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.Electronic supplementary materialThe online version of this article (doi:10.1007/s10549-011-1946-8) contains supplementary material, which is available to authorized users.

The cell cycle regulator ecdysoneless cooperates with H-Ras to promote oncogenic transformation of human mammary epithelial cells

“…35 In this context, Ecd overexpression together with ErbB2 signifies an especially poor prognosis. 5 We demonstrate that co-overexpression of Ecd and Ras in hMECs leads to a significant increase in cell cycle transit through S to G2/M under conditions of growth factor withdrawal (Fig. 3A), which is not seen in cells overexpressing either gene alone.…”

“…These findings strongly support our conclusion that Ecd is required for cell cycle progression in hMECs and that this role relies on the ability of Ecd to counter the Rb-mediated negative regulation of E2Fs, as we have delineated in a MEF system. 4 The above conclusion, together with our recent findings that Ecd is overexpressed in human breast cancers, 5 raised the possibility that Ecd could function as an oncogene in hMECs. Overexpression of Ecd alone in hMECs led to only a modest increase in cell cycle progression or proliferation under reduced growth factor conditions ( Fig.…”

“…4 Cremediated deletion of Ecd in MEFs led to G1/S arrest that was rescued by hEcd, strongly supporting an essential role of mammalian Ecd to promote cell cycle progression. 4 Based on the original identification of Ecd from a hMEC cDNA library, 3 and further findings that Ecd is overexpressed in human breast cancers, 5 we undertook studies that reveal Ecd as an essential regulator of cell cycle in hMEC, and as a cooperating oncogene in the oncogenesis when overexpressed.…”

“…Thus, it appears unlikely that Ecd can function as an oncogene by itself, consistent with its overexpression in the context of other oncogenic alterations that are known to drive human breast cancers. 5 To test if Ecd can alternatively serve as a cooperating oncogene, we utilized experimental oncogenesis of hMECs with activated H-Ras as an oncogene. While oncogenic mutations of Ras are less frequent in breast cancer, 27 overexpression of mutant Ras in hMEC and other epithelial transformation models is well-established as a strategy to reveal cooperating oncogenic roles of other genes.…”

“…Significantly, increased Ecd expression showed strong positive association with shorter breast cancer specific survival and disease-free survival in HER2/ErbB2 overexpressing patients. 5 Similarly, Ecd was also overexpressed in pancreatic cancer and its overexpression correlates with tumor progression. 6 Given the key role of Ecd in cell cycle progression as revealed by genetic studies, and an association between its overexpression and tumor progression, current studies were designed to investigate if Ecd is a positive regulator of cell cycle in hMECs.…”