Immunology and biochemistry of the Regan isoenzyme

The Regan isoenzyme is a placental-type alkaline phosphatase that is expressed in a number of human tumors, particularly in gonadal and urologic cancers. Attention is given to the unique gene that codes for placental alkaline phosphatase and the similarities and differences in the tumor and placental gene products. The separation and identification of individual organ-specific isoenzymes is accomplished by a variety of biochemical, immunologic, and electrophoretic techniques and the correlation of the Regan isoenzyme, non-Regan isoenzyme, and Nagao isoenzyme, and the Kasahara isoenzyme is made with their developmental counterparts. The L-leucine-sensitivity phenotypes of placental and tumor alkaline phosphatases and the non-Regan early placental type alkaline phosphatases appear to be developmental phase-specific. Oncotrophoblast gene expression has been investigated with monophenotypic cell culture lines as a consequence of modulation by prednisolone and hyperosmolarity. Finally, general discussion of oncodevelopmental proteins as tumor markers precedes a current opinion of Regan isoenzyme as a tumor marker. Evidence now points to seminoma as a consistent producer of Regan isoenzyme although much more work will be required to establish its clinical utility.