Beta-2-microglobulin is an independent predictor of progression in asymptomatic multiple myeloma

A review of clinical guidelines, laboratory recommendations and external quality assurance programs for monoclonal gammopathy testing

Monoclonal gammopathy (MG) is a spectrum of diseases ranging from the benign asymptomatic monoclonal gammopathy of undetermined significance to the malignant multiple myeloma. Clinical guidelines and laboratory recommendations have been developed to inform best practices in the diagnosis, monitoring, and management of MG. In this review, the pathophysiology, relevant laboratory testing recommended in clinical practice guidelines and laboratory recommendations related to MG testing and reporting are examined. The clinical guidelines recommend serum protein electrophoresis, serum immunofixation and serum free light chain measurement as initial screening. The laboratory recommendations omit serum immunofixation as it offers limited additional diagnostic value. The laboratory recommendations offer guidance on reporting findings beyond monoclonal protein, which was not required by the clinical guidelines. The clinical guidelines suggested monitoring total IgA concentration by turbidimetry or nephelometry method if the monoclonal protein migrates in the non-gamma region, whereas the laboratory recommendations make allowance for involved IgM and IgG. Additionally, several external quality assurance programs for MG protein electrophoresis and free light chain testing are also appraised. The external quality assurance programs show varied assessment criteria for protein electrophoresis reporting and unit of measurement. There is also significant disparity in reported monoclonal protein concentrations with wide inter-method analytical variation noted for both monoclonal protein quantification and serum free light chain measurement, however this variation appears smaller when the same method was used. Greater harmonization among laboratory recommendations and reporting format may improve clinical interpretation of MG testing.

Analysis of the B2M Expression in Colon Adenocarcinoma and Its Correlation with Patient Prognosis

Colon adenocarcinoma (COAD) is one of the most common malignant tumors in clinics. It is often found at an advanced stage, with high incidence and poor prognosis; early diagnosis is difficult and treatment methods are limited. In order to find new methods for diagnosis and treatment of COAD, people pay more and more attention to the discovery and functional research of new oncogenes and tumor suppressor genes of COAD. β2-microglobulin (B2M) plays different physiological and pathological roles in tumor cells and nontumor cells. At present, there is no public report on the expression of B2M in COAD. In this study, the expression of B2M mRNA in COAD tissues was compared with that in normal tissues. The relationship between the expression of B2M mRNA and the stage, histological subtype, lymph node metastasis, TP53 mutation, and survival time of COAD was discussed. It was found that B2M is a potential tumor suppressor gene in COAD. The decreased expression of B2M after mutation can cause immune escape of COAD cells, thus affecting the therapeutic effect and prognosis. This study provides a new idea for the prevention and treatment of COAD.

Lifting the Veil: Characteristics, Clinical Significance, and Application of β-2-Microglobulin as Biomarkers and Its Detection with Biosensors

Because β-2-microglobulin (β₂M) is a surface protein that is present on most nucleated cells, it plays a key role in the human immune system and the kidney glomeruli to regulate homeostasis. The primary clinical significance of β₂M is in dialysis-related amyloidosis, a complication of end-stage renal disease caused by a gradual accumulation of β₂M in the blood. Therefore, the function of β₂M in kidney-related diseases has been extensively studied to evaluate its glomerular and tubular functions. Because increased β₂M shedding due to rapid cell turnover may indicate other underlying medical conditions, the possibility to use β₂M as a versatile biomarker rose in prominence across multiple disciplines for various applications. Therefore, this work has reviewed the recent use of β₂M to detect various diseases and its progress as a biomarker. While the use of state-of-the-art β₂M detection requires sophisticated tools, high maintenance, and labor cost, this work also has reported the use of biosensor to quantify β₂M over the past decade. It is hoped that a portable and highly efficient β₂M biosensor device will soon be incorporated in point-of-care testing to provide safe, rapid, and reliable test results.

