Growth Of Leukemia Cells Research Articles

IMPDH inhibition activates TLR-VCAM1 pathway and suppresses the development of MLL-fusion leukemia.

Inosine monophosphate dehydrogenase (IMPDH) is a rate-limiting enzyme in de novo guanine nucleotide synthesis pathway. Although IMPDH inhibitors are widely used as effective immunosuppressants, their antitumor effects have not been proven in the clinical setting. Here, we found that acute myeloid leukemias (AMLs) with MLL-fusions are susceptible to IMPDH inhibitors invitro. We also showed that alternate-day administration of IMPDH inhibitors suppressed the development of MLL-AF9-driven AML invivo without having a devastating effect on immune function. Mechanistically, IMPDH inhibition induced overactivation of Toll-like receptor (TLR)-TRAF6-NF-κB signaling and upregulation of an adhesion molecule VCAM1, which contribute to the antileukemia effect of IMPDH inhibitors. Consequently, combined treatment with IMPDH inhibitors and the TLR1/2 agonist effectively inhibited the development of MLL-fusion AML. These findings provide a rational basis for clinical testing of IMPDH inhibitors against MLL-fusion AMLs and potentially other aggressive tumors with active TLR signaling.

Synthesis, characterization and cytotoxicity of copper (II) complex containing a 2H-benzo[e][1,3]oxazin derivative

A new cis-dihalo copper(II) complex, [CuII(HLbz)(Cl)2].CH3CN (1), where HLbz = (S)-2-(((2-(2-(pyridin-2-yl)-2H-benzo[e][1,3]oxazin-3(4H)-yl)ethyl)amino)methyl)phenol), was isolated by reacting copper(II) chloride dihydrate and the H2L ligand (H2L = 2,2′-((2-(pyridin-2-yl)imidazolidine-1,3-diyl)bis(methylene))diphenol) in a MeOH/CH3CN (1:3 v/v) mixture. The complex formation occurred via the ligand modification during complexation, producing a unique structure containing 2H-benzo[e][1,3]oxazin, as observed from the single crystal X-ray structure determination. The complex was characterized by elemental analysis, potentiometric titration, spectroscopic techniques (UV–Vis, FT-IR) and conductance measurements. Complex 1 inhibits the growth of myelogenous leukemia cells with an IC50 of 17.3 μmol L−1.

The ENL YEATS epigenetic reader domain critically links MLL-ENL to leukemic stem cell frequency in t(11;19) Leukemia.

MLL (KMT2a) translocations are found in ~10% of acute leukemia patients, giving rise to oncogenic MLL-fusion proteins. A common MLL translocation partner is ENL and associated with a poor prognosis in t(11;19) patients. ENL contains a highly conserved N-terminal YEATS domain that binds acetylated histones and interacts with the PAF1c, an epigenetic regulator protein complex essential for MLL-fusion leukemogenesis. Recently, wild-type ENL, and specifically the YEATS domain, was shown to be essential for leukemic cell growth. However, the inclusion and importance of the YEATS domain in MLL-ENL-mediated leukemogenesis remains unexplored. We found the YEATS domain is retained in 84.1% of MLL-ENL patients and crucial for MLL-ENL-mediated leukemogenesis in mouse models. Mechanistically, deletion of the YEATS domain impaired MLL-ENL fusion protein binding and decreased expression of pro-leukemic genes like Eya1 and Meis1. Point mutations that disrupt YEATS domain binding to acetylated histones decreased stem cell frequency and increased MLL-ENL-mediated leukemia latency. Therapeutically, YEATS containing MLL-ENL leukemic cells display increased sensitivity to the YEATS inhibitor SGC-iMLLT compared to control AML cells. Our results demonstrate that the YEATS domain is important for MLL-ENL fusion protein-mediated leukemogenesis and exposes an "Achilles heel" that may be therapeutically targeted for treating t(11;19) patients.

Targeting Cell Adhesion Molecules in IDH Mutant Myeloid Malignances

Neomorphic mutations in the genes encoding isocitrate dehydrogenase (IDH) are common in human cancers including myeloid malignancies. The oncometabolite (R)-2-hydroxyglutarate (R-2-HG) produced by mutant IDH promotes leukemia development by competitively inhibiting α-ketoglutarate (α-KG)-dependent dioxygenases, causing epigenetic dysregulation of histone and DNA methylation in myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). FDA-approved allosteric inhibitors (ivosidenib and enasidenib targeting mutant IDH1 and IDH2 respectively) are used for treating newly diagnosed and/or relapsed/refractory AML patients with IDH mutations. However, the low response rate and primary resistance to IDHmut inhibitors are major clinical challenges. Moreover, acquired resistance to IDH inhibition can occur through multiple mechanisms, including R-2-HG-restoring second-site IDH mutations and the selection of sub-clonal mutations in RUNX1/CEBPA or RAS-RTK pathway. These findings underscore the importance of developing new and more effective approaches for the treatment of IDH-mutant MDS and AML patients. To identify mutant IDH-mediated alterations and actionable dependencies, we generated isogenic TF-1 myeloid leukemia cell lines containing endogenous, hotspot IDH mutations (IDH1R132H, IDH2R140Q, IDH2R140W, and IDH2R172K) by CRISPR/Cas9-mediated base-editing. By comparative transcriptomic (RNA-seq) and epigenomic (ATAC-seq and ChIP-seq) profiling of base-edited versus parental isogenic leukemia cells, we identified cell adhesion molecules, especially CD44, as the top upregulated genes in IDH-mutant leukemia cells. CD44 expression is significantly upregulated in IDH-mutant AML patient samples relative to normal CD34+ hematopoietic stem/progenitor cells (HSPCs) or other AML samples without IDH mutations. Increased CD44 expression is also associated with overall poorer survival and therapy resistance in independent AML cohorts. Importantly, we found that ectopic CD44 expression promotes cytokine-independent cell growth of TF-1 myeloid leukemia cells, resembling the effect observed upon expression of mutant IDH. Moreover, CD44 depletion led to decreased R-2-HG levels in base-edited IDH-mutant TF-1 leukemia cells, and impaired the propagation of IDH-mutant leukemia cells in vitro and in xenotransplanted recipient mice. These studies establish direct evidence that IDH mutations cause aberrant activation of cell adhesion molecules such as CD44, and CD44 is required for the propagation of IDH-mutant myeloid leukemia cells. Mechanistically, we found that the aberrantly activated CD44 is first cleaved by matrix metalloproteinases MMP2 and MMP9 for proteolytic release of its ectodomain from membrane, followed by γ-secretase-mediated intramembranous cleavage to produce the CD44 intracellular domain (CD44ICD). CD44ICD subsequently activates the pentose phosphate pathway (PPP) for the production of NADPH, a critical cofactor for mutant IDH enzymes to convert α-KG to R-2-HG. Hence, mutant IDH-mediated activation of CD44 functions to rewire intracellular metabolism to facilitate IDHmut-catalyzed R-2-HG production, supporting a model for mutant IDH-induced feed-forward oncogenic programs. CD44 also activates AKT/ERK signaling pathway to promote the proliferation and cytokine-independent growth of IDH-mutant leukemia cells. More importantly, primary and resistant IDH-mutant leukemia cells are sensitive to combination regimens consisting of IDHmut inhibitors and humanized monoclonal antibody specific for CD44 (RG7536) or MMP2/9 inhibitors (SB-3CT) invitro and invivo. Taken together, our findings uncover the cell adhesion molecule-mediated metabolic signaling as a new targetable dependency of IDH-mutant leukemia cells, with therapeutic implications for more effective treatment of primary and resistant IDH-mutant myeloid malignancies.

