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Relationship between COX-2 expression and clinicopathological features of colorectal cancers
Jun Zhan1, Jian-ping Liu, Zhao-hua Zhu
1Department of Gastroenterology, The Second Affiliated Hospital, Sun Yat-Sen University, Guangzhou 510120, China.
Background:
Cyclo-oxgenase 2 (COX-2) is involved in prostaglandin synthesis in central nervous system, and it also plays a role in human carcinogenesis. Our purpose of this study is to investigate the COX-2 expression in different development stages of colorectal cancer, and to discuss the relationship between the gene expression and clinicopathological features of the cancer.
Methods:
COX-2 expression was examined by immunohistochemical staining in 76 surgical specimens of colorectal cancer (44 of advanced stage and 32 of early stage), thirty-three adenomas and 18 normal colonic mucosal tissues taken by endoscopic biopsy. Kaplan-Meier survival curves and Cox proportional hazards regression were used to evaluate the relation of COX-2 to prognosis.
Results:
COX-2 expression, divided into 4 grades from "-" to "+++", is respectively 83.3%, 16.7%, 0% and 0% in normal colonic mucosal tissues; 12.1%, 42.4%, 36.4% and 9.1% in adenomas; 6.3%, 28.1%, 46.9% and 18.7% in early colorectal cancers (ECCs), and 6.8%, 20.5%, 18.2% and 54.5% in advanced colorectal cancers (CRCs). The differences in COX-2 expression between advanced CRCs and early colorectal cancers (ECCs) as well as between the advanced CRCs and adenomas were statistically significant (P < 0.01); but there was no significant difference between ECCs and adenomas. Kaplan-Meier survival analysis showed a significant difference in the survival curves between low high COX-2 groups (P < 0.05). Cox proportional hazards regression showed that COX-2 expression was related to poorer long-term outcome with a hazard ratio of 2.665 unadjusted for other variables (P < 0.05), and COX-2 expression was an independent risk factor of poor prognosis.
Conclusions:
COX-2 expression is gradually up-regulated in the development from normal epithelium to adenomas and from ECCs to advanced CRCs. Alhough the COX-2 protein can not be regarded as a tumor marker to diagnose CRCs early, COX-2 expression can be regarded as an independent risk factor of poor prognosis for postoperative patients with advanced CRCs.
