Microsatellite instability detection

Fig 1. Example of microsatellite instability at the locus D17S796 in twenty subclones of the cisplatin resistant cell line A2780/cp70. The PCR products were fractionated on a 6% denaturing polyacrylamide gel and detected by autoradiography. The first four lanes show the M13 sequencing ladder used as a molecular-weight marker. Reproduced with authors permission. 

Once the PCR procedure is complete, the products of amplification should be visualized for analysis and interpretation. Agarose gel electrophoresis and ethidium bromide staining can achieve this however, they cannot separate amplification products that differ in size by only a few nucleotides. Polyacrylamide gel electrophoresis or capillary gel electrophoresis can achieve a finer separation (Fig 2.3A,B). PCR amplification followed by gel electrophoresis is frequently used for detection of small deletions or insertions, microsatellite instability, and LOH. For detection of point mutations, the PCR products should be interrogated by other molecular techniques. 

FIGURE 2.15 Detection of microsatellite instability using the NCI recommended panel of five microsatellite markers. In this colon cancer sample, all five markers show microsatellite instability, which manifests as change in size of microsatellite repeats seen on capillary gel electropherograms of tumor PCR products. Electropherograms of normal tissue PCR products are used as a negative control. 

Boland CR, Thibodeau SN, Hamilton SR, et al. A National Cancer Institute Workshop on Microsatellite Instability for cancer detection and familial predisposition development of international criteria for the determination of microsatellite instability in colorectal cancer. Cancer Res. 1998 58 5248-5257. 

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