Development of a Novel Treatment Strategy Targeting JAK2 in Acute Myelogenous Leukemia.

Abstract Abstract 2619 Poster Board II-595 Somatic mutations in Janus kinase 2 (JAK2) gene activate JAK2/signal transducer and activator of transcriptions (STATs) signaling, leading to proliferation of hematopoietic cells. STAT3 and/or STAT5 were constitutively activated in the majority of patients with acute myelogenous leukemia (AML), although mutation of the JAK2 gene was an extremely rare event in AML. This study performed the immunohistochemichal examination to verify whether JAK2 was activated in AML (n=73, excluding acute promyelocytic leukemia) by utilizing the phosphor-specific antibody against JAK2. p-JAK2 was detectable in all cases examined, although its level varied between each patients (+, n=27; +/−, n=28; −/+, n=18). Statistical examination found that levels of p-JAK2 were correlated with leukocytosis (21.4 × 106/L in patients with high p-JAK2 vs 13.8 × 106/L in those with low p-JAK2, p<0.001) and lower complete remission rate (65.5% in patients with high p-JAK2 vs 83.3% in patients with low p-JAK2, p<0.02). In addition, there was a trend that high expression level of p-JAK2 was associated with poor prognosis in AML patients (median survival time 604 days in patients with high p-JAK2 vs 1431 days in those with low p-JAK2). Moreover, we found that the novel and specific inhibitor of the JAK2 kinase AZ960 potently inhibited the clonogenic growth of freshly isolated CD34+ AML cells from patients (n=6) with IC50 ranging from 0.01 to 0.1 mM. On the other hand, levels of p-JAK2 in CD34+ hematopoietic cells from healthy volunteers (n=3) were lower than those in CD34+AML cells, as measured by FACS, and their colony forming ability was not affected by AZ960. Furthermore, exposure of freshly isolated CD34+ AML cells to AZ960 (0.03–0.1 mM) induced apoptosis as assessed by induction of the cleaved forms of PARP as well as caspase 3, and downregulation of anti-apoptotic protein Bcl-xL. Taken together, JAK2 may be a promising molecular target for treatment of AML. Further studies are warranted to evaluate the efficacy of the JAK2 inhibitor in clinical settings. Disclosures: No relevant conflicts of interest to declare.

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CD34+/CD38− Acute Myelogenous Leukemia Cells Aberrantly Express Aurora Kinase A

Blood ◽

10.1182/blood.v118.21.1886.1886 ◽

2011 ◽

Vol 118 (21) ◽

pp. 1886-1886

Author(s):

Jing Yang ◽

Takayuki Ikezoe ◽

Mutsuo Furihata ◽

Chie Nishioka ◽

Akihito Yokoyama

Keyword(s):

Acute Myelogenous Leukemia ◽

Conflicts Of Interest ◽

Lymphoblastic Leukemia ◽

Specific Inhibitor ◽

Aurora Kinase ◽

Myelogenous Leukemia ◽

Hematopoietic Stem ◽

Aurora Kinase A ◽

Acute Myelogenous ◽

Kinase A

Abstract Abstract 1886 Aurora kinase A (AURKA) plays a pivotal role in the mitotic processes during cell division. We previously showed that AURKA was aberrantly expressed in hematological malignant cells including those from acute myelogenous leukemia (AML) and acute lymphoblastic leukemia, compared with CD34+ hematopoietic stem/progenitor cells isolated from healthy volunteers. This study found that freshly isolated CD34+/CD38− cells from individuals with AML (n=12) in which leukemia stem cells were supposed to be enriched expressed a greater amount of AURKA than their CD34+/CD38+ counterparts, as measured by real time RT-PCR. Blockade of AURKA by the specific inhibitor MLN8237 significantly inhibited proliferation and induced apoptosis of CD34+/CD38− AML cells, as assessed by the clonogenic assay and detection of the cleaved form of poly (ADP-ribose) polymerase by Western blot analysis, respectively. In addition, exposure of CD34+/CD38− AML cells to MLN8237 down-regulated levels of Bcl-2 family proteins and increased Bax/Bcl-2 expression ratio. Moreover, inhibition of AURKA by MLN8237 (30mg/kg for 14 consecutive days) impaired engraftment of CD34+/CD38− AML cells in severely immunocompromised mice (n=5, 49±32% in control vs 18±16% in MLN8237 treated mice, P<0.05), and prolonged their overall survival (P<0.05), compared with vehicle treated mice. Taken together, AURKA may be a promising molecular target to eliminate chemotherapy-resistant CD34+/CD38− AML cells. Disclosures: No relevant conflicts of interest to declare.

