Production of human chorionic gonadotropin and its subunits by human tumors growing in nude mice

The production and secretion of human chorionic gonadotropin (HCG) and its subunits by human tumors growing in nude mice have been examined. JAR choriocarcinoma cells growing in nude mice produce both free alpha subunit and complete HCG, but there is a decrease in the amount of free alpha subunit relative to complete HCG produced in vivo compared to HCG subunit production by these cells growing in culture. Cell lines that produce only free alpha subunit in culture (HeLa cervical carcinoma, ChaGo bronchogenic carcinoma, and BT-20 breast carcinoma) continue to produce primarily free alpha subunit in vivo, but a small amount of HCG-beta/HCG is detectable in the 24-hr urine collected from mice bearing HeLa or ChaGo tumors. CBT cells derived from a glioblastoma multiforme produce both alpha and HCG-beta/HCG in vivo. This represents a distinct shift from the pattern of HCG subunit production by CBT cells in culture because cultured CBT cells produce only free beta subunit and do not synthesize either free alpha or complete HCG. Thus, for human tumors growing in nude mice, there appears to be a shift toward more complete HCG production and a decrease in free subunit production as compared to the pattern observed for cultured cells.