Ras p21 onco-protein in the sera of mice carrying an experimentally induced tumor and in human cancer patients.

We have established a model system to detect the presence of ras p21 in the sera of Balb/c mice carrying tumors induced by a mouse cell line transformed with the Harvey murine sarcoma virus in the presence of a helper Friend murine leukemia virus. As determined by ELISA and immunoblot assays, ras p21 in the serum increased with increased tumor growth. Since ras genes have been found to be frequently activated in human tumours, we examined the levels of ras p21 in the sera of a variety of human cancer patients. In only 3 out of 13 cases, representing patients with adenocarcinomas of the stomach receiving chemotherapy, was ras p21 detected at elevated levels, whereas in patients with the following types of cancer no substantial change in serum ras p21 was observed; nine with breast, 5 colon, 5 lung, 5 ovarian and 5 hepatocellular carcinomas.