Objectives: Cyclooxygenase 2 (COX-2) is aberrantly expressed in multiple tumor types including bladder cancer and is associated with enhanced growth, resistance to apoptosis, invasion, and angiogenesis. To evaluate the mechanisms through which COX-2 expression alters normal urothelium, we transfected the SV-40 immortalized human urothelial cell line SV-HUC with COX-2.
Methods: SV-HUC cells were stably transfected with a plasmid containing COX-2 under a CMV promoter. Following isolation of monoclonal transfectants, COX-2 expression was determined by Western and Northern analyses. Prostaglandin E2 (PGE2) in the culture supernatant was measured by ELISA. Cell growth was measured by crystal violet assay. Cellular invasion through Matrigel and anchorage-independent growth in 0.4% agarose were assessed. Tumorigenicity was evaluated by subcutaneous injection of cells in nude mice with and without Matrigel.
Results: Four of 12 clones stably overexpressing COX-2 at high levels relative to vector-transfected control cells were chosen for further study. Cell growth rates of these 4 clones were higher than vector control cells. PGE(2) production was elevated in 3 of these 4 clones, and PGE2 levels correlated significantly with invasion through Matrigel. COX-2-transfected cells did not form colonies in soft agarose or tumors in nude mice.
Conclusions: Forced COX-2 expression in SV-HUC immortalized urothelial cells contributes to increased PGE2 production and increased invasion through Matrigel. However, it is insufficient to induce malignant transformation.