Relationship Between Elevated Immunoglobulin Free Light Chain and the Presence of Igh Translocations in Multiple Myeloma

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Relationship between elevated immunoglobulin free light chain and the presence of IgH translocations in multiple myeloma

S Kumar1, L Zhang2, A Dispenzieri1, S Van Wier3, JA Katzmann4, M Snyder4, E Blood5, R DeGoey1, K Henderson1, RA Kyle1, AR Bradwell6, PR Greipp1, SV Rajkumar1 and R Fonseca3

1Division of Hematology, Mayo Clinic, Rochester, MN, USA; 2Department of Biostatistics, ECOG, Boston, MA, USA; 3Department of Hematology, Mayo Clinic, Scottsdale, AZ, USA; 4Laboratory Medicine, Mayo Clinic, Rochester, MN, USA; 5Dartmouth Medical School, Lebanon, NH, USA and 6Department of Immunology, Birmingham University Medical School, Birmingham, UK

Elevated immunoglobulin free light chain (FLC) level and k- and l-light chains that circulate as monomers or dimers, not abnormal FLC ratio are commonly seen in multiple myeloma bound to the immunoglobulin heavy chain.4–6 The estimation of (MM) and have prognostic implications. We hypothesized that free light chain levels and their ratio has utility in screening, presence of immunoglobin heavy chain (IgH) translocations leads to unbalanced production of light chains and more prognostication and treatment response assessment in nearly extreme abnormalities of FLC, and may explain the prognostic all the monoclonal plasma cell disorders, including multiple value of FLC. We studied 314 patients with newly diagnosed myeloma, smoldering myeloma, monoclonal gammopathy of MM enrolled in a phase III trial, in whom results of fluorescence undetermined significance, plasmacytomas and light chain in situ hybridization testing and data on serum FLC levels were amyloidosis.7–13 available. Cytogenetic analyses and FLC estimates were Translocations involving the immunoglobulin heavy chain performed on stored samples and results were correlated with clinical data. The median ratio (FLC ratio) and the absolute (IgH) locus on chromosome 14 can be detected using difference (FLC diff) between the involved and uninvolved FLC fluorescence in situ hybridization (FISH) in over half of the were higher among those with IgH translocations, especially patients with myeloma.14–16 The five recurrent translocations t(14;16). In multivariate analysis, the prognostic value of FLC with identifiable partner chromosomes include t(11;14), t(4;14), estimates on progression-free and overall survival were t(14;16), t(6;14) and t(14;20), which lead to dysregulation of independent of high-risk IgH translocations t(4;14) and specific genes that are thought to have a role in the pathogenesis t(14;16). A combination of the risk factors; either abnormal 17 FLC estimate and/or the presence of high-risk IgH transloca- of myeloma and its manifestations. The presence of certain tion, achieved better prognostic stratification. We conclude that IgH translocations, such as t(4;14) and t(14;16), has been shown patients with IgH translocations have higher FLC levels and to be associated with a poor outcome in patients with abnormal ratios, but the prognostic effect of FLC is only myeloma.14,18–20 During B cell maturation and plasma cell partially explained by translocation status. A system including development the IgH chain region undergoes switch recombi- both these risk factors allows better prediction of outcome. nation events, leading to a class switch and formation of IgG or Leukemia (2010) 24, 1498–1505; doi:10.1038/leu.2010.128; published online 3 June 2010 IgA instead of an IgM. Previous studies in patient cells and Keywords: multiple myeloma; translocations; free light chain; human myeloma cell lines have suggested that the absence of a prognosis; survival functional rearrangement in at least one of the IgH alleles is the basis of light chain myeloma.21,22 In these studies, presence of a heavy chain was associated with a functional recombination in one of the IgH loci with the other allele often being involved in a Introduction translocation. Given these, we hypothesized that the presence of an IgH translocation may be associated with compromised The monoclonal protein secreted by clonal plasma cells in production of heavy chains and lead to unbalanced, excess