Overexpression of a novel cell cycle regulator ecdysoneless in breast cancer: a marker of poor prognosis in HER2/neu-overexpressing breast cancer patients

Abstract

Uncontrolled proliferation is one of the hallmarks of breast cancer. We have previously identified the human Ecd protein (human ortholog of Drosophila Ecdysoneless, hereafter called Ecd) as a novel promoter of mammalian cell cycle progression, a function related to its ability to remove the repressive effects of Rb-family tumor suppressors on E2F transcription factors. Given the frequent dysregulation of cell cycle regulatory components in human cancer, we used immunohistochemistry of paraffin-embedded tissues to examine Ecd expression in normal breast tissue versus tissues representing increasing breast cancer progression. Initial studies of a smaller cohort without outcomes information showed that Ecd expression was barely detectable in normal breast tissue and in hyperplasia of breast, but high levels of Ecd were detected in benign breast hyperplasia, ductal carcinoma in situ (DCIS) and infiltrating ductal carcinoma (IDCs) of the breast. In this cohort of 104 IDC patients, Ecd expression levels showed a positive correlation with higher grade (P=0.04). Further analyses of Ecd expression using a larger, independent cohort (954) confirmed these results, with a strong positive correlation of elevated Ecd expression with higher histological grade (P=0.013), mitotic index (P=0.032), and Nottingham Prognostic Index score (P=0.014). Ecd expression was positively associated with HER2/neu (P=0.002) overexpression, a known marker of poor prognosis in breast cancer. Significantly, increased Ecd expression showed a strong positive association with shorter breast cancer specific survival (BCSS) (P=0.008) and disease-free survival (DFS) (P=0.003) in HER2/neu overexpressing patients. Taken together, our results reveal Ecd as a novel marker for breast cancer progression and show that levels of Ecd expression predict poorer survival in Her2/neu overexpressing breast cancer patients.

Fig. 1

IHC staining of IDC and adjacent normal duct. Three independent IDC (a–c) tumor specimens which contain adjacent normal ducts were used for IHC staining using anti-Ecd antibodies. Arrows indicate Ecd staining in tumor tissues and arrow heads indicate Ecd staining in the adjacent normal ducts at a magnification of ×10

Fig. 2

a Analyses of Ecd expression in normal, DCIS and IDC breast tissues. Representative specimens (from Table 1) for Ecd staining are shown with magnification of ×40; b Correlation of Ecd expression in samples from cohort 1 with IDC tumor grade is shown. The distribution of IDC samples was: grade 1 = 18, grade 2 = 34, and grade 3 = 52, analyzed by Kruskal–Wallis test

Fig. 3

a Kaplan–Meier plot of Ecd expression in the whole series of breast cancer patients with respect to BCSS for 120 months (P = 0.008); b Kaplan–Meier plot of Ecd expression in Ecd alone, HER2 alone or HER2 + Ecd overexpressing breast cancer patients with respect to BCSS for 250 months (P = 0.04); c Kaplan–Meier plot of Ecd expression in Ecd alone, HER2 alone or HER2 + Ecd overexpressing breast cancer patients with respect to DFI for 250 months (P = 0.008)