CHI3L1 and posterior cortical atrophy: In silico analysis of YKL40 mRNA expression using publicly available gene expression data (Gene Expression Omnibus datasets (GDS), http://www.ncbi.nlm.nih.gov/gds) found YKL40 gene expression to be significantly increased in patients with metastatic PCa when compared with primary PCa and normal prostate tissue (Fig. 3C, GDS2545; Chandran et al. 2007).