multiple myeloma typically is made up of an intact immuno- production of clonal light chains. In addition, we wanted to globulin consisting of heavy chains, most commonly immuno- examine whether the prognostic value of abnormal FLC ratio globulin (Ig)G or IgA, bound to a k-orl-light chain.1,2 Normal in myeloma can be explained by the presence of associated plasma cells produce mostly intact immunoglobulins with genetic abnormalities. relatively little excess free light chain. The majority of myeloma cells produces an intact immunoglobulin along with a relative excess of free light chains with an intact immunoglobulin, Materials and methods whereas a minority (15–20%) secretes only a light chain with no identifiable heavy chain; a condition termed as light chain myeloma.3 However, in the majority of patients with a heavy Patients From February 1988 to May 1992, 653 patients with previously chain, varying amounts of free light chain is present in the untreated multiple myeloma from 36 Eastern Cooperative serum, unbound to a heavy chain. The free light chain Oncology Group institutions were enrolled in the phase III (FLC) assay allows a nephelometric measurement of this free clinical trial, E9486, and its companion ancillary study, E9487, and their outcomes have been previously reported.23 Serum free Correspondence: Dr S Kumar, Division of Hematology, Mayo Clinic, light chains were run on stored sera obtained at baseline in 495 200 First Street SW, Rochester, MN 55905, USA. E-mail: [email protected] patients as part of a previous study examining the value of 11 Received 25 March 2010; accepted 29 April 2010; published online 3 disease response using free light chain levels. Among these June 2010 patients, 314 were previously investigated, using FISH, for the Immunoglobulin free light chains and IgH translocations in myeloma S Kumar et al 1499 presence or absence of IgH translocations, p53 abnormalities hybridization, validation and scoring procedures as described and deletion 13, and were included in the current analysis.21 previously by us.19 We scored 100 cells for each one of the The eligibility and treatment details have previously been abnormalities and recorded the percentage of cells with described.23 In brief, patients with previously untreated abnormal patterns (with special attention to the number of myeloma and measurable disease defined as: either as a fusions detected for the translocations). condition with serum M protein level greater than or equal to 1.0 g/100 ml; urine monoclonal light chain excretion exceeding 200 mg in 24 h; serially measurable soft tissue plasmacytomas; Statistical methods or bone marrow plasmacytosis greater than or equal to 30% For each individual type of translocation, a Wilcoxon rank sum were enrolled. Patients entering the study were stratified test was applied to assess the differences in FLC level (ratio; and according to age, creatinine, M protein type and clinical stage, difference between involved and uninvolved light chain) and randomized to one of the three study treatment regimens. between groups with and without the translocation. The levels The first regimen was VBMCP (vincristine, carmustine (bis- of FLC were also dichotomized by different cutoff points, and chloronitrosourea), melphalan, cyclophosphamide and predni- the association between the FLC groups and translocation status sone), administered in 5-week cycles. The second regimen was was assessed using Fisher’s exact test. The test was two-sided VBMCP plus recombinant alpha-2 interferon. Patients younger and the significance level was 0.05. The overall survival (OS) than 70 years were also randomized to a third regimen and progression-free survival (PFS) were examined using consisting of VBMCP and high-dose cyclophosphamide. Treat- Kaplan–Meier product limit method and the difference between ment was continued for a maximum of 2 years or until disease the groups was assessed using a logrank test. Cox proportional progression, if the latter occurred first. The baseline character- hazards model was used for best cutoff point determination. istics of the 314 patients studied here were no different from the larger cohort of patients when all relevant biological and prognostic factors are considered. Results

