A comparative experimental study of the anaerobic treatment of food wastes using an anaerobic digester with a polyamide stirring rake or a stainless-steel stirring rake.

A low treatment capacity and unstable operation are the main drawbacks of the anaerobic digestion of food wastes. The present work improved the efficiency and stabilization of the anaerobic digestion of food wastes using digesters with a polyamide stirring rake (DPSR) and compared it to a traditional digester with a stainless-steel stirring rake (DSSSR). The DPSR had a higher reliability and produced 3.97 times the methane yield of DSSSR in batch experiments at high loading rates (105 VS/L). Uniform design experiments were applied to investigate the relationship between methane yield and the stirring factors of the DPSR. A regression analysis of the uniform design indicated that stirring factors synergistically affect methane yield. The experiment verifying the optimal conditions showed that in the DPSR with 82 r/min stirring intensity and 10 min/d stirring time, the first 20 days of methane yield (392.1 mL/g VS) achieved to 85.26% of the theoretically derived methane yield. In brief, in the anaerobic digestion of food wastes for high methane production and stable operation, the DPSR was more beneficial for the anaerobic digestion of food wastes than the DSSSR.

Mechanism of synergy of BH3 mimetics and paclitaxel in chronic myeloid leukemia cells: Mcl-1 inhibition.

Paclitaxel is an alternative chemotherapeutic agent for chronic myelogenous leukemia (CML) when primary or secondary resistance of tyrosine kinase inhibitors (TKI) is emerging, because paclitaxel could bypass the apoptotic deficiencies linked to p53 and fas ligand pathways in CML. However, high levels of Bcl-2 family proteins in CML could resist paclitaxel-induced apoptosis. Herein, we utilized two BH3 mimetics ABT-737 and S1 to study the potential of BH3 mimetics in combination with paclitaxel in treatment of CML cells and illustrated the mechanism by which BH3 mimetics synergize with paclitaxel. As a single agent, S1 could induce apoptosis in CML-derived cell line K562, whereas ABT-737 was largely ineffective. However, both of the two agents could efficiently synergize with paclitaxel through intrinsic apoptosis pathway. By using Bcl-2 siRNA, Bcl-XL siRNA or Mcl-1 siRNA, we found although each of the three members exhibited activities to block paclitaxel-induced apoptosis, Mcl-1 was the determinant for the synergistic effect between paclitaxel and ABT-737 or S1. Furthermore, paclitaxel/ABT737 synergized to drastically upregulate Bim to displace Bak from Mcl-1, whereas S1 directly binds Mcl-1 to release both Bim and Bak. As such, ABT-737 and S1 sensitized CML to paclitaxel by Mcl-1 inhibition, indirect inhibition through Bim antagonizing Mcl-1, or direct inhibition through binding to Mcl-1 itself. Finally, activation of JNK/Bim pathway was identified as the apical mechanism for ABT-737/paclitaxel synergism. Together, our results demonstrated potent synergy between BH3 mimetics and paclitaxel in the killing of CML cells and revealed an important role for Mcl-1 in mediating synergism by these agents.

A novel BH3 mimetic efficiently induces apoptosis in melanoma cells through direct binding to anti-apoptotic Bcl-2 family proteins, including phosphorylated Mcl-1.

The Bcl-2 family modulates sensitivity to chemotherapy in many cancers, including melanoma, in which the RAS/BRAF/MEK/ERK pathway is constitutively activated. Mcl-1, a major anti-apoptotic protein in the Bcl-2 family, is extensively expressed in melanoma and contributes to melanoma's well-documented chemoresistance. Here, we provide the first evidence that Mcl-1 phosphorylation at T163 by ERK1/2 and JNK is associated with the resistance of melanoma cell lines to the existing BH3 mimetics gossypol, S1 and ABT-737, and a novel anti-apoptotic mechanism of phosphorylated Mcl-1 (pMcl-1) is revealed. pMcl-1 antagonized the known BH3 mimetics by sequestering pro-apoptotic proteins that were released from Bcl-2/Mcl-1. Furthermore, an anthraquinone BH3 mimetic, compound 6, was identified to be the first small molecule to that induces endogenous apoptosis in melanoma cells by directly binding Bcl-2, Mcl-1, and pMcl-1 and disrupting the heterodimers of these proteins. Although compound 6 induced upregulation of the pro-apoptotic protein Noxa, its apoptotic induction was independent of Noxa. These data reveal the promising therapeutic potential of targeting pMcl-1 to treat melanoma. Compound 6 is therefore a potent drug that targets pMcl-1 in melanoma.

