Search

Abstract Objectives The serine/threonine PIM protein kinases are critical regulators of tumorigenesis in multiple cancers. However, whether PIMs are potential therapeutic targets for treating B-cell acute lymphocytic leukemia (B-ALL) remains unclear. Therefore, here, PIM expression was detected in B-ALL patients and the effects of SMI-4a, a pan-PIM small molecule inhibitor, were investigated in B-ALL cells. Methods PIM1 and PIM2 expression in 26 newly diagnosed B-ALL cases was detected by real-time PCR and Western blot. B-ALL cells were treated with varied SMI-4a doses and the viability of treated cells was investigated using a cell-counting kit-8 (CCK-8) assay. Apoptosis and cell cycles were analyzed by flow cytometry. Western blot analysis was then used to explore the expression of apoptosis-related proteins and the JAK2/STAT3 pathway. Results PIM1 and 2 were overexpressed in B-ALL patients with high HO-1 level. SMI-4a induced decreases in PIMs and HO-1 expressions and inhibited B-ALL cell viability. Treatment with SMI-4a induced apoptosis by downregulating Bcl-2, upregulating Bax and other antiapoptotic proteins, and decreasing protein levels of p-JAK2 and p-STAT3. In addition, upregulation of HO-1 alleviated decrease in p-JAK2 and p-STAT3 expression, reduced SMI-4a-induced apoptosis of B-ALL cells, and influenced B-ALL cell survival. Conclusions PIMs were highly expressed in B-ALL patients. SMI-4a inhibited B-ALL proliferation and induced apoptosis via the HO-1-mediated JAK2/STAT3 pathway. SMI-4a might be applicable for treatment of B-ALL cells. [ABSTRACT FROM AUTHOR]

Leptin showed different apoptosis regulation effects on the chondrocytes from tibial and vertebral epiphyseal plates. However, the mechanism is still unclear. In this study, we tested the protein profile of tibial and vertebral epiphyseal plate chondrocytes with and without leptin stimulation by mass spectrometry and found that the histone acetylation level of tibial chondrocytes was decreased after leptin treatment, while increased in vertebral epiphyseal plates. COIP assay showed that leptin promoted H3, H4 histone acetylation by recruiting CREB binding protein (CBP)/P300 to activate histone acetyl transferases (HATs) activity in vertebral disc chondrocytes. But in tibial plate cartilage cells, leptin did not recruit CBP and p300, thus differently affect the apoptosis of epiphyseal plate chondrocytes. Through explored the mechanism of histone acetylation modulated by leptin, and its effect on cartilage cell apoptosis and cell cycle regulation, This provides a novel target therapy possibility therapeutic approach to for the related disease. [ABSTRACT FROM AUTHOR]

Purpose: HDAC3, which is associated with smurf2, has been shown to be associated with poor prognosis in B-ALL. This study examined the efficacy of targeting HDAC3 combined with MG-132 as a possible therapeutic strategy for B-ALL patients. Methods: Real-time PCR and western blot were used to measure the expression of smurf2 and HDAC3 from B-ALL patients bone marrow samples. Sup-B15 and CCRF-SB cells were treated with MG-132, small interfering RNA of smurf2 or HDAC3. A plasmid designed to up-regulate smurf2 expression was transfected into B-ALL cells. Flow cytometry and western blot were used to measure variation due to these treatments in terms of apoptosis and cell cycle arrest. Results: Expression of Smurf2 and HDAC3 mRNA were inversely related in B-ALL patients. Up-regulation of smurf2 or MG-132 influenced HDAC3, further inhibiting the JAK/signal transducer and activator of transcription 3 (STAT3) signal pathway and inducing apoptosis in B-ALL cells. When we treated Sup-B15 and CCRF-SB cells with siHDAC3 and MG-132 for 24 h, silencing HDAC3 enhanced the apoptosis rate induced by MG-132 in B-ALL cells and further inhibited the JAK/STAT3 pathway. Furthermore, MG-132 was observed to cause G2/M phase arrest in B-ALL cells and inhibited the JAK/STAT3 pathway, leading to apoptosis. Conclusions: Silencing of HDAC3 enhanced the sensitivity of B-ALL cells to MG-132. The combination of targeting HDAC3 and MG-132 may provide a new avenue for clinical treatment of acute B lymphocytic leukaemia and improve the poor survival of leukaemia patients. [ABSTRACT FROM AUTHOR]

