p53-dependent apoptosis is a major determinant of its tumor suppressor activity and can be triggered by hypoxia. No p53 target is known to be induced by p53 or to mediate p53-dependent apoptosis during hypoxia. We report that p53 can directly upregulate expression of Bnip3L, a cell death inducer. During hypoxia, Bnip3L is highly induced in wild-type p53-expressing cells, in part due to increased recruitment of p53 and CBP to Bnip3L. Apoptosis is reduced in hypoxia-exposed cells with functional p53 following Bnip3L knockdown. In vivo, Bnip3L knockdown promotes tumorigenicity of wild-type versus mutant p53-expressing tumors. Thus, Bnip3L, capable of attenuating tumorigenicity, mediates p53-dependent apoptosis under hypoxia, which provides a novel understanding of p53 in tumor suppression.

p53 deficiency is common in almost all human tumors and contributes to an aggressive chemo-or radiotherapy-resistant phenotype, therefore providing a target for drug development. Molecular targeting to restore wild-type p53 activity has been attempted in drug development and has led to the identification of CP-31398, PRIMA1, and the Nutlins. However, strategies targeting p53-activated transcriptional responses or p53 family member expression in p53-deficient tumors have yet to be explored. Here we demonstrate the use of noninvasive bioluminescence imaging in a high-throughput cell-based screen of small molecules that activate p53 responses and cell death in human tumor cells carrying a mutant p53. We isolated a number of small molecules that activate p53 reporter activity, increase expression of p53 target genes such as p21(WAF1) or death receptor 5 (KILLER͞DR5) of TNF-related apoptosis-inducing ligand (TRAIL), and induce apoptosis in p53-deficient cells. Some of the compounds activate a p53 response by increasing p73 expression, and knockdown of transactivating isoforms of p73 by small interfering RNA reduces their induction of p53-responsive transcriptional activity. Some compounds do not induce significant p73 expression but induce a high p53-responsive transcriptional activity in the absence of p53. In vivo experiments demonstrate potent antitumor effects of selected compounds, using either HCT116͞p53(؊͞؊) or DLD1 human colon tumor xenografts. The results establish the feasibility of a cell-based drug screening strategy targeting the p53 transcription factor family of importance in human cancer and provide lead compounds for further development in cancer therapy.apoptosis ͉ cancer ͉ drug development ͉ imaging

DR5 (also called TRAIL receptor 2 and KILLER) is an apoptosis-inducing membrane receptor for tumor necrosis factor-related apoptosis-inducing ligand (also called TRAIL and Apo2 ligand). DR5 is a transcriptional target of p53, and its overexpression induces cell death in vitro. However, the in vivo biology of DR5 has remained largely unexplored. To better understand the role of DR5 in development and in adult tissues, we have created a knockout mouse lacking DR5. This mouse is viable and develops normally with the exception of having an enlarged thymus. We show that DR5 is not expressed in developing embryos but is present in the decidua and chorion early in development. DR5-null mouse embryo fibroblasts expressing E1A are resistant to treatment with TRAIL, suggesting that DR5 may be the primary proapoptotic receptor for TRAIL in the mouse. When exposed to ionizing radiation, DR5-null tissues exhibit reduced amounts of apoptosis compared to wild-type thymus, spleen, Peyer's patches, and the white matter of the brain. In the ileum, colon, and stomach, DR5 deficiency was associated with a subtle phenotype of radiation-induced cell death. These results indicate that DR5 has a limited role during embryogenesis and early stages of development but plays an organ-specific role in the response to DNA-damaging stimuli.

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In SCLC, sarcopenic male patients with high NLR have a poor prognosis and do not tolerate standard treatment. Intensive supportive care is needed in these patients.

The proapoptotic cytokine tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is being evaluated presently as a selective anticancer agent, but its limited effects against cancer cell lines has raised some concerns about its ultimate clinical utility. Here, we review recent findings that cancer cell sensitivity to TRAIL is greatly increased when the Bcl-2 family protein Mcl-1 is down-regulated by the Raf/vascular endothelial growth factor kinase inhibitor sorafenib, a Food and Drug Administration-approved cancer drug. Using the TRAIL-sorafenib combination as a tactic to more effectively kill cancer cells may provide an effective tool to attack a variety of human cancers that are largely presently untreatable.

We identified the peroxisomal proliferator response element (PPRE) in the +68/+89 region of the rat GLUT2 gene. To identify whether the putative PPRE in the GLUT2 gene (GLUT2-PPRE) is functional, GLUT2 promoter-luciferase reporter constructs were transfected into CV-1 cells. Promoter activities were increased by coexpression of peroxisomal proliferator-activated receptor (PPAR)-␥, retinoid X receptor (RXR)-␣, and treatment of their ligands; troglitazone and 9-cis retinoic acid potentiated the transactivational effects. Introduction of mutations in GLUT2-PPRE resulted in loss of transactivational effects of the PPAR-␥/RXR-␣ heterodimer. Electrophoretic mobility shift assay using nuclear extracts of CV-1 cells, which were transfected with various combinations of PPARs or RXR-␣ expression plasmids, revealed that heterodimers of PPAR-␥ and RXR-␣ preferentially bound to GLUT2-PPRE. In HIT-T15 cells, promoter activity of the rat GLUT2 gene was increased by troglitazone and 9-cis retinoic acid, and mutations of GLUT2-PPRE resulted in reduction of promoter activity. In addition, we observed increased GLUT2 transcription by troglitazone and 9-cis retinoic acid in isolated rat primary islets. These results suggested that the GLUT2-PPRE is functional and plays a significant role in gene expression of GLUT2 in pancreatic ␤-cells. This is the first report identifying PPRE in a gene involved in glucose homeostasis, linking the effect of troglitazone on the regulation of insulin secretion. Diabetes 49:1517-1524, 2000

The cytotoxic death ligand TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) is a tumor-specific agent under development as a novel anticancer therapeutic agent. However, some reports have demonstrated toxicity of certain TRAIL preparations toward human hepatocytes and keratinocytes through a caspasedependent mechanism that involves activation of the extrinsic death pathway and Type II signaling through the mitochondria. We have isolated and purified both His-tagged protein and three versions of native recombinant human TRAIL protein from Escherichia coli. We found that 5 mM dithiothreitol in the purification process enhanced oligomerization of TRAIL and resulted in the formation of hyper-oligomerized TRAILs, including hexamers and nonomers with an extremely high potency in apoptosis induction. Although death-inducing signaling complex formation was much more efficient in cells treated with hyper-oligomerized TRAILs, this did not convert TRAIL-sensitive Type II HCT116 colon tumor cells to a Type I death pattern as judged by their continued sensitivity to a caspase 9 inhibitor. Moreover, TRAIL-resistant Type II Bax-null colon carcinoma cells were not converted to a TRAIL-sensitive Type I state by hyper-oligomerized TRAIL. Primary human esophageal epithelial 2 cells were found to be sensitive to all TRAIL preparations used, including trimer TRAIL. TRAIL-induced death in esophageal epithelial 2 cells was prevented by caspase 9 inhibition for up to 4 h after TRAIL exposure. This result suggests a possible therapeutic application of caspase 9 inhibition as a strategy to reverse TRAIL toxicity. Hyper-oligomerized TRAIL may be considered as an alternative agent for testing in clinical trials.