Analysis of the κ light chain variable region in multiple myeloma

Abstract

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.

Origin and diversification of the clonogenic cell in multiple myeloma: lessons from the immunoglobulin repertoire

“…In total, 27 V genes have been analyzed in three of the above studies. 50,53,54 However, no definite conclusion can yet been reached regarding their preferential distribution in the existing V gene families or biased usage of certain V genes in MM.…”

“…50 The pattern of mutations in the V rearranged genes revealed an asymmetric distribution in CDRs compared to FWRs. Most of the mutations occurring in FWRs were S, whereas mutations in the CDRs were more frequently of the R type.…”

“…Sahota et al 53 observed a strikingly high usage of the A27 (Hum v325) V gene in 33% of their cases. In sharp contrast, this gene has not been found rearranged in any of the cases analyzed by us, 50 Wagner et Table 1 Collective data on V gene usage in MM from various reports V gene (%)…”

“…The rearranged V genes identified in five published reports [50][51][52][53][54] were compared for differences and similarities regarding individual gene usage by MM clonogenic B cells (Table 1). A preference for over-representation of the O8-18 and O2-12 V genes, which belong to the V I family was observed.…”

Analysis of Vλ-Jλ expression in plasma cells from primary (AL) amyloidosis and normal bone marrow identifies 3r(λIII) as a new amyloid-associated germline gene segment

“…A recent exhaustive revision of nucleotide sequencing data in myeloma and related conditions found no evidence of bias in V use; 27 3r was rearranged only twice in a total of 27 myeloma V regions (7.4%). [28][29][30] It is unknown whether the 2 3r-myeloma patients had amyloid. We are now sequencing myeloma V regions in patients without associated amyloidosis (biopsy negative with follow-up Ͼ 2 years) and found 3r in 1 of 10 cases (V.P., unpublished observations, August 2001).…”