Pentoxifylline During Steroid Window At Induction To Remission Increases Apoptosis In Childhood Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia (ALL) is the most common cancer diagnostic in children, and it represents the second death cause in this population. Despite advances in the treatment of childhood ALL, there are small portion of patients whom still succumb to this disease.

A reduced apoptosis in cells plays an important role in carcinogenesis. This phenomenon is an important component in the cytotoxicity induced by anticancer drugs. A currently challenge is the chemotherapy resistance of tumor cells, inhibiting the apoptosis induced by chemotherapy.

Pentoxifylline, (PTX) has been studied for its role on increase of apoptosis on cancer cells by different pathways. Our group has reported its efficacy in vitro and ex vivo in increasing apoptosis induced by chemotherapy drugs such as adriamycin and cisplatin in fresh leukemic human cells, lymphoma murine models and cervical cancer cells. We conducted a phase 1 controlled randomized trial to evaluate the efficacy of adding PTX to the steroid window during the remission induction phase in new diagnosed children with ALL.

We included all children from both sexes from 9 months to 17 years old during October 2011 to December 2012. Patients were divided into 3 groups, the first one as a non-malignant control group (NL group) included children with a non-hematology disease in which bone marrow aspiration (BMA) was mandatory in order to reach the diagnosis. The second one, the ALL control group whom received prednisone (PRD group) for the steroid window at 40mg/m2/day PO from day -7 to day 0; and then the third one (PTX group), the study group which included children receiving the steroid phase with PRD as early described, plus PTX at 10mg/kg/day IV divided in 3 doses, at the same days as recommended in our treatment protocol (Total Therapy XV). For all 3 groups a BMA was performed at diagnosis, for PRD group as well as PTX group, a second BMA was also collected at day 0. Apoptosis was evaluated by means of Annexin V Apoptosis Detection Kit FITC/PI (eBioscience¨, San Diego, CA, USA) in 1×10⁶ bone marrow mononuclear cells. We measured minimal residual disease (MRD) by flow cytometry at day 14 to demonstrate complete remission in leukemic patients. Statically analysis was performed by U Man Whitney.

We enrolled 32 patients: 10 in NL group; 11 in PRD group; and 11 in PTX group. The median age of all groups was 6 years (range 9 months-17 years). In PRD group, patient 1 abandoned treatment after administration of day 0, nevertheless the second BMA sample was collected. Patient number 7 died at day 4 due to complications from tumor lysis syndrome. Consequently, in these patients we were not able to measure MRD and BM aspiration at day 14. Except one patient in PRD group, all achieved complete remission at day 14. We did not find any significant difference between NL group and PRD and PTX groups before intervention (U=32 p=0.7; U=28.5 p=0.48 respectively). There was no significant difference between treatment groups before intervention (U= 37 p=0.79). However, after treatment we found an important difference between PRD and PTX groups, we observed an increase in apoptosis in PTX group in comparison with PRD group (U=17.5 p=0.04). There were no adverse effects during treatment.

The present study is the first one that shows the efficacy of PTX in increasing apoptosis induced by PRD in new ALL diagnosed children, whom have not received any treatment yet. This might be helpful, not only in patients with relapse, but to increase the overall cure rate in ALL. Further studies are needed to prove this hypothesis. With this objective, our study group is already planning a second trial were PTX will be given during all remission induction phase. Experimental reports strongly suggest that PTX induces inhibition of the transcription factor NF-ĸB, by inhibiting survival gens and facilitating apoptosis. To prove it, we are currently processing these patients' samples to know their genetic expression.

No relevant conflicts of interest to declare.