GBM cases belonging to the mesenchymal subtype are also characterized by the expression of mesenchymal markers such as chitinase-3-like protein 1 (CHI3L1) and MET. It has been thought that the higher activity of mesenchymal and astrocytic markers such as CD44 and MERKT is linked to an epithelial-to-mesenchymal transition proper of dedifferentiated and transdifferentiated tumors. The gene discussed is CHI3L1; the disease is glioblastoma.