Serum Free Light-Chain Ratio at Diagnosis Is Associated with Early Renal Damage in Multiple Myeloma: A Case Series Real-World Study

The serum free light-chain (FLC) ratio is a sensitive tool for the differential diagnosis of plasma cell disorders and is biomarker of multiple myeloma (MM) progression from premalignant conditions. Here, we investigate the potential role of FLC ratio at diagnosis in identifying early renal damage in MM patients and other correlations with clinical, laboratory, and molecular findings. A total of 34 MM patients who had undergone autologous stem cell transplantation were included in this retrospective case series study, and FLC quantification was performed with nephelometric assays. In our study, sFLC ratio was significantly associated with light-chain MM and β-2 microglobulin levels, likely indicating a high disease burden at diagnosis, especially in patients without heavy chain M-protein at serum electrophoresis. Moreover, the sFLC ratio was inversely correlated with glomerular filtration rate, possibly identifying early renal damage in MM patients. Our preliminary results confirm the importance of early sFLC evaluation, especially in patients with the light-chain MM type and low disease burden, to minimize the risk of late renal failure.

Inflammatory and autoimmune predictive markers of response to anti‑PD‑1/PD‑L1 therapy in NSCLC and melanoma

Immune checkpoint inhibitors (ICI) are a standard in cancer therapy, but few patients respond to the treatment. The aim of the present study was the determination of immunological markers for monitoring response to ICI. The present study included 74 patients receiving ICI in subsequent [group 1; non-small cell lung cancer (NSCLC)] and first-line setting (group 2; melanoma) and 30 patients with NSCLC receiving first-line chemotherapy. In groups 1 and 2 β-2 microglobulin (B2-MG), neopterin (NPT), IL-6, IL-18, HLA-DRB1 and autoantibodies were assessed after two months of ICI, and before the start of next administration in group 3. In group 1 low level of B2-MG (P<0.0001), NPT (P<0.0001), IL-6 (P<0.0001), IL-18 (P=0.0003), HLA-DRB1*03 (P=0.016) and anti-TPO antibodies (P=0.016) were associated with response >six months. In group 2 high level of B2-MG (P=0.0001), NPT (P=0.0016), IL-6 (P=0.013) and IL-18 (P=0.032) were associated with early disease progression (<six months). Univariate analysis demonstrated that immune-related adverse events were predictive marker of prolonged progression-free survival (PFS) in group 1 (P=0.038) and 2 (P=0.020). Neutrophil-lymphocyte ratio ≥5 before immunotherapy was correlated with shorter PFS in melanoma in multivariate analysis (P=0.007). B2-MG ≥2.5 mg/ml (P=0.006) and NPT ≥12 nmol/l (P=0.027) were predictors of shorter PFS in group 1. B2-MG ≥2.5 mg/ml was predictor of shorter PFS (P=0.008) in group 2. In group 1 levels of B2-MG, NPT, IL-6 and IL-18 were higher than in group 3. In summary, immunological markers are promising predictive markers for immunotherapy; however, it requires further prospective studies.

Machine learning predicts treatment sensitivity in multiple myeloma based on molecular and clinical information coupled with drug response

Providing treatment sensitivity stratification at the time of cancer diagnosis allows better allocation of patients to alternative treatment options. Despite many clinical and biological risk markers having been associated with variable survival in cancer, assessing the interplay of these markers through Machine Learning (ML) algorithms still remains to be fully explored. Here, we present a Multi Learning Training approach (MuLT) combining supervised, unsupervised and self-supervised learning algorithms, to examine the predictive value of heterogeneous treatment outcomes for Multiple Myeloma (MM). We show that gene expression values improve the treatment sensitivity prediction and recapitulates genetic abnormalities detected by Fluorescence in situ hybridization (FISH) testing. MuLT performance was assessed by cross-validation experiments, in which it predicted treatment sensitivity with 68.70% of AUC. Finally, simulations showed numerical evidences that in average 17.07% of patients could get better response to a different treatment at the first line.

