title: Pathway and single gene analyses of inhibited Caco-2 differentiation by ascorbate-stabilized quercetin suggest enhancement of cellular processes associated with development of colon cancer.
abstract: The aim was to investigate mechanisms contributing to quercetin's previously described effects on cell-proliferation and -differentiation, which contradicted its proposed anticarcinogenic potency. In a 10-day experiment, 40 microM quercetin stabilized by 1 mM ascorbate reduced Caco-2 differentiation up to 50% (p < 0.001). Caco-2 RNA from days 5 and 10, hybridized on HG-U133A2.0 Affymetrix GeneChips(R), showed 1,743 affected genes on both days (p < 0.01). All 14 Caco-2 differentiation-associated genes showed decreased expression (p < 0.01), including intestinal alkaline phosphatase, that was confirmed technically (qRT-PCR) and functionally (enzyme-activity). The 1,743 genes contributed to 27 pathways (p < 0.05) categorized under six gene ontology (GO) processes, including apoptosis and cell-cycle. Genes within these GO-processes showed fold changes that suggest increased cell-survival and -proliferation. Furthermore, quercetin down-regulated expression of genes involved in tumor-suppression and phase II metabolism, and up-regulated oncogenes. Gene expression changes mediated by ascorbate-stabilized quercetin were concordant with those occurring in human colorectal carcinogenesis ( approximately 80-90%), but were opposite to those previously described for Caco-2 cells exposed to quercetin without ascorbate ( approximately 75-90%). In conclusion, gene expression among Caco-2 cells exposed to ascorbate-stabilized quercetin showed mechanisms contrary to what is expected for a cancer-preventive agent. Whether this unexpected in vitro effect is relevant in vivo, remains to be elucidated.
authors.affiliation: TNO Quality of Life, Business Unit Biosciences, Zeist, The Netherlands.
authors.forename: Ashwin A
authors.initials: AA
authors.lastname: Dihal
authors.forename: Chantal
authors.initials: C
authors.lastname: Tilburgs
authors.forename: Marjan J
authors.initials: MJ
authors.lastname: van Erk
authors.forename: Ivonne M C M
authors.initials: IM
authors.lastname: Rietjens
authors.forename: Ruud A
authors.initials: RA
authors.lastname: Woutersen
authors.forename: Rob H
authors.initials: RH
authors.lastname: Stierum
mesh_terms: D001205:Ascorbic Acid / Q000494:pharmacology*; D018938:Caco-2 Cells; D002454:Cell Differentiation / Q000187:drug effects* / Q000235:genetics; D002455:Cell Division / Q000187:drug effects; D003110:Colonic Neoplasms / Q000235:genetics* / Q000473:pathology; D004355:Drug Stability; D015870:Gene Expression; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis; D011794:Quercetin / Q000494:pharmacology*
chemical_list: D011794:Quercetin; D001205:Ascorbic Acid