Light chain amyloidosis: Where are the light chains from and how they play their pathogenic role?

In-hospital outcomes among amyloidosis patients with atrial fibrillation: A propensity score-matched analysis

Background

The impact of atrial fibrillation (AF) among patients with amyloidosis on in-hospital outcomes is not well-established. We aimed to examine in-hospital outcomes among patients admitted with a primary diagnosis of AF with and without amyloidosis.

Methods and Results

We queried the Nationwide Readmissions Database to compare the in-hospital outcomes among AF patients with and without amyloidosis. Our study demonstrated that in-hospital all-cause mortality, adverse events, and 30-day readmission were comparable between the two groups.

Conclusions

Patients with AF and concurrent amyloidosis did not have worse in-hospital outcomes than those with AF alone.

Current status and prospect of anti-amyloid fibril therapy in AL amyloidosis

Amyloid light-chain (AL) amyloidosis is a rare hematological disease that produces abnormal monoclonal immunoglobulin light chains to form amyloid fibrils that are deposited in tissues, resulting in organ damage and dysfunction. Advanced AL amyloidosis has a very poor prognosis with a high risk of early mortality. The combination of anti-plasma cell therapy and amyloid fibrils clearance is the optimal treatment strategy, which takes into account both symptoms and root causes. However, research on anti-amyloid fibrils lags far behind research on anti-plasma cells, and there is currently no approved treatment that could clear amyloid fibrils. Nevertheless, anti-amyloid fibril therapies are being actively investigated recently and have shown potential in clinical trials. In this review, we aim to outline the preclinical work and clinical efficacy of fibril-directed therapies for AL amyloidosis.

Semi-Quantification of Myocardial Uptake of Bone-Seeking Agents in Suspected Cardiac Amyloidosis

INTRODUCTION

Bone scintigraphy has emerged as a key tool for non-invasive etiologic diagnosis of transthyretin (ATTR) cardiac amyloidosis (CA). We focused on a new semi-quantification method (on planar imaging) that could complement the qualitative/visual Perugini scoring system, especially when SPET/CT is not available.

MATERIAL AND METHODS

We retrospectively/qualitatively evaluated 8674 consecutive, planar 99mTc-biphosphonate scintigraphies (performed for non-cardiac reasons), identifying 68 (0.78%) individuals (mean age 79 ± 7 years, range 62-100 years; female/male ratio 16/52) presenting myocardial uptake. Due to the retrospective nature of the study, no SPET/CT, pathologic or genetic confirmation was obtained. The Perugini scoring system was determined (in patients presenting cardiac uptake) and compared with three newly proposed semi-quantitative indices. We took 349 consecutive bone scintigraphies, qualitatively absent of any cardiac/pulmonary uptake, as "healthy controls" (HC).

RESULTS

The heart-to-thigh ratio (RHT) and lung-to-thigh ratio (RLT) indices were significantly higher in patients than in HCs (p ≤ 0.0001). There were statistically significant differences for RHT in HCs vs. patients with qualitative Perugini scores of 1 or >1 (with p ranging from ≤0.001 to ≤0.0001). ROC curves showed that RHT outperformed the other indices and was more accurate in both male and female groups. Furthermore, in the male population, RHT accurately distinguished HCs and patients with scores of 1 (less likely affected by ATTR) from patients with qualitative scores >1 (more likely affected by ATTR) with an AUC of 99% (sensitivity: 95%; specificity: 97%).

CONCLUSION

The proposed semi-quantitative RHT index can accurately/semi-quantitatively distinguish between HCs and subjects probably affected by CA (Perugini scores from 1 to 3), and could be particularly useful when no SPET/CT data are available (such as in retrospective studies and data mining). Furthermore, RHT can semi-quantitatively predict, with very high accuracy, subjects in the male population more likely to be affected by ATTR. The present study, although using a very large sample, is however retrospective, monocentric, and therefore the generalizability of the results should be proved by an accurate external validation.

ADVANCES IN KNOWLEDGE

The proposed heart-to-thigh ratio (RHT) can distinguish healthy controls and subjects that are probably affected by cardiac amyloidosis in a simple and more reproducible way, as compared to standard qualitative/visual evaluation.

