Antibody-dependent cytotoxicity mediated by chimeric monoclonal antibody Nd2 and experimental immunotherapy for pancreatic cancer

Early administration of amatuximab, a chimeric high-affinity anti-mesothelin monoclonal antibody, suppresses liver metastasis of mesothelin-expressing pancreatic cancer cells and enhances gemcitabine sensitivity in a xenograft mouse model

Amatuximab is a promising therapeutic antibody targeting mesothelin, a 40-kDa glycoprotein that is highly expressed in pancreatic cancer. We investigated the effectiveness of early amatuximab treatment, imitating an adjuvant chemotherapy setting, and combination therapy with amatuximab and gemcitabine in liver metastasis of pancreatic cancer. Liver metastasis mouse models were established in 8-week-old male BALB/c nu/nu mice using the hemisplenic injection method. Tridaily amatuximab monotherapy or combination with gemcitabine was administered to the liver metastasis mouse model before metastatic lesions had formed huge masses. Gaussia luciferase-transfected AsPC-1 was used as a mesothelin-overexpressing pancreatic cancer cell line. The amount of liver metastases and the serum luciferase activity were significantly lower in the treatment groups than those in the control IgG group. Notably, the anti-tumor activity of gemcitabine was synergically enhanced by combination therapy with amatuximab. Furthermore, western blotting revealed that the high expression of phosphorylated c-Met and AKT in liver metastatic lesions treated with gemcitabine monotherapy was canceled by its combination with amatuximab. This result indicated that the observed synergic therapeutic effect may have occurred as a result of the inhibitory effect of amatuximab on the phosphorylation of c-Met and AKT, which were promoted by exposure to GEM. In conclusion, our study revealed that early administration of amatuximab alone or in combination with GEM significantly suppressed the liver metastases of mesothelin-expressing pancreatic cancer cells. A phase II clinical trial of amatuximab as part of an adjuvant chemotherapy regimen for resected pancreatic cancer is expected.

Targeted radionuclide therapies for pancreatic cancer

Pancreatic malignancies, the fourth leading cause of cancer deaths, have an aggressive behavior with poor prognosis, resulting in a 5-year survival rate of only 4%. It is typically a silent malignancy until patients develop metastatic disease. Targeted radionuclide therapies of cancer such as radiolabeled peptides, which bind to the receptors overexpressed by cancer cells and radiolabeled antibodies to tumor-specific antigens provide a viable alternative to chemotherapy and external beam radiation of metastatic cancers. Multiple clinical trials of targeted radionuclide therapy of pancreatic cancer have been performed in the last decade and demonstrated safety and potential efficacy of radionuclide therapy for treatment of this formidable disease. Although a lot of progress has been made in treatment of pancreatic neuroendocrine tumors with radiolabeled (90)Y and (177)Lu somatostatin peptide analogs, pancreatic adenocarcinomas remain a major challenge. Novel approaches such as peptides and antibodies radiolabeled with alpha emitters, pre-targeting, bispecific antibodies and biological therapy based on the radioactive tumorlytic bacteria might offer a potential breakthrough in treatment of pancreatic adenocarcinomas.

Development of a cytokine-modified allogeneic whole cell pancreatic cancer vaccine

Management of patients with pancreatic cancer is a multidisciplinary approach that presents enormous challenges to the clinician. Overall 5-year survival for all patients remains <3%. Symptoms of early pancreas cancer are nonspecific. As such, only a fraction of patients are candidates for surgery. While surgical resection provides the only curative option, most patients will develop tumor recurrence and die of their disease. To date, the clinical benefits of chemotherapy and radiation therapy have been important but have led to modest improvements. Tumor vaccines have the potential to specifically target the needle of pancreas cancer cells amidst the haystack of normal tissue. The discovery of pancreas tumor-specific antigens and the subsequent ability to harness this technology has become an area of intense interest for tumor immunologists and clinicians alike. Without knowledge of specific antigen targets, the whole tumor cell represents the best source of immunizing antigens. This chapter will focus on the development of whole tumor cell vaccine strategies for pancreas cancer.

Antitumor effect of trastuzumab for pancreatic cancer with high HER-2 expression and enhancement of effect by combined therapy with gemcitabine

PURPOSE

The purpose of the present study was to evaluate whether trastuzumab has antitumor effect against pancreatic cancer and whether this effect is concordant with levels of HER-2, which is reportedly overexpressed in pancreatic cancer. We also investigated whether the effect is potentiated in combined therapy with gemcitabine.