Testing Mayo Clinic's New 20/20/20 Risk Model in Another Cohort of Smoldering Myeloma Patients: A Retrospective Study

Background—smoldering multiple myeloma (SMM) risk of progression to multiple myeloma (MM) is highly heterogeneous and several models have been suggested to predict this risk. Lakshman et al. recently proposed a model based on three biomarkers: bone marrow plasma cell (BMPC) percentage > 20%, free light chain ratio (FLCr) > 20 and serum M protein > 20 g/L. The goal of our study was to test this “20/20/20” model in our population and to determine if similar results could be obtained in another cohort of SMM patients. Method—we conducted a retrospective, single center study with 89 patients diagnosed with SMM between January 2008 and December 2019. Results—all three tested biomarkers were associated with an increased risk of progression: BMPC percentage ≥ 20% (hazard ratio [HR]: 4.28 [95%C.I., 1.90–9.61]; p < 0.001), serum M protein ≥ 20 g/L (HR: 4.20 [95%C.I., 1.90–15.53]; p = 0.032) and FLCr ≥ 20 (HR: 3.25 [95%C.I., 1.09–9.71]; p = 0.035). The estimated median time to progression (TTP) was not reached for the low and intermediate risk groups and was 29.1 months (95%C.I., 3.9–54.4) in the high-risk group (p = 0.006). Conclusions—the 20/20/20 risk stratification model adequately predicted progression in our population and is easy to use in various clinical settings.

Modulating gene regulation to treat genetic disorders

Over a thousand diseases are caused by mutations that alter gene expression levels. The potential of nuclease-deficient zinc fingers, TALEs or CRISPR fusion systems to treat these diseases by modulating gene expression has recently emerged. These systems can be applied to modify the activity of gene-regulatory elements - promoters, enhancers, silencers and insulators, subsequently changing their target gene expression levels to achieve therapeutic benefits - an approach termed cis-regulation therapy (CRT). Here, we review emerging CRT technologies and assess their therapeutic potential for treating a wide range of diseases caused by abnormal gene dosage. The challenges facing the translation of CRT into the clinic are discussed.

Salivary β2-microglobulin levels in patients with erosive oral lichen planus and squamous cell carcinoma

OBJECTIVES

β2 microglobulin, as a biomarker, is used for the diagnosis of oral malignant and pre-malignant lesions. The components of the microglobulin system can directly or indirectly help grow and develop tumors. The present study aims to compare beta-2 microglobulin levels in patients with lichen planus of the esophagus, oral squamous cell carcinoma, and healthy individuals. Further, it evaluated the salivary β2-microglobulin level in malignant and pre-malignant lesions. Oral lichen planus (OLP) is a chronic skin-mucus disorder. Of the total 75 patients referred to Oral Medicine at Dentistry School of Zahedan University of Medical Sciences, 25 were healthy and 25 had oral lichen planus (OLP) and the rest had squamous cell carcinoma (SCC). To collect the saliva samples, unstimulated spitting was used. They were collected between 9 and 12 a.m. Salivary beta2 microglobulin was recorded based on the factory instructions by ELISA optical density method with 450 nm wavelength for each sample. The data were analyzed using descriptive, Kruskal-Wallis and Mann-Whitney and Pearson's correlation coefficient (SPSS 21).

RESULTS

The salivary β2 microglobulin level in patients with squamous cell carcinoma (SCC) and oral lichen plan (OLP) is significantly higher than that in healthy group. Thus, this index is used for assessing early malignant transformation and oral pre-malignant lesion.

Tumor load in patients with multiple myeloma: β₂-microglobulin levels versus low-dose whole-body CT

OBJECTIVE

Beta-2-microglobulin is a serum marker of tumor burden in multiple myeloma (MM). Our aim was to correlate serum β₂-microglobulin levels in patients with MM to tumor burden determined by low-dose whole-body CT (LDWBCT).

MATERIALS AND METHODS

A total of 52 patients with newly diagnosed, untreated MM who underwent LDWBCT were included. LDWBCT scans were assessed by two musculoskeletal radiologists in consensus for focal lesions. The Durie and Salmon PLUS staging system was used for staging patients in stages I-III. β₂-microglobulin was also subdivided into stages I-III on the basis of the multiple myeloma International Staging System (ISS).

