GENISTEIN INDUCES A G(2) M BLOCK AND APOPTOSIS IN HUMAN UTERINE ADENOCARCINOMA CELL-LINES/

We report evidence indicating that the isoflavone genistein induces a dose-dependent antiproliferative effect in the human uterine adenocarc inoma cell lines HEC-1A, HEC-1B, AN3 CA and RL95-2. Cell growth inhibi tion resulted from a partial G(2)/M block and from the appearance of a hypodiploid DNA peak (reduction in nuclear DNA content), suggestive o f apoptosis. In HEC-1A cells, we found that both cell cycle impairment and the appearance of a hypodiploid DNA peak were time-dependent, tri ggered by similar concentrations of the isoflavone and not affected by the presence of serum in the culture medium. However, while the genis tein-induced cell cycle arrest was fully reversible, the appearance of the hypodiploid DNA peak was not. To verify whether the appearance of a hypodiploid DNA peak corresponded to apoptosis, we used in situ end labelling (ISEL) and transmission electron microscopy (TEM) in HEC-1A cells. We found that a 48-h treatment with genistein induced ISEL pos itivity only in a minority of cells, while at 72 h the majority of cel ls were labelled. At this time TEM showed the typical ultrastructural features of apoptosis, including apoptotic bodies.Because genistein in hibited tyrosine kinase (TK) and topoisomerase (Topo) II activity in H EC-1A cells and its effects were mimicked by structurally unrelated TK and Topo II inhibitors, we speculate that interactions with TK and To po II are relevant for the antiproliferative effect of genistein. Conv ersely, the antiproliferative effect of genistein seems to be independ ent of its oestrogenic activity. Our data indicate that genistein inhi bits the growth of uterine adenocarcinoma cell lines by inducing cell cycle arrest and apoptosis.