Are free light chain levels and ratios higher in patients Free light chain measurements with IgH translocations? The FLC assay (FREELITE, The Binding Site, Birmingham, U.K.) We first examined whether the FLC ratio or the FLC diff were was retrospectively and centrally performed on a Siemens different among patients with IgH abnormalities detected by (Siemens Healthcare Diagnostics, Deerfield, IL, USA) BNII FISH compared with those without any of these abnormalities. automated nephelometer using 0.5 ml of stored, thawed Among the 314 patients included in the study, there were 147 serum.4,6 This assay consists of two separate measurements: patients (47%) who had a translocation involving the IgH region; one to quantify k-FLC and the other to quantify l-FLC. In the distribution is shown in Table 1. The median FLC ratio and addition to reporting the k- and l-FLC, the assay report also the median FLC diff were higher among the group of patients contains the k/l FLC ratio (diagnostic range: 0.26–1.65). Out of with any IgH translocation abnormality compared to those with the 314 patients, 17 (5%) patients had normal k/l-FLC ratio none. When each of the IgH translocations were examined (0.26–1.65). If k/l ratio was 41.65, k-light chain was assigned individually, the trend was similar for all the three translocations as the involved light chain, and if the ratio was o0.26, l-light but the difference was statistically significant compared with chain was assigned as the involved light chain. The involved those with no IgH translocations only among the patients with light chain type was determined by Immunofixation (IFE) for t(14;16). Given the wide range of values for the FLC ratio and patients with a normal FLC ratio. The involved vs uninvolved FLC diff, we also examined the relationship between IgH light chain ratio (FLC ratio) was calculated, and the k/l ratio was translocations and FLC estimates using log-transformed FLC used as the involved/uninvolved ratio for patients with normal ratio and FLC diff (Figure 1). With increasing rank of FLC ratio or k/l ratio. As the FLC ratio can be affected both by the tumor FLC diff, there was an increase in the proportion of patients with burden and the degree of suppression of the uninvolved any of the three known IgH translocations; an association that immunoglobulin and the uninvolved free light chain, we also was significant at the FLC ratio cutoffs shown in the Figure 1. included the absolute difference between the involved and the In contrast, patients with an IgH abnormality but no definite uninvolved free light chain (FLC diff) in the analyses. partner chromosome identified had FLC values similar to those with no IgH abnormalities. Among the 314 patients, 47 patients (15%) had light chain myeloma, defined as the lack of a heavy FISH analysis chain on immunofixation of the serum or urine. Among the As part of the clinical trial, bone marrow research samples were patients with light chain myeloma, 57% (27/47) had an IgH collected prospectively with Institutional Review Board translocation, and among the non-light chain group, 45% (120/ approval and informed consent. Aspirate samples were enriched 267) had an IgH translocation (P ¼ 0.12, Fisher’s exact test). for mononuclear cells using the Ficoll method and cytospin slides were stored for future use (at À70 1C). Fluorescence in situ hybridization analysis was performed as previously described Is there a relationship between other genetic and the results for the entire group of patients have been abnormalities and elevated FLC? previously published. To detect t(14;16)(q32;q23), we used the We further examined whether there were differences in the FLC same 14q32 chromosome probes as previously described by values based on the presence or absence of p53 (17p-) us,19 in combination with two bacterial artificial chromosome abnormality or deletion 13 as assessed by FISH. Although there clones (356D21 and 484H2; Research Genetics, Huntsville, AL, was no correlation between the presence of p53 abnormalities USA), which localize to 16q23, and bacterial artificial chromo- and FLC measurements, patients with deletion 13 had higher some clones, 10205 and 10206, described by Chesi et al.24 To FLC ratio and FLC diff compared with patients with no test for 17p13.1, we used a locus-specific probe (LSI) p53 probe chromosome 13 abnormalities (Table 1). However, this was from Vysis (Downers Grove, IL, USA). We used standard explained by the coexistence of IgH translocations in the

Leukemia Immunoglobulin free light chains and IgH translocations in myeloma S Kumar et al 1500 Table 1 Relationship between FLC estimates and genetic abnormalities in patients with newly diagnosed myeloma

n FLC ratio Absolute FLC difference (involved/uninvolved) (involved-uninvolved)

Median (range) Pa Median (range) Pa

Overall 314 80 (0.3, 27021) 39 (0.02, 3369)

