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Studies on the Mechanism of Inhibition of Tumor Growth by the Enzyme Glutaminase¹

Department of Biochemistry and the Cancer Research Institute, University of California, School of Medicine, San Francisco, California

The Gardner 6C3HED lymphosarcoma, Leukemia L-1210, and Leukemia L-1210/aza in ascites form were inhibited in in vivo experiments by a highly purified preparation of glutaminase-asparaginase from a pseudomonad. The glutamine content of tumors was measured by an enzymatic micromethod. The results showed that glutaminase-treated tumors were depleted of free glutamine. The glutamine-synthetase activity in tissues of normal mice has been compared with that of tumor cells. Tumor tissues showed lower activity of this enzyme than did normal tissues. Glycine-¹⁴C and adenine-¹⁴C incorporation studies in vivo indicated the impairment of both the de novo and the reutilization pathways of purine synthesis. Combination therapy with azaserine-enzyme and 8-azaguanine-enzyme produced an augmentation of tumor inhibition.

¹ Aided by research grants from the National Cancer Institute (CA-02915, CA-03175) and the Cancer Research Funds of the University of California.

² Prepared from a thesis submitted in partial satisfaction for the Ph.D. degree by F. A. El-Asmar to the Graduate Division (San Francisco) of the University of California, January, 1965.

Received 4/ 6/65. Revised 7/16/65.

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