Expression and Fuactional Role of HERG1, K^+ Channels in Leukemic Cells and Leukemic Stem Cells

In order to investigate the expression and functional role of HERG1 K+ channels in leukemic cells and leukemic stem cells (LSCs), RT-PCR was used to detect the HERG1 K+ channels expression in leukemic cells and LSCs. The functional role of HERG1 K+ channels in leukemic cell proliferation was measured by MTT assay, and cell cycle and apoptosis were analyzed by flow cy- tometry. The results showed that herg mRNA was expressed in CD34+/CD38-, CD123+ LSCs but not in circulating CD34+ cells. Herg mRNA was also up-regulated in leukemia cell lines K562 and HL60 as well as almost all the primary leukemic cells while not in normal peripheral blood mononuclear cells (PBMNCs) and the expression of herg mRNA was not associated with the clinical and cytoge- netic features of leukemia. In addition, leukemic cell proliferation was dramatically inhibited by HERG K+ channel special inhibitor E-4031. Moreover, E-4031 suppressed the cell growth by induc- ing a specific block at the G1/S transition phase of the cell cycle but had no effect on apoptosis in leukemic cells. The results suggested that HERG1 K+ channels could regulate leukemic cells prolif- eration and were necessary for leukemic cells to proceed with the cell cycle. HERG1 K+ channels may also have oncogenic potential and may be a biomarker for diagnosis of leukemia and a novel potential pharmacological target for leukemia therapy.

Studying Human Leukemic Stem Cells in Mice

Transplantation of human leukemic cells into severe combined immunodeficiency(SCID)mice has been attempted to study leukemogenesis and to develop therapeuticmodalities.Previous models,however,were limited in efficient initiation orlong-term engraftment of leukemic cells following the transplantation of primaryhuman leukemic cells.The insufficient engraftment of primary leukemic cells couldbe caused by the residual innate immunity in CB-17/SCID or NOD/SCID mice.We

Characteristics of leukemic stem cells in acute leukemia and potential targeted therapies for their specific eradication

In acute myeloid leukemia(AML),a small cell population that contains stem cell features such as lack of differentiation,self-renewal potential,and drug resistance,can be identified.These so-called leukemic stem cells(LSCs)are thought to be responsible for relapse initiation after initial treatment leading to successful eradication of the bulk AML cell population.Since many studies have aimed to characterize and eliminate LSCs to prevent relapse and increase survival rates of patients,LSCs are one of the best characterized cancer stem cells.The specific elimination of LSCs,while sparing the healthy normal hematopoietic stem cells(HSCs),is one of the major challenges in the treatment of leukemia.This review focuses on several surface markers and intracellular transcription factors that can distinguish AML LSCs from HSCs and,therefore,specifically eliminate these stem cell-like leukemic cells.Moreover,previous and ongoing clinical trials of acute leukemia patients treated with therapies targeting these markers are discussed.In contrast to knowledge on LSCs in AML,insight into LSCs in acute lymphoid leukemia(ALL)is limited.This review therefore also addresses the latest insight into LSCs in ALL.

High frequency of CD34+CD38-/low immature leukemia cells is correlated with unfavorable prognosis in acute myeloid leukemia

AIM To evaluate the importance of the CD34+CD38-cell population when compared to the CD34+CD38+/low and CD34+CD38+/high leukemic cell sub-populations and to determine its correlations with leukemia characteristics and known prognostic factors, as well as with response to therapy and survival.METHODS Two hundred bone marrow samples were obtained at diagnosis from 200 consecutive patients with newly diagnosed acute myeloid leukemia(AML) were studied between September 2008 and December 2010 at our Institution(Hematology Department, Lyon, France). The CD34/CD38 cell profile was analyzed by multiparameter flowcytometry approach using 8 C panels and FACS CANTO and Diva software(BD Bioscience).RESULTS We analyzed CD34 and CD38 expression in bone marrow samples of 200 AML patients at diagnosis, and investigated the prognostic value of the most immature CD34+CD38-population. Using a cut-off value of 1% of CD34+CD38-from total "bulk leukemic cells" we found that a high(> 1%) level of CD34+CD38-blasts at diagnosis was correlated with advanced age, adverse cytogenetics as well as with a lower rate of complete response after induction and shorter disease-free survival. In a multivariate analysis considering age, leukocytosis, the % of CD34+ blasts cells and the standardized cytogenetic and molecular risk subgroups, a percentage of CD34+CD38-leukemic cells > 1% was an independent predictor of DFS [HR = 2.8(1.02-7.73), P = 0.04] and OS [HR = 2.65(1.09-6.43), P = 0.03].CONCLUSION Taken together, these results show that a CD34/CD38 "backbone" for leukemic cell analysis by multicolour flowcytometry at diagnosis provides useful prognostic information.

