THE UNITARIAN OR TROPHOBLASTIC THESIS OF CANCER by Ernst T. Krebs, Jr., Ernst T. Krebs, Sr., and Howard H. Beard

If the trophoblast cell, then, is instrinsically malignant, this malignancy should become especially apparent when the trophoblast is removed from the normal extrinsic checks and controls surrounding it in its normal canalization of pregnancy. Maximov is among those who have observed normal pregnancy trophoblast in tissue culture pari passu non-trophoblast.34 He describes as follows a tissue culture preparation of a normal rabbit embryo plus the contiguous trophoblast: "From the very first moment of their formation in vitro, the trophoblastic elements, whose function under normal conditions is to destroy, resorb, and penetrate into the uterine mucosa, attack the growing embryonic tissues. They glide between cells through the intercellular spaces, along blood vessels, gnaw large holes in epithelial sheets....Wherever they appear they dissolve, destroy and resorb everything surrounding them. The picture sometimes bears a striking resemblance to chorionepithelioma malignum. As in vitro there is no maternal tissue, the destructive tendencies of the trophoblast are directed toward the net and only available---the embryonic tissue itself. This is rapidly destroyed and totally used up for the nutrition and growth of the trophoblast."
   Maximov's description of the nutritive utilization by the trophoblast of somatic or embryonic tissue in vitro bears a striking parallelism to the following observation of Greenstein on the nutritive behavior of the cancer cell: "It is, indeed, astonishing that a tumor can thus attach itself to an organism already running downhill in negative nitrogen balance and subsequently grow at the host's further expense."