Bromodomain and extraterminal domain (BET) inhibitors are promising epigenetic agents for the treatment of various subsets of acute myeloid leukemia (AML). However, the resistance of leukemia stem cells (LSC) to BET inhibitors remains a major challenge. In this study, we evaluated the mechanisms underlying LSC resistance to the BET inhibitor JQ1. We evaluated the levels of apoptosis and autophagy induced by JQ1 in LSC-like leukemia cell lines and primary CD34CD38 leukemic blasts obtained from AML cases with normal karyotype without recurrent mutations. JQ1 effectively induced apoptosis in a concentration-dependent manner in JQ1-sensitive AML cells. However, in JQ1-resistant AML LSCs, JQ1 induced little apoptosis and led to upregulation of beclin-1, increased LC3-II lipidation, formation of autophagosomes, and downregulation of p62/SQSTM1. Inhibition of autophagy by pharmacologic inhibitors or knockdown of beclin-1 using specific siRNA enhanced JQ1-induced apoptosis in resistant cells, indicating that prosurvival autophagy occurred in these cells. Independent of mTOR signaling, activation of the AMPK (pThr172)/ULK1 (pSer555) pathway was found to be associated with JQ1-induced autophagy in resistant cells. AMPK inhibition using the pharmacologic inhibitor compound C or by knockdown of AMPKα suppressed autophagy and promoted JQ1-induced apoptosis in AML LSCs. These findings revealed that prosurvival autophagy was one of the mechanisms involved in the resistance AML LSCs to JQ1. Targeting the AMPK/ULK1 pathway or inhibition of autophagy could be an effective therapeutic strategy for combating resistance to BET inhibitors in AML and other types of cancer. .

Paroxysmal nocturnal hemoglobinuria (PNH) is a progressive, systemic, life-threatening disease, characterized by chronic uncontrolled complement activation. A retrospective analysis of 301 Korean PNH patients who had not received eculizumab was performed to systematically identify the clinical symptoms and signs predictive of mortality. PNH patients with hemolysis (lactate dehydrogenase [LDH] ≥ 1.5 × the upper limit of normal [ULN]) have a 4.8-fold higher mortality rate compared with the age- and sex-matched general population (P < 0.001). In contrast, patients with LDH < 1.5 × ULN have a similar mortality rate as the general population (P = 0.824). Thromboembolism (TE) (odds ratio [OR] 7.11; 95% confidence interval [CI] (3.052-16.562), renal impairment (OR, 2.953; 95% CI, 1.116-7.818) and PNH-cytopenia (OR, 2.547; 95% CI, 1.159-5.597) are independent risk factors for mortality, with mortality rates 14-fold (P < 0.001), 8-fold (P < 0.001), and 6.2-fold (P < 0.001) greater than that of the age- and sex-matched general population, respectively. The combination of hemolysis and 1 or more of the clinical symptoms such as abdominal pain, chest pain, or dyspnea, resulted in a much greater increased mortality rate when compared with patients with just the individual symptom alone or just hemolysis. Early identification of risk factors related to mortality is crucial for the management of PNH. This trial was registered at www.clinicaltrials.gov as NCT01224483.

Early cytomegalovirus (CMV) replication (eCMV) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) has been suggested as an independent factor that reduces leukemia relapse risk. We retrospectively analyzed 74 patients with acute myeloid leukemia (AML) who underwent allo-HSCT between August 2006 and September 2012. All recipients were CMV seropositive. In 52 patients, eCMV occurred at a median of 35 days (range, 11-92) after allo-HSCT. Univariate analysis revealed that the factors associated with a reduction in the 5-year cumulative incidence of relapse (CIR) included the first complete remission status at allo-HSCT, non-adverse cytogenetics and molecular abnormalities, pre-transplant serum ferritin level <1,400 mg/dL, chronic graft-versus-host disease (cGVHD), and eCMV. In sub-group analysis, according to the existence of eCMV and cGVHD, those with both eCMV and cGVHD showed the lowest 5-year CIR (P < 0.003). Patients with both eCMV and cGVHD had the best outcome for leukemia-free survival (LFS) (P < 0.001) and OS (P < 0.001). In the CMV-seropositive population, the presence of eCMV in combination with cGVHD had a significant positive effect on LFS and OS after allo-HSCT. When eCMV preceded cGVHD, the relapse rate after allo-HSCT was significantly reduced in patients with AML. Therefore, we suggest that it is critical to have an immunological understanding of the graft-versus-leukemia effect in this setting.

Bromodomain and extraterminal domain (BET) inhibitors are promising epigenetic agents for the treatment of various subsets of acute myeloid leukemia (AML). However, the resistance of leukemia stem cells (LSCs) to BET inhibitors remains a major challenge. In this study, we evaluated the mechanisms underlying LSC resistance to the BET inhibitor JQ1. We evaluated the levels of apoptosis and macroautophagy/autophagy induced by JQ1 in LSC-like leukemia cell lines and primary CD34 C CD38 ¡ leukemic blasts obtained from AML cases with normal karyotype without recurrent mutations. JQ1 effectively induced apoptosis in a concentration-dependent manner in JQ1-sensitive AML cells. However, in JQ1-resistant AML LSCs, JQ1 induced little apoptosis and led to upregulation of BECN1/Beclin 1, increased LC3 lipidation, formation of autophagosomes, and downregulation of SQSTM1/p62. Inhibition of autophagy by pharmacological inhibitors or knockdown of BECN1 using specific siRNA enhanced JQ1-induced apoptosis in resistant cells, indicating that prosurvival autophagy occurred in these cells. Independent of MTOR signaling, activation of the AMPK (p-Thr172)-ULK1 (p-Ser555) pathway was found to be associated with JQ1-induced autophagy in resistant cells. AMPK inhibition using the pharmacological inhibitor compound C or by knockdown of PRKAA/AMPKa suppressed autophagy and promoted JQ1-induced apoptosis in AML LSCs. These findings revealed that prosurvival autophagy was one of the mechanisms involved in the resistance of AML LSCs to JQ1. Targeting the AMPK-ULK1 pathway or inhibition of autophagy could be an effective therapeutic strategy for combating resistance to BET inhibitors in AML and other types of cancer.KEYWORDS AMPK-ULK1; autophagy; BET inhibitor; leukemia stem cells; resistanceDespite advances in our understanding of the molecular pathogenesis of acute myeloid leukemia (AML), the prognosis remains poor, primarily because of high relapse rates. Cytotoxic therapy has shown limited effectiveness in eradicating the functionally distinct leukemia stem cells (LSCs), which may contribute to chemotherapy resistance and relapse. Therefore, novel treatment strategies with acceptable toxicity that target LSCs are urgently needed to improve therapeutic outcomes for patients with AML. BRD4 (bromodomain containing 4), a member of the bromodomain and extraterminal domain (BET) family, is a chromatin reader that preferentially localizes to "super-enhancer" regions upstream of a variety of oncogenes, including MYC/cMyc, to regulate their expression. BRD4 inhibition may be an effective alternative strategy for targeting MYC, which is considered undruggable and deregulated in many human cancers. Selective inhibitors of BET, such as JQ1, are promising epigenetic agents for the treatment of various tumor types, including AML and LSCs.Although leukemia cells appear to have differences in apoptotic responses to JQ1 and this cannot be explained by changes in the levels of MYC and BRD4, our knowledge of the molecular mechanisms underlying resist...