Impact Of Dysplasia On Outcome Of Patients With Acute Myeloid Leukemia and Response To Allogeneic Hematopoetic Stem Cell Transplantation

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 5551-5551
Author(s):  
Shatha Farhan ◽  
Catherine Carroll ◽  
Danielle Pelland ◽  
Jose Carlos Velasco ◽  
Susan Wautelet ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Acute Myeloid Leukemia ◽  
Survival Time ◽  
Median Survival ◽  
Peripheral Blood ◽  
Median Survival Time ◽  
Myeloid Leukemia ◽  
Median Number ◽  
The Impact ◽  
Acute Myeloid

Abstract Background Myelodysplastic syndromes (MDS) are a heterogeneous group of malignancies characterized by dysplasia, cytopenia, ineffective hematopoiesis and by an increased risk of transformation to acute myeloid leukemia (AML). Recurrent aberrant karyotypes cannot entirely account for the genetic defects that are at the basis of the pathogenesis of MDS, as they are detected only in approximately 50% of patients. Allogeneic hematopoietic cell transplantation (HCT) likely prolongs survival in patients with AML and MDS. In this report, we evaluated the impact of presence of dyspoesis in paients with AML with or without cytogenetic (CG) abnormality on outcome in our center. Methods We retrospectively reviewed all patients who were diagnosed with AML (non promyelocytic) in our center between 2002 and 2012. Primary objective was to study the impact of MDS with or without CG abnormalities on outcome of patients with AML. Demographics and disease-related variables were collected. OS was defined as the time from diagnosis to the time of death or last contact. Results Between 2002 and 2012, 123 patients with high or intermediate risk AML patients were treated at our center. Median age at diagnosis was 60 (range 19-89). Median OS for all patients was 368 days. Of 123 patients, 51 had MDS while 73 did not. CG abnormalities were present in 35 (68%) of patients with dyspoetic changes. Median age of AML patients with MDS was 59 while median age of AML without MDS patients was 55. Median number of blasts in bone marrow and peripheral blood in AML patients with MDS was 38% and 6% respectively. While median number of blasts in bone marrow and peripheral blood in AML patients without MDS was 67% and 39% respectively. Of 51 AML patients with MDS, 14 received HCT with median age of 56. Half of these received myeloablative regimen while the other half received reduced toxicity regimen. The median survival time for AML patients without MDS was 401 days while the median survival time for AML patients with MDS was 278 days (p = 0.0201), Fig1. For AML with MDS who received HCT, the median survival time was 586 days while it was 164.5 days for AML patient with MDS who did not receive HCT (p = 0.0013), Fig2. Conclusion In this small cohort from a single center, the results suggest that AML patients with dyspoetic changes do have a worse prognosis despite having lower percentage of blasts in bone marrow or peripheral blood. This can be explained by what Walter et al reprted, using next-generation sequencing, that the proportion of neoplastic marrow cells is indistinguishable in MDS and secondary-AML even with myeloblast count of zero. HCT can be performed in those patients including older patients with promising results. Disclosures: No relevant conflicts of interest to declare.

CXCR4 Invalidation Limits the MLL-ENL Induced Leucemogenesis in Vivo

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 4089-4089
Author(s):  
Yanyan Zhang ◽  
Hadjer Abdelouahab ◽  
Aline Betems ◽  
Monika Wittner ◽  
William Vainchenker ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Acute Myeloid Leukemia ◽  
Survival Time ◽  
Median Survival ◽  
Median Survival Time ◽  
Myeloid Leukemia ◽  
Conflicts Of Interest ◽  
Hematopoietic Stem ◽  
Acute Myeloid

