Alkaline Phosphatase Activity in Mouse Teratoma

In tumors and embryoid bodies of mouse teratoma a correlation has been established between specific activity of alkaline phosphatase (EC 3.1.3.1) and content of embryonal carcinoma, the stem cell of the tumor. A histochemical study of embryoid bodies has shown that high levels of the enzyme are confined to embryonal carcinoma. Fifteen tissue culture lines could be classified into three groups: (a) lines identifiable as pluripotential embryonal carcinoma by their morphology, tumorigenicity, and capacity to differentiate in vivo; (b) nullipotential embryonal carcinoma, resembling pluripotential embryonal carcinoma in morphology and malignancy but giving rise to undifferentiated tumors; and (c) lines of apparently nonmalignant somatic cells. Both types of embryonal carcinoma possess levels of alkaline phosphatase 5- to a 100-fold higher than the somatic cell lines. The embryonal carcinoma enzyme resembles the enzymes from kidney and placenta in kinetics of thermal inactivation and sensitivity to the inhibitor L-phenylalanine, but is distinguishable from the alkaline phosphatases of liver and intestine. These findings are discussed in relation to the use of teratoma for the study of cell differentiation.