Lovastatin induces COX-2 and PGE2 in immortalized human bronchial epithelial cells.

B81

Purpose Statins are attractive candidates in the treatment and prevention of lung tumors, since lung cancer and atherosclerosis share several important risk factors including smoking and advanced age. Cyclooxygenase 2 (COX-2) inhibition, while effective in the prevention of colon cancer recurrence, has been associated with an increased incidence of myocardial infarction. Thus, there is a rationale for combined prevention of lung cancer with statins and COX-2 inhibitors. Methods We utilized Human Immortalized Bronchial Epithelial Cells (HBEC) and HBEC with K-rasV12 mutations (HBEC-Kras). We treated cells with lovastatin at concentrations of 1-5μM, and celecoxib at doses of 1-2.5μM. Mevalonolactone 250uM treatment was utilized for specific reversal of HMG-CoA reductase inhibition. 24-72 hours following treatment, we assayed proliferation by MTT assays, PGE₂ levels by competitive ELISA and COX-2 mRNA and protein levels by Western Blot and RT-PCR. Results HBEC-Kras cells demonstrated markedly elevated PGE₂, COX-2 mRNA and COX-2 protein levels compared to HBEC cells. Lovastatin markedly reduced the proliferation of both HBEC and HBEC-Kras cells. We hypothesized that lovastatin treatment would reduce the PGE₂ and COX-2 levels in these cell lines. Surprisingly, 48 hours of lovastatin treatment markedly increased PGE₂ levels in both cell lines. Statins induced higher PGE₂ levels in HBEC-Kras cells compared to HBEC cells. This induction was lovastatin concentration dependent, and reversible with mevalonate. We found that the lovastatin mediated elevation of PGE₂ levels was first detectable at 48hrs and increased at 72hrs, suggesting a specific, sterol-mediated mechanism. Lovastatin increased COX-2 mRNA and protein levels in a dose and time dependent manner. The COX-2 mRNA and protein levels were higher at every dose and time in HBEC-Kras cells compared to HBEC. Finally, we investigated the impact of lovastatin and celecoxib in combination on cell proliferation. We found that celecoxib alone had no anti-proliferative effect, whereas combination treatment reduced cell proliferation greater than lovastatin alone. Conclusion Lovastatin induces the production of PGE₂, COX-2 mRNA and COX-2 protein in a concentration, sterol and time dependent manner, in HBEC and HBEC-Kras cells. Celecoxib and lovastatin in combination have an augmented anti-proliferative effect than either drug alone. While the importance and mechanism of lovastatin mediated COX-2 induction is under investigation, the combination of these agents warrants further study.