Cyclooxygenase-2 (COX-2) overexpression in childhood brain tumors

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An overexpression of COX enzymes has been demonstrated in human neoplasms at various sites, including the colon, gastrointestinal tract, lung, skin, and recently in brain tumors. In this study, we attempted to detect COX-2 receptor overexpression in primary childhood brain tumors and to observe the distribution pattern of COX-2 receptors. We used a sensitive, four-step, alkaline phosphatase conjugated antigen detection technique and employed a specific monoclonal antibody in anaplastic, high-grade astrocytomas (ASTRs) and in glioblastoma multiformes (GMs). Of the 14 MEDs/PNETs we observed, all of them demonstrated high levels of immunoreactivity (overexpression) with the highest immunostaining intensity grades A and B. However, of the 14 subtypes of astrocytic tumors we examined, COX-2 receptor expression level was nowhere near that of the MEDs/PNETs levels but was nonetheless significant when comparing low grade pilocytic ASTRs to high grade anaplastic ASTRs and glioblastomas. In two low grade pilocytic ASTRs the expression level never exceeded 20 per cent while in high grade glial tumors (in 6 anaplastic ASTRs and 6 glioblastomas) 30 to 50 per cent of the tumor cells overexpressed COX-2 receptors. As evidenced by our results, COX-2 receptor overexpression seems to increase as the grade of the astrocytic tumor increases. As such, COX-2 inhibitors may represent a novel chemo-preventive tool in treating childhood brain tumors, which are now the leading cause of solid tumor cancer death in children under the age of 20, surpassing acute lymphoblastic leukemia.