Rapid Generation of Murine CLL/Richter Syndrome Models By Multiplexed CRISPR/Cas9 Editing of Common CLL Driver Genes

Background: Recent large-scale next generation sequencing studies have revealed a highly heterogeneous genetic landscape in CLL. However, the majority of the genetic lesions are relatively infrequent and their functional role and clinical relevance are still unknown. Moreover, in vivo models to study how these lesions cooperate between themselves and affect the response to novel therapeutic agents are still lacking. To further understand the relative contribution of individual genetic lesions to CLL development, progression and response to treatment, we performed multiplex CRISPR/Cas9-editing of normal and leukemic murine B cells by targeting a large set of CLL driver genes. Materials and Methods: Multiplexed CRISPR/Cas9 editing was done on normal B1 and B2 B cells isolated from the peritoneal cavity of young (<4 months) del(13q14)MDR-/- mice or on leukemic B1 B cells isolated from the spleen of old (>12 months) Eμ-TCL1 mice using a recently established procedure (Chakraborty et al, Blood 2021). The effects of the introduced genetic lesions on leukemia cell growth and treatment resistance were investigated by analyzing the mutant allele frequency (MAF) of the injected cells and cells recovered from the spleens of untreated or venetoclax-treated mice. Results: To investigate whether multiplex CRISPR/Cas9 editing can be used to transform normal murine B cells derived from del(13q14)MDR-/- mice, we simultaneously targeted 12 putative CLL driver genes representative of cellular pathways that are commonly affected in CLL, including DNA damage response (TP53, ATM and POT1), chromatin modifiers (CHD2, SETD2), cell cycle (RB1), inflammation (SAMHD1) and the NF-kB (BIRC3, NFKBIE, TRAIL-R), NOTCH (FBXW7) and MYC pathways (MGA) (n=4 experiments). The transfected B1 and B2 B cells were transplanted in the peritoneal cavity of B cell-deficient NSG mice and analyzed at different timepoints within a range of 1 to 5 months. Both cellular subsets were detected in the peritoneal cavity of NSG mice at the initial timepoint, but B1 B cells preferentially expanded at the later timepoints, giving rise to CD19+/CD5+ leukemias 3-5 months after transplantation. An increase in MAF was observed for all targeted genes, suggesting that all of the introduced genetic lesions provide a growth advantage to the leukemic cells. To investigate the impact of selected genetic lesions on CLL progression and Richter transformation (RT), we simultaneously introduced activating mutations in NOTCH1 (targeting of the PEST domain) or inactivating mutations in MGA, ATM, TP53, CDKN2A, CDKN2B, BIRC3 and NFKBIE in CLL cells derived from Eμ-TCL1 transgenic mice (n=3 independent experiments). A rise in MAF was observed for all 8 genes following in vivo propagation of the edited cells, suggesting that all of these mutations are positively selected during leukemia progression. However, selection of NOTCH1, TP53, ATM, BIRC3 and NFKBIE mutations occurred more rapidly, reaching the maximum MAF already after the 1st passage in vivo, whereas the MAF of genetic lesions specifically associated with Richter transformation, i.e. CDKN2A, CDKN2B and MGA, rouse more slowly and increased during serial passages (Figure 1). Interestingly, a substantial increase in MAF was observed for CDKN2A and CDKN2B when cells from the 1st passage were placed in culture (from 44% to 93%, p=0.017, and from 64% to 94%, p=0.043, after 6 weeks in culture for CDKN2A and CDKN2B, respectively), consistent with our recent finding that biallelic disruption of these genes allows for spontaneous proliferation of Eμ-TCL1 leukemia cells and may represent the transforming factor in a subset of cases with Richter Transformation. In contrast, the MAF of the other five driver genes showed no or only minor changes during culture. The MAF of CDKN2A and CDKN2B also increased to a greater extent in mice treated with venetoclax compared to untreated mice, indicating that cells with such genetic lesions are more resistant to venetoclax treatment. Conclusions: This study shows that multiplex CRISPR/Cas9 editing can be used to rapidly generate murine leukemias with the genetic make-up of human CLL or Richter Syndrome. These models can represent an important preclinical tool to study how individual genetic lesions cooperate during CLL development and progression and how they affect the response to treatment with novel therapeutic agents. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Activating a Non-Genetic MYC-Regulating Pathway Sensitizes Acute Myeloid Leukemia to Bromodomain Inhibition