Abstract Abstract 4089 The receptor CXCR4 and its ligand SDF-1 play major physiological roles especially on hematopoietic stem cells homing and retention. Many studies have implicated CXCR4 in the invasion by tumor cells of organs that produce SDF-1. In acute myeloid leukemia, the physiological role of CXCR4 is not fully understood. We used retrovirus to express MLL-ENL oncogene in CXCR4+/+ and CXCR4−/− hematopoietic primitive cells (Lin- isolated from fetal liver) and showed that CXCR4 is dispensable for generation of immortalized colonies in vitro. To determine CXCR4 function in vivo, CXCR4+/+ and CXCR4−/− transformed cells were transplanted into lethally irradiated mice. Whatever their phenotype, the recipient developed a myelo-monocytique leukemia characterized by their expression of Gr-1 and Mac-1. As expected, all recipients of MLL-ENL transduced CXCR4+/+ cells were moribund within 35 to 80 days post transplant (median survival time: 50 days). Strikingly, recipients of MLL-ENL transduced CXCR4−/− cells showed significantly increased lifespan, with a median survival time of 90 days. The cellularity of the peripheral blood of recipients of MLL-ENL transduced cells displayed considerable increases over time although this increase was much lower in CXCR4−/− than in CXCR4+/+ chimera. Bone marrow of MLL-ENL transduced CXCR4−/− chimera had moderately decreased numbers of mononuclear cells. There were important numbers of leukemic CD45.2+/Gr1+/Mac1+/c-kit+ cells in spleen from MLL-ENL CXCR4+/+ chimera which suggested that CXCR4 is important for leukemic progenitors cells retention in the bone marrow and especially in the spleen. The homing capacity of transduced CXCR4+/+ cells is comparable to the CXCR4−/− cells. Finally, more DNA damages were found in the BM cells of MLL-ENL CXCR4−/− chimera. All these results were confirmed by treating of MLL-ENL CXCR4+/+ chimera with CXCR4 inhibitor (TN140). These results demonstrated that in absence of CXCR4, the cells transduced by oncogene MLL-ENL are capable of generating leukemia in the recipients. However, mice transplanted with MLL-ENL transduced CXCR4−/− FL cells developed acute myeloid leukemia with reduced aggressiveness and organ infiltration, which is associated with induced differentiation and DNA instability. These results indicated that the MLL-ENL progenitors are dependent on CXCR4 for their maintenance in the BM and spleen suggesting that CXCR4 inhibitors might have potential therapeutic applications. Disclosures: No relevant conflicts of interest to declare.

Expression of Angiopoietins and Their Receptor Tie2 in the Bone Marrow of Patients with Acute Myeloid Leukemia.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1894-1894
Author(s):  
Christoph Schliemann ◽  
Ralf Bieker ◽  
Teresa Padro ◽  
Torsten Kessler ◽  
Heike Hintelmann ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Acute Myeloid Leukemia ◽  
Myeloid Leukemia ◽  
Critical Role ◽  
Angiogenic Factor ◽  
Term Survival ◽  
Bone Marrow Biopsies ◽  
Cox Regression Analysis ◽  
The Impact ◽  
Acute Myeloid

Abstract Angiopoietin-1 (Ang-1) and its natural antagonist Angiopoietin-2 (Ang-2), both ligands for the receptor tyrosine kinase Tie2, are known to play an essential role in normal and pathological angiogenesis. However, the importance of angiopoietin signaling in the pathophysiology of hematologic neoplasias such as acute myeloid leukemia (AML) remains to be elucidated. We investigated the expression of Ang-1, Ang-2 and Tie2 by immunohistochemical analyses in bone marrow biopsies of 64 adult patients with newly diagnosed AML and correlated angiogenic factor expression with clinicopathological variables and long-term survival. Expression of Ang-2 was significantly increased in the bone marrow of AML patients (median [interquartile ranges]: 4.7 [3.3 – 5.7] AU [arbitrary units]) as compared with 16 control patients (1.5 [1.5 – 1.8] AU; P < 0.0001). In contrast, Ang-1 expression levels in AML patients did not differ from those found in controls. Thus, we observed a reversal of the Ang-1 and Ang-2 expression balance in the neoplastic bone marrow (Ang-2:Ang-1 ratio: 1.73) as compared with normal bone marrow (0.51; P < 0.0001). Furthermore, the angiopoietin receptor Tie2 was significantly overexpressed in leukemic blasts (3.8 [2.8 – 4.9] AU vs. 1.8 [1.6 – 2.3] AU; P < 0.0001). Patients expressing high levels of Ang-2 showed significantly longer overall survival (OS) than those with low Ang-2 levels (52.7 vs. 14.7 months; P = 0.039). The impact of Ang-2 expression on OS was especially evident in AML patients simultaneously expressing low levels of Ang-1 (P = 0.0298). Multivariate Cox regression analysis revealed karyotype and Ang-2 expression as independent prognostic factors for OS (hazard ratio [CI]: 3.06 [1.39 – 6.70] and 0.31 [0.14 – 0.69], respectively; P < 0.01). In conclusion, these data provide evidence that the alteration of angiopoietin balance in favor of Ang-2 may play a critical role in the pathophysiology of AML. Furthermore, high pre-therapeutic bone marrow Ang-2 levels indicate a favorable prognosis in polychemotherapy treated AML by a yet unknown mechanism.

