Elevated K-ras activity with cholestyramine and lovastatin, but not konjac mannan or niacin in lung--importance of mouse strain.
Our previous work established that hypocholesterolemic agents altered K-ras intracellular localization in lung. Here, we examined K-ras activity to define further its potential importance in lung carcinogenesis. K-ras activity in lungs from male A/J, Swiss and C57BL/6 mice was examined. For 3 weeks, mice consumed either 2 or 4% cholestyramine (CS), 1% niacin, 5% konjac mannan (KM), or were injected with lovastatin 25mg/kg three or five times weekly (Lov-3X and Lov-5X). A pair-fed (PF) group was fed the same quantity of diet consumed by the Lov-5X mice to control for lower body weights in Lov-5X mice. After 3 weeks, serum cholesterol was assayed with a commercial kit. Activated K-ras protein from lung was affinity precipitated with a Raf-1 ras binding domain-glutathione-S-transferase fusion protein bound to glutathione-agarose beads, followed by Western blotting, K-ras antibody treatment, and chemiluminescent detection. Only KM reduced serum cholesterol (in two of three mouse strains). In C56BL/6 mice treated with Lov-3X, lung K-ras activity increased 1.8-fold versus control (p=0.009). In normal lung with wild-type K-ras, this would be expected to be associated with maintenance of differentiation. In A/J mice fed 4% CS, K-ras activity increased 2.1-fold (p=0.02), which might be responsible for the reported enhancement of carcinogenesis in carcinogen-treated rats fed CS. KM feeding and PF treatment had no significant effects on K-ras activity. These data are consistent with the concept that K-ras in lung has an oncogenic function when mutated, but may act as a tumor suppressor when wild-type.
Calvert
Richard J
RJ
Division of Research and Applied Technology, Office of Nutritional Products, Labeling, and Dietary Supplements, Center for Food Safety and Applied Nutrition, US Food and Drug Administration, College Park, MD 20740, USA. calvert@mail.ncifcrf.gov
Tepper
Shirley
S
Kammouni
Wafa
W
Anderson
Lucy M
LM
Kritchevsky
David
D
D000818:Animals; D000924:Anticholesteremic Agents / Q000494:pharmacology*; D015153:Blotting, Western; D001835:Body Weight / Q000187:drug effects; D002784:Cholesterol / Q000097:blood; D002792:Cholestyramine Resin / Q000494:pharmacology*; D004587:Electrophoresis, Agar Gel; D008148:Lovastatin / Q000494:pharmacology*; D008168:Lung / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008351:Mannans / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009525:Niacin / Q000494:pharmacology*; D013045:Species Specificity; D018631:ras Proteins / Q000378:metabolism*
D000924:Anticholesteremic Agents; D008351:Mannans; D002792:Cholestyramine Resin; D009525:Niacin; C022901:(1-6)-alpha-glucomannan; D002784:Cholesterol; D008148:Lovastatin; D018631:ras Proteins