MYC (c-Myc) plays a central role in the oncogenic progression and is commonly overexpressed or amplified in more than 50% of human cancers, including acute myeloid leukemia (AML), which is an aggressive disease with over 70% of patients who cannot survive more than five years. Elevated MYC expression is associated with therapeutic resistance and predicts a poorer outcome in AML patients. While numerous lines of evidence have validated MYC as a therapeutic target of AML and many other cancer types, MYC protein itself has been a challenge for therapeutic targeting. Recently, MYC gene transcription has been linked to the bromodomain and extra-terminal domain (BET) family proteins. BET inhibitors (BETi) inhibit MYC expression and have shown promising antitumor activities in preclinical models and are being evaluated in clinical trials. Despite the therapeutic promise, BETi-associated drug resistance and dose-limiting side effects hinder the clinical applications. Therefore, there is a pressing need to understand the mechanisms controlling drug response and resistance to BET inhibitors. To understand the mechanisms that regulate BETi sensitivity, we leveraged a functional CRISPR screen focusing on about 1,700 human transcription factors. We discovered the aryl hydrocarbon receptor (AHR) as a novel regulator of BETi sensitivity in AML. Our results have further identified that a novel AHR-ELMSAN1 axis is critically involved in regulating MYC and BETi sensitivity. Specifically, we show that constitutive or ligand activation of AHR sensitizes leukemia cells to BETi. AHR signaling represses MYC and synergizes with BETi for maximum inhibition of MYC transcription. Ectopic expression of MYC could rescue the anti-leukemia effects induced by combined AHR activation and BET blockade. Mechanistically, our unbiased bioinformatic analysis unexpectedly identified that AHR functions through activating a non-canonical target, ELMSAN1, a less-studied epigenetic factor known as a member of the MiDAC histone deacetylase complex. Depletion of ELMSAN1 leads to upregulation of MYC and blunts AHR signaling-mediated MYC repression and BETi sensitization. Importantly, we demonstrate that AHR agonist and BETi synergistically inhibit MYC and leukemia cell growth in CD34+ primary AML patient samples in vitro and patient-derived xenografts in vivo. In summary, our data suggest that AHR-ELMSAN1 is a novel pathway for MYC repression, activation of which could sensitize AML to BET-targeting agents. As neither AHR nor ELMSAN1 is found mutated in AML, our research may open a new door to new MYC targeting paradigms by activating novel non-genetic MYC repressors.

Phase 1 Results of the First-in-Class CXCR1/2 Inhibitor SX-682 in Patients with Hypomethylating Agent Failure Myelodysplastic Syndromes

Background: SX-682 is an oral dual allosteric inhibitor of the CXCR1 and CXCR2 (CXCR1/2) chemokine receptors, a signaling pathway involved in the recruitment of immunosuppressive MDSCs and autocrine growth of disease-initiating leukemic stem cells (LSCs) in AML and myelodysplastic syndromes (MDS). CXCR2 overexpression is predictive of transfusion dependence in MDS. CXCR2 inhibition reduces proliferation of leukemic cell lines and primary MDS/AML patient (pt) samples in vitro and impairs leukemic growth in an in vivo AML animal model. CXCR2 is also involved in normal neutrophil egress from the bone marrow and thus absolute neutrophil count (ANC) serves as a pharmacodynamic (PD) marker for CXCR1/2 inhibition by SX-682. In pts with normal bone marrow, 25-400 mg SX-682 twice-daily (BID) dose-dependently reduces ANC, with maximum ANC reduction (-66% of baseline) obtained at >150 mg BID, consistent with maximum CXCR1/2 inhibition above this dose. ANC rapidly (24 hrs) normalizes with dose-holding. This NHLBI funded trial (HL142389, NCT04245397) explored the safety and efficacy of SX-682 monotherapy in pts with hypomethylating agent (HMA) failure MDS. Methods: This Phase 1 dose-escalation with expansion study treated five cohorts of HMA failure MDS pts with escalating 25-400 mg BID doses of SX-682 in six continuous 28-day cycles with responding pts continuing treatment. Steady-state pharmacokinetics (PK) were obtained. Response assessment was at the end of cycles 1, 3 and 6 and every third cycle thereafter using IWG criteria (Cheson 2006). This interim analysis after dose-escalation to select the expansion dose was pre-specified. Results:17 MDS pts received SX-682 (median 1 prior therapies; range 1-4) with 6 pts in the 200 mg cohort, 3 pts in each of the 25, 50 and 100 cohorts and 2 pts in the 400 mg cohort (Table). Median age was 76, and pts were low (n=1), intermediate-1 (n=10), intermediate-2 (n=5) and high (n=1) risk by the International Prognostic Scoring System (IPSS). All pts were transfusion-dependent and all had failed prior HMA and 24% lenalidomide. Steady-state PK exhibits increasing drug plasma concentration with dose comparable to pts with solid tumors. The ANC PD marker exhibited a dose-dependent decrease from baseline (ΔANC) that plateaued in the 200 and 400 mg dose cohorts consistent with maximum receptor inhibition (Table). Marrow MDSCs and LSCs were reduced after initiation of SX-682. SX-682 was well-tolerated with no maximally tolerated dose and no pt discontinued treatment for adverse events. Treatment-emergent adverse events > grade 3 were most common in the 200 and 400 mg dose cohorts, and those related to neutrophils are consistent with being related to SX-682. Effects on neutrophils reversed on cessation of drug dosing. There was a dose-dependent increase in overall response rate (ORR) from 0% at 25 mg BID to 50% at 200 mg BID consistent with the observed clinical benefit being related to CXCR1/2 inhibition by SX-682 (Table). Four of the five responders had mutant genes (MGs) involving splicing factors (60% of responders; SF3B1, SRSF2) and/or epigenetic regulation (60% of responders; TET2, ASXL1, IDH2). Across all dose cohorts, 8 of 17 (47%) pts had a reduction in marrow blasts after initiating SX-682 (Figure). The 200 mg dose yielded the most rapid and deep reduction in blasts with 2 of 6 pts (33%) achieving a marrow complete remission (mCR) in keeping with this dose providing maximum receptor inhibition. There was hematologic improvement (HI) in 3 pts with one having a durable near-CR response (on SX-682 >500 days) consisting of trilineage HI (hemoglobin > 10 g/dL) and transfusion independence for over 4 months (pt required 16 transfusions in the 7 weeks before starting SX-682 therapy). Based on ANC PD, ORR and marrow blast responses, the 200 mg BID dose was selected for the expansion phase of the trial. Conclusions: SX-682 is a novel therapy in HMA failure MDS with dual activity against LSCs and MDSCs. SX-682 was well tolerated with encouraging efficacy with a biologically effective oral dose selected at 200 mg BID. An expansion cohort in both lower and higher risk MDS pts is ongoing and will additionally include HMA naïve patients. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