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Homoharringtonine Affects the Expression of PI3K and p-AKT of NB4, SHI-1 Leukemia Cells

Blood ◽

10.1182/blood.v116.21.4381.4381 ◽

2010 ◽

Vol 116 (21) ◽

pp. 4381-4381

Author(s):

Mingzhen Yang ◽

Xiaoyu Zhang ◽

Zhenqi Huang ◽

Qinhua Liu ◽

Lin Wang ◽

...

Keyword(s):

Cell Proliferation ◽

Protein Expression ◽

Acute Myelogenous Leukemia ◽

Conflicts Of Interest ◽

Mammalian Target Of Rapamycin ◽

Leukemia Cell ◽

Myelogenous Leukemia ◽

Leukemia Cells ◽

Growth And Survival ◽

Acute Myelogenous

Abstract Abstract 4381 Background: Homoharringtonine (HHT) was efficient in therapying patients with acute myeloid leukemia (AML) in China, but little is known about the mechanism of its action. The phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling axis plays a central role in cell proliferation, growth, and survival under physiological conditions and many human cancers, including acute myelogenous leukemia (AML). We try to explore the effect of HHT on PI3K/Akt pathway in AML cells, thus supplying theoretical basis for wider use of HHT. Method: The NB4 and SHI-1 cells were cultured in 20% FCS RPMI-1640 with different concentration of HHT, cell proliferation was detected with MTT, apoptosis was measured by FCM, the protein of PI3K and p-Akt were determined by Western blot. Result: 5ug/L HHT suppressed NB4 and SHI-1 cells proliferation and induced apoptosis after culture 24hr, 100ug/L HHT suppressed 71.29% NB4 and 64.83% SHI-1 cells proliferation respectively. Apoptosis increased obviously with the increasing HHT concentration and the culture time, the leukemia cell apoptosis was significant at 500ug/L HHT, about 41.84% NB4 cells and 46.88% SHI-1 cells were apoptosis when the HHT concentration was 100ug/L. The protein expression of PI3K, and p-Akt gradually declined with HHT concentration increasing, when 500ug/L HHT co-cultured with leukemia cells for 24 hours, The protein expression of PI3K and p-Akt were lowest. The p-Akt of NB4 and SHI-1 cells decreased 28.4% and 34.5% respectively at 5ug/L HHT for 48hr, the PI3K of NB4 and SHI-1 cells decreased 31.56% and 37.38% respectively at 10ug/L HHT for 48hr. Conclusion: HHT could inhibit NB4, SHI-1 cells proliferation and induce leukemia cells apoptosis, and could down-regulate the expression of PI3K and p-Akt significantly, this might be the one of mechanisms that HHT induce NB4 and SHI-1 cells apoptosis, we presume that HHT inhibit proliferation of acute myelogenous leukemia cells through effect of PI3K/Akt signaling pathways. Disclosures: No relevant conflicts of interest to declare.

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Sequential Acquisition of AML1-ETO and c-Kit Mutation Leads to Formation of Human t(8;21) Acute Myelogenous Leukemia Stem Cells,

Blood ◽

10.1182/blood.v118.21.3584.3584 ◽

2011 ◽

Vol 118 (21) ◽

pp. 3584-3584

Author(s):

Takahiro Shima ◽

Yoshikane Kikushige ◽

Toshihiro Miyamoto ◽

Koichi Akashi

Keyword(s):

