Conjugated Linoleic Acid Inhibits Cell Proliferation through a p53-Dependent Mechanism: Effects on the Expression of G1-Restriction Points in Breast and Colon Cancer Cells

Michael Q. Kemp, Brandon D. Jeffy, Donato Romagnolo

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Abstract

Previous reports have documented the antiproliferative properties of a mixture of conjugated isomers (CLA) of linoleic acid [LA (18: 2)]. In this study, we investigated the mechanisms of CLA action on cell cycle progression in breast and colon cancer cells. Treatment with CLA inhibited cell proliferation in breast cancer MCF-7 cells containing wild-type p53 (p53 +/+). At cytostatic concentrations, CLA elicited cell cycle arrest in G1 and induced the accumulation of the tumor suppressors p53, p27 and p21 protein. Conversely, CLA reduced the expression of factors required for G1 to S-phase transition including cyclins D1 and E, and hyperphoshorylated retinoblastoma Rb protein. In contrast, the overexpression of mutant p53 (175Arg to His) in MFC-7 cells prevented the CLA-dependent accumulation of p21 and the reduction of cyclin E levels suggesting that the expression of wild-type p53 is required for CLA-mediated activation of the G1 restriction point. To futher elucidate the role of p53, the effects of CLA in colon cancer HCT116 cells (p53+/+) and p53-deficient (p53-/-) HCT116 cells (HCTKO) were examined. The treatment of HCT116 cells with CLA increased the levels of p53, p21, p27 and hypophosphorylated (pRb) protein and reduced the expression of cyclin E, whereas these effects were not seen in p53-deficient HCTKO cells. The t10,c12-CLA isomer was more effective than c9,t11-CLA in inhibiting cell proliferation of MCF-7 breast cancer cells and enhancing the accumulation of p53 and pRb. We conclude that the antiproliferative properties of CLA appear to be a function, at least in part, of the relative content of specific isomers and their ability to elicit a p53 response that leads to the accumulation of pRb and cell growth arrest.

Original languageEnglish (US)
Pages (from-to)3670-3677
Number of pages8
JournalJournal of Nutrition
Volume133
Issue number11
StatePublished - Nov 2003

Fingerprint

G1 Phase Cell Cycle Checkpoints
Conjugated Linoleic Acids
conjugated linoleic acid
colorectal neoplasms
breast neoplasms
Colonic Neoplasms
cell proliferation
HCT116 Cells
Cyclin E
Cell Proliferation
Breast Neoplasms
cyclins
isomers
Retinoblastoma Protein
cells
proteins
Cyclin D1
Phase Transition
MCF-7 Cells
Cytostatic Agents

Keywords

  • Cell cycle arrest
  • Conjugated linoleic acid
  • G1/S
  • p53
  • Rb

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Food Science

Cite this

@article{55ef7cc2950b448482330a8e630ae52f,
title = "Conjugated Linoleic Acid Inhibits Cell Proliferation through a p53-Dependent Mechanism: Effects on the Expression of G1-Restriction Points in Breast and Colon Cancer Cells",
abstract = "Previous reports have documented the antiproliferative properties of a mixture of conjugated isomers (CLA) of linoleic acid [LA (18: 2)]. In this study, we investigated the mechanisms of CLA action on cell cycle progression in breast and colon cancer cells. Treatment with CLA inhibited cell proliferation in breast cancer MCF-7 cells containing wild-type p53 (p53 +/+). At cytostatic concentrations, CLA elicited cell cycle arrest in G1 and induced the accumulation of the tumor suppressors p53, p27 and p21 protein. Conversely, CLA reduced the expression of factors required for G1 to S-phase transition including cyclins D1 and E, and hyperphoshorylated retinoblastoma Rb protein. In contrast, the overexpression of mutant p53 (175Arg to His) in MFC-7 cells prevented the CLA-dependent accumulation of p21 and the reduction of cyclin E levels suggesting that the expression of wild-type p53 is required for CLA-mediated activation of the G1 restriction point. To futher elucidate the role of p53, the effects of CLA in colon cancer HCT116 cells (p53+/+) and p53-deficient (p53-/-) HCT116 cells (HCTKO) were examined. The treatment of HCT116 cells with CLA increased the levels of p53, p21, p27 and hypophosphorylated (pRb) protein and reduced the expression of cyclin E, whereas these effects were not seen in p53-deficient HCTKO cells. The t10,c12-CLA isomer was more effective than c9,t11-CLA in inhibiting cell proliferation of MCF-7 breast cancer cells and enhancing the accumulation of p53 and pRb. We conclude that the antiproliferative properties of CLA appear to be a function, at least in part, of the relative content of specific isomers and their ability to elicit a p53 response that leads to the accumulation of pRb and cell growth arrest.",
keywords = "Cell cycle arrest, Conjugated linoleic acid, G1/S, p53, Rb",
author = "Kemp, {Michael Q.} and Jeffy, {Brandon D.} and Donato Romagnolo",
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journal = "Journal of Nutrition",
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T1 - Conjugated Linoleic Acid Inhibits Cell Proliferation through a p53-Dependent Mechanism

