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A Genetically Engineered Mouse Model of Sporadic Colorectal Cancer
Published on: July 6, 2017
Detection of transforming oncogenes in rat colon tumors induced by direct perfusion with N-methyl-N-nitrosourea
R J Alexander1, S J Garte, R F Raicht
1Research Service, D.V.A. Medical Center, New York, NY 10010.
Abstract:
We assayed rat colon tumors induced by N-methyl-N-nitrosourea (MNU) for transforming oncogenes by the NIH 3T3 transfection and nude mouse tumorigenicity assays. Transfection of DNA from 3 of 3 adenomas and 3 of 5 carcinomas induced transformed foci on NIH 3T3 cells. DNA from 2 of 3 primary foci also possessed focus-forming activity, and rat-specific sequences were observed in secondary focus DNAs. Furthermore, NIH 3T3 cells transfected with DNA from a carcinoma and from a primary focus derived from it, both positive in the focus-forming assay, induced tumors in nude mice. We found no evidence for rat H-ras, K-ras, or N-ras sequences in the DNA of any of 16 primary foci derived from 6 rat tumors; thus, in contrast to other animal tumor models induced by MNU, activation of the ras genes does not appear to predominantly occur in MNU-induced rat colon tumors. We also did not observe, in any of these foci, sequences corresponding to the rat neu, raf, fms, met, or hst genes, thus indicating that none of these is the transforming oncogene in our model. These results suggest that an as yet unidentified transforming oncogene may be activated in rat colon tumors induced by MNU.
Insights
Researchers investigated oncogenes in rat colon tumors induced by N-methyl-N-nitrosourea (MNU). They found no evidence of ras gene activation, suggesting an unidentified transforming oncogene is involved in MNU-induced rat colon cancer.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- N-methyl-N-nitrosourea (MNU) is a chemical mutagen used to induce tumors in experimental models.
- Identifying transforming oncogenes is crucial for understanding cancer development and for therapeutic target discovery.
Purpose of the Study:
- To identify transforming oncogenes in rat colon tumors induced by MNU.
- To investigate the role of ras family genes and other known oncogenes in this specific tumor model.
Main Methods:
- NIH 3T3 transfection assay to detect focus-forming transforming activity in tumor DNA.
- Nude mouse tumorigenicity assay to confirm the transforming potential of transfected NIH 3T3 cells.
- Polymerase chain reaction (PCR) and DNA sequencing to screen for specific oncogene sequences (ras, neu, raf, fms, met, hst).
Main Results:
- DNA from rat colon adenomas and carcinomas induced NIH 3T3 cell transformation.
- Transfected NIH 3T3 cells from positive foci induced tumors in nude mice.
- No evidence of H-ras, K-ras, N-ras, neu, raf, fms, met, or hst gene activation was found in the analyzed tumor samples.
Conclusions:
- The study suggests that ras gene family activation is not the predominant mechanism in MNU-induced rat colon tumors.
- An as yet unidentified transforming oncogene is likely responsible for tumor development in this model.
- Further research is needed to identify the novel oncogene involved in MNU-induced rat colon carcinogenesis.
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