RESULTS

Using the Durie and Salmon PLUS staging system criteria for image evaluation, we were able to identify stage I MM in 17 patients, stage II MM in nine patients, and stage III MM in 26 patients. Eight of nine patients with stage II MM and 16 of 26 patients with stage III MM had normal β₂-microglobulin levels. Thus, 24 of 35 patients (68.6%) had 5 or more focal lesions and false-negative β₂-microglobulin levels.

CONCLUSION

Serum β₂-microglobulin levels alone may not indicate the full extent of tumor burden in a significant subset of myeloma patients.

Rare case of non-producer variant of plasma cell dyscrasias with circulating plasma cells

Non-producing variant of plasma cell disorders with circulating plasma cells is an aggressive variant of plasma cell dyscrasias with relatively poor outcomes. A 75-year-old man was admitted due to anaemia (90 g/L) and thrombocytopenia (9×10⁹/L). Comprehensive metabolic panel showed creatinine of 1.34 mg/dL, total protein of 6 g/dL, and corrected calcium was normal. Peripheral smear review showed 8% circulating atypical plasmacytoid cells. Bone marrow biopsy (BMB) confirmed plasma cell myeloma involving 90%-95% of bone marrow cellularity. Serum protein electrophoresis showed no monoclonal protein. Due to aggressive biology of non-producer variant and outcomes based on circulating plasma cells, he was started on VD-PACE (bortezomib, dexamethasone, cisplatin, doxorubicin, cyclophosphamide and etoposide) chemotherapy. BMB after cycle 1 chemotherapy showed no morphologic, immunophenotypic, or flow cytometric features of a plasma cell neoplasm. Given excellent treatment response cycle 2 was changed to VRD (bortezomib, lenalidomide and dexamethasone). Following two cycles of VRD, he underwent autologous haematopoietic cell transplantation. Day 80 BMB suggested stringent complete response.

Incidence and risk factors for acute kidney injury following autologous stem cell transplantation for multiple myeloma

Acute kidney injury (AKI) is a common complication after allogeneic stem cell transplantation; however, its incidence and outcome in patients transplanted for multiple myeloma (MM) is unknown. We evaluated the incidence, severity, and risk factors for AKI within the first 30 days after autologous stem cell transplantation (ASCT) for MM. We prospectively followed 185 consecutive patients with MM, without chronic renal replacement therapy, who underwent ASCT; 12.5% of patients had MM‐associated amyloidosis. AKI occurred in 19 (10.3%) patients, 8 ± 3 days after ASCT, with 18 patients (9.7%) stage 1 and one patient (0.6%) stage 2 AKI. The development of AKI was not associated with reduced overall survival and recovery of kidney function was evident in 68.4% of patients at 3 months. In Cox regression analysis, preexisting–chronic kidney disease (HR 7.01, CI 95% 2.04‐24.09; P = 0.002), serum beta2 microglobulin (HR 3.05, CI 95% 1.10‐8.44; P = 0.03), and mucositis grade 3/4 (HR 1.29, CI 95% 1.08‐1.53; P = 0.003) were independent risk factors for AKI. Our results suggest that AKI occurs with low incidence and reduced severity after ASCT for MM. Prophylactic measures in patients with preexisting–kidney failure may further reduce this risk.

Development of an Initial Conceptual Model of Multiple Myeloma to Support Clinical and Health Economics Decision Making

