Overexpression of human ortholog of mammalian enabled (hMena) is associated with the expression of mutant p53 protein in human breast cancers.

The human ortholog of mammalian enabled (hMena), a member of the enabled/vasodilator-stimulated phosphoprotein (Ena/VASP) family, is an actin regulatory protein involved in the regulation of cell motility. Increasing evidence suggests that hMena overexpression is involved in human cancers, but the upstream events that influence the expression of hMena remain to be elucidated. In this study, we performed immunohistochemical analysis of the expression of hMena protein in paraffin-embedded archival tissues of infiltrating ductal carcinomas (IDCs) obtained from 52 cases. We found that elevated hMena expression is associated with larger tumor size (>2.5 cm, p<0.01), HER2 expression (p<0.05), p53 index (p<0.03) and Ki67 index (p<0.01), suggesting that hMena is a predictor of poor prognosis in IDCs. The histological characteristics of each specimen showed that hMena was overexpressed in the tumor cells at the invasive front of IDCs, indicating that hMena expression is at least partly mediated by tumor cell-matrix interactions. To explore the role of the absence of p53 function in hMena overexpression of IDCs, wild-type p53 cDNA was introduced into SW620 cells, which originally express mutant p53. In wild-type p53-transfected cells, hMena mRNA expression was decreased to 70% of the levels in mock transfected cells (p<0.01). In conclusion, our study indicates that hMena overexpression is involved in the progression of IDCs, and raises the possibility that wild-type p53 may suppress hMena expression.