Citations

AbstractContext:Hyperandrogenism and oxidative stress are related in polycystic ovary syndrome (PCOS), but it is unknown whether hyperandrogenemia can activate oxidative stress.Objective:The purpose of this study was to determine the effect of oral androgen administration on fasting and glucose-stimulated leukocytic reactive oxygen species (ROS) generation, reduced nicotinamide adenine dinucleotide phosphate oxidase p47phox subunit gene expression, and plasma thiobarbituric acid-reactive substances (TBARS) in lean healthy reproductive-age women.Participants, Design, and Setting:Sixteen lean healthy ovulatory reproductive-age women were treated with 130 mg dehydroepiandrosterone (DHEA) or placebo (n = 8 each) for 5 d in this randomized, controlled, double-blind study that was performed at an an academic medical center.Main Outcome Measures:Leukocytic ROS generation, p47phox gene expression, and plasma TBARS were quantified in the fasting state and 2 h after glucose ingestion, before and after treatment.Results:Before treatment, subjects receiving DHEA or placebo exhibited no differences in androgens or any prooxidant markers while fasting and after glucose ingestion. Compared with placebo, DHEA administration raised levels of testosterone, androstenedione, and DHEA-sulfate, increased the percent change in glucose-challenged p47phox RNA content, and increased the percent change in fasting and glucose-challenged ROS generation from mononuclear cells and polymorphonuclear cells, p47phox protein content, and plasma TBARS.Conclusion:Elevation of circulating androgens comparable to what is present in PCOS increases leukocytic ROS generation, p47phox gene expression, and plasma TBARS to promote oxidative stress in lean healthy reproductive-age women. Thus, hyperandrogenemia activates and sensitizes leukocytes to glucose in this population.

Abstract A61 Background Patients with Barrett's esophagus (BE) and dysplasia are ideal candidates for chemopreventive strategies to reduce cancer risk. Difluoromethylornithine (DMFO) is a promising chemopreventive agent that inhibits polyamine synthesis involved in the regulation of cell growth and differentiation. We conducted a pilot study to examine the effects of DFMO on esophageal histopathology, mucosal polyamine content, and gene expression. Materials and Methods Patients (n=10) with histologically confirmed BE and low grade dysplasia were enrolled in a single-arm study of DFMO (0.5 g/m2/d) given continuously for 6 months. Esophagoscopy with biopsies (4 quadrants every 1 cm) was performed at baseline, 3 and 6 months, and at 12 months (where available). Grading of dysplasia was performed by a GI pathologist blinded to clinical/biomarker data. Audiology was also performed. Mucosal polyamine content was measured by high-performance liquid chromatography, and analyzed using paired t-tests. Gene expression profiling was performed using a cDNA two-color chip, and was compared between baseline and 6 months. Expression data was normalized using the two-channel fastlo routine and differential expression was computed using a Wilcoxon signed-rank test. Results After 6 months of DFMO treatment, histopathological response data demonstrate regression of dysplasia (n= 1), stable disease (n= 8), and progression of dysplasia (n= 1). Within the stable category, 2 patients with extensive low grade dysplasia showed only focal dysplasia based upon 4 or more biopsies at 6 months. Histolopathological improvements seen at 6 months were maintained at 12 months. Overall, DFMO was well tolerated. One patient had subclinical, unilateral ototoxicity. Modulation of polyamines (spermine, spermidine, putrescine, histamine) was shown only for putrescine which decreased with treatment (6 mo., p=0.07) and showed recovery to baseline at 12 months (p= 0.01). Gene expression profiling revealed modulated genes of potential biological importance (KLF5, KAL1, RFC5, TIMM8a, TC10) and of these, Krüppel-like factor 5 (KLF5) was downregulated whereas the others were upregulated. Conclusion >Further study of the chemopreventive effect of DFMO upon BE with dysplasia is suggested. DFMO treatment suppressed mucosal putrescine levels and downregulated KLF5, an important mediator of cell proliferation. Citation Information: Cancer Prev Res 2008;1(7 Suppl):A61.

