Laboratory-Based Rationale for Targeting the Protein Homeostasis Network in AL Amyloidosis

Abstract

AL amyloidosis is an incurable plasma cell dyscrasia with limited therapeutic options. The pathogenetic mechanism in AL amyloidosis is the deposition of insoluble fibrillary aggregates of misfolded immunoglobulin (Ig) free light chains (FLC) and chaperone proteins in target organs. Therefore, AL amyloidosis is the prototypic, protein-toxicity hematologic disorder. Based on laboratory evidence of increased, constitutive proteotoxic stress, PCs are intrinsically vulnerable to agents that target proteins whose function is to guarantee that nascent polypeptides either reach a functional conformation or are disposed of (proteostasis network). The clinical efficacy of proteasome inhibitors (PIs), such as bortezomib, in the treatment of plasma cell (PC) disorders has provided proof of concept that disrupting protein homeostasis is an effective and generally safe therapeutic approach. Therefore, the intrinsic biology of PC offers us the opportunity to rationally develop therapies that target this distinct proteostasis vulnerability of PC dyscrasias. In this manuscript, we will review the laboratory rationale for the effectiveness of FDA-approved and investigational agents targeting protein homeostasis in AL amyloidosis and related PC disorders.

Keywords

• AL amyloidosis
• proteostasis network
• ubiquitin–proteasome system
• therapeutic targets
• proteotoxicity
• protein degradation