Characterization of CD8+ cytotoxic T lymphocyte/tumor cell interactions reflecting recognition of an endogenously expressed murine wild-type p53 determinant.

Abstract

p53 mutations are frequently found in human cancers and are often associated with the overexpression of wild-type (WT) protein or peptide sequences, supporting the notion that WT p53 epitopes may serve as potential targets for tumor immunotherapy. We have developed a cytotoxic T lymphocyte (CTL)/p53 tumor-associated antigen (TAA) model, based on immune recognition of a WT p53 determinant. WT p53-peptide-specific, major histocompatibility complex (MHC) classI-restricted CTL were produced from immunocompetent C57BL/6 (H-2b) mice after immunization with a previously defined WT p53 peptide (p53(232-240)) Epitope-specific CTL were then employed to identify syngeneic tumor cell populations expressing that antigenic determinant. Two syngeneic tumor cell lines, MC38 colon carcinoma and MC57G fibrosarcoma, were demonstrated to express the endogenous WT p53(232-240) determinant naturally, as defined by CD8 + CTL recognition. Cold-target inhibition assays confirmed that CTL-mediated lysis was due to immune recognition of the p53(232-240) peptide epitope. The p53(232-240)-specific CTL line did not lyse syngeneic normal cells (i.e., mitogen-activated splenocytes) in the absence of exogenous peptide, suggesting that the WT-p53-specific CTL could distinguish between tumor cells expressing self-TAA and normal host cells. We have demonstrated, for the first time, that the adoptive transfer of WT-p53-specific CTL to mice with established pulmonary metastasis resulted in antitumor activity in vivo. The ability to generate MHC-class-I-restricted CD8- CTL lines specific for a non-mutated p53 determinant from normal, immunocompetent mice, which display antitumor activity both in vitro and in vivo (by adoptive transfer), may have implications for the immunotherapy of certain p53-expressing malignancies.