Combining the novel FLT3 and MERTK dual inhibitor MRX-2843 with venetoclax results in promising antileukemic activity against FLT3-ITD AML.

FMS-like tyrosine kinase 3 (FLT3) mutations occur in approximately one third of acute myeloid leukemia (AML) patients. FLT3-Internal tandem duplication (FLT3-ITD) mutations are the most common FLT3 mutations and are associated with a poor prognosis. Gilteritinib is a FLT3 inhibitor that is US FDA approved for treating adult patients with relapsed/refractory AML and a FLT3 mutation. While gilteritinib monotherapy has improved patient outcome, few patients achieve durable responses. Combining gilteritinib with venetoclax (VEN) appears to make further improvements, though early results suggest that patients with prior exposure to VEN fair much worse than those without prior exposure. MRX-2843 is a promising inhibitor of FLT3 and MERTK. We recently demonstrated that MRX-2843 is equally potent as gilteritinib in FLT3-ITD AML cell lines in vitro and primary patient samples ex vivo. In this study, we investigated the combination of VEN and MRX-2843 against FLT3-ITD AML cells. We found that VEN synergistically enhances cell death induced by MRX-2843 in FLT3-mutated AML cell lines and primary patient samples. Importantly, we found that VEN synergistically enhances cell death induced by MRX-2843 in FLT3-ITD AML cells with acquired resistance to cytarabine (AraC) or VEN+AraC. VEN and MRX-2843 significantly reduce colony-forming capacity of FLT3-ITD primary AML cells. Mechanistic studies show that MRX-2843 decreases Mcl-1 and c-Myc protein levels via transcriptional regulation and combined MRX-2843 and VEN significantly decreases oxidative phosphorylation in FLT3-ITD AML cells. Our findings highlight a promising combination therapy against FLT3-ITD AML, supporting further in vitro and in vivo testing.

KDM4C contributes to cytarabine resistance in acute myeloid leukemia via regulating the miR-328-3p/CCND2 axis through MALAT1.

AIMS: Acute myeloid leukemia (AML) is an aggressive hematologic neoplasm, in which relapse due to drug resistance is the main cause for treatment failure and the disease progression. In this study, we aimed to investigate the molecular mechanism of KDM4C-dependent MALAT1/miR-328-3p/CCND2 axis in cytarabine (Ara-C) resistance in the context of AML. METHODS: Bioinformatics analysis was performed to predict the targeting relationships among KDM4C, MALAT1, miR-328-3p, and CCND2 in AML, which were validated with chromatin immunoprecipitation and dual-luciferase reporter assay. Methylation-specific polymerase chain reaction was conducted to detect the methylation of MALAT1 promoter. After conducting gain- and loss-of-function assays, we investigated the effect of KDM4C on cell Ara-C resistance. A NOD/SCID mouse model was established to further investigate the roles of KDM4C/MALAT1/miR-328-3p/CCND2 in Ara-C resistant AML cells. RESULTS: KDM4C expression was upregulated in AML. KDM4C upregulation promoted the demethylation in the promoter region of MALAT1 to increase its expression, MALAT1 targeted and inhibited miR-328-3p expression, enhancing the Ara-C resistance of HL-60/A. miR-328-3p targeted and suppressed the expression of CCND2 in HL-60/A to inhibit the Ara-C resistance. Mechanistically, KDM4C regulated miR-328-3p/CCND2 through MALAT1, resulting in Ara-C resistance in AML. Findings in an in vivo xenograft NOD/SCID mouse model further confirmed the contribution of KDM4C/MALAT1/miR-328-3p/CCND2 in the Ara-C resistant AML. CONCLUSION: Our study demonstrated that KDM4C may up-regulate MALAT1 expression, which decreases the expression of miR-328-3p. The downregulation of miR-328-3p increased the level of CCND2, which induced the Ara-C resistance in AML.

Compound Heterozygous Mutations in the F7 Gene in 2 Unrelated Families With Congenital Factor VII Deficiency.

Factor VII (FVII) deficiency is a rare bleeding disorder normally caused by homozygous and compound heterozygous mutations in the F7 gene. Whole-exome sequencing was performed to identify F7 mutations in 3 individuals from 2 unrelated families who were diagnosed with FVII deficiency. Four compound heterozygous mutations were identified and validated in these 3 probands with FVII deficiency. Among the 4 identified mutations, NM_000131.4:c.572-1_581del, NM_000131.4:c.1250A>G (p.Tyr417Cys), and NM_000131.4:c.647G>T (p.Gly216Val) were novel. All 3 novel mutations were predicted to be likely pathogenic by the American College of Medical Genetics and Genomics/Association for Molecular Pathology guidelines.

Hemophagocytic lymphohistiocytosis due to Streptococcus suis in a 12-year-old girl: A case report.

