A novel PDK1 inhibitor, JX06, inhibits glycolysis and induces apoptosis in multiple myeloma cells.

Pyruvate dehydrogenase kinase 1 (PDK1) is a Ser/Thr kinase that inactivates mitochondrial pyruvate dehydrogenase (PDH), leading to switch of glucose metabolism from mitochondrial oxidation to aerobic glycolysis. We previously reported that PDK1 inhibition is a potent therapeutic strategy in multiple myeloma (MM). However, availability of PDK1 inhibitors, which are effective at low concentrations, are limited at present, making PDK1 inhibition difficult to apply in the clinic. In the present study, we examined the efficacy and mechanism of action of JX06, a novel PDK1 inhibitor, against MM cells. We confirmed that PDK1 is highly expressed in normal plasma cells and MM cells using publicly available gene expression datasets. JX06 suppressed cell growth and induced apoptosis against MM cells from approximately 0.5 µM JX06 treatment reduced PDH phosphorylation, suggesting that JX06 is indeed inhibiting PDK1. Intracellular metabolite analysis revealed that JX06 treatment reduced metabolites associated with glucose metabolism of MM cells. Additionally, JX06 in combination with a well-known proteasome inhibitor, bortezomib, significantly increased MM cell death, which raises the possibility of combination use of JX06 with proteasome inhibitors in the clinic. These findings demonstrate that PDK1 can be potentially targeted by JX06 in MM through glycolysis inhibition, leading to a novel therapeutic strategy in MM.

Novel p97/VCP inhibitor induces endoplasmic reticulum stress and apoptosis in both bortezomib-sensitive and -resistant multiple myeloma cells.

p97/VCP is an endoplasmic reticulum (ER)-associated protein that belongs to the AAA (ATPases associated with diverse cellular activities) ATPase family. It has a variety of cellular functions including ER-associated protein degradation, autophagy, and aggresome formation. Recent studies have shown emerging roles of p97/VCP and its potential as a therapeutic target in several cancer subtypes including multiple myeloma (MM). We conducted a cell-based compound screen to exploit novel small compounds that have cytotoxic activity in myeloma cells. Among approximately 2000 compounds, OSSL_325096 showed relatively strong antiproliferative activity in MM cell lines (IC50 , 100-500 nmol/L). OSSL_325096 induced apoptosis in myeloma cell lines, including a bortezomib-resistant cell line and primary myeloma cells purified from patients. Accumulation of poly-ubiquitinated proteins, PERK, CHOP, and IREα, was observed in MM cell lines treated with OSSL_325096, suggesting that it induces ER stress in MM cells. OSSL_325096 has a similar chemical structure to DBeQ, a known p97/VCP inhibitor. Knockdown of the gene encoding p97/VCP induced apoptosis in myeloma cells, accompanied by accumulation of poly-ubiquitinated protein. IC50 of OSSL_325096 to myeloma cell lines were found to be lower (0.1-0.8 µmol/L) than those of DBeQ (2-5 µmol/L). In silico protein-drug-binding simulation suggested possible binding of OSSL_325096 to the ATP binding site in the D2 domain of p97/VCP. In cell-free ATPase assays, OSSL_325096 showed dose-dependent inhibition of p97/VCP ATPase activity. Finally, OSSL_325096 inhibited the growth of subcutaneous myeloma cell tumors in vivo. The present data suggest that OSSL_325096 exerts anti-myeloma activity, at least in part through p97/VCP inhibition.

[Spontaneous remission of acquired factor XIII inhibitor concurrent to development of IgA-λ type multiple myeloma].

Coagulation factor XIII is a fibrin-stabilizing factor that leads to the crosslinking of fibrin when activated by thrombin. Acquired factor XIII inhibitor is caused when antibodies are generated against factor XIII, reducing its activity. Here we report a case of acquired factor XIII inhibitor. Although prednisolone was administered, factor XIII activity was not recovered. Interestingly, the activity normalized following the onset of multiple myeloma. The presence of inhibitors was evaluated in the patient's plasma by absorption tests and enzyme-linked immunosorbent assay. Immunoglobulin G inhibitors of factor XIII were present at admission, but later decreased with the onset of the IgA-λ-type myeloma. Thus, it is possible that the level of factor XIII inhibitors and polyclonal immunoglobulins could have been suppressed by the progression of myeloma, resulting in the normalization of factor XIII activity.

MUC1/KL-6 expression confers an aggressive phenotype upon myeloma cells.