Any IgH translocation Yes 147 108 (0.3, 15200) 62 (0.1, 3369) 0.05 No 167 50 (0.3, 27021) 0.03 26 (0.4, 3019)

t(11;14) Yes 42 120 (0.9, 3110) 79 (0.04, 1978) No IgH translocation 167 50 (0.3, 27021) 0.22 25 (0.2, 3019) 0.19

t(4;14) Yes 39 104 (0.3, 15200) 63(0.02, 1869) No IgH translocation 167 50 (0.3, 27021) 0.19 25 (0.2, 3019) 0.21

t(14;16) Yes 13 714 (8.7, 10000) 244 (2.3, 3369) No IgH translocation 167 50 (0.3, 27021) 0.001 25(0.2, 3019) 0.04

Other 14q32 Yes 53 80 (0.8, 7870) 0.55 39 (0.04, 2399) 0.29 No IgH translocation 167 50 (0.3, 27021) 25 (0.2, 3019)

P53 mutation Yes 8 421 (2.2, 27021) 0.48 75 (0.8, 1869) 0.84 No 306 78 (0.3, 17400) 39 (0.02, 3369)

Del Chrom13 Yes 157 108 (0.3, 27021) 0.03 62 (0.02, 2399) 0.07 No 157 50 (0.3, 15200) 25 (0.04, 3369) Abbreviations: FLC, free light chain; IgH, immunoglobulin heavy chain. aWilcoxon rank sum test. Bold values indicate statistically signiﬁcant P values.

Figure 1 Distribution of free light chain (FLC) ratio (involved vs uninvolved ratio) and FLC diff (absolute difference between involved and uninvolved) among patients. Solid squares represent patients with t(4;14), t(14;16) or t(11;14) or other 14q32 translocation; open circles represent patients without t(4;14), t(14;16), t(11;14) and any other 14q32 translocations. The horizontal dashed lines refer to FLC ratio original values of 100 and 1000, and vertical dashed lines refer to FLC difference original values of 10 and 100. Solid line indicates signiﬁcant association (Pp0.05) between the dichotomized FLC groups and translocation status.

