Anaplastic large-cell lymphoma (ALCL) is a distinct subtype of peripheral T-cell lymphomas harboring chromosomal translocations involving the ALK tyrosine kinase. ALCL represents about 10% of all childhood non-Hodgkin lymphoma (NHL). The t(2;5)(p23;q35) chromosomal aberration resulting in overexpression of a chimeric oncogene, nucleophosmin-anaplastic lymphoma kinase (NPM/ALK) is the most common translocation found in these tumors. The NPM/ALK protein plays a key role in ALCL lymphomagenesis and has been shown to cause lymphoid malignancy in vitro and in vivo. Although, the prognosis of localized childhood ALCL is excellent with 5 year survival ranging from 90-95%, children with advanced stage ALCL only have a 5 year survival of about 60% with late relapses are a common complication. Since 70% of children present with advanced disease, 25%-35% of all children with ALCL will relapse or become refractory to initial treatment. Biomarkers of ALCL that can be useful for diagnosis, early detection, prediction of biologic behavior and therapy are needed. Novel targeted therapies are needed for children with refractory/relapsed ALCL and for the subset of children with a poor prognosis at diagnosis. In this application, we propose to utilize a suite of quantitative mass spectrometry-based proteomics strategies supported by sophisticated bioinformatics approaches to identify proteomic biomarkers of NPM/ALK-positive lymphomas. In specific aim 1, we will perform global quantitative proteomic analysis in an unbiased manner to identify the proteomic and phosphoproteomic changes associated with the expression of NPM/ALK in human lymphoid cells. In specific aim 2, we will establish the functional relevance of selected components of the MS-derived NPM/ALK signaling pathways. Our long-term goal is to identify robust, sensitive and specific protein biomarkers for the detection of NPM/ALK-positive ALCLs. Our studies have implications for the identification of disease biomarkers for other forms of cancers characterized by ALK deregulation.