Developmental phase-specific alkaline phosphatase isoenzymes of human placenta and their occurrence in human cancer.

Alkaline phosphatase electrophoretic patterns characteristic of three phases in early human trophoblast development are described in this preliminary communication. Phase 1 (6 to 10 weeks) consists entirely of two heat-sensitive, L-homoarginine-inhibited bands, the slower one of which possesses antigenic determinants of live-bone-type alkaline phosphatase, whereas the fast band lacks any of the known alkaline phosphatase antigenic determinants. Phase 2 pattern (11 to 13 weeks) is that of a mixture of Phase 1 and Phase 3 isozyme components, the latter exhibiting two isozyme bands with the characteristics of term placental alkaline phosphatases correspond in order to non-Regan isoenzyme, a mixture of Regan and non-Regan isoenzymes and Regan isoenzyme in a variety of human cancer tissues. The biochemical profile characteristic of trophoblast developmental Phase 1 alkaline phosphatase is expressed as 78.5% heat-sensitive inhibition (5 min at 65 degrees), 66.3% L-homoarginine inhibition, and 17.3% L-phenylalanine inhibition where n = 12. It is hypothesized that the alkaline phosphatase of human tumor tissues reflects the expression of placental genes corresponding to one or more phases of trophoblastic development.