Treatment of Acute Myeloid Leukemia in a Community Hospital.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 4575-4575
Author(s):  
Mandeep S. Dhami ◽  
Anca Bulgaru ◽  
Kandhasamy Jagathambal ◽  
Dinesh Kapur ◽  
Dennis E. Slater ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Acute Myeloid Leukemia ◽  
Median Survival ◽  
Myeloid Leukemia ◽  
Community Hospital ◽  
Care Center ◽  
Tertiary Care ◽  
Cell Transplant ◽  
Number Of Patients ◽  
Acute Myeloid

Abstract Optimal management of patients with acute myeloid leukemia requires an accurate diagnosis along with cytogenetics and an intensive systemic chemotherapy regimen administered by a multidisciplinary team of experienced physicians, nurses and other support staff. It has been suggested that such complex patients should be treated only at tertiary care centers. However, it is often difficult for patients and families to receive care at teratiary care center which may be at a great distance from their home. Here we present a retrospective review of all patients diagnosed and treated for acute myeloid leukemia at William W Backus Hospital, a 213 bed acute care hospital serving a community of 70,000 in Norwich, Connecticut between the years 2000 and 2005. A total of 44 patients were treated during this period. There were 22 males and 22 females. The median age was 67.5 years. Bone Marrow samples were evaluated by a hematopathologist (histopathology, flowcytometry and cytogenetics) at a near-by tertiary care center. FAB subgroups and cytogenetics were similar to other published studies. APML patients are not included in this analysis. The median survival for the entire group was 14.7 months ranging from 2 days to 113 months. Fourteen patients were alive, all in continued clinical remission except one with relapsed disease and one patient remains transfusion dependent. Median survival was 15.2 months for men compared to 13.2 months for women. Four patients were referred for bone marrow/stem cell transplant after induction therapy. The limitation of this study is the relatively small number of patients as one would expect from a study done at a small community hospital. Nevertheless, it appears that the median survival of our patients is similar to a pooled analysis of five SWOG trials published by Gundacker et al. We conclude that most patients with acute myeloid leukemia can be managed in a community hospital with commitment and experience to treat such patients. Treatment outcomes (median survival) Study Number of Patients Under 55 55 – 65 65 – 75 Over 75 *Gundacker et al. Blood, 1 May 2006, volume 107, 3481–3485 Current study 44 17.1 m 18 m 11.7 m 5.7 m Gundacker et al* 968 18.8 m 9.0 m 6.9 m 3.5 m

Detection of Nucleophosmin Gene Mutations in Plasma from Patients with Acute Myeloid Leukemia: Clinical Significance and Implications.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 2855-2855
Author(s):  
Wanlong Ma ◽  
Xi Zhang ◽  
Iman Jilani ◽  
Farhad Ravandi ◽  
Elihu Estey ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Acute Myeloid Leukemia ◽  
Peripheral Blood ◽  
Myeloid Leukemia ◽  
Gene Mutations ◽  
Leukemic Cells ◽  
Striking Difference ◽  
Plasma Dna ◽  
Npm1 Mutation ◽  
Acute Myeloid

Abstract Nucleotides insertion in the nucleophosphamin (NPM1) gene has been reported in about one third of patients with acute myeloid leukemia (AML). Multiple studies showed that the presence of NPM1 mutations associated with better outcome in patients with AML. Studies reported to date have analyzed leukemic cells obtained from bone marrow or peripheral blood. We tested for mutations in the NPM1 gene using peripheral blood plasma and compared results with clinical outcome from a single institution. Analyzing plasma from 98 newly diagnosed patient with AML showed NPM1 mutation in 24 (23%) of patient while only one (4%) of 28 previously untreated patients with myelodysplastic syndrome (MDS) showed NPM1 mutation. Compared with peripheral blood cells, 2 (8%) of the 24 positive patients were negative by cells; none were positive by cells and negative by plasma. Most of the mutations detected (45%) were in patients with FAB classification M2, M4 and M5. In addition to the reported 4 bp insertion, we also detected 4 bp deletion in one patient in cells and plasma. Patients with NPM1 mutation had a significantly higher white blood cell count (P = 0.0009) and a higher blast count in peripheral blood (P = 0.002) and in bone marrow (P = 0.002). Blasts in patients with NPM1 mutant expressed lower levels of HLA-DR (P = 0.005), CD13 (P = 0.02) and CD34 (P < 0.0001), but higher CD33 levels (P = 0.0004). Patients with NPM1 mutation appear to have better chance of responding to standard therapy (P = 0.06). Event free survival of patients with NPM1 mutation was longer (P = 0.056) than in patients with intermediate cytogenetic abnormalities. The most striking difference in survival was in patients who required >35 days to respond to therapy (Figure). Survival was significantly longer in patients with NPM1 mutation requiring >35 days to respond (P = 0.027). This data not only support that NPM1 plays a significant role in the biology and clinical behavior of AML, but also show that plasma DNA is enriched with leukemia-specific DNA and is a reliable source for testing. Figure Figure

