Ex vivo evaluation of anti-EpCAM immunocytokine huKS-IL2 in ovarian cancer

J Immunother. May-Jun 2004;27(3):211-9. doi: 10.1097/00002371-200405000-00005.

Abstract

Despite encouraging responses to treatment, 70% to 80% of women with ovarian cancer will recur due to subclinical residual disease. One experimental agent that merits testing in this setting is the immunocytokine huKS-IL2. Immunocytokines are fusion proteins consisting of a humanized monoclonal antibody linked to IL-2 (or other cytokines). The humanized monoclonal antibody (mAb) huKS, which recognizes the epithelial cell adhesion molecule (EpCAM), has been used to construct the immunocytokine huKS-IL2. To determine the potential therapeutic use of huKS-IL2 in ovarian cancer, the authors evaluated the expression of EpCAM in these cancers and investigated the effects of huKS-IL2 on peritoneal white blood cells and peripheral blood mononuclear cells from women with ovarian cancer. EpCAM expression was determined by immunohistochemistry using both huKS-IL2 and the parent KS1/4 antibody. Ascites fluid was collected and the cellular fraction cultured with or without huKS-IL2 to evaluate the cellular content and potential anti-tumor effects of the peritoneal effector cells (PECs). Peritoneal cells were incubated with FITC-conjugated KS antibody to determine the relative amount of EpCAM-positive cells. Nonadherent cells were analyzed by flow cytometry for hematopoietic origin with CD45 mAb and for CD69 expression as an indication of immune cell activation. EpCAM-positive NIH:OVCAR-3 cells were radiolabeled as targets in a chromium release assay with either PECs or PBMCs as effector cells in the presence or absence of 0.25 mcg/mL huKS-IL2. Differences between treatments were determined by t test. Thirty-two of thirty-three (97%) ovarian cancers were found to express EpCAM via immunohistochemistry. Eleven cases were stained using both KS1/4 and huKS-IL2, and identical patterns of staining were seen. All ascites samples tested had EpCAM-positive cells by flow cytometry. The mean fluorescence intensity of CD69 expression on peritoneal WBCs was increased from 20.7 to 43.9 as a result of culturing with huKS-IL2, indicating effector cell activation. In chromium release assays, KS-IL2 facilitated cell lysis of NIH:OVCAR-3 by PBMCs from both healthy controls and patients with ovarian cancer. PECs from all cases tested showed significant cell lysis induced by huKS-IL2 compared with untreated control cultures. Based on these findings, huKS-IL2 warrants further investigation as a potential immunotherapy for patients with epithelial ovarian cancer, preferably in a minimal disease setting as seen after complete cytoreductive surgery, after a complete clinical response to primary therapy, or when elevated CA-125 levels predict recurrent disease prior to clinical relapse.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Antibodies, Monoclonal / chemistry
  • Antigens, CD / chemistry
  • Antigens, Differentiation, T-Lymphocyte / chemistry
  • Antigens, Neoplasm / chemistry*
  • Cell Adhesion
  • Cell Adhesion Molecules / chemistry*
  • Cell Line, Tumor
  • Chromium / chemistry
  • Cytokines / chemistry*
  • Epithelial Cell Adhesion Molecule
  • Female
  • Flow Cytometry
  • Humans
  • Immunohistochemistry
  • In Vitro Techniques
  • Interleukin-2 / chemistry*
  • Interleukin-2 / immunology
  • Interleukin-2 / metabolism
  • Lectins, C-Type
  • Leukocyte Common Antigens / chemistry
  • Leukocytes, Mononuclear / chemistry
  • Leukocytes, Mononuclear / metabolism
  • Ovarian Neoplasms / chemistry*
  • Ovarian Neoplasms / immunology*
  • Ovarian Neoplasms / metabolism
  • Peritoneum / cytology
  • Peritoneum / pathology
  • Time Factors

Substances

  • Antibodies, Monoclonal
  • Antigens, CD
  • Antigens, Differentiation, T-Lymphocyte
  • Antigens, Neoplasm
  • CD69 antigen
  • Cell Adhesion Molecules
  • Cytokines
  • Epithelial Cell Adhesion Molecule
  • Interleukin-2
  • Lectins, C-Type
  • Chromium
  • Leukocyte Common Antigens