Background: Recent studies revealed that gene amplification and series of oncogenic mutations of anaplastic lymphoma kinase (ALK) are potent oncogenic factors of neuroblastoma (NB). In addition, enhanced ALK expression even without genetic alteration of ALK.is a poor prognostic factor in NB patients. We investigated the specific downstream signaling molecules of ALK in NB to investigate the unique role of ALK in oncogenesis of NB.
Methods: To elucidate the role of ALK in oncogenesis of NB cells, phosphotyrosine-containing proteins associated with ALK were investigated by purification and mass-spectrometry analysis.
Results: SHP2 (SH-PTP2/PTPN11), a tyrosine phosphatase was identified among the ALK-binding tyrosine-phosphorylated proteins. Since oncogenic contribution of SHP2 phosphatase has been reported in several cancers, and point mutations of SHP2 was recently reported in neuroblastoma as well, we examined the role of SHP2 phosphatase in the neuroblastoma cells. The ALK-dependent N’-terminal tyrosine phosphorylation of SHP2, which is known to regulate phosphatase activity of SHP2, was revealed in NB-39-nu NB cells which harbor gene amplification of wild-type ALK. It was also shown that SHP2 is associated with ALK through SH2 domains of SHP2 via ShcC, a docking protein we originally found as a major binding partner of ALK (Miyake et al, 2002) which regulates NB oncogenicity in a tyrosine phosphorylation-dependent manner. SHP2 appeared to mediate ALK-dependent oncogenic property such as proliferation or migration of NB-39-nu cells, while SHP2 also induced dephosphorylation of ALK protein in NB-39-nu cells. These data suggest that SHP2-ShcC complex control ALK-dependent malignant characteristics of NB by enzymatic interaction between molecules. Further studies are currently on-going to clarify the precise mechanism.