RATIONALE: Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening hyperinflammatory syndrome that can be caused by bacterial infection. Streptococcus suis (S. suis) is a zoonotic pathogen that can cause severe disease in both pigs and humans. We report the first-ever documented case of HLH secondary to S. suis infection. PATIENT CONCERNS: A 12-year-old girl presented with fever, rash, hepatosplenomegaly, pancytopenia, and elevated levels of ferritin and soluble CD25. Bone marrow examination revealed hemophagocytosis. Blood culture was positive for S. suis. DIAGNOSIS: A diagnosis of hemophagocytic syndrome due to S. suis was established. INTERVENTIONS: We treated the patient with intravenous immunoglobulin, intravenous imipenem, and supportive care. OUTCOMES: The patient eventually showed complete recovery. LESSONS: Inflammatory response plays an important role in S. suis infection. Aberrant inflammatory response to S. suis infection may induce HLH. This case report illustrates that early definitive diagnosis and prompt treatment is a key imperative in patients with suspected S. suis infection.

Synergistic anti-leukemic interactions between panobinostat and MK-1775 in acute myeloid leukemia ex vivo.

MK-1775 is the first-in-class selective Wee1 inhibitor which has been demonstrated to synergize with CHK1 inhibitors in various malignancies. In this study, we report that the pan-histone deacetylase inhibitor (HDACI) panobinostat synergizes with MK-1775 in acute myeloid leukemia (AML), a malignancy which remains a clinical challenge and requires more effective therapies. Using both AML cell line models and primary patient samples, we demonstrated that panobinostat and MK-1775 synergistically induced proliferation arrest and cell death. We also demonstrated that panobinostat had equal anti-leukemic activities against primary AML blasts derived from patients either at initial diagnosis or at relapse. Interestingly, treatment with panobinostat alone or in combination with MK-1775 resulted in decreased Wee1 protein levels as well as downregulation of the CHK1 pathway. shRNA knockdown of CHK1 significantly sensitized AML cells to MK-1775 treatment, while knockdown of Wee1 significantly enhanced both MK-1775- and panobinostat-induced cell death. Our results demonstrate that panobinostat synergizes with MK-1775 in AML cells, at least in part through downregulation of CHK1 and/or Wee1, providing compelling evidence for the clinical development of the combination treatment in AML.

Single nucleotide polymorphisms in non-coding region of the glucocorticoid receptor gene and prednisone response in childhood acute lymphoblastic leukemia.

Poor prednisone response predicts an inferior outcome in pediatric acute lymphoblastic leukemia (ALL) in Berlin-Frankfurt-Münster (BFM) treatment protocols. Here, we investigated five single nucleotide polymorphisms (SNPs) in both the coding and non-coding regions of the glucocorticoid receptor (GR) gene, and analyzed their association with prednisone responsiveness in vivo in 63 pediatric patients with ALL in China. Of the five SNPs, the rs41423247 and rs7701443 polymorphisms were significantly associated with prednisone response at the allelic level (rs41423247 odds ratio [OR] = 9.58; 95% confidence interval [CI]: 1.23-74.21; p = 0.01; rs7701443 OR = 3.12; 95% CI: 1.08-9; p = 0.02). Two polymorphisms (rs6189/6190 and rs6198) were not observed in the study cohort. Haplotypes composed of CCC alleles and TCG alleles at three loci (rs7701443, Tth111I and BclI) were both associated with prednisone response (p = 0.013; p = 0.028). Our results suggested that polymorphisms in the non-coding region of the GR gene were associated with prednisone response in vivo in pediatric ALL in Han Chinese.

CHK1 plays a critical role in the anti-leukemic activity of the wee1 inhibitor MK-1775 in acute myeloid leukemia cells.

BACKGROUND: Acute myeloid leukemia (AML) remains a difficult disease to treat and requires new therapies to improve treatment outcome. Wee1 inhibitors have been used to prevent activation of the G2 cell cycle checkpoint, thus enhancing the antitumor activity of DNA damaging agents. In this study, we investigated MK-1775 in AML cell lines and diagnostic blast samples to identify sensitive subtypes as well as possible mechanisms of resistance. METHODS: In vitro MK-1775 cytotoxicities of AML cell lines and diagnostic blasts were measured using MTT assays. The effects of MK-1775 on cell cycle progression and related proteins were determined by propidium iodide (PI) staining and flow cytometry analysis and Western blotting. Drug-induced apoptosis was determined using annexin V/PI staining and flow cytometry analysis. RESULTS: We found that newly diagnosed and relapsed patient samples were equally sensitive to MK-1775. In addition, patient samples harboring t(15;17) translocation were significantly more sensitive to MK-1775 than non-t(15;17) samples. MK-1775 induced apoptosis in both AML cell lines and diagnostic blast samples, accompanied by decreased phosphorylation of CDK1 and CDK2 on Tyr-15 and increased DNA double-strand breaks (DSBs). Time-course experiments, using AML cell lines, revealed a time-dependent increase in DNA DSBs, activation of CHK1 and subsequent apoptosis following MK-1775 treatment, which could be attenuated by a CDK1/2 inhibitor, Roscovitine. Simultaneous inhibition of CHK1 and Wee1 resulted in synergistic anti-leukemic activity in both AML cell lines and primary patient samples ex vivo. CONCLUSIONS: Our study provides compelling evidence that CHK1 plays a critical role in the anti-leukemic activity of MK-1775 and highlights a possible mechanism of resistance to MK-1775. In addition, our study strongly supports the use of MK-1775 to treat both newly diagnosed and relapsed AML, especially cases with t(15;17) translocation, and supports the development of combination therapies with CHK1 inhibitors.