The case in point is the relationship of chorionic alkaline phosphatase to chorionic gonadotrophin, both being local ized to syncitiotrophoblast and expressed in choriocarci

The view is advanced that it is important to fix the stage of development corresponding to the pattern of expression of oncodevelopmental proteins in neoplastic transformation and neoplasia. From a map of development focused on events beginning with the zygote and ending with the establishment of fetus and placenta, it is possible to explain why certain develop mental gene products are restricted to fetus or placenta or distributed in both. It also suggests which products can be expected to be expressed concordantly in neoplastic trans formation and in neoplasia. The case in point is the relationship of chorionic alkaline phosphatase to chorionic gonadotrophin, both being local ized to syncitiotrophoblast and expressed in choriocarci noma. Chorionic alkaline phosphatase, the neoplastic counterpart of which is non-Regan isoenzyme, is defined as the heat-sensitive, L-homoargininebut not L-phenylala nine-inhibited alkaline phosphatase that has some liver an tigenic determinants, and that has a characteristic electro phoretic pattern. This alkaline phosphatase isoenzyme dif fers markedly from term placental alkaline phosphatase, which is heat stable and L-phenylalanine sensitive, and pos sesses unique antigenic determinants. Moreover, there ex ists amnion alkaline phosphatase which is L-phenylalanine sensitive and heat labile and travels to a preliver alkaline phosphatase position on electrophoresis. The expression of term placental, chorionic, and amnionic alkaline phospha tase isoenzymes in preneoplastic and neoplastic lung and other cancers is anticipated from a preliminary study of epithelial cell sonic extracts obtained from the tracheobron chial tree of a patient with bronchogenic cancer.