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- Thorsélius, Mia, 1973-
(författare)
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Immunoglobulin Gene Analysis in Different B cell Lymphomas : With Focus on Cellular Origin and Antigen Selection
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- B cell lymphoma (BCL) comprises a biologically and clinically heterogeneous group of tumors deriving from different stages of B cell development. The immunoglobulin (Ig) variable heavy chain (VH) gene rearrangement is unique for each BCL and can be used to reveal cellular origin, to study signs of antigen selection and to quantify tumor cell load.The normal counterpart of mantle cell lymphoma (MCL) has been postulated to be a naïve B cell and in hairy cell leukemia (HCL) it is considered to be a post-germinal centre B cell. We analyzed the VH gene rearrangements in 110 MCLs and 32 HCLs by PCR amplification and sequencing. Most MCLs (84%) displayed VH genes lacking somatic hypermutation (SHM), thus correlating to a naïve cell origin, whereas a subgroup (16%) showed SHM, implying derivation from a more differentiated B cell. In HCL, a majority of cases (84%) displayed SHM with signs of intraclonal heterogeneity and 16% had unmutated VH genes, thus questioning the cell of origin in HCL. Biased usage of particular VH genes was detected in both HCL (VH3-30) and MCL (VH3-21 and VH4-34), which indicates that antigen selection may be involved in lymphoma development. Furthermore, VH3-21+ MCLs showed a highly restricted Vλ3-19 gene use and they also had a superior outcome compared to other MCLs.Rearrangement analysis of 67 VH3-21+ chronic lymphocytic leukemia (CLL) cases from three different countries verified, regardless of geographical origin, the short and highly homologous complementarity determining region 3s and the strikingly biased usage of the Vλ2-14 gene (75%), as previously reported in CLL. This further supports that antigen selection by a common antigenic epitope may have occurred in VH3-21+ CLLs. In an autologous transplantation study of 30 multiple myeloma patients, we quantified the tumor content in the autografts before and after stem cell selection using clone-specific PCR. We conclude that stem cell selection reduced the number of clonal cells linearly, but purging could not totally eliminate the tumor cells from the graft, thus increasing the risk of a relapse.Altogether, our data allowed us to define new BCL subsets and to gain insights into the potential role of antigen selection in BCL development as well as the monitoring of tumor cell load using Ig gene rearrangements analysis.
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| 2. |
- Tobin, Gerard, 1971-
(författare)
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Immunoglobulin Gene Analysis in Chronic Lymphocytic Leukemia : Characterization of New Prognostic and Biological Subsets
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Recent studies have shown that the somatic mutation status of the immunoglobulin (Ig) VH genes can divide chronic lymphocytic leukemia (CLL) into two prognostic subsets, since cases with mutated VH genes display superior survival compared to unmutated cases. Biased VH gene usage has also been reported in CLL which may reflect antigen selection.We performed VH gene analysis in 265 CLL cases and confirmed the prognostic impact of the VH mutation status. Preferential VH gene usage was also demonstrated in both the mutated and unmutated subset. Interestingly, CLL cases rearranging one particular VH gene, VH3-21, displayed poor outcome despite that two-thirds showed mutated VH genes. Many of the VH3-21 cases expressed λ light chains, rearranged a Vλ2-14 gene, and had homologous complementarity determining region 3s (CDR3s), implying recognition of a common antigen epitope. We believe that the VH3-21 subset comprises an additional CLL entity.To further explore the B-cell receptors in CLL, we analyzed the VH gene rearrangements and, specifically, the heavy chain CDR3 sequences in 346 CLL cases. We identified six new subgroups with similar HCDR3 features and restricted VL gene usage as in the VH3-21-using group. Our data indicate a limited number of antigen recognition sites in these subgroups and give further evidence for antigen selection in the development of CLL.Different cutoffs have been suggested to distinguish mutated CLL in addition to the 2% cutoff. Using three levels of somatic mutations, i.e. <2%, 2-5% and >5%, we divided 323 CLLs into subsets with divergent survival. This division revealed a low-mutated subgroup (2-5%) with inferior outcome that would have been masked using the traditional 2% cutoff. A 1513A/C polymorphism in the P2X7 receptor gene was reported to be more frequent in CLL, but no difference in genotype frequencies was revealed in our 170 CLL cases and 200 controls. However, CLL cases with the 1513AC genotype showed superior survival than 1513AA cases and this was in particular confined to CLL with mutated VH genes. In summary, we could define new prognostic subgroups in CLL using Ig gene rearrangement analysis. This also allowed us to gain insights in the biology and potential role of antigen involvement in the pathogenesis of CLL.
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