Received for publication July 5, 2005.
Revised September 7, 2005.
Accepted for publication September 14, 2005.

NO-donating aspirin inhibits colon cancer cell growth via MAP kinase activation

Abstract

Nitric oxide donating aspirin (NO-aspirin), representing a new concept in the development of more efficacious NSAIDs, consists of traditional aspirin bearing -ONO₂, which releases NO. Traditional aspirin prevents human colon cancer but its toxicity precludes its application as a chemopreventive agent. NO-aspirin appears safer and in cultured cancer cells it is >1,000 fold more potent than aspirin. To determine the mechanism by which NO-aspirin inhibits cell growth, we studied its effect on MAPK signaling in HT-29 human colon cancer cells. NO-aspirin stimulated the phosphorylation of ERK1/2 and Akt only marginally. The greatest increases in phosphorylation were seen in JNK and p38 MAP kinases, which were observed as early as 5 minutes and after 1 hr of treatment, averaged more than 10 fold over control. The activation of JNK and p38 was accompanied by large increases in the phosphorylation of the downstream transcription factors cJun and ATF-2. We used specific MAPK inhibitors, siRNA gene silencing methods and dominant negative cJUN to determine the relevance of these phosphorylation events to the ability of NO-aspirin to inhibit colon cancer cell growth. Only the dual inhibitor of p38 and JNK and the use of combined siRNA silencing of p38 and cJun abrogated the ability of NO-aspirin to block cell growth. Our data indicate that NO-aspirin is dependent on both the p38 and the JNK MAP kinase pathways for its ability to inhibit the growth of colon cancer cells.

Key words: JNK, MAPK signaling, NO-donating aspirin, NSAIDs, chemoprevention, colon cancer