CONICET | Buscador de Institutos y Recursos Humanos

Chronic lymphocytic leukemia (CLL) is the most common form of adult leukemia in the Western world, with a highly variable clinical course. The mutational status of the immunoglobulin variable heavy-chain (IGHV) gene represent one of the best prognostic markers in this pathology. In this study, we analyzed the association between IGHV repertoire and mutation status in a series of 167 Argentinian patients with CLL (103 males; mean age: 65.5 years; 82% at initial stages) and correlate them with clinical parameters, cytogenetic and fluorescence in situ hybridization (FISH) alterations (13q, 11q and 17p deletions and trisomy 12). Amplification of IGHV regions by PCR was performed on cDNA using VH framework region 1 consensus family specific primers (VH1-VH6) and JH or Cµ primers. PCR products were sequenced bi-directionally and analyzed using IgBLAST and the IMGT/V-QUEST database. IGHV sequences with less than 98% homology with respect to the germline counterpart were considered as M, usually associated to good prognosis. Fifty seven percent of patients were M-CLL, and 42.6% were UM-CLL. The most frequently used IGHV families were VH3 >VH4>VH1. The IGHV3-23 gene (10.1%) was the most commonly used, followed by IGHV1-69 (9.5%), IGHV4-34 (8.9%) and IGHV3-21(6.5%). Stereotyped HCDR3 (heavy chain complementary determining region 3) was found in 13% of patients and clusters #2, #4 and #7 were the most frequently found. Normal karyotypes, FISH with less than 2 aberrations and trisomy 12 were more frequently found in M-CLL (p=0.047, p=0.0001 and p=0.01, respectively); while deletion 17p and lower beta2-microglobulin were more frequent in UM-CLL (p=0.001 and p=0.049, respectively). Overall survival was significantly shorter for UM-CLL patients (50.5 months) with respect to M-CLL cases (98.5 months) (p=0.0001). Our results confirm the role for VH mutational profile in predicting CLL prognosis and their correlation with other known prognostic markers.