ABSTRACT
Recent studies have suggested that cellular transformation by abl oncoproteins may be mediated by the ras signaling pathway. One of the main nuclear targets of this signal transduction cascade is the Fos and Jun family of transcription factors. To test the relevance of the c-fos proto-oncogene for v-abl-induced cancer development, we inoculated c-fos-deficient mice with the Abelson murine leukemia virus. Neonatal c-fos-deficient mice infected with the Abelson complex are able to develop the pre-B-cell lymphoma that characterizes Abelson disease. c-fos-deficient animals succumb to the disease with similar kinetics as their wild-type and heterozygous littermates. Moreover, the transformed cell that brings about the malignancy in mutant mice is the same pre-B-cell lymphoblast that is seen in control animals. These results demonstrate that c-fos is not required for in vivo transformation by v-abl.
Subject(s)
Cell Transformation, Viral , Genes, abl , Genes, fos , Lymphoma, B-Cell/etiology , Transcription Factor AP-1/physiology , Abelson murine leukemia virus , Animals , Animals, Newborn , Lymphoma, B-Cell/genetics , Lymphoma, B-Cell/microbiology , Mice , Mice, Knockout , Survival AnalysisABSTRACT
The proto-oncogene c-fos is a major nuclear target for signal transduction pathways involved in the regulation of cell growth, differentiation, and transformation. Using the multistep skin carcinogenesis model, we have directly tested the ability of c-fos-deficient mice to develop cancer. Upon treatment with a tumor promoter, c-fos knockout mice carrying a v-H-ras transgene were able to develop benign tumors with similar kinetics and relative incidence as wild-type animals. However, c-fos-deficient papillomas quickly became very dry and hyperkeratinized, taking on an elongated, horny appearance. While wild-type papillomas eventually progressed into malignant tumors, c-fos-deficient tumors failed to undergo malignant conversion. Experiments in which v-H-ras-expressing keratinocytes were grafted onto nude mice suggest that c-fos-deficient cells have an intrinsic defect that hinders tumorigenesis. These results demonstrate that a member of the AP-1 family of transcription factors is required for the development of a malignant tumor.
