Effects of Irradiation on the Expression of Surface Antigens in Human Ovarian Cancer

Alessandro D Santin,John C Hiserodt,John Fruehauf,Philip J Disaia,Sergio Pecorelli,Gale A Granger

doi:10.1006/gyno.1996.0075

Abstract

Tumor cells from four established human ovarian carcinoma cell lines were analyzed for their expression of surface antigens including MHC Class I, Class II, ICAM-1, and the tumor-associated antigens CA 125 and Her2-neu before and after exposure to high doses of gamma irradiation. All four ovarian cell lines expressed variable levels of MHC Class I and Her2-neu. ICAM-1 antigens were expressed in only two cell lines and Class II and CA 125 surface antigens were absent in all the cell lines evaluated. Exposure to high doses of gamma irradiation (i.e., 5000 to 10,000 cGy) significantly and consistently increased the expression of all surface antigens present on the cells prior to irradiation. Importantly, the irradiation-induced upregulation was persistent and lasted until all the cells died. Irradiation was unable to induce neoexpression of antigens previously not expressed by the cells (i.e., MHC Class II or ICAM-1). These findings may partially explain the increased immunogenicity of tumor cells following irradiation and may suggest enhanced immune recognition in tumor tissue in patients receiving radiation therapy.

Highlights

Cell surface antigens are important for both recognition and destruction of tumor cells by the host immune system
Our studies show that high doses of gamma irradiation induce a significant and long-lasting upregulation of all surface antigens expressed on the ovarian carcinoma cell lines prior to irradiation
The importance of surface antigen expression and immune recognition has been underscored by studies on human tumor

Summary

Introduction

Cell surface antigens are important for both recognition and destruction of tumor cells by the host immune system. Levels of expression of these cell surface antigens are important in determining whether tumor cells are immunogenic [2, 3] and methods which upregulate their expression may facilitate more efficient host–tumor interactions. In this regard, several studies have described an increase in antigen expression after exposure of tumor cells to certain cytokines, IFN(s) and TNF-a [4, 5], and such tumor cell have been shown to be more immunogenic as determined by in vitro cytotoxicity assays [4,5,6]. Few studies have described the effects of high doses of irradiation on the expression of cell surface antigens on tumor cells, and no studies have been published evaluating such effects on human epithelial ovarian cancer cells

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Conclusion