Alterations of Cell Signaling Pathways in Pediatric B-ALL Patients.

The outcome for children with Acute Lymphoblastic Leukemia (ALL) has improved in the last few decades with current therapy resulting in an event free survival exceeding 75%. Despite of this, 25% of patients still relapse or resist to conventional therapies. Proteomics, in particular the Reverse Phase Protein Arrays (RPA), offers a new approach to study both the potential molecular mechanisms of drugs chemosensitivity versus resistance, and identify new drug targets in the patients that do not respond to therapy. RPA, which can quantitatively measure dozens to hundreds of phosphorylated kinase substrates from only a few thousand cells, can be used to profile the working state of cellular signaling pathways in a manner not possible with gene microarrays, since post-translational modifications cannot be accurately portrayed by global gene expression patterns alone. We employed RPA to study the phosphorylated cellular pathways in bone marrow aspirate samples collected prior to treatment. The phosphorylation status of 95 key signaling proteins, including pro-survival, pro-apoptotic and those involved in cell cycle control were analyzed from 120 pediatric B-ALL specimens collected at the Pediatric Oncohematology Laboratory (University of Padova) over the past 15 years. Molecular network analysis and phosphoprotein profiling were performed using commercially available software. Our results indicate that there may be a difference between the molecular networks of activated kinase substrates within leukemic patients depending on disease state, genotype, or response therapy. The discovery of the molecular mechanisms related to drug resistance could play an important role for individualizing therapy and may reveal new strategies to improve treatment outcome.