Loss of Apc allows phenotypic manifestation of the transforming properties of an endogenous K-ras oncogene in vivo

Sansom, O. et al. (2006) Loss of Apc allows phenotypic manifestation of the transforming properties of an endogenous K-ras oncogene in vivo. Proceedings of the National Academy of Sciences of the United States of America, 103(38), pp. 14122-14127. (doi: 10.1073/pnas.0604130103)

Abstract

Oncogenic mutations in the K-ras gene occur in approximate to 50% of human colorectal cancers. However, the precise role that K-ras oncogenes play in tumor formation is still unclear. To address this issue, we have conditionally expressed an oncogenic K-ras(V12) allele in the small intestine of adult mice either alone or in the context of Apc deficiency. We found that expression of K-ras(V12) does not affect normal intestinal homeostasis or the immediate phenotypes associated with Apc deficiency. Mechanistically we failed to find activation of the Raf/MEK/ERK pathway, which may be a consequence of the up-regulation of a number of negative feedback loops. However, K-ras(V12) expression accelerates intestinal tumorigenesis and confers invasive properties after Apc loss over the long term. In renal epithelium, expression of the oncogenic K-ras(V12) allele in the absence of Apc induces the rapid development of renal carcinoma. These tumors, unlike those of intestinal origin, display activation of the Raf/MEK/ERK and Akt signaling pathways. Taken together, these data indicate that normal intestinal and kidney epithelium are resistant to malignant transformation by an endogenous K-ras oncogene. However, activation of K-ras(V12) after Apc loss results in increased tumorigenesis with distinct kinetics. Whereas the effect of K-ras oncogenes in the intestine can been observed only after long latencies, they result in rapid carcinogenesis in the kidney epithelium. These data imply a window of opportunity for anti-K-ras therapies after tumor initiation in preventing tumor growth and invasion.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Oien, Professor Karin and Sansom, Professor Owen
• Authors: Sansom, O., Meniel, V., Wilkins, J., Cole, A., Oien, K., Marsh, V., Jamieson, T., Guerra, C., Ashton, G., Barbacid, M., and Clarke, A.
• College/School: College of Medical Veterinary and Life Sciences > School of Cancer Sciences
• Journal Name: Proceedings of the National Academy of Sciences of the United States of America
• ISSN: 0027-8424