MDM2 GENE ALTERATIONS AND MDM2 PROTEIN EXPRESSION IN BREAST CARCINOMAS

This study investigates the mdm2 gene status and expression in 66 surg ically resected human breast carcinomas, with correlations with clinic o-pathological and biological data (histological type, grading, steroi d receptor status, p53 expression, proliferative activity). Four (7.7 per cent) out of 52 informative cases bear mdm2 gene amplification (fo ur- to ten-fold) and 8 (15.4 per cent) of 52 cases showed borderline a mplification (three-fold). Nine (13.6 per cent) out of 66 cases showed strong mdm2 nuclear immunoreactivity. Twenty-seven (40.9 per cent) ca ses showed isolated mdm2 reactive nuclei. All cases with clear amplifi cation showed a high percentage of mdm2 immunoreactive nuclei. The rel ationship between gene amplification and mdm2 protein expression is hi ghly significant (P<0.0001). No association was observed between mdm2 gene amplification and any of the considered clinico-pathological and biological parameters, while mdm2 immunoreactivity showed a significan t association only with oestrogen receptor immunoreactivity (P=0.009). p53 expression was associated neither with mdm2 gene amplification no r with mdm2 immunoreactivity. It could be tempting to hypothesize that the evaluation of the combined mdm2/p53 immunohistochemical phenotype in human breast carcinoma could give us better prognostic information than the evaluation of the expression of the p53 protein alone.