Sha Yi

Betulinic acid inhibits autophagic flux and induces apoptosis in human multiple myeloma cells in vitro

Aim:To investigate the effects of betulinic acid (BA) on apoptosis and autophagic flux in multiple myeloma cells and the relationship between the two processes.Methods:The proliferation of human multiple myeloma KM3 cells was measured with MTT assay. FITC/PI double-labeled flow cytometry (FCM) and Hoechst 33258 staining were used to analyze the cell apoptosis. Caspase 3, PARP, Beclin1, LC3-II, and P62 were detected using Western blotting.Results:Treatment of KM3 cells with BA (5−25 μg/mL) suppressed the cell proliferation in time- and dose-dependent manners. The IC50 values at 12, 24, and 36 h were 22.29, 17.36, and 13.06 μg/mL, respectively. BA treatment dose-dependently induced apoptosis of KM3 cells, which was associated with the activation of caspase 3. However, Z-DEVD-FMK, a specific inhibitor of caspase 3, did not decrease, but rather sensitized the cells to BA-induced apoptosis, suggesting an alternative mechanism involved. On other hand, BA treatment dose-dependently increased the accumulation of LC3-II and P62 in KM3 cells, representing the inhibition of autophagic flux. Furthermore, BA treatment dose-dependently downregulated the expression of Beclin 1, an important inducer of autophagy, in KM3 cells. In the presence of BA, Z-DEVD-FMK induced autophagy and increased the amount of LC3-II in KM3 cells, which may occur via attenuating BA-induced decrease in the level of Beclin 1. Similarly, rapamycin, an autophagy inducer, increased the amount of LC3-II in KM3 cells. In the presence of BA, rapamycin caused further increase in the amount of LC3-II. Furthermore, rapamycin sensitized BA-treated KM3 cells to apoptosis.Conclusion:The results demonstrate that BA induces apoptosis and blocks autophagic flux in KM3 cells. Furthermore, in addition to activation of caspase 3, the inhibition of autophagic flux also contributes to the BA-mediated apoptosis of KM3 cells.

Oridonin induces NPM mutant protein translocation and apoptosis in NPM1c+ acute myeloid leukemia cells in vitro

Aim:Skewed cytoplasmic accumulation of NPM mutant protein (NPM1c+) is close related to leukemia pathogenesis. The aim of this study was to investigate whether oridonin, a diterpenoid isolated from the Chinese traditional medicine Rabdosia rubescens, was able to interfere with NPM1c+ protein trafficking and induce apoptosis in NPM1c+ acute myeloid leukemia cells in vitro.Methods:OCI-AML3 cell line harboring a NPM1 gene mutation was examined. Cell growth was detected by MTT assay. Cell apoptosis was evaluated using flow cytometry and Hoechst 33258 staining. The expression and subcellular localization of relevant proteins were detected by Western blot and immunofluorescent staining. The mRNA expression was detected by RT-PCR.Results:Oridonin (2–12 μmol/L) dose-dependently inhibited the viability of OCI-AML3 cells (the IC50 value was 3.27±0.23 μmol/L at 24 h). Moreover, oridonin induced OCI-AML3 cell apoptosis accompanied by activation of caspase-3 and nuclear translocation of NPM1c+ protein. Oridonin did not change the expression of Crm1 (the export receptor for nuclear export signal-containing proteins), but induced nuclear translocation of Crm1. Oridonin markedly increased the expression of nucleoporin98 (Nup98), which had an important role in Crm1-mediated nuclear protein export, and induced nuclear accumulation of Nup98. Furthermore, oridonin markedly increased the expression of p14arf and p53.Conclusion:In NPM1c+ leukemia cells, oridonin induces NPM1c+ protein translocation into the nucleus possibly via nuclear accumulation of Crm1; the compound markedly increases p53 and p14arf expression, which may contribute to cell apoptosis.

Deguelin, a selective silencer of the NPM1 mutant, potentiates apoptosis and induces differentiation in AML cells carrying the NPM1 mutation.