Stem Cells ◽

Acute Myelogenous Leukemia ◽

Conflicts Of Interest ◽

Critical Role ◽

Myelogenous Leukemia ◽

Target Cells ◽

Hematopoietic Stem ◽

Kit Mutation ◽

Acute Myelogenous

Abstract Abstract 3584 The 8;21 translocation, one of the most general chromosomal abnormalities in acute myelogenous leukemia (AML), encodes the AML1-ETO chimeric fusion gene. Because AML1-ETO can inhibit the CBF complex to transactivate myeloid-lineage genes in a dominant negative fashion, the high level expression of this gene plays a critical role in inhibiting differentiation of target cells, which leads to progression of AML. We, however, have reported that patients maintaining a long-term remission retain AML1-ETO expression at a very low level that can be detected by nested RT-PCR. The AML1-ETO transcripts in these patients were derived from a small fraction of t(8;21)+ hematopoietic stem cells (HSCs) capable of multilineage differentiation (PNAS 2000). In fact, previous data shown that AML1/ETO knock-in or AML1/ETO transgenic mice did not develop AML. These data suggest that acquisition of the AML1-ETO fusion is not sufficient to develop t(8;21) AML. Since t(8;21) AML cells frequently possess constitutive active mutation of c-Kit, we hypothesized that the c-Kit mutation may work as a second oncogenic hit in t(8;21)+ HSCs to transform into AML. To test the hypothesis, we extensively analyzed the existence of c-Kit mutation within AML1-ETO+ HSCs from patients maintaining remission for a long-term. CD34+CD38− HSCs were purified from the bone marrow of patients in long-term remission, and were cultured in vitro to form colonies. These HSC-derived colonies were picked up, and tested for the presence ofAML1-ETO and c-Kit mutation. Five t(8;21) AML patients with c-Kit mutation were enrolled in this study. All of 1020 blastic colonies at diagnosis were positive for both AML1-ETO and c-Kit mutation. In 7187 colonies formed in the culture of remission marrow, almost 1% (89 colonies) of these colonies expressed AML1-ETO. Surprisingly, none of these colonies possessed c-Kit mutation, indicating that AML1-ETO+ clones in remission are not identical to these in t(8;21) AML. Accordingly, it is highly likely that HSCs first acquire AML1-ETO, and a fraction of these cells additionally mutated c-Kit, resulting in transformation into AML stem cells. This is the first clear-cut evidence that human HSCs transform into AML via multi-step oncogenesis in vivo. Disclosures: No relevant conflicts of interest to declare.

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Clonal Evolution and Devolution Following Chemotherapy in Adult Acute Myelogenous Leukemia.

Blood ◽

10.1182/blood.v120.21.2487.2487 ◽

2012 ◽

Vol 120 (21) ◽

pp. 2487-2487

Author(s):

Brian Parkin ◽

Peter Ouillette ◽

Yifeng Li ◽

Cheng Li ◽

Kerby Shedden ◽

...

Keyword(s):

