148753

FAM163A

C1orf76|NDSP|RP11-12M5.2;family with sequence similarity 163, member A;FAM163A;family with sequence similarity 163, member A

cebelin|neuroblastoma derived secretory protein|neuroblastoma-derived secretory protein|protein FAM163A

1q25.2

protein-coding

Secreted proteins such as growth factors, cytokines, and chemokines play important roles in tumor development. Through expression microarray and bioinformatic analysis, we discovered a novel secreted protein, neuroblastoma-derived secretory protein (NDSP). The NDSP gene is found on chromosome 1q25.2 and encodes a 167 amino acid protein with a putative signal peptide. Using real-time PCR and immunoblotting, we find that NDSP is specifically overexpressed in neuroblastoma at much higher levels than other adult and pediatric malignancies and normal tissues. NDSP is an 18-kDa protein that can be secreted by NDSP-transfected HEK-293T cells, as well as, neuroblastoma cell lines endogenously expressing NDSP. Inhibiting NDSP expression in neuroblastoma cell lines with retrovirally transduced NDSP small hairpin interfering RNA, sh-NDSP, results in decreased cellular proliferation and colonyformation. We also find inhibited extracellular signal-regulated kinase (ERK)1/2phosphorylation in the sh-NDSP cell line. Treating the parental cell line with MAP/ERK kinase 1/2 inhibitors, which diminish ERK1/2 phosphorylation, results indecreased cell proliferation. Culturing these transduced cells with recombinant NDSP, reintroducing NDSP overexpression in the knockdown cell line, or inducing Ras oncogene overexpression for constitutive ERK1/2 activation results in a reversal of the growth-inhibited phenotype and proliferation rates similar to the control cells. In addition, reintroduction of NDSP overexpression in the sh-NDSPcell line results in ERK1/2 phosphorylation similar to control. We conclude thatNDSP is specifically overexpressed in neuroblastoma and actively secreted from tumor cells. Furthermore, NDSP serves as a growth factor for neuroblastoma tumorcells through activation of the ERK-mediated proliferation pathway.