Unfolding and Aggregation Pathways of Variable Domains from Immunoglobulin Light Chains

Light chain amyloidosis is the most common form of systemic amyloidosis. This disease is caused by the formation and deposition of amyloid fibers made from immunoglobulin light chains. Environmental conditions such as pH and temperature can affect protein structure and induce the development of these fibers. Several studies have shed light on the native state, stability, dynamics, and final amyloid state of these proteins; however, the initiation process and the fibril formation pathway remain poorly understood structurally and kinetically. To study this, we analyzed the unfolding and aggregation process of the 6aJL2 protein under acidic conditions, with temperature changes, and upon mutation, using biophysical and computational techniques. Our results suggest that the differences in amyloidogenicity displayed by 6aJL2 under these conditions are caused by traversing different aggregation pathways, including unfolded intermediates and the formation of oligomers.

An N-glycosylation hotspot in immunoglobulin κ light chains is associated with AL amyloidosis

Immunoglobulin light chain (AL) amyloidosis is caused by a small, minimally proliferating B-cell/plasma-cell clone secreting a patient-unique, aggregation-prone, toxic light chain (LC). The pathogenicity of LCs is encrypted in their sequence, yet molecular determinants of amyloidogenesis are poorly understood. Higher rates of N-glycosylation among clonal κ LCs from patients with AL amyloidosis compared to other monoclonal gammopathies indicate that this post-translational modification is associated with a higher risk of developing AL amyloidosis. Here, we exploited LC sequence information from previously published amyloidogenic and control clonal LCs and from a series of 220 patients with AL amyloidosis or multiple myeloma followed at our Institutions to define sequence and spatial features of N-glycosylation, combining bioinformatics, biochemical, proteomics, structural and genetic analyses. We found peculiar sequence and spatial pattern of N-glycosylation in amyloidogenic κ LCs, with most of the N-glycosylation sites laying in the framework region 3, particularly within the E strand, and consisting mainly of the NFT sequon, setting them apart with respect to non-amyloidogenic clonal LCs. Our data further support a potential role of N-glycosylation in determining the pathogenic behavior of a subset of amyloidogenic LCs and may help refine current N-glycosylation-based prognostic assessments for patients with monoclonal gammopathies.

Current Updates on the Management of AL Amyloidosis

Systemic immunoglobulin light chain (AL) amyloidosis is a rare but fatal disease. It results from clonal proliferation of plasma cells with excessive production of insoluble misfolded proteins that aggregate in the extracellular matrix, causing damage to the normal architecture and function of various organs. For decades, treatment for AL amyloidosis was based mainly on therapeutic agents previously studied for its more common counterpart, multiple myeloma. As the prevalence and incidence of AL amyloidosis have increased, ongoing research has been conducted with treatments typically used in myeloma with varying success. In this review, we focus on current treatment strategies and updates to clinical guidelines and therapeutics for AL amyloidosis.

Molecular mechanism of amyloidogenic mutations in hypervariable regions of antibody light chains

Systemic light chain (AL) amyloidosis is a fatal protein misfolding disease in which excessive secretion, misfolding, and subsequent aggregation of free antibody light chains eventually lead to deposition of amyloid plaques in various organs. Patient-specific mutations in the antibody V_L domain are closely linked to the disease, but the molecular mechanisms by which certain mutations induce misfolding and amyloid aggregation of antibody domains are still poorly understood. Here, we compare a patient V_L domain with its nonamyloidogenic germline counterpart and show that, out of the five mutations present, two of them strongly destabilize the protein and induce amyloid fibril formation. Surprisingly, the decisive, disease-causing mutations are located in the highly variable complementarity determining regions (CDRs) but exhibit a strong impact on the dynamics of conserved core regions of the patient V_L domain. This effect seems to be based on a deviation from the canonical CDR structures of CDR2 and CDR3 induced by the substitutions. The amyloid-driving mutations are not necessarily involved in propagating fibril formation by providing specific side chain interactions within the fibril structure. Rather, they destabilize the V_L domain in a specific way, increasing the dynamics of framework regions, which can then change their conformation to form the fibril core. These findings reveal unexpected influences of CDR-framework interactions on antibody architecture, stability, and amyloid propensity.