Sunitinib Reduces Acute Myeloid Leukemia Clonogenic Cells in Vitro and Has Potent Inhibitory Effect on Sorted AML ALDH+ Cells

Sunitinib is an orally administered, multi-target tyrosine kinase inhibitor that has been approved by the FDA for the treatment of renal cell carcinoma and imatinib resistant gastro-intestinal tumors. Anti-leukemic activity of sunitinib has been examined in early clinical trials with limited success. However, recent trials on acute myeloid leukemia (AML) patients carrying FLT3 mutations have shown promising results. Effects of sunitinib on leukemic clonogenic cells and potential leukemic stem cells have not been examined so far. We analyzed the anti-proliferative and apoptotic properties of sunitinib on AML-derived cell lines. We also tested the effect of sunitinib on AML patient derived clonogenic cells (AML-CFC), as well as flow-sorted potential leukemic progenitors. Peripheral blood or bone marrow samples were obtained from newly diagnosed AML patients and flow sorted for CD34+ CD133+ or ALDH+ cells. Umbilical cord blood derived CD34+ cells were used as normal controls. Sunitinib induced growth arrest and apoptosis in AML derived cell lines. In addition, 7 μM sunitinib induced 75% reduction of AML-CFC as compared to DMSO treated control (±6.79%;n = 4). In contrast, 7 μM sunitinib treatment of umbilical cord blood derived normal CD34+ cells showed 29% reduction in AML-CFC (±6.77%;n = 5). Treatment of ALDH+ cells sorted from 2 AML cases and CD34+ CD133+ cells from one patient showed reduction of AML-CFC on treatment with sunitinib. Our study highlighted a potent anti-proliferative and proapoptotic effect of sunitinib on AML cell lines, AML patient derived clonogenic cells and potential leukemic stem cells.

B-cell lymphoma-2 inhibition and resistance in acute myeloid leukemia

Spurred by better understanding of disease biology,improvements in molecular diagnostics,and the development of targeted therapies,the treatment of acute myeloid leukemia(AML)has undergone significant evolution in recent years.Arguably,the most exciting shift has come from the success of treatment with the B-cell lymphoma-2 inhibitor venetoclax.When given in combination with a hypomethylating agent or low dose cytarabine,venetoclax demonstrates high response rates,some of which are durable.In spite of this,relapses after venetoclax treatment are common,and much interest exists in elucidating the mechanisms of resistance to the drug.Alterations in leukemic stem cell metabolism have been identified as a possible escape route,and clinical trials focusing on targeting metabolism in AML are ongoing.This review article highlights current research regarding venetoclax treatment and resistance in AML with a focus on cellular metabolism.

Molecular and cellular bases of chronic myeloid leukemia

Chronic myeloid leukemia(CML)is a myeloproliferative disease characterized by the overproduction of granulocytes,which leads to high white blood cell counts and splenomegaly in patients.Based on clinical symptoms and laboratory findings,CML is classified into three clinical phases,often starting with a chronic phase,progressing to an accelerated phase and ultimately ending in a terminal phase called blast crisis.Blast crisis phase of CML is clinically similar to an acute leukemia;in particular,B-cell acute lymphoblastic leukemia(B-ALL)is a severe form of acute leukemia in blast crisis,and there is no effective therapy for it yet.CML is induced by the BCR-ABL oncogene,whose gene product is a BCR-ABL tyrosine kinase.Currently,inhibition of BCR-ABL kinase activity by its kinase inhibitor such as imatinib mesylate(Gleevec)is a major therapeutic strategy for CML.However,the inability of BCR-ABL kinase inhibitors to completely kill leukemia stem cells(LSCs)indicates that these kinase inhibitors are unlikely to cure CML.In addition,drug resistance due to the development of BCRABL mutations occurs before and during treatment of CML with kinase inhibitors.A critical issue to resolve this problem is to fully understand the biology of LSCs,and to identify key genes that play significant roles in survival and self-renewal of LSCs.In this review,we will focus on LSCs in CML by summarizing and discussing available experimental results,including the original studies from our own laboratory.

Treatment strategies in acute myeloid leukemia

Objective To summarize the risk stratification and current treatment strategies for acute myeloid leukemia （AML） and discuss the role of emerging novel agents that might be applied in future clinical trials.Data sources The data in this article were collected from PubMed database with relevant English articles published from 1991 to 2009.Study selection Articles regarding the risk stratification and therapeutic options of AML, as well as the characteristics of leukemic stem cells were selected.Results AML is a heterogeneous disease with variable clinical outcome dependent on several prognostic factors,including age, cytogenetics and molecular markers. The advances in the understanding of AML pathogenesis and development will generate potential novel agents that might improve the treatment results of standard chemotherapy.Conclusion Deeper insight into the multiple transforming events of AML may aid us in designing combinations of small molecule inhibitors based on the individual patient characteristics.