benzyloxycarbonylleucyl-leucyl-leucine-aldehyde and Precursor-Cell-Lymphoblastic-Leukemia-Lymphoma

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.. 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.. 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.. 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.

Topics: Adolescent; Adult; Aged; Apoptosis; Bone Marrow Cells; Child; Child, Preschool; Drug Synergism; Female; G2 Phase Cell Cycle Checkpoints; Histone Deacetylases; Humans; Infant; Janus Kinases; Leupeptins; Male; Middle Aged; Precursor Cell Lymphoblastic Leukemia-Lymphoma; RNA Interference; RNA, Small Interfering; Signal Transduction; STAT3 Transcription Factor; Ubiquitin-Protein Ligases; Up-Regulation; Young Adult

Recent research indicates that the proteasome is one of the non-caspase proteases involved in apoptotic signaling pathways. Nuclear factor-kappaB (NF-kappaB) activation, one of the key factors in apoptosis, can be prevented through abrogation of IkappaBalpha degradation by proteasome inhibition. We have investigated the effects of the proteasome inhibitors carbobenzoxyl-L-leucyl-L-leucyl-L-leucinal (MG132) and N-acetyl-L-leucinyl-L-leucinyl-L-norleucinal (LLnL) on apoptosis and NF-kappaB activation induced by etoposide, using a human leukemia cell line (U937) and leukemia blasts freshly isolated from patients with acute leukemia. Pretreatment of U937 cells with MG132 or LLnL inhibited etoposide-induced morphological apoptosis and caspase-3 activation. Furthermore, MG132 or LLnL prevented NF-kappaB activation and IkappaBalpha degradation, but not IkappaBalpha phosphorylation at Ser32. Other inhibitors of NF-kappaB activation, including pyrrrolidine dithiocarbamate (an antioxidant) and the peptide SN50 (an inhibitor of translocation of activated NF-kappaB into the nucleus), also attenuated etoposide-induced apoptosis. In leukemia blasts, although proteasome inhibitors suppressed NF-kappaB activation induced by etoposide, they were unable to prevent morphological apoptosis. Moreover, proteasome inhibitors by themselves caused apoptosis in leukemia blasts at the concentrations employed in this study. These results suggest that the role that NF-kappaB plays in apoptosis induced by etoposide in a human leukemia cell line may be different from the role it plays in freshly isolated leukemia blasts.

Topics: Antineoplastic Agents, Phytogenic; Apoptosis; Caspase 3; Caspases; Cysteine Endopeptidases; Cysteine Proteinase Inhibitors; DNA-Binding Proteins; Etoposide; Humans; I-kappa B Proteins; Leupeptins; Multienzyme Complexes; NF-kappa B; NF-KappaB Inhibitor alpha; Phosphorylation; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Proteasome Endopeptidase Complex; Tumor Cells, Cultured; U937 Cells