The behavior of transplanted mixtures of tumor and embryo

Mixtures of hashed mouse-embryo and transplantable mouse-tumor were inoculated into the subcutaneous tissue of adult animals. It was found that growth of both elements took place, often in intimate association. But to obtain these results a balancing of avidity was necessary, such as Apolant used in his mixtures of sarcoma and carcinoma. Only tumor-cells of sluggish character can be implanted with the embryonic cells, which otherwise are outgrown and soon die. This is interesting in view of the enormous proliferative ability of the embryonic cells in utero, and it would seem to show that such ability depends at least as much on the excellent nutritive arrangement in utero as on inherent cell-energy. The transplanted cells not only lack the power of unlimited growth that characterizes tumor, but during their temporary growth in a new environment lack the proliferative energy that many tumors show.

In a mixed graft that has only partially succeeded, tumor and embryo tend to grow or fail together. This must be largely a matter of immediate nutritive conditions, which are best, for example, at the edge of the graft. But it is also notable that at those points where one element has elicited a supporting reaction from the host tissues and is growing, the other has also succeeded. When the tumor mass is walled off from the host by a layer of developing embryo, it nevertheless grows, utilizing as stroma the embryonic connective tissue.