Mutational landscape reflects the biological continuum of plasma cell dyscrasias

Abstract

We subjected 90 patients covering a biological spectrum of plasma cell dyscrasias (monoclonal gammopathy of undetermined significance (MGUS), amyloid light-chain (AL) amyloidosis and multiple myeloma) to next-generation sequencing (NGS) gene panel analysis on unsorted bone marrow. A total of 64 different mutations in 8 genes were identified in this cohort. NRAS (28.1%), KRAS (21.3%), TP53 (19.5%), BRAF (19.1%) and CCND1 (8.9%) were the most commonly mutated genes in all patients. Patients with non-myeloma plasma cell dyscrasias showed a significantly lower mutational load than myeloma patients (0.91±0.30 vs 2.07±0.29 mutations per case, P=0.008). KRAS and NRAS exon 3 mutations were significantly associated with the myeloma cohort compared with non-myeloma plasma cell dyscrasias (odds ratio (OR) 9.87, 95% confidence interval (CI) 1.07-90.72, P=0.043 and OR 7.03, 95% CI 1.49-33.26, P=0.014). NRAS exon 3 and TP53 exon 6 mutations were significantly associated with del17p cytogenetics (OR 0.12, 95% CI 0.02-0.87, P=0.036 and OR 0.05, 95% CI 0.01-0.54, P=0.013). Our data show that the mutational landscape reflects the biological continuum of plasma cell dyscrasias from a low-complexity mutational pattern in MGUS and AL amyloidosis to a high-complexity pattern in multiple myeloma. Our targeted NGS approach allows resource-efficient, sensitive and scalable mutation analysis for prognostic, predictive or therapeutic purposes.

Figure 1

Panel of genes and hot spot regions covered by the next-generation sequencing panel including previously identified alterations. Alteration type and location of mutations in NRAS, KRAS, FAM46C, CCND1, IRF4, BRAF, CYLD, TP53, NFKB1 and LTB genes previously identified in multiple myeloma are shown. Red bars indicate regions chosen for hot spot sequencing. AD, transactivation domain; ANK, ankyrin domain; BD, binding domain; CAP-Gly, cytoskeleton-associated protein glycine-rich; DAG, diacilglycerol; NTP_transf_7, nucleotidyltransferase; p-loop NTY, containing nucleoside triphosphate hydrolase; Ph, phorbol-ester/DAG-type; RBD, ras binding domain; PK, protein kinase; RHD, real like domain; TD, tetramerization domain; TNF, tumor necrosis factor domain.

Figure 2

Mutated clones detected by NGS in the MGUS, AL amyloidosis and myeloma cohorts. Genes regulating cell proliferation (red circles), stress and inflammatory response (green circles), apoptosis (blue circles) and protein translation (orange circles) are shown.

Figure 3

Differences in the mutational load between disease categories. (a) Difference in mutational frequency (number of mutant exons per patient) between myeloma and non-myeloma plasma cell dyscrasias. (b) Difference in percentage of patients with mutations (⩾1 mutation per case) between myeloma and non-myeloma plasma cell dyscrasias.