[The relationship between copy number and microsatellite instability of mitochondrial DNA in colorectal cancer].

Objective: To study the relationship between the abnormality of mitochondrial DNA (mtDNA) copy number and the clinical parameters and microsatellite instability (MSI) in colorectal cancer.

Methods: Total DNA was extracted from cancer and pericancer tissue from 50 colorectal cancer (CRC) biopsy samples. Non-coding region sequencing was done and the copy number of mtDNA was quantitated with real-time PCR in mitochondrial ND1 gene. The relationship between clinical indicators, mtMSI and mitochondrial copy number was detected.

Results: The mean copy number of mtDNA 312 +/- 185 in the tumor tissue was significantly lower than that 525 +/- 125 of the corresponding non-tumor tissue of these patients (P < 0.001). No significant correlation was found between mtDNA copy number and other variables including age, gender, pathological type and clinical stage (P > 0.05). However, there was a significant correlation between copy number and mtMSI (P < 0.001).

Conclusion: There is a significant reduction of mtDNA in CRC patients, which may be caused by mtMSI.