Corrigendum: AMPA receptor-mediated regulation of a Gi-protein in cortical neurons.

This corrects the article DOI: 10.1038/39062.

Downregulation of XIAP expression in ovarian cancer cells induces cell death in vitro and in vivo.

A hallmark of cancer cells is an ability to evade apoptosis. Overexpression and/or activating mutations of prosurvival molecules such as the X-linked inhibitor of apoptosis (XIAP) contribute to this inappropriate cell survival. Our objectives were to investigate the effects of downregulation of XIAP in ovarian cancer cells in vitro and in vivo using the clinical candidate antisense oligonucleotide against XIAP, AEG35156 (AS XIAP). Three ovarian cancer cell lines were transfected with AS XIAP in vitro, and the effects on cell survival were assessed. Downregulation of XIAP resulted in significant apoptosis. To investigate the in vivo efficacy of AS XIAP, CD-1 nude mice were xenografted intraperitoneally with A2780-cp cells, treated with intraperitoneal AS XIAP and evaluated for survival time and tumor histology. Mice treated with 10 mg/kg/day AS XIAP showed a significant improvement in survival time compared to animals treated with control oligonucleotides. Histological analysis of the tumors showed significantly fewer viable cells in the AS XIAP-treated tumors. Downregulation of XIAP expression in ovarian cancer cells resulted in apoptosis in vitro and a prolonged survival time of ovarian cancer-bearing mice, which indicate that XIAP may be a valuable therapeutic target in ovarian cancers, and supports the ongoing clinical investigation of AEG35156.

Preclinical characterization of AEG35156/GEM 640, a second-generation antisense oligonucleotide targeting X-linked inhibitor of apoptosis.

PURPOSE: Cancer cells can use X-linked inhibitor of apoptosis (XIAP) to evade apoptotic cues, including chemotherapy. The antitumor potential of AEG35156, a novel second-generation antisense oligonucleotide directed toward XIAP, was assessed in human cancer models when given as a single agent and in combination with clinically relevant chemotherapeutics. EXPERIMENTAL DESIGN: AEG35156 was characterized for its ability to cause dose-dependent reductions of XIAP mRNA and protein in vitro and in vivo, to sensitize cancer cell lines to death stimuli, and to exhibit antitumor activity in multiple human cancer xenograft models as a single agent or in combination with chemotherapy. RESULTS: AEG35156 reduced XIAP mRNA levels with an EC50 of 8 to 32 nmol/L and decreased XIAP protein levels by >80%. Loss of XIAP protein correlated with increased sensitization to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis in Panc-1 pancreatic carcinoma cells. AEG35156 exhibited potent antitumor activity relative to control oligonucleotides in three human cancer xenograft models (prostate, colon, and lung) and was capable of inducing complete tumor regression when combined with taxanes. Antitumor effects of AEG35156 correlated with suppression of tumor XIAP levels. CONCLUSIONS: AEG35156 reduces XIAP levels and sensitizes tumors to chemotherapy. AEG35156 is presently under clinical assessment in multiple phase I trials in cancer patients as a single agent and in combination with docetaxel in solid tumors or cytarabine/idarubicin in leukemia.

Loss of XIAP protein expression by RNAi and antisense approaches sensitizes cancer cells to functionally diverse chemotherapeutics.

Stable expression of short-hairpin RNAs (shRNAs) directed against the X-linked inhibitor of apoptosis (XIAP) resulted in the generation of three MDA-MB-231 cell lines (XIAP shRNA cells) with reductions in XIAP mRNA and protein levels > 85% relative to MDA-MB-231 cells stably transfected with the U6 RNA polymerase III promoter alone (U6 cells). This RNA interference (RNAi) approach dramatically sensitized these cells to killing by the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Importantly, loss of XIAP also sensitized the cells to killing by taxanes but had no additional effects on killing by carboplatin and doxorubicin. The increased sensitivity of the XIAP shRNA cells to killing by TRAIL and taxanes correlated with enhanced caspase cleavage and activation, including caspase-8, and robust processing of poly(ADP-ribose) polymerase and BID compared to U6 cells. Additionally, increasing XIAP levels by adenovirus-mediated expression protected both XIAP shRNA and U6 cells from TRAIL killing in a dose-dependent manner. The effects observed by stable RNAi with respect to TRAIL sensitization were also achieved following downregulation of XIAP in Panc-1 cells treated with a second-generation, mixed-backbone antisense oligonucleotide, AEG 35156/GEM640. These data indicate that reducing XIAP protein expression by either RNAi or antisense approaches increases cancer cell susceptibility to functionally diverse chemotherapeutic agents and supports the notion that downregulation of XIAP in vivo may synergize with disease-relevant chemotherapeutic regimes, including TRAIL and taxanes, to increase the effectiveness of antineoplastic agents.

Antisense oligonucleotides targeting XIAP induce apoptosis and enhance chemotherapeutic activity against human lung cancer cells in vitro and in vivo.

Activation of programmed cell death in cancer cells offers novel and potentially useful approaches to improving patient responses to conventional chemotherapy. X-linked inhibitor of apoptosis (XIAP), is the most potent member of the IAP gene family in terms of its ability to inhibit caspases and suppress apoptosis. In this study, we investigated the effect of XIAP down-regulation by antisense oligonucleotides (AS ODNs) on human non-small cell lung cancer (NIH-H460) growth in vitro and in vivo. In cultured H460 cells, G4 AS ODN was identified as the most potent compound. It down-regulated XIAP mRNA by 55% and protein levels up to 60% as determined by real-time quantitative reverse transcription-PCR and Western blotting, respectively, and induced 60% cell death. In contrast, the scrambled control ODN caused minimal XIAP loss and less than 10% cell death. Treatment with G4 AS ODN induced apoptosis as revealed by degradation of procaspase-3 and poly(ADP-ribose) polymerase proteins with significant nuclear DNA condensation and fragmentation. In addition, G4 AS ODNs sensitized H460 cells to the cytotoxic effects of doxorubicin, Taxol, vinorelbine, and etoposide. In animal models, administration of G4 AS ODN had significant sequence-specific inhibitory effects on H460 solid tumor establishment in a xenograft model. This antitumor activity was associated with an 85% down-regulation of XIAP protein in the tumors. In addition, the combination of 15 mg/kg G4 AS ODN with 5 mg/kg vinorelbine significantly delayed tumor establishment, more than either agent alone. These studies support the contention that XIAP is a viable target for cancer therapy in human non-small cell lung cancer.