br Introduction Multiple signal transduction pathways in nor

Introduction Multiple signal transduction pathways in normal and malignant BEZ 235 manufacturer converge on Bcl-2 family proteins, which stand at the crossroads between cell survival and apoptosis. The seminal event in the intrinsic pathway of apoptosis is mitochondrial outer membrane permeabilization (MOMP), induced by the “effector” Bcl-2 family proteins, Bax and Bak. The anti-apoptotic proteins are Bcl-2, Bcl-XL, Bcl-w, Mcl-1, Bfl-1/A1 and Bcl-B. The “multi-domain” pro-apoptotic proteins are Bax, Bak and Bok, which share homology in domains BH (Bcl-2 homology) 1–3. The other pro-apoptotic Bcl-2 family proteins share only the BH3 domain and are termed “BH3-only” proteins; these include Bim, Bid, Bad, Bik, Hrk, Bmf, Puma and Noxa. The BH3 domain enables binding to a hydrophobic groove on the surface of the anti-apoptotic Bcl-2 molecules. Under normal conditions, pro-apoptotic BH3-only proteins prevent the anti-apoptotic Bcl-2 proteins from engaging with the apoptosis effectors Bax and Bak, allowing the latter to trigger apoptosis upon receipt of a death signal. Alternatively, “direct activator” BH3-only proteins may be held in check by their anti-apoptotic counterparts. Fig. 1 illustrates some of these concepts.
Mcl-1 Mcl-1 is distinguished from other anti-apoptotic Bcl-2 proteins in that it has a very short half-life (only 2–4h in most cells), making it dependent upon active transcription and translation for its maintenance. Mcl-1 sequesters, in conjunction with Bcl-XL, the apoptotic effector Bak on the mitochondrial surface, protecting against Bak oligomerization and the induction of MOMP. Mcl-1 also interacts with and sequesters the pro-apoptotic proteins Bim and truncated Bid. Noxa antagonizes Mcl-1 and promotes its proteasomal degradation, freeing Bak and Bim (Fig. 1). Because of structural differences, Mcl-1 is not bound by ABT-737, a potent small-molecule “BH3-mimetic” antagonist of Bcl-2, Bcl-XL and Bcl-w, which thus mimics the actions of Bad (Fig. 1). Indeed, up-regulation of Mcl-1 represents an important mechanism underlying leukemia cell resistance to ABT-737. While up-regulation of Mcl-1 has been described at the time of AML relapse, in fms-like tyrosine kinase-internal tandem duplication (FLT3-ITD) AML stem cells, and in the regulation of stem cell self-renewal, the most compelling evidence to date in support of a critical role for Mcl-1 in the survival of human AML cells emanates from a recent study in which deletion of Mcl-1, but not loss or pharmacological blockade of Bcl-XL, Bcl-2, or Bcl-w, induced the death of transformed AML and cured disease in AML-afflicted mice.
Conclusion
Contributions
Introduction In literature, two types of i(5)(p10) are observed :
Materials and methods
Results
Discussion To date, an i(5)(p10) has been found in a very small number of patients (10 AML, 4MDS, one secondary MDS after treatment of a multiple myeloma). In particular, among MDS patients there were one case of refractory cytopenia with multilineage dysplasia and another one of refractory anemia with ringed sideroblasts. Recent studies have displayed a non random relationship between C282Y and H63D mutations of hemochromatosis gene and myelodysplasia, suggesting a possible role of iron overload in pathogenesis of myelodysplastic disorders.
Conflict of interest statement
Acknowledgments
Introduction The Bcr-Abl fusion protein, central to the pathogenesis of chronic myelogenous leukemia (CML), interacts with a variety of effector proteins, leading to deregulated cellular proliferation, decreased adherence of leukemia cells to the bone marrow stroma, and a reduced apoptotic response to mutagenic stimuli. The revolutionary results of the International Randomized Study of Interferon and STI571 (IRIS), a phase III randomized trial of imatinib compared with the combination of interferon alfa and cytarabine in newly diagnosed patients with chronic phase CML (CML-CP), dramatically transformed the therapeutic landscape of CML. The second generation Bcr-Abl TKIs dasatinib and nilotinib were initially approved for CML patients intolerant of or resistant to imatinib, and subsequently for previously untreated patients with CML-CP. Recently, another second generation Bcr-Abl TKI, bosutinib (Bosulif®), has been approved for the treatment of patients with all phases of CML who have demonstrated resistance or intolerance to prior therapy.