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Genetic heterogeneity in drug-metabolizing enzyme/transporter (DMET) genes affects specific drug-related cancer phenotypes. To investigate the relationships between genetic variation and response to treatment in acute myeloid leukemia (AML), we genotyped 1931 variants on DMET genes in 94 CD33-positive AML patients enrolled in a phase III multicenter clinical trial combining Gemtuzumab-Ozogamicin (GO) with Fludarabine-Cytarabine-Idarubicin (FLAI) regimen, with the DMET Plus platform. Two ADH1A variants showed statistically significant differences (odds ratio (OR)=5.68, P=0.0006; OR=5.35, P=0.0009) in allele frequencies between patients in complete/partial remission and patients without response, two substitutions on CYP2E1 (OR=0.13, P=0.001; OR=0.09, P=0.003) and one on SLCO1B1 (OR=4.68, P=0.002) were found to differently influence liver toxicity, and two nucleotide changes on SULTB1 and SLC22A12 genes correlated with response to GO (OR=0.24, P=0.0009; OR=2.75, P=0.0029). Genetic variants were thus found for the first time to be potentially associated with differential response and toxicity in AML patients treated with a combination of GO-FLAI regimen. [ABSTRACT FROM AUTHOR]

Expression of c-Myb is required for normal hematopoiesis and for proliferation of myeloid leukemia blasts and a subset of T-cell leukemia, but its role in B-cell leukemogenesis is unknown. We tested the role of c-Myb in p190BCR/ABL-dependent B-cell leukemia in mice transplanted with p190BCR/ABL-transduced marrow cells with a c-Myb allele (Mybf/d) and in double transgenic p190BCR/ABL/Mybw/d mice. In both models, loss of a c-Myb allele caused a less aggressive B-cell leukemia. In p190BCR/ABL-expressing human B-cell leukemia lines, knockdown of c-Myb expression suppressed proliferation and colony formation. Compared with c-Mybw/f cells, expression of Bmi1, a regulator of stem cell proliferation and maintenance, was decreased in pre-B cells from Mybw/d p190BCR/ABL transgenic mice. Ectopic expression of a mutant c-Myb or Bmi1 enhanced the proliferation and colony formation of Mybw/d p190BCR/ABL B-cells; by contrast, Bmi1 downregulation inhibited colony formation of p190BCR/ABL-expressing murine B cells and human B-cell leukemia lines. Moreover, c-Myb interacted with a segment of the human Bmi1 promoter and enhanced its activity. In blasts from 19 Ph1 adult acute lymphoblastic leukemia patients, levels of c-Myb and Bmi1 showed a positive correlation. Together, these findings support the existence of a c-Myb-Bmi1 transcription-regulatory pathway required for p190BCR/ABL leukemogenesis. [ABSTRACT FROM AUTHOR]

The mammalian target of rapamycin (mTOR) serine/threonine kinase is the catalytic subunit of two multi-protein complexes, referred to as mTORC1 and mTORC2. Signaling downstream of mTORC1 has a critical role in leukemic cell biology by controlling mRNA translation of genes involved in both cell survival and proliferation. mTORC1 activity can be downmodulated by upregulating the liver kinase B1/AMP-activated protein kinase (LKB1/AMPK) pathway. Here, we have explored the therapeutic potential of the anti-diabetic drug, metformin (an LKB1/AMPK activator), against both T-cell acute lymphoblastic leukemia (T-ALL) cell lines and primary samples from T-ALL patients displaying mTORC1 activation. Metformin affected T-ALL cell viability by inducing autophagy and apoptosis. However, it was much less toxic against proliferating CD4+ T-lymphocytes from healthy donors. Western blot analysis demonstrated dephosphorylation of mTORC1 downstream targets. Unlike rapamycin, we found a marked inhibition of mRNA translation in T-ALL cells treated with metformin. Remarkably, metformin targeted the side population of T-ALL cell lines as well as a putative leukemia-initiating cell subpopulation (CD34+/CD7−/CD4−) in patient samples. In conclusion, metformin displayed a remarkable anti-leukemic activity, which emphasizes future development of LKB1/AMPK activators as clinical candidates for therapy in T-ALL. [ABSTRACT FROM AUTHOR]

