E2F4 and ribonucleotide reductase mediate S-phase arrest in colon cancer cells treated with chlorophyllin

Korakod Chimploy, G. Dario Díaz, Qingjie Li, Orianna Carter, Wan Mohaiza Dashwood, Christopher K. Mathews, David E. Williams, George S. Bailey, Roderick H. Dashwood

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Chlorophyllin (CHL) is a water-soluble derivative of chlorophyll that exhibits cancer chemopreventive properties, but which also has been studied for its possible cancer therapeutic effects. We report here that human colon cancer cells treated with CHL accumulate in S-phase of the cell cycle, and this is associated with reduced expression levels of p53, p21, and other G1/S checkpoint controls. At the same time, E2F1 and E2F4 transcription factors become elevated and exhibit increased DNA binding activity. In CHL-treated colon cancer cells, bromodeoxyuridine pulse-chase experiments provided evidence for the inhibition of DNA synthesis. Ribonucleotide reductase (RR), a pivotal enzyme for DNA synthesis and repair, was reduced at the mRNA and protein level after CHL treatment, and the enzymatic activity was inhibited in a concentration-dependent manner both in vitro and in vivo. Immunoblotting revealed that expression levels of RR subunits R1, R2, and p53R2 were reduced by CHL treatment in HCT116 (p53+/+) and HCT116 (p53-/-) cells, supporting a p53-independent mechanism. Prior studies have shown that reduced levels of RR small subunits can increase the sensitivity of colon cancer cells to clinically used DNA-damaging agents and RR inhibitors. We conclude that by inhibiting R1, R2, and p53R2, CHL has the potential to be effective in the clinical setting, when used alone or in combination with currently available cancer therapeutic agents.

Original languageEnglish (US)
Pages (from-to)2086-2094
Number of pages9
JournalInternational Journal of Cancer
Volume125
Issue number9
DOIs
StatePublished - Nov 1 2009
Externally publishedYes

Fingerprint

Ribonucleotide Reductases
S Phase
Colonic Neoplasms
E2F4 Transcription Factor
DNA
E2F1 Transcription Factor
DNA Repair Enzymes
HCT116 Cells
Neoplasms
Therapeutic Uses
Bromodeoxyuridine
Chlorophyll
Immunoblotting
chlorophyllin
Cell Cycle
Messenger RNA
Water
Proteins

Keywords

  • Chlorophyllin
  • Colorectal cancer
  • Rb/E2F pathway
  • Ribonucleotide reductase

ASJC Scopus subject areas

  • Cancer Research
  • Oncology
  • Medicine(all)

Cite this

Chimploy, K., Díaz, G. D., Li, Q., Carter, O., Dashwood, W. M., Mathews, C. K., ... Dashwood, R. H. (2009). E2F4 and ribonucleotide reductase mediate S-phase arrest in colon cancer cells treated with chlorophyllin. International Journal of Cancer, 125(9), 2086-2094. https://doi.org/10.1002/ijc.24559

E2F4 and ribonucleotide reductase mediate S-phase arrest in colon cancer cells treated with chlorophyllin. / Chimploy, Korakod; Díaz, G. Dario; Li, Qingjie; Carter, Orianna; Dashwood, Wan Mohaiza; Mathews, Christopher K.; Williams, David E.; Bailey, George S.; Dashwood, Roderick H.

In: International Journal of Cancer, Vol. 125, No. 9, 01.11.2009, p. 2086-2094.

Research output: Contribution to journalArticle

Chimploy, K, Díaz, GD, Li, Q, Carter, O, Dashwood, WM, Mathews, CK, Williams, DE, Bailey, GS & Dashwood, RH 2009, 'E2F4 and ribonucleotide reductase mediate S-phase arrest in colon cancer cells treated with chlorophyllin', International Journal of Cancer, vol. 125, no. 9, pp. 2086-2094. https://doi.org/10.1002/ijc.24559
Chimploy, Korakod ; Díaz, G. Dario ; Li, Qingjie ; Carter, Orianna ; Dashwood, Wan Mohaiza ; Mathews, Christopher K. ; Williams, David E. ; Bailey, George S. ; Dashwood, Roderick H. / E2F4 and ribonucleotide reductase mediate S-phase arrest in colon cancer cells treated with chlorophyllin. In: International Journal of Cancer. 2009 ; Vol. 125, No. 9. pp. 2086-2094.
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AU - Díaz, G. Dario

AU - Li, Qingjie

AU - Carter, Orianna

AU - Dashwood, Wan Mohaiza

AU - Mathews, Christopher K.

AU - Williams, David E.

AU - Bailey, George S.

AU - Dashwood, Roderick H.

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AB - Chlorophyllin (CHL) is a water-soluble derivative of chlorophyll that exhibits cancer chemopreventive properties, but which also has been studied for its possible cancer therapeutic effects. We report here that human colon cancer cells treated with CHL accumulate in S-phase of the cell cycle, and this is associated with reduced expression levels of p53, p21, and other G1/S checkpoint controls. At the same time, E2F1 and E2F4 transcription factors become elevated and exhibit increased DNA binding activity. In CHL-treated colon cancer cells, bromodeoxyuridine pulse-chase experiments provided evidence for the inhibition of DNA synthesis. Ribonucleotide reductase (RR), a pivotal enzyme for DNA synthesis and repair, was reduced at the mRNA and protein level after CHL treatment, and the enzymatic activity was inhibited in a concentration-dependent manner both in vitro and in vivo. Immunoblotting revealed that expression levels of RR subunits R1, R2, and p53R2 were reduced by CHL treatment in HCT116 (p53+/+) and HCT116 (p53-/-) cells, supporting a p53-independent mechanism. Prior studies have shown that reduced levels of RR small subunits can increase the sensitivity of colon cancer cells to clinically used DNA-damaging agents and RR inhibitors. We conclude that by inhibiting R1, R2, and p53R2, CHL has the potential to be effective in the clinical setting, when used alone or in combination with currently available cancer therapeutic agents.

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