Yolk Sac Cultivation of Tumors

Some months ago there was published from this laboratory a brief preliminary report of a method whereby tumors could be cultivated in the yolk sacs of developing chick embryos (4). Neoplasms were first injected into the yolk sac with the idea that the tumor cells would die and disintegrate, thus releasing any virus that might be present. It was hoped that if such a release occurred the medium possibly might favor the growth and concentration of the tumorproducing principle, as Cox and others have found for the viruses of Rocky Mountain spotted fever and typhus groups (1). Since publication of the preliminary results, this technic has been used here extensively in studies involving large numbers of eggs, and it is now felt that a further and more detailed description of the method would be of value. Special interest has been focused on the use of this medium for growing tumors because it was found possible to produce malignant neoplasms in mice with cell-free extracts of the yolk material from eggs implanted with cancer (3). The technic was hit upon in the course of investigations leading up to the discovery of this virus-like principle. It occasioned considerable surprise when eggs so treated were opened and well developed tumors were discovered in the yolk sacs. The principles involved are essentially the same as those discovered by Murphy when he found that the chick chorioallantoic membrane and the chick itself were capable of supporting the growth of tumor tissue from the mouse and the rat (2). In the present instance the location of the growth is different, but in both methods the chick supports the cancer. In the yolk sac method the tumor does not interfere with the chick and inoculation is relatively simple.