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Studies on the Enzymology of the Rhabdomyosarcoma Induced by the Murine Sarcoma Virus (Moloney)¹

Viral Leukemia and Lymphoma Branch, National Cancer Institute, and Microbiological Associates, Inc., Bethesda, Maryland 20014

The murine sarcoma virus (Moloney) induces a rhabdomyosarcoma in adult mice followed by a high incidence of regressions. Changes in several biochemical parameters and enzyme levels were followed during the enlargement and regression of the tumor.

As the tumor enlarged, water, protein, RNA, and DNA concentrations increased on a dry weight basis. Actomyosinfree Mg⁺⁺-activated ATPase and lactate dehydrogenase activity decreased as the tumor enlarged. At the same time glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase showed marked increases in activity. As the tumor regressed, activity of these latter enzymes continued to increase. Significantly elevated activity remained when the tumor was undetectable by palpation. Acid phosphatase levels in the tumor were almost 3 times that found in normal muscle reflecting infiltration of phagocytic cells.

Reduced lactate dehydrogenase activity and low lactate accumulation in the tumor compared to normal muscle suggest an unusual pattern of NAD metabolism compared to other tumors. Both tumors and inoculum were found to contain high titers of lactate dehydrogenase virus. The pattern of four of the enzymes agrees favorably with the pattern found in other nonviral rhabdomyosarcomas.

¹ This investigation was supported in part by National Cancer Institute USPHS Contract PH-43-66-887 at Microbiological Associates, Inc., Bethesda, Md. Portions of this work have been presented (6).

Received 5/ 9/69. Accepted 9/22/69.