Effect of CM from transfected cells on the S-phase of normal CFU-GM. Control shows CFU-GM in S-phase (mean ± SD) with medium alone (n = 4); HL-60 CM (n = 4); RBL/Wild CM from untransfected cells (n = 2); RBL/PR3 proteinase 3 transfectant (n = 4); RBL/Cath G cathepsin G transfectant (n = 2); RBL/Elastase transfectant (n = 2); RBL/PR3/cat.del catalytically inactive PR3 transfectant (n = 3); 32D/PR3 (n = 3); 32D/Cath G (n = 2); 32D/Elastase (n = 2). The asterisk (*) denotes significant reduction of the number of CFU-GM in S-phase (P < .01).