Nucleophosmin (NPM1) is a multifunctional protein that functions as a molecular chaperone, shuttling between the nucleolus and the cytoplasm. In up to one third of patients with acute myeloid leukemia, mutation of NPM1 results in the aberrant cytoplasmic accumulation of mutant protein and is thought to be responsible for leukemogenesis. Deguelin, a rotenoid isolated from several plant species, has been shown to be a strong anti-tumor agent. Human leukemia cell lines were used for in vitro studies. Drug efficacy was evaluated by apoptosis and differentiation assays, and associated molecular events were assessed by Western blot. Gene silencing was performed using small interfering RNA (siRNA). Deguelin exhibited strong cytotoxic activity in the cell line of OCI-AML3 and selectively down-regulated the NPM1 mutant protein, which was accompanied by up-regulation of the activity of caspase-6 and caspase-8 in high concentrations. Deguelin induced differentiation of OCI-AML3 cells at a nontoxic concentration which was associated with a decrease in expression of activated caspase-8, p53, p21, and the 30-kD form of CCAAT/enhancer binding protein α (C/EBPα), whereas no effects were found in OCIM2 cells expressing NPM-wt. Moreover, treatment with siRNA in the NPM mutant cell line OCI-AML3 decreased expression of p53, p21, pro-caspase-8, and the 30-kD form of C/EBPα, and it inhibited proliferation and induced differentiation of the OCI-AML3 cells. In conclusion, deguelin is a potent in vitro inhibitor of the mutant form of NPM1, which provides the molecular basis for its anti-leukemia activities in NPM1 mutant acute myeloid leukemia cells.

Steroid receptor coactivator-3 is a pivotal target of gambogic acid in B-cell Non-Hodgkin lymphoma and an inducer of histone H3 deacetylation.

Gambogic acid (GA), the active ingredient from gamboges, has been verified as a potent anti-tumor agent in many cancer cells. Nevertheless, its function in lymphoma, especially in B-cell Non-Hodgkin lymphoma (NHL), remains unclear. Amplification and/or overexpression of steroid receptor coactivator-3 (SRC-3) have been detected in multiple tumors and have confirmed its critical roles in carcinogenesis, progression, metastasis and therapy resistance in these cancers. However, no clinical data have revealed the overexpression of SRC-3 and its role in B-cell NHL. In this study, we demonstrated the anti-tumor effects of GA, which included cell growth inhibition, G1/S phase cell cycle arrest and apoptosis in B-cell NHL. We also verified that SRC-3 was overexpressed in B-cell NHL in both cell lines and lymph node samples from patients. The overexpressed SRC-3 was a central drug target of GA, and its down-regulation subsequently modulated down-stream gene expression, ultimately contributing to apoptosis. Silencing SRC-3 decreased the expression of Bcl-2, Bcl-6 and cyclin D3, but not of NF-κB and IκB-α. GA treatment did not inhibit the activation of AKT signaling pathway, but induced the deacetylation of histone H3 at lysine 9 and lysine 27. Down-regulated SRC-3 was observed to interact with more HDAC1 to mediate the deacetylation of H3. As the component of E3 ligase, Cullin3 was up-regulated and mediated the degradation of SRC-3. Our results demonstrate that GA is a potent anti-tumor agent that can be used for therapy against B-cell NHL, especially against those with an abundance of SRC-3.

Downregulation of nucleoporin 88 and 214 induced by oridonin may protect OCIM2 acute erythroleukemia cells from apoptosis through regulation of nucleocytoplasmic transport of NF-κB

Oridonin has been utilized for the treatment of various human diseases due to its anti-inflammatory, antibacterial and antitumor effects. However, the precise mechanisms induced by oridonin in human erythroleukemia are yet to be clarified. The present study aimed to elucidate possible oridonin-induced apoptotic mechanisms in OCIM2 cells, as well as the possible mechanisms whereby OCIM2 cells are relatively resistant to oridonin. Results in the present study showed that oridonin significantly inhibited OCIM2 and OCI-AML3 cell proliferation in a dose- and time-dependent manner, while expressing a much higher IC50 in OCIM2, compared to OCI-AML3. These results also indicated that oridonin induced OCIM2 cell apoptosis, associated with p65 and Bax, while activating caspases-9, -6 and -3. However, p65 was only partly translocated into the nucleus, while most of the p65 was retained in the cytoplasm. Moreover, nucleoporin 214 (Nup214) and nucleoporin 88 (Nup88) were downregulated at the transcriptional and protein levels, subsequent to oridonin treatment. Taken together, these data suggest that oridonin has the potential to induce OCIM2 cell-apoptosis, involving NF-κB activation, whereas the downregulation of Nup88 and Nup214 may protect OCIM2 through the regulation of the nucleocytoplasmic transport of p65.

