COX-2 expression and cell cycle progression in human fibroblasts

Cyclooxygenase-2 (COX-2) is continuously expressed in mostcancerous cells where it appears to modulate cellular proliferation andapoptosis. However, little is known about the contribution oftransient COX-2 induction to cell cycle progression or programmed celldeath in primary cells. In this study we determined whether COX-2regulates proliferation or apoptosis in human fibroblasts. COX-2 mRNA, protein, and prostaglandin E₂(PGE₂) were not detected in quiescent cells but wereexpressed during the G₀/G₁ phase of the cellcycle induced by serum. Inhibition of COX-2 did not alter G₀/G₁ to S phase transition or induceapoptosis at concentrations that diminished PGE₂.Addition of interleukin-1 to serum enhanced COX-2 expression andPGE₂ synthesis over that by serum alone but had no effecton the progression of these cells into S phase. Furthermore,platelet-derived growth factor drove the G₀ fibroblasts into the cell cycle without inducing detectable levels of COX-2 orPGE₂. Collectively, these data show that transient COX-2expression in primary human fibroblasts does not influence cell cycle progression.