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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]

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]