m6A-dependent upregulation of DDX21 by super-enhancer-driven IGF2BP2 and IGF2BP3 facilitates progression of acute myeloid leukaemia.

BACKGROUND: Acute myeloid leukaemia (AML) is a haematological malignancy with unfavourable prognosis. Despite the effectiveness of chemotherapy and targeted therapy, relapse or drug resistance remains a major threat to AML patients. N6-methyladenosine (m6A) RNA methylation and super-enhancers (SEs) are extensively involved in the leukaemogenesis of AML. However, the potential relationship between m6A and SEs in AML has not been elaborated. METHODS: Chromatin immunoprecipitation (ChIP) sequencing data from Gene Expression Omnibus (GEO) cohort were analysed to search SE-related genes. The mechanisms of m6 A-binding proteins IGF2BP2 and IGF2BP3 on DDX21 were explored via methylated RNA immunoprecipitation (MeRIP) assays, RNA immunoprecipitation (RIP) assays and luciferase reporter assays. Then we elucidated the roles of DDX21 in AML through functional assays in vitro and in vivo. Finally, co-immunoprecipitation (Co-IP) assays, RNA sequencing and ChIP assays were performed to investigate the downstream mechanisms of DDX21. RESULTS: We identified two SE-associated transcripts IGF2BP2 and IGF2BP3 in AML. High enrichment of H3K27ac, H3K4me1 and BRD4 was observed in IGF2BP2 and IGF2BP3, whose expression were driven by SE machinery. Then IGF2BP2 and IGF2BP3 enhanced the stability of DDX21 mRNA in an m6A-dependent manner. DDX21 was highly expressed in AML patients, which indicated a poor survival. Functionally, knockdown of DDX21 inhibited cell proliferation, promoted cell apoptosis and led to cell cycle arrest. Mechanistically, DDX21 recruited transcription factor YBX1 to cooperatively trigger ULK1 expression. Moreover, silencing of ULK1 could reverse the promoting effects of DDX21 overexpression in AML cells. CONCLUSIONS: Dysregulation of SE-IGF2BP2/IGF2BP3-DDX21 axis facilitated the progression of AML. Our findings provide new insights into the link between SEs and m6A modification, elucidate the regulatory mechanisms of IGF2BP2 and IGF2BP3 on DDX21, and reveal the underlying roles of DDX21 in AML.

High expression of BCAT1 sensitizes AML cells to PARP inhibitor by suppressing DNA damage response.

Previous evidence has confirmed that branched-chain aminotransferase-1 (BCAT1), a key enzyme governing branched-chain amino acid (BCAA) metabolism, has a role in cancer aggression partly by restricting αKG levels and inhibiting the activities of the αKG-dependent enzyme family. The oncogenic role of BCAT1, however, was not fully elucidated in acute myeloid leukemia (AML). In this study, we investigated the clinical significance and biological insight of BCAT1 in AML. Using q-PCR, we analyzed BCAT1 mRNAs in bone marrow samples from 332 patients with newly diagnosed AML. High BCAT1 expression independently predicts poor prognosis in patients with AML. We also established BCAT1 knockout (KO)/over-expressing (OE) AML cell lines to explore the underlying mechanisms. We found that BCAT1 affects cell proliferation and modulates cell cycle, cell apoptosis, and DNA damage/repair process. Additionally, we demonstrated that BCAT1 regulates histone methylation by reducing intracellular αKG levels in AML cells. Moreover, high expression of BCAT1 enhances the sensitivity of AML cells to the Poly (ADP-ribose) polymerase (PARP) inhibitor both in vivo and in vitro. Our study has demonstrated that BCAT1 expression can serve as a reliable predictor for AML patients, and PARP inhibitor BMN673 can be used as an effective treatment strategy for patients with high BCAT1 expression. KEY MESSAGES: High expression of BCAT1 is an independent risk factor for poor prognosis in patients with CN-AML. High BCAT1 expression in AML limits intracellular αKG levels, impairs αKG-dependent histone demethylase activity, and upregulates H3K9me3 levels. H3K9me3 inhibits ATM expression and blocks cellular DNA damage repair process. Increased sensitivity of BCAT1 high expression AML to PARP inhibitors may be used as an effective treatment strategy in AML patients.

Quercetin improves cerebral ischemia/reperfusion injury by promoting microglia/macrophages M2 polarization via regulating PI3K/Akt/NF-κB signaling pathway.