Characterization of Extramedullary Acute Myeloid Leukemia – Results of the AML96 Trial

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2154-2154
Author(s):  
Friedrich Stölzel ◽  
Christoph Röllig ◽  
Michael Kramer ◽  
Brigitte Mohr ◽  
Uta Oelschlägel ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Acute Myeloid Leukemia ◽  
Induction Chemotherapy ◽  
Myeloid Leukemia ◽  
The Body ◽  
Hematopoietic Stem ◽  
Npm1 Mutation ◽  
Mutation Status ◽  
The Impact ◽  
Acute Myeloid

Abstract Abstract 2154 Background: Myeloid Sarcoma (MS) is defined as an extramedullary mass composed of myeloid blasts occurring at an anatomical site other than the bone marrow. Furthermore, the term extramedullary manifestation (EM) is applied if it accompanies overt acute myeloid leukemia (AML) and represents non-effacing tissue infiltration. EM is reported to correspond often to the skin but can affect almost every site of the body. The prognosis of MS or EM has been discussed controversially in the past. EM at diagnosis of AML is generally thought to be a rare event. However, data defining the prevalence of EM at diagnosis of AML and its prognostic value are missing. The aim of this analysis was to provide data for estimating the prevalence of EM at diagnosis of AML and to determine its relevance by including clinical and laboratory data from patients being treated in the prospective AML96 trial of the Study Alliance Leukemia (SAL) study group. Patients and Methods: A total of 326 patients with AML (age 17 – 83 years) and EM were treated within the AML96 trial with a median follow up of 8.8 years (95% CI, 8.4 to 9.3 years). All patients received double induction chemotherapy. Consolidation therapy contained high-dose cytosine arabinoside and for patients ≤ 60 years of age the option of autologous or allogeneic hematopoietic stem cell transplantation (HSCT). Logistic regression analyses were used to identify prognostic variables for CR rates. The method of Kaplan-Meier was used to estimate OS and EFS. Confidence interval (CI) estimation for the survival curves was based on the cumulative hazard function using the Greenwood's formula for the SE estimation. Survival distributions were compared using the log rank test. Results: 17% of the AML patients entered into the AML96 trial were diagnosed with EM. In 313 of the 326 patients (96%) EM was evident at diagnosis. The majority of patients with EM were diagnosed with de novo AML (84%, n=273), whereas gingival infiltration (51%, n=166) displayed the main EM of AML with CNS involvement being less common (4%, n=14). The majority of patients had a cytogenetic intermediate risk profile (71%, n=221) with a total of 172 patients (56%) harboring a normal karyotype. Patients with EM had a statistically significant lower median CD34-positivity of bone marrow blasts, higher percentage of FAB subtypes M4 and M5, higher WBC counts and LDH at diagnosis and higher percentage of NPM1 mutations compared to those patients without EM (all p<.001). When comparing achievement of CR between patients with EM to patients without EM, no statistical difference between these two groups was observed. Analysis according to the NPM1/FLT3-ITD mutation status revealed highest 5-year-OS (37%, 95% CI: .24 - .508) and 5-year-EFS (36%, 95% CI: .224 - .448) in the NPM1-mut/FLT3-wt group and lowest 5-year-OS (12%, 95% CI: 0 - .261) and 5-year-EFS (4%, 95% CI: 0 - .124) in the NPM1-wt/FLT3-ITD group, p=.007 and p=.001, respectively. Of the 49 relapsed patients with EM who had a NPM1-mutation at diagnosis 48 deceased despite of intensified relapse therapies. Conclusions: This analysis represents the largest study so far investigating the impact of EM AML. Patients with EM AML have distinct differences from AML patients without EM regarding their clinical and molecular characteristics at diagnosis. However these differences do not translate into differences in response to induction chemotherapy. Compared to patients without EM, survival analysis revealed differences according to the NPM1/FLT3-ITD mutation status which is also described for patients without EM AML. However, the prognosis for patients with EM who harbor a mutated NPM1 the prognosis at relapse seems to be dismal. Disclosures: No relevant conflicts of interest to declare.