Abstract Aims Histone deacetylase inhibitors (HDACis) are promising anticancer drugs that open new areas of epigenetic drug discovery. Multiple myeloma (MM) is a malignant tumor of the blood system that is difficult to cure and often relapses. Here, we investigated the in vitro effects of a novel HDACi, LMK-235, on MM cells, and explored the underlying mechanisms. Main methods Real-time PCR and western blot were used to measure the expression of HDAC4 and HO-1 in MM cells treated with LMK-235. si-RNA was used to transfect MM cells. Hemin or ZnPP was combined to regulate heme oxygenase-1 (HO-1), and a pathway inhibitor was added to measure changes in the JNK/AP-1 signaling pathway. Apoptosis and proliferation were assessed by flow cytometry and CCK-8 assay, respectively. Key findings We found that LMK-235, a selective inhibitor of class IIA HDAC4/5, induced apoptosis of MM cells by downregulating HO-1 that is closely related to HDAC4. LMK-235 increased phosphorylation of JNK and c -Jun in MM cells. Downregulation of HO-1 expression in combination with LMK-235 expression further activated phosphorylation of JNK and c-Jun and induced apoptosis in MM cells. When the JNK inhibitor SP600125 was used in combination, the apoptosis phenomenon was reversed. However, when HO-1 was upregulated, LMK-235-mediated phosphorylation of JNK and c-Jun was inhibited, and apoptosis of MM cells began to decrease. Significance These data suggest that LMK-235 has potent anti-myeloma activity through regulation of HO-1-induced apoptosis via the JNK/AP-1 pathway. This provides a new concept for the treatment of multiple myeloma. [ABSTRACT FROM AUTHOR]

Abstract Aims The aim of this study was to investigate the combinatorial effects of IM and a novel HDAC inhibitor AR-42 on the proliferation, apoptosis, cell cycle arrest, migration and invasion of CML cells, and to explore the underlying mechanisms. Main methods We assessed the ability of the pan-HDAC inhibitor AR-42 and IM, to synergistically kill CML cells by survival, apoptosis, cell cycle, migration and invasion assays in vitro. We also assessed the HDAC1 expression by Western blot and real-time PCR. Synergy was calculated using combinatorial indices as determined by CalcuSyn. Key findings We found that Combining AR-42 with IM synergistically inhibited CML cell proliferation, enhanced cell apoptosis, induced cell cycle arrest, and decreased migration and invasion. The expression of HDAC1 in K562R cells was higher than that in K562 cells. AR-42 enhanced IM-induced HDAC1 expression inhibition in K562 and K562R cells. Importantly, HDAC1 overexpression partly reversed the apoptosis, G2/M phase arrest, migration and invasion of K562 cells induced by the combination of IM with AR-42. Moreover, HDAC1 knockdown partly promoted K562R cell apoptosis and G2/M phase arrest, migration and invasion induced by IM in combination with AR-42. Significance In conclusion, AR-42 may increase the sensitivity of CML cells to IM and reverse IM resistance by regulating HDAC1 expression. This study provides new insights into the effects of combined therapy using IM and pan-HDAC inhibitor AR-42, paving the way for overcoming IM resistance in clinical practice. [ABSTRACT FROM AUTHOR]