The modulation of microglial polarization from the pro-inflammatory M1 to the anti-inflammatory M2 phenotype shows promise as a therapeutic strategy for ischemic stroke. Quercetin, a natural flavonoid abundant in various plants, possesses anti-inflammatory, anti-apoptotic, and antioxidant properties. Nevertheless, its effect and underlying mechanism on microglia/macrophages M1/M2 polarization in the treatment of cerebral ischemia/reperfusion injury (CI/RI) remain poorly explored. In the current study, we observed that quercetin ameliorated neurological deficits, reduced infarct volume, decreased the number of M1 microglia/macrophages (CD16/32+/Iba1+), and enhanced the number of M2 microglia/macrophages (CD206+/Iba1+) after establishing the CI/RI model in rats. Subsequent in vivo and in vitro experiments indicated that quercetin downregulated M1 markers (CD86, iNOS, TNF-α, IL-1ß, and IL-6) and upregulated M2 markers (CD206, Arg-1, IL-10, and TGF-ß). Network pharmacology analysis and molecular docking revealed that the PI3K/Akt/NF-κB signaling pathway emerged as the core pathway. Western blot confirmed that quercetin upregulated the phosphorylation of PI3K and Akt, while alleviating the phosphorylation of IκBα and NF-κB both in vivo and in vitro. However, the PI3K inhibitor LY294002 reversed the effects of quercetin on M2 polarization and the expression of key proteins in the PI3K/Akt/NF-κB pathway in primary microglia after oxygen-glucose deprivation/reoxygenation (OGD/R) in vitro. Collectively, our findings demonstrate that quercetin facilitates microglia/macrophages M2 polarization by modulating the PI3K/Akt/NF-κB signaling pathway in the treatment of CI/RI. These findings provide novel insights into the therapeutic mechanisms of quercetin in ischemic stroke.

circSLC25A13 acts as a ceRNA to regulate AML progression via miR-616-3p/ADCY2 axis.

Circular RNAs (circRNAs), a type of endogenous noncoding RNA (ncRNA), exert vital roles in leukemia progression and are promising prognostic factors. Here, we report a novel circRNA, circSLC25A13 (hsa_circ_0081188), which was increased in acute myeloid leukemia (AML) patients with poor overall survival (OS) comparing to patients with good prognosis. Knockdown of circSLC25A13 in AML cells inhibited proliferation and increased cell apoptosis in vitro and in vivo. Enhanced circSLC25A13 expression promoted the survival of AML cells. Mechanistically, circSLC25A13 played as a microRNA sponge of miR-616-3p, which inhibited the expression of adenylate cyclase 2 (ADCY2). Downregulation of miR-616-3p and overexpression of ADCY2 partially rescued circSLC25A13 deficient induced cell growth arrest. In summary, through competitive absorption of miR-616-3p and thereby upregulating ADCY2 expression, circSLC25A13 promoted AML progression. Moreover, circSLC25A13 may represent a potential novel biomarker for the prognosis of AML and offer a potential therapeutic target for AML treatment.

Glutamate dehydrogenase 1: A novel metabolic target in inhibiting acute myeloid leukaemia progression.

Glutamine metabolic reprogramming in acute myeloid leukaemia (AML) cells contributes to the decreased sensitivity to antileukemic drugs. Leukaemic cells, but not their myeloid counterparts, largely depend on glutamine. Glutamate dehydrogenase 1 (GDH1) is a regulation enzyme in glutaminolysis. However, its role in AML remains unknown. Here, we reported that GDH1 was highly expressed in AML: high GDH1 was one of the independent negative prognostic factors in AML cohort. The dependence of leukaemic cells on GDH1 was proved both in vitro and in vivo. High GDH1 promoted cell proliferation and reduced survival time of leukaemic mice. Targeting GDH1 eliminated the blast cells and delayed AML progression. Mechanistically, GDH1 knockdown inhibited glutamine uptake by downregulating SLC1A5. Moreover, GDH1 invalidation also inhibited SLC3A2 and abrogated the cystine-glutamate antiporter system Xc- . The reduced cystine and glutamine disrupted the synthesis of glutathione (GSH) and led to the dysfunction of glutathione peroxidase-4 (GPX4), which maintains the lipid peroxidation homeostasis by using GSH as a co-factor. Collectively, triggering ferroptosis in AML cells in a GSH depletion manner, GDH1 inhibition was synthetically lethal with the chemotherapy drug cytarabine. Ferroptosis induced by inhibiting GDH1 provides an actionable therapeutic opportunity and a unique target for synthetic lethality to facilitate the elimination of malignant AML cells.