Prognostic Value of Circulating sST2 for the Prediction of Mortality in Patients With Cardiac Light-Chain Amyloidosis

Aims: Systemic light-chain (AL) amyloidosis is a multisystemic disorder leading to multiple organ dysfunction and mortality that is often caused by cardiac involvement. Soluble suppression of tumorigenicity 2 (sST2) is a novel biomarker identified for risk stratification of heart disease. The aim of this study was to investigate the value of circulating sST2 levels in prognosis and mortality risk assessments for the AL amyloidosis population.

Methods and Results: A total of 56 patients diagnosed with AL amyloidosis were enrolled in Peking Union Medical College Hospital (PUMCH) from January 2015 to May 2018. The relationships between the clinical parameters and overall survival (OS) and risk factors for disease progression were assessed. Additionally, receiver operating characteristic (ROC) curves, Kaplan–Meier analysis, and Cox hazard models were performed to explore the predictive value of sST2 in mortality rates. We found that the median OS of all patients was 7.3 [interquartile range (IQR) 4.4, 15.9] months. The median baseline sST2 level was 12.2 (IQR 5.1, 31.1) ng/ml, and the sST2 high group had more severe patients with a higher Mayo stage. In the ROC analysis, the area under the curve (AUC) was 0.728 [95% confidence interval (CI) 0.603–0.853] for sST2 to predict the outcomes of AL amyloidosis patients, and the optimal cutoff value was 12.34 ng/ml (sensitivity 80.2%, specificity 61.1%). Moreover, in multivariate Cox proportional hazards regression analysis, sST2 acted as an independent predictor of poor functional outcome in patients with AL amyloidosis.

Conclusion: In AL amyloidosis patients, sST2 was a strong and independent prognostic biomarker for all-cause mortality, providing complementary prognostic information of a novel scoring system for risk stratification.

Amyloid Proteins and Peripheral Neuropathy

Painful peripheral neuropathy affects millions of people worldwide. Peripheral neuropathy develops in patients with various diseases, including rare familial or acquired amyloid polyneuropathies, as well as some common diseases, including type 2 diabetes mellitus and several chronic inflammatory diseases. Intriguingly, these diseases share a histopathological feature-deposits of amyloid-forming proteins in tissues. Amyloid-forming proteins may cause tissue dysregulation and damage, including damage to nerves, and may be a common cause of neuropathy in these, and potentially other, diseases. Here, we will discuss how amyloid proteins contribute to peripheral neuropathy by reviewing the current understanding of pathogenic mechanisms in known inherited and acquired (usually rare) amyloid neuropathies. In addition, we will discuss the potential role of amyloid proteins in peripheral neuropathy in some common diseases, which are not (yet) considered as amyloid neuropathies. We conclude that there are many similarities in the molecular and cell biological defects caused by aggregation of the various amyloid proteins in these different diseases and propose a common pathogenic pathway for "peripheral amyloid neuropathies".

Abnormal serum carbohydrate antigen 19-9 levels in a patient with splenic retiform haemangioendothelioma concomitant with hepatic amyloidosis: A case report

BACKGROUND

Carbohydrate antigen 19-9 (CA 19-9) is a glycoprotein that is used as a reliable tool for monitoring pancreatic cancer. Serum CA 19-9 levels are increased in patients suffering from liver, lung, and other non-malignant diseases. Haemangioendothelioma is a vascular neoplasm with a borderline biological behaviour. However, no case of haemangioendothelioma has yet been reported to be associated with CA 19-9.

CASE SUMMARY

A 54-year-old Chinese man was referred to our hospital for discontinuous fatigue and unintentional weight loss for over one year. Laboratory investigations revealed an elevated serum CA 19-9 concentration of 39 IU/mL (reference interval, 0–37 IU/mL) over one year before admission. Afterwards, coagulopathy appeared, and the patient’s serum CA 19-9 concentration increased continuously. At the time of admission, abdominal pain and haemorrhagic shock burst occurred, and emergency medical operation was performed. Laboratory investigations conducted upon admission showed a serum CA19-9 concentration of 392.56 IU/mL. Surgical resection of the spleen was undertaken, and pathological examination showed retiform haemangioendothelioma. The patient developed jaundice ten days after surgical excision of the spleen. Pathological examination of needle biopsy samples of the liver yielded a diagnosis of hepatic amyloidosis.

CONCLUSION

We describe a rare case of splenic retiform haemangioenthelioma concomitant with hepatic amyloidosis. Physicians should note abnormal serum CA 19-9 levels with early symptoms of fatigue and unintentional weight loss.

