Ex vivo evaluation of anti-EpCAM immunocytokine huKS-IL2 in ovarian cancer.
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| 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.
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| Authors | Joseph P Connor, Mildred Felder, Jacquelyn Hank, Josephine Harter, Jacek Gan, Stephen D Gillies, Paul Sondel |
| Journal | Journal of immunotherapy (Hagerstown, Md. : 1997) (J Immunother) 2004 May-Jun Vol. 27 Issue 3 Pg. 211-9 ISSN: 1524-9557 [Print] United States |
| PMID | 15076138 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.) |
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