The Demonstration of Inhibitory Substances in the Filtrate of the Rous Chicken Sarcoma and Their Separation from the Active Agent

Very little is known concerning the nature of the filtrable agents causing sarcoma in chickens, though considerable information dealing with their resistance to physical and chemical agents is now available. Most of the work reported has been done with the Rous chicken sarcoma, for this apparently offers the best means for biological and chemical studies of the nature of the substance which produces tumors in fowls. Studies upon the adsorption of the agent by aluminum hydroxide and other substances have been described by Lewis and Andervont (1), while the liberation of the adsorbed tumor-producing agent by a secondary phosphate has been reported by Frankel (2), and more recently by Murphy and his associates (3). In attempting to concentrate and purify the tumor-producing agent by means of various adsorbents, our attention was drawn to the fact that a shift of hydrogen-ion concentration of the filtrate to the acid range sufficed to bring about an inactivation of the agent, with subsequent re-activation upon adjustment to an alkaline reaction. In 1928, Murphy (4) reported that the active agent may be precipitated “by lowering the isoelectric point of the concentrate with weak acid,” though he gave no details. Since the isoelectric point of a substance cannot be changed without altering the substance itself, it is assumed he meant that the precipitation was brought about by increasing the hydrogen-ion concentration. Recently he has reported that the pH at which the precipitate comes down is between 4.4 and 4.8.