PHF6 Maintains Acute Myeloid Leukemia Via Regulating NF-Κappab Signaling Pathway

Acute myeloid leukemia (AML) is a major hematopoietic malignancy characterized by the uncontrolled expansion of the immature myeloid cells in the hematopoietic system. Current chemotherapy regimens remain ineffective as assessed by low remission and 5-year-survival rate. Many efforts have been dedicated to decipher the molecular events underlying AML transformation. PHF6 is a conserved epigenetic regulator and has been found to be frequently altered in hematologic malignancies. Previous studies demonstrated that PHF6 plays a suppressive role in T-ALL leukemogenesis. However, the functional role(s) of PHF6 in AML initiation and progression remains unknown. Here in this study, we analyzed the mRNA expression of PHF6 in blood cells from healthy donors and leukemia cells from AML patients, and found that the PHF6 expression was significantly increased in AML cells when compared with that of normal PMNs (www.Bloodspot.com) (p < 0.05). Significantly, the average survival time of AML patients with high PHF6 expression was much shorter than that of AML patients with low PHF6 expression (p = 0.022). Overexpressing of PHF6 (PHF6 OE) in Kasumi-1 or K562 leukemia cell lines showed increased growth of Kasumi-1 and K562 cells, decreased apoptosis of Kasumi-1 cells. Additionally, we knocked down (KD) PHF6 expression in AML cells and CD34+ cord blood cells, and found that PHF6 KD significantly decreased the growth of Kasumi-1 and promoted cell apoptosis, while had little effects on apoptosis of CD34+ cord blood cells. These results suggested that PHF6 is required for the growth of myeloid leukemia cells but is dispensable for normal blood cells. To further evaluate the functional role of Phf6 in leukemogenesis in vivo, we generated Phf6 KO+RUNX1-ETO9a (RE9a) and Phf6 KO+MLL-AF9 (MA9) AML mice. We found the survival time of Phf6 KO+RE9a mice was significantly longer than that of WT Phf6+RE9a mice. The Phf6 KO+RE9a mice showed much milder disease phenotypes than WT Phf6+RE9a mice, including lower counts of GFP+ leukemia cells in the PB and BM, higher body weights, lower spleen and liver weights, and lower degree of extramedullary infiltration in spleen, liver, lung and brain. Extreme limiting dilution transplantation assays demonstrated a marked decrease in leukemia stem cell (LSC) activity in Phf6 KO+RE9a cells when compared with Phf6 WT+RE9a cells. Consistent with RE9a-induced AML mouse model, PHF6 deficiency impaired the self-renewal of LSCs and delayed the progression of MA9-induced AML, supporting a general oncogenic role of Phf6 in sustaining myeloid leukemia. To investigate the underlying molecular mechanisms of Phf6 in regulating AML development, we performed RNAseq to analyze the transcriptome programing changes associated with Phf6 deficiency in isogenic Phf6 WT+RE9a or Phf6 KO+RE9aAML cells. Gene set enrichment analysis (GSEA) showed up-regulation of apoptosis and down-regulation of NF-κB-regulated gene expressions in Phf6 KO+RE9a cells, suggesting that Phf6 depletion might promote AML cell apoptosis by blocking the NF-κB signaling. Immunocytochemistry studies showed that PHF6 depletion partially inhibited the nuclear translocation of p50. Co-immunoprecipitation experiments revealed that PHF6 directly bound to p50 in myeloid leukemia cells, suggesting that PHF6 might activate NF-κB signaling pathways by binding with p50 and maintaining the nuclear translocation of p50. To confirm this, we treated PHF6 OE AML cells with BAY11-7082 (a selective NF-κB inhibitor), and found BAY11-7082 significantly inhibited the growth of PHF6 OE Kasumi-1 cells in vitro. In summary, we revealed that PHF6 promoted RE9a- or MA9-induced AML progression in mice by activating NF-κB signaling pathway, and promoting P50 nuclear translocation. Our study thus defined a unique role for Phf6 in regulating NF-κB signaling pathway in AMLs, and potentially can be used as a therapeutic target for treating myeloid leukemia patients.

Changes in the T Helper Cell Compartment during Treatment with the BTK Inhibitor Acalabrutinib

