Arsenic trioxide suppresses thymidylate synthase in 5-FU-resistant colorectal cancer cell line HT29 In Vitro re-sensitizing cells to 5-FU.
Identification of new agents with antitumor activity in chemoresistant tumors is urgently needed for the treatment of colorectal cancer. Arsenic trioxide (As(2)O(3)), a Food and Drug Administration (FDA) approved drug is successfully being used to treat acute promyelocytic leukemia (APL). Several clinical trials also suggest its ineffectiveness on solid tumors. We proposed that arsenic trioxide may be used as chemosensitizer, especially to 5-fluorouracil (5-FU). The effect of arsenic trioxide on cell proliferation of 5-FU-sensitive and -resistant HT29 colorectal cancer cells in vitro was tested by trypan blue dye exclusion assay, 2, 3-bis(2-methoxy-4-nitro-5-sulfophenyl)-S-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide (XTT) cell proliferation assay and cell cycle analysis using flow cytometry. Gene expression was analyzed using real-time polymerase chain reaction (PCR) and Western blot methods. There was a dose-dependent increase in cell detachment and proliferation in HT29 and HT29FU cells. As a single agent, arsenic trioxide also down-regulated thymidylate synthase (TS) expression without affecting the expression of some other genes analyzed in the above cell lines. Combination of arsenic trioxide and 5-FU increased cytotoxicity. In vitro data show that as a single agent, arsenic trioxide down-regulated TS expression in HT29 cells. Addition of 5-FU to these sensitized cells increased cytotoxicity. These findings open up a possibility to use arsenic trioxide as a chemosensitizer in combination therapy.
Subbarayan
Pochi Ramalingam
PR
Department of Medicine, Division of Hematology and Oncology, University of Miami School of Medicine, Miami, FL 33136, USA. spochi@med.miami.edu
Lee
Kelvin
K
Ardalan
Bach
B
D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D000077237:Arsenic Trioxide; D001152:Arsenicals / Q000008:administration & dosage / Q000494:pharmacology*; D015153:Blotting, Western; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000201:enzymology*; D019008:Drug Resistance, Neoplasm; D004357:Drug Synergism; D005472:Fluorouracil / Q000008:administration & dosage / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D019073:HT29 Cells; D006801:Humans; D010087:Oxides / Q000008:administration & dosage / Q000494:pharmacology*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013940:Thymidylate Synthase / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis / Q000235:genetics
D001152:Arsenicals; D010087:Oxides; D012333:RNA, Messenger; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D013940:Thymidylate Synthase; D000077237:Arsenic Trioxide; D005472:Fluorouracil