title: Mechanistic and predictive profiling of 5-Fluorouracil resistance in human cancer cells.
abstract: Gene expression was analyzed in five pairs of 5-fluorouracil (5-FU) resistant and parental cancer cell lines on DNA microarrays. In unsupervised analysis, a prediction rule was built from the expression profiles of 29 genes, and 5-FU sensitivity class was predicted with 100% accuracy and high predictive strength. In supervised analysis of key 5-FU pathways, expression of 91 genes was associated with 5-FU sensitivity phenotype and segregated samples accordingly in hierarchical analysis. Key genes involved in 5-FU activation were significantly down-regulated (thymidine kinase, 2.9-fold; orotate phosphoribosyltransferase, 2.3-fold; uridine monophosphate kinase, 3.2-fold; pyrimidine nucleoside phosphorylase 3.6-fold) in resistant cells. Overexpression of thymidylate synthase and its adjacent gene, c-Yes, was detected in the resistant cell lines. The mRNA and protein overexpression of nuclear factor kappaB (NFkappaB) p65 and related antiapoptotic c-Flip gene was detected in resistant cells. The 5-FU-resistant cell lines also showed high NFkappaB DNA-binding activity. Cotransfection of NFkappaB p50 and p65 cDNA induced 5-FU resistance in MCF-7 cells. Both NFkappaB- and 5-FU-induced resistant cell lines manifested reduced expression of genes governing G(1)-S and S-phase transition. Expression of genes involved in DNA replication was also down-regulated in resistant cell lines. These findings were highly consistent with the slower growth rate, higher proportion of G(1), and lower proportion of S-phase cells in the resistant cell lines. This phenotype may protect resistant cells from cell death induced by incorporation of 5-FU into DNA chains, by allowing time to repair 5-FU-induced damage. Our findings may provide novel targets for tackling 5-FU resistance.
authors.affiliation: Department of Medical Oncology, Beatson Institute for Cancer Research, Glasgow, United Kingdom. w.wang@beatson.gla.ac.uk
authors.forename: Weiguang
authors.initials: W
authors.lastname: Wang
authors.forename: James
authors.initials: J
authors.lastname: Cassidy
authors.forename: Vincent
authors.initials: V
authors.lastname: O'Brien
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Ryan
authors.forename: Elaina
authors.initials: E
authors.lastname: Collie-Duguid
mesh_terms: D001483:Base Sequence; D045744:Cell Line, Tumor; D017931:DNA Primers; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D005434:Flow Cytometry; D005472:Fluorouracil / Q000494:pharmacology*; D016193:G1 Phase; D020869:Gene Expression Profiling; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype
chemical_list: D017931:DNA Primers; D005472:Fluorouracil