MiR-92 is significantly elevated in plasma of patients with CRC and can be a potential non-invasive molecular marker for CRC screening.

In cancer cells, glucose is often converted into lactic acid, which is known as the 'Warburg effect'. The reason that cancer cells have a higher rate of aerobic glycolysis, but not oxidative phosphorylation, remains largely unclear. Herein, we proposed an epigenetic mechanism of the Warburg effect. Fructose-1,6-bisphosphatase-1 (FBP1), which functions to antagonize glycolysis was downregulated through NF-kappaB pathway in Ras-transformed NIH3T3 cells. Restoration of FBP1 expression suppressed anchorage-independent growth, indicating the relevance of FBP1 downregulation in carcinogenesis. Indeed, FBP1 was downregulated in gastric carcinomas (Po0.01, n ¼ 22) and gastric cancer cell lines (57%, 4/7). Restoration of FBP1 expression reduced growth and glycolysis in gastric cancer cells. Moreover, FBP1 downregulation was reversed by pharmacological demethylation. Its promoter was hypermethylated in gastric cancer cell lines (57%, 4/7) and gastric carcinomas (33%, 33/ 101). Inhibition of NF-kappaB restored FBP1 expression, partially through demethylation of FBP1 promoter. Notably, Cox regression analysis revealed FBP1 promoter methylation as an independent prognosis predicator for gastric cancer (hazard ratio: 3.60, P ¼ 0.010). In summary, we found that NF-kappaB functions downstream of Ras to promote epigenetic downregulation of FBP1. Promoter methylation of FBP1 can be used as a new biomarker for prognosis prediction of gastric cancer. Such an important epigenetic link between glycolysis and carcinogenesis partly explains the Warburg effect.

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Cigarette smoking is a putative environmental risk factor for colon cancer. Nicotine, an active alkaloid in tobacco, has been implicated in carcinogenesis. In the present study, we demonstrated that oral nicotine administration (50 or 200 microg/ml) for 25 days stimulated growth of human colon cancer xenograft in nude mice. It also increased vascularization in the tumors and elevated cotinine and adrenaline plasma levels. beta-Adrenoceptors, cyclooxygenase-2 (COX-2), prostaglandin E(2) (PGE(2)), and vascular endothelial growth factor (VEGF) in tumor tissues were also increased by nicotine. I.p. injection of beta(1)-selective antagonist (atenolol, 5 or 10 mg/kg) or beta(2)-selective antagonist (ICI 118,551, 5, or 10 mg/kg) blocked the nicotine-stimulated tumor growth dose dependently, in which beta(2)-selective antagonist produced a more prominent effect. beta-Adrenoceptors blockade also abrogated the stimulatory action of nicotine on microvessel densities as well as cell expression of COX-2, PGE(2), and VEGF, in which beta(2)-selective antagonist produced a significant effect. These findings provide a direct evidence that nicotine can enhance colon tumor growth mediated partly by stimulation of beta-adrenoceptors, preferentially the beta(2)-adrenoceptors. Activation of beta-adrenoceptors and the subsequent stimulation of COX-2, PGE(2), and VEGF expression is perhaps an important mechanism in the tumorigenic action of nicotine on colon tumor growth. These data suggest that beta-adrenoceptors play a modulatory role in the development of colon cancer and partly elucidate the carcinogenic action of cigarette smoke.

Cigarette smoking is a risk factor for colorectal cancer. It is suggested that 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a tobacco-specific nitrosamine, mediates the carcinogenic action of cigarette smoking by promoting cancer growth. In the present study, the proliferative response of a cultured colon cancer cell line HT-29 to NNK was determined. It was found that NNK dose-dependently stimulated HT-29 cell proliferation. In this regard, the stimulatory action of NNK was abolished by atenolol and ICI 118,551, a B 1 -and B 2 -selective antagonist, respectively. In addition, cell growth was stimulated by the nonselective adrenergic agonist, noradrenaline, and more effectively by the B-selective agonist, isoproterenol. The second message cyclic AMP level for B-adrenoceptor activation was elevated by isoproterenol and NNK treatment. These agents also up-regulated cyclooxygenase-2 expression, cytosolic phospholipase A 2 expression, and prostaglandin E 2 release. B 2 -adrenoceptor blockade with ICI 118,551, in contrast, significantly decreased cyclooxygenase-2 expression, cytosolic phospholipase A 2 expression and prostaglandin E 2 release induced by NNK and isoproterenol. To conclude, it is proposed that NNK stimulates HT-29 cell proliferation through B-adrenoceptors, preferentially B 2 receptors. Activation of the B-adrenoceptors, and the consequent cyclic AMP elevation coupled with the downstream arachidonic acid pathway, is perhaps an important mechanistic cascade in the promotion of colon cancer growth. These findings partly elucidate the carcinogenic actions of cigarette smoke and shed new light on the novel modulatory role of B-adrenoceptors in the development of colon cancer. (Cancer Res 2005; 65(12): 5272-7)

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Blockade of angiogenesis is a promising strategy to suppress tumor growth, invasion, and metastasis. Vascular endothelial growth factor (VEGF), which binds to tyrosine kinase receptors [VEGF receptors (VEGFR) 1 and 2], is the mediator of angiogenesis and mitogen for endothelial cells. Cyclooxygenase-2 (COX-2) plays an important role in the promoting action of nicotine on gastric cancer growth. However, the action of nicotine and the relationship between COX-2 and VEGF/VEGFR system in tumorigenesis remain undefined. In this study, the effects of nicotine in tumor angiogenesis, invasiveness, and metastasis were studied with sponge implantation and Matrigel membrane models. Nicotine (200 Mg/mL) stimulated gastric cancer cell proliferation, which was blocked by SC-236 (a highly selective COX-2 inhibitor) and CBO-P11 (a VEGFR inhibitor). This was associated with decreased VEGF levels as well as VEGFR-2 but not VEGFR-1 expression. Topical injection of nicotine enhanced tumor-associated vascularization, with a concomitant increase in VEGF levels in sponge implants. Again, application of SC-236 (2 mg/kg) and CBO-P11 (0.4 mg/kg) partially attenuated vascularization by f30%. Furthermore, nicotine enhanced tumor cell invasion through the Matrigel membrane by 4-fold and promoted migration of human umbilical vein endothelial cells in a cocultured system with gastric cancer cells. The activity of matrix metalloproteinases 2 and 9 and protein expressions of plasminogen activators (urokinase-type plasminogen activator and its receptor), which are the indicators of invasion and migration processes, were increased by nicotine but blocked by COX-2 and VEGFR inhibitors. Taken together, our results reveal that the promoting action of nicotine on angiogenesis, tumor invasion, and metastasis is COX-2/VEGF/VEGFR dependent. (Mol Cancer Res 2005;3(11):607 -15)