Expression of E2F-4 in invasive breast carcinomas is associated with poor prognosis

Abstract

The E2F family of transcription factors plays a key role in the control of cellular proliferation and apoptosis. Some family members act as oncogenes and others act as tumour suppressor genes (TSGs), behaviour which appears to be tissue-specific. E2F-4 is a member of the E2F family, located at chromosome band 16q22.1, that shows frequent deletion in breast cancer, suggesting that it may function as a TSG in breast carcinogenesis. In the present study, the expression of E2F-4 was assessed immunohistochemically on paraffin wax sections from 265 breast carcinomas and expression was compared with both clinicopathological variables and disease outcome in an attempt to identify its possible role as a TSG and to assess its prognostic value, if any, in breast cancer. E2F-4 protein expression was detected in the nuclei and in the cytoplasm of normal and malignant breast epithelial cells. In the malignant tissues, no significant loss or decrease of expression was seen in association with any specific tumour type. There was a correlation between increased nuclear expression of E2F-4 and indicators of poor prognosis including larger tumour size (p = 0.000), grade 3 lesions (p = 0.033), lymph node stage (p = 0.037), and poorer Nottingham prognostic index group (p = 0.003). Increased immunoreactivity was also seen in association with the development of recurrent disease (p = 0.004), distant metastasis (p = 0.001), and poorer outcome including poorer overall survival time (p = 0.002) and shorter disease-free interval (p = 0.001). In multivariate analysis, E2F-4 was of independent prognostic significance along with grade and lymph node stage. These results suggest that E2F-4 may play a role in breast cancer progression and that increased nuclear expression is associated with more advanced tumours with poor outcomes. E2F-4 appears to have an oncogenic role rather than a tumour suppressor role in breast carcinogenesis and, hence, it is not the gene targeted by 16q22.1 loss in breast carcinoma.