Abstract
ObjectiveThis study aims to screen the MSI detection loci suitable for the East Asian colorectal cancer patients. and explore its intratumoral heterogeneity.MethodsA total of 271 pathological tissues specimens of colorectal cancer were collected. The MSI status was detected using different PCR reagent kits with different detection loci. Then, the results were compared with the immunohistochemical (IHC) staining results. Microdissection of pathological tissues specimens detected to be MSI‐H was performed to examine whether there was intratumoral heterogeneity of MSI status.ResultsThirty‐nine out of 271 cases were dMMR. dMMR occurred mostly in patients with right‐hemi colon cancer (P < 0.0001). Compared with dMMR patients, the clinical stages of pMMR patients were more inclined to be in the late stage with lymph node metastasis (P < 0.0001). MSI‐H tumors were significantly associated with KRAS mutation (P = 0.036) and PD‐L1 expression (P = 0.038). Compared with Promega panel and 24‐locus detection, the consistency between NCI MSI panel and IHC staining results were the highest with the Kappa value of 0.850. The sensitivity of detection decreased from 87.18% to 56.41% with the increase in detection loci. Single locus analysis showed that the first two loci with the highest sensitivity were both mononucleotide loci, namely, BAT‐26 (95.45%) and BAT‐25 (86.36%). The dinucleotide locus with highest sensitivity was D2S123 (50%). The main detection loci of MSI‐H showed no intratumoral heterogeneity.ConclusionThe combination of 2 mononucleotide loci (BAT25, BAT26) and 3 dinucleotide loci (D2S123, D5S346, D17S250) might be the most suitable loci for MSI detection in East Asian population. There is no intratumoral heterogeneity in the main MSI loci.
Highlights
There may be significant differences in the genetic landscape, the response to chemotherapy and immunotherapy, as well as the classification and staging of tumors due to different status of microsatellite instability (MSI)
This study aims to screen the MSI detection loci suitable for the East Asian colorectal cancer (CRC) patients, and to explore the intratumoral
The screening of 2 major groups of MSI loci is predominantly based on the study of Caucasian population
Summary
This study was funded by the Major Research and Development Project of Shanxi Science and Technology Department of Shanxi (grant number: 201603 D321049) and the Scientific Research Task of the Shanxi Health and Family Planning Commission of Shanxi (grant number: 2014052).
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