Kosmas C, Viniou N A, Stamatopoulos K, Courtenay-Luck N S, Papadaki T, Kollia P, Paterakis G, Anagnostou D, Yataganas X, Loukopoulos D
First Department of Medicine, University of Athens School of Medicine, Laikon General Hospital, Greece.
Br J Haematol. 1996 Aug;94(2):306-17. doi: 10.1046/j.1365-2141.1996.d01-1815.x.
The study of immunoglobulin heavy chain gene rearrangements in multiple myeloma has revealed extensive divergence from the germline sequences, but no intraclonal diversity with disease evolution. Our study investigated the state of the rearranged kappa light chain variable region (V kappa) gene segments as well as abortive V kappa family gene usage in cases of multiple myeloma expressing lambda light chain. We studied 11 cases of kappa and five cases of lambda light chain-expressing multiple myeloma. Total cellular RNA was extracted from the bone marrow of patients with overt disease and subjected to reverse transcription-polymerase chain reaction (RT-PCR) analysis to amplify clonally rearranged variable region sequences. Direct nucleotide sequencing by the dideoxy-chain termination method was performed on the RT-PCR products. We did not observe preferential usage of certain V kappa gene families. Mutation frequencies of the V kappa segments varied in number. In the majority of cases, extensive somatic mutations occurred within the complementarity determining regions (CDRs) of V kappa, whereas only a limited degree of divergence from the germline was observed in others. In all cases studied. replacement mutations tended to cluster in the CDRs, a finding compatible with an antigen-driven somatic hypermutation process. In 3/5 cases of lambda light-chain expressing multiple myeloma, abortively rearranged V kappa gene segments were amplified from genomic DNA; in two cases a non-templated nucleotide insertion rendering the V kappa sequences out-of-frame was observed, and in the third a stop codon was identified in the open reading frame of the V kappa sequence. Somatic mutations were observed in all cases of abortive V kappa genes studied; however, their distribution does not suggest selection by antigen. We conclude that somatic mutations observed in the V kappa regions of myeloma cells are of variable extent and suggest operation of the antigen selection process. Lack of or minimal somatic hypermutation in a few cases may be in some way implicated in the biological heterogeneity of the disease.
对多发性骨髓瘤中免疫球蛋白重链基因重排的研究显示，其与种系序列存在广泛差异，但在疾病进展过程中不存在克隆内多样性。我们的研究调查了表达λ轻链的多发性骨髓瘤病例中重排的κ轻链可变区（Vκ）基因片段的状态以及流产型Vκ家族基因的使用情况。我们研究了11例表达κ轻链和5例表达λ轻链的多发性骨髓瘤病例。从显性疾病患者的骨髓中提取总细胞RNA，并进行逆转录-聚合酶链反应（RT-PCR）分析，以扩增克隆性重排的可变区序列。对RT-PCR产物采用双脱氧链终止法进行直接核苷酸测序。我们未观察到某些Vκ基因家族的优先使用情况。Vκ片段的突变频率各不相同。在大多数病例中，Vκ的互补决定区（CDR）内发生了广泛的体细胞突变，而在其他病例中仅观察到与种系有有限程度的差异。在所有研究的病例中，置换突变倾向于聚集在CDR中，这一发现与抗原驱动的体细胞超突变过程相符。在3/5例表达λ轻链的多发性骨髓瘤病例中，从基因组DNA中扩增出了流产型重排的Vκ基因片段；在2例中观察到非模板化核苷酸插入使Vκ序列移码，在第3例中在Vκ序列的开放阅读框中鉴定出一个终止密码子。在所研究的所有流产型Vκ基因病例中均观察到体细胞突变；然而，它们的分布并不表明是由抗原选择的。我们得出结论，骨髓瘤细胞Vκ区域中观察到的体细胞突变程度各异，提示存在抗原选择过程。少数病例中缺乏或仅有极少的体细胞超突变可能在某种程度上与该疾病的生物学异质性有关。
