Microsatellite instability (MSI) is a form of genomic instability. It is caused by the insertion or deletion of repeating bases (called microsatellites) during DNA replication and the failure of the mismatch repair system (MMR) to correct these errors.
CD Genomics employs Promega kit which is a fluorescent multiplex PCR-Capillary Electrophoresis based method to detect the MSI status. Typically, the MSI analysis system includes allelic profiles of microsatellite markers comparison, involving five nearly monomorphic mononucleotide repeat markers (BAT-25, BAT-26, MONO-27, NR-21 and NR-24) and two highly polymorphic pentanucleotide repeat markers (Penta C and Penta D), which are quality control for sample authentication of matched normal and tumor. For MSI detection, tumor and normal tissues from each patient need to be analyzed in parallel. Generally, MSI detection in ≥ 30-40% of the markers is considered to be MSI-high (MSI-H), whereas that in < 30-40% of the markers is considered MSI-low (MSI-L), or MSS if no marker is unstable.
Key Features and Applications
MSI Analysis Workflow:
1) 5 mL peripheral blood in EDTA tube
2) 5-6 FFPE tissue slides or block containing only non-tumor tissue
3) We can attempt to isolate non-tumor tissue from the tumor specimen submitted in cases no alternative tissue is available
FFPE tissue (paraffin block is preferred).
Note: Additional normal, non-tumor tissue sample from the same source individual is required for comparison testing in MSI Analysis.
Using Applied Biosystems® 3500 xL Genetic Analyzer.