Leukemia Immunoglobulin free light chains and IgH translocations in myeloma S Kumar et al 1501 majority of these patients, as the values were not very different and OS relative to the presence of translocations (Table 3).We for patients with chromosome 13 abnormalities with out an then examined the outcome among patients grouped according associated IgH translocation compared with those with no to whether they had one or more of the abnormalities; neither chromosome 13 abnormalities (P ¼ 0.67 for FLC diff; P ¼ 0.51 FISH abnormality nor FLC abnormality; either one of the for FLC ratio). In addition, we also noticed a significant abnormalities; or both. The presence of either one of the association between the type of involved light chain and abnormalities (FLC diff 4185 or one of the two translocations) presence of IgH translocations, with overrepresentation of has a negative impact on the outcome, both PFS and OS l-light chain in that group (P ¼ 0.006). (Figure 3). More importantly, presence of both abnormalities resulted in a much inferior outcome (PFS and OS) compared with having neither one of the abnormalities (Figures 3a and b). Can the prognostic value of FLC in multiple myeloma be The median OS for the three groups were 3.97, 2.19 and 1.74 explained by concurrent presence of high-risk IgH years, respectively (Po0.0001) in the presence of none, either translocations? one or both risk factors (FLC and one of the translocations). Given that previous studies show the adverse prognostic impact These findings were similar when the FLC ratio was used instead of abnormal FLC estimates in myeloma, we examined whether it of FLC diff (Figures 3c and d). can be explained on the basis of simultaneous presence of high- risk IgH translocation abnormalities. First, we examined the relationship of FLC diff and FLC ratio with PFS and OS. As both Discussion the values have a very wide range, we first log10-transformed both FLC diff and FLC ratio, and used this as a continuous The humoral immune system is an important component of the variable for examining their effect on PFS and OS. As shown in body’s defense and consists of terminally differentiated plasma Table 2, both FLC diff and FLC ratio were prognostic for PFS and cells secreting antibodies with specificity for a variety of OS. To identify optimal cutoff points for FLC diff and FLC ratio antigens. The normal development of plasma cells from the B (using actual values, not log-transformed) for survival analysis, cells systematically provides the opportunity for development of we used an outcome-oriented method, that is, maximizing the diversity, both in terms of the spectrum of antigens the log-likelihood value using Cox proportional hazards model in a antibodies can respond to and also in terms of the defense univariate manner. For the FLC diff, 185 was considered as the mechanisms it can bring to bear by virtue of the different classes best cutoff point for both PFS and OS, and for the FLC ratio, 277 of antibodies it can generate.25,26 The pathogenesis of plasma was determined to be the best cutoff. (Table 2, Figures 2 a–d). cell disorders is intricately intertwined with the normal B cell The prognostic value of IgH translocations among the patients development. During the normal development of plasma cells in this trial has been previously reported and was further from the early-stage B cells, the genes encoding for the IgH and confirmed within this subset. As previously demonstrated, light chains undergo a series of genetic modifications, including presence of t(4;14) and t(14;16) was associated with inferior the VDJ recombination that allows random segments of the V outcomes compared to patients without any IgH translocations, (variable), D (diversity) and J (joining) regions to come together whereas those with t(11;14) and other 14q32 abnormalities had to form a functional recombination. This is followed by somatic outcomes comparable with those without translocations (data hypermutation that generates point mutations and consequently not shown). diversity in the variable region and class switch recombination In a multivariate analysis, we examined whether the prog- involving the constant region that allow generation of specific nostic values seen with FLC diff and FLC ratio were independent types of heavy chains.16,27 Although the primary heavy chain of the presence of IgH translocations t(4:14) and t(14;16), which produced by the B cell is an IgM, and production of IgD can are associated with a worse outcome. The impact of these result from alternate splicing/termination, the production of an translocations on outcome in this dataset was similar to that IgA, IgG or IgE requires the class switch recombination of the previously reported (data not shown). The presence of t(4;14) or heavy chain gene. t(14;16) correlated with FLC diff, with 13% of those with FLC diff Normal immunoglobulin production and secretion by plasma p185 and 27% of those with FLC diff 4185 having the two cells, however, require a balanced production of IgH and light translocations (P ¼ 0.008). Using this cutoff for grouping, the chains. Given the complex process of genetic rearrangements prognostic value of the FLC diff on PFS and OS seems to that underlies the normal plasma cell development process, it is be independent of these high-risk IgH translocations not surprising that errors, which can potentially have patholo- (P-value ¼ 0.03 and 0.003, respectively, for PFS and OS; gical consequences, can occur. The normal counterpart for the Table 3). Similar results were also obtained when FLC ratio clonal cells in myeloma represent the terminally differentiated was used in place of FLC diff, in terms of its association with plasma cell, as the these cells typically have undergone somatic presence of t(4:14) and t(14;16), as well as its effect on the PFS hypermutation and class switch recombination; both hallmarks

Table 2 Impact of FLC diff and FLC ratio on progression-free and overall survival

Prognostic factor Progression-free survival Overall survival

Hazard ratio (95% CI) P-value Hazard ratio (95% CI) P-value

FLC diff (log) 1.2 (1.06, 1.36) 0.0039 1.23 (1.09, 1.39) 0.0009 FLC diff 4185 vs FLC diff p185 1.51 (1.15, 1.98) 0.003 1.61 (1.24, 2.09) 0.0004 FLC ratio (log) 1.23 (1.10, 1.39) 0.0005 1.21 (1.08, 1.36) 0.0012 FLC ratio 4277 vs FLC ratio p277 1.57 (1.22, 2.02) 0.0005 1.53 (1.20, 1.96) 0.0007 Abbreviations: CI, conﬁdence interval; FLC, free light chain.

