Effects of COX-2 inhibition on expression of vascular endothelial growth factor and interleukin-8 in lung cancer cells.
BACKGROUND
Cyclooxygenase (COX)-2 has been implicated in tumour progression, angiogenesis and metastasis in non-small cell lung cancer (NSCLC). We speculated that inhibition of COX-2 activity might reduce expression of the pro-angiogenic factors vascular endothelial growth factor (VEGF) and interleukin-8 (IL-8) in lung cancer cells.


METHODS
The levels of IL-8, VEGF and prostaglandin E2 (PGE2) were measured by ELISA. Expression of COX-1 and COX-2 was determined by Western blotting. Inhibition or knockdown of COX-2 was achieved by treating NSCLC cells with specific COX-2 inhibitor NS-398 or COX-2 siRNA, respectively.


RESULTS
We found that NSCLC cell lines produced more IL-8 than VEGF (p < 0.001). In contrast, small cell lung cancer (SCLC) cell lines produced more VEGF than IL-8 (p < 0.001). COX-1 was expressed in all cell lines, but COX-2 was expressed only in NSCLC cell lines. Consistent with this, PGE2 was significantly higher in NSCLC cell lines than SCLC cell lines (p < 0.001). We tested these cell lines with a potent specific COX-2 inhibitor NS-398 at concentrations of 0.02, 0.2, 2, 20 microM for 24 or 48 h. The COX-2 activity was reduced in a dose-dependent fashion as shown by reduced PGE2 production. VEGF was significantly reduced following the treatment of NS-398 in A549 (by 31%) and MOR/P (by 47%) cells lines which expressing strong COX-2, but not in H460 cell line which expressing very low COX-2. However, IL-8 was not reduced in these cell lines. To confirm these results, we knocked down COX-2 expression with COX-2 siRNA in these cell lines. VEGF was significantly decreased in A549 (by 24%) and in MOR/P (by 53%), but not in H460 whereas IL-8 was not affected in any cell line.


CONCLUSIONS
We conclude that NSCLC cells produce much higher levels of IL-8 than SCLC cells whereas both NSCLC and SCLC cells produce similar levels of VEGF. COX-2 is only expressed in NSCLC cells, but not in SCLC cells. VEGF is produced in both NSCLC and SCLC cells regardless of COX-2 expression. However, VEGF production is, at least partly, COX-2 dependent in NSCLC cells expressing COX-2. In contrast, IL-8 production is COX-2 independent in both NSCLC and SCLC cells. We speculate that combined targeting of COX-2 and IL-8 may be useful in the treatment of patients with NSCLC and targeting VEGF may be useful in the treatment of patients with SCLC.
Zhu
Yong Ming
YM
Institute for Cancer Studies, School of Medicine and Biomedical Science, University of Sheffield, Beech Hill Road, Sheffield S10 2RX, UK. y.m.zhu@sheffield.ac.uk
Azahri
Nor Saadah M
NS
Yu
Danny C W
DC
Woll
Penella J
PJ
D002289:Carcinoma, Non-Small-Cell Lung / Q000378:metabolism*; D018288:Carcinoma, Small Cell / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D051546:Cyclooxygenase 2 / Q000502:physiology*; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology*; D015232:Dinoprostone / Q000378:metabolism; D018450:Disease Progression; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism*; D008175:Lung Neoplasms / Q000378:metabolism*; D009362:Neoplasm Metastasis; D009389:Neovascularization, Pathologic; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*
D016861:Cyclooxygenase Inhibitors; D016209:Interleukin-8; D042461:Vascular Endothelial Growth Factor A; D051546:Cyclooxygenase 2; D015232:Dinoprostone