Experimental study of the association between the microsatellite instability and thyroid carcinoma

Objective To investigate the relationship between the Microsatellite Instability(MSI) and the clinicopathological features as well as the prognosis in patients with thyroid carcinoma.Methods The expression of MSI was analyzed by detecting THRA1,D2S123,D11S912,BAT-26 using polymerase chain reaction(PCR) in 30 cases of thyroid carcinoma and 30 cases of normal tissues.The postoperative course and survival rates were compared among patients with and without MSI,and 5 year survival rate were counted.Results The most frequent MSI was observed at THRA1 with an incidence of 43.3%(13/30),MSI on D2S123 was detected in36.7%(11/30) of the tumors.In follicular cancer,MSI in D2S123 occurred at a frequency of 100%(6/6) with no(0%) occurrence of MSI at the nearby BAT-26 loci.MSI was detected about 26.7%(8/30) on D18S58.BAT-26,which is an important marker in colorectal cancer,displayed the lowest frequency of MSI in our panel of thyroid tumors 6.7%(2/30).Follow-up survey 5 years after the operation,it was found that the patients with MSI-positive cancer showed longer survival period compared with those with MSI negative cancer.The high frequency of MSI can be detected at both 2p and 18q loci.The link between MSI in D2S123 and follicular carcinoma was statistically significant,and there was a significant correlation between MSI in D18S58 and patients' age as well as the stage of tumor.Lowest frequency of MSI in BAT-26 was found in thyroid,which is different from that in colorectal cancer.Conclusion MSI leads to the instability of the genome,which has the notable significance in the occurance of the thyroid tumors.Patients with MSI positive cancer showed longer survival period than those with MSI negative cancer.