Leukemia Immunoglobulin free light chains and IgH translocations in myeloma S Kumar et al 1502

Figure 2 Kaplan–Meier curves demonstrating comparison of progression-free survival based on free light chain (FLC) estimates; FLC difference 4185 vs o ¼ 185 (a); overall survival based on FLC estimates; FLC difference 4185 vs o ¼ 185 (b); progression-free survival based on FLC estimates; FLC ratio4277 vs o ¼ 277 (c) and overall survival based on FLC estimates; FLC ratio4277 vs o ¼ 277 (d).

Table 3 Impact of translocation status and FLC estimates on the progression and overall survival

Prognostic factor Progression-free survival Overall survival

Hazard ratio (95% CI) P-value Hazard ratio (95% CI) P-value

Cox model for FLC ratio FLC ratio Inv/uninv4277 vs 1.48 (1.14, 1.91) 0.0028 2.09 (1.53, 2.84) 0.0023 Inv/uninvp277 t(4;14) or t(14;16) Yes vs no 2.13 (1.55, 2.92) o0.0001 1.47 (1.15, 1.89) o0.0001

Cox model for FLC difference at FLC diff Inv/uninv4185 vs 1.36 (1.03, 1.79) 0.032 1.49 (1.15, 1.95) 0.003 Inv/uninvp185 t(4;14) or t(14;16) Yes vs no 2.10 (1.52, 2.90) o0.0001 2.03(1.49, 2.77) o0.0001 Abbreviations: CI, conﬁdence interval; FLC, free light chain.

of post germinal center B cells.28 Several lines of evidence exists to be secreted alone in the absence of an accompanying heavy to suggest that unbalanced production of the heavy or light chain.33,34 Such an absence of heavy chain can potentially chains can lead to the lack of intact immunoglobulin molecules result from several mechanisms, including lack of a functional and preferential secretion of the heavy or light chains.29 rearrangement of the heavy chain, mutations involving the Although excess of heavy or light chain can occur depending heavy chain gene resulting in early termination of transcription, on the affected component, this seems to affect the heavy chain secondary VDJ rearrangements, instability of the heavy chain less commonly.30 Although there are likely to be several reasons mRNA, or inability of the cell to secrete the heavy chain. for this observation, including inability of the endoplasmic Light chain myeloma, constituting 15–20% of all myelomas is reticulum to secrete the heavy chain that is unbound to a light characterized by the absence of a detectable heavy chain in the chain leading to an unfolded protein response and intracellular serum or urine. Studies suggest that this ﬁnding is likely to result degradation of the heavy chain through a proteasome mediated from the lack of a functional rearrangement in the heavy chain pathway, as well as toxicity of non-secreted full-size heavy gene.21,22,35 Typically, only one of the alleles undergoes chain.29,31,32 Light chains unbound to a heavy chain seem less functional rearrangement in any given plasma cell. Szczepanski susceptible to such degradation mechanisms and are more likely et al22 studied 12 patients with light chain myeloma, and

Leukemia Immunoglobulin free light chains and IgH translocations in myeloma S Kumar et al 1503

