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Deirdre A Nelson

Publications and source records attributed to Deirdre A Nelson.

6 recordsLinked to original sources
PubMed2006

Autophagy promotes tumor cell survival and restricts necrosis, inflammation, and tumorigenesis.

Defective apoptosis renders immortalized epithelial cells highly tumorigenic, but how this is impacted by other common tumor mutations is not known. In apoptosis-defective cells, inhibition of autophagy by AKT activation or by allelic disruption of beclin1 confers sensitivity to metabolic stress by inhibiting an autophagy-dependent survival pathway. While autophagy acts to buffer metabolic stress, the combined impairment of apoptosis and autophagy promotes necrotic cell death in vitro and in vivo. Thus, inhibiting autophagy under conditions of nutrient limitation can restore cell death to apoptosis-refractory tumors, but this necrosis is associated with inflammation and accelerated tumor growth. Thus, autophagy may function in tumor suppression by mitigating metabolic stress and, in concert with apoptosis, by preventing death by necrosis.

Animals↗
PubMed2005

Akt-dependent expression of NAIP-1 protects neurons against amyloid-{beta} toxicity.

Neurotrophins are a family of growth factors that attenuate several forms of pathological neuronal cell death and may represent a putative therapeutic approach to neurodegenerative diseases. In Alzheimer disease, amyloid-beta (Abeta) is thought to play a central role in the neuronal death occurring in brains of patients. In the present study, we evaluate the ability of neurotrophin-3 (NT-3) to protect neurons against the toxicity induced by aggregated Abeta. We showed that in primary cultures of cortical neurons, NT-3 reduces Abeta-induced apoptosis by limiting caspase-8, caspase-9, and caspase-3 cleavage. This neuroprotective effect of NT-3 was concomitant to an increased level of Akt phosphorylation and was abolished by an inhibitor of the phosphatidylinositol-3 kinase (PI-3K), LY294002. In parallel, NT-3 treatment reduced Abeta induced caspase-3 processing to control levels. In an attempt to link PI-3K/Akt to caspase inhibition, we evaluated the influence of the PI-3K/Akt axis on the expression of a member of the inhibitors of apoptosis proteins (IAPs), the neuronal apoptosis inhibitory protein-1. We demonstrated that NT-3 induces an up-regulation of neuronal apoptosis inhibitory protein-1 expression in neurons that promotes the inhibition of Abeta-induced neuronal apoptosis. Together, these findings demonstrate that NT-3 signaling counters Abeta-dependent neuronal cell death and may represent an innovative therapeutic intervention to limit neuronal death in Alzheimer disease.

Amyloid beta-Peptides↗
PubMed2005

Key roles of BIM-driven apoptosis in epithelial tumors and rational chemotherapy.

Defective apoptosis not only promotes tumorigenesis, but also can confound chemotherapeutic response. Here we demonstrate that the proapoptotic BH3-only protein BIM is a tumor suppressor in epithelial solid tumors and also is a determinant in paclitaxel sensitivity in vivo. Furthermore, the H-ras/mitogen-activated protein kinase (MAPK) pathway conferred resistance to paclitaxel that was dependent on functional inactivation of BIM. Whereas paclitaxel induced BIM accumulation and BIM-dependent apoptosis in vitro and in tumors in vivo, the H-ras/MAPK pathway suppressed this BIM induction by phosphorylating BIM and targeting BIM for degradation in proteasomes. The proteasome inhibitor Velcade (P-341, Bortezomib) restored BIM induction, abrogated H-ras-dependent paclitaxel resistance, and promoted BIM-dependent tumor regression, suggesting the potential benefits of combinatorial chemotherapy of Velcade and paclitaxel.

Animals↗
PubMed2004

Epothilone induced cytotoxicity is dependent on p53 status in prostate cells.

BACKGROUND: Epothilones are a promising class of drugs in clinical trials of prostate cancer that target the microtubules, similar to taxanes, and induce apoptosis in taxane resistant tumors. The tumor suppressor p53 is one important molecular mechanism of chemotherapy resistance that in some studies predicted tumor sensitivity to paclitaxel. We hypothesized that epothilone induced cytotoxicity would be influenced by the status of p53 in prostate cells. METHODS: LNCaP, DU145, and a transformed rat prostate (RP) epithelial cell line with a temperature sensitive mutant p53 (val 135) were studied for the effect of epothilone on cell viability, cell cycle, and cell cycle checkpoint proteins. RESULTS: Epothilone had greater cytotoxicity in p53 mutant cancer cells compared to wild type cells. We confirmed our findings by creating a transformed RP epithelial cell line with a temperature sensitive mutant p53 (val 135). Using a tetrazolium (MTT) assay we found that epothilone (100 nM) decreased cell viability in RP cells by 90% with mutant p53 compared to 45% with wild type p53 (P < 0.01). Epothilone induced G2/M arrest in 50% of cells with mutant p53 compared to 25% with wild type p53 (P < 0.01). To begin to understand mechanism of epothilone induced G2/M arrest, we assessed cell cycle checkpoint proteins. We found that the effect to enhance G2/M cell cycle arrest was associated with dephosphorylation of cdc2 in both p53 wild type and p53 mutant RP cells. CONCLUSIONS: These results demonstrate that epothilone is more active against transformed prostate epithelial cells with mutant compared to wild type p53. Epothilone is capable of dephosphorylation of cdc2 in both p53 wild type and mutant cells, which is associated with G2/M cell cycle arrest. These data provide a basis for further study of p53, and the phosphorylation status of cdc-2, as markers for epothilone sensitivity in clinical studies.

Animals↗
PubMed2004

Hypoxia and defective apoptosis drive genomic instability and tumorigenesis.

Genomic instability is a hallmark of cancer development and progression, and characterizing the stresses that create and the mechanisms by which cells respond to genomic perturbations is essential. Here we demonstrate that antiapoptotic BCL-2 family proteins promoted tumor formation of transformed baby mouse kidney (BMK) epithelial cells by antagonizing BAX- and BAK-dependent apoptosis. Cell death in vivo correlated with hypoxia and induction of PUMA (p53 up-regulated modulator of apoptosis). Strikingly, carcinomas formed by transformed BMK cells in which apoptosis was blocked by aberrant BCL-2 family protein function displayed prevalent, highly polyploid, tumor giant cells. Examination of the transformed BMK cells in vivo revealed aberrant metaphases and ploidy changes in tumors as early as 9 d after implantation, which progressed in magnitude during the tumorigenic process. An in vitro ischemia system mimicked the tumor microenvironment, and gain of BCL-2 or loss of BAX and BAK was sufficient to confer resistance to apoptosis and to allow for accumulation of polyploid cells in vitro. These data suggest that in vivo, even in cells in which p53 function is compromised, apoptosis is an essential response to hypoxia and ischemia in the tumor microenvironment and that abrogation of this response allows the survival of cells with abnormal genomes and promotes tumorigenesis.

Animals↗