The sialic glycoprotein, MUC1, is known to be involved in the pathogenesis of various types of cancers. KL-6 is one of the surface antigens of MUC1 and also a marker of interstitial pneumonitis. A fraction of patients with myeloma (3.9%) have elevated serum KL-6 levels without any evidence of interstitial pneumonitis and their myeloma cells have high MUC1 expression. We established a myeloma cell line designated EMM1 from a patient with multiple myeloma accompanied with elevated serum KL-6. EMM1 cells expressed high levels of MUC1 compared with other myeloma cell lines. Knockdown of MUC1 in EMM1 cells induced cell cycle arrest during S phase and apoptosis, suggesting that the MUC1 expression is involved in accelerated growth of EMM1 cells. RNA-seq analysis suggests that MUC1 expression activates k-ras and TNFα-induced NFκB pathways in EMM1 cells. We injected EMM1 cells subcutaneously into Rag2-/-Jak3-/- Balb/c mice to establish a mouse xenograft model. These mice had aggressive tumor growth that was accompanied by high serum KL-6 levels. In addition, MUC1 knockdown in EMM1 cells led to inhibited tumor growth. These findings demonstrate that MUC1 serves as a potential target for developing drugs for treatment of patients with KL-6+ myeloma, and EMM1 cells and EMM1-engrafted mice are useful tools for the development of such novel agents.

Unsuppressed serum albumin levels may jeopardize the clinical relevance of the international staging system to patients with light chain myeloma.

The international staging system (ISS) is the most commonly used risk-stratification system for patients with multiple myeloma (MM) and is determined by serum albumin and ß2-microglobulin levels. In the two determinants, ß2-microglobulin levels are frequently observed to be elevated in patients with myeloma, particularly in those with renal impairment. In comparison with patients with intact immunoglobulin myeloma, patients with LC myeloma do not necessarily show decreased levels of serum albumin. The clinical impact of ISS in patients with LCMM, in particular the distinction between ISS I and II, may be complicated due to non-decreased levels of serum albumin in both stages. Accordingly, we have attempted to assess clinical relevance of the ISS in patients with LC myeloma. The clinical data of 1899 patients with MM diagnosed between January 2001 and December 2012 were collected from 38 affiliated hospitals of the Japanese Society of Myeloma. Significant difference was not found between stage I (n = 72) and stage II (n = 92) in LC myeloma patients (n = 307). The mean serum albumin concentration of patients with LC myeloma was within the reference range but higher than that of patients with IgG + IgA myeloma (n = 1501), which complicates the distinction between ISS stage I and II myeloma. Patients with LC myeloma had low frequencies of t(4; 14) and high frequency of elevated lactate dehydrogenase, and despite a relevant amount of missing data in our registry (R-ISS stage I; n = 11, stage II; n = 32, and stage III: n = 18), the information included in the R-ISS scoring system seems to be more accurate than ISS to obtain a reliable risk stratification approach in non-ISS stage III LC myeloma patients.

A xenograft model reveals that PU.1 functions as a tumor suppressor for multiple myeloma in vivo.

We previously demonstrated that PU.1 expression is down-regulated in the majority of myeloma cell lines and primary myeloma cells from patients. We introduced the tet-off system into the human myeloma cell lines U266 and KMS12PE that conditionally express PU.1 and demonstrated that PU.1 induces cell cycle arrest and apoptosis in myeloma cells in vitro. Here, we established a mouse xenograft model of myeloma using these cell lines to analyze the effects of PU.1 on the phenotype of myeloma cells in vivo. When doxycycline was added to the drinking water of mice engrafted with these myeloma cells, all mice had continuous growth of subcutaneous tumors and could not survived more than 65 days. In contrast, mice that were not exposed to doxycycline did not develop subcutaneous tumors and survived for at least 100 days. We next generated mice engrafted with subcutaneous tumors 5-10 mm in diameter that were induced by exposure to doxycycline. Half of the mice stopped taking doxycycline-containing water, whereas the other half kept taking the water. Although the tumors in the mice taking doxycycline continued to grow, tumor growth in the mice not taking doxycycline was significantly suppressed. The myeloma cells in the tumors of the mice not taking doxycycline expressed PU.1 and TRAIL and many of such cells were apoptotic. Moreover, the expression of a cell proliferation marker Ki67 was significantly decreased in tumors from the mice not taking doxycycline, compared with that of tumors from the mice continuously taking doxycycline. The present data strongly suggest that PU.1 functions as a tumor suppressor of myeloma cells in vivo.

