CSF3 and neoplasm: One unique feature of the 4T1 TNBC model is high constitutive secretion of granulocyte-colony stimulating factors (G-CSF), a glycoprotein that stimulates the bone marrow to produce large amount of leukocytes, mostly granulocytes, which go into the peripheral blood and then infiltrate tissues such as the spleen, lymph nodes, liver, lungs, as well as the tumor.