Figure 3 Kaplan–Meier curves demonstrating comparison of progression-free survival based on FLC estimates (FLC difference 4185 vs o ¼ 185) and/or the presence or absence of the translocations t(4;14) or t(14;16) (a); overall survival based on FLC estimates (FLC difference 4185 vs o ¼ 185) and/or the presence or absence of the translocations t(4;14) or t(14;16) (b); progression-free survival based on FLC estimates (FLC ratio4277 vs o ¼ 277) and/or the presence or absence of the translocations t(4;14) or t(14;16) (c); and overall survival based on FLC estimates (FLC ratio4277 vs o ¼ 277) and/or the presence or absence of the translocations t(4;14) or t(14;16) (d). observed monoallelic J(H) gene rearrangements in 10 patients, are clearly higher among the patients with very high absolute biallelic rearrangement in one patient, and biallelic deletion of levels of involved free light chain, and as expected in those with the JH and Cm regions in one patient. The authors concluded that a high ratio for the involved to uninvolved free light chain. in many of the light chain myeloma patients, illegitimate IgH Although involved-to-uninvolved FLC ratio can be due to high class switch rearrangement or illegitimate deletion of the levels of the involved FLC or suppression the uninvolved FLC, functional VDJ allele is responsible for the failure of heavy Figure 2 suggests that most of the association with presence of chain secretion. Magrangeas et al,21 in an another study on translocations is due to the elevation of the abnormal FLC, as patients with light chain myeloma and myeloma cell lines, using very few of the translocated patients are seen in the upper left or FISH, demonstrated that lack of heavy chain production was a lower right quadrants. It is not clear how translocation involving direct result of the absence of functional rearrangement on one a heavy chain locus would lead to an elevation in the free light of the alleles, while the other have undergone a translocation. In chain excretion; however, several hypotheses can be raised. It is comparison, in patients with non-light chain myeloma with IgH unlikely that this results from a translocation that occurs on the translocations, one of the heavy chain genes remains functional, functionally rearranged heavy chain locus, as that would have whereas the other has undergone translocation. Translocations most likely led to the complete disruption of the heavy chain involving the IgH gene is observed in over half of all patients production and consequent light chain myeloma. The molecular with multiple myeloma, whereas the other half of the patients analysis of the IgH translocations suggests that this mostly occurs usually have trisomies of odd-numbered chromosomes, leading on the non-productive IgH allele. It is possible that the presence to a hyperdiploid clone.14,15,20,36,37 As is typically seen, only of a translocation is an indicator of genomic instability in the 15% of our study population had light chain disease and the clonal myeloma cells that can potentially lead to somatic presence of an IgH translocation was not signiﬁcantly higher in mutations or other processes inﬂuencing the functionally rear- this group compared with common myeloma. This is in ranged allele, leading to decreased production of the heavy agreement with the previous reports showing no association chain. Moreover, the lack of a complete concordance between between light chain myeloma and presence of IgH transloca- the presence of a translocation and the elevation of the FLC also tions.38 In the original publications, we found t(11;14)(q13;q32) point toward this being due to the cumulative effect of several associated with light chain-l myeloma. In this study, we events rather than any single abnormality. demonstrate an association between the presence of IgH The presence of IgH translocations, especially t(4;14) and translocations and elevated free light chains and extreme light t(14;16), have been associated with poor outcome after chain ratios. The proportion of patients with these translocations conventional or high-dose therapies.18,19,39–41 In this study,

