Discovery of novel inhibitors of anti-apoptotic Bcl-2 proteins derived from Bim BH3 domain

The BH3 mimetics targeting the interaction between the BH3-only proteins and their prosurvival Bcl-2family proteins have shown enormous potential as cancer therapeutics. Herein, seven analogues targeting anti-apoptotic Bcl-2 proteins derived from the Bim BH3 domain via sequence simplification and/or modification are described. The in vitro binding affinity on anti-apoptotic Bcl-2 proteins and cell killing activity were evaluated. The results showed that analogues could significantly bind to target proteins and exhibited anti-cancer effect against three cancer cell lines. Of particular interest were the analogue SM-5（KD= 9.48 nmol/L for Bcl-2） and SM-6（KD= 0.08 nmol/L for Bcl-xL）, which exhibited improved binding affinity compared with the lead Bim（KD= 16.90 nmol/L for Bcl-2 and 22.2 nmol/L for Bcl-xL, respectively）. These results indicated that the peptide sequence containing the four hydrophobic side chains occupying pockets within the BH3-recognition cleft of anti-apoptotic Bcl-2 proteins might be the minimum sequence required for the bioactivity and the active core region of Bim. Promising inhibitors of anti-apoptotic Bcl-2 proteins with high bioactivity might be designed based on the active core.

Effects of electroacupuncture on conjunctival cell apoptosis and the expressions of apoptosis-related proteins Caspase-3,Fas and Bcl-2 in rabbits with dry eye syndrome

Objective:By observing the effects of electroacupuncture(EA)on the apoptosis of conjunctival cells of rabbits with dry eye syndrome(DES)and the expressions of apoptosis-related proteins Caspase-3,Fas and Bcl-2,to discuss the mechanism of EA in the treatment of DES from the perspective of cell apoptosis.Methods:Male New Zealand rabbits were randomly divided into a normal group(NG),a model group(MG),an EA group(EAG)and a sham EA group(SEAG).DES rabbit model was developed by eye drop of 0.1%benzalkonium chloride.The rabbit tear secretion and tear film break-up time(BUT)were measured;terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling(TUNEL)assay was used to detect the apoptosis of conjunctival cells;the expressions of Caspase-3,Fas and Bcl-2 proteins in conjunctival cells were detected by immunohistochemistry.Results:Compared with the NG,the rabbit tear secretion decreased and the BUT was shortened in the MG(both P<0.01);compared with the MG and the SEAG,the rabbit tear secretion increased and the BUT was prolonged in the EAG(all P<0.05).Compared with the NG,the apoptosis of rabbit conjunctival cells increased(P<0.01),the expressions of Caspase-3 and Fas proteins increased(both P<0.05),and the expression of Bcl-2 protein decreased(P<0.01)in the MG;compared with the MG and the SEAG,the apoptosis of rabbit conjunctival cells decreased(both P<0.01),the expressions of Caspase-3 and Fas proteins decreased(all P<0.05),and the expression of Bcl-2 protein increased(both P<0.01)in the EAG.Conclusion:EA can inhibit the apoptosis of rabbit conjunctival cells,down-regulate the expressions of apoptosis-related proteins Caspase-3 and Fas,and up-regulate the expression of Bcl-2 protein,which may be one of the mechanisms of EA in treatment of DES.

Effect of arsenic trioxide on inhibition of restenosis after rabbit vascular injury and its mechanism

OBJECTIVE: To investigate the effect and mechanism of arsenic trioxide (As(2)O(3)) on the prevention of restenosis after vascular injury. METHODS: Apoptosis induction of As(2)O(3) on cultured rabbit vascular smooth muscle cells (VSMCs) in vitro was observed. Thirty-two New Zealand white rabbits were randomly divided into 2- and 4-wk study groups, and their controls. 10% As(2)O(3) at 2.5 mg x Kg(-1) x d(-1) or 0.9% sodium chloride was intraperitoneally infused for 3 days before left common carotid arteries were denudated with a balloon. After denudation 2- and 4-wk animals were sacrificed for morphometry and immunohistochemical studies on carotid arteries, and for histopathology on liver and kidney. RESULTS: It was shown via cellular morphology and DNA fragments in electrophoresis that promotion of As(2)O(3) on cultured vascular smooth muscle cell apoptosis was dependent upon its concentration and duration. Compared with the control animals, the mean vascular intimal proliferation areas were reduced in 2-wk study animals (P 0.05), while the mean vascular luminal areas were all enlarged in both study groups (all P

Drug and apoptosis resistance in cancer stem cells: a puzzle with many pieces

Resistance to anticancer agents and apoptosis results in cancer relapse and is associated with cancer mortality.Substantial data have provided convincing evidence establishing that human cancers emerge from cancer stemcells (CSCs), which display self-renewal and are resistant to anticancer drugs, radiation, and apoptosis, andexpress enhanced epithelial to mesenchymal progression. CSCs represent a heterogeneous tumor cell populationand lack specific cellular targets, which makes it a great challenge to target and eradicate them. Similarly, theirclose relationship with the tumor microenvironment creates greater complexity in developing novel treatmentstrategies targeting CSCs. Several mechanisms participate in the drug and apoptosis resistance phenotype in CSCsin various cancers. These include enhanced expression of ATP-binding cassette membrane transporters, activationof various cytoprotective and survival signaling pathways, dysregulation of stemness signaling pathways, aberrantDNA repair mechanisms, increased quiescence, autophagy, increased immune evasion, deficiency ofmitochondrial-mediated apoptosis, upregulation of anti-apoptotic proteins including c-FLIP [cellular FLICE (FADDlikeIL-1β-converting enzyme)-inhibitory protein], Bcl-2 family members, inhibitors of apoptosis proteins, andPI3K/AKT signaling. Studying such mechanisms not only provides mechanistic insights into these cells that areunresponsive to drugs, but may lead to the development of targeted and effective therapeutics to eradicate CSCs.Several studies have identified promising strategies to target CSCs. These emerging strategies may help targetCSC-associated drug resistance and metastasis in clinical settings. This article will review the CSCs drug and apoptosis resistance mechanisms and how to target CSCs.