5-Azacitidine In Patients with Myelodysplasia and Acute Myeloid Leukemia: a Single Centre Experience

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 4969-4969 ◽  
Author(s):  
Capodanno Isabella ◽  
Paolo Avanzini ◽  
Francesco Merli
Keyword(s):  
Bone Marrow ◽  
Overall Survival ◽  
Acute Myeloid Leukemia ◽  
Myeloid Leukemia ◽  
Progression Free Survival ◽  
Median Number ◽  
Study Population ◽  
Blast Count ◽  
Acute Myeloid

Abstract Abstract 4969 Introduction Hypomethylating agents have recently been shown to prolong overall survival and improve quality of life in patients with INT-2 and high IPSS risk myelodysplasia (MDS) and low bone marrow blast count acute myeloid leukemia (AML). Patients and Methods Since September 2008 we have been treating 26 patients affected by acute myeloid leukemia (13 patients), MDS (11 patients) or chronic myelomonocytic leukemia (2 patients) with 5-azacitidine. According to recent guidelines, most of myelodysplastic patients eligible for treatment belonged to the IPSS INT-2 or high risk groups. Patients with acute myeloid leukemia had a medullary blast count of 20–30%, except for four cases. Patients with chronic myelomonocytic leukemia had a medullary blast count > 10% and < 20%. The median age of patients when treatment was started was 69,5 years (range: 51–82). Azacitidine was administered subcutaneously (75 mg/m2/d) for 7 days of every 28-day cycle until loss of response or disease progression. Patients received a median number of 5,5 cycles of therapy (range 1–24). We evaluated overall improvement (CR + PR+ HI), the best response obtained and adverse events in the overall study population, according to International Working Group MDS and LMA criteria. In the subgroup of patients who received at least 6 cycles of therapy (10 patients) we also evaluated overall survival (OS) and progression free survival (PFS). Results The results of 5-azacitidine therapy in our cohort of patients are described in Table 1. In the AML cohort, after a median number of 4 cycles (range 1–10), we observed a hematological improvement (HI) in 15% of the patients, a stable disease (SD) in 31% of patients and a lack of response in 38% of patients. In the MDS cohort, after a median number of 7 cycles (range 2–24), we observed a complete response (CR) (including a cytogenetic response) in 36.5% of patients, a partial response (PR) in 9% of patients, a hematological improvement in 45.5% of patients and a stable disease in 18% of patients. The overall improvement (CR + PR + HI) was 15% in the AML cohort and 91% in the MDS cohort. In the LMMC cohort, after a median number of 2.5 cycles (range 1–4), we observed a hematological improvement in 50% of the patients. In the subgroup of patients who received at least six cycles of therapy, the overall survival was 11.5 months and the progression free survival was 9 months. In the overall study population, two patients (8%) discontinued treatment as a result of adverse events. In four non-responder patients (15%) death was due to a rapid progression of disease. Discussion In this analysis we have reported good response rates in MDS patients, with 36.5% of complete response (including a complete cytogenetic response). No CR or PR were observed in AML patients; however, in this subgroup of patients the median follow-up was short (median number of cycles of therapy: four). Furthermore, in these patients even a stable disease with no need of hospitalization and a good quality of life can be considered an important result. Due to the short period of follow-up, 57.5% of our patients received fewer than 6 cycles of 5-azacitidine and their therapy is still ongoing. Conclusions The limited number of cases and the short period of follow-up did not allow us to evaluate overall survival and progression free survival in the overall study population. We will update these data as time progresses. We reported these data in the subgroup of patients who received at least six cycles of therapy. According to current evidence, we observed that 5-azacitidine plays an important role in the treatment of patients with MDS (both with high- and low-IPSS risk) and low bone marrow blast counts AML. In these subgroups of patients, 5-azacitidine prolongs survival and is well tolerated. In our limited experience, this drug had no efficacy when a higher degree of bone marrow blasts (> 30%) was present. Further trials should assess the number of cycles required for treatment, the role of hypometilating agents in low-risk MDS and in patients with AML and a bone marrow blasts counts > 30%. Disclosures: No relevant conflict of interest to declare. Disclosures: No relevant conflicts of interest to declare.