Background. We aimed to develop and validate a conceptual model of multiple myeloma (MM) that characterizes the attributes affecting disease progression and patient outcomes, and the relationships between them. Methods. Systematic and targeted literature reviews identified disease- and patient-specific attributes of MM that affect disease progression and outcomes. These attributes were validated by a Delphi panel of four international MM experts, and a physician-validated model was constructed. Real-world clinical data from the Czech Registry of Monoclonal Gammopathies (RMG) was used to confirm the relationships between attributes using pairwise correlations and multiple Cox regression analysis. Results. The Delphi panel reached consensus that most cytogenetic abnormalities influenced disease activity, which results in symptoms and complications and affects overall survival (OS). Comorbidities and complications also affect OS. The entire panel agreed that quality of life was influenced by comorbidities, age, complications, and symptoms. Consensus was not reached in some cases, in particular, the influence of del(17p) on complications. The relationships between attributes were confirmed using pairwise analysis of real-world data from the Czech RMG; most of the correlations identified were statistically significant and the strength of the correlations changed with successive relapses. Czech RMG data were also used to confirm significant predictors of OS included in the model, such as age, Eastern Cooperative Oncology Group performance status, and extramedullary disease. Conclusions. This validated conceptual model can be used for economic modeling and clinical decision making. It could also inform the development of disease-based models to explore the impact of disease progression and treatment on outcomes in patients with MM.

Linking transcriptional and genetic tumor heterogeneity through allele analysis of single-cell RNA-seq data

Characterization of intratumoral heterogeneity is critical to cancer therapy, as the presence of phenotypically diverse cell populations commonly fuels relapse and resistance to treatment. Although genetic variation is a well-studied source of intratumoral heterogeneity, the functional impact of most genetic alterations remains unclear. Even less understood is the relative importance of other factors influencing heterogeneity, such as epigenetic state or tumor microenvironment. To investigate the relationship between genetic and transcriptional heterogeneity in a context of cancer progression, we devised a computational approach called HoneyBADGER to identify copy number variation and loss of heterozygosity in individual cells from single-cell RNA-sequencing data. By integrating allele and normalized expression information, HoneyBADGER is able to identify and infer the presence of subclone-specific alterations in individual cells and reconstruct the underlying subclonal architecture. By examining several tumor types, we show that HoneyBADGER is effective at identifying deletions, amplifications, and copy-neutral loss-of-heterozygosity events and is capable of robustly identifying subclonal focal alterations as small as 10 megabases. We further apply HoneyBADGER to analyze single cells from a progressive multiple myeloma patient to identify major genetic subclones that exhibit distinct transcriptional signatures relevant to cancer progression. Other prominent transcriptional subpopulations within these tumors did not line up with the genetic subclonal structure and were likely driven by alternative, nonclonal mechanisms. These results highlight the need for integrative analysis to understand the molecular and phenotypic heterogeneity in cancer.

Rediscovering Beta-2 Microglobulin As a Biomarker across the Spectrum of Kidney Diseases

There is currently an unmet need for better biomarkers across the spectrum of renal diseases. In this paper, we revisit the role of beta-2 microglobulin (β₂M) as a biomarker in patients with chronic kidney disease and end-stage renal disease. Prior to reviewing the numerous clinical studies in the area, we describe the basic biology of β₂M, focusing in particular on its role in maintaining the serum albumin levels and reclaiming the albumin in tubular fluid through the actions of the neonatal Fc receptor. Disorders of abnormal β₂M function arise as a result of altered binding of β₂M to its protein cofactors and the clinical manifestations are exemplified by rare human genetic conditions and mice knockouts. We highlight the utility of β₂M as a predictor of renal function and clinical outcomes in recent large database studies against predictions made by recently developed whole body population kinetic models. Furthermore, we discuss recent animal data suggesting that contrary to textbook dogma urinary β₂M may be a marker for glomerular rather than tubular pathology. We review the existing literature about β₂M as a biomarker in patients receiving renal replacement therapy, with particular emphasis on large outcome trials. We note emerging proteomic data suggesting that β₂M is a promising marker of chronic allograft nephropathy. Finally, we present data about the role of β₂M as a biomarker in a number of non-renal diseases. The goal of this comprehensive review is to direct attention to the multifaceted role of β₂M as a biomarker, and its exciting biology in order to propose the next steps required to bring this recently rediscovered biomarker into the twenty-first century.

