ALK and glioblastoma: PTN has been proved to interact with and influence endothelial and cancer cell functions through many cell surface receptors, such as syndecan-3 in advanced stages of prostate cancer[33], anaplastic lymphoma kinase (ALK) in glioblastoma[34,35], breast cancer[36] and lung cancer[37], receptor protein tyrosine phosphatase beta/zeta (RPTPβ/ζ) in breast cancer[38].