Gene Expression Profiling of Pediatric MLL-Rearranged Leukemia: Relation between Acute Lymphoblastic Leukemia, Acute Myeloid Leukemia, and Leukemic Cell Lines.

Although most patients with acute lymphoblastic leukemia (ALL) having MLL rearrangements suffer poor treatment outcome, there exists a subgroup of patients with this disease who enjoy long-term disease-free survival. In order to verify our previously reported new classification of this type of leukemia predicting treatment outcome, we analyzed gene expression profiles of MLL-rearranged leukemic cell lines and acute myeloid leukemia (AML) samples along with the previously reported ALL samples. Hierarchical clustering and the weighted vote method showed that cell line samples formed a strong association with the poorer prognosis subgroup in the classification, and that AML samples had some relationship with the better prognosis subgroup. Highly expressed genes in the poorer prognosis subgroup combined with cell line samples compared with the better prognosis subgroup include genes related to tumor aggressiveness, such as SNCG, GRM4, and EDG4. These results support the significance of the previously described classification associated with prognosis. Large-scale clinical studies, therefore, may be worth trying on the basis of this classification.