Centrioles, primary cilia and calcium in the growth of Balb/c 3T3 cells.

In every mammalian cell the interphase centriole forms a primary cilium during some part of the cell cycle. Many sensory receptors are modifications of primary cilia, but a sensory role for primary cilia in mammalian cells has not been proven. Nevertheless, we have found that both growth factors and calcium ionophore (A23187) induce calcium fluxes and shortening of the primary cilium. This evidence raises the question of whether the primary cilium is involved in calcium fluxes that are necessary for growth stimulation in mammalian cells.

Stimulation of synthesis and secretion of chorionic gonadotropin subunits by eutopic and ectopic hormone-producing human cell lines.

The effects of dibutyryl cyclic adenosine 3'3':-5'-monophosphate (AMP) and sodium butyrate on the synthesis and secretion of human chorionic gonadotropin (HCG) by trophoblastic and nontrophoblastic human cell lines were studied by radioimmunoassay and pulse-chase labeling techniques. Dibutyryl cyclic AMP stimulated synthesis and secretion of HCG-alpha and HCG-beta subunits by the trophoblastic cell lines JAR and BeWo, whereas butyrate had no effect or decreased secretion. On the other hand, a number of nontrophoblastic cell lines (including the breast carcinoma lines ZR-75-31, BT-20, and MCF-7; the bronchogenic carcinoma line ChaGo; and the cervical carcinoma line HeLa S3) were induced to synthesize and secrete increased amounts of HCG subunits by butyrate, but dibutyryl cyclic AMP had less or no stimulatory effect. The nontrophoblastic brain tumor line CBT was an exception to this general rule in that HCG-beta production was stimulated by dibutyryl cyclic AMP but not by butyrate. In all cases, the drug-induced increase in HCG subunit secretion was directly proportional to the elevation of HCG subunit synthesis. These data suggest that the differential effects of dibutyryl cyclic AMP and butyrate on trophoblastic and nontrophoblastic cells reflect differences in the transcription or translation of HCG subunit genes induced by these agents in the two cell types.

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.