Implication of transcriptional repression in compound C-induced apoptosis in cancer cells.

Compound C, a well-known inhibitor of AMP-activated protein kinase (AMPK), has been reported to induce apoptosis in some types of cells. However, the underlying mechanisms remain largely unclear. Using a DNA microarray analysis, we found that the expression of many genes was downregulated upon treatment with compound C. Importantly, compound C caused transcriptional repression with the induction of p53, a well-known marker of transcriptional stress response, in several cancer cell lines. Compound C did not induce the phosphorylation of p53 but dramatically increased the protein level of p53 similar to some other transcriptional inhibitors, including 5,6-dichloro-1-ß-D-ribobenzimidazole (DRB). Consistent with previous reports, we found that compound C initiated apoptotic death of cancer cells in an AMPK-independent manner. Similar to DRB and actinomycin D (ActD), two classic transcription inhibitors, compound C not only resulted in the loss of Bcl-2 and Bcl-xl protein but also induced the phosphorylation of eukaryotic initiation factor-alpha (eIF2α) on Ser51. Hence, the phosphorylation of eIF2α might be a novel marker of transcriptional inhibition. It is noteworthy that compound C-mediated apoptosis of cancer cells is correlated with decreased expression of Bcl-2 and Bcl-xl and the phosphorylation of eIF2α on Ser51. Remarkably, compound C exhibits potent anticancer activities in vivo. Taken together, our data suggest that compound C may be an attractive candidate for anticancer drug development.

Screening of differentially expressed genes of middle cerebral artery occlusion with DNA microarray.

OBJECTIVES: To screen differentially expressed genes of different days after cerebral artery occlusion and drug treatment, and identify related small drug molecules. MATERIALS AND METHODS: The gene expression profile GSE35338 of cerebral artery occlusion was downloaded from Gene Expression Omnibus database, including a total of 14 samples. 5 samples are 1 day after cerebral artery occlusion (control), 3 samples are 7 days after cerebral artery occlusion and 3 samples are under lipopolysaccharide (LPS) treatment. Differentially expressed genes (DEGs) between different days after cerebral artery occlusion were screened (p < 0.05, FDR < 0.05, |logFC| > 1). The DEGs were then entered into the CMAP database and related small drug molecules were retrieved, followed by calculation of co-expression score of the genes and construction of co-expression-drug network. FuncAssociate software and DAVID were used to obtain the functional clusters of genes with p-value < 0.05 and FDR < 0.05. RESULTS: Compared with the control group, 825, 1445, 218 DEGs and 4, 3, 2 most-related small drug molecules were respectively identified from 3, 7 days after cerebral artery occlusion and LPS treated group. Co-expression network was constructed and functional clusters were found to be 161, 146, and 6 in each group. CONCLUSIONS: Our study provides some underlying biomarkers for cerebral artery occlusion under varied conditions and potential small drug molecules for treatment of cerebral artery occlusion.

Unfolded protein response suppresses cisplatin-induced apoptosis via autophagy regulation in human hepatocellular carcinoma cells.

It has been shown that drug resistance is extremely common in hepatocellular carcinoma (HCC) and is one of the major problems in HCC chemotherapy. However, the detailed mechanisms remain largely unknown. We have previously shown that endoplasmic reticulum (ER) stress is involved in the tumorigenesis of HCC. Here, we demonstrated that the unfolded protein response (UPR) inhibits cisplatin-induced HCC cell apoptosis. In HCC cells, cisplatin treatment triggers the UPR, which subsequently inhibits cisplatin-induced apoptosis. Importantly, mild ER stress precondition suppresses the sensitivity of HCC cells to cisplatin-induced apoptosis through autophagy regulation. Furthermore, heat-shock protein 27 (Hsp27) is involved in the cytoprotective role of the UPR in cisplatin-induced apoptosis. We also demonstrated that Hsp27 inhibits cisplatin- induced HCC cell death through autophagy activation. Taken together, our results indicate that the UPR inhibits cisplatin-induced apoptosis in HCC cells, at least in part, by Hsp27-mediated autophagy activation.

PI3K/Akt promotes GRP78 accumulation and inhibits endoplasmic reticulum stress-induced apoptosis in HEK293 cells.

The potential pro-survival role of phosphatidylinositol 3-kinase (PI3K)/Akt during endoplasmic reticulum stress has been well-characterized. However, the detailed mechanisms remain largely unknown. Here, we showed that PI3K/Akt inhibition promoted endoplasmic reticulum stress-induced apoptosis in a glucose-regulated protein 78 (GRP78)-dependent manner. During endoplasmic reticulum stress, high levels of Akt phosphorylation were sustained for at least 18 h in HEK293 cells. Importantly, PI3K/Akt enhanced GRP78 accumulation through increasing its stability following endoplasmic reticulum stress. Furthermore, Akt1, but not Akt2 or Akt3, was involved in GRP78 stability regulation. These results suggest that PI3K/Akt inhibits endoplasmic reticulum stress-induced apoptosis in HEK293 cells, at least in part, by promoting GRP78 protein stability.