Cell-cycle arrest in G0/G1 phase of growth factor-induced endothelial cell proliferation by various calcium channel blockers.

Calcium channel blockers cause antiproliferative effects on various cells in culture. Since angioneogenesis is a crucial step in the development of tumor growth, we examined the influence of different calcium channel blockers on human umbilical arterial endothelial cell (HUAEC) growth. Cell growth was measured by cell count, by [3H]thymidine incorporation, and by a 5-bromo-2-deoxyuridine (BrdU-incorporation immunofluorescence assay. Cell-cycle analysis was performed by flow cytometric analysis. Nifedipine, isradipine, diltiazem, and verapamil dose-dependently inhibited the basic fibroblast growth factor (bFGF)-induced [3H]thymidine incorporation. Fifty micromolars of nifedipine, isradipine, diltiazem, and verapamil completely inhibited bFGF-induced proliferation of HUAEC. Ten micromolars of each calcium channel blocker abolished the bFGF-induced increase in cell count. Five micromolars of isradipine completely blocked the bFGF-induced BrdU incorporation. Stimulation of HUAEC with bFGF (50 ng/ml) for 24 h caused a 2-fold increase in cells that entered S and G2+M phase in comparison with control cells. Five micromolars of isradipine abolished this effect completely. We conclude that calcium channel blockers are able to inhibit cell proliferation by a cell-cycle arrest in G0/G1 phase.