Massively parallel pyrosequencing allows sensitive deep sequencing to detect molecular aberrations. Thus far, data are limited on the technical performance in a clinical diagnostic setting. Here, we investigated as an international consortium the robustness, precision and reproducibility of amplicon next-generation deep sequencing across 10 laboratories in eight countries. In a cohort of 18 chronic myelomonocytic leukemia patients, mutational analyses were performed on TET2, a frequently mutated gene in myeloproliferative neoplasms. Additionally, hotspot regions of CBL and KRAS were investigated. The study was executed using GS FLX sequencing instruments and the small volume 454 Life Sciences Titanium emulsion PCR setup. We report a high concordance in mutation detection across all laboratories, including a robust detection of novel variants, which were undetected by standard Sanger sequencing. The sensitivity to detect low-level variants present with as low as 1-2% frequency, compared with the 20% threshold for Sanger-based sequencing is increased. Together with the output of high-quality long reads and fast run time, we demonstrate the utility of deep sequencing in clinical applications. In conclusion, this multicenter analysis demonstrated that amplicon-based deep sequencing is technically feasible, achieves high concordance across multiple laboratories and allows a broad and in-depth molecular characterization of cancer specimens with high diagnostic sensitivity. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented which discusses a study on the isomatic mutations of isocitrate dehydrogenase 1 and 2 (IDHI and IDH2) in chronic myeloid leukemia (CML) and acute lymphoblastic leukemia (ALL) patients.

Chronic myeloid leukemia (CML) is caused by the BCR-ABL hybrid gene. The molecular mechanisms leading from chronic phase (CP) to blast crisis (BC) are not understood. However, both the presence and the levels of BCR-ABL seem to be important for CML progression. BCR-ABL is under the transcriptional control of BCR promoter. Here we focused on the gene expression control of BCR and BCR-ABL upon myeloid differentiation in healthy donors (HDs), CP and BC patients. As previously reported, BCR-ABL is downregulated during myeloid maturation in CP patients. A similar pattern was detected for BCR (but not for ABL) in CP-CML and in HD, thus suggesting that the two genes may be under a similar transcriptional control. In BC this mechanism is similarly impaired for both BCR-ABL and BCR. These data indicate the presence of an ‘in trans’ deregulated transcription of both BCR and BCR-ABL promoters, associated with CML progression. [ABSTRACT FROM AUTHOR]

The main reason for the unfavorable clinical outcome of BCR–ABL1-positive acute lymphoblastic leukemia (ALL) is genetic instability. However, how normal B-cell precursors acquire the genetic changes that lead to transformation has not yet been completely defined. We investigated the expression of the activation-induced cytidine deaminase (AID) and its role in clinical outcome in 61 adult BCR–ABL1-positive ALL patients. AID expression was detected in 36 patients (59%); it correlated with the BCR–ABL1 transcript levels and disappeared after treatment with tyrosine kinase inhibitors. Different AID splice variants were identified: full-length isoform; AIDΔE4a, with a 30-bp deletion of exon 4; AIDΔE4, with the exon 4 deletion; AIDins3, with the retention of intron 3; AIDΔE3-E4 isoform without deaminase activity. AID-FL predominantly showed cytoplasmic localization, as did the AID-ΔE4a and AID-ΔE3E4 variants, whereas the C-terminal-truncated AID-ΔE4 showed a slightly increased nuclear localization pattern. AID expression correlated with a higher number of copy number alterations identified in genome-wide analysis using a single-nucleotide polymorphism array. However, the expression of AID at diagnosis was not associated with a worse prognosis. In conclusion, BCR–ABL1-positive ALL cells aberrantly express different isoforms of AID that may act as mutators outside the immunoglobulin (Ig) gene loci in promoting genetic instability. [ABSTRACT FROM AUTHOR]

Mutations in nucleophosmin (NPM) exon 12 and the resulting delocalization of NPM into the cytoplasm are the most specific and frequent cellular events in acute myeloid leukemia patients (AML) with normal karyotype. Cytoplasmatic NPM (NPMc+) is associated with responsiveness to chemotherapy and better prognosis. The activation of nuclear factor-κB (NF-κB) has been demonstrated to occur in a subset of AML patients and is thought to induce resistance to many chemotherapeutical agents. In this study, we demonstrate the increased in vitro sensitivity of NPMc+ cells to chemotherapeutical agents and their reduced NF-κB activity. Furthermore, we provide evidence of the interaction between NPMc+ and NF-κB in the cytoplasm, resulting in the sequestration and inactivation of NF-κB. The cytosolic localization and consequent inactivation of NF-κB justifies the reduced NF-κB DNA-binding activity observed in NPMc+ patients. These data, taken together, may provide a possible explanation for the increased rate of chemosensitivity observed among the NPMc+ patients.Leukemia (2008) 22, 1234–1240; doi:10.1038/leu.2008.68; published online 10 April 2008 [ABSTRACT FROM AUTHOR]

A letter to the editor is presented regarding allogeneic stem cell transplantation (SCT) that was published in the 2008 issue of "Leukemia."

The article reports on the retraction of the article "Increase sensitivity to chemotherapeutical agents and cytoplasmatic interaction between the NPM leukemic mutant and NF-jB in AML carrying NPM1 mutations" that was published on April 10, 2008.