Complete Remission ◽

Gene Mutation ◽

Induction Chemotherapy ◽

Acute Myelogenous Leukemia ◽

Conflicts Of Interest ◽

Gene Mutations ◽

Myelogenous Leukemia ◽

Stable Gene ◽

Paired Data ◽

Acute Myelogenous

Abstract Abstract 2487 Introduction: Despite significant advances in the understanding of the biology of adult acute myelogenous leukemia (AML), overall survival remains poor due chiefly to the high rate of relapse after achieving complete remission as well as primary failure of induction chemotherapy. Efforts to further unravel the mechanisms leading to relapse and primary refractory disease are critical in order to guide the development of effective and durable treatment strategies for AML. To that end, this study seeks to elucidate the clonal relationship of AML in various disease phases. Methods: We employed SNP 6.0 array-based genomic profiling of acquired copy number aberrations (aCNA) and copy neutral LOH (cnLOH) together with sequence analysis of recurrently mutated genes to characterize paired AML genomes. We analyzed 28 AML sample pairs from patients that achieved complete remission with chemotherapy and subsequently relapsed (median remission duration 272 days [range 25 – 1249 days]) and 11 sample pairs from patients with persistent disease following induction chemotherapy. AML cell samples were isolated with a Ficoll gradient, negatively selected using Miltenyi microbead columns, and then further purified with flow cytometric cell sorting. Processed DNA isolated from highly purified AML blasts and paired buccal DNA was hybridized to Affymetrix SNP 6.0 arrays. aCNA were visually identified using the dChip program in paired data displays and corroborated by algorithmic lesion scoring, and cnLOH was detected using internally developed software. In addition, 11 genes known to be recurrently mutated in AML (CEBPA, DNMT3A, IDH1, IDH2, RUNX1, BCORL1, NPM1, NRAS, KRAS, FLT3 and TP53) were resequenced in all 39 presentation samples to identify somatically acquired mutations. Genes found mutated in individual AML cases were subsequently tested for the persistence of the mutation in paired samples. Results: For the 28 paired specimens in the relapsed cohort, comparison of aCNA and cnLOH occurrences, gene mutation patterns and karyotypes revealed 6 cases that carried no aCNA/cnLOH at either presentation or relapse, but at presentation carried at least 1 gene mutation, all of which but one were stable in relapse (1 case lost a RUNX1 mutation but carried a t(8;21) in both disease stages); 11 cases that were characterized by the presence of aCNA/cnLOH at presentation, of which 55% (6 of 11) gained additional aCNA/cnLOH at relapse; 6 cases without aCNA/cnLOH at presentation that gained aCNA/cnLOH at relapse, of which 2 concurrently lost a FLT3-ITD or CEPBA mutation; and 5 cases that carried no informative genomic events. For the 11 paired specimens in the persistent AML cohort, the same comparison revealed 2 cases without aCNA/cnLOH before or after chemotherapy and stable gene mutations; 5 cases with aCNA/cnLOH at presentation that carried the same genomic lesions and gene mutations before and after chemotherapy; 3 cases with aCNA/cnLOH present at enrollment that lost some but not all of these aCNA/cnLOH and gained none after initial induction therapy; and 1 additional case that lost a FLT3-ITD. Comparative analysis of these patterns demonstrates that relapsed AML invariably represents reemergence or evolution of an antecedent clone. Furthermore, all individual aCNA or cnLOH detected at presentation persisted at relapse indicating that this lesion type is proximally involved in AML evolution. Analysis of informative paired persistent AML disease samples uncovered at least two coexisting dominant clones of which at least one was chemotherapy sensitive and one resistant. Conclusion: This detailed genomic analysis supports the conclusion that incomplete eradication of AML founder clones rather than stochastic emergence of fully unrelated novel clones underlies AML relapse and persistence with direct implications for clinical AML research. Disclosures: No relevant conflicts of interest to declare.

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Prognostic impact of trisomy 8 cytogenetic abnormality in acute myelogenous leukemia: Analysis of a large cohort (N=2187) of newly diagnosed patients.

Journal of Clinical Oncology ◽

10.1200/jco.2013.31.15_suppl.7089 ◽

2013 ◽

Vol 31 (15_suppl) ◽

pp. 7089-7089

Author(s):

Gautam Borthakur ◽

Cecilia Ysabel Arana Yi ◽

Jorge E. Cortes ◽

Wei Qiao ◽

Tapan M. Kadia ◽

...

Keyword(s):