Interactions with T helper cells are part of the supportive lymph node microenvironment promoting chronic lymphocytic leukemia (CLL) cell growth and survival. Treatment of CLL patients with ibrutinib, the first-in-class BTK inhibitor, induces profound changes in the T cell compartment, with normalization of elevated T cell numbers and plasma cytokine levels, and diversification of the T cell receptor (TCR) repertoire (Yin Q et al., J Immunol 2017). Acalabrutinib, a second generation BTK inhibitor, is more selective for BTK, with less off-target effects towards other kinases, including IL-2-inducible T cell kinase (ITK), an important kinase for T cell signaling. To characterize acalabrutinib effects on T cell numbers and function in patients with CLL, we analyzed serial samples from 12 acalabrutinib-treated CLL patients at baseline, after 1 week, and after 1, 3, 6, and 12 months of continuous acalabrutinib treatment (with monthly Obinutuzumab added during months 3-9) in an ongoing Phase 2 trial (NCT04505254). Six age-matched healthy donors (HD) were analyzed for comparison. T cell subsets were characterized by flow cytometry. Functional T cell response were assessed after stimulation with phorbol myristate acetate and ionomycin, and proliferation by Ki-67 expression. Prior to treatment, untreated CLL patients had elevated numbers of CD4+ (1864±32/ml) and CD8+ (2533±452/ml, mean T cells which normalized after 12 months of therapy (CD4+ 514±65/ml, p<0.01; and CD8+ 747±271/ml, p<0.05). Two key subsets, T follicular helper cells (Tfh) and T regulatory cells (Tregs), also decreased significantly after 12 months of treatment (Tfh from 2.9±0.4% to 0.2±0.1%, p<0.05; and Tregs from 2.4±0.4% to 0.9±0.2%, p<0.05). Next, we analyzed expression of Tfh and Treg surface markers and found significant down-modulation of CD69 (on Tfh from 20±3.7% to 3.3±0.6%, p<0.001; on Tregs from 10±1.8% to 1.7±0.5%, p<0.01), ICOS (on Tfh from 33±2.6% to 13±1.6%, p<0.01), PD-1 (on Tregs from 7.8±1.3% to 1.2±0.3%, p<0.01), and CTLA-4 (on Tfh from 16±3.2% to 3.8±1.0%, p<0.05; on Tregs from 14±1.5% to 3.1±0.7%, p<0.001) after 12 months of treatment. Additionally, this therapy resulted in reduced cytokine production by Tfh and Tregs when compared to baseline samples, as quantified by flow cytometry after cytoplasmatic staining. For example, induced IL-21 expression decreased from 23±1.3% in baseline samples to 12±0.5% after 12 months, p<0.05 (for comparison, 5.7%±1.3% in HD), IL-10 decreased from 7.3±1.1% to 0.9±0.2% at 12 months, p<0.05 (0.9%±0.1% in HD), and TGFb (from 6.2±0.9% to 0.8±0.2% at 12 months, p<0.01 (1.6%±0.5% in HD). Moreover, circulating Tfh cells from pre-treatment samples expressed higher levels of the co-stimulatory molecule CD40L upon restimulation at baseline compared to after 12 months of treatment and the levels in HD (from 23.0±1.6% to 11.0±1.1% at 12 months, p<0.05; versus 3.8%±1.0% in HD, p<0.001). Looking at Ki-67 expression, we noted, as expected, a significant decrease in CLL cell proliferation from 3.9±0.8% down to 0.8±0.6% after 1 month of therapy (p<0.001), similar data were seen at later time points. Interestingly, Tregs also had reduced Ki-67 expression, down from 16±0.6% to 7.3±0.9% after 6 months (p<0.01) and to 7.9%±1.1% after 12 months of therapy (p<0.05). Collectively, the reduction in T cells and T helper cell subset numbers, along with changes in surface activation markers, and reduced cytokine and Ki-67 expression suggest that an activated pre-treatment T helper cell compartment normalizes during continuous acalabrutinib therapy. These findings are reminiscent of the T cell data from patients receiving ibrutinib therapy, suggesting that off-target effects of the BTK inhibitor may not dictate T helper cell changes, and these may rather be due to activation by the CLL clone, which diminishes as the underlying disease responds to treatment.

Pharmacologic Inhibition of DYRK1A Results in Hyperactivation and Hyperphosphorylation of MYC and ERK Rendering KMT2A-R ALL Cells Sensitive to BCL2 Inhibition

Background: B-cell acute lymphoblastic leukemia (ALL) harboring KMT2A-rearrangements (KMT2A-R) is a high-risk ALL subtype with significant relapse risk and poor overall survival across the age spectrum. While new antibody-based and cellular immunotherapies have revolutionized the therapeutic paradigm for many patients with relapsed ALL, application of these therapies has proven particularly challenging to date in infants given their immune system immaturity and in older adults prone to high-grade immunotherapy toxicities. Unlike other ALL subtypes, KMT2A-R ALL has an extremely low frequency of co-mutations, which makes it particularly difficult to find new treatment options. To identify targetable kinases in KMT2A-R ALL, we performed a domain-specific kinome-wide CRISPR screen and identified the serine/threonine kinase DYRK1A as required for the survival of KMT2A-R ALL. Importantly, DYRK1A appears to be non-essential for normal tissues per the Cancer Dependency MAP, suggesting potential for a therapeutic window via DYRK1A targeting. Results:In vitro treatment studies using three different menin inhibitors (MI-2-2 / MI-503 / VTP50469) to disrupt the transcriptional activity of the KMT2A-R complex resulted in the downregulation of DYRK1A at the RNA and the protein level. We further analyzed ChIP-Seq data and identified that oncogenic KMT2A-R directly binds to the DYRK1A promoter, indicating that DYRK1A is directly regulated by the oncogenic KMT2A fusion. Interestingly, the DYRK1A RNA and protein levels were elevated in KMT2A-R ALL cell lines and patient-derived xenograft (PDX) samples compared to non-KMT2A-R ALL cases. To test the consequence of direct pharmacologic DYRK1A inhibition on cell proliferation and apoptosis, we treated KMT2A-R ALL cells with the DYRK1A inhibitors EHT1610 and harmine. Interestingly, we observed that pharmacologic inhibition of DYRK1A with both drugs did not induce apoptosis but induced potent leukemic cell growth inhibition in vitro and in vivo. In preliminary studies, we further observed that pharmacologic inhibition of DYRK1A or genetic deletion resulted in MYC upregulation and hyperphosphorylation of ERK. It has been demonstrated that premature signaling activation in developing B cells induces cell cycle arrest as a protective mechanism to prevent the development of autoimmune diseases. We hypothesized that DYRK1A inhibitor-induced ERK hyperactivation and consequent cell cycle arrest remains a conserved mechanism in KMT2A-R ALL. Supporting our hypothesis, combining DYRK1A inhibitors with the MEK inhibitor trametinib antagonistically rescued KMT2A-R ALL cell proliferation, indicating that ERK hyperactivation is the main driver of DYRK1A inhibitor mediated cell cycle arrest. Given that DYRK1A inhibition does not induce apoptosis and cells restart to proliferate after DYRK1A inhibitor withdrawal, we concluded that a DYRK1A monotherapy may not be an ideal new treatment option. Interestingly, it has been reported that increased MYC activity induces the accumulation of BIM in Burkitt's Lymphoma. BIM is a pro-apoptotic molecule that is inactive when bound by the anti-apoptotic molecule BCL2. Given that DYRK1A inhibition results in MYC upregulation, we performed a new Western blot analysis and validated that EHT1610 and harmine both induce BIM overexpression in KMT2A-R ALL cell lines. To test if combined DYRK1A and BCL2 inhibition will lead to enhanced KMT2A-R ALL apoptosis, we treated four KMT2A-R ALL cell lines with increasing concentrations of EHT1610 and the BCL2 inhibitor venetoclax. Strikingly, combining both drugs synergistically killed KMT2A-R ALL cells in vitro. More importantly, we validated the anti-leukemic effect of harmine in combination with venetoclax in mice injected with a KMT2A-R PDX case. Conclusion: Our results validate DYRK1A as an important molecule to regulate cell proliferation via inhibition of MYC and ERK. Targeting DYRK1A results in the accumulation of BIM, which renders the cells sensitive to BCL2 inhibition via venetoclax. While further in vivo studies are needed, we predict that combining DYRK1A inhibition with venetoclax may be a novel precision medicine strategy for the treatment of KMT2A-R ALL. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Metformin Inhibits Acute Myeloid Leukemia Cells Growth through the AMPK/mTOR Pathway and Autophagic Regulation