Circulating Beta-2 Microglobulin and Risk of Cancer: The Atherosclerosis Risk in Communities Study (ARIC)

BACKGROUND

Serum β-2 microglobulin (B2M), a major histocompatibility complex class I molecule that is a biomarker of kidney filtration and increased cell turnover, is elevated at the time of diagnosis in hematological and some solid cancers. However, serum B2M was not examined prospectively as a marker for cancer risk. We hypothesized that in a population without a prior cancer diagnosis, serum B2M is associated with risk of cancer (n = 2,436), including colorectal (n = 255), lung (n = 298), breast (n = 424), and prostate (n = 524) cancers, and hematological (n = 176) malignancies.

METHODS

The analytical cohort (n = 12,300) was followed for incident cancers from 1990 through 2006. B2M (range, 0.9-57.8 mg/L) was measured in stored serum collected in 1990-1992. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals for cancer incidence and mortality in relation to quartiles of B2M.

RESULTS

Adjusting for age, sex, race, center, education, body mass index, smoking, aspirin, and hormone therapy (in women) and comparing highest to lowest B2M quartiles, HRs were 1.25 (1.06-1.47; Ptrend = 0.002) for total cancer risk and 2.21 (1.32-3.70; Ptrend=0.001) for colorectal cancer risk, with similar HRs for colon and rectal cancers. These associations remained after adjustment for an inflammatory biomarker, C-reactive protein, and after excluding the first three years of follow-up. Significant associations were also observed for mortality from total, lung, and hematological cancers.

CONCLUSIONS

These findings provide the first evidence that higher serum B2M is associated with increased colorectal cancer risk.

IMPACT

This study supports B2M as a potential biomarker for colorectal cancer risk. Cancer Epidemiol Biomarkers Prev; 25(4); 657-64. ©2016 AACR.

High density of tryptase-positive mast cells in patients with multiple myeloma: correlation with parameters of disease activity

Multiple myeloma (MM) is a plasma cell neoplasm characterized by bone marrow infiltration from malignant plasma cells. Mast cells play an important role in inflammation and angiogenesis in malignant diseases. The aim of the study was to evaluate the mast cell density in bone marrow of untreated MM patients with markers of disease activity such as serum interleukin-6 (IL-6), B2M, and C-reactive protein (CRP), the grade of bone marrow infiltration, and the levels of produced paraprotein. We studied 86 newly diagnosed MM patients (46 males, 40 females, mean age 59 ± 13.7 years). Thirty of them reached plateau phase after chemotherapy and 20 healthy volunteers. According to the criteria of International Staging System (ISS) staging system, 23 patients had stage I, 30 had stage II, and 33 had stage III. The serum concentrations of CRP, B2M, and IL-6, and the mast cell density (MCD) values were significantly higher in MM patients' group (1.6 ± 1.8, 4.3 ± 2.9, 7.1 ± 5.1, and 9 ± 4.8), in comparison with those found in control group (0.4 ± 0.1, 1.5 ± 0.6, 1.1 ± 0.5, and 1.9 ± 0.7; p < 0.001 in all the cases). Significant differences were found between the grade of infiltration in bone marrow, and the paraprotein values in patients' serum before and after chemotherapy. Furthermore, there was a significant correlation between the MCD values and the prognostic markers CRP (r = 0.452, p < 0.0001), IL-6 (r = 0.475, p < 0.0001), bone marrow infiltration (r = 0.333, p < 0.0002), and serum paraprotein levels(r = 0.221, p < 0.04). High MCD values strengthen the hypothesis that mast cells participate in the pathogenesis of disease progression and may be used as an indicator of the disease activity.

Iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) magnetic resonance imaging as a biomarker for symptomatic multiple myeloma

Introduction

To evaluate the effectiveness of iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) magnetic resonance imaging (MRI) to discriminate between symptomatic and asymptomatic myeloma in lumbar bone marrow without visible focal lesions.

