Fate of the Active Agent in the Chicken Sarcoma in Mixtures Containing Inhibiting Substances.

Abstract

We have previously described 1 the presence of a tumor inhibiting substance in the filtrate of the Rous chicken sarcoma and in normal chicken sera. It was found that this inhibiting substance is retained in the supernatant fluid when the tumor filtrate is brought to pH 4, while the active agent is carried down in the precipitate. In a more recent report, Murphy 2 and his associates report results that would seem to confirm these observations.

The fact that the activity of the agent can be inhibited by the supernatant fluid and sera made it of interest to ascertain whether the agent was actually destroyed in such mixtures or whether its tumor producing properties were merely inactivated. In order to answer this question it became necessary to determine if it is possible to recover the agent in an active state from these non-infective mixtures. The supernatant fluid used was prepared by adding an equal amount of a phthalate buffer solution at pH 4 to a 20% filtrate of the Rous chicken sarcoma. After standing for 30 minutes, the mixture was centrifuged, and the supernatant fluid decanted, neutralized and concentrated in vacuo to 1/2 its original volume. To 2 cc. of the concentrated supernatant fluid was added 0.5 cc. of filtrate, and the mixture allowed to stand for 30 minutes at room temperature. Such a mixture when injected into chickens fails to produce tumors in 75% of the inoculations. If, however, the mixture is brought to pH 4, and the precipitate extracted at pH 8, the active agent is recovered, for the extract is now able to induce tumor growth. Similar results were obtained when blood was used instead of the supernatant fluid.