High frequency of mas oncogene activation detected in the NIH3T3 tumorigenicity assay.

In four independent transfection experiments performed with high molecular weight DNA isolated from a human ovarian carcinoma, oncogenic NIH3T3 cells contained an activated mas gene in the in vivo tumorigenicity assay. Varying from 1.8 to 3.5 kb upstream of the coding region of the mas gene, the DNA sequences in the transfectants diverged from those present in the ovarian tumor, as determined by restriction enzyme mapping. Because these upstream sequences were different in at least 5 nude mouse tumors studied, we suppose that another as yet not identified structural alteration in the mas gene of the original ovarian tumor is responsible for the transforming activity of the gene.