We used flow cytometry to quantify minimal residual disease (MRD) in 56 patients with acute myeloid leukemia (AML) expressing a leukemia-associated phenotype. Thirty-four patients aged 18 to 60 years were entered into the AML-10 protocol (induction, consolidation, and autologous stem-cell transplantation [ASCT]), whereas 22 patients older than 60 years received the AML-13 protocol (induction, consolidation, and consolidation II). After induction, the level of MRD that was best associated with treatment outcome was 4.5 × 10−4 residual leukemic cells. However, the outcome in patients with at least 4.5 × 10−4 cells (n = 26) was not significantly different from that in patients with fewer leukemic cells (n = 30); there were 15 (58%) relapses in the first group and 12 (40%) relapses in the second. After consolidation, the most predictive MRD cutoff value was 3.5 × 10−4cells: 22 patients had an MRD level of 3.5 × 10−4 cells or higher and 17 (77%) of these patients had relapse, compared with 5 of 29 patients (17%) with lower MRD levels (P < .001). An MRD level of 3.5 × 10−4 cells or higher after consolidation was significantly correlated with poor or intermediate-risk cytogenetic findings, a multidrug resistance 1 (MDR1) phenotype, short duration of overall survival, and short duration of relapse-free survival (P = .014, .031, .00022, and .00014, respectively). In multivariate analysis, this MRD status was significantly associated with a high frequency of relapse (P < .001) and a short duration of overall (P = .025) and relapse-free survival (P = .007). ASCT did not alter the prognostic effect of high MRD levels after consolidation: the relapse rate after transplantation was 70%. Thus, we found that an MRD level of 3.5 × 10−4 cells or higher at the end of consolidation strongly predicts relapse and is significantly associated with an MDR1 phenotype and intermediate or unfavorable cytogenetic findings.

T-cel migration into tissue depends on a cascade of rapid and selective adhesive Intactios with endothellum. "Triggering" is a step in that cascade required to activate T-cell integrins. Hepatocyte The recruitment of T lymphocytes into tissue is regulated by a cascade of molecular events resulting in adhesion to endothelium followed by migration into tissue (1, 2). Initially, selectin-mediated interactions cause T cells to roll along the vessel wall, where they contact factors that trigger strong binding to endothelium by activating T-cell integrins. Thereafter migration into tissue is directed by locally active promigratory factors (1). Although the selectin and integrin components are relatively well defined, the factors responsible for triggering T-cell adhesion and directing migration into tissue are not. A recent model has proposed that a family of cytokines, the chemokines, trigger adhesion and migration of leukocyte subsets when they are immobilized on the endothelial surface by binding to proteoglycan (3,4).Two aspects of the adhesion cascade model are poorly understood. First, there must be diversity in the triggering step to account for the specificity of leukocyte subset recruitment (1) and it is unclear whether chemokines alone can provide this. Second, if they are to be relevant physiologically, trigger factors must activate integrins within seconds of interacting with the leukocyte (5,6). Such rapid effects of pro-adhesive cytokines on T cells have not been demonstrated. Here we report that a structurally distinct cytokine, hepatocyte growth factor (HGF), can induce adhesion and migration of T-cell subsets and that HGF and the chemokine macrophage inflammatory protein 113 (MEP-118) can induce cytoskeletal changes within seconds of T-cell exposure to them.HGF (also known as scatter factor) is a heparin-binding growth factor with structural homology to plasminogen that causes epithelial cells to proliferate, differentiate, and scatter by activating the tyrosine kinase receptor c-Met (7-10). Although HGF has not previously been shown to affect T lymphocytes, several findings suggest a potential role for HGF in leukocyte recruitment: (i) it is released by inflammatory cells (11,12), (ii) it can enhance both neutrophil (12) and B-lymphocyte (13) functions, (iii) it can induce motility in the J-111 monocyte cell line (14), and (iv) it is detected immunohistochemically on endothelium in tissue (15, 16). These properties of HGF led us to investigate its effect on T-cell migration and adhesion. METHODSIsolation of Resting Human T Cells. T cells and the following T-cell subsets, CD4+, CD8+, CD45RA-, and CD45RO-, were prepared by negative selection from peripheral blood of normal donors by using a mixture of monoclonal antibodies (mAbs) (17). Purity of the T cells was >95%.Migration Assays. Three assays were used. (i) Migration through protein-coated 5-pm-pore polycarbonate membranes was assessed with 48-well microchemotaxis chambers (4, 18). Membranes were coated by floating overnight at 40C on a s...

This review highlights new findings that have deepened our understanding of the mechanisms of leukemogenesis, therapy and resistance in acute promyelocytic leukemia (APL). Promyelocytic leukemia-retinoic acid receptor α (PML-RARa) sets the cellular landscape of acute promyelocytic leukemia (APL) by repressing the transcription of RARa target genes and disrupting PML-NBs. The RAR receptors control the homeostasis of tissue growth, modeling and regeneration, and PML-NBs are involved in self-renewal of normal and cancer stem cells, DNA damage response, senescence and stress response. The additional somatic mutations in APL mainly involve FLT3, WT1, NRAS, KRAS, ARID1B and ARID1A genes. The treatment outcomes in patients with newly diagnosed APL improved dramatically since the advent of all-trans retinoic acid (ATRA) and arsenic trioxide (ATO). ATRA activates the transcription of blocked genes and degrades PML-RARα, while ATO degrades PML-RARa by promoting apoptosis and has a pro-oxidant effect. The resistance to ATRA and ATO may derive from the mutations in the RARa ligand binding domain (LBD) and in the PML-B2 domain of PML-RARa, but such mutations cannot explain the majority of resistances experienced in the clinic, globally accounting for 5–10% of cases. Several studies are ongoing to unravel clonal evolution and resistance, suggesting the therapeutic potential of new retinoid molecules and combinatorial treatments of ATRA or ATO with different drugs acting through alternative mechanisms of action, which may lead to synergistic effects on growth control or the induction of apoptosis in APL cells.