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Modulation of growth gene expression by selective alteration of polyamines in human colon carcinoma cells
P Celano1, C M Berchtold, F M Giardiello
1Johns Hopkins Oncology Center, Baltimore, Maryland.
Abstract:
The biosynthesis of the polyamines, putrescine, spermidine and spermine, is temporally linked with expression of many growth related genes. Our previous studies have shown that generalized polyamine depletion of the human colon cancer cell line COLO 320 by 2-difluoromethylornithine is associated with decreased transcription of the c-myc, c-fos, and ornithine decarboxylase (ODC) genes. In the current study, the role of individual polyamines was further defined by the use of a specific inhibitor of spermidine synthase, S-adenosyl-1,8, diamino-3-thio-octane (AdoDATO), and a spermine analogue, N1,N12 bis(ethyl)spermine. Our data demonstrate that depletion of spermidine results in a 60-90% decrease in c-myc mRNA steady state levels. In contrast, c-fos mRNA levels are decreased only when both spermidine and spermine are diminished. Furthermore, ODC mRNA levels are increased when all polyamines are decreased by DFMO, but are unaffected by a selective reduction in intracellular spermidine levels by AdoDATO. These studies suggest that individual polyamines may have a selective role in the expression of specific growth related genes.
Insights
Polyamines like spermidine and spermine influence cancer gene expression. Depleting spermidine significantly reduces c-myc mRNA, impacting cell growth and gene regulation.
Area of Science:
- Molecular Biology
- Cancer Research
- Biochemistry
Background:
- Polyamines (putrescine, spermidine, spermine) are crucial for cell growth and gene expression.
- Previous work linked polyamine depletion to reduced transcription of growth-related genes like c-myc and c-fos.
Purpose of the Study:
- To investigate the specific roles of individual polyamines in regulating growth-related gene expression in colon cancer cells.
- To differentiate the effects of spermidine and spermine depletion on c-myc, c-fos, and ornithine decarboxylase (ODC) mRNA levels.
Main Methods:
- Utilized specific inhibitors: S-adenosyl-1,8, diamino-3-thio-octane (AdoDATO) for spermidine synthase and N1,N12 bis(ethyl)spermine as a spermine analogue.
- Assessed mRNA steady-state levels of c-myc, c-fos, and ODC in COLO 320 cells under varying polyamine conditions.
Main Results:
- Selective spermidine depletion caused a 60-90% decrease in c-myc mRNA.
- c-fos mRNA levels decreased only when both spermidine and spermine were reduced.
- ODC mRNA increased with general polyamine depletion (DFMO) but remained unaffected by isolated spermidine reduction.
Conclusions:
- Individual polyamines play distinct roles in regulating specific growth-related genes.
- Spermidine is a key regulator of c-myc expression.
- The interplay between spermidine and spermine influences c-fos regulation.