Tumor homograft-enhancing activity was found to be widely distributed in subcellular particulate fractions prepared from Sarcoma I ascites cells but was essentially absent from the soluble fraction. It was most concentrated in the fluffy layer, but, because of the relatively large mass of the nuclei, about half of the total activity of the cells was present in the nuclear fraction.

A procedure for extracting enhancing activity from a particulate fraction prepared from ascites tumor cells was developed. Active extracts contained three components separable by electrophoresis at pH 9.2. The fastest-moving component could be eliminated by incubating the particulate fraction with ribonuclease.


Supported by a grant from the American Cancer Society (E-26) and by research grant C-1329 from the National Cancer Institute of the National Institutes of Health, U.S. Public Health Service.

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