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The Biochemical Characterization of Alkaline Phosphatase from Chemical- and Viral-induced Thymic Lymphomas of C57BL Mice¹

Department of Medical Microbiology, Stanford University, Stanford, California 94305

The alkaline phosphatase activity of a number of chemical- and viral-induced thymic lymphomas from C57BL mice was characterized biochemically according to pH optimum, heat inactivation, the ratio of activity toward two substrates, p-nitrophenyl phosphate and ß-glycerophosphate, and electrophoretic mobility in acrylamide gel. Alkaline phosphatase activity from normal liver, spleen, and duodenum was also characterized for comparison. Since this enzyme is not found in thymic lymphocytes of the normal C57BL adult mouse but is usually present in tumor cells, such a characterization of it might be expected to indicate whether the genetic information for the enzyme is of virus or cell origin. Enzyme activity from tumors induced by different chemical agents or by virus did not differ significantly with respect to the first 3 parameters tested and, in addition, resembled the enzyme from spleen in these 3 characteristics. These same characteristics determined for the alkaline phosphatase activity in the normal 16-day embryo thymus were consistent with those found in the tumor and spleen enzymes.

Disc-gel electrophoresis performed on the adult normal and tumor tissue extracts showed the major component of the tumor alkaline phosphatase activity to have an electrophoretic mobility similar to that of the normal spleen. A minor component of the tumor alkaline phosphatase activity was found to have a slower mobility than any component of the enzyme from the normal tissues tested. It is concluded that the major component of the alkaline phosphatase activity of this tumor is similar to the alkaline phosphatase activity of the spleen and may represent a cell-coded enzyme which is derepressed in the process of neoplastic transformation.

¹ This work was supported by USPHS Research Grant CA-8914 from the National Cancer Institute, by Training Grant AI-82 from the National Institute of Allergy and Infectious Diseases, and by grants to the Advanced Computer for Medical Research (ACME project) from NIH (FR-0311) and the Josiah Macy, Jr., Foundation.

² USPHS Predoctoral Fellow 5-F1-GM-34,782-02. Present address: Department of Biology, Atlanta University, Atlanta, Ga. 30314.

Received 8/11/69. Accepted 1/ 2/70.