Abstract

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 liver-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 phosphatase. These three patterns of developmental phase-specific placental alkaline phosphatases correspond in order to non-Regan isoenzyme, a mixture of Regan and non-Regan isozymes 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°), 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. 1 Supported in part by Grants CA-13332 and CA-12924 from the National Cancer Institute, NIH, USPHS, Bethesda, Md. The support of the Council for Tobacco Research (Grant 935-M) is acknowledged. This paper was presented at the 66th Annual Meeting of the American Association for Cancer Research in San Diego, Calif., May 8 to 11, 1975 (6). 3 Recipient of Cancer Research Award K6-18453 of the National Cancer Institute. Part of this study was carried out at the University of California at Los Angeles during the tenure of a Visiting Professorship of Pathology in the Department of Pathology.