There are two commonly accepted methods for detecting microsatellite status: the one is to detect amplified microsatellite loci by polymerase chain reaction (PCR), and the other is to detect mismatch repair gene (MMR) proteins expression by immunohistochemistry(IHC). The PCR detection is considered to have accuracy in clinic, while the IHC is widely used because of its easier operation and cheaper expense.
In order to compare IHC with PCR in detecting the microsatellite status in colorectal carcinoma, A total of 569 samples of colorectal carcinoma resection were collected in Department of Pathology, Nanjing Drum Tower Hospital between June 2014 and June 2017, all samples were used IHC and PCR to detect microsatellite status, the consistency of results between the two methods was compared.
We found that 48 cases of microsatellite instability (MSI) were detected by PCR, including 37 cases of microsatellite instability high (MSI-H), 11 cases of microsatellite instability low (MSI-L) and 521 cases of MSS. MSI accounted for 8.44% of all cases, of which the MSI-H accounted for 6.50%.The IHC results of 569 patients showed that 69 cases were deficient mismatch repair (dMMR), 500 cases were proficient mismatch repair (pMMR), dMMR accounted for 12.13% of all cases. The loss expression of PMS2 protein was the most common while the MSH6 was rare. The coincidence rate of the two methods for detecting microsatellite states was 91.92%.
IHC and PCR method had high consistency in microsatellite status. Compared with PCR, IHC method is more economical, convenient for clinical operations. When the 4 repair proteins were without missing detected by IHC, it can be diagnosed as MSS / MSI-L, further PCR was not necessary, and when any repair protein is found to be deficient, PCR detection was needed to determine whether there existed MSI. Our conclusion will save a lot of time and cost for clinical work.
Clinical trial identification
Legal entity responsible for the study
The Comprehensive Cancer Center of Drum Tower Hospital, Medical School of Nanjing University& Clinical Cancer Institute of Nanjing University.
National Natural Science Foundation of China; Nanjing Medical Science and Technique Development Foundation.
All authors have declared no conflicts of interest.