Objective To investigate the antiproliferative effect of HMG CoA reductase inhibitor on ADPKD cyst-lining epithelial cells and its possible mechanism. Methods Cell viability was assayed by MTT. Membrane-bounded p2lras was detected by immunoblotting. The expression of c-jun and c-fos was examined by immunocytochemistry. Results After ADPKD cyst-lining epithelial cells were exposed to HMG CoA reductase inhibitor, proliferation was markedly inhibited( P