Decrease in K-ras p21 and increase in Raf1 and activated Erk 1 and 2 in murine lung tumors initiated by N-nitrosodimethylamine and promoted by 2,3,7,8-tetrachlorodibenzo-p-dioxin.

Abstract

Recent evidence suggests that K-ras protooncogene protein p21 may have a tumor-suppressive role in the context of development of lung adenocarcinoma. Levels of K-ras p21, raf-1, mitogen-activated protein kinases Erk 1 and 2, the phosphorylated-activated forms of Erk 1 and 2 (Erk 1P and 2P), and proliferating cell nuclear antigen (PCNA) were measured by immunoblotting in mouse lung tumors (5 to 9 mm in size) caused by N-nitrosodimethylamine (NDMA) and in control lungs. In tumors compared with normal lung, cell membrane-associated K-ras p21 was significantly decreased and cytosolic K-ras p21 increased. Total, membrane, and cytosolic raf-1 and Erk 1P and 2P were increased in tumors compared with normal lung. A single dose of 5 nmol/kg 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) given after NDMA resulted in a significant 2.4-fold increase in tumor multiplicity. A significantly greater decrease in membrane-associated K-ras p21 and increase in total and membrane associated raf-1 occurred in the NDMA/TCDD tumors compared with the NDMA-only tumors. PCNA levels increased in tumors, a finding confirmed by immunohistochemistry, and correlated with tumor size after NDMA/TCDD treatment but not after NDMA only. The increase in raf-1 in the tumors was confirmed by immunohistochemistry, which also revealed an increase in raf-1-positive alveolar macrophages specifically associating with tumors from the earliest stages. These results suggest a possible tumor-suppressive function for K-ras p21 in lung and a positive role for raf-1 and Erk 1/2 in lung tumorigenesis. TCDD may promote tumors by contributing to downregulation of K-ras and stimulation of raf-1.

• Authors: Gayatri Ramakrishna, Christine Perella, Lisa Birely, Bhalchandra A Diwan, Laura W Fornwald, Lucy M Anderson
• Journal: Toxicology and applied pharmacology (Toxicol Appl Pharmacol) Vol. 179 Issue 1 Pg. 21-34 (Feb 15 2002) ISSN: 0041-008X [Print] United States
• PMID: 11884234 (Publication Type: Journal Article)

Chemical References

• Carcinogens
• Polychlorinated Dibenzodioxins
• Proliferating Cell Nuclear Antigen
• Proto-Oncogene Proteins c-raf
• proto-oncogene protein v-RAF1, pig
• Mitogen-Activated Protein Kinase 1
• Mitogen-Activated Protein Kinase 3
• Mitogen-Activated Protein Kinases
• Oncogene Protein p21(ras)
• Dimethylnitrosamine

Topics

• Animals
• Carcinogens (toxicity)
• DNA Mutational Analysis
• Dimethylnitrosamine (toxicity)
• Gene Expression Regulation, Neoplastic (drug effects)
• Immunoblotting
• Immunohistochemistry
• Lung Neoplasms (chemically induced, genetics, pathology)
• Male
• Mice
• Mitogen-Activated Protein Kinase 1 (biosynthesis, genetics)
• Mitogen-Activated Protein Kinase 3
• Mitogen-Activated Protein Kinases (biosynthesis, genetics)
• Oncogene Protein p21(ras) (biosynthesis, genetics)
• Polychlorinated Dibenzodioxins (toxicity)
• Proliferating Cell Nuclear Antigen (metabolism)
• Proto-Oncogene Proteins c-raf (biosynthesis, genetics)