Abstract Purpose: Celecoxib has been shown to induce cell death in conjunction with its chemopreventive effects. However, the mechanisms by which celecoxib induces cell death are incompletely understood. We determined whether celecoxib can induce autophagy, a process of cell destruction whereby cytoplasmic proteins and organelles are sequestered in vacuoles and delivered to lysosomes for degradation and recycling. Both apoptosis and autophagy have been shown to be negatively regulated by pro-survival Bcl-2 proteins, and the small molecule Bcl-2/Bcl-xL antagonist (ABT-737), can enhance both processes. Since autophagy can be pro-survival or pro-death depending upon the cellular context, we determined whether autophagy inhibition can drive colon cancer cells into apoptosis. Methods: HCT116 (wild-type and Bax−/−), HT29, SW480 colorectal cancer cell lines were treated with celecoxib (0–120 µM) and/or ABT-737 (Abbott; 0–5 µM) in the presence or absence of a pan caspase inhibitor, z-VAD-fmk. Cell viability was determined using the MTS assay and apoptosis was analyzed by Annexin V FITC labeling. Immunoblotting was used to analyze caspase cleavage and LC3 conversion. GFP-LC3B cellular localization was determined by confocol microscopy. Autophagic flux was determined by LC3 immunoblotting in the presence of the lysosome inhibitor, bafilomycin A1. Knockdown of Bcl-xL, Vps34 or Atg8/LC3B were achieved by lentiviral shRNA or siRNA. Results: Celecoxib was shown to induce apoptosis that was attenuated by ectopic Bcl-2 or Bax knockout. ABT-737 synergistically enhanced celecoxib-induced apoptosis as shown by caspase cleavage and Annexin V labeling. Celecoxib also induced autophagy, as shown by conversion of the autophagosome-associated protein light chain 3 (LC3) from a cytosolic (LC3I) to a membrane-bound (LC3II) form as shown by immunoblotting, and a punctate fluorescence pattern of ectopic GFP-LC3 protein. Celecoxib-induced conversion of LC3 that was due to autophagy induction, as shown using the lysosome inhibitor, Bafilomycin A1 that produced an accumulation of LC3II. Furthermore, ABT-737 enhanced LC3 conversion by celecoxib. Autophagy inhibition was achieved using 3-methyladenine (3-MA), wortmannin or knockdown of Vps34 or Atg8/LC3B using siRNA. Inhibition of autophagy enhanced apoptosis as shown by caspase cleavage and Bid truncation in cells treated with celecoxib plus ABT-737. Furthermore, the addition of 3-MA to celecoxib plus ABT-737 produced a 5-fold increase in apoptosis that was associated with caspase cleavage and cytochrome c release. Conclusions: Celecoxib induces both apoptosis and autophagy that can both be potentiated by ABT-737. Inhibition of autophagy was shown to potently drive cells into apoptosis, suggesting a novel therapeutic strategy against colon cancer cells. Citation Information: Cancer Prev Res 2010;3(1 Suppl):B46.

Abstract Purpose: Obesity is associated with an increased risk of colon cancer. However, the influence of body mass index (BMI) upon the outcome of colon cancer survivors and its relationship to gender remains unknown. Experimental Design: BMI (kg/m2) was calculated and categorized in patients with TNM stage II and III colon carcinomas (n= 4,381) enrolled in 7 randomized trials of 5-fluorouracil-based adjuvant chemotherapy. Cox proportional hazards modeling was used to determine the association of BMI with disease-free and overall survival. Results: Among colon cancer patients, 868 (20%) were obese (BMI ≥30 kg/m2) of which 606 were class 1 (BMI 30–34 kg/m2) and 262 were class 2,3 (BMI ≥35 kg/m2). Obese versus normal-weight patients were more likely to be younger, have distal tumors, show intact DNA mismatch repair (MMR), and have increased lymph node metastases (p <0.017). The association of BMI and MMR status was dependent upon patient age (p= 0.031). In a multivariate analysis, BMI was significantly associated with both disease-free (p=0.030) and overall survival (p=0.0017). Men with class 2,3 obesity showed reduced overall survival compared to normal weight men [HR 1.35 (1.02, 1.79); p=0.039]. Women with class I obesity had reduced overall survival [HR 1.24 (1.01, 1.53), p=0.045] compared to normal weight women. BMI was not predictