794 Clonal evolution in progressive lymphomas

Abstract

Introduction Alterations in clinical behaviour, morphological appearance and immunophenotype are frequently observed in relapsing non-Hodgkin's lymphoma (NHL). The aim of this study was to analyse a material of relapsing or progressive lymphomas with respect to clonality changes, using the immunoglobulin heavy-chain (IgH) as a marker of clonality. Material and methods 52 samples taken during the course from 19 NHL cases were investigated with RFLP analysis of the IgH locus, VH gene family specific PCR-SSCP and in five selected cases by sequence analysis of VH gene fragments. Seven cases showed transformation or discordant lymphomas during the course. Results In 10 cases no alteration of the IgH locus could be detected by the methods used, By RFLP 5/7 cases with transformed/discordant lymphomas and 3/l2 with unchanged morphology showed altered IgH patterns. Three cases showed evidence of oligoclonality (> 2 rearranged bands) on RFLP. Altered VH gene PCR-SSCP pattern and/or VH gene family utilization was observed in 7 cases, 6 of these also showing altered IgH-RFLP. In two cases, a rearrangement involving an additional VH family was amplified at relapse. In two other cases the VH rearrangement from diagnosis was not detected at relapse. Sequence analysis revealed point-mutations in the 4 cases (4, 4, 6, 20 mutations, respectively) with altered PCR-SSCP pattern. In one of the two cases with a novel VH gene family utilization at relapse, a VH gene replacement was detected. In the other case, no sequence homology was found between the samples. Conclusion Alterations of the clonal IgH rearrangements during the course occurred in about half of the cases, mainly in the transformed/discordant lymphomas and were due to point mutations as well as to presence of different clones of malignant cells. Alterations in clinical behaviour, morphological appearance and immunophenotype are frequently observed in relapsing non-Hodgkin's lymphoma (NHL). The aim of this study was to analyse a material of relapsing or progressive lymphomas with respect to clonality changes, using the immunoglobulin heavy-chain (IgH) as a marker of clonality. 52 samples taken during the course from 19 NHL cases were investigated with RFLP analysis of the IgH locus, VH gene family specific PCR-SSCP and in five selected cases by sequence analysis of VH gene fragments. Seven cases showed transformation or discordant lymphomas during the course. In 10 cases no alteration of the IgH locus could be detected by the methods used, By RFLP 5/7 cases with transformed/discordant lymphomas and 3/l2 with unchanged morphology showed altered IgH patterns. Three cases showed evidence of oligoclonality (> 2 rearranged bands) on RFLP. Altered VH gene PCR-SSCP pattern and/or VH gene family utilization was observed in 7 cases, 6 of these also showing altered IgH-RFLP. In two cases, a rearrangement involving an additional VH family was amplified at relapse. In two other cases the VH rearrangement from diagnosis was not detected at relapse. Sequence analysis revealed point-mutations in the 4 cases (4, 4, 6, 20 mutations, respectively) with altered PCR-SSCP pattern. In one of the two cases with a novel VH gene family utilization at relapse, a VH gene replacement was detected. In the other case, no sequence homology was found between the samples. Alterations of the clonal IgH rearrangements during the course occurred in about half of the cases, mainly in the transformed/discordant lymphomas and were due to point mutations as well as to presence of different clones of malignant cells.