Calbindin 2 (CALB2) Regulates 5-fluorouracil Sensitivity in Colorectal Cancer by Modulating the Intrinsic Apoptotic Pathway

PLoS One. 2011;6(5):e20276. doi: 10.1371/journal.pone.0020276. Epub 2011 May 24.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents / pharmacology
  • Apoptosis / drug effects*
  • Apoptosis / genetics
  • Blotting, Western
  • Caspase 3 / genetics
  • Caspase 3 / metabolism
  • Caspase 7 / genetics
  • Caspase 7 / metabolism
  • Caspase 9 / genetics
  • Caspase 9 / metabolism
  • Cell Survival / drug effects
  • Cell Survival / genetics
  • Colorectal Neoplasms / metabolism*
  • Cytochromes c / genetics
  • Cytochromes c / metabolism
  • Fluorouracil / pharmacology*
  • HCT116 Cells
  • Humans
  • Membrane Potential, Mitochondrial / drug effects
  • Oligonucleotide Array Sequence Analysis
  • RNA, Small Interfering
  • Reverse Transcriptase Polymerase Chain Reaction
  • X-Linked Inhibitor of Apoptosis Protein / genetics
  • X-Linked Inhibitor of Apoptosis Protein / metabolism

Substances

  • Antineoplastic Agents
  • RNA, Small Interfering
  • X-Linked Inhibitor of Apoptosis Protein
  • XIAP protein, human
  • Cytochromes c
  • Caspase 3
  • Caspase 7
  • Caspase 9
  • Fluorouracil