T2 - Effects on the Expression of G1-Restriction Points in Breast and Colon Cancer Cells

AU - Kemp, Michael Q.

AU - Jeffy, Brandon D.

AU - Romagnolo, Donato

PY - 2003/11

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N2 - Previous reports have documented the antiproliferative properties of a mixture of conjugated isomers (CLA) of linoleic acid [LA (18: 2)]. In this study, we investigated the mechanisms of CLA action on cell cycle progression in breast and colon cancer cells. Treatment with CLA inhibited cell proliferation in breast cancer MCF-7 cells containing wild-type p53 (p53 +/+). At cytostatic concentrations, CLA elicited cell cycle arrest in G1 and induced the accumulation of the tumor suppressors p53, p27 and p21 protein. Conversely, CLA reduced the expression of factors required for G1 to S-phase transition including cyclins D1 and E, and hyperphoshorylated retinoblastoma Rb protein. In contrast, the overexpression of mutant p53 (175Arg to His) in MFC-7 cells prevented the CLA-dependent accumulation of p21 and the reduction of cyclin E levels suggesting that the expression of wild-type p53 is required for CLA-mediated activation of the G1 restriction point. To futher elucidate the role of p53, the effects of CLA in colon cancer HCT116 cells (p53+/+) and p53-deficient (p53-/-) HCT116 cells (HCTKO) were examined. The treatment of HCT116 cells with CLA increased the levels of p53, p21, p27 and hypophosphorylated (pRb) protein and reduced the expression of cyclin E, whereas these effects were not seen in p53-deficient HCTKO cells. The t10,c12-CLA isomer was more effective than c9,t11-CLA in inhibiting cell proliferation of MCF-7 breast cancer cells and enhancing the accumulation of p53 and pRb. We conclude that the antiproliferative properties of CLA appear to be a function, at least in part, of the relative content of specific isomers and their ability to elicit a p53 response that leads to the accumulation of pRb and cell growth arrest.

AB - Previous reports have documented the antiproliferative properties of a mixture of conjugated isomers (CLA) of linoleic acid [LA (18: 2)]. In this study, we investigated the mechanisms of CLA action on cell cycle progression in breast and colon cancer cells. Treatment with CLA inhibited cell proliferation in breast cancer MCF-7 cells containing wild-type p53 (p53 +/+). At cytostatic concentrations, CLA elicited cell cycle arrest in G1 and induced the accumulation of the tumor suppressors p53, p27 and p21 protein. Conversely, CLA reduced the expression of factors required for G1 to S-phase transition including cyclins D1 and E, and hyperphoshorylated retinoblastoma Rb protein. In contrast, the overexpression of mutant p53 (175Arg to His) in MFC-7 cells prevented the CLA-dependent accumulation of p21 and the reduction of cyclin E levels suggesting that the expression of wild-type p53 is required for CLA-mediated activation of the G1 restriction point. To futher elucidate the role of p53, the effects of CLA in colon cancer HCT116 cells (p53+/+) and p53-deficient (p53-/-) HCT116 cells (HCTKO) were examined. The treatment of HCT116 cells with CLA increased the levels of p53, p21, p27 and hypophosphorylated (pRb) protein and reduced the expression of cyclin E, whereas these effects were not seen in p53-deficient HCTKO cells. The t10,c12-CLA isomer was more effective than c9,t11-CLA in inhibiting cell proliferation of MCF-7 breast cancer cells and enhancing the accumulation of p53 and pRb. We conclude that the antiproliferative properties of CLA appear to be a function, at least in part, of the relative content of specific isomers and their ability to elicit a p53 response that leads to the accumulation of pRb and cell growth arrest.

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