Purine re-utilization in normal and malignant cells of human placental origin

The metabolism of the purine compounds adenine, hypoxanthine and adenosine, was studied in cultured human choriocarcinoma cells (BeWo) and in term human placental cells in primary culture. Both preparations retained at least some specific placental functions, as shown by secretion of human chorionic gonadotrophin, which was less in the malignant cell line than in the primary culture. In contrast, choriocarcinoma cells incorporated substantially more purine bases (adenine and hypoxanthine) and nucleoside (adenosine) into nucleotides, mainly ATP. Adenosine metabolism was concentration-dependent, with a higher proportion metabolized to hypoxanthine at higher substrate concentration. The term placental cells, which do not divide in culture, have a less active purine metabolism, but they retain a degree of specialized function higher than that of malignant cells of placental origin.