Effect of syndecan-1 on cell cycle progression and cyclin D1 expression. (A) Expression of syndecan-1 inhibits G1-S progression: DNA content of exponentially growing ARH-77 cells, transfected with vector only (ARH-77^neo) or syndecan-1 (ARH-77^syn-1), was determined by flow cytometry after PI staining. (B) Shed syndecan-1 inhibits G1-S progression: ARH-77 cells were incubated with syndecan-1 (2 nmol/L) or media alone for 48 hours and stained with PI. DNA content analysis was performed using flow cytometry. (C) Shed syndecan-1 inhibits cyclin D1 expression. ARH-77 cells were incubated with syndecan-1 (2 nmol/L) or media alone for 48 hours and stained for cyclin D1 using FITC-conjugated anti-cyclin D1 antibody using the manufacturer's protocol (PharMingen). Expression of cyclin D1 is expressed as the ratio of median fluorescent intensity of test sample to that of isotype control (*P < .05).