The bone marrow microenvironment plays an important role in the development and progression of AML. Leukemia stem cells are in a hypoxic condition, which induces the expression of HIF-1α. Aberrant activation of HIF-1α is implicated in the poor prognosis of patients with acute myeloid leukemia (AML). Herein, we investigated the expression of HIF-1α in AML and tested 2-methoxyestradiol (2ME2) as a candidate HIF-1α inhibitor for the treatment of AML. We found that HIF-1α was overexpressed in AML. HIF-1α suppression by 2ME2 significantly induced apoptosis of AML cells, and it outperformed traditional chemotherapy drugs such as cytarabine. At the same time, 2ME2 downregulated the transcriptional levels of VEGF, GLUT1 and HO-1 in cellular assays. Additionally, 2ME2 displayed antileukemia activity in bone marrow blasts from AML patients, but showed little effect on normal cells. 2ME2-induced activation of mitochondrial apoptotic pathway is mediated by reactive oxygen species (ROS), which decreased the slight effect of drug on normal cells. Our data show that supression of HIF-1α expression significantly reduced the survival of AML cell lines, suggesting that 2ME2 may represent a powerful therapeutic approach for patients with AML.

Diffuse large B-cell lymphoma (DLBCL) is the most common type of adult lymphoma. It is a group of malignant tumors with a large number of clinical manifestations and prognoses. Therefore, it is necessary to explore its unknown potential therapeutic targets. Histone deacetylase inhibitor (HDACi) is a novel drug for the treatment of DLBCL, however pan-HDACis cannot be ignored because of their clinical efficacy. By contrast, specific HDACi is well-tolerated, and LMK-235 is a novel HDACi that is a specific inhibitor of HDAC4 and HDAC5. In this study, we investigated the up-regulation of BCLAF1 through NF-κB signaling pathways in LMK-235, mediating the apoptosis of two diffuse large B-cell lymphoma cell lines, OCI-LY10 and OCI-LY3. Further studies showed that BCLAF1 expression was increased in DLBCL cells after treatment with the NF-κB inhibitor Bay11-7082. The combination of Bay11-7082 and siRNA si-HDAC4 significantly increased BCLAF1 expression and further increased apoptosis. These results indicate that BCLAF1 plays an important role in LMK-235-mediated apoptosis and may be a potential target for the treatment of diffuse large B-cell lymphoma.

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Multiple myeloma (MM) is a hematological malignancy that is characterized by the clonal expansion of plasma cells in the bone marrow. Histone deacetylases (HDACs) represent a new type of molecular targeted therapy for different types of cancers and promising targets for myeloma therapy. We showed that HDAC3 mRNA and protein levels of CD138 mononuclear cells from MM patients were higher than those in healthy donors. Therefore, we investigated the effects of a novel class I HDAC inhibitor BG45 on MM cells in vitro. BG45 downmodulated heme oxygenase 1 (HO-1) when class I HDACs decreased in MM cells. HO-1 is a target for the treatment of MM. Moreover, BG45 induced hyperacetylation of histone H3 and inhibited the growth, especially the apoptosis of MM cell lines. Treatment with BG45 induced apoptosis by downregulating bcl-2 and Bcl-xl, upregulating Bax and other antiapoptotic proteins and activating poly(ADP-ribose)polymerase, and decreasing protein levels of p-JAK2 and p-STAT3. These effects were partly blocked by HO-1. Correspondingly, BG45 led to an accumulation in the G0/G1 phase, accompanied by decreased levels of CDK4 and phospho-retinoblastoma protein, an increased level of p21, and a moderately reduced level of CDK2. Clinical use of single agents was limited because of toxic side effects and drug resistance. However, combining BG45 with lenalidomide exerted synergistic effects. In conclusion, we verified the potent antimyeloma activity of this novel HDAC inhibitor and that the combination of BG45 and lenalidomide is a new method for MM treatment. Thus, BG45 may be applicable to the treatment of MM and other hematological malignancies.

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Acute myeloid leukemia (AML) is the most common type of acute leukemia in adults with poor prognosis. Especially for AML-M5 type, due to the strong cell migration ability, the possibility of extramedullary invasion is large and widespread, which leads to poor therapeutic effect. Previous studies have found that protein arginine methyltransferase 5 (PRMT5) could promote the proliferation and differentiation of leukemic cells in AML, but its regulation on the invasive ability of AML cells remains unclear. This study was designed to explore the role of PRMT5 in regulating the invasion of AML cells and to investigate the mechanisms. Patient samples were collected for detection of PRMT5 expression level. AML cells were used for exploring the function of PRMT5. The results of clinical samples showed that the expression of PRMT5 was significantly increased in newly diagnosed and recurrent AML patients, and the expression of leukocyte immunoglobulin-like receptor B4 (LILRB4) was positively correlated with the level of PRMT5. In the cell experiment in vitro, we found that when PRMT5 was knocked down, the invasion, migration, and adhesion capacities of MV-4-11 cells and THP-1 cells were decreased, and the mRNA and protein levels of LILRB4 were also decreased. Moreover, we screened related signaling pathways and found that PRMT5 affected the expression of downstream LILRB4 by activating mTOR pathway, which in turn enhanced the invasive ability of AML cells. Taken together, PRMT5 plays an important role in the invasion of AML, which acts via regulating the expression of LILRB4. PRMT5 could act as a potential therapeutic candidate for AML.

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OBJECTIVE: Fenretinide is reported to induce NR4A1-associated apoptosis in several types of cancer cells. However, it remains unclear about its specific role and the underlying mechanism in acute myeloid leukemia (AML). Therefore, this study aimed to explore the role and mechanism of fenretinide-induced apoptosis in AML.METHOD: Firstly, the NR4A1 mRNA level in the newly diagnosed AML patients was measured, then AML cells were treated with fenretinide at various time points and doses, and cell viability was investigated by using the cell-counting kit-8 (CCK-8) assay. Additionally, apoptosis and cell cycles were analyzed by using flow cytometry. Moreover, siNR4A1 was utilized to knockdown NR4A1 expression, and leptomycin B (LMB) was adopted to inhibit the nuclear export; afterwards, the apoptosis rate and expression of apoptotic proteins in AML cells were detected. In addition, the expression levels of NR4A1 in the nuclei and mitochondria of fenretinide-treated AML cells were also measured. Meanwhile, the interaction between NR4A1 and Bcl-2, as well as the Bcl-2 transformation, was also examined. The anti-leukemic effect of fenretinide on NOD/SCID mice was also determined through subcutaneous injection of HL-60 cells.RESULTS: NR4A1 expression in AML patients was markedly down-regulated compared with that in normal donors. Fenretinide induced the expression of NR4A1 and mitochondria-mediated apoptotic pathway-associated proteins in a time- and concentration-dependent manner. Importantly, both siNR4A1 alone or the combination of fenretinide with LMB could attenuate the fenretinide-induced apoptosis and expression of apoptotic proteins. Under the action of fenretinide, the NR4A1 protein expression was down-regulated in nuclear extracts whereas up-regulated in mitochondrial extracts. At the same time, fenretinide promoted NR4A1 translocation from nuclei into mitochondria, and enhanced the interaction between NR4A1 and Bcl-2, thereby exposing the BH3 domain of Bcl-2 to exert the anti-apoptotic effect. Moreover, fenretinide also exhibited an anti-leukemic effect and induced NR4A1 expression in the AML mouse model.CONCLUSIONS: Fenretinide exerts an obvious effect on AML cells both in vitro and in vivo. Besides, the NR4A1-mediated signaling pathway is highly involved in the fenretinide-induced apoptosis of AML cells.