Acute Myelogenous Leukemia ◽

Remission Rate ◽

Myelogenous Leukemia ◽

Cancer Center ◽

Prognostic Impact ◽

Intermediate Risk ◽

Newly Diagnosed ◽

Trisomy 8 ◽

Acute Myelogenous ◽

Md Anderson

7089 Background: Trisomy 8 is grouped as intermediate risk in cytogenetic (CG) classifications of acute myelogenous leukemia (AML). In a multi-variate analysis of MRC data, trisomy 8 was associated with worse overall survival (OS). Methods: Between years 1993-2012, 2,187 patients (pts) with newly diagnosed AML presented at MD Anderson Cancer Center and 21 (10%) were with a trisomy 8 CG abnormality. The median age of trisomy 8 pts was 63 years (range, 17-89 years) and 59% were males. Sixty four (30%) had isolated trisomy 8, 45 (21%) had trisomy 8 +≤2 additional cytogenetic abnormalities and 102 (49%) had trisomy 8 + ≥3 additional abnormalities. Thirty three percent of pts with trisomy 8+≤2 additional abnormalities, had secondary AML compared to 21% of diploid CG (p=.007). Mutations in the FLT3 gene was seen in 9% and N or KRAS gene in 8%. Results: The overall remission rate (RR) was 47%, 53% and 43% among pts with trisomy 8 alone, trisomy 8+≤2 and trisomy 8+≥3 abnormalities respectively. Among pts <60 years of age and with trisomy 8 + ≤2 abnormalities, RR was 71% and the same was 77% for pts with diploid CG. For pts ≥ 60 years, the RRs were 26% and 57% respectively. Among pts ≥ 60 years and trisomy 8 with complex CG (≥3 additional abnormalities) the RR was 38% and that for patients with complex (non-trisomy 8) CG was 41%. Patients with trisomy 8 either alone or ≤2 additional abnormalities had a shorter OS (p= .04 and .05 respectively, median 10.8 and 8.6 months vs 16.5 months) compared to those with diploid CG. Event free survival was also shorter among patient with isolated trisomy 8 versus those with diploid CG (p=.008, median 2.9 versus 7.5 months). On the other hand, patients with trisomy 8+≥3 abnormalities had outcomes comparable to non-trisomy 8 CG group. Conclusions: Non-complex CG trisomy 8 is associated with worse clinical outcome in patients with AML than those with diploid CG and its inclusion in intermediate risk group may need reconsideration. The most adverse impact appears to be from lower RR among patients with trisomy 8+≤2 additional abnormalities and ≥60 years of age.

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Correlation of cytogenetic patterns and clinicobiological features in adult acute myeloid leukemia expressing lymphoid markers [see comments]

Blood ◽

10.1182/blood.v79.3.720.bloodjournal793720 ◽

1992 ◽

Vol 79 (3) ◽

pp. 720-727

Author(s):

A Cuneo ◽

JL Michaux ◽

A Ferrant ◽

L Van Hove ◽

A Bosly ◽

...

Keyword(s):

Acute Myelogenous Leukemia ◽

Remission Rate ◽

Group Iv ◽

Myelogenous Leukemia ◽

Trisomy 13 ◽

Clinicopathologic Features ◽

Group Iii ◽

Group I ◽

Acute Myelogenous ◽

Ph Chromosome

Cytogenetic, biomolecular, and clinicopathologic features were retrospectively studied in 34 adult patients with acute myelogenous leukemia expressing one or more of the following lymphoid-associated markers (LMs): CD7, CD2, CD10, CD19, CD22, TdT. Six patients showed 11q23 rearrangements (group I); three patients had the classic Ph chromosome (group II); 15 patients had aberrations of the myeloid type (group III), including four patients with structural aberrations of 13q or trisomy 13, three patients with 7q and 1q anomalies, and two patients with trisomy 11q. Ten patients had a normal karyotype (group IV). Anomalies exclusively associated with lymphoid malignancies were not seen. Ig H and/or T-cell receptor genes were found to be rearranged in 50% and 66% of patients in cytogenetic groups I and II, respectively, versus 8% in group III and 12% in group IV. Likewise, more than one LM was more frequently detected in groups I and II. In group III, two of four patients with aberrations of chromosome 13 expressed two or more lymphoid features. Clinically, patients belonging to cytogenetic groups I and II were generally young, presented with a high white blood cell (WBC) count, and had a low complete remission rate. Survival in Ph chromosome-positive cases was uniformly short. We conclude that although there is no cytogenetic anomaly specifically associated with acute myelogenous leukemia expressing LM, a Morphologic, Immunologic, and Cytogenetic classification may constitute a working basis for further studies aimed at a better definition of clinicopathologic features and optimal treatment strategies for these leukemias.

