Molecular biomarkers for the prevention of mouse lung tumors by budesonideaDepartment of Pathology, Medical College of Ohio, Toledo, OH bChemoprevention Agent Development Research Group, National Cancer Institute, Bethesda, MD
The discovery of chemopreventive drugs could be expedited by the use of biomarkers that demonstrate chemopreventive efficacy. The modulation of biomarkers by budesonide in mouse lung tumors was determined. Female strain A mice were administered 16 mg/kg vinyl carbamate for two consecutive weeks. Budesonide (2.4 mg/kg diet, a dose that prevented lung tumors in mice) was administered for only the last seven days prior to sacrifice at Week 35. The Proliferating Cell Nuclear Antigen (PCNA)-labeling Index was decreased by budesonide in carcinomas (59.0%), adenomas (77.6%), airways (25.4%), and parenchyma (41.1%). In lung tumors, budesonide increased the protein level of p21(Cip1/Waf1/sdi1) and p27(Kip1) and the mRNA level of p21. Using the bisulfite-treated DNA sequencing procedure, normal lung tissue had ~20 of 24 CpG sites methylated in the differentially methylated region 2 of the insulin-like growth factor-2 (IGF-II) gene. Lung tumors had only 0-2 of the CpG sites methylated, while budesonide increased the number of methylated sites to 13-16. Hpa II digestion of DNA from normal lung tissue did not result in any bands on Southern blot analysis when probed for c-myc, while three bands were present in digested DNA from lung tumors. Budesonide decreased the intensity of the three bands from DNA. Thus, potential biomarkers for chemoprevention of lung cancer include the ability to increase the protein levels of p21 and p27, the mRNA level of p21 and the methylation of the IGF-II and c-myc genes in tumors, and to decrease the PCNA-labeling in tumors and normal appearing airways and parenchyma
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Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Prevention.