MTOR and neoplasm: Previous studies have also reported that YKL-40 may play a role in the regulation of phosphatidylinositol 3 kinase (PI3K)/AKT/mTOR pathway or Ras/Raf/MEK/ERK cascade, which is one of the best-studied signal transduction pathways connected with tumor survival, transformation, invasion, and metastasis [25, 26].