Metformin (MET) can be used to slow the aging process and treat cancers. Although reports indicate the efficacy of MET combined with other treatments on acute myeloid leukemia (AML), the detailed mechanisms of its effect on AML remain unresolved. This study aimed to find a potential effective strategy of AML by analyzing the inhibitory mechanisms of MET on AML. The effect of MET on AML cell growth was examined by treating Kasumi-1, HL-60, and U937 cells with MET ranging between 0.5 and 40 mM for 72 h. MET was found to markedly inhibit the growth of all AML cell lines in a dose-dependent manner. The mechanism of growth inhibition by MET was further investigated by examining the cell-cycle profile using flow cytometry after treating AML cells with 10 mM MET for 36 h. MET treated groups presented the majority of cells in the G0/G1 phase of the cell cycle vs. the control groups. We also showed that the level of green fluorescence increased in Kasumi-1, HL-60, and U937 cells treated with MET for 72 h at various concentrations using the TUNEL apoptosis kit. The role of MET in inhibiting AML cells was explored by inducing autophagy both in AML cell lines and primary AML cells. Following treatment with 10 mM MET for 36 h, MET-treated group clearly had more phagophores than untreated cells. The mechanisms underlying the anti-proliferative effects of MET were investigated by characterizing the effects of MET on the AMPK/mTOR pathway. In addition, flow cytometry showed that knockdown of AMPK abrogated MET-induced AML cell cycle arrest. Moreover, a combined MET and daunorubicin treatment gave an additive effect in vitro and in vivo. The results suggest that MET could inhibit AML growth by targeting multiple signaling pathways, and MET combined treatment may be a promising therapy for AML.

Trial in Progress: A Phase I/II Study to Assess Safety, Tolerability and Preliminary Efficacy of Bexmarilimab in Combination with Standard of Care in Patients with Hematological Malignancies (BEXMAB)

Background: Emerging data on the role of leukemic cells on shaping the tumor immune environment places macrophages as target cells and immune checkpoints in acute myeloid leukemia (AML) (Miari et. al. Front. Cell Dev. Biol.2021; Sallman et. al. Blood 2019). CLEVER-1 (common lymphatic endothelial and vascular endothelial receptor-1) constitutes such macrophage checkpoint. The receptor contributes to tumor immune tolerance by antigen clearing and T cell inhibition. In multiple models, tumor growth is significantly reduced in CLEVER-1 absence (Viitala et. al. Clin Cancer Res 2019). CLEVER-1 expression level is a prognostic factor for poor outcomes in AML (Pölönen et. al. Cancer Research 2019) and its suppression inhibits leukemia cell growth. Analyses suggests lower expression is associated with venetoclax sensitivity (Lin et al. Mol Ther 2019). Bexmarilimab (FP-1305; BEX), an IgG4 monoclonal antibody, binds CLEVER-1 and alters the function of macrophages and inactive T cells. BEX was shown to increase antigen presentation, induce proinflammatory cytokines and infiltration of activated T cells (Viitala et. al. Clin Cancer Res 2019). The therapeutic potential of BEX is supported with data from the MATINS study (NCT03733990) evaluating single agent in advanced solid tumors. Up to 40% of patients in selected indications experience disease control (stable disease/partial response) associated with a 65% chance of 1-year overall survival (OS) compared to 11% of patients without disease control. BEX treatment is well tolerated without any dose limiting toxicity (DLT) reported. CLEVER-1 is highly expression on malignant blasts and monocytes of bone marrow from AML and myelodysplastic syndrome (MDS) patients. Treatment of these BM cells with BEX alone or in combination with azacitidine or venetoclax results in enhanced antigen presentation capacity and increased activation markers on effector T cells with synergistic effects (EHA 2022 P380). Study Design and Methods: The PhI/II study investigates BEX treatment plus standard of care in MDS, chronic myelomonocytic leukemia (CMML) frontline or hypomethylating agent (HMA)-failed patients or newly diagnosed AML or relapsed/refractory (r/r) AML patients (NCT05428969). Enrollment is ongoing. Ph I is a dose escalation using a Bayesian optimal interval (BOIN) design to explore 4 dose levels of BEX in a cohort size of 5 with 1.0 mg/kg as starting dose. BEX plus azacitidine (doublet) is assessed in a mixed cohort of MDS, CMML frontline and hypomethylating agent (HMA)-failure patients or r/r AML patients. Dose determination may then be performed in separate indications. BEX plus azacitidine + venetocolax (triplet) will follow a similar BOIN design for dose determination in patients with newly diagnosed AML unfit for induction chemotherapy. BEX is dosed in 28-day cycles Q1W during cycles 1-3 followed by Q2W dosing, until disease progression or intolerable toxicity. Standard of care therapy is administered as per label. During Ph II, selected indications are explored for efficacy when BEX is administered at recommended phase 2 dose (RP2D) determined in the doublet and triplet. Dose expansion follows a 2-Stage design with indication-specific target efficacy rates, including complete remission +/- incomplete hematologic recovery, overall response rate or minimal residual disease (MRD)-negativity. Primary endpoints are safety and tolerability, RP2D of BEX and preliminary efficacy. Secondary endpoints include extended efficacy for duration of response, event free survival and OS. Exploratory endpoints are focused on pharmacodynamic parameters for immunological and cellular read-outs and the association of predictive biomarker of BEX clinical activity in different patient sub-groups. Key eligibility includes patient ≥ 18 years of age presenting with morphologically confirmed diagnosis of either MDS (intermediate-very high rIPSS risk), CMML-2 with indication for azacitidine treatment; CMML and MDS patients with failure to HMA therapy, confirmed diagnosis of r/r AML following at least 1 prior treatment line or diagnosis of AML in patients unfit for induction therapy with indication for azacitidine + venetoclax. Patients with APL or myeloproliferative CMML, active auto-immune disorder or requiring systemic corticosteroid or other immunosuppressive treatment are excluded. Approximately 181 patients at 10 US and EU sites will be enrolled.

