CHI3L1 and breast cancer: Based on qRT-PCR analysis of cultured cells, the highest level of YKL-40 gene expression was detected in EO771.LMB breast cancer cells, whereas low levels were observed in MC38 colon cancer and undetectable levels in B16F10 melanoma cells, LL2 lung cancer cells, and PANO2 pancreatic cancer cells (Figure 2A).