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Treatment of patients over 50 years of age with acute myelogenous leukemia with a combination of rubidazone and cytosine arabinoside, vincristine, and prednisone (ROAP)

Blood ◽

10.1182/blood.v58.3.584.bloodjournal583584 ◽

1981 ◽

Vol 58 (3) ◽

pp. 584-591 ◽

Cited By ~ 1

Author(s):

MJ Keating ◽

KB McCredie ◽

RS Benjamin ◽

GP Bodey ◽

A Zander ◽

...

Keyword(s):

Cytosine Arabinoside ◽

Acute Myelogenous Leukemia ◽

Older Patients ◽

Remission Rate ◽

Myelogenous Leukemia ◽

Control Group ◽

Younger Patients ◽

Hematologic Disorder ◽

Significant Difference ◽

Acute Myelogenous

We administered a combination of rubidazone, cytosine arabinoside, vincristine, and prednisone (ROAP) to 91 patients with acute myelogenous leukemia who were 50 yr of age or older. These patients had been identified in previous studies to be a group with a relatively poor prognosis. One-third of the patients had an antecedent hematologic disorder prior to treatment. Forty patients (48%) obtained a complete hematologic and clinical remission. A history of an antecedent hematologic disorder, male sex, and absence of Auer rods were adverse factors for achieving remission in this older population. More than half of the patients achieved remission in one course. The major cause of failure to obtain a remission was death due to infection, 40% of which were caused by fungi. Resistance to chemotherapy, although uncommon, was noted more frequently in patients with an antecedent hematologic disorder. Univariate and multivariate prognostic factor analysis was used to compare these patients with a historical control group treated with a program in which adriamycin was used instead of rubidazone (AdOAP). No significant difference in remission rate was detected. Cyclocytidine was used as a maintenance agent in this study, and while the median remission duration was only 37 wk, 30% of patients are expected to be in remission for 2 yr. Chemotherapy programs combining an anthracycline with cytosine arabinoside, given to older patients in similar fasion to younger patients will achieve remissions in one-half of a group of older patients. These remissions are of comparable quality to those of younger patients. Mathematical models derived from analysis of prognostic factors are of use in identifying patients likely to fail these programs who are in need of innovative approaches to treatment.

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Clofarabine Plus Cytarabine Compared With Cytarabine Alone in Older Patients With Relapsed or Refractory Acute Myelogenous Leukemia: Results From the CLASSIC I Trial

Journal of Clinical Oncology ◽

10.1200/jco.2011.37.9743 ◽

2012 ◽

Vol 30 (20) ◽

pp. 2492-2499 ◽

Cited By ~ 121

Author(s):

Stefan Faderl ◽

Meir Wetzler ◽

David Rizzieri ◽

Gary Schiller ◽

Madan Jagasia ◽

...

Keyword(s):

Acute Myelogenous Leukemia ◽

Remission Rate ◽

Disease Free Survival ◽

Myelogenous Leukemia ◽

Free Survival ◽

End Point ◽

Common Grade ◽

Acute Myelogenous ◽

Grade 3

Purpose To compare the receipt of clofarabine plus cytarabine (Clo+Ara-C arm) with cytarabine (Ara-C arm) in patients ≥ 55 years old with refractory or relapsed acute myelogenous leukemia (AML). Patients and Methods Patients were randomly assigned to receive either clofarabine (Clo) 40 mg/m2 or a placebo followed by Ara-C 1 g/m2 for five consecutive days. The primary end point was overall survival (OS). Secondary end points included event-free survival (EFS), 4-month EFS, overall remission rate (ORR; complete remission [CR] plus CR with incomplete peripheral blood count recovery), disease-free survival (DFS), duration of remission (DOR), and safety. Results Among 320 patients with confirmed AML (median age, 67 years), the median OS was 6.6 months in the Clo+Ara-C arm and 6.3 months in the Ara-C arm (hazard ratio [HR], 1.00; 95% CI, 0.78 to 1.28; P = 1.00). The ORR was 46.9% in the Clo+Ara-C arm (35.2% CR) versus 22.9% in the Ara-C arm (17.8% CR; P < .01). EFS (HR: 0.63; 95% CI, 0.49 to 0.80; P < .01) and 4-month EFS (37.7% v 16.6%; P < .01) favored the Clo+Ara-C arm compared with Ara-C arm, respectively. DFS and DOR were similar in both arms. Overall 30-day mortality was 16% and 5% for CLO+Ara-C and Ara-C arms, respectively. In the Clo+Ara-C and Ara-C arms, the most common grade 3 to 4 toxicities were febrile neutropenia (47% v 35%, respectively), hypokalemia (18% v 11%, respectively), thrombocytopenia (16% v 17%, respectively), pneumonia (14% v 10%, respectively), anemia (13% v 0%, respectively), neutropenia (11% v 9%, respectively), increased AST (11% v 2%, respectively), and increased ALT (10% v 3%, respectively). Conclusion Although the primary end point of OS did not differ between arms, Clo+Ara-C significantly improved response rates and EFS. Study follow-up continues, and the role of clofarabine in the treatment of adult patients with AML continues to be investigated.