UM171 cooperates with PIM1 inhibitors to restrict HSC expansion markers and suppress leukemia progression

The pyrimido-indole derivative UM171 promotes human Hematopoietic Stem Cells Expansion (HSCE), but its impact on leukemia is not known. Herein, we show in a mouse model of erythroleukemia that UM171 strongly suppresses leukemia progression. UM171 inhibits cell cycle progression and apoptosis of leukemic cells in culture. The effect of UM171 on leukemia differentiation was accompanied by increased expression of HSCE markers. RNAseq analysis combined with Q-RT-PCR and western blotting revealed that the PIM1 protein kinase is highly elevated in response to UM171 treatment. Moreover, docking analysis combined with immunoprecipitation assays revealed high binding affinity of UM171 to PIM1. Interestingly, pan-PIM kinase inhibitors counteracted the effect of UM171 on HSCE marker expression and PIM1 transcription, but not its suppression of leukemic cell growth. Moreover, combination treatment with UM171 and a pan-PIM inhibitor further suppressed leukemic cell proliferation compared to each drug alone. To uncover the mechanism of growth inhibition, we showed strong upregulation of the cyclin-dependent kinase inhibitor P21CIP1 and the transcription factor KLF2 by UM171. In accordance, KLF2 knockdown attenuated growth inhibition by UM171. KLF2 upregulation by UM171 is also responsible for the activation of P21CIP1 in leukemic cells leading to a G1/S arrest and suppression of leukemogenesis. Thus, suppression of leukemic growth by UM171 through KLF2 and P21CIP1 is thwarted by PIM-mediated expansion of leukemic stemness, uncovering a novel therapeutic modality involving combined UM171 plus PIM inhibitors.

Extracellular Vesicles Derived from Human Bone Marrow Stem Cells Inhibit Acute Lymphoblastic Leukemia Cell Growth by Inhibiting MAPK Pathway via the miR-29b-3p/GDF15 Axis

Introduction: Acute lymphoblastic leukemia (ALL) is a common hematologic neoplastic disease. This study discussed the effect of extracellular vesicles (EVs) released from bone marrow mesenchymal stem cells (BMSCs) on ALL cells and the mechanism. Methods: BMSCs-EVs were isolated by differential centrifugation and identified. The effect of BMSCs-EVs on ALL cell proliferation and apoptosis was evaluated. The expression of miR-29b-3p in ALL cells and EVs was detected. The uptake of EVs by ALL cells was observed. The effect of miR-29b-3p on ALL cell proliferation and apoptosis was assessed after silencing miR-29b-3p. The targeting relation of miR-29b-3p and GDF15 was analyzed by bioinformatics website and dual-luciferase assay. The role of GDF15 in proliferation and apoptosis of ALL cells was further confirmed, and Western blot assay was performed to measure MAPK pathway-related protein levels. Results: BMSC-derived EVs inhibited proliferation and promoted apoptosis of ALL cells, as shown by the up-regulation of caspase-3 and Bax expressions and down-regulation of Bcl-2 expression. EVs carried miR-29b-3p into ALL cells, upregulated miR-29b-3p expression in ALL cells, and inhibited GDF15 expression. Silencing of miR-29b-3p or overexpression of GDF15 partially reversed the effect of EVs. EVs inhibited the MAPK pathway through the miR-29b-3p/GDF15 axis. Conclusion: BMSCs-EVs carried miR-29b-3p into ALL cells, upregulated miR-29b-3p, and inhibited GDF15 to suppress the MAPK pathway and further inhibit proliferation and promote apoptosis of ALL cells.

Novel nitrogen mustard-artemisinin hybrids with potent anti-leukemia action through DNA damage and activation of GPx

The incidence of various types of cancers is increasing every year. Among these, leukemia is extremely common, and thus, developing novel drugs to combat leukemia is crucial. In this study, we designed and synthesized several hybrids and obtained a new lead molecule 5a, with a strong therapeutic effect on leukemia. The results indicated that most hybrids effectively inhibited the growth of leukemia cells, HCT-116, and A549 cancer cells with an IC50 of <10 μM. Among these hybrids, 5a and 4h showed significant anticancer activity against CCRF-CEM, with IC50 values of 0.895 μM and 0.555 μM, respectively. Particularly, 5a had lower toxicity to L02 than chlorambucil (CLB) and doxorubicin (Dox), and the high selectivity was also reflected in the normal human B lymphoblast cell line (IM9). Upon investigating the mechanism of action, we found that 5a downregulated Bcl-2 and caused DNA double-stranded breaks (DSBs) to induce several genotoxic stress responses. The results of the flow cytometry assay showed that 5a was a non-specific molecule in the cell cycle. Furthermore, 5a did not affect total ROS levels but significantly improved the activity of glutathione peroxidase (GPx). Preliminary studies showed that nitrogen mustard exerted an efficient effect, and 5a can combine the advantages of artemisinin and nitrogen mustard and exhibit effects superior to either. This study showed that 5a should be further investigated as a therapeutic compound against leukemia.

CML-164 Dihydroorotate Dehydrogenase Inhibition Reveals Metabolic Vulnerability in Chronic Myeloid Leukemia

There are chronic myeloid leukemia (CML) patients who show resistance to TKI therapy and are prone to progress to more advanced phases of the disease, and new therapeutic approaches are needed. Our study shows that CML cells are vulnerable to dihydroorotate dehydrogenase (DHODH) inhibition mediated by Meds433, a potent DHODH inhibitor developed by our group. Pyrimidine supply in resting and differentiated cells primarily relies on the salvage pyrimidine pathway, which is energetically affordable. This level of nucleotide production for fast-proliferating leukemic cells is insufficient, and they have to fulfill their needs via the de novo pathway. In this study, we shed light on the role of DHODH inhibition in CML and how it can be a promising approach for targeting leukemic cells. Sixty bone marrow samples and peripheral blood of newly diagnosed CML patients and 4 TKI-resistant patients were collected. In-vivo, in-vitro, and ex-vivo experiments were performed on primary CML CD34+ and various CML cell lines. Our data showed that DHODH is highly active in CML stem/progenitor cells, which supports a high proliferation capacity. Meds433, by targeting DHODH enzyme activity, induced apoptosis, cell growth, and cell cycle arrest in leukemic cells. Meanwhile, the administration of Meds433 reduced tumor growth and tumor burden in treated mice. Interestingly, the addition of exogenous uridine rescued all of the biological effects caused by DHODH inhibition, demonstrating the selectivity of Meds433. Based on RNA-seq data, most upregulated gene sets were related to apoptosis and immune response and most downregulated gene sets were related to MYC targets and metabolism pathways, which was confirmed by metabolic profile analysis. Also, we found that glutamic pyruvic acid transaminase 1 (GPT1) is among the top downregulated genes after treating CML cells with Meds433, and overexpressing GPT1 in CML cells interfered with the effect of Meds433. These data show that GPT1 downregulation could be one of the possible mechanisms in which Meds433 acts in CML. Our study shows that DHODH inhibition is a promising approach for targeting CML stem/progenitor cells and may help more patients discontinue the therapy. This work was supported by Associazione Italiana per la Ricerca sul Cancro: IG-23344.

