Improved supportive care, more precise risk stratification, and personalized chemotherapy based on the characteristics of leukemic cells and hosts (eg, pharmacokinetics and pharmacogenetics) have pushed the cure rate of childhood acute lymphoblastic leukemia to near 90%. Further increase in cure rate can be expected from the discovery of additional recurrent molecular lesions, coupled with the development of novel targeted treatment through high-throughput genomics and innovative drug-screening systems. We discuss specific areas of research that promise to further refine current treatment and to improve the cure rate and quality of life of the patients. (Blood. 2012;120(6):1165-1174)
IntroductionOptimal use of existing antileukemic agents and improved supportive care in contemporary clinical trials have improved the 5-year survival rate of childhood acute lymphoblastic leukemia (ALL) above 85% in developed countries (Table 1). [1][2][3][4][5][6][7][8] Further advances in survival and quality of life will require a better understanding of ALL pathobiology, the mechanisms of drug resistance, and drug disposition in the host, together with the development of innovative therapeutics. To this end, the advent of high-resolution genomewide analyses of gene expression, DNA copy number alterations, and epigenetic changes, and more recently, next-generation wholegenome and transcriptome sequencing have provided new insights into leukemogenesis, drug resistance, and host pharmacogenomics, identified novel subtypes of leukemia, and suggested potential targets for therapy. 9,10 Paralleling these advances has been the development of novel monoclonal antibodies, small molecule inhibitors, chemotherapeutics, and cell-based treatment strategies. 9 Here we discuss some of the current challenges and future directions in pediatric ALL research.
Emerging leukemia subtypesTraditionally, ALL has been classified into precursor T (or T-cell), precursor B, and B-cell (Burkitt) phenotypes, which are then further subdivided according to recurrent karyotypic abnormalities, including aneuploidy and translocations. 9,11 Detailed profiling of submicroscopic alterations and mutational analyses have allowed refinement of these classification schema, identification of genetic alterations that coexist and cooperate with chromosomal alterations in leukemogenesis, and discovery of new ALL subtypes that lack alterations on cytogenetic analysis. Like acute myeloid leukemia, 12 many ALL subtypes are characterized by genetic alterations that perturb multiple key cellular pathways, including hematopoietic development, signaling or proliferation, and epigenetic regulation. Recent studies have identified a novel high-risk immature T-cell subtype, termed "early T-cell precursor" ALL, which is characterized by immunologic markers and a gene expression profile reminiscent of double-negative 1 thymocytes that retain the ability to differentiate into both T-cell and myeloid, but not B-cell, lineages. 13 Whole genome sequencing showed that the mutational spectru...