A Human Trophoblastic Isozyme (Lactate Dehydrogenase-Z) Associated with Choriocarcinoma1

A unique electrophoretic form of lactate dehydrogenase (LDH-Z), formerly observed in a choriocarcinoma cell line (JEG 3) and first-trimester placenta, has been shown to be the same as that produced in hydatidiform mole and term placenta. We have also observed LDH-Z in second-trimester placenta, cho riocarcinoma metastasized to the liver, and five of five addi tional independently derived (from different patients) chorio carcinoma cell lines. The only exception to the production of LDH-Z in a choriocarcinomawas in the cell line BEWO, which was establishedfrom the same tumoras JEG-3. Since BEWO has been in culture for over 200 passages more than any of the independently derived lines, its lack of LDH-Z is viewed as being consistent with the loss of certain expressional charac teristics upon such long-term culture. Analysis of JEG-3 sub clones revealed the expression of LDH-Z to be independent of the products of the LDH-A genetic locus. Present data do not allow us to determine whether LDH-Z is the product of a newly discovered LDH locus or is a modified form of the product of the LDH-B locus. LDH-Z has not been observed in other human tissues, nor have we observed it in homogenates prepared from over 60 cell lines established from a wide variety of human neoplasms. We therefore conclude that LDH-Z is an isozyme associated with human choriocarcinoma and is indicative of the trophoblastic origin of the cells.