Leukemia Immunoglobulin free light chains and IgH translocations in myeloma S Kumar et al 1504 we sought to answer the question whether the prognostic effect 3 Kyle RA, Gertz MA, Witzig TE, Lust JA, Lacy MQ, Dispenzieri A of elevated free light chain in myeloma and other plasma cell et al. Review of 1027 patients with newly diagnosed multiple disorders can be explained by the presence of high-risk IgH myeloma. Mayo Clin Proc 2003; 78: 21–33. translocations. Although the group of patients with elevated FLC 4 Bradwell AR, Carr-Smith HD, Mead GP, Tang LX, Showell PJ, Drayson MT et al. Highly sensitive, automated immunoassay for level and ratio clearly were more likely to carry the high-risk IgH immunoglobulin free light chains in serum and urine. Clin Chem translocations, the prognostic effect of FLC was independent of 2001; 47: 673–680. the translocation abnormality. More importantly, we could 5 Katzmann JA, Abraham RS, Dispenzieri A, Lust JA, Kyle RA. combine the two markers to develop a better risk-stratification Diagnostic performance of quantitative kappa and lambda free light system allowing better estimates of outcome among these chain assays in clinical practice. Clin Chem 2005; 51: 878–881. patients. One could speculate that the prognostic value of FLC 6 Katzmann JA, Clark RJ, Abraham RS, Bryant S, Lymp JF, Bradwell AR et al. Serum reference intervals and diagnostic ranges for free seen in monoclonal gammopathy of undetermined significance kappa and free lambda immunoglobulin light chains: relative and in Smoldering Multiple Myeloma (SMM) may also partially sensitivity for detection of monoclonal light chains. Clin Chem result from the enrichment of the high-risk group for these 2002; 48: 1437–1444. genetic abnormalities. However, mechanisms behind the 7 Rajkumar SV, Kyle RA, Therneau TM, Clark RJ, Bradwell AR, independent effect of FLC on the outcome of patients with Melton III LJ et al. Presence of monoclonal free light chains in the plasma cell disorders remains unanswered. It has been serum predicts risk of progression in monoclonal gammopathy of undetermined significance. Br J Haematol 2004; 127: 308–310. suggested that the heavy chain, after proteasomal degradation 8 Dispenzieri A, Kyle RA, Katzmann JA, Therneau TM, Larson D, in the cell, may be presented on the cell surface as a potential Benson J et al. Immunoglobulin free light chain ratio is an antigen for the development of an immune response, which may independent risk factor for progression of smoldering (asympto- keep the clonal population under check.42,43 The progressive matic) multiple myeloma. Blood 2008; 111: 785–789. acquisition of somatic mutations and other genetic recombina- 9 Dingli D, Kyle RA, Rajkumar SV, Nowakowski GS, Larson DR, tion events in the malignant plasma cell, may eventually lead to Bida JP et al. Immunoglobulin free light chains and solitary decreased production of the heavy chain and escape from the plasmacytoma of bone. Blood 2006; 108: 1979–1983. 10 Dispenzieri A, Lacy MQ, Katzmann JA, Rajkumar SV, Abraham RS, immune surveillance, as well as ‘light chain escape’. Hayman SR et al. Absolute values of immunoglobulin free light In conclusion, elevated free light chain levels are associated chains are prognostic in patients with primary systemic amyloi- with the presence of IgH translocations and these patients are dosis undergoing peripheral blood stem cell transplantation. Blood more likely to harbor the high-risk genetic abnormalities. Both 2006; 107: 3378–3383. the free light chain estimates and the results of the FISH testing 11 Dispenzieri A, Zhang L, Katzmann JA, Snyder M, Blood E, Degoey contribute to the risk stratification in patients with newly R et al. Appraisal of immunoglobulin free light chain as a marker of response. Blood 2008; 111: 4908–4915. diagnosed myeloma. Routine FISH testing and free light chain 12 Kyrtsonis MC, Vassilakopoulos TP, Kafasi N, Sachanas S, Tzenou estimation for patients with newly diagnosed myeloma will T, Papadogiannis A et al. Prognostic value of serum free light chain allow us to confirm tests and allow better risk stratification of the ratio at diagnosis in multiple myeloma. Br J Haematol 2007; 137: patients. Additional research needs to be carried out to help us 240–243. better understand the molecular basis for unbalanced light chain 13 van Rhee F, Bolejack V, Hollmig K, Pineda-Roman M, Anaissie E, excretion by myeloma cells and the current finding of the Epstein J et al. High serum-free light chain levels and their association with IgH translocation abnormalities should form rapid reduction in response to therapy define an aggressive multiple myeloma subtype with poor prognosis. Blood 2007; the basis for this research. 110: 827–832. 14 Fonseca R, Barlogie B, Bataille R, Bastard C, Bergsagel PL, Chesi M et al. Genetics and cytogenetics of multiple myeloma: a workshop Conflict of interest report. Cancer Res 2004; 64: 1546–1558. 15 Chng WJ, Glebov O, Bergsagel PL, Kuehl WM. Genetic events in SK, AD, RF, LZ, EB, MS, RD, KH, SV, RAK, MO, PRG declare no the pathogenesis of multiple myeloma. Best Pract Res Clin conflict of interest. ARB is an employee of the Binding Site. JAK Haematol 2007; 20: 571–596. receives reagents from the Binding Site. 16 Gonzalez D, van der Burg M, Garcia-Sanz R, Fenton JA, Langerak AW, Gonzalez M et al. Immunoglobulin gene rearrangements and the pathogenesis of multiple myeloma. Blood 2007; 110: 3112–3121. 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