Nontoxic-dose of Deguelin Induce NPMc+ AML Cell Differentiation by Selectively Targeting Mt NPM1/SIRT1 Instead of HDAC1/3

AML with Mt NPM1 has relatively good responses to induction therapy. However, a proportion of NPMc+ AML cells cannot be cleared by conventional treatments. Therefore, we determined the therapeutic efficacy of deguelin that has demonstrated extensive biological activity with low toxicity. We previously reported that deguelin selectively reduces Mt NPM1, as well as induces differentiation and potentiates apoptosis in NPMc+ AML cells. Nevertheless, little information is available regarding the mechanism of deguelin-induced differentiation. Here, we investigated the role of deguelin in the induction of NPMc+ AML cell differentiation. Deguelin at the nontoxic concentration of 2 μM strongly inhibited cell growth but reduced apoptosis in OCI-AML3 cells carrying Mt NPM1, whereas the antiproliferative effect was minimal in OCIM2 cells harboring Wt NPM1. Compared with OCIM2 cells that showed no response, deguelin-treated OCI-AML3 cells exhibited the morphological features of granulocytic/monocytic differentiation, increased expression of differentiation antigens, and a nitroblue tetrazolium reduction activity. Induction of differentiation was associated with downregulation of Mt NPM1 and SIRT1, but not Wt NPM1, which was accompanied by an increase in CEBPβ and G-CSFR expression, and further confirmed by sh-Mt NPM1 and sh-SIRT1. sh-Mt NPM1 treatment reduced SIRT1 expression, but did not change HDAC1/3 levels, suggesting that the decline of SIRT1 was partially accountable for the deguelin-induced, Mt-NPM1-related differentiation. Moreover, Mt NPM1 overexpression blocked deguelin-induced cell differentiation. Lastly, we showed that deguelin reduced the expression of Mt NPM1 via the ubiquitin-proteasome pathway. Taken together, our results suggest that deguelin may be a therapeutic candidate for NPMc+ AML.

Deguelin induced differentiation of mutated NPM1 acute myeloid leukemia in vivo and in vitro.

Nucleophosmin (NPM1), a restricted nucleolar localization protein, shuttles between the nucleus and the cytoplasm. Mutated (Mt)-NPM1 protein, which has aberrant cytoplasmic dislocation of nucleophosmin, occurs in approximately one-third of acute myeloid leukemia cases. Deguelin, a rotenoid isolated from several plant species, is a strong antitumor agent. NOD/SCID mice xenografted with human Mt-NPM1 OCI/AML3 cell lines served as in-vivo models. Wright–Giemsa staining and flow cytometry analysis were used for differentiation assays. Associated molecular events were assessed by western blot and histological analyses. Kaplan–Meier estimates were used to calculate survival. Deguelin toxicity in mice was assessed by immunohistochemistry staining and serum markers. Clinical samples were differentiated by flow cytometry analysis. Deguelin induced differentiation by downregulating the Mt-NPM1 protein levels, which was accompanied by a decrease in SIRT1, p21, and HDAC1 and an increase in CEBP&bgr; and granulocyte colony-stimulating factor receptor protein expression levels. A low-deguelin dose prolonged survival compared with the control group, and there were no apparent lesions to the brain, liver, heart, and kidney in vivo. In clinical samples, deguelin induced the differentiation of fresh blasts with Mt-NPM1 protein, but not with the wild-type NPM1 protein. Taken together, these findings further provide new evidence that the Mt-NPM1 protein plays an important role in inducing differentiation in vivo and in vitro. Mutated NPM1 protein may be a therapeutic target of deguelin in acute myeloid leukemia with the NPM1 mutation.

Triptolide Induces Cell Apoptosis by Targeting H3K4me3 and Downstream Effector Proteins in KM3 Multiple Myeloma Cells

As the principal active ingredient in the Chinese herb Tripterygium wilfordii Hook.F (TwHF), triptolide has been shown to have very strong antitumor properties. The trimethylation of lysine 4 on histone H3 (H3K4me3) has been proposed to promote gene expression, and the accumulation of H3K4me3 at the transcriptional start sites of oncogenes is involved in carcinogenesis. To identify the association between the reduction of H3K4me3 and the apoptosis of MM cells induced by triptolide, we investigated the global patterns of H3K4me3 occupancy in the MM cell genome. Combined analyses using ChIP-on-chip and western blotting showed that H3K4me3 were highly enriched on the gene promoters of c-Myc and VEGFA and were associated with the up-regulation of both genes. Treatment of KM3 cells with triptolide and siRNA targeting ASH2L reduced the expression of c-Myc and VEGFA. These results suggest that triptolide can down-regulate c-Myc and VEGFA expression by blocking the accumulation of H3K4me3 on their promoters,and thus play an important role in anti-MM mechanism.