Over the past two decades, emerging data have found that YKL-40, a secreted glycoprotein, is elevated in a broad spectrum of human diseases including cancers, liver injury, asthma, diabetes, inflammatory diseases, and cardiac disorders. In breast cancer, increased serum levels of YKL-40 are correlated with cancer metastasis and short survival, suggesting that serum levels of YKL-40 serve as a cancer biomarker. YKL-40 has the ability to stimulate vascular endothelial cell activation and suppress mammary epithelial...