Characteristics of the peroxisome proliferator activated receptor gamma (PPARgamma) ligand induced apoptosis in colon cancer cells.
BACKGROUND: Involvement of peroxisome proliferator activated receptor gamma (PPARgamma) in the growth response of colon cancer cells has been suggested. AIMS: To investigate the characteristics of PPARgamma induced apoptosis in colon cancer cells. METHODS: The effects of ligands for each of the PPAR subtypes (alpha, delta, and gamma) on DNA synthesis and cell viability were examined in HT-29 colon cancer cells. Modulation of apoptosis related gene expression by PPARgamma ligands was screened with cDNA arrays, and the results were confirmed by quantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis. RESULTS: PPARalpha, PPARdelta, and PPARgamma were all expressed in HT-29 cells. PPARgamma ligands, 15-deoxy-delta(12,)(14)-prostaglandin J2 (15d-PGJ2) and troglitazone (TGZ), suppressed DNA synthesis of HT-29 cells whereas ligands for PPARalpha and PPARdelta had no significant effects. Both 15d-PGJ2 and TGZ induced HT-29 cell death in a dose dependent manner which was associated with an increase in fragmented DNA and was sensitive to a caspase inhibitor. Among several genes selected by cDNA array screening, quantitative RT-PCR analysis confirmed downregulation of c-myc expression and upregulation of c-jun and gadd153 expression by 15d-PGJ2 and TGZ. PPARgamma induced apoptosis was antagonised by the presence of serum in the culture medium, and interaction between PPARgamma signalling and cell survival signalling through the phosphatidylinositol 3-kinase pathway was suggested. CONCLUSIONS: As c-myc is an important target gene of the adenomatous polyposis coli (APC)/beta-catenin and/or APC/gamma-catenin pathway, activation of PPARgamma signalling appears to compensate for deregulated c-myc expression caused by mutated APC. The present results suggest the potential usefulness of PPARgamma ligands for chemoprevention and treatment of colon cancers.[1]References
- Characteristics of the peroxisome proliferator activated receptor gamma (PPARgamma) ligand induced apoptosis in colon cancer cells. Shimada, T., Kojima, K., Yoshiura, K., Hiraishi, H., Terano, A. Gut (2002) [Pubmed]
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