Expression of cyclooxygenase-2 and vascular endothelial growth factor in primary central nervous system lymphomas

Cyclooxygenase (COX) is the rate-limiting enzyme that catalyzes the initial step in biosynthesis of prostaglandins (PGs) from arachidonic acid. COX-2 has been associated with inflammatory processes and tumorigenesis. In order to investigate the correlation between VEGF, COX-2 expression, and tumorigenesis in primary central nervous system lymphomas (PCNSLs), the present study assessed 26 cases of PCNSL by immunostaining for VEGF and COX-2. Immunohistochemical studies were evaluated as follows: (-), no staining; (1+), 0-30% positive cells; (2+), 30-60% positive cells; (3+), >60% positive cells. VEGF expression was detected in 21 of 26 cases; of these, 14, 1 and 6 were scored as 3+, 2+ and 1+, respectively. COX-2 expression was detected in 22 of 26 cases; of these, 14, 4 and 4 were scored as 3+, 2+ and 1+, respectively. For double immunofluorescence, 20 of 26 cases that were detected with both VEGF and COX-2 were examined and almost all tumor cells coexpressed both VEGF and COX-2 in the examined cases. However, COX-2 and VEGF expression in PCNSLs did not correlate with neoangiogenesis and patient survival in the present study, in contrast to previous findings in systemic lymphomas. It is suggested that the high frequency of COX-2 and VEGF coexpression in PCNSLs may be associated with tumorigenesis of PCNSLs and could possibly lead to a future therapeutic trial of PCNSLs with selective COX-2 inhibitor therapy.