Shu-Liang Zhao

BACKGROUND: The molecular mechanisms that control the aggressiveness of gastric cancer (GC) remain poorly defined. Here we show that synbindin contributes to the aggressiveness of GC by activating extracellular signal-regulated protein kinase (ERK) signaling on the Golgi apparatus. METHODS: Expression of synbindin was examined in normal gastric mucosa (n = 44), intestinal metaplastic gastric mucosa (n = 66), and GC tissues (n=52), and the biological effects of synbindin on tumor growth and ERK signaling were detected in cultured cells, nude mice, and human tissue samples. The interaction between synbindin and mitogen-activated protein kinase kinase (MEK1)/ERK was determined by immunofluorescence and fluorescence resonance energy transfer assays. The transactivation of synbindin by nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) was detected using luciferase reporter assay and chromatin immunoprecipitation. RESULTS: High expression of synbindin was associated with larger tumor size (120.8 vs 44.8 cm(3); P = .01), advanced tumor node metastasis (TNM) stage (P = .003), and shorter patient survival (hazard ratio = 1.51; 95% confidence interval [CI] = 1.01 to 2.27; P = .046). Synbindin promotes cell proliferation and invasion by activating ERK2 on the Golgi apparatus, and synbindin is directly transactivated by NF-κB. Synbindin expression level was statistically significantly higher in human GCs with activated ERK2 than those with low ERK2 activity (intensity score of 11.5, 95% CI = 10.4 to 12.4 vs intensity score of 4.6, 95% CI 3.9 to 5.3; P < .001). Targeting synbindin in xenograft tumors decreased ERK2 phosphorylation and statistically significantly reduced tumor volume (451.2mm(3), 95% CI = 328.3 to 574.1 vs 726.1mm(3), 95% CI = 544.2 to 908.2; P = .01). CONCLUSIONS: Synbindin contributes to malignant phenotypes of GC by activating ERK on the Golgi, and synbindin is a potential biomarker and therapeutic target for GC.

The trafficking protein particle complex 4 (TRAPPC4) is implicated in vesicle-mediated transport, but its association with disease has rarely been reported. We explored its potential interaction with ERK2, part of the ERK1/2 complex in the Extracellular Signal-regulated Kinase/ Mitogen-activated Protein Kinase (ERK-MAPK) pathway, by a yeast two-hybrid screen and confirmed by co-immunoprecipitation (Co-IP) and glutathione S-transferase (GST) pull-down. Further investigation found that when TRAPPC4 was depleted, activated ERK1/2 specifically decreased in the nucleus, which was accompanied with cell growth suppression and apoptosis in colorectal cancer (CRC) cells. Overexpression of TRAPPC4 promoted cell viability and caused activated ERK1/2 to increase overall, but especially in the nucleus. TRAPPC4 was expressed more highly in the nucleus of CRC cells than in normal colonic epithelium or adenoma which corresponded with nuclear staining of pERK1/2. We demonstrate here that TRAPPC4 may regulate cell proliferation and apoptosis in CRC by interaction with ERK2 and subsequently phosphorylating ERK1/2 as well as modulating the subcellular location of pERK1/2 to activate the relevant signaling pathway.

Colorectal cancer is a leading cause of morbidity and mortality worldwide, and its incidence has been increasing in recent years. The role of epigenetic modifications, including DNA methylation and histone modifications, has only recently been investigated. In this study, the effects of epigenetic agents such as folic acid (FA) and sodium butyrate (NaBu) on the development of colorectal cancer induced by 1,2-dimethylhydrazine (DMH) using ICR mice was examined. Of the mice treated in a chemopreventive manner with epigenetic agents, FA and NaBu, 15-50% developed colorectal cancer at 24 weeks compared with a 95% incidence of colorectal cancer in DMH-treated control mice. Folate deficiency can alter cytosine methylation in DNA leading to inappropriate activation of the proto-oncogene c-myc. We detected lower levels of p21(WAF1) gene expression in colorectal cancer samples, as well as significantly lower levels of acetylated histone H3, compared with samples from corresponding normal colorectal mucosa. In contrast, administration of NaBu increased levels of p21(WAF1) mRNA and p21(WAF1) protein, and was associated with an accumulation of histone acetylation. In summary, our results show that FA and NaBu reduce the incidence of colorectal cancer induced by DMH-induced in ICR mice, and therefore we hypothesize that targeting epigenetic targets should be further investigated for the prevention of colorectal cancer in humans.