Ex vivo evaluation of anti-EpCAM immunocytokine huKS-IL2 in ovarian cancer.
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.
Connor
Joseph P
JP
University of Wisconsin, Department of Obstetrics and Gynecology, Division of Gynecologic Oncology, Madison, USA. jpconnor@wisc.edu
Felder
Mildred
M
Hank
Jacquelyn
J
Harter
Josephine
J
Gan
Jacek
J
Gillies
Stephen D
SD
Sondel
Paul
P
D000911:Antibodies, Monoclonal / Q000737:chemistry; D015703:Antigens, CD / Q000737:chemistry; D000945:Antigens, Differentiation, T-Lymphocyte / Q000737:chemistry; D000951:Antigens, Neoplasm / Q000737:chemistry*; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000737:chemistry*; D045744:Cell Line, Tumor; D002857:Chromium / Q000737:chemistry; D016207:Cytokines / Q000737:chemistry*; D000071858:Epithelial Cell Adhesion Molecule; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D007376:Interleukin-2 / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism; D037181:Lectins, C-Type; D017493:Leukocyte Common Antigens / Q000737:chemistry; D007963:Leukocytes, Mononuclear / Q000737:chemistry / Q000378:metabolism; D010051:Ovarian Neoplasms / Q000737:chemistry* / Q000276:immunology* / Q000378:metabolism; D010537:Peritoneum / Q000166:cytology / Q000473:pathology; D013997:Time Factors; D000099192:CD69 Antigens
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D000951:Antigens, Neoplasm; D015815:Cell Adhesion Molecules; D002857:Chromium; D016207:Cytokines; D000071858:Epithelial Cell Adhesion Molecule; D007376:Interleukin-2; D037181:Lectins, C-Type; D017493:Leukocyte Common Antigens; D000099192:CD69 Antigens