CTLA4 and breast cancer: The five hub genes, CD40LG, CD5, CD27, CD3E and CD52, are cluster of differentiation (CD) leukocyte surface antigens, which are mainly related to immune function.[41]Table 6 summarizes current studies on these five hub genes in breast cancer.[42–59] CD40LG, also called CD154 or CD40L, is mainly expressed in activated T lymphocytes and belongs to the tumor necrosis factor family.