Resistance to BH3 mimetic S1 in SCLC cells that up-regulate and phosphorylate Bcl-2 through ERK1/2.

BACKGROUND AND PURPOSE: B cell lymphoma 2 (Bcl-2) is a central regulator of cell survival that is overexpressed in the majority of small-cell lung cancers (SCLC) and contributes to both malignant transformation and therapeutic resistance. The purpose of this work was to study the key factors that determine the sensitivity of SCLC cells to Bcl-2 homology domain-3 (BH3) mimetic S1 and the mechanism underlying the resistance of BH3 mimetics. EXPERIMENTAL APPROACHES: Western blot was used to evaluate the contribution of Bcl-2 family members to the cellular response of SCLC cell lines to S1. Acquired resistant cells were derived from initially sensitive H1688 cells. Quantitative PCR and gene silencing were performed to investigate Bcl-2 up-regulation. KEY RESULTS: A progressive increase in the relative levels of Bcl-2 and phosphorylated Bcl-2 (pBcl-2) characterized the increased de novo and acquired resistance of SCLC cell lines. Furthermore, acute treatment of S1 induced Bcl-2 expression and phosphorylation. We showed that BH3 mimetics, including S1 and ABT-737, induced endoplasmic reticulum (ER) stress and then activated MAPK/ERK pathway. The dual function of MAPK/ERK pathway in defining BH3 mimetics was illustrated; ERK1/2 activation leaded to Bcl-2 transcriptional up-regulation and sustained phosphorylation in naïve and acquired resistant SCLC cells. pBcl-2 played a key role in creating resistance of S1 and ABT-737 not only by sequestrating pro-apoptotic proteins, but also sequestrating a positive feedback to promote ERK1/2 activation. CONCLUSIONS AND IMPLICATIONS: These results provide significant novel insights into the molecular mechanisms for crosstalk between ER stress and endogenously apoptotic pathways in SCLC following BH3 mimetics treatment.

S1 kills MCF-7/ADR cells more than MCF-7 cells: A protective mechanism of endoplasmic reticulum stress.

Drug resistance in chemotherapy for breast cancer is associated with high levels of P-glycoprotein (P-gp) as well as endoplasmic reticulum (ER) stress. In this paper, we aimed to evaluate the efficacy of a pan-BH3 mimetic S1 on drug-resistant MCF-7/ADR cells, and the roles of S1-induced ER stress in cell death. S1 exhibited greater and faster mitochondrial apoptosis in MCF-7/ADR cells than in MCF-7 cells. We demonstrated by Bax/Bak activation and cyrochrome c release that the p-glycprotein had little influence on S1 entering cells and hitting its targets in MCF-7/ADR cells. An IRE1-mediated ER stress response followed by c-Jun N-terminal kinase (JNK) and extracellular signal-regulated protein kinase (ERK) activation was specifically induced by S1 in MCF-7 cells, but not in MCF-7/ADR cells. Coimmunoprecipitation and western blotting analysis determined that ER stress played a protective role in S1-induced apoptosis by triggering Bcl-2 phosphorylation, which grabbed more pro-apoptotic proteins. The synergism effect of ERK inhibitor PD98059 with S1 confirmed the protective role of ER stress. Defective ER stress in MCF-7/ADR cells confers the more sensitivity toward S1.

Design and application of a rigid quinazolone scaffold based on two-face Bim α-helix mimicking.

Based on our previous discovery of an anthraquinone scaffold mimicking two faces of Bim α-helix, we derived a quinazolone scaffold through structure simplification and optimization. It was inferred that a rigid bicyclic ring was necessary and efficient to maintain the two-faced binding mode. A novel dual inhibitor 6c [6,7,8-trihydroxy-3-(2-hydroxy-5-methylbenzyl)-2-phenylquinazolin-4(3H)-one] was obtained based on this scaffold. 6c exhibited dual binding activity with K(i) values of 0.123 µM for Mcl-1 and 0.179 µM for Bcl-2.