however, the underlying molecular mechanisms by which IL B mediated p38 signaling is regulated during gastric carcinogenesis remain largely unknown. One potential mechanism by which p38 could increase the invasion and migration of cancer cells is by elevating the levels of MMPs. It is well established that secretion of MMPs with the capacity for e tracellular matri degradation is a feature of metastatic cancer cells. MMP2 and MMP9 are two of the most well characterized MMPs and are closely associated with cancer invasion and metastasis due to their strong proteolytic activity of ECM. We report here also for the first time that the likely molecular mechanism by which IL 1B promotes GA cell migration and invasion may involve the IL 1B p38 AP 1 MMP2 MMP9 signaling pathway.

We demonstrated that both MMP2 and MMP9 were upregulated in GA cells in response to IL 1B stimulation. these effects were inhibited by siRNAs against p38, MMP2 or MMP9, the p38 inhibitor SB202190, and the MMP2 9 inhibitor BiPs. Furthermore, knockdown of MMP2 or MMP9 using siRNAs, or inhibition of MMP2 9 activity using BiPs, significantly decreased IL 1B induced GA cell migration and invasion. As a serine threonine protein kinase, p38 is capable of inducing activation of the transcription factor AP 1. We further found that the IL 1B induced, p38 mediated upregulation of MMP2 and MMP9 were AP 1 dependent. IL 1B was only able to activate the transcription of MMP9 promoter regions containing AP 1 sites, and these effects were attenuated by p38 siRNA and the p38 inhibitor SB202190.

Add itionally, IL 1B induced activation of AP 1 dependent transcription was inhibited by p38 siRNA. Phospho p38, the activated form Batimastat of p38, could be detected in nearly 50% of the human GA tissue samples tested by IHC assay, and e pression of p p38 was sig nificantly associated with lymph node metastasis, and invasion beyond the serosa in patients with GA. Moreover, the e pression of IL 1B positively correlated with the e pression of p p38, MMP2, MMP9 and c fos in the clin ical GA specimens. Furthermore, in vivo data from the me tastasis assay demonstrated that the formation of lung metastatic foci by GA cells, and p38 p p38, MMP2, MMP9 and c fos mRNA and protein e pression in the lung metastatic foci were elevated by IL 1B, and re duced by injection of cells transfected with p38 siRNA.

Taken together, these data strongly suggest that IL 1B induced GA cell migration and invasion occur via activa tion of the p38 signaling pathway which leads to AP 1 activation and upregulation of MMP2 and MMP9. There fore, p38 plays an essential role in IL 1B induced metasta sis in GA. JNK is another important MAPK to be well known to play important roles in regulation IL 1B signaling in several different cells. However, in this study, JNK was found to be not involved in regulation of IL 1B induced GA cell migration and invasion.