Identification and Assessment of Cardiac Amyloidosis by Myocardial Strain Analysis of Cardiac Magnetic Resonance Imaging.

BACKGROUND: We explored the usefulness of myocardial strain analysis on cardiac magnetic resonance imaging (CMR) scans for the identification of cardiac amyloidosis.Methods and Results:The 61 patients with systemic amyloidosis underwent 3.0-T CMR, including CMR tagging and late-gadolinium enhanced (LGE) imaging. The circumferential strain (CS) of LGE-positive and LGE-negative patients was measured on midventricular short-axis images and compared. Logistic regression modeling of CMR parameters was performed to detect patients with LGE-positive cardiac amyloidosis. Of the 61 patients with systemic amyloidosis 48 were LGE-positive and 13 were LGE-negative. The peak CS was significantly lower in the LGE-positive than in the LGE-negative patients (-9.5±2.3 vs. -13.3±1.4%, P<0.01). The variability in the peak CS time was significantly greater in the LGE-positive than in the LGE-negative patients (46.1±24.5 vs. 21.2±20.1 ms, P<0.01). The peak CS significantly correlated with clinical biomarkers. The sensitivity, specificity, and accuracy of the diagnostic model using CS parameters for the identification of LGE-positive amyloidosis were 93.8%, 76.9%, and 90.2%, respectively. CONCLUSIONS: Myocardial strain analysis by CMR helped detect LGE-positive amyloidosis without the need for contrast medium. The peak CS and variability in the peak CS time may correlate with the severity of cardiac amyloid deposition and may be more sensitive than LGE imaging for the detection of early cardiac disease in patients with amyloidosis.

Analysis of deposited peptides in amyloid lesions of AL amyloidosis by mass spectrometry.

Although immunoglobulin light chain (LC) plays a critical role in AL amyloidosis, detailed characteristics of deposited LC are not well known. In this study, LC peptides were analyzed by a combination of laser microdissection, liquid chromatography, and mass spectrometry (LC-MS/MS) in 65 patients with AL amyloidosis. Constant regions of LC were detected in all patients. Kappa- or lambda-types were detected in 20 and 45 patients, respectively. Various types of constant regions of LC were found; however, IGLC3 and IGKC4 were the most frequently detected. Besides LC, apolipoproteins and vitronectin were repeatedly found in amyloid lesions. These results suggest marked heterogeneity in terms of subtype of constant regions of LC in amyloid lesions. Immunohistochemistry identified LC in approximately half of patients in whom LC was detected by LC-MS/MS. This finding indicates superiority of LC-MS/MS over IHC for the detection of LC.

Immunomodulatory drugs act as inhibitors of DNA methyltransferases and induce PU.1 up-regulation in myeloma cells.

Immunomodulatory drugs (IMiDs) such as thalidomide, lenalidomide, and pomalidomide are efficacious in the treatment of multiple myeloma and significantly prolong their survival. However, the mechanisms of such effects of IMiDs have not been fully elucidated. Recently, cereblon has been identified as a target binding protein of thalidomide. Lenalidomide-resistant myeloma cell lines often lose the expression of cereblon, suggesting that IMiDs act as an anti-myeloma agent through interacting with cereblon. Cereblon binds to damaged DNA-binding protein and functions as a ubiquitin ligase, inducing degradation of IKZF1 and IKZF3 that are essential transcription factors for B and T cell development. Degradation of both IKZF1 and IKZF3 reportedly suppresses myeloma cell growth. Here, we found that IMiDs act as inhibitors of DNA methyltransferases (DMNTs). We previously reported that PU.1, which is an ETS family transcription factor and essential for myeloid and lymphoid development, functions as a tumor suppressor in myeloma cells. PU.1 induces growth arrest and apoptosis of myeloma cell lines. In this study, we found that low-dose lenalidomide and pomalidomide up-regulate PU.1 expression through inducing demethylation of the PU.1 promoter. In addition, IMiDs inhibited DNMT1, DNMT3a, and DNMT3b activities in vitro. Furthermore, lenalidomide and pomalidomide decreased the methylation status of the whole genome in myeloma cells. Collectively, IMiDs exert demethylation activity through inhibiting DNMT1, 3a, and 3b, and up-regulating PU.1 expression, which may be one of the mechanisms of the anti-myeloma activity of IMiDs.

