Production of truncated MBD4 protein by frameshift mutation in DNA mismatch repair-deficient cells enhances 5-fluorouracil sensitivity that is independent of hMLH1 status.
Methyl-CpG binding domain protein 4 (MBD4) is a DNA glycosylase that can remove 5-fluorodeoxyuracil from DNA as well as repair T:G or U:G mismatches. MBD4 is a target for frameshift mutation with DNA mismatch repair (MMR) deficiency, creating a truncated MBD4 protein (TruMBD4) that lacks its glycosylase domain. Here we show that TruMBD4 plays an important role for enhancing 5-fluorouracil (5FU) sensitivity in MMR-deficient colorectal cancer cells. We found biochemically that TruMBD4 binds to 5FU incorporated into DNA with higher affinity than MBD4. TruMBD4 reduced the 5FU affinity of the MMR recognition complexes that determined 5FU sensitivity by previous reports, suggesting other mechanisms might be operative to trigger cytotoxicity. To analyze overall 5FU sensitivity with TruMBD4, we established TruMBD4 overexpression in hMLH1-proficient or -deficient colorectal cancer cells followed by treatment with 5FU. 5FU-treated TruMBD4 cells demonstrated diminished growth characteristics compared to controls, independently of hMLH1 status. Flow cytometry revealed more 5FU-treated TruMBD4 cells in S phase than controls. We conclude that patients with MMR-deficient cancers, which show characteristic resistance to 5FU therapy, may be increased for 5FU sensitivity via secondary frameshift mutation of the base excision repair gene MBD4.
a First Department of Medicine , Hamamatsu University School of Medicine , Hamamatsu , Shizuoka , Japan.
Satoshi
S
Suzuki
a First Department of Medicine , Hamamatsu University School of Medicine , Hamamatsu , Shizuoka , Japan.|b Division of Gastroenterology, Department of Internal Medicine and Department of Human Genetics, University of Michigan , Ann Arbor , MA , USA.
Moriya
M
Iwaizumi
b Division of Gastroenterology, Department of Internal Medicine and Department of Human Genetics, University of Michigan , Ann Arbor , MA , USA.
Stephanie
S
Tseng-Rogenski
a First Department of Medicine , Hamamatsu University School of Medicine , Hamamatsu , Shizuoka , Japan.|b Division of Gastroenterology, Department of Internal Medicine and Department of Human Genetics, University of Michigan , Ann Arbor , MA , USA.
Yasushi
Y
Hamaya
a First Department of Medicine , Hamamatsu University School of Medicine , Hamamatsu , Shizuoka , Japan.
Hiroaki
H
Miyajima
c Department of Gastroenterology , Hamamatsu Medical Center , Shizuoka , Japan.
Shigeru
S
Kanaoka
a First Department of Medicine , Hamamatsu University School of Medicine , Hamamatsu , Shizuoka , Japan.
Ken
K
Sugimoto
b Division of Gastroenterology, Department of Internal Medicine and Department of Human Genetics, University of Michigan , Ann Arbor , MA , USA.
John M
JM
Carethers
D015179:Colorectal Neoplasms / Q000188:drug therapy / Q000235:genetics*; D053843:DNA Mismatch Repair; D004706:Endodeoxyribonucleases / Q000235:genetics* / Q000378:metabolism; D005472:Fluorouracil / Q000627:therapeutic use*; D016368:Frameshift Mutation; D006801:Humans; D000070957:MutL Protein Homolog 1 / Q000235:genetics* / Q000378:metabolism; D014162:Transfection
C501486:MLH1 protein, human; D004706:Endodeoxyribonucleases; C118712:MBD4 protein, human; D000070957:MutL Protein Homolog 1; D005472:Fluorouracil
5-fluorouracil; Colorectal cancer; DNA mismatch repair; MBD4; cytotoxicity; frameshift mutation; truncated protein