title: Caffeine inhibits adenosine-induced accumulation of hypoxia-inducible factor-1alpha, vascular endothelial growth factor, and interleukin-8 expression in hypoxic human colon cancer cells.
abstract: Frequent coffee consumption has been associated with a reduced risk of colorectal cancer in a number of case-control studies. Coffee is a leading source of methylxanthines, such as caffeine. The induction of vascular endothelial growth factor (VEGF) and interleukin-8 (IL-8) is an essential feature of tumor angiogenesis, and the hypoxia-inducible factor-1 (HIF-1) transcription factor is known to be a key regulator of this process. In this study, we investigated the effects of caffeine on HIF-1 protein accumulation and on VEGF and IL-8 expression in the human colon cancer cell line HT29 under hypoxic conditions. Our results show that caffeine significantly inhibits adenosine-induced HIF-1alpha protein accumulation in cancer cells. We show that HIF-1alpha and VEGF are increased through A3 adenosine receptor stimulation, whereas the effects on IL-8 are mediated via the A2B subtype. Pretreatment of cells with caffeine significantly reduces adenosine-induced VEGF promoter activity and VEGF and IL-8 expression. The mechanism of caffeine seems to involve the inhibition of the extracellular signal-regulated kinase 1/2 (ERK1/2), p38, and Akt, leading to a marked decrease in adenosine-induced HIF-1alpha accumulation, VEGF transcriptional activation, and VEGF and IL-8 protein accumulation. From a functional perspective, we observe that caffeine also significantly inhibits the A3 receptor-stimulated cell migration of colon cancer cells. Conditioned media prepared from colon cells treated with an adenosine analog increased human umbilical vein endothelial cell migration. These data provide evidence that adenosine could modulate the migration of colon cancer cells by an HIF-1alpha/VEGF/IL-8-dependent mechanism and that caffeine has the potential to inhibit colon cancer cell growth.
authors.affiliation: Department of Clinical and Experimental Medicine, Pharmacology Unit, University of Ferrara, Ferrara, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Merighi
authors.forename: Annalisa
authors.initials: A
authors.lastname: Benini
authors.forename: Prisco
authors.initials: P
authors.lastname: Mirandola
authors.forename: Stefania
authors.initials: S
authors.lastname: Gessi
authors.forename: Katia
authors.initials: K
authors.lastname: Varani
authors.forename: Carolina
authors.initials: C
authors.lastname: Simioni
authors.forename: Edward
authors.initials: E
authors.lastname: Leung
authors.forename: Stephen
authors.initials: S
authors.lastname: Maclennan
authors.forename: Pier Giovanni
authors.initials: PG
authors.lastname: Baraldi
authors.forename: Pier Andrea
authors.initials: PA
authors.lastname: Borea
mesh_terms: D000241:Adenosine / Q000494:pharmacology*; D002110:Caffeine / Q000494:pharmacology*; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D003110:Colonic Neoplasms / Q000378:metabolism* / Q000473:pathology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D016209:Interleukin-8 / Q000378:metabolism*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D043704:Receptor, Adenosine A2B / Q000235:genetics; D043684:Receptor, Adenosine A3 / Q000235:genetics / Q000502:physiology; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D016209:Interleukin-8; D043704:Receptor, Adenosine A2B; D043684:Receptor, Adenosine A3; D042461:Vascular Endothelial Growth Factor A; D002110:Caffeine; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D000241:Adenosine