CPT1B, a metabolic molecule, is also an independent risk factor in CN-AML.

BACKGROUND: Fatty acid oxidation has been considered as an important energy source for tumorigenesis and development. Several studies have investigated the role of CPT1A, a kind of fatty acid oxidation rate-limiting enzyme, in AML. However, prognostic value and regulatory network of another subtype, CPT1B in AML remains elusive. This study aims to clarify the independent prognostic role of CPT1B in CN-AML based on clinical data and molecular level data (mRNA, miRNA and lncRNA). OBJECTIVE: The aim of this study is to investigate the prognostic value of CPT1B in AML patients. METHODS: First, we analyzed the CPT1B expression in AML cohort via the online database "GEPIA". Subsequently, miRNA-mRNA and ceRNA networks were constructed to help predict the role of CPT1B in AML. Several molecules which showed the prognostic value and metabolic function of CPT1B were identified. Finally, the expression of CPT1B in our own cohort of 324 CN-AML patients was analyzed to clarify the results. RESULTS: It was found that CPT1B was markedly higher in AML patients compared to normal people and this upregulation was associated with the poor clinical outcome. Several molecules revealed the possible regulatory mechanism of CPT1B in AML. CONCLUSION: CPT1B is a potential prognostic factor and a therapeutic target for AML treatment.

Spermatogenesis associated serine rich 2 like plays a prognostic factor and therapeutic target in acute myeloid leukemia by regulating the JAK2/STAT3/STAT5 axis.

BACKGROUND: Spermatogenesis associated serine rich 2 like (SPATS2L) was highly expressed in homoharringtonine (HHT) resistant acute myeloid leukemia (AML) cell lines. However, its role is little known in AML. The present study aimed to investigate the function of SPATS2L in AML pathogenesis and elucidate the underlying molecular mechanisms. METHODS: Overall survival (OS), event-free survival (EFS), relapse-free survival (RFS) were used to evaluate the prognostic impact of SPATS2L for AML from TCGA database and ourcohort. ShRNA was used to knockdown the expression of SPATS2L. Apoptosis was assessed by flow cytometry. The changes of proteins were assessed by Western blot(WB). A xenotransplantation mice model was used to evaluate in vivo growth and survival. RNA sequencing was performed to elucidate the molecular mechanisms underlying the role of SPATS2L in AML. RESULTS: SPATS2L expression increased with increasing resistance indexes(RI) in HHT-resistant cell lines we had constructed. Higher SPATS2L expression was observed in intermediate/high-risk patients than in favorable patients. Meanwhile, decreased SPATS2L expression was observed in AML patients achieving complete remission (CR). Multivariate analysis showed high SPATS2L expression was an independent poor predictor of OS, EFS, RFS in AML. SPATS2L knock down (KD) suppressed cell growth, induced apoptosis, and suppressed key proteins of JAK/STAT pathway, such as JAK2, STAT3, STAT5 in AML cells. Inhibiting SPATS2L expression markedly enhanced the pro-apoptotic effects of traditional chemotherapeutics (Ara-c, IDA, and HHT). CONCLUSIONS: High expression of SPATS2L is a poor prognostic factor in AML, and targeting SPATS2L may be a promising therapeutic strategy for AML patients.

FLOT1 knockdown inhibits growth of AML cells through triggering apoptosis and pyroptosis.

Acute myeloid leukemia (AML) is a group of hematological malignancies characterized by clonal proliferation of immature myeloid cells. Lipid rafts are highly organized membrane subdomains enriched in cholesterol, sphingolipids, and gangliosides and play roles in regulating apoptosis through subcellular redistribution. Flotillin1 (FLOT1) is a component and also a marker of lipid rafts and had been reported to be involved in the progression of cancers and played important roles in cell death. However, the role of FLOT1 in AML remains to be explored. In this study, we found that increased expression of FLOT1 was correlated with poor clinical outcome in AML patients. Knockdown of FLOT1 in AML cells not only promoted cell death in vitro but also inhibited malignant cells engraftment in vivo. Mechanically, FLOT1 knockdown triggered apoptosis and pyroptosis. FLOT1 overexpression promoted AML cell growth and apoptosis resistance. Our findings indicate that FLOT1 is a prognostic factor of AML and may be a potential target for AML treatment.