[The prognostic value of baseline serum free light chain in immunoglobulin light-chain cardiac amyloidosis]

Objective: To analyze the prognostic value of baseline serum free light chain (sFLC) in immunoglobulin light-chain cardiac amyloidosis (AL-CA) . Methods: Thirty patients diagnosed with AL-CA from January 2012 to December 2016 at Beijing Chaoyang Hospital were included in this study to retrospectively evaluate the clinical data. The cut-off value of dFLC (involved sFLC minus uninvolved sFLC) was determined according to the receiver operator characteristic curve (ROC) and grouped, the prognoses of both groups were evaluated. Results: The onset age of all AL-CA patients was 57 years old. It occurred more commonly in men (21 cases, 70%) and the light chains of immunoglobulin composed mainly of type λ (22 cases, 73.3%) . Renal involvements occurred in 17 cases (56.7%) . The median value of difference between involved and uninvolved serum immunoglobulin free light chain levels (dFLC) was 162.9 (57.9-401.6) mg/L. More subjects in the high dFLC group had higher BNP (P=0.005) , and shorter median survival than those in the low dFLC group (15 months vs 47 months, P<0.001) . Similar results of median survival were observed when the patients were redivided by a new cut-off value of 180 mg/L for dFLC (high dFLC group: 22 months, low dFLC group: 40 months, P=0.001) , or a κ/λ ratio in which patients with κ type sFLC-ratio<3.79 and λ type sFLC-ratio≥0.06 were grouped into the low sFLC-ratio (37 months) , and the reverse the high sFLC-ratio ones (25 months, P=0.021) . In multivariate analysis, dFLC and New York Heart Association (NYHA) classification of cardiac function were two risk factors associated with all-cause mortality in patients, of them the hazard ratio for higher dFLC was 12.13 (95%CI 2.98-49.30, P<0.001) . Conclusion: Measurement of the sFLC level could implicate the prognosis of AL-CA.

MAGE genes: Prognostic indicators in AL amyloidosis patients

A high frequency of MAGE-CT (cancer testis) antigens are expressed in Multiple Myeloma (MM) patients; however, in other plasma cell dyscrasias, their potential function remains unclear. We measured the expression of MAGE-CT genes (MAGE-C1/CT7, MAGE-A3, MAGE-C2/CT10) in 105 newly diagnosed amyloid light-chain (AL) amyloidosis patients between June 2013 and January 2018 at Peking University People's Hospital using real-time quantitative polymerase chain reaction. In the newly diagnosed AL patients, the positive expression rates of patients with MAGE-C1/CT7, MAGE-C2/CT10 and MAGE-A3 were 83.8% (88/105), 56.71% (38/67) and 22.0% (13/59) respectively. There was no significant correlation between organ propensity and MAGE-CT gene expression. Changes in the MAGE-C1/CT7 levels were consistent with a therapeutic effect. The expression levels of MAGE-C1/CT7, MAGE-C2/CT10 and MAGE-A3 provide potentially effective clinical indicators for auxiliary diagnoses and monitoring treatment efficacy in AL amyloidosis patients.

Bortezomib-based chemotherapy reduces early mortality and improves outcomes in patients with ultra-high-risk light-chain amyloidosis: a retrospective case control study

Background: Patients with amyloid light-chain (AL) amyloidosis who have advanced cardiac damage are at risk of premature mortality. Currently, bortezomib is the mainstay in the treatment of AL amyloidosis, but the benefits of bortezomib in patients with ultra-high-risk (2004 Mayo stage IIIb or 2012 Mayo stage IV) AL amyloidosis have not been proved definitively. Methods: We performed a retrospective analysis of patients newly diagnosed with ultra-high-risk AL amyloidosis who received a bortezomib-based regimen or supportive treatment. We aimed to establish the effects of bortezomib on early mortality and long-term outcomes in this high-risk population. Results: Patients receiving bortezomib-containing chemotherapy (n = 62) and patients receiving no chemotherapy (n = 24) were included. Median overall survival (OS) was 30 months in the bortezomib group and 2 months in the control group (p < .001), and median progression-free survival (PFS) was 15.8 months (bortezomib) and 2 months (control; p < .001). The early-death rate (within 6 months of treatment) was 32.3% (bortezomib) and 66.7% (control; p < .001). In a landmark analysis assessing outcomes in patients surviving beyond 6 months, the 2-year OS and PFS in the bortezomib group were 77.3% and 65.8%, respectively. Conclusions: Bortezomib-based regimens can help to reduce early mortality and improve long-term survival in patients with ultra-high-risk AL amyloidosis.

