Effect of over-expression of ZIP1-Myc on RWPE2 cell growth. Vector or ZIP1-Myc expressing (Clone A and Clone B) RWPE2 were plated at a density of 20,000 per well in 12-well plates for 24 hours and then 0 or 25 μM ZnSO4 was added into the medium. Medium was changed at days 3, 6 and 9 after plating. Cells were harvested and cell numbers were determined at days 6, 9, and 12 after plating. Values are the means ± SD of three experiments.