Abstract 4803: Quantitative proteome profiling of CD4+CD25+CCR4+ T-cells to identify potential therapeutic targets for adult T-cell leukemia (ATL) and Human T-lymphotropic virus type-1 associated myelopathy (HAM)

Abstract

Abstract Human T-cell leukemia virus type 1 (HTLV-1) is a retro-viruse known as the one of the causative factors of adult T-cell leukemia/lymphoma (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), both of which are developed after a long latency period over 30 years. ATL is developed in HTLV-1-infected individuals at the prevalence of 5% with poor prognosis. Meanwhile, HAM/TSP has a prevalence of approximately 0.25% of HTLV-1-infected individuals and is characterized by its neurological symptoms, such as sensory disturbance of lower extremities. Regardless of the importance of early diagnosis and appropriate therapeutic intervention for the patients, the diagnostic markers or the effective molecular treatment targets have not been discovered yet. The objective of the present study is to identify determinants responsible for the development of ATL or HAM/TSP, which could be useful as the potential therapeutic targets or prognostic biomarkers. Here we performed a quantitative proteomic profiling of CD4+CD25+CCR4+ T-cells, which are known as the predominant viral reservoir, by means of label-free quantification analysis on the Expressionist proteome server. CD4+CD25+CCR4+ T cells were isolated from the peripheral blood mononuclear cells derived from 6 uninfected volunteers, 5 asymptomatic carriers, 9 HAM/TSP patients, and 9 ATL patients. The isolated T cells from 29 individuals were lysed, digested, and subjected to LC/MS/MS analyses. Subsequently, we integrated the 29 LC/MS/MS data on the Expressionist proteome server and conducted label-free quantification analysis, obtaining 14,064 non-redundant peptides. Kruskal-Wallis test and leave-one-out cross validation test finally extracted 20 peptides derived from 17 distinct proteins, which allowed statistical classification of four pathological groups. The 17 candidates included a couple of proteins which are well known as an apoptotic enzyme-substrate pair; Calpain-2 (CAN2) and Spectrin alpha chain (SPTA2). Our mass spectrometric quantification data demonstrated that CAN2 expression was significantly down-regulated in CD4+CD25+CCR4+ cells from ATL patients, while SPTA2 was abnormally accumulated. Indeed, exogenous overexpression of CAN2 remarkably induced apoptosis to ATL cell line SO-4 (expressing high level of SPTA2) but not in KOB cells (SPTA2 negative). These observations indicate that CAN2 and SPTA2 coordinately regulate the apoptosis and the suppression of CAN2 in HTLV-1 infected T-cells would be one of the plausible causes of ATL onset. Our label-free quantification-based proteome profiling of CD4+CD25+CCR4+ T cells enabled us to identify 17 pathological determinants for HAM/TSP and ATL, which could contribute to developing new strategies for treatment and diagnosis in the future. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4803. doi:1538-7445.AM2012-4803