Materials and Methods

The lumbar spine was examined with 3-T MRI in 11 patients with asymptomatic myeloma and 24 patients with symptomatic myeloma. The fat-signal fraction was calculated from the ratio of the signal intensity in the fat image divided by the signal intensity of the corresponding ROI in the in-phase IDEAL image. The t test was used to compare the asymptomatic and symptomatic groups. ROC curves were constructed to determine the ability of variables to discriminate between symptomatic and asymptomatic myeloma.

Results

Univariate analysis showed that β2-microglobulin and bone marrow plasma cell percent (BMPC%) were significantly higher and fat-signal fraction was significantly lower with symptomatic myeloma than with asymptomatic myeloma. Areas under the curve were 0.847 for β₂;-microglobulin, 0.834 for fat-signal fraction, and 0.759 for BMPC%.

Conclusion

The fat-signal fraction as a biomarker for multiple myeloma enables discrimination of symptomatic myeloma from asymptomatic myeloma. The fat-signal fraction offers superior sensitivity and specificity to BMPC% of biopsy specimens.

Role of β2-microglobulin in uremic patients may be greater than originally suspected

The role of beta2-microglobulin (β₂M) in dialysis-related amyloidosis as a specific amyloid precursor was defined in the 1980s. Studies in those years were largely related to β₂M amyloidosis. In 2005, for what was probably the first time in the available literature, we provided data about the association between β₂M and early-onset atherosclerosis in hemodialysis patients without co-morbidities. In recent years, the role of uremic toxins in uremic atherosclerosis and the interest in β₂M as a marker of cardiovascular (CV) and/or mortality risk have grown. In the current literature, clinical studies suggest that β₂M is an independent, significant predictor of mortality, not only in dialysis patients, but also in predialysis patients and in the high-risk portion of the general population, and it seems to be a factor strongly linked to the presence and severity of CV disease. It is still unknown whether β₂M is only a uremic toxin marker or if it also has an active role in vascular damage, but data support that it may reflect an increased burden of systemic atherosclerosis in a setting of underlying chronic kidney disease. Thus, although there have been some inconsistencies among the various analyses relating to β₂M, it promises to be a novel risk marker of kidney function in the awareness and detection of high-risk patients. However, more research is required to establish the pathophysiological relationships between retained uremic toxins and further biochemical modifications in the uremic milieu to get answers to the questions of why and how. In this review, the recent literature about the changing role of β₂M in uremic patients will be examined.

Tumour markers and kidney function: a systematic review

Tumour markers represent useful tools in diagnosis and clinical management of patients with cancer, because they are easy to use, minimally invasive, and easily measured in either blood or urine. Unfortunately, such an ideal marker, as yet, does not exist. Different pathological states may increase the level of a tumour marker in the absence of any neoplasia. Alternatively, low levels of tumour markers could be also found in the presence of neoplasias. We aimed at reviewing studies currently available in the literature examining the association between tumour markers and different renal impairment conditions. Each tumour marker was found to be differently influenced by these criteria; additionally we revealed in many cases a lack of available published data.

Novel filtration markers as predictors of all-cause and cardiovascular mortality in US adults

BACKGROUND

New filtration markers, including β-trace protein (BTP) and β₂-microglobulin (B2M), may, similar to cystatin C, enable a stronger prediction of mortality compared to serum creatinine-based estimated glomerular filtration rate (eGFRcr). We sought to evaluate these mortality associations in a representative sample of US adults.

STUDY DESIGN

Prospective cohort study.

SETTING & PARTICIPANTS

6,445 adults 20 years or older from the Third National Health and Nutrition Examination Survey (1988-1994) with mortality linkage through December 31, 2006.

PREDICTORS

Serum cystatin C, BTP, and B2M levels and eGFRcr categorized into quintiles, with the highest quintile (lowest for eGFRcr) split into tertiles (subquintiles Q5a-Q5c).

OUTCOMES

All-cause, cardiovascular disease, and coronary heart disease mortality.

MEASUREMENTS

Demographic- and multivariable-adjusted Cox proportional hazard models.

