title: Silencing the wild-type and mutant K-ras increases the resistance to 5-flurouracil in HCT-116 as a colorectal cancer cell line.
abstract: Colon cancer is the second to third common cancer worldwide. Several efforts have been made to reveal the pathways responsible for drug resistance in this type of cancer. We aimed to investigate the effect of silencing both mutant and wild-type Kristen Rous sarcoma (k-ras) on the response of human colorectal tumor 116 (HCT-116) as a colon cancer cell line to the cytotoxic effect of 5-flurouracil (5-FU). One oligonucelotide against mutant k-ras (12th codon, namely 207) and two against wild-type k-ras (namely 535 and 689) were cloned into pSilencer neo2.1. The linearized vectors besides the negative control plasmid were stably transfected into HCT-116. The proliferation rates of these cells in different concentrations of 5-FU and the apoptosis rates of the cells after treatment with lethal doses of 5-FU were studied. Moreover, the cell cycle in these cells was also analyzed by staining the cells with propidium iodide. Stably transfected cells were named HCT207ks, HCT535ks, HCT689ks, and HCT-Sc (transfected with the negative control plasmid). Decreased expression of k-ras in HCT207ks, HCT535ks, and to a lesser extent in HCT689ks was proved by quantitative real-time PCR. Although in HCT207ks the cells were mostly in G0/G1 and G2/M phases, in HCT535ks and HCT689ks, the cells in the S phase were higher in comparison with nontransfected HCT-116. Lethal doses of 5-FU in HCT-116 and HCT-Sc were 2.5-3 and 3-3.5 µmol/l, whereas in HCT207ks, HCT535ks, and HCT689ks, they were 35-40, 37.5-40, and 22.5-25 µmol/l. In conclusion, silencing mutant and wild-type k-ras would increase the resistance of HCT-116 cell line as a model of colorectal cancer to 5-FU. The degree of resistance was related directly to the k-ras mRNA level. Therefore, both mutant and wild-type k-ras may play a role in sensitizing colorectal cancer cells to 5-FU as a common chemotherapeutic drug.
authors.affiliation: aDepartment of Medical Biotechnology, School of Advanced Technologies in Medicine bBiosensor Research Center, Endocrinology and Metabolism Cellular and Molecular Science Institute, Tehran University of Medical Sciences cMolecular Medicine Department, Biotechnology Research Center dVirology Department, Pasteur Institute of Iran, Tehran, Iran.
authors.forename: Ladan
authors.initials: L
authors.lastname: Teimoori-Toolabi
authors.forename: Saba
authors.initials: S
authors.lastname: Hashemi
authors.forename: Kayhan
authors.initials: K
authors.lastname: Azadmanesh
authors.forename: Farnaz
authors.initials: F
authors.lastname: Eghbalpour
authors.forename: Farnaz
authors.initials: F
authors.lastname: Safavifar
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Khorramizadeh
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D049109:Cell Proliferation / Q000187:drug effects; D015536:Down-Regulation / Q000235:genetics; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics*; D005472:Fluorouracil / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D020868:Gene Silencing; D011905:Genes, ras; D005839:Gentamicins / Q000494:pharmacology; D045325:HCT116 Cells / Q000187:drug effects; D006801:Humans; D009154:Mutation; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D000964:Antimetabolites, Antineoplastic; D005839:Gentamicins; C010680:antibiotic G 418; D005472:Fluorouracil