Reduced frequency treatment with bortezomib plus dexamethasone for elderly patients with relapsed and/or refractory multiple myeloma: a phase 2 study of the Japanese Myeloma Study Group (JMSG-0902).

Bortezomib is one of the most widely used novel drugs for the treatment of multiple myeloma (MM). However, twice-weekly intravenous administration is associated with innegligible adverse events and treatment discontinuation. We therefore evaluated the long-term efficacy and feasibility of reduced frequency treatment with intravenous bortezomib in elderly patients with relapsed and/or refractory MM. A total of 47 bortezomib-naïve patients (median age 75 years) received bortezomib (1.3 mg/m(2), intravenously) and dexamethasone (20 mg) on days 1, 8, and 15 of every 4-week cycle. Twenty-six patients completed the planned 8 cycles. Best responses were stringent complete response (sCR) in 5 patients, very good partial response (VGPR) in 3, PR in 15, stable disease (SD) in 18, and disease progression (PD) in 6, respectively. Median progression-free and overall survivals were 9.6 and 35.1 months, respectively. After progression, 11 patients were retreated with bortezomib-based regimens and another 24 patients with immunomodulatory drugs. Multivariate analysis revealed that ISS 3, t(4;14), and <4 therapy cycles were significantly poor prognostic factors and that subsequent therapy with bortezomib-based regimens was a favorable factor for extended OS. The common adverse events were diarrhea, constipation, and peripheral neuropathy with no grade 4 toxicity. In conclusion, reduced frequency treatment with intravenous bortezomib + dexamethasone is an effective option for elderly patients with MM.

Phylogenetics of family Enterobacteriaceae and proposal to reclassify Escherichia hermannii and Salmonella subterranea as Atlantibacter hermannii and Atlantibacter subterranea gen. nov., comb. nov.

Multilocus sequence analysis based on hypervariable housekeeping proteins was utilized to differentiate closely related species in the family Enterobacteriaceae. Of 150 housekeeping proteins, the top 10 hypervariable proteins were selected and concatenated to obtain distance data. Distances between concatenated proteins within the family were 0.9-41.2%, whereas the 16S rRNA and atpD-gyrB-infB-rpoB concatenated sequence (4MLSA) distances were 0.8-6.0% and 0.9-22.1%, respectively. These data indicate that phylogenetic analysis by concatenation of hypervariable proteins is a powerful tool for discriminating species in the family Enterobacteriaceae. To confirm the discriminatory power of the 10 chosen concatenated hypervariable proteins (C10HKP), phylogenetic trees based on C10HKP, 4MLSA, and the 16S rRNA gene were constructed. Comparison of average bootstrap values among C10HKP, 4MLSA and 16S rRNA genes indicated that the C10HKP tree was the most reliable. Location via the C10HKP tree was consistent with existing assignments for almost all species in the family Enterobacteriaceae. However, the C10HKP tree suggested that several species (including Enterobacter massiliensis, Escherichia vulneris, Escherichia hermannii, and Salmonella subterranea) should be reassigned to different clusters than those defined in previous analyses. Furthermore, E. hermannii and S. subterranea appeared to fall onto a branch independent from those occupied by the other Enterobacteriaceae. Therefore, we propose Atlantibacter gen. nov., such that E. hermannii and S. subterranea would be transferred to genus Atlantibacter as Atlantibacter hermannii, comb. nov. and Atlantibacter subterranea. comb. nov., respectively.

Transcriptional dysregulation of the deleted in colorectal carcinoma gene in multiple myeloma and monoclonal gammopathy of undetermined significance.

The deleted in colorectal carcinoma (DCC) gene at 18q21 encodes a netrin-1 receptor, a tumor suppressor that prevents cell growth. While allele loss or decreased expression of DCC has been associated with the progression of solid tumors and hematologic malignancies, including leukemias and malignant lymphomas, its involvement has not been evaluated in multiple myeloma (MM), a plasma cell malignancy characterized by complex and heterogenous molecular abnormalities. We here show that 10 of 11 human myeloma-derived cell lines (HMCLs) expressed non-translated aberrant DCC transcriptional variants, in which exon 2 fuses with intron 1 instead of exon 1 (mt.DCC). Among them, two co-expressed wild type transcripts (wt.DCC), while eight co-expressed the splicing variant (sv.DCC) lacking exon 1. The remaining HMCL expressed only sv.DCC. In addition, analyses revealed that there were two types of mt.DCC that differed in their fusion of intron 1 with exon 2. In patient-derived samples from 30 MM and 8 monoclonal gammopathy of undetermined significance (MGUS) patients, wt.DCC was expressed in 53% of MM, but not in MGUS, while 23% of MM and 75% of MGUS expressed only sv.DCC. Considering that 25% of MGUS, 57% of MM, and 91% HMCLs expressed mt.DCC, our results suggest that the acquisition of mt.DCC might be a secondary genetic change in plasma cell dyscrasia.

