Helicobacter pylori-Induced Invasion and Angiogenesis of Gastric Cells Is Mediated by Cyclooxygenase-2 Induction through TLR2/TLR9 and Promoter Regulation

Abstract

Cyclooxygenase-2 (COX-2) plays a crucial role in Helicobacter pylori-associated gastric cancer. In this study, we report that H. pylori-induced COX-2 expression enhances the cancer cell invasion and angiogenesis via TLR2 and TLR9, which can be attenuated by the specific COX-2 inhibitor NS398 or celecoxib. The cAMP response element (CRE) and AP1 sites, but not κB on the COX-2 promoter, are involved in MAPKs-regulated COX-2 expression. Differential bindings of the CREB-1, ATF-2, c-jun to the CRE site, and the c-fos, c-jun, ATF-2 to the AP1 site are demonstrated by DNA affinity protein-binding, supershift, and chromatin immunoprecipitation assays. Activations of these transcription factors were attenuated by different MAPKs inhibitors. The mutants of TLR2, TLR9, or MAPKs inhibited H. pylori-induced COX-2 promoter, CRE, and AP-1 activities. MAPKs inhibitors attenuated the H. pylori-induced COX-2 mRNA and protein expressions. These results indicate that H. pylori acts through TLR2 and TLR9 to activate MAPKs, especially p38, and their downstream transcription factors (CREB-1, ATF-2, c-jun, and c-fos), resulting in the activations of CRE and AP-1 on the COX-2 promoter. These intracellular networks drive the COX-2-dependent PGE2 release and contribute to cell invasion and angiogenesis.

Toll-like receptors and their role in carcinogenesis and anti-tumor treatment

“…Their role in carcinogenesis depends on the activation of NF-κB and related genes, resulting in the production of cytokines such as IL-1, IL-2, IL-6, IL-10 and TNF-α; the recruitment of cells of the immune system by chemokines; the maintenance of chronic inflammation; and suppression in the tumor microenvironment. This complex net of chemical and direct cell-to-cell interactions may contribute to tumor survival and progression through an antiapoptotic effect, the direct inhibition of cell cytotoxicity or angiogenesis [57,58]. There is still controversy regarding TLRs in angiogenesis, as to whether they promote or inhibit the formation of new vessels.…”

Toll-Like Receptors as Novel Therapeutic Targets for the Treatment of Pancreatic Cancer

“…Differential binding of CREB-1, ATF-2, and c-jun to the CRE site and c-fos, c-jun, and ATF-2 to the AP1 site were demonstrated and attenuated by different MAPK inhibitors as well as mutants of TLR2 and TLR9. In sum, these results showed that H. pylori activated TLR2 and TLR9 to activate MAKs, particularly p38, and downstream transcription factors (CREB-1, ATF-2, c-jun, and c-fos) resulting in activations of CRE and AP-1 on the COX-2 promoter (Chang et al, 2005).…”

“…Thus, H. Pylori activation of TLR2 and TLR9 signals activate the MAPK cascade leading to increased COX-2 and COX-2-dependent prostaglandin E 2 (PGE 2 ) release. This contributes to cancer cell invasion and angiogenesis (Chang et al, 2005). The COX-2 increase can be attenuated by the specific COX-2 inhibitor, NS398 or celecoxib.…”

Genetic Variants of Toll-Like Receptor 2 and 5, Helicobacter Pylori Infection, and Risk of Gastric Cancer and Its Precursors in a Chinese Population

“…H. pylori flagellin is a TLR5 agonist in vitro (11,16), whereas some conflicting reports show that H. pylori flagellin evades TLR5 recognition, which may contribute to its long-term persistence in hosts (19,20). TLR9 could recognize H. pylori CpG DNA, leading to the induction of cytokine secretion (17,18).…”

“…Stimulation of the TLR pathway induces NF-kB activation and transcription of immune response genes such as cytokines and chemokines, leading to the activation of innate immunity and regulation of acquired immunity (9). To date, 10 members of the TLR family have been identified in humans (10), in which TLR2, 4, 5, and 9 are reported to be involved in H. pylori recognition (11)(12)(13)(14)(15)(16)(17)(18). TLR2 was shown to recognize H. pylori lipopolysaccharide (LPS) (11).…”