A functional assay to identify amyloidogenic light chains

Abstract

Introduction: Multiple myeloma (MM) and light chain monoclonal gammopathy of undetermined significance (LCMGUS) are plasma cell disorders associated with the secretion of monoclonal free light-chain (LC) proteins. Due to the high concentrations of LC in circulation, both of these populations are at risk for developing LC-associated amyloidosis (AL) – a protein misfolding disease characterized by the deposition of LC protein fibrils in organs and tissues, leading to dysfunction and significant morbidity. At present, accurate identification of subjects at risk for developing amyloidosis is not possible, but with the advent of novel, amyloid-targeted therapies, identification of pre-symptomatic individuals is of clinical import.

Methods: To address this, a competition assay has been developed to discern LC proteins with enhanced amyloidogenic potential. Numerous factors that may influence the efficacy of the assay have been evaluated to yield optimal conditions.

Results: Using a panel of nine patient-derived LC, we have demonstrated that amyloid-associated LC inhibited the recruitment of a biotinyl-λ6 variable domain by homologous amyloid-like fibrils significantly more than MM LC (p < .01).

Conclusion: The assay accurately discriminated AL from MM patient populations, suggesting that it may aid in the identification of patients with monoclonal gammopathies who have an increased risk of developing amyloidosis.

Keywords:

• Light-chain amyloidosis
• multiple myeloma
• light-chain protein
• risk assessment
• assay

Acknowledgements

We appreciate the thoughts and comments provided by Dr. Raymond Comenzo. We thank Matthew Little for assistance in the production of rVλ6Wil protein.

Disclosure statement

EBM and JSW are co-inventors named on a PCT patent application (claiming priority from U.S. Provisional Patent Application No. 62/326,671, filed April 22, 2016, which is titled “Methods & Systems for Identifying Amyloidogenic Proteins”) related to the development of an assay to identify subjects with a high risk of developing amyloidosis in susceptible populations. The remaining authors report no conflicts of interest.

Additional information

Funding

This study was supported by a Research Grant from the Amyloidosis Foundation (AF). Additional support was provided by the Department of Medicine at the University of Tennessee Medical Center.