sions, for example, regarding the indication to allogeneic HSCT within T lineage ALL. Screening for deletions of the IKZF1 gene might improve risk stratification in patients with Ph positive ALL. Distinct levels of the MRD load as assessed by RQ PCR have been LY294002 PI3K inhibitor defined as guidelines for therapeutic decisions. Molecular diagnostics and immunophenotyping have become the basis for targeted therapy in ALL, as demonstrated by the use of tyrosine kinase inhibitors for BCR ABL1 positive ALL, and rituximab for CD20 positive B cell precursor ALL or mature B ALL/ Burkitt lymphoma, which improved the prognosis of these previously highly adverse subtypes. Screening for BCRABL1 mutations can be helpful to identify patients with Philadelphia positive ALL who may have a benefit from second tyrosine kinase inhibitors or novel compounds targeting the T315I.
Considering the recent introduction of highthroughput sequencing into hematological diagnostics, the potential of this novel technology should be explored for mutation screening, the definition of new therapeutic targets, TGX-221 PI3K inhibitor and follow up diagnostics in the acute lymphoblastic leukemias. Marked clinical improvement was reported when a BCR ABLkinase inhibitor, imatinib, was combined with chemotherapy for the treatment of Ph positive acute lymphoblastic leukemia.1,2 However, further improvement is needed to decrease relapses owing to residual or resistant leukemic cells. Leukemia stem cells are reported to be responsible for leukemia relapse.
3 Mathematical models of the chronic phase of chronic myeloid leukemia suggested that imatinib does not eradicate LSCs,4,5 and the survival of malignant cells is reportedly attributable to the quiescence of LSCs.6 In order to overcome drug resistance, rational combinations of molecular targeting drugs of different signal pathways have been explored.7 The mammalian target of rapamycin has attracted attention as a therapeutic target of LSCs.8,9 mTOR regulates cell growth and apoptosis through the phosphatidilinositide 3 kinase /AKT/mTOR pathway, which was reported to be constitutively activated in most AMLs10 or in T ALL cell lines.11 The inhibitory effect of an mTOR inhibitor, rapamycin, on the Pht leukemia cell lines with T315I was reported,7 and more recently, the effect of everolimus on human childhood B cell progenitor ALL was reported in a non obese diabetic/severe combined immunodeficiency model.
12 The mTOR inhibitor everolimus is an orally available mTOR inhibitor which was approved by the Food and Drug Administration for advanced renal cell carcinoma. A phase I/II study has been performed in patients with acute leukemia,13 and clinical trials alone or in combination with other drugs are also currently ongoing for lymphoma and myeloma.14 Effects of everolimus on human Pht ALL have not been well examined. In this study, we examined the efficacy of everolimus in combination with imatinib utilizing Pht ALL cell lines and an NOD/SCID/IL2rgnull mouse model of human BCR ABLt leukemia,15 in which the hierarchy of leukemia cells was maintained. Materials and methods Leukemic cells Xenografts were established in NOD/SCID/IL2rgnull mice as previously described.15 Briefly, Pht ALL patient cells were serially xenotransplanted into immunodeficient NOG mice, and engrafted spleen cells were obtained 8 10 weeks after injection. Erythrocytes were removed by erythrocyte lysis buffer,