Peg-Arg I plus Ara-C impairs malignant T-cell proliferation and induces tumor cell apoptosis in vivo. (A-B) Proliferation of T-ALL cells was tested in vivo in CCRF-CEM-bearing mice treated with peg-Arg I/Ara-C (n = 10) or PBS (n = 10) by measuring the uptake of BrdU, as described in “Cell-cycle progression and proliferation.” (C) A representative experiment showing the expression of cyclin D3 and GAPDH in CD5⁺ cells sorted from individual tumor-bearing mice treated with PBS (n = 3) or peg-Arg I plus Ara-C (n = 5). The experiment was repeated a minimum of 3 times obtaining similar results. (D) Annexin V expression was established in gated CD5⁺ cells in the spleens from tumor-bearing mice treated with peg-Arg I/Ara-C (n = 10) or PBS (n = 10) after 30 days of tumor injection.