Both hMutSα and hMutSß DNA mismatch repair complexes participate in 5-fluorouracil cytotoxicity

• Published in: PloS one Vol. 6; no. 12; p. e28117
• Main Authors: Tajima, Akihiro, Iwaizumi, Moriya, Tseng-Rogenski, Stephanie, Cabrera, Betty L, Carethers, John M
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 02.12.2011; Public Library of Science (PLoS)
• Subjects: 5-Fluorouracil; Antimetabolites, Antineoplastic - pharmacology; Antineoplastic Agents - pharmacology; Apoptosis; Assaying; Baculoviridae - genetics; Baculovirus; Binding; Biology; Cancer therapies; Cell cycle; Cell death; Cell Line, Tumor; Chemotherapy; Cisplatin; Colonic Neoplasms - drug therapy; Colorectal cancer; Cross-Linking Reagents - pharmacology; Crosslinking; Cytotoxicity; Deoxyribonucleic acid; DNA; DNA Mismatch Repair; DNA repair; DNA-Binding Proteins - genetics; DNA-Binding Proteins - physiology; Drugs; Fluorouracil - pharmacology; Gastroenterology; Humans; Internal medicine; Medical prognosis; Medicine; Microsatellite Repeats - genetics; Mismatch repair; Mutation; Oligonucleotides; Oligonucleotides - chemistry; Patients; Psoralen; Recombinant Proteins - chemistry; Repair; Saccharomyces cerevisiae; Surface Plasmon Resonance; Tetrazolium Salts - pharmacology; Thiazoles - pharmacology; Toxicity; Treatment Outcome; Tumors; Yeast; La Jolla California; California; Ann Arbor Michigan; United States > US; Michigan
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0028117

Patients with advanced microsatellite unstable colorectal cancers do not show a survival benefit from 5-fluorouracil (5-FU)-based chemotherapy. We and others have shown that the DNA mismatch repair (MMR) complex hMutSα binds 5-FU incorporated into DNA. Although hMutSß is known to interact with interstrand crosslinks (ICLs) induced by drugs such as cisplatin and psoralen, it has not been demonstrated to interact with 5-FU incorporated into DNA. Our aim was to examine if hMutSß plays a role in 5-FU recognition. We compared the normalized growth of 5-FU treated cells containing either or both mismatch repair complexes using MTT and clonogenic assays. We utilized oligonucleotides containing 5-FU and purified baculovirus-synthesized hMutSα and hMutSß in electromobility shift assays (EMSA) and further analyzed binding using surface plasmon resonance. MTT and clonogenic assays after 5-FU treatment demonstrated the most cytotoxicity in cells with both hMutSα and hMutSß, intermediate cytotoxicity in cells with hMutSα alone, and the least cytotoxicity in cells with hMutSß alone, hMutSß binds 5-FU-modified DNA, but its relative binding is less than the binding of 5-FU-modified DNA by hMutSα. Cytotoxicity induced by 5-FU is dependent on intact DNA MMR, with relative cell death correlating directly with hMutSα and/or hMutSß 5-FU binding ability (hMutSα>hMutSß). The MMR complexes provide a hierarchical chemosensitivity for 5-FU cell death, and may have implications for treatment of patients with certain MMR-deficient tumors.