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HSP70 Inhibitor, YK5, Ablates Blast, Progenitor and Stem Cell Populations in Primary Acute Myelogenous Leukemia Cells

Blood ◽

10.1182/blood.v118.21.2493.2493 ◽

2011 ◽

Vol 118 (21) ◽

pp. 2493-2493

Author(s):

Juan Felipe Rico ◽

Krishan K. Sharma ◽

Yanlong Kang ◽

Tony Taldone ◽

Hardik Patel ◽

...

Keyword(s):

Flow Cytometry ◽

Stem Cell ◽

Acute Myelogenous Leukemia ◽

Poor Prognosis ◽

Hematopoietic Cells ◽

Myelogenous Leukemia ◽

Great Promise ◽

Cell Populations ◽

Acute Myelogenous ◽

Stem Cell Populations

Abstract Abstract 2493 Prognosis for acute myelogenous leukemia (AML) with traditional chemotherapeutic agents remains poor, most patients relapse and die of their disease. Studies have shown that AML can be originated and maintained by leukemia stem cells (LSCs) and that a high percentage of phenotypically-defined LSCs correlate to especially poor prognosis. Thus, novel therapies that can eliminate LSCs are needed. Upregulation of HSP70 has been described in human cancer cells and is often associated with chemoresistance and poor prognosis. Therefore, HSP70 represents a novel target for cancer therapy. Due to this, we tested a novel inhibitor of tumor-HSP70, YK5, and found that it can induce potent cell death in AML cells including progenitor and stem cell populations with minimal effects in normal hematopoietic cells. Fifteen primary AML patient samples were treated with YK5 in varying concentrations for 48 hours to determine the LD50 of YK5. The viability of these samples was determined by multiparameter flow cytometry using cell surface markers to distinguish, lymphocytes, blasts, progenitor and stem cell populations in conjunction with Annexin V and 7AAD. Mean LD50 for all samples tested was 4.5μM (CI 95% 2.239–6.853). Three of these samples had very low LD50s below 2.5μM and only one sample demonstrated relative resistance with a LD50 that was greater than 15μM. Notably, progenitor and stem cell populations were also targeted while normal remaining lymphocytes were spared. Furthermore, we found that LSCs in a subset of patient samples treated with YK5 exhibited higher sensitivity to the compound when compared to blast cells. Importantly, treatment of primary AML samples with 5μM YK5 resulted in a 63% decrease in colony forming ability when compared to untreated control (N=5), suggesting that YK5 can impair malignant progenitors. In contrast, normal CD34+ cord blood cells after treatment with 5μM YK5 for 48hrs exhibited a viability of 57% (N=3). Xenotransplant assays are currently ongoing to determine the ability of YK5 to inhibit LSC function. Treatment with YK5 resulted in a decrease in phosphorylation of STAT5, determined by flow cytometry. Taken together, HSP70 inhibition is a promising potential treatment for AML and has the potential to eradicate leukemic stem and progenitor cells while sparing normal hematopoietic cells. Thus, targeting HSP70 in AML appears to hold great promise. *JFR and KKS contributed equally to this project Disclosures: Roboz: EpiCept: Consultancy; ChemGenex: Consultancy; Celgene: Consultancy; Boehringer Ingelheim: Consultancy.

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