Characteristics of the TCR Vbeta Repertoire and Identical Clonally Expanded T Cells in Chronic Myeloid Leukemia Patients in Advanced Phase with ABL Mutations

Abstract

Tumor specific or related antigen cytotoxic lymphocyte (CTL) have been identified in chronic myeloid leukemia patients, however, whether they are constituted by specific type of T cell receptor chains has not been illustrated so far. Previous studies have reported abnormal TCR repertoires and clonally expanded TCR Vβ T cells in chronic myeloid leukemia in chronic phase (CP-CML). In this study, we investigated the distribution and clonality of the TCR Vβ repertoire in 5 CML patients in blast crisis (BC-CML) and one in acceleration phase (AP-CML) with ABL kinase domain mutations (KDMs) including T315I, E255K, F317L+S417Y, Y-253F and L387M+T-315A. Examination of TCR Vβ expression and clonality was performed by reverse transcription-polymerase chain reaction (RT-PCR) combined with GeneScan analysis. Significantly skewed TCR Vβ repertoires were observed in those patients, and 4 to 8 oligoclonally expanded TCR Vβ subfamilies could be identified in each sample, which distributed in 15/24 different subfamilies (TCR Vβ4, Vβ5, Vβ6, β8, Vβ9, Vβ10, Vβ15, Vβ16, Vβ17, Vβ18, Vβ19, Vβ21, Vβ22, Vβ23, Vβ24). Intriguingly, a relatively highly expanded Vβ9 clone with the same length as CDR3 (139 bp) was found in all three CML patients in lymphoid blast crisis (LBC-CML) who had different KDMs, but the clone was not detected in the other two CML patient in myeloid blast crisis (MBC-CML) or the one CML patients in accelerated phase. In conclusion, restricted TCR Vβ repertoire expression and decreased clone complexity was a general phenomenon in the BC-CML patients with different KDMs, indicating the T-cell immunodeficiency status of these patients, and clonally expanded Vβ9 T cell clones may represent a specific immune response to leukemia-associated antigens in LBC-CML patients.