Inhibition of HDAC8 Reactivates p53 and Abrogates Leukemia Stem Cell Activity in CBFβ-SMMHC Associated Acute Myeloid Leukemia

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 363-363
Author(s):  
Jing Qi ◽  
Qi Cai ◽  
Sandeep Singh ◽  
Ling Li ◽  
Hongjun Liu ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Acute Myeloid Leukemia ◽  
Myeloid Leukemia ◽  
Bone Marrow Cells ◽  
Conflicts Of Interest ◽  
Cell Activity ◽  
Disease Free Survival ◽  
Hematopoietic Stem ◽  
The Impact ◽  
Acute Myeloid

Abstract The inv(16)-created CBFβ-SMMHC fusion protein inhibits differentiation of hematopoietic stem and progenitor cells (HSPCs) and creates pre-leukemic populations predisposed to acute myeloid leukemia (AML) transformation. However, the molecular mechanism underlying the leukemogenic function of CBFβ-SMMHC has been elusive. Given the low TP53 mutation rate in AML, alternative mechanisms disrupting p53 function are expected. We showed thatCBFβ-SMMHC impairs p53 acetylation and p53 target gene activation through formation of an aberrant protein complex with p53 and HDAC8 (Blood, 120: A772; 122(21): 224). We now show that CBFβ-SMMHC binds to p53 and HDAC8 independently through distinct regions and that HDAC8 mediates the deacetylation of p53 associated with CBFβ-SMMHC. In addition, we generated mice carrying a floxed Hdac8 (Hdac8f) allele and crossed with Cbfb56M/+/Mx1-Cre (Kuo YH et al, Cancer Cell 2006). Deletion of Hdac8 signifiacntly (p<0.0001) reduced the incidence of AML and prolonged disease-free survival. Pharmacologic inhibition of HDAC8 activity with HDAC8-selective inhibitors (HDAC8i) reactivates p53 and selectively induces apoptosis of inv(16)+ AML CD34+ cells while sparing normal HSPCs. To test the effect of HDAC8i on LSC engraftment and leukemia-initiating capacity, we generated Cbfb56M/+/Mx1-Cre mice with a Cre-reporter line expressing tdTomato fluorescence protein following Cre-mediated recombination. AML cells (dTomato+/cKit+) treated with HDAC8i (22d) ex vivo showed reduced engraftment (p=0.025) and enhanced survival (p=0.025) in transplanted mice. To examine whether HDAC8i 22d treatment affects the engraftment capacity on surviving cells, we transplanted equal number (2 x 106) of AML cells treated with either 22d or vehicle in another cohort of mice (n=4). We show that HDAC8i 22d treatment reduced the engraftment of dTomato+/cKit+ AML cells and enhanced survival, suggesting that the engraftment capacity is altered in addition to reducing AML cell survival. We next performed preclinical studies to determine the efficacy of in vivo administration of HDAC8i 22d. AML transplanted mice were randomized into two groups, one group treated with vehicle and the other treated with HDAC8i 22d for 2 weeks. Flow cytometry analysis revealed significantly reduced frequency (p=0.0097) and number (p=0.0101) of dTomato+/cKit+ AML cells in the bone marrow and spleen of 22d treated mice compared to vehicle treated group. To further assess the impact on LSC activity, we transplanted bone marrow cells from these treated mice into secondary recipients and analyzed for AML engraftment. Significant reduction in the frequency (p<0.0001) and the number (p=0.0006) of dTomato+/cKit+ AML cells was observed in the bone marrow and spleen. Furthermore, HDAC8i 22d treated transplants showed no signs of leukemia while vehicle treated transplants are moribund with aggressive AML. These results indicate that HDAC8 inhibition by 22d treatment effectively eliminates engraftment and leukemia-initiating capacity of AML LSCs. In conclusion, our studies identify a novel post-translational p53-inactivating mechanism and demonstrate selective HDAC8 inhibition as a promising approach to target inv(16)+ AML LSCs. Disclosures No relevant conflicts of interest to declare.

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