GENISTEIN, A TYROSINE KINASE INHIBITOR, BLOCKS THE CELL-CYCLE PROGRESSION BUT NOT CA2+ INFLUX INDUCED BY BAY K8644 IN FRTL-5 CELLS

IGF-I, when added to TSH-primed FRTL-5 cells, induces a long lasting Ca2+ influx and then DNA synthesis. Ca2+ channel agonist, BAYK 8644, is capable to mimic these effects on cell proliferation. We studied the effect of genistein, a specific tyrosine kinase inhibitor, on BAY 1(8644- or IGF-I- induced cell cycle progression in FRTL-5 cells. Genitein inhibited DNA synthesis induced by BAY K8644 and by IGF-I. In contrast, Ca2+ influx stimulated by BAY K8644 was not inhibited. These data demonstrate that the signal transduction pathway induced by BAY K8644 or IGF-I may possibly involve genistein-sensitive process at the downstream step of Ca2+ entry. © 1993 Academic Press, Inc.