Pentoxifylline is a xanthine that possesses antitumor properties and that can induce higher apoptosis in the leukemic cells of pediatric patients with acute lymphoblastic leukemia (ALL) during treatment with prednisone. We conducted a phase 1 pilot, controlled, randomized trial to evaluate the gene expression modified by pentoxifylline during the steroid window of induction to remission phase in patients newly diagnosed with ALL. Experimental and control treatments induced broad changes in the gene expression profile. Patients who received just prednisone upregulated 377 and downregulated 344 genes, in contrast with patients treated with the experimental treatment (combination of prednisone and pentoxifylline), who demonstrated upregulation of 1319 and downregulation of 1594 genes. The most important genes modified in this pathway are those with proapoptotic activity, the majority of these overexpressed. Thus, the addition of pentoxifylline to the treatment with prednisone during steroid window in patients with ALL modified the gene expression profile and changed different signal pathways of the leukemic cell. The combination of both drugs represents a therapeutic alternative for potentiating antileukemic therapy.