Aberrant expression of COX-2 occurs in many types of malignancies including colon and lung cancers, and is implicated in development and progression of cancer. The molecular mechanisms associated with aberrant expression of COX-2 in lung cancer cells remain to be fully elucidated. In this study, we found that non-small cell lung cancer (NSCLC) NCI-H520 and NCI-H460 cells constitutively expressed COX-2 and produced prostaglandin E2 (PGE2) as measured by Western blotting and enzyme-linked immunosorbent assay (ELISA), respectively. Reporter assays showed that transcriptional regulation of COX-2 was blunted when either the NF-IL6 (C/EBPβ) or nuclear factor-κB (NF-κB) binding site in the COX-2 promoter was mutated, suggesting that C/EBPβ and NF-κB transcription factors have an important role in aberrant expression of COX-2 in these lung cancer cells. In addition, the eight herbal mixture PC-SPES (Lot. 5431219) caused growth arrest and apoptosis of NCI-H520 and NCI-H460 cells in association with blockade of NF-κB and down-regulation of C/EBPβ, resulting in down-regulation of COX-2 and PGE2 in these cells. On the other hand, PC-SPES up-regulated the level of C/EBPβ in these cells. Taken together, C/EBPβ and NF-κB may be promising molecular targets for COX-2 inhibition in lung cancer cells. PC-SPES might be useful in the adjuvant setting for the treatment of individuals with resected NSCLC as well as other types of cancer in which COX-2 is activated.

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