title: Calbindin 2 (CALB2) regulates 5-fluorouracil sensitivity in colorectal cancer by modulating the intrinsic apoptotic pathway.
abstract: The role of the calcium binding protein, Calbindin 2 (CALB2), in regulating the response of colorectal cancer (CRC) cells to 5-Fluorouracil (5-FU) was investigated. Real-time RT-PCR and Western blot analysis revealed that CALB2 mRNA and protein expression were down-regulated in p53 wild-type and p53 null isogenic HCT116 CRC cell lines following 48 h and 72 h 5-FU treatment. Moreover, 5-FU-induced apoptosis was significantly reduced in HCT116 and LS174T CRC cell lines in which CALB2 expression had been silenced. Further investigation revealed that CALB2 translocated to the mitochondria following 5-FU treatment and that 5-FU-induced loss of mitochondrial membrane potential (Δψ(m)) was abrogated in CALB2-silenced cells. Furthermore, CALB2 silencing decreased 5-FU-induced cytochrome c and smac release from the mitochondria and also decreased 5-FU-induced activation of caspases 9 and 3/7. Of note, co-silencing of XIAP overcame 5-FU resistance in CALB2-silenced cells. Collectively, these results suggest that following 5-FU treatment in CRC cell lines, CALB2 is involved in apoptosis induction through the intrinsic mitochondrial pathway. This indicates that CALB2 may be an important mediator of 5-FU-induced cell death. Moreover, down-regulation of CALB2 in response to 5-FU may represent an intrinsic mechanism of resistance to this anti-cancer drug.
authors.affiliation: Drug Resistance Group, Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland.
authors.forename: Leanne
authors.initials: L
authors.lastname: Stevenson
authors.forename: Wendy L
authors.initials: WL
authors.lastname: Allen
authors.forename: Irina
authors.initials: I
authors.lastname: Proutski
authors.forename: Gail
authors.initials: G
authors.lastname: Stewart
authors.forename: Louise
authors.initials: L
authors.lastname: Johnston
authors.forename: Karen
authors.initials: K
authors.lastname: McCloskey
authors.forename: Peter M
authors.initials: PM
authors.lastname: Wilson
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Longley
authors.forename: Patrick G
authors.initials: PG
authors.lastname: Johnston
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D015153:Blotting, Western; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D053179:Caspase 7 / Q000235:genetics / Q000378:metabolism; D053453:Caspase 9 / Q000235:genetics / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D015179:Colorectal Neoplasms / Q000378:metabolism*; D045304:Cytochromes c / Q000235:genetics / Q000378:metabolism; D005472:Fluorouracil / Q000494:pharmacology*; D045325:HCT116 Cells; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D020411:Oligonucleotide Array Sequence Analysis; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D034741:RNA, Small Interfering; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; D045304:Cytochromes c; D053148:Caspase 3; D053179:Caspase 7; D053453:Caspase 9; D005472:Fluorouracil