Multiorgan involvement by amyloid light chain amyloidosis

Amyloid light chain (AL) amyloidosis is a protein conformational disease. AL amyloidosis results from aggregation of misfolded proteins that are deposited in tissues as amyloid fibrils. Diagnosis of AL amyloidosis can be challenging due to its low incidence and clinical complexity. Therapy requires a risk-adapted approach involving dose reductions and schedule modifications of chemotherapy regimens along with close monitoring of hematologic and organ responses. We herein describe a patient whose condition was diagnosed as systemic AL amyloidosis and presented with splenic rupture as the initial symptom. Congo red staining of the kidney biopsy was positive. The normal structure of the liver and spleen had been replaced by amyloid deposition. The chemotherapy strategy involved a combination of bortezomib, cyclophosphamide, thalidomide, and dexamethasone.

Diagnosis of cardiac amyloidosis: a systematic review on the role of imaging and biomarkers

BACKGROUND

Cardiac Amyloidosis (CA) pertains to the cardiac involvement of a group of diseases, in which misfolded proteins deposit in tissues and cause progressive organ damage. The vast majority of CA cases are caused by light chain amyloidosis (AL) and transthyretin amyloidosis (ATTR). The increased awareness of these diseases has led to an increment of newly diagnosed cases each year.

METHODS

We performed multiple searches on MEDLINE, EMBASE and the Cochrane Database of Systematic Reviews. Several search terms were used, such as "cardiac amyloidosis", "diagnostic modalities cardiac amyloidosis" and "staging cardiac amyloidosis". Emphasis was given on original articles describing novel diagnostic and staging approaches to the disease.

RESULTS

Imaging techniques are indispensable to diagnosing CA. Novel ultrasonographic techniques boast high sensitivity and specificity for the disease. Nuclear imaging has repeatedly proved its worth in the diagnostic procedure, with efforts now focusing on standardization and quantification of amyloid load. Because the latter would be invaluable for any staging system, those spearheading research in magnetic resonance imaging of the disease are also trying to come up with accurate tools to quantify amyloid burden. Staging tools are currently being developed and validated for ATTR CA, in the spirit of the acclaimed Mayo Staging System for AL.

CONCLUSION

Cardiac involvement confers significant morbidity and mortality in all types of amyloidosis. Great effort is made to reduce the time to diagnosis, as treatment in the initial stages of the disease is tied to better prognosis. The results of these efforts are highly sensitive and specific diagnostic modalities that are also reasonably cost effective.

Localized conformational changes trigger the pH-induced fibrillogenesis of an amyloidogenic λ light chain protein

Solvent conditions modulate the expression of the amyloidogenic potential of proteins. In this work the effect of pH on the fibrillogenic behavior and the conformational properties of 6aJL2, a model protein of the highly amyloidogenic variable light chain λ6a gene segment, was examined. Ordered aggregates showing the ultrastructural and spectroscopic properties observed in amyloid fibrils were formed in the 2.0-8.0 pH range. At pH <3.0 a drastic decrease in lag time and an increase in fibril formation rate were found. In the 4.0-8.0 pH range there was no spectroscopic evidence for significant conformational changes in the native state. Likewise, heat capacity measurements showed no evidence for residual structure in the unfolded state. However, at pH <3.0 stability is severely decreased and the protein suffers conformational changes as detected by circular dichroism, tryptophan and ANS fluorescence, as well as by NMR spectroscopy. Molecular dynamics simulations indicate that acid-induced conformational changes involve the exposure of the loop connecting strands E and F. These results are compatible with pH-induced changes in the NMR spectra. Overall, the results indicate that the mechanism involved in the acid-induced increase in the fibrillogenic potential of 6aJL2 is profoundly different to that observed in κ light chains, and is promoted by localized conformational changes in a region of the protein that was previously not known to be involved in acid-induced light chain fibril formation. The identification of this region opens the potential for the design of specific inhibitors.