The expression level of TRAF1 in human gastric mucosa is related to virulence genotypes of Helicobacter pylori

Inhibitory Effect of β-Carotene on Helicobacter pylori-Induced TRAF Expression and Hyper-Proliferation in Gastric Epithelial Cells

Helicobacter pylori infection causes the hyper-proliferation of gastric epithelial cells that leads to the development of gastric cancer. Overexpression of tumor necrosis factor receptor associated factor (TRAF) is shown in gastric cancer cells. The dietary antioxidant β-carotene has been shown to counter hyper-proliferation in H. pylori-infected gastric epithelial cells. The present study was carried out to examine the β-carotene mechanism of action. We first showed that H. pylori infection decreases cellular IκBα levels while increasing cell viability, NADPH oxidase activity, reactive oxygen species production, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation, and TRAF1 and TRAF2 gene expression, as well as protein–protein interaction in gastric epithelial AGS cells. We then demonstrated that pretreatment of cells with β-carotene significantly attenuates these effects. Our findings support the proposal that β-carotene has anti-cancer activity by reducing NADPH oxidase-mediated production of ROS, NF-κB activation and NF-κB-regulated TRAF1 and TRAF2 gene expression, and hyper-proliferation in AGS cells. We suggest that the consumption of β-carotene-enriched foods could decrease the incidence of H. pylori-associated gastric disorders.

CagA promotes proliferation and inhibits apoptosis of GES-1 cells by upregulating TRAF1/4-1BB

Cytotoxin-associated gene A (CagA) is one of the most important virulence factors of Helicobacter pylori, and serves a role in H. pylori‑mediated tumorigenesis in gastric cancer. However, the underlying molecular mechanism remains to be elucidated. The present study aimed to investigate the effects of CagA on the proliferation and apoptosis of GES‑1 cells, and the underlying mechanism. A CagA eukaryotic expression plasmid was constructed and transfected into GES‑1 cells. The mRNA and protein levels of CagA, tumor necrosis factor receptor‑associated factor 1 (TRAF1) and tumor necrosis factor receptor superfamily member 9 (4‑1BB) were determined using the reverse transcription‑quantitative polymerase chain reaction and western blot analysis, respectively. Western blot and ELISA analysis was used to detect the release of interleukin (IL)‑8. An MTT assay and flow cytometric analysis was used to assess cell viability and apoptosis, respectively. Ectopic expression of CagA markedly increased TRAF1 and 4‑1BB mRNA and protein levels in GES‑1 cells. CagA increased the expression and release of IL‑8 in GES‑1 cells. The expression of CagA significantly promoted the proliferation (P<0.05) and inhibited the apoptosis (P<0.05) of GES‑1 cells. In conclusion, CagA upregulated TRAF1/4‑1BB, thereby promoting the proliferation and inhibiting the apoptosis of GES-1 cells.

TRAF1 Is Critical for DMBA/Solar UVR-Induced Skin Carcinogenesis

TRAF1 is a member of the TRAF protein family, which regulates the canonical and noncanonical NF-κB signaling cascades. Although aberrant TRAF1 expression in tumors has been reported, the role of TRAF1 remains elusive. Here, we report that TRAF1 is required for solar UV-induced skin carcinogenesis. Immunohistochemical analysis showed that TRAF1 expression is up-regulated in human actinic keratosis and squamous cell carcinoma. In vivo studies indicated that TRAF1 expression levels in mouse skin are induced by short-term solar UV irradiation, and a long-term skin carcinogenesis study showed that deletion of TRAF1 in mice results in a significant inhibition of skin tumor formation. Moreover, we show that TRAF1 is required for solar UV-induced extracellular signal-regulated kinase-5 (ERK5) phosphorylation and the expression of AP-1 family members (c-Fos/c-Jun). Mechanistic studies showed that TRAF1 expression enhances the ubiquitination of ERK5 on lysine 184, which is necessary for its kinase activity and AP-1 activation. Overall, our results suggest that TRAF1 mediates ERK5 activity by regulating the upstream effectors of ERK5 and also by modulating its ubiquitination status. Targeting TRAF1 function might lead to strategies for preventing and treating skin cancer.

Association between Virulence Factors and TRAF1/4-1BB/Bcl-xL Expression in Gastric Mucosa Infected with Helicobacter pylori

Objective. CagA+/vacAs1+/vacAm1+ Helicobacter pylori upregulates the expression of tumor necrosis factor receptor-associated factor 1 (TRAF1), tumor necrosis factor receptor superfamily member 9 (4-1BB), and B-cell lymphoma-extra large (Bcl-xL) in human gastric epithelial cells. We investigated the correlation between cagA/vacAs1/vacAm1 and TRAF1/4-1BB/Bcl-xL expression in gastric mucosal tissue of patients with gastric disorders. Methods. We collected gastric mucosa samples from 35 chronic, nonatrophic gastritis (CG) patients, 41 atrophic gastritis patients, 44 intestinal metaplasia with atypical hyperplasia (IM) patients, and 28 gastric carcinoma (Ca) patients. The expression of  TRAF1, 4-1BB, and Bcl-xL was determined using western blotting. The expression of cagA, vacAs1, and vacAm1 in H. pylori was examined with polymerase chain reaction. Results. The expression of TRAF1, 4-1BB, and Bcl-xL was significantly upregulated in IM and Ca patients (P < 0.05 compared with CG). There were more cases of cagA+/vacAs1+/vacAm1+ H. pylori infection in samples with elevated TRAF1, 4-1BB, or Bcl-xL expression (P < 0.05). Additionally, there were a remarkably large number of samples with upregulated TRAF1/4-1BB/Bcl-xL expression in cases of cagA+/vacAs1+/vacAm1+ H. pylori infection (44 cases, 67.7%; P < 0.05). Conclusions. The pathogenesis of IM and Ca may be promoted by cagA+/vacAs1+/vacAm1+ H. pylori, possibly via upregulated TRAF1, 4-1BB, and Bcl-xL in gastric mucosal tissue.