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n-6 and n-3 polyunsaturated fatty acids differentially modulate oncogenic Ras activation in colonocytes.
E D Collett1, L A Davidson, Y Y Fan
1Molecular and Cell Biology Group, Faculty of Nutrition, and Center for Environmental and Rural Health, Texas A&M University, College Station, Texas 77843-2471, USA.
American Journal of Physiology. Cell Physiology
|April 5, 2001
Summary
Dietary fish oil, rich in docosahexaenoic acid (DHA), reduces colon cancer risk by decreasing Ras membrane localization and downstream signaling. This contrasts with corn oil
Area of Science:
- Molecular Biology
- Oncology
- Nutrition Science
Background:
- Ras proteins are key regulators of cell growth and differentiation; their membrane localization is essential for malignant transformation.
- Dietary fish oil, compared to corn oil, has been shown to decrease colonic Ras membrane localization and reduce tumor formation.
- Ras protein activity is modulated by posttranslational lipid modification and interactions with lipids.
Purpose of the Study:
- To investigate whether docosahexaenoic acid (DHA) from fish oil, versus linoleic acid (LA) from corn oil, alters Ras posttranslational processing, activation, and effector protein function.
- To examine the effects of DHA and LA on Ras signaling pathways in colon cells.
Main Methods:
- Utilized young adult mouse colon cells overexpressing H-ras (YAMC-ras).
- Compared the effects of DHA (n-3 PUFA) and LA (n-6 PUFA) on Ras protein localization, lipidation, GTP binding, and downstream signaling.
- Assessed p42/44(ERK)-dependent signaling pathways.
Main Results:
- DHA significantly reduced Ras localization to the plasma membrane compared to LA, without altering posttranslational lipidation.
- DHA decreased Ras-GTP binding, indicating reduced activation.
- Downstream signaling, specifically p42/44(ERK)-dependent pathways, was lowered by DHA.
Conclusions:
- Docosahexaenoic acid (DHA) differentially modulates Ras activation compared to linoleic acid (LA).
- Reduced Ras membrane localization and activation by DHA may contribute to the protective effects of dietary fish oil against colon cancer.
- These findings highlight the role of dietary polyunsaturated fatty acids in cancer prevention through modulation of key oncogenic signaling pathways.