Growth inhibition by ATRA or Vit D3 in antisense RB-transfected U-937 cells as compared with mock-transfected cells. Cells (0.2 × 10⁶ /mL) from antisense RB clone A1 and mock clone M6 were incubated with Vit D3 at 0.1 μmol/L or ATRA at 1 μmol/L for 4 days. Aliquots were removed and counted daily. Simultaneously, noninduced cells were incubated as controls. Results shown are from one representative experiment. (□) M6; (▵) M6 + ATRA; (○) M6 + Vit D3; (▪) A1; (▴) A1 + ATRA; (•) A1 + Vit D3.