A key target for NSAID-induced map (ERK-2) kinase – Inhibition of gastric cancer cell proliferation and growth

Clinical and limited experimental studies indicate that NSAIDs may inhibit gastric cancer growth. However, the mechanisms involved are not completely understood.

Map(ERK-2)kinase signaling pathway is essential for cell proliferation, but the effect of NSAIDs on ERK-2 activity and phosphorylation in gastric cancer has never been studied. We studied whether NS-398 and/or indomethacin (IND): 1) inhibit gastric cancer cell proliferation, 2) whether this inhibition is mediated via ERK-2, and whether 3) NSAIDs enhance apoptosis in gastric cancer cells. Human gastric epithelial cells (MKN28) were treated with either vehicle, 0.25–0.5 mM IND or 50–100 uM NS-398 for 6–48 hrs. Cell proliferation determined by 3H-thymidine uptake, MAPK activity by incorporation of radiolabeled phosphate into myelin basic protein, apoptosis was evaluated using TUNEL assay.

Results: 1) IND and NS-398 significantly (by 3.5–5 fold) inhibited the proliferation of MKN28 cells at 24 hrs. Both NSAIDs also significantly inhibited ERK-2 activity: IND >53±9% inhibition, NS-398, 72±6% inhibition (both p<0.05); 3) IND significantly increased the apoptotic index by 30% vs. vehicle; p<0.05. The correlation between inhibition of cell proliferation and ERK-2 activity reduction by NSAIDs was r=0.921 for IND and r=0.983 for NS-398.

Conclusions: IND and NS-398 significantly inhibit proliferation and growth of human gastric cancer cell line MKN28. This effect of NSAIDs is mediated by inhibition of MAP (ERK-2) kinase signaling pathway, essential for cell proliferation. Thus, in addition to inhibiting cyclooxygenase, NSAIDs inhibit phosphorylating enzymes – kinases essential for signal transduction. NSAIDs also increase apoptosis in gastric cancer cells.