Inhibition of histone deacetylase (HDAC) is a promising therapeutic strategy for various hematologic cancers. Panobinostat has been approved for treating patients with multiple myeloma (MM) by the FDA. Since the mechanism for the resistance of panobinostat to MM remains elusive, we aimed to clarify this mechanism and the synergism of panobinostat with lenalidomide. The mRNA and protein of transcription factor IRF4 were overexpressed in CD138 + mononuclear cells from MM patients compared with in those from healthy donors. Given that direct IRF4 inhibitors are clinically unavailable, we intended to explore the mechanism by which IRF4 expression was regulated in MM. Heme oxygenase-1 (HO-1) promotes the growth and drug resistance of various malignant tumors, and its expression is positively correlated with IRF4 mRNA and protein expression levels. Herein, panobinostat induced acetylation of histone H3K9 and activation of caspase-3 in MM cells, being inversely correlated with the reduction of HO-1/IRF4/MYC protein levels. Adding Z-DEVD-FMK, a caspase-3 inhibitor, abolished the HO-1/IRF4 reduction by panobinostat alone or in combination with lenalidomide, suggesting that caspase-3-mediated HO-1/IRF4/MYC degradation occurred. Given that lenalidomide stabilized cereblon and facilitated IRF4 degradation in MM cells, we combined it with LBH589, an HDAC inhibitor. LBH589 and lenalidomide exerted synergistic effects, and LBH589 reversed the efficacy of lenalidomide on the resistance of CD138 + primary MM cells, in part due to simultaneous suppression of HO-1, IRF4 and MYC. The results provide an eligible therapeutic strategy for targeting MM depending on the IRF4 network and clinical testing of this drug combination in MM patients. [ABSTRACT FROM AUTHOR]

Although great efforts have been made to improve available therapies, the mortality rate of acute myeloid leukemia (AML) remains high due to poor treatment response and frequent relapse after chemotherapy. Leukemia stem cells (LSCs) are thought to account for this poor prognosis and relapse. Phosphoinositide-dependent kinase 1 (PDK1) is a critical regulator of the PI3K/Akt pathway and has been shown to be frequently activated in leukemia. However, the role of PDK1 in the regulation of LSCs in AML is still not clear. Using a PDK1 conditional deletion MLL-AF9 murine AML model, we revealed that the deletion of PDK1 prolonged the survival of AML mice by inducing LSC apoptosis. This was accompanied by the increased expression of the pro-apoptotic genes Bax and p53 and the reduced expression of Stat5 , which has been shown to be constitutively activated in leukemia. Thus, our findings suggest that PDK1 plays an essential role in maintaining LSCs. Further delineating the function of PDK1 in LSCs may provide a new strategy for the improved treatment of AML relapse. [ABSTRACT FROM AUTHOR]

Abstract: The Notch1 signaling pathway plays an essential role in cell growth and differentiation. Over-expression of the intracellular Notch1 domain (ICN1) in murine hematopoietic cells is able to induce robust T-cell acute lymphoblastic leukemia (T-ALL) in mice. Here we explored the drug sensitivity of T-ALL cells in two subpopulations of CD8+CD4+ and CD8+CD4− cells in Notch1-induced T-ALL mice. We found that Notch1 induced T-ALL cells could be decreased by chemotherapeutic drug cyclophosphamide (CTX). CD8+CD4− T-ALL cells were more sensitive to CTX treatment than CD8+CD4+ T-ALL cells. The percentage of apoptotic cells induced by CTX treatment was higher in CD8+CD4− T-ALL cells. T-ALL cells were also inhibited by inhibitor of mTORC1 rapamycin. CD8+CD4+ T-ALL cells were more susceptible to rapamycin treatment than CD8+CD4− T-ALL cells. Rapamycin treatment selectively arrested more CD8+CD4+ T-ALL cells at G0 phase of cell cycle. A combination of the two drugs significantly improved overall survival of T-ALL bearing mice when compared with CTX or rapamycin alone. These results indicated that CD8+CD4+ and CD8+CD4− leukemia cell populations had distinct drug sensitivity. [Copyright &y& Elsevier]