EXPERIMENTAL DESIGN

Using immunohistochemistry and FACScan, we analyzed HER-2 expression in 16 pancreatic cancer cell lines. The in vitro antiproliferative effect of trastuzumab, alone and in combination with gemcitabine, was examined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The in vitro antibody-dependent cell-mediated cytotoxicity of trastuzumab was investigated by (51)Cr release assay. The in vivo antitumor effect of trastuzumab, alone and in combination with gemcitabine, was evaluated in nude mouse xenograft growth. The survival benefit was evaluated in a Capan-1 orthotopic implanted nude mouse model.

RESULTS

HER-2 expression of 2+ or more was observed in 10 and of 3+ in 2 of the 16 cell lines. No in vitro growth-inhibitory effect of trastuzumab was found in any cell line, but trastuzumab induced antibody-dependent cell-mediated cytotoxicity in proportion to HER-2 expression level. Trastuzumab inhibited tumor growth in Capan-1 (HER-2: 3+) xenografts and prolonged survival in the orthotopic model. These effects were increased by combined therapy with gemcitabine. In contrast, trastuzumab exhibited no antitumor effect against PANC-1 (HER-2: 1+) or SW1990 (HER-2: 2+) xenografts.

CONCLUSIONS

The antitumor effect of trastuzumab in pancreatic cancer with high HER-2 expression was shown in vitro and in vivo. Clinical application of trastuzumab is expected in pancreatic cancer with 3+ HER-2 expression.

Cytotoxic activity of novel human monoclonal antibody MT201 against primary ovarian tumor cells

PURPOSE

The epithelial cell adhesion molecule (Ep-CAM) is a clinically validated target for antibody-based therapy of cancer. The aim of this work was to evaluate the specific cytotoxic activity of a novel fully human Ep-CAM-specific IgG1 antibody, called MT201, against primary ovarian tumor cells and an ovarian tumor cell line.

METHODS

The anti-tumor efficacy of MT201 was examined both in coculture of the ovarian cancer cell line OvCAR-3 and peripheral blood mononuclear cells (PBMCs) from healthy donors, and in primary metastatic tumor specimens freshly dissected from 21 patients with ovarian cancer using only the tumor-resident autologous effector cells. The extent of tumor cell depletion was determined by flow cytometry using Ep-CAM/CA-125 double-labeling or Ep-CAM labeling, both combined with propidium iodide uptake as cell lysis marker.

RESULTS

MT201 at sub- micro g/ml concentrations effectively eliminated OvCar-3 cells in the presence of PBMC. In freshly dissected tumor specimen, endogenous autologous immune cells could lyse, in a MT201-dependent fashion, Ep-CAM-positive tumor cells in 17 out of 21 patients showing an ex vivo response rate of 81%. In certain samples, up to 80% lysis of Ep-CAM-positive tumor cells by MT201 were observed after 16-30 h of incubation.

CONCLUSIONS

These data indicate that MT201 can effectively redirect tumor-resident effector cells against Ep-CAM-positive ovarian cancer cells and may therefore offer an effective therapy for ovarian cancer.

Immunotherapy for pancreatic cancer: current concepts

Despite advances in chemotherapy and surgical technique, patients with pancreatic cancer often succumb to local recurrence or metastatic spread. The need for new therapeutic strategies for this disease coupled with a better understanding of basic immunology have led to the development of novel anti-tumor vaccines. This review focuses on the historical development of tumor vaccines emphasizing the identification of potential pancreatic tumor antigens. The role of both B-cell and T-cell responses in tumor rejection will be reviewed. Methods for antigen presentation, including peptides, recombinant viral and bacterial vectors, dendritic cells, and whole cell approaches will be discussed. The use of immune adjuvants and improved methods of vaccine delivery will also be explored. The full potential for the immunotherapy of pancreatic cancer awaits the results of early phase clinical trials. The development of pancreatic cancer vaccines represents a useful paradigm for the translation of basic research into the clinical arena.

Innovative treatments for pancreatic cancer

Pancreatic cancer is the fifth leading cause of cancer deaths in the United States with little or no impact from conventional treatment options. Significant advances in understanding basic immunology have renewed interest in using immunotherapy to treat pancreatic cancer. Cancer immunotherapy, including humanized MAbs, cytokines, and potent vaccine strategies, has been successful in animal models and is being evaluated in clinical trials. Gene therapy is also being explored using methods to inactivate oncogenes, replace defective tumor suppressor genes, confer enhanced chemosensitivity to tumor cells, and increase immunogenicity of tumor cells. Angiogenesis, an essential step in the growth and metastasis of pancreatic cancer, has been targeted by many antiangiogenic agents. Several clinical trials have been initiated to evaluate the role of these innovative strategies in patients with pancreatic cancer with increasingly sophisticated correlative studies to learn more about the mechanisms of tumor rejection with these agents. The rapid translation of basic science discoveries to clinical trials should result in the development of new effective treatments for patients with pancreatic cancer.