Dihydropyrimidinase-like 2 can serve as a novel therapeutic target and prognostic biomarker in acute myeloid leukemia.

BACKGROUND: Identifying therapeutic targets and prognostic biomarkers significantly contributes to individualized treatment of acute myeloid leukemia (AML). Dihydropyrimidinase-like 2 (DPYSL2) expression was decreased in homoharringtonine (HHT)-resistant AML cells, which were established by our group. DPYSL2 plays an important role in axon growth and has oncogene effect in glioblastoma. However, little research has been conducted to investigate the function of DPYSL2 in AML pathogenesis. METHODS: Auto-docking was used to reveal the targeting relationship between HHT and DPYSL2. Overall survival (OS), event-free survival (EFS), and relapse-free survival (RFS) were used to evaluate the prognostic impact of DPYSL2 for AML. ShRNA was used to knockdown the expression of SPATS2L. Apoptosis was assessed by flow cytometry. In vivo growth and survival were assessed using a xenotransplantation mice model. RNA sequencing was performed to elucidate the molecular mechanisms underlying the role of SPATS2L in AML and were confirmed by Western blot. RESULTS: We found DPYSL2 was the target of HHT. Next, we found AML cell lines and patients had higher DPYSL2 expression levels than the normal samples. Further multivariate analysis demonstrated that high DPYSL2 expression was an independent poor prognostic factor for OS, EFS, and RFS in AML. Inhibition of DPYSL2 expression suppressed cell growth, induced apoptosis in AML cell lines, and prolonged the survival of AML xenograft NCG mice. Through RNA-seq analysis from TCGA and our data, the JAK2/STAT3/STAT5-PI3K P85/AKT/GSK3b axis was thought to be the critical pathway in regulating DPYSL2 in AML development. CONCLUSIONS: We first time confirmed that DPYSL2 was a target of HHT and played an oncogene role in AML by regulating JAK/STAT signaling pathway. Therefore, DPYSL2 could serve as a novel prognostic marker and therapeutic target for AML treatment.

ACC010, a novel BRD4 inhibitor, synergized with homoharringtonine in acute myeloid leukemia with FLT3-ITD.

Bromodomain-containing protein 4 (BRD4) inhibitors have been clinically developed to treat acute myeloid leukemia (AML), but their application is limited by the possibility of drug resistance, which is reportedly associated with the activation of the WNT/ß-catenin pathway. Meanwhile, homoharringtonine (HHT), a classic antileukemia drug, possibly inhibits the WNT/ß-catenin pathway. In this study, we attempted to combine a novel BRD4 inhibitor (ACC010) and HHT to explore their synergistic lethal effects in treating AML. Here, we found that co-treatment with ACC010 and HHT synergistically inhibited cell proliferation, induced apoptosis, and arrested the cell cycle in FMS-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD)-positive AML cells in vitro, and significantly inhibiting AML progression in vivo. Mechanistically, ACC010 and HHT cooperatively downregulated MYC and inhibited FLT3 activation. Further, when HHT was added, ACC010-resistant cells demonstrated a good synergy. We also extended our study to the mouse BaF3 cell line with FLT3-inhibitor-resistant FLT3-ITD/tyrosine kinase domain mutations and AML cells without FLT3-ITD. Collectively, our results suggested that the combination treatment of ACC010 and HHT might be a promising strategy for AML patients, especially those carrying FLT3-ITD.

Homoharringtonine is synergistically lethal with BCL-2 inhibitor APG-2575 in acute myeloid leukemia.

