DNA mismatch repair pathway defects in the pathogenesis and evolution of myeloma

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Genetic instability is a hallmark of multiple myeloma (MM).
• Disease progression from monoclonal gammopathy of uncertain significance (MGUS) and smouldering myeloma (SMM) correlates with accumulating molecular and chromosomal abnormalities.
• The DNA mismatch repair (MMR) pathway is crucial for maintaining genomic stability by correcting replication errors.

Purpose of the Study:

• To investigate the proficiency of the MMR pathway in plasma cell dyscrasias.
• To determine if MMR pathway defects are associated with disease progression in multiple myeloma.

Main Methods:

• Microsatellite analysis was performed on 92 clinical samples (MGUS/SMM, MM/plasma cell leukaemia (PCL), relapsed MM/PCL).
• An in vitro heteroduplex G/T repair assay was used to assess MMR proficiency in cell lines and PCL cases.
• Aberrant expression of MMR proteins was evaluated.

Main Results:

• Microsatellite instability was detected in 15 out of 92 patients (16.3%).
• Instability rates were 7.7% in MGUS/SMM, 20.7% in MM/PCL, and 12.5% in relapsed MM/PCL.
• Reduced MMR repair was observed in two cell lines and two PCL cases, linked to aberrant MMR protein expression.

Conclusions:

• Defects in the DNA mismatch repair pathway are present in plasma cell dyscrasias.
• The increased frequency of MMR defects in more advanced disease stages suggests a role in multiple myeloma progression.