The Critical Role of Inhibitor of Differentiation 4 in Breast Cancer: From Mammary Gland Development to Tumor Progression

Inhibitor of differentiation 4 (ID4) is a highly conserved DNA-binding inhibitory protein of mammals, and its main role is to bind basic helix–loop–helix (b-HLH) so that it loses its DNA-binding activity, which in turn regulates the transcription of key genes, regulating cell differentiation and proliferation as the physiological function. Breast tissue is a highly heterogeneous tissue organ with a strong capacity for remodeling and differentiation, and studies of breast carcinogenesis suggest that the mechanisms regulating the differentiation of breast tissue interact critically with tumorigenesis. The expression level of ID4 and its regulatory mechanism play a crucial role in the study of breast cancer, but its oncogenic or oncostatic role has not yet been unanimously identified, and its regulatory mechanism in breast cancer still needs to be further elucidated. This review summarizes and analyzes the relevant studies of ID4 and the research progress in breast cancer, integrating the development of breast tissue and tumorigenesis with the regulatory role of ID4, to provide some insights into develop new treatment strategies and diagnostic biomarkers.