Expression and prognostic value of Id protein family in human breast carcinoma

Inhibitors of DNA binding/inhibitors of differentiation (Id) protein family (Id-1, -2, -3 and -4) of helix-loop-helix proteins have been shown to be involved in carcinogenesis and are regarded as prognostic markers in several types of human cancers. However, the roles of Id proteins during breast carcinoma progression remain unclear. The objective was to study the effects of Id proteins in breast cancer. The expression of Id-1, Id-2, Id-3 and Id-4 proteins was examined in 122 dissected female human breast carcinoma tissues and 22 normal female breast specimens by immunohistochemical assay and the relationship between Id staining and clinical pathological characteristics of breast cancer was also analyzed. The over-expressed Id-1 and down-regulated Id-4 proteins were found both correlated with poorer differentiation and more aggressive behavior of the tumor. Id-1 protein could be termed as a negative prognostic marker while Id-4 protein as a positive marker for patients with breast carcinoma. Although the differentially expressed Id-2 and -3 may be correlated with some clinical parameters, they could not be used as independent prognostic factors in human breast cancer.