Evaluation of Serum Interleukin-15 in Acute Lymphoid and Myeloid Leukemia Patients.

The interleukin-15 is a unique proinflammatory cytokine associated with immune response regulation and the growth, survival, and biological behavior of leukemic cells. This study assesses the effect of both types of acute malignancies, lymphoid and myeloid, on the interleukin-15 serum levels for Acute Lymphoid Leukemia and Acute Myeloid Leukemia patients. The interleukin-15 serum levels were measured for 21 acute lymphoid leukemia patients and 21 acute myeloid leukemia patients compared to healthy people (24) as a control group using the ELISA Peprotech Company (USA), a protocol kit. The research data explain a significant decrease in interleukin-15 serum level for acute lymphoid leukemia (ALL) patients (99 pg/ml)compared with the healthy group (126 pg/ml) at level (P value=0.009), while the acute myeloid leukemia (AML) (141 pg/ml) patients recorded a nonsignificant increase in IL-15 serum level from the healthy group at (P>0.05). The data outcome clarified an important effect of acute lymphoid leukemia in reduced proinflammatory interleukin-15 serum level due to impairment in T and B lymphocyte production, which is correlated with immunosuppression response toward leukemia, while acute myeloid leukemia non-significantly increases the interleukin-15 serum level.

Research Progress of m6A Methylation Modification in Hematological Tumors--Review

N6-methyladenosine (m6A) is one of the most common epigenetic modifications of eukaryotic mRNAs, which is involved in the regulation of gene expressions and biological processes in a variety of cells with dynamic and reversible methylation processes. In recent years, many studies have shown that m6A methylation modification not only acts on the growth, proliferation, and medullary differentiation of acute myeloid leukemia cells, but also participates in the regulation of the proliferation and apoptosis of other hematological tumor cells such as chronic myeloid leukemia and diffuse large B-cell lymphoma, and it can even weaken the efficacy of anti-hematological tumor immunotherapy and induce immune escape leading to tumor resistance. With the successive development of a variety of m6A methylation-related enzyme inhibitors, it will provide new therapeutic ideas for patients with relapsed and refractory hematological tumors. In this paper, we review the research progress on the mechanism of m6A methylation on the occurrence, development, and tumor immunity of various hematological tumors.

BRD4 PROTAC degrader MZ1 exerts anticancer effects in acute myeloid leukemia by targeting c-Myc and ANP32B genes

ABSTRACT Acute myeloid leukemia (AML) is a highly cancerous and aggressive hematologic disease with elevated levels of drug resistance and relapse resulting in high mortality. Recently, bromodomains and extra-terminal (BET) protein inhibitors have been extensively researched in hematological tumors as potential anticancer agents. MZ1 is a novel BET inhibitor that mediates selective proteins degradation and suppression of tumor growth through proteolysis-targeting chimeras (PROTAC) technology. Accordingly, this study aimed to investigate the role and therapeutic potential of MZ1 in AML. In this study, we first identified that AML patients with high BRD4 expression had poor overall survival than those with low expression group. MZ1 inhibited AML cell growth and induced apoptosis and cycle arrest in vitro. MZ1 induced degradation of BRD4, BRD3 and BRD2 in AML cell strains. Additionally, MZ1 also initiated the cleavage of poly-ADP-ribose polymerase (PARP), which showed cytotoxic effects on NB4 (PML-RARa), K562 (BCR-ABL), Kasumi-1 (AML1-ETO), and MV4-11 (MLL-AF4) cell lines representing different molecular subtypes of AML. In AML mouse leukemia model, MZ1 significantly decreased leukemia cell growth and increased the mouse survival time. According to the RNA-sequencing analysis, MZ1 led to c-Myc and ANP32B genes significant downregulation in AML cell lines. Knockdown of ANP32B promoted AML cell apoptosis and inhibited cell growth. Overall, our data indicated that MZ1 had broad anti-cancer effects on AML cell lines with different molecular lesions, which might be exploited as a novel therapeutic strategy for AML patients.

Small RNA-Seq Reveals Similar miRNA Transcriptome in Children and Young Adults with T-ALL and Indicates miR-143-3p as Novel Candidate Tumor Suppressor in This Leukemia.

We aimed to identify miRNAs and pathways specifically deregulated in adolescent and young adult (AYA) T-ALL patients. Small RNA-seq showed no major differences between AYA and pediatric T-ALL, but it revealed downregulation of miR-143-3p in T-ALL patients. Prediction algorithms identified several known and putative oncogenes targeted by this miRNA, including KRAS, FGF1, and FGF9. Pathway analysis indicated signaling pathways related to cell growth and proliferation, including FGFR signaling and PI3K-AKT signaling, with the majority of genes overrepresented in these pathways being predicted targets of hsa-miR-143-3p. By luciferase reporter assays, we validated direct interactions of this miRNA with KRAS, FGF1 and FGF9. In cell proliferation assays, we showed reduction of cell growth upon miR-143-3p overexpression in two T-ALL cell lines. Our study is the first description of the miRNA transcriptome in AYA T-ALL patients and the first report on tumor suppressor potential of miR-143-3p in T-ALL. Downregulation of this miRNA in T-ALL patients might contribute to enhanced growth and viability of leukemic cells. We also discuss the potential role of miR-143-3p in FGFR signaling. Although this requires more extensive validation, it might be an interesting direction, since FGFR inhibition proved promising in preclinical studies in various cancers.