PU.1 is a potent tumor suppressor in classical Hodgkin lymphoma cells.

PU.1 has previously been shown to be down-regulated in classical Hodgkin lymphoma (cHL) cells via promoter methylation. We performed bisulfite sequencing and proved that the promoter region and the -17 kb upstream regulatory element of the PU.1 gene were highly methylated. To evaluate whether down-regulation of PU.1 is essential for the growth of cHL cells, we conditionally expressed PU.1 in 2 cHL cell lines, L428 and KM-H2. Overexpression of PU.1 induced complete growth arrest and apoptosis in both cell lines. Furthermore, in a Hodgkin lymphoma tumor xenograft model using L428 and KM-H2 cell lines, overexpression of PU.1 led to tumor regression or stable disease. Lentiviral transduction of PU.1 into primary cHL cells also induced apoptosis. DNA microarray analysis revealed that among genes related to cell cycle and apoptosis, p21 (CDKN1A) was highly up-regulated in L428 cells after PU.1 induction. Stable knockdown of p21 rescued PU.1-induced growth arrest in L428 cells, suggesting that the growth arrest and apoptosis observed are at least partially dependent on p21 up-regulation. These data strongly suggest that PU.1 is a potent tumor suppressor in cHL and that induction of PU.1 with demethylation agents and/or histone deacetylase inhibitors is worth exploring as a possible therapeutic option for patients with cHL.

[Diagnostic criteria of multiple myeloma].

Multiple myeloma is a disease showing heterogeneous symptoms and varieties of laboratory findings. Although there have been many efforts trying to diagnose this disease in a simple way, no simple criteria was available until International Myeloma Working Group (IMWG) criteria has proposed. In this review, detailed IMWG criteria for diagnosis of multiple myeloma are described.

Complete remission achieved in a multiple myeloma patient with elevated serum KL-6 level by a combination regimen with bortezomib, cyclophosphamide, and dexamethasone.

A 79-year-old woman suffering from double vision after a 4-year history of MGUS was referred to our hospital. MRI revealed that she had three intracranial plasmacytoma masses and one spinal plasmacytoma mass. Bone marrow aspirates showed 52.4% plasma cell infiltration and immunoelectrophoresis identified serum IgG-M protein, leading to a diagnosis of IgG-type multiple myeloma. IgG was elevated to 3,355 mg/dl and urine type Bence-Jones protein was positive. KL-6, a membrane-bound glycoprotein encoded by Mucin 1 and a marker of interstitial pneumonia, was also elevated to 1,409 mg/dl, but computed tomography of the lungs revealed no obvious pulmonary lesions. Previously reported studies showing that myeloma patients with elevated KL-6 might have a poor prognosis prompted us to treat this patient with a three-drug (bortezomib, cyclophosphamide, and dexamethasone: VCD) combination regimen. When 6 cycles of the regimen had been completed, no M-protein was detectable in her serum. Furthermore, κ free light chain had significantly decreased from 12,700 to 24.8 mg/l. In addition, (18)F-FDG PET/CT revealed reduced mass sizes and no (18)F-FDG uptakes by plasmacytomas. Thus, she was defined as having achieved a stringent complete remission (sCR). We therefore concluded that the VCD combination regimen was highly effective in this multiple myeloma patient with KL-6 elevation.

A retrospective analysis of clinical features and treatment outcome in 21 patients with immunoglobulin M-related light-chain amyloidosis in Japan: a study from the Amyloidosis Research Committee.

