Chromothripsis in Treatment Resistance in Multiple Myeloma

Multiple myeloma (MM) is a malignant disease caused by an abnormal proliferation of plasma cells, of which the prognostic factors include chromosomal abnormality, β-2 microglobulin, and albumin. Recently, the term chromothripsis has emerged, which is the massive but highly localized chromosomal rearrangement in response to a one-step catastrophic event. Many studies have shown an association of chromothripsis with the prognosis in several cancers; however, few studies have investigated it in MM. Here, we studied the association between chromothripsis-like patterns and treatment resistance or prognosis. First, we analyzed nine MM cell lines (U266, MM.1S, RPMI8226, KMS-11, KMS-12-BM, KMS-12-PE, KMS-28-BM, KMS-28-PE, and NCI-H929) and bone marrow samples of four patients who were diagnosed with MM by next-generation sequencing-based copy number variation analysis. The frequency of the chromothripsis-like pattern was observed in seven cell lines. We analyzed the treatment-induced chromothripsis-like patterns in KMS-12-BM and KMS-12-PE cells. As a result, breakpoints and chromothripsis-like patterns were increased after drug treatment in the relatively resistant KMS-12-BM. We further analyzed the patients’ results according to the therapeutic response, which was divided into sensitive and resistant, as suggested by the International Myeloma Working Group. The chromothripsis-like pattern was more frequently observed in the resistant group. In the sensitive group, the frequency of the chromothripsis-like pattern decreased after treatment, whereas the resistant group showed increased chromothripsis-like patterns after the treatment. These results suggest that the chromothripsis-like pattern is associated with treatment response in MM.

Chromothripsis Identified by Copy Number Profiling in a Case of Plasma Cell Leukaemia / 임상검사와정도관리

A genomic instability called chromothripsis occurs as a single catastrophic event, generating massive complex genomic rearrangement with a possible characteristic pattern of copy number oscillations. Here, we report a case of secondary plasma cell leukaemia (PCL) showing chromothripsis identified by single nucleotide polymorphism array (SNP-A)-based karyotyping. A 53-year-old male patient was diagnosed as having secondary PCL four years after he was diagnosed with multiple myeloma, and he died four days later due to intracerebral haemorrhage. Chromosomal analysis and fluorescence in situ hybridization (FISH) revealed the deletions of 13q and 17p and an insertion of 1q. Further, genomic aberrations that were not detected by chromosomal analysis and FISH were identified by SNP-A. In particular, SNP-A revealed numerous alternating copy number state switches involving one, two, or three copy number states on chromosome 7q, suggesting the presence of chromothripsis. The present case suggests that chromothripsis may occur in secondary PCL and can be inferred from genomic copy number profiles identified by SNP-A.