The mAbs MJ7/18 (22), AFRC Mac 48 (Mac 48, a rat IgG2a specific for phytochrome; European Collection of Animal Cell Cultures, Salisbury, United Kingdom), 9G10 (23) C44, 2C3, and Gv39M (20, 23 -25) were purified from hybridoma supernatant by protein A or G affinity chromatography.…”