Multipotentiality of Single Embryonal Carcinoma Cells.

In order to test the hypothesis that embryonal carcinoma cells are multipotential stem cells of a teratocarcinoma, an in vivo cloning technic was designed. Small embryoid bodies containing mostly embryonal carcinoma were obtained from ascitic con version of a murine teratocarcinoma and were dissociated with trypsin to form a sus pension of single cells; the single cells were picked up in small capillary tubes and transplanted directly into mice. From over 1700 single cell grafts, 44 clonal lines were obtained; 43 of these lines were teratocarcinomas composed of as many as fourteen well differentiated somatic tissues in addition to embryonal carcinoma. These 43 lines varied in their degree of differ entiation, capacity to produce embryoid bodies, and in growth rate. The remaining clonal line showed limited potential for differentiation, producing only yolk sac, trophoblast, and embryonal carcinoma. The results demonstrated the multipotentiality of single embryonal carcinoma cells, as well as the heterogeneity of the embryonal carcinoma of a teratocarcinoma. The capacity of single embryonal carcinoma cells to differentiate into benign tissues sup ports neither the dogma of the irreversibility of the malignant transformation nor the somatic cell mutation theory of cancer. These findings were interpreted as giving strong support to the stem cell theory of cancer.