We retrospectively gathered data of 21 patients (13 male and 8 female; median age 65 years) diagnosed with immunoglobulin M (IgM)-related light-chain (AL) amyloidosis in Japan to investigate characteristics of IgM-AL amyloidosis and its optimal treatment strategy. Median IgM and difference free light chain (FLC) at diagnosis were 1257 mg/dl and 34.3 mg/l, respectively. Organ involvement was observed in the heart in 7 patients (33%), kidneys in 15 (71%), and lymph nodes in 5 (24%). Initial treatments were melphalan/dexamethasone in 7 patients, bortezomib/cyclophosphamide/dexamethasone in 3, autologous stem cell transplantation in 3, rituximab/bendamustine in 1, other in 3, and none in 4. Hematological responses among 15 evaluable patients were as follows: 3 reached complete response (CR), 4 partial response (PR), and 1 very good PR (VGPR), making the overall response rate of PR or better 40%. Median overall survival (OS) was 14.0 months and 1-year OS was 71.4%. Prognosis was significantly poorer in patients with cardiac involvement than those with non-cardiac involvement (1-year OS 27.8% vs. 85.7%, p = 0.0468). The involved FLC value was low in several patients and therapeutic response was difficult to assess. Further study is necessary to determine the optimal treatment for IgM-AL amyloidosis.

Identification and characterization of a novel enhancer in the HTLV-1 proviral genome.

Human T-cell leukemia virus type 1 (HTLV-1) is a retrovirus that causes adult T-cell leukemia/lymphoma (ATL), a cancer of infected CD4+ T-cells. There is both sense and antisense transcription from the integrated provirus. Sense transcription tends to be suppressed, but antisense transcription is constitutively active. Various efforts have been made to elucidate the regulatory mechanism of HTLV-1 provirus for several decades; however, it remains unknown how HTLV-1 antisense transcription is maintained. Here, using proviral DNA-capture sequencing, we found a previously unidentified viral enhancer in the middle of the HTLV-1 provirus. The transcription factors, SRF and ELK-1, play a pivotal role in the activity of this enhancer. Aberrant transcription of genes in the proximity of integration sites was observed in freshly isolated ATL cells. This finding resolves certain long-standing questions concerning HTLV-1 persistence and pathogenesis. We anticipate that the DNA-capture-seq approach can be applied to analyze the regulatory mechanisms of other oncogenic viruses integrated into the host cellular genome.

Fibrous stroma and vascularity of pancreatic carcinoma: correlation with enhancement patterns on CT.

OBJECTIVE: To demonstrate the contrast-enhancement behavior of pancreatic carcinoma on dynamic contrast-enhanced CT (DCE-CT), and the relationship between the degree of contrast-enhancement and the vascularity (vessel density) and amount of fibrous stroma (fibrosis within the tumor) on pathological specimen. METHODS: The contrast-enhancement values were measured by producing the subtracting images for obtaining largest region of interests to reduce measurement errors and variability. Vascularity was determined by immunostaining of the tissue sections with factor 8 and the fibrous stroma was determined by picrosirius staining. Correlation of the findings of DCE-CT with pathological findings was performed in 21 patients with pancreatic carcinoma. RESULTS: All but one patient exhibited a gradually increasing enhancement, but there was considerably wide range in contrast-enhancement values of tumors. Examination of the overall relationship between vascularity and fibrous stroma with contrast-enhancement behavior showed that tumor with more fibrosis and higher vascularity had a higher contrast effect through all phases of dynamic study. Tumors having liver metastases tended to be less fibrotic than tumors without liver metastases. CONCLUSION: The contrast-enhancement behavior of pancreatic carcinoma may be helpful in estimating vascularity and the extent of tumor fibrosis and possibility of liver metastases.

[Clinical usefulness of serum free light chain measurement in monoclonal gammopathy].

Recently, a highly sensitive assay (FREELITE) capable of measuring serum immunoglobulin-free light chains (FLC) was developed. An abnormal kappa/lambda ratio supports the presence of clonal plasma cell expansion. Using this assay, we measured serum and urine samples of 178 healthy volunteers, 184 patients with polyclonal gamma-globulinemia and 150 patients with monoclonal gamma-globulinemia. The diagnostic sensitivity of the FLC assays for monoclonal gammopathies was 88.0% and the specificity for healthy volunteers and polyclonal gammopathies was 96.1%. The minimal detection sensitivity of this assay for serum FLC was 0.3 mg/l and was greater than 100-fold more sensitive than serum protein electrophoresis (SPE). The combination of FLC with SPE and immunoelectrophoresis identified 99% of patients with monoclonal gammopathies. Effective treatment often leads to a more rapid reduction of the involved FLC level relative to the intact immunoglobulin or total light chain concentration because the half-life of FLC is <6 hours. These observations suggest that FREELITE is useful for diagnosis, disease monitoring and assessment of response to treatment in patients with monoclonal gammopathies such as multiple myeloma and AL amyloidosis.