Expression of CD30 and CD30 ligand in cultured cell lines from human germ-cell tumors

Abstract

Embryonal carcinoma (EC) cells are the multipotent stem cells of human teratocarcinomas. EC cell lines isolated from human testicular teratocarcinomas retain pluripotentiality and show cell-surface marker phenotype and growth characteristics similar to those of primate embryonic stem cells. CD30, a member of the tumor necrosis factor superfamily of cytokine receptors, is expressed on the surface of human EC cells, but little is known regarding its function or the expression of its ligand in this context. Northern blot analysis, reverse transcriptase-PCR, and immunoprecipitation were used to study the expression of CD30 ligand and CD30 in cell lines representing multipotent and nullipotent EC as well as yolk sac carcinoma. Antibodies, recombinant CD30-Fc, and recombinant CD30 ligand were used in bioassays to assess the ability of exogenous CD30 ligand to promote the growth of multipotent human EC stem cells. Nullipotent and multipotent human EC cells, but not yolk sac carcinoma, expressed surface CD30, as demonstrated by immunoblotting and immunofluorescence; in multipotent cells, expression was decreased during differentiation induced by retinoic acid. Transcripts for CD30L were found at high levels in a yolk sac carcinoma cell line by Northern analysis and reverse transcriptase-PCR and were present at lower levels in EC cells as well. Immunoprecipitation confirmed expression of CD30 ligand protein in yolk sac carcinoma and in nullipotent embryonal carcinoma. Antibodies with CD30 cross-linking activity failed to promote the growth of multipotent EC cell line GCT 27 X-1. Anti-CD30 ligand antibodies and CD30-Fc both failed to block the promotion of EC cell growth induced by yolk-sac cell culture supernatants or feeder-cell monolayers. CD30 ligand is expressed in cell lines representative of human yolk sac carcinoma and nullipotent embryonal carcinoma. The membrane-bound cytokine may have an autocrine role in human EC stem-cell renewal, but other exogenous factors are required to maintain the growth of multipotent EC cells in vitro.