OBJECTIVETo investigate the proportion between tumors which maintain their telomeres by a mechanism of alternative lengthening of telomeres(ALT) and telomerase-dependent tumors in gastrointestinal malignant tumors, the expression difference of hRad21 between the two groups and the clinicopathological characteristics of ALT tumors were also explored.

METHODSOne hundred and four cases of gastrointestinal malignant tumors were divided into 2 groups: ALT group and telomerase group by detecting telomerase activity using TRAP method. Expression difference of hRad21 was investigated between the two groups. All the patients were followed up and clinicopathological data of these patients were analyzed.

RESULTSOf 104 cases, there were 12 cases in ALT group and 94 cases in telomerase group. Expression of hRad21 in ALT group was higher than that in telomerase group. Tumors in ALT group had a thinner invasion depth (lower T stage) as compared to telomerase group (P=0.021). Other indexes, such as age, gender, tumor size, tumor grade, location of tumor, CEA and CA199, were not significantly different between the two groups. Results of follow-up showed that the survival rate of ALT group was 100% while that of telomerase group was 56% at 30 months postoperatively.

CONCLUSIONSThere are tumors which maintain their telomeres by ALT in gastrointestinal malignant tumors, accounting for 10%-12% of the total tumors. As compared to telomerase group, ALT group presents higher expression of hRad21, thinner tumor invasion depth, and higher survival rate.