Characterization of the effects of cyclooxygenase-2 inhibition in the regulation of apoptosis in human small and non-small cell lung cancer cell lines.
BACKGROUND
Cyclooxygenase-2 enzyme (COX-2) is overexpressed in human non-small cell lung cancer (NSCLC) but is not expressed in small cell lung cancer. Selective COX-2 inhibitors have been shown to induce apoptosis in NSCLC cells, an effect which is associated with the regulation of intracellular MAP kinase (MAPK) signal pathways. Our aims were to characterize the effects of COX-2 inhibition by rofecoxib on apoptosis in human NSCLC and small cell lung cancer cell lines.


METHODS
The human NSCLC cell line NCI-H2126 and small cell lung cancer cell line DMS-79 were used. Constitutive COX-2 protein levels were first determined by Western blot test. Levels of apoptosis were evaluated by using propidium iodide staining on FACScan analysis after incubation of NCI-H2126 and DMS-79 with p38 MAPK inhibitor SB202190 (25 ?microM), NF-kappaB inhibitor SN50 (75 microg/mL), and rofecoxib at 100 and 250 microM. All statistical analysis was performed by analysis of variance.


RESULTS
Western blot test confirmed the presence of COX-2 enzyme in NCI-H2126 and absence in DMS-79. Interestingly, rofecoxib treatment demonstrated a dose-dependent increase in apoptosis in both cell lines. Given this finding, the effect of rofecoxib on NF-kappaB and p38 MAPK pathways was also examined. Apoptosis in both cell lines was unaltered by SN50, either alone or in combination with rofecoxib. A similar phenomenon was observed in NCI-H2126 cells treated with SB202190, either alone or in combination with rofecoxib. In contrast, p38 MAPK inhibition greatly upregulated DMS-79 apoptosis in a manner that was unaltered by the addition of rofecoxib.


CONCLUSIONS
Rofecoxib led to a dose-dependent increase in apoptosis in both tumor cell lines. This effect occurred independently of COX-2, NF-kappaB, and p38 MAPK pathways in DMS-79 cells. As such, rofecoxib must act on alternative pathways to regulate apoptosis in human small cell lung cancer cells.
Alam
Mahmood
M
Department of Cardiothoracic Surgery, Cork University Hospital, Cork, Republic of Ireland.
Wang
Jiang Huai
JH
Coffey
John Calvin
JC
Qadri
Syed Suhail
SS
O'Donnell
Aonghus
A
Aherne
Thomas
T
Redmond
Henry Paul
HP
D000704:Analysis of Variance; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002289:Carcinoma, Non-Small-Cell Lung / Q000201:enzymology*; D018288:Carcinoma, Small Cell / Q000201:enzymology*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007783:Lactones / Q000494:pharmacology*; D008175:Lung Neoplasms / Q000201:enzymology*; D016328:NF-kappa B / Q000037:antagonists & inhibitors; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction; D013450:Sulfones / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D015854:Up-Regulation; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors
D004791:Enzyme Inhibitors; D007093:Imidazoles; D007783:Lactones; D016328:NF-kappa B; D011725:Pyridines; D013450:Sulfones; C116926:rofecoxib; D048051:p38 Mitogen-Activated Protein Kinases; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole