Because TAMs located in the stroma of breast cancers are primarily M2 macrophages activated by IL-4-producing CD4+ T cells [25], we mimicked this TAM-populated microenvironment by co-cultivating SKBR3 breast cancer cells with IL-4-activated MDMs in a Boyden chamber, which prevents direct cell-cell contact. The gene discussed is CD4; the disease is breast carcinoma.