In normal adult tissues, however, only limited expression of the full-length ALK receptor, PTN or MK was seen but overexpression of these genes was reported in a number of human cancers including brain tumors (Schulte and Wellstein, 1997; Mentlein and Held-Feindt, 2002; Powers et al., 2002; Peria et al., 2007). This evidence concerns the gene PTN and cancer.