PROGNOSTIC-SIGNIFICANCE OF P53 OVEREXPRESSION IN PRIMARY BREAST-CANCER - A NOVEL LUMINOMETRIC IMMUNOASSAY APPLICABLE ON STEROID-RECEPTOR CYTOSOLS

A novel quantitative luminometric immunoassay (LIA) has been developed for the measurement of wild-type and mutant p53 protein in extracts f rom breast tumour tissue. The LIA was found to yield reliable estimate s of p53 expression in cytosol samples routinely prepared for steroid receptor analysis as compared with results obtained with immunohistoch emical analysis. The LIA was evaluated on 205 primary breast tumour cy tosols prepared for steroid receptor analysis and stored frozen at -80 degrees C for 6-8 years, p53 protein being detected in 65% of the sam ples (range 0.01-23 ng mg(-1) protein). Using an arbitrary cut-off val ue of 0.15 ng mg(-1) protein, 30% of the tumours were classified as ma nifesting p53 overexpression. Significant and independent correlations were found to exist between p53 overexpression and shorter disease-fr ee (P < 0.001) and overall survival (P = 0.039) at a median duration o f follow-up of 50 months. p53 overexpression was related to low oestro gen receptor content and high proliferation rate (S-phase fraction). N o relationship was found to tumour size or the presence of lymph node metastasis. Three tumours possessed an extremely high p53 content (> 1 0 ng mg(-1) protein), all of which were of medullary or high-grade duc tal type, oestrogen and progesterone receptor negative, DNA non-diploi d, had S-phase fractions of > 22% and recurred within 1-2 years. In su mmary, a new sensitive and quantitative LIA suitable for routine analy sis of p53 protein in steroid receptor cytosol preparations from breas t tumours has been developed to confirm the prognostic importance of p 53 protein accumulation in human breast cancer.