Tumors without a detectable p53 gene alteration by single-strand confor

Nuclear accumulation ofp53 protein Is associated with a poorer clinical outcome in breast cancer patients. Heat shock protein 70 (lssp7O) is a chaperone that binds to mutant p53 and consequently could regulate its accumulation or localization. The aims of this study were to determine if the prognostic significance ofp53 accumulation was dependent on the type ofantibody used for detection and whether hsp'7Owas associated with this accumulation. Node-negative breast tumors (n 169) were examined by Immunohistochemistry for nuclear p53, cytoplasmic or nuclear hsp7O,and forpS3 gene alteration by single-strand conformation polymorphism anal ysis. Frozen sections of pulverized breast tumors were stained with five p53 antibodIes (240, 1801, 421, BPS3-12, and CM!), a cocktail ofboth 240 and 1801, and the hsp7O antibody C92. Protein level was expressed as the sum of a proportion and Intensity score (total 0, 2—8)with 2 defined as positive staining. The cocktail 240/1801 gave the highest rate of positive staining (45%), followed by BP53-12 (35%), 1801 (27%), 240 (25%), CM! (24%), and 421 (18%), with a high correlation between antibodies. Posi tive staining with each individual antibody or the cocktail was signifi candy associated with estrogen receptor and progesterone receptor neg ativity, age < 50, and high S-phase fraction. Only staining detected by the 240/1801 cocktail was associnted with significantly worse overall survival; 85 versus 70% at 5 years for p53-negative compared to p53-positive tumors, respectively (P = 0.02). There was no association between nuclear or cytoplasmic hsp7O staining and accumulation ofp53. Patients that were p53-negative/cytoplasmic hsp70-positive had a better overaN survival than those that were p53-negative/cytoplasmic hsp7o-negative. No other com bination of p53 and hsp7O status could further define subsets of patients with a significantly different prognosis compared to p53 status alone. Tumors without a detectable p53 gene alteration by single-strand confor mation polymorphism but with accumulated p53 protein did not have relatively increased levels of hsp7O. We conclude that in node-negative breast cancer, the cocktail of two antibodies, 240/1801, resulted in the highest rate of positive staining and was most strongly associated with overall survival compared with either antibody alone or with the other individual antibodies. By immunohistochemistry, nuclear accumulation of p53 was not associated with cytoplasinic or nuclear hsp7O levels.