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The Mammary Tumor Agent in Extracts of Frozen and Unfrozen Mammary Cancers^*

John J. Bittner and David T. Imagawa

( Division of Cancer Biology, Department of Physiology, and the Department of Bacteriology and Immunology University of Minnesota Medical School, Minneapolis 14, Minn.)

No difference was observed in the tumor-producing activity of the mammary tumor agent in cell-free supernatants of frozen and unfrozen transplanted mammary carcinoma, when tumors of the same passage were used as the source material.

There was no decrease in the activity of the agent derived from fresh tissue after the tumor had been transplanted for nine passages.

When extracts of frozen tumors of the first passage were used, no variation was seen either in the incidence of mammary cancer or the average cancer age in mice injected intraperitoneally or subcutaneously. The first tumor appeared at 193 days.

Tumors appeared at the injection site of the thawed tumor mince. Extracts of these tumors, and their transplants, gave fewer tumors in the test animals when injected subcutaneously than intraperitoneally.

From these studies, no evidence was obtained to suggest that the mammary tumor agent is activated by freezing.

^* Assisted by grants from the National Cancer Institute of the National Institutes of Health, U.S. Public Health Service, and the American Cancer Society upon recommendation of the Committee on Growth of the National Research Council.

Present address: Department of Pediatrics, University of California School of Medicine, Los Angeles 24, Calif.

Received 2/27/53.