CHI3L1 and breast cancer: Two immuno-oncological biomarkers for disease monitoring in mice (3, 4) and breast cancer patients (22–24), CHI3L1 and LCN2, corroborated the 4T1 disease progression and showed significantly increased levels in 4T1 compared to Py230 primary tumors at 1 and 3 w p.i., but not at 6 w p.i. (Figure 4C), when 4T1 and Py230 primary tumors reached similar volumes.