Radiosensitizing effect of PARP-1 inhibitor Olaparib on MCF-7 breast cancer and hypoxic imaging / 中国药理学通报

Aim To investigate the radiosensitizing effect of the PARP inhibitor Olaparib on MCF-7 breast cancer model and to monitor the radiosensitizing effect of Olaparib by F-Fluoroerythronitroimidazole (F-FETNIM) PET/CT. Methods MCF-7 breast cancer model was established and divided into control group, Olaparib group, irradiation group and Olaparib + irradiation group according to random number table method; tumor volume was measured to calculate tumor inhibition rate and survival time of tumor-bearing mice was counted.

Targeting androgen receptor and trail: a novel treatment paradigm for breast cancer / 中国药理学与毒理学杂志

OBJECTIVE TNF- related apoptosis- inducing ligand(TRAIL)is a promising cancer therapeutic agent due to its minimal toxicity to normal tissues and remarkable apoptotic activity in tumors. However, most breast cancer cells are resistant to TRAIL- induced apoptosis. Our objectives are to investigate the underlying molecular mechanisms and to develop strategies to overcome such resistance. METHODS To identify modulators of TRAIL-induced apoptosis, we carried out a genome wide siRNA screen. To validate the screening result, we either silenced or overexpressed the identified genes in various breast cancer cells and changes in growth and TRAIL-induced cell apoptosis were determined in vitro and in an orthotopic xenograft mouse model. Finally, we investigated whether small molecules targeting the identified genes improve the effectiveness of TRAIL-therapy. RESULTS We unexpectedly identified androgen receptor (AR) to be responsible for TRAIL resistance. While AR is classically viewed as the key factor in prostate cancer progression, we found that AR expression levels were markedly elevated in human invasive breast cancer specimens including triple- negative breast cancers (TNBC) that are highly aggressive with poor prognosis. Importantly, breast cancer cell lines express different levels of AR that correlated with their TRAIL resistance. AR overexpression in MDA- MB- 231 and MDA- MB- 436 cells suppressed the TRAIL sensitivity whereas knockdown of AR rendered MCF-7 and MDA-MB-453 cells sensitive to TRAIL-induced apoptosis. AR overexpression also induced TRAIL resistance in breast tumors in vivo. Further, we observed an upregulation of the TRAIL receptor, death receptor 5 (DR5) in breast cancer cells, following the removal or inhibition of AR by its antagonists Casodex and MDV3100. Treatment with AR antagonists also enhanced TRAIL- induced breast cancer cell apoptosis. CONCLUSION AR signaling suppresses TRAIL-induced breast cancer cell apoptosis, in part, by suppressing DR5 expression, and a combination of AR antagonists together with TRAIL may be a novel and effective therapy for TNBC.

Green tea polyphenol epigallocatechin-3-gallate protects cells against peroxynitrite-induced cytotoxicity: modulatory effect of cellular G6PD status.

Glucose-6-phosphate dehydrogenase (G6PD) plays important roles in the maintenance of cellular redox balance. It was not until recently that the importance of G6PD in regulation of cellular growth and apoptosis emerged. In the present study, we found that G6PD-deficient fibroblasts were more susceptible to peroxynitrite-induced cytotoxicity. Treatment with peroxynitrite generator 3-morpholinosydnonimine (SIN-1) hydrochloride caused apoptosis in human fibroblast in a dose-dependent manner. This was preceded by a decrease in the intracellular level of glutathione (GSH) as well as accumulation of p53. The extent of apoptosis and glutathione depletion were greater in G6PD-deficient fibroblasts than in the normal counterpart. Pretreatment with green tea polyphenol epigallocatechin-3-gallate (EGCG) effectively blocked peroxynitrite-induced glutathione depletion, p53 accumulation, and apoptosis in both normal and G6PD-deficient cells. EGCG, administered to cells alone or as pretreatment, caused activation of Akt. The protective effect was abolished by phosphatidylinositol 3-kinase (PI3K) inhibitors, wortmannin, and LY294002. Our findings suggest that G6PD deficiency enhances the toxicity of peroxynitrite and that EGCG initiates cell survival signaling via the PI3K/akt pathway.

EPC-K1 Prevents ONOO(-)-induced Apoptosis in Cerebellar Granule Neurons.

The cytotoxic effect of peroxynitrite on cerebellar granule neurons was studied. Exposure of cerebellar granule neurons to 10 &mgr;mol/L peroxynitrite triggered apoptosis in vitro, which was confirmed by both morphological (nuclear morphology observed by fluorescence microscopy) and biochemical evidence (DNA fragmentation detected by ELISA). Using ESR spin labeling technique, the alteration of biophysical characteristics of neuronal cell membrane during the apoptotic process was studied. The results indicate that after treatment with peroxynitrite, the fluidity of both the surface layer and the deep layer of the neuronal cell membrane decreased markedly, and the S/W ratio of the membrane protein thiol groups increased significantly. Pre-treating cerebellar granule neurons with antioxidant EPC-K1, a novel water-soluble derivative of vitamin C and vitamin E, alleviated the oxidative injury and prevented cells from apoptosis.