Correlation between cyclooxygenase-2 expression and HuR cytoplasmic translocation of breast cancer

Background: Embryonic lethal abnormal vision (ELAV)-like protein HuR is known to stabilize mRNA through binding AU-rich elements in the 3′-untranslated region. Recent studies show that HuR expression is associated with the expression of several genes including cyclooxy-genase-2 (COX-2). HuR exists predominantly in the nucleus, but cytoplasmic translocation of HuR is thought to be more important for its activity. COX-2 is a well-known enzyme that promotes tumor growth. Methods: To evaluate the correlation of HuR and COX-2 expression, we analyzed expression of HuR and COX-2 in 91 cases of breast cancer using immunohistochemistry. Results: Nuclear and cytoplasmic expression of HuR was seen in 76 (83.5%) and 19 (20.9%) of 91 cases respectively. COX-2 immunoreactivity was seen in 54 (59.4%) cases. Cytoplasmic HuR expression showed significant correlation with COX-2 expression (p=0.001). Nuclear HuR showed no correlation with COX-2 expression or other clinicopathological parameters. COX-2 expression is significantly associated with tumor grade (p=0.028). COX-2 (p=0.092) and cytoplasmic (p=0.569) and nuclear HuR (p=0.247) expression showed no correlation with survival. Conclusions: These results suggest that cytoplasmic HuR expression is associated with COX-2 expression in breast cancer and cytoplasmic location of HuR might contribute to the stabilization of COX-2 mRNA.