The major heat shock protein, HSP70, protects cells from a variety of stressful stimuli, while c-myc protein allegedly stimulates expression of HSP70 by transacting on the HSP70 promotor.This study was aimed at correlating expression of HSP70 with that of c-myc protein in benign and malignant breast lesions.For this purpose, the indirect immunoperoxidase and immunoblotting techniques using monoclonal antibodies were employed.Fresh frozen sections were prepared from five fibroadenomas and 59 breast carcinomas.Immunohistochemically, both proteins were localized in the nuclei and/or cytoplasm of neoplastic and nonneoplastic epithelial cells.Expression of HSP70 and c-myc protein was comparable in malignant cells of 37 (63%) carcinomas.In 17 (29%) carcinomas, c-myc protein expression predominated over HSP70 while in 5 (8%) carcinomas HSP70 was predominant.All five fibroadenomas and most nonneoplastic epithelial cells adjacent to cancer showed strong reactivities of both proteins.Immunoblot analysis for HSP70 revealed a clear single band in the extract of tumors with strong HSP70 staining, but no or faint bands were seen in the extract of immunohistochemically HSP70-negative carcinomas.The current study, for the first time, demonstrated the expression of HSP70 in human cancer cells in vivo.The discrepancy in expression of both proteins in a certain percentage of breast carcinomas suggests the presence of mechanisms of HSP70 production not involving the c-myc protein-triggered promotor pathway.富山医科薬科大学・医学博士・甲第133号・田内克典・1991/3/20富山医科薬科大
