Approximately 90 per cent of 101 human tumors implanted in cortisone-treated x-radiated rats survived and proliferated for 12–20 days. In some instances they were maintained as long as 30 days. A similar percentage of tumors implanted in cortisone-treated nonirradiated rats were also positive for growth. None survived in normal control animals.

One biopsy specimen of a human epidermoid carcinoma, implanted originally in a single cortisone-treated rat, has so increased in the fourth transfer generation that tumors are being carried by ten rats and 38 hamsters, all cortisone-treated. It is hoped that this neoplasm can be maintained permanently as a transplantable tumor in laboratory animals.

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This investigation has been aided by grants from the Jane Coffin Childs Memorial Fund for Medical Research, the National Cancer Institute of the U.S. Public Health Service, American Cancer Society, and the Damon Runyan Memorial Fund for Cancer Research.

The cortisone acetate (Cortone, Merck) used for these experiments has been supplied through the courtesy of Merck & Co., Inc., Rahway, N.J.

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