The introduction of new assays for point mutations in chromosomal DNA has enabled us to identify activated ras genes in a large number of human tumors (Table I; ref.1). Thus it became clear that certain tumor types never or only occasionally harbor a mutated ras gene, whereas other tumor types have an activated ras gene more or less frequently (20% to 90% of the cases). On the basis of clinical or histopathological features, a tumor that has a mutated ras gene does not differ from a tumor of the same type that does not. This indicates that the activation of ras is not an essential event. However, since activated ras proteins have cell-transforming properties, and (nearly) all malignant cells of a tumor carry a mutated gene, it is likely that the activation of ras does contribute to the development of tumors. Apparently, other genetic events have similar effects as ras activation.
KeywordsAcute Myeloid Leukemia Chronic Myeloid Leukemia Mutational Activation Mutagenic Agent Acute Lymphoid Leukemia
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