Tracking Clonal Evolution of Multiple Myeloma Using Targeted Next-Generation DNA Sequencing

Abstract

Clonal evolution drives treatment failure in multiple myeloma (MM). Here, we used a custom 372-gene panel to track genetic changes occurring during MM progression at different stages of the disease. A tumor-only targeted next-generation DNA sequencing was performed on 69 samples sequentially collected from 30 MM patients. The MAPK/ERK pathway was mostly affected with KRAS mutated in 47% of patients. Acquisition and loss of mutations were observed in 63% and 37% of patients, respectively. Four different patterns of mutation evolution were found: branching-, mutation acquisition-, mutation loss- and a stable mutational pathway. Better response to anti-myeloma therapy was more frequently observed in patients who followed the mutation loss—compared to the mutation acquisition pathway. More than two-thirds of patients had druggable genes mutated (including cases of heavily pre-treated disease). Only 7% of patients had a stable copy number variants profile. Consequently, a redistribution in stages according to R-ISS between the first and paired samples (R-ISS″) was seen. The higher the R-ISS″, the higher the risk of MM progression and death. We provided new insights into the genetics of MM evolution, especially in heavily pre-treated patients. Additionally, we confirmed that redefining R-ISS at MM relapse is of high clinical value.

Liquid biopsy-based monitoring of residual disease in multiple myeloma by analysis of the rearranged immunoglobulin genes–A feasibility study

“…Due to the particular characteristics of this process, each mature B-cell and their terminally differentiated descendants, the plasma cells, encode exactly one pair of unique immunoglobulin heavy chain and light chain [63,64]. As multiple myeloma cells are malignantly transformed postgerminal lymphoid cells, they also carry unique immunoglobulin sequences [5,64], that is shown to be largely stable during the course of this disease [33][34][35], unlike most mutated or driver genes which are subject to intense (sub)clonal evolution [11,26,34,53,65], which even increases due to treatment pressure [20,66]. Thus, it is crucial for our analysis to identify the myeloma specific CDR3 sequence of each patient.…”

Molecular and immunological mechanisms of clonal evolution in multiple myeloma

“…After disease initiation, the clonal evolution most often follows a branching pattern, where multiple heterogeneous clones develop independently and distinct mutations are lost or gained in the course of MM progression. Less frequently, the clonal structure persists between early and late disease stages, referred as a stable evolutionary pattern (69,70). Notably, clonal heterogeneity can be found throughout all steps of myeloma progression starting from MGUS (71,72).…”

CRL4CRBN E3 Ligase Complex as a Therapeutic Target in Multiple Myeloma

“…Recent molecular studies with lenalidomide- and pomalidomide-resistant MM patients revealed some CRBN molecular alterations (e.g., point mutation, structural variation, copy loss, or exon 10 spliced transcript of CRBN) associated with IMiDs’ exposure [ 26 ]. Nevertheless, the low frequency and clonal fraction of identified CRBN mutations cannot be responsible for IMIDs resistance in the majority of patients [ 27 , 28 ]. As IMiDs resistance is one of the main challenges in MM treatment, its mechanism of resistance needs to be explored in future studies.…”