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Systemic alterations in ornithine decarboxylase activity caused by colon cancer in mice
R Saydjari1, R D Beauchamp, C M Townsend
1Department of Surgery, University of Texas Medical Branch, Galveston 77550.
Abstract:
Tumors are known to cause profound changes in host biology, but the mechanisms responsible for these changes remain unclear. Ornithine decarboxylase (ODC) is a rate-limiting enzyme that catalyzes the biosynthesis of polyamines. The purpose of this study was to examine the effects of MC-26 tumor burden on ODC activity in the gastrointestinal tract, kidney and liver of mice. Forty-four Balb/c mice were randomly divided into 2 groups and the test group was pair-fed (to control). Group 1 was the tumor-free control. Group 2 was inoculated subcutaneously with 5 x 10(5) MC-26 cells. The ODC activity in the kidney and liver of tumor-bearing mice was significantly lower compared to tumor-free controls at sacrifice. ODC activity in the colon increased almost 4-fold. These results suggest that the presence of MC-26 tumor causes systemic effects that alter ODC activity. The tumor may elaborate a substance that suppresses ODC activity in some normal tissues while stimulating ODC activity in the tissue from which the tumor was derived.
Insights
Tumor presence significantly alters ornithine decarboxylase (ODC) activity. While ODC activity decreased in the kidney and liver, it increased substantially in the colon of tumor-bearing mice.
Area of Science:
- Biochemistry
- Oncology
- Physiology
Background:
- Tumors induce significant host biology alterations.
- Mechanisms behind tumor-induced biological changes are not fully understood.
- Ornithine decarboxylase (ODC) is a key enzyme in polyamine biosynthesis.
Purpose of the Study:
- To investigate the impact of MC-26 tumor burden on ODC activity.
- To assess ODC activity across the gastrointestinal tract, kidney, and liver in mice.
Main Methods:
- Forty-four Balb/c mice were divided into tumor-free control and MC-26 tumor-inoculated groups.
- The tumor group received 5 x 10(5) MC-26 cells subcutaneously.
- Pair-feeding was employed to control for dietary intake in the test group.
Main Results:
- Tumor-bearing mice exhibited significantly lower ODC activity in the kidney and liver compared to controls.
- ODC activity in the colon of tumor-bearing mice increased nearly fourfold.
- These findings indicate systemic effects of tumor presence on ODC activity.
Conclusions:
- MC-26 tumor burden causes differential systemic effects on ODC activity.
- The tumor may secrete factors that suppress ODC in some organs while stimulating it in others.
- Further research is needed to elucidate the specific mechanisms involved.