Overexpression of h-prune in breast cancer is correlated with advanced disease status

Purpose: The h-prune gene is involved in cellular motility and metastasis formation in breast cancer through interacting with the nm23-H1 protein. The aim of this study was to better define the clinical and pathological role of h-prune in breast cancer patients. Experimental Design: Using immunohistochemistry, we assessed h-prune and nm23-H1 protein expression in two series of breast cancer patients: (i) in 2,109 cases with pathological reports on primary tumors; and (ii) in 412 cases with detailed clinical information. To assess the role of DNA amplification in gene activation, the h-prune copy number was evaluated by fluorescence in situ hybridization analysis in 1,016 breast cancer cases. Results: In the patients tested (2,463), 1,340 (54%) had an increased level of h-prune expression; a positive immunostaining for nm23-H1 was observed in 615 of 2,061 (30%) cases. Overexpression of h-prune was associated with multiple gene-copy number at chromosome 1q21.3 in a very limited fraction of cases (68 of 1,016; 6.7%), strongly indicating that alternative pathways induce h-prune activation in breast cancer. Multivariate Cox regression analysis showed that neither h-prune overexpression nor decreased nm23-H1 immunostaining are independent prognostic factors. However, a significant association of h-prune overexpression with either advanced lymph node status (p=0.017) or presence of distant metastases (p=0.029) was observed. Conclusions: Although not significantly correlated with overall survival, positive h-prune immunostaining identifies subsets of breast cancer patients with higher tumor aggressiveness. Further investigations using larger collections of advanced breast cancer patients are required for assessing the predictive role of h-prune in breast cancer.