BACKGROUND: Despite advances in targeted agent development, effective treatment of acute myeloid leukemia (AML) remains a major clinical challenge. The B-cell lymphoma-2 (BCL-2) inhibitor exhibited promising clinical activity in AML, acute lymphoblastic leukemia (ALL) and diffuse large B-cell lymphoma (DLBCL) treatment. APG-2575 is a novel BCL-2 selective inhibitor, which has demonstrated anti-tumor activity in hematologic malignancies. Homoharringtonine (HHT), an alkaloid, exhibited anti-AML activity. METHODS: The synergistic effects of APG-2575 and HHT were studied in AML cell lines and primary samples. MTS was used to measure the cell viability. Annexin V/propidium iodide staining was used to measure the apoptosis rate by flow cytometry. AML cell xenografted mouse models were established to evaluate the anti-leukemic effect of BCL-2 inhibitor, HHT and their combination in vivo. Western blot was used to determine the expression of related proteins. RESULTS: APG-2575 showed comparable anti-leukemic effect to the FDA-approved BCL-2 inhibitor ABT-199 in vitro and in vivo. Combined treatment of HHT with APG-2575 synergistically inhibited AML cell growth and engraftment. Mechanistically, HHT promoted degradation of myeloid cell leukemia-1 (MCL-1), which was reported to induce BCL-2 inhibitor resistant, through the PI3K/AKT/GSK3ß signaling pathway. CONCLUSION: Our results provide an effective AML treatment strategy through combination of APG-2575 and HHT, which is worthy of further clinical research.

Circular RNA LONP2 regulates proliferation, invasion, and apoptosis of bladder cancer cells by sponging microRNA-584-5p.

Bladder cancer (BC) is the most frequent type of urinary tumor and a barely treatable disease. Although extensive efforts have been invested in the research of BC, the underlying etiology and pathophysiology remain unclear. CircLONP2 is a circular RNA implicated in the development of many cancers, and miR-584-5p and YAP1 have been reported to contribute to the progression of BC. In this research, we presented novel evidence supporting circLONP2/miR-584-5p/YAP1 axis as a novel regulatory module in the progression of BC. We analyzed the expression of circLONP2 between precancerous BC samples and normal tissues using a published RNA-seq dataset. The expression of circLONP2 was also validated in clinical samples and cell lines by quantitative RT-PCR. Small interfering RNA (siRNA) and miRNA inhibitor was utilized to modulate the expression of circLONP2 and miR-584-5p and investigate their functions on cell proliferation and invasion. Luciferase reporter assay and RNA pull-down were performed to confirm the functional interactions among circLONP2/miR-584-5p/YAP1. CircLONP2 was significantly upregulated in precancerous BC tissues and BC cells. CircLONP2 depletion inhibited cell viability, proliferation, and invasion of BC cell lines, which could be partially rescued by miR-584-5p inhibitor. Further experiments indicated that miR-584-5p regulates cell viability, proliferation, and invasion via directly targeting YAP1. In summary, our work indicates that circLONP2 plays an oncogenic function in BC by regulating miR-584-5p/YAP1 axis, and its interaction with miR-584-5p provides a potential strategy to target BC.

MAP4K1 functions as a tumor promotor and drug mediator for AML via modulation of DNA damage/repair system and MAPK pathway.

BACKGROUND: Acute myeloid leukemia (AML) is a group of heterogeneous hematologic malignancies correlates with poor prognosis. It is important to identify biomarkers for effective treatment of AML. Kinases participate in many regulatory pathways and biological activities in AML. Previous studies demonstrated that MAP4K1, a serine/threonine kinase, was associated with immune regulation and cancer progression. However, its role and mechanism in acute myeloid leukemia (AML) have not been explored. METHODS: RNA-seq profiling was performed for Homoharringtonine (HHT)-resistant and Homoharringtonine (HHT)-sensitive cell lines. Bioinformatic tools were used for differential analysis. Cell culture and transfection, Cell proliferation, apoptosis and Cell cycle assay, Quantitative RT-PCR, and Western blotting analysis were used to explore biological phenotypes in vitro. FINDINGS: We found that MAP4K1 was highly expressed in HHT-induced resistant AML cell lines. In addition, overexpression of MAP4K1 in AML cells induced resistance of AML cells against HHT. Not only that, the findings of this study showed that overexpression of MAP4K1 was an independent risk factor that predicts poor prognosis of AML. Further, In vitro studies showed that MAP4K1 modulated cell cycle through MAPK and DNA damage/repair pathways. Therefore, MAP4K1 is a potential target for developing therapies for AML. INTERPRETATION: This study demonstrates that MAP4K1 not only regulates HHT resistance but also independently predicts AML prognosis. In addition, understanding the regulatory mechanism of MAP4K1 reveals novel treatment strategies for resistant and refractory AML. Fundings: This work was supported by the National Natural Science Foundation of China (NSFC) (Grant No.81800199, 81670124, 82070118) and the Natural Science Foundation of Zhejiang Province (LY20H080008).

