Activation of the nuclear oncogene, p53, may be the most frequent alteration found in human tumors. High-level overexpression of p53 protein, due to point mutation in the gene, has been found in 27% of breast cancers. Furthermore, tumors overexpressing p53 generally present at more advanced clinical stages. A broadly reactive, high titer autoantibody against p53 is found in a proportion of patients with breast cancer expressing mutant p53 proteins. These mutant proteins all bind a 70kd member of the heat shock protein family (hsp70). From in vitro experiments, hsp70 binding p53 mutants appear more potent in cell transformation. To investigate the possibility that p53 alterations lead to clinically apparent differences in tumor behavior, it will be determined whether breast cancers that contain widespread overexpression of p53 pursue a more aggressive clinical course than their counterparts initiated by mechanisms other than p53 mutation. Furthermore, whether p53 mutants can be clinically classified by their ability to bind hsp70 and whether the potency of these mutants is altered by retention of a wild-type p53 gene in tumor tissue will be studied. Experimentally, the potency of the two classes of p53 mutants (hsp-binding and non-binding) will be compared in mice containing p53 transgenes. To investigate the potential utility of monitoring p53 autoantibodies, it will be determined if all mammary tumors containing hsp70 binding p53 proteins, regardless of stage, elicit an autoantibody. Additionally, the time course of antibody disappearance and reappearance in patients presenting with primary breast cancer will be measured. Immunoreactive determinates of the p53 protein are found in the serum of some breast cancer patients. Experiments to determine if hsp70 binding alters the intracellular fate of p53 and leads to secretion of the protein will be performed on fibroblasts and mammary epithelium. A model of p53 immunity will be constructed using cells transformed by different classes of p53 mutants to induce tumors in syngeneic rats. The ability of different cells to induce transplantation immunity will be specifically investigated. Finally, the existence of cytolytic T cells that recognize p53 epitopes will be determined in the breast cancer patients using syngeneic targets (immortalized B cells) acutely infected with vaccinia virus containing truncated p53 coding sequences. p53 alterations may provide important prognostic information of relevance to surgical oncology. In addition, monitoring autoantibodies will be a sensitive and specific way to determine tumor recurrence in antibody positive patients and the existence of a cellular immune response to p53 may be found to greatly influence the course of the disease.
