Nm23-H1 metastasis suppressor gene expression in primary breast cancer: associations with axillary lymph node status, tumour size, type and grade

Abstract

The nm23-H1 gene has tumour suppressor functions and is a putative metastasis suppressor. Higher levels of expression of the gene in breast carcinoma have been associated with the absence of lymph node metastasis, and with longer relapse free intervals and overall survival.Expression levels of nm23-H1 in breast carcinoma were examined by Northern and slot blot in a consecutive series of 105 patients. The levels of nm23-H1 mRNA expression were examined for associations with axillary lymph node metastasis, and with tumour size, tumour type and grade, mitotic rate, nuclear size and pleomorphism and vascular invastion, in 97 cases of invasive cancer. No statistically significant differences in nm23 expression levels between axillary node negative and axillary node positive infiltrating duct carcinomas were observed. There was no correlation between nm23-H1 expression levels and other histopathologically determined prognostic factors. Higher levels of gene expression were demonstrated in pure ductal carcinoma in situ (DCIS) lesions when compared to invasive tumours; further analysis suggested that DCIS components within invasive tumours contributed to measurements of nm23 expression, possibly masking the lower expression levels of the invasive component in some cases. Further correlative studies, using in situ hybridization or gene product immunohistochemistry would be most suited to determining the contribution of different tissue components in breast cancer.