Three different activated ras genes in mouse tumours; evidence for oncogene activation during progression of a mouse lymphoma.

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Abstract
Five unrelated mouse tumours have been shown to carry activated transforming genes using the NIH/3T3 transfection assay. Three of these tumours, a T‐cell lymphoma, a fibrosarcoma and a macrophage tumour, were found to carry an activated c‐Ki‐ras gene. A c‐Ha‐ras gene was shown to be activated in a myeloid leukaemia and a recently identified member of the ‘ras’ gene family, N‐ras, was found to be activated in a lung carcinoma. The T‐cell lymphoma, L5178Y‐ES, is a more aggressively growing metastatic variant which arose spontaneously from the parental tumour, L5178Y‐E. Although DNA from both parental and variant tumours was shown to transfer a genetic marker to recipient cells equally well, only the metastatic variant carried an activated c‐Ki‐ras gene detectable by transfection. The altered growth behaviour of the L5178Y‐ES cells may therefore be the result of the spontaneous activation of the c‐Ki‐ras gene after the lymphoma cells had already become tumorigenic.