FcγRIIIA Genotype in Plasma Cell Dyscrasias Is Associated with Clinical Progression, Bone Disease Extension and...

Background/Objectives: FcγRIIIA presents a single nucleotide polymorphism at position 158 (V/F), which affects its binding affinity to the fragment crystallizable (Fc) of antibodies (Abs). In the presence of immune complexes, FcγRIIIA can mediate the inflammatory signaling, severity of bone disease, and osteoclastogenic activity. Based on this functional relevance, we hypothesized that the FcγRIIIA F158V polymorphism may influence the clinical presentation of multiple myeloma (MM). Methods: FcγRIIIA F158V genotyping was performed on genomic DNA extracted from peripheral blood samples of patients affected by MM or asymptomatic conditions named MGUS and SMM. We compared the allele frequency of FcγRIIIA-F158V polymorphism in 72 MM, 42 MGUS and 31 SMM and evaluated the association with clinical features and occurrence of high-risk chromosome abnormalities. Targeted NGS mutation analysis was performed on genomic DNA isolated from purified CD138⁺ bone marrow plasma cells (BMPCs) of 41 patients, to evaluate the association between somatic mutations and the FcγRIIIA F158V genotype. Results: the FcγRIIIA-158 V/V homozygous genotype was associated with high-risk cytogenetics, anemia, high beta-2 microglobulin levels, and more than 10 osteolytic lesions. V/V homozygous genotype was significantly associated with at least one mutation in RAS pathway genes (N-RAS, K-RAS or B-RAF). In the immune microenvironment, patients carrying the V/V homozygous genotype had a higher percentage of CD14⁺CD16⁺⁺ non-conventional inflammatory monocytes than the V/F or FF genotype. Conclusions: Our study contributes to a better understanding of the interactions between genetic variants, tumor microenvironment, and therapeutic response in plasma cell dyscrasias, to identify molecular biomarkers for precision medicine in MM, MGUS and SMM.