RESULTS

During follow-up, 2,392 deaths (cardiovascular, 1,079; coronary heart disease, 605) occurred. Levels of all 4 filtration markers were associated with mortality risk after adjusting for demographics (P trend<0.02). Adjusted for mortality risk factors, compared to the middle quintile, the highest subquintiles for cystatin C (Q5c: HR, 1.94; 95% CI, 1.43-2.62), BTP (Q5c: HR, 2.14; 95% CI, 1.56-2.94), and B2M (Q5c: HR, 2.58; 95% CI, 1.96-3.41) were associated with increased all-cause mortality risk, whereas the association was weaker for eGFRcr (Q5c: HR, 1.31; 95% CI, 0.84-2.04). Associations persisted for the novel markers and not for eGFRcr at eGFRcr ≥60 mL/min/1.73 m². Trends were similar for cardiovascular disease and coronary heart disease mortality.

LIMITATIONS

Single measurements of markers from long-term stored samples.

CONCLUSIONS

The strong association of cystatin C level with mortality compared with serum creatinine estimates is shared by BTP and B2M. This supports the utility of alternative filtration markers beyond creatinine when improved risk prediction related to decreased GFR is needed.

Genome-wide association study identified the human leukocyte antigen region as a novel locus for plasma beta-2 microglobulin

Beta-2 microglobulin (B2M) is a component of the major histocompatibility complex (MHC) class I molecule and has been studied as a biomarker of kidney function, cardiovascular diseases and mortality. Little is known about the genes influencing its levels directly or through glomerular filtration rate (GFR). We conducted a genome-wide association study of plasma B2M levels in 6738 European Americans from the Atherosclerosis Risk in Communities study to identify novel loci for B2M and assessed its association with known estimated GFR (eGFR) loci. We identified 2 genome-wide significant loci. One was in the human leukocyte antigen (HLA) region on chromosome 6 (lowest p value = 1.8 × 10(-23) for rs9264638). At this locus, 6 index SNPs accounted for 3.2 % of log(B2M) variance, and their association with B2M could largely be explained by imputed classical alleles of the MHC class I genes: HLA-A, HLA-B, or HLA-C. The index SNPs at this locus were not associated with eGFR based on serum creatinine (eGFRcr). The other locus of B2M was on chromosome 12 (rs3184504 at SH2B3, beta = 0.02, p value = 3.1 × 10(-8)), which was previously implicated as an eGFR locus. In conclusion, although B2M is known to be a component of MHC class I molecule, the association between HLA class I alleles and plasma B2M levels in a community-based population is novel. The identification of the two novel loci for B2M extends our understanding of its metabolism and informs its use as a kidney filtration biomarker.

Genome-wide association study identified the human leukocyte antigen region as a novel locus for plasma beta-2 microglobulin

Beta-2 microglobulin (B2M) is a component of the major histocompatibility complex (MHC) class I molecule and has been studied as a biomarker of kidney function, cardiovascular diseases and mortality. Little is known about the genes influencing its levels directly or through glomerular filtration rate (GFR). We conducted a genome-wide association study of plasma B2M levels in 6738 European Americans from the Atherosclerosis Risk in Communities study to identify novel loci for B2M and assessed its association with known estimated GFR (eGFR) loci. We identified 2 genome-wide significant loci. One was in the human leukocyte antigen (HLA) region on chromosome 6 (lowest p value = 1.8 × 10(-23) for rs9264638). At this locus, 6 index SNPs accounted for 3.2 % of log(B2M) variance, and their association with B2M could largely be explained by imputed classical alleles of the MHC class I genes: HLA-A, HLA-B, or HLA-C. The index SNPs at this locus were not associated with eGFR based on serum creatinine (eGFRcr). The other locus of B2M was on chromosome 12 (rs3184504 at SH2B3, beta = 0.02, p value = 3.1 × 10(-8)), which was previously implicated as an eGFR locus. In conclusion, although B2M is known to be a component of MHC class I molecule, the association between HLA class I alleles and plasma B2M levels in a community-based population is novel. The identification of the two novel loci for B2M extends our understanding of its metabolism and informs its use as a kidney filtration biomarker.