Abstract: Objective To explore the expression of inducible T cell costimulatory molecules in colon cancer tissues and their correlation with long-term survival of colon cancer patients. Methods A total of 206 colon cancer patients who underwent surgical resection of colon tissue in Xinhua Hospital Affiliated to Dalian University from May 2018 to May 2019 were selected. Their colon cancer tissues and paracancerous tissues were used for the detection of inducible T-cell co-stimulator (ICOS) expression by fluorescence quantitative PCR. The relationships between the expression level of ICOS and the clinicopathological characteristics or the long-term survival were analyzed. Results The expression level of ICOS was significantly lower in colon cancer tissues (8. 73 ± 2. 25) than that in adjacent tissues (18. 54 ± 3. 26) (P< 0. 05). The expression level of ICOS in colon cancer tissues was related to tumor diameter, distant metastasis, clinical stage, lymph node metastasis (P< 0. 05), and no relation was found between ICOS expression level and age, gender, tumor location, and degree of differentiation (P > 0. 05). The expression level of ICOS in 206 colon cancer tissues was low in 117 cases, and high in 89 cases. Logistic regression analysis showed that ICOS expression was related to tumor size, clinical stage, lymph node metastasis, and distant metastasis (P< 0. 05), but not related to age, gender, lymph node metastasis, tumor location, and degree of differentiation (P > 0. 05). The 206 colon cancer patients were followed up until September 30, 2021, the survival rate was 83. 01 % (171 / 206), the mortality rate was 16. 99 % (35 / 206), and the median survival time was (23. 5 ± 3. 3) months. The median survival time of the 89 colon cancer patients with high expression level of ICOS was (27. 4 ± 3. 2) months, with a 95 % CI of 2. 24-6. 147. The median survival time of the 117 colon cancer patients with low expression level of ICOS was (16. 3 ± 4. 3) months, and the 95 % CI was 1. 458-5. 237. The median survival time of colon cancer patients with high expression level of ICOS was significantly higher than that of patients with low expression level of ICOS (P<0. 05). Conclusion ICOS is lowly expressed in colon cancer tissues, and its expression level is positively correlated with the long-term survival of patients. The expression level of ICOS can be used as an important evaluation index for the prognosis and survival of colon cancer patients.

Key words: inducible T cell costimulatory molecules, colon cancer, long-term survival, correlation