Inhibition of CPT1a as a prognostic marker can synergistically enhance the antileukemic activity of ABT199.

BACKGROUND: Fatty acid oxidation (FAO) provides an important source of energy to promote the growth of leukemia cells. Carnitine palmitoyltransferase 1a(CPT1a), a rate-limiting enzyme of the essential step of FAO, can facilitate cancer metabolic adaptation. Previous reports demonstrated that CPT1a acts as a potential molecular target in solid tumors and hematologic disease. However, no systematic study was conducted to explore the prognostic value of CPT1a expression and possible treatment strategies with CPT1a inhibitor on acute myeloid leukemia (AML). METHODS: The expression of CPT1a in 325 cytogenetically normal AML (CN-AML) patients was evaluated using RT-PCR. The combination effects of ST1326 and ABT199 were studied in AML cells and primary patients. MTS was used to measure the cell proliferation rate. Annexin V/propidium iodide staining and flow cytometry analysis was used to measure the apoptosis rate. Western blot was used to measure the expression of Mcl-1. RNAseq and GC-TOFMS were used for genomic and metabolic analysis. RESULTS: In this study, we found AML patients with high CPT1a expression (n = 245) had a relatively short overall survival (P = 0.01) compared to patients in low expression group (n = 80). In parallel, downregulation of CPT1a inhibits proliferation of AML cells. We also conducted genomic and metabolic interactive analysis in AML patients, and found several essential genes and pathways related to aberrant expression of CPT1a. Moreover, we found downregulation of CPT1a sentitized BCL-2 inhibitor ABT199 and CPT1a-selective inhibitor ST1326 combined with ABT199 had a strong synergistic effect to induce apoptosis in AML cells and primary patient blasts for the first time. The underlying synergistic mechanism might be that ST1326 inhibits pGSK3ß and pERK expression, leading to downregulation of Mcl-1. CONCLUSION: Our study indicates that overexpression of CPT1a predicts poor clinical outcome in AML. CPT1a-selective inhibitor ST1326 combined with Bcl-2 inhibitor ABT199 showed strong synergistic inhibitory effects on AML.

Global, regional, and national burdens of leukemia from 1990 to 2017: a systematic analysis of the global burden of disease 2017 study.

We described the spatial and temporal trends of the annual leukemia incidence, prevalence, mortality, and disability-adjusted life years (DALYs) from 1990 to 2017. Leukemia case numbers and age-standardized rates (ASRs) were extracted from the Global Burden of Disease (GBD) study 2017. The estimated annual percentage change (EAPC) in the ASR was calculated using a generalized linear model with a Gaussian distribution. The risk factors for death and DALYs due to leukemia were estimated within the comparative risk assessment framework of the GBD study. Globally, the prevalence, age-standardized prevalence rate (ASPR), and EAPC in leukemia cases in 2017 were 2.43 (95% uncertainty interval (UI) 2.19 to 2.59) million, 32.26 (95% UI 29.02 to 34.61), and 0.22% (95% CI 0.13 to 0.31, P<0.01), respectively, during 1990-2017. The trends of the age-standardized incidence, deaths, and DALY rate all significantly decreased globally. The burden of leukemia was higher in males than in female. An increasing leukemia burden was found in high-middle-sociodemographic index (SDI) countries and territories. The burden of leukemia tended to be lower in high-SDI regions than that in lower SDI regions. The rapid increases in the prevalent cases and prevalence rate of leukemia is urgent to be solved in the future.

Ibrutinib Suppresses Early Megakaryopoiesis but Enhances Proplatelet Formation.

Ibrutinib, an irreversible inhibitor of Bruton's tyrosine kinase, has a favorable safety profile in patients with B cell-related malignancies. A primary adverse effect of ibrutinib is thrombocytopenia in the early stages of treatment, but platelet counts increase or recover as treatment continues. Currently, the effects of ibrutinib on megakaryopoiesis remain unclear. In this study, we investigated the mechanism by which ibrutinib induces thrombocytopenia using cord blood CD34+ hematopoietic stem cells (HSCs), a human megakaryoblastic cell line (SET-2), and C57BL/6 mice. We show that treatment with ibrutinib can suppress CD34+ HSC differentiation into megakaryocytes (MKs) and decrease the number of colony-forming unit-MKs (CFU-MKs). The ibrutinib-dependent inhibition of early megakaryopoiesis seems to mainly involve impaired proliferation of progenitor cells without induction of apoptosis. The effects of ibrutinib on late-stage megakaryopoiesis, in contrast to early-stage megakaryopoiesis, include enhanced MK differentiation, ploidy, and proplatelet formation in CD34+ HSC-derived MKs and SET-2 cells. We also demonstrated that MK adhesion and spreading, but not migration, were inhibited by ibrutinib. Furthermore, we revealed that integrin αIIbß3 outside-in signaling in MKs was inhibited by ibrutinib. Consistent with previous clinical observations, in C57BL/6 mice treated with ibrutinib, platelet counts decreased by days 2 to 7 and recovered to normal levels by day 15. Together, these results reveal the pathogenesis of ibrutinib-induced transient thrombocytopenia. In conclusion, ibrutinib suppresses early megakaryopoiesis, as evidenced by inhibition of MK progenitor cell proliferation and CFU-MK formation. Ibrutinib enhances MK differentiation, ploidy, and proplatelet formation, while it impairs integrin αIIbß3 outside-in signaling.

Abivertinib synergistically strengthens the anti-leukemia activity of venetoclax in acute myeloid leukemia in a BTK-dependent manner.

B-cell lymphoma 2 (BCL-2), a crucial member of the anti-apoptotic BCL-2 family, is frequently dysregulated in cancer and plays an important role in acute myeloid leukemia (AML). Venetoclax is a highly selective BCL-2 inhibitor that has been approved by the FDA for treating elderly AML patients. However, the emergence of resistance after long-term treatment emphasizes the need for a deeper understanding of the potential mechanisms of resistance and effective rescue methods. By using RNA-seq analysis in two human AML cohorts made up of three patients with complete remission and three patients without remission after venetoclax treatment, we identified that upregulation of BTK enabled AML blast resistance to venetoclax. Interestingly, we found that abivertinib, an oral BTK inhibitor, could synergize with venetoclax to inhibit the proliferation of primary AML cells and cell lines. It is worth noting that the combination of the two effectively enhanced the sensitivity of two AML patients (AML#3 and AML#12) to venetoclax. In this study, we demonstrated that combined use of the two drugs can synergistically inhibit the colony-forming capacity of AML cells, arrest the AML cell cycle in the G0/G1 phase, and inhibit the BCL-2 anti-apoptotic family protein, activating the caspase family to induce apoptosis. Mechanistically, knockdown of BTK in AML cell lines impaired the synergistic effect of the two drugs. In vivo study showed similar results as those seen in vitro. Abivertinib in combination with venetoclax could significantly prolong the survival time and reduce the tumor burden of MV4-11-NSG mice compared with those of control and single-agent groups. Our in vitro and in vivo studies have shown that the combination of abivertinib and venetoclax may benefit AML patients, especially in patients resistant to venetoclax or those that relapse. New clinical trials will be planned.

A novel alkylating deacetylase inhibitor molecule EDO-S101 in combination with cytarabine synergistically enhances apoptosis of acute myeloid leukemia cells.

Acute myeloid leukemia (AML) is a devastating disease. Hybrid agents with dual activity, which have been shown to possess anti-cancer effect, are expected to potentially improve the prognosis of AML patients. EDO-S101 is a novel alkylating deacetylase inhibitor molecule synthesized by the addition of the hydroxamic acid of histone deacetylases inhibitor vorinostat into bendamustine, a DNA-damaging agent. However, the effect of EDO-S101 in combination with traditional chemotherapy drugs has not been studied in AML. In this study, we investigated the effect of EDO-S101 in combination with cytarabine in treating AML cells. The synergic activity against AML was identified by remarkable reduction of cell viability, significant apoptosis enhancement and the upregulation of the cleaved PARP, Casepase-3 and -7 proteins compared with monotherapy. To explain the drivers, we detected the DNA damage pathway including DNA double-strand breaks marker γ-H2AX and DNA damage checkpoint proteins, which was supposed to be responsible for the enhanced apoptosis activity. In summary, our data demonstrated that EDO-S101 in combination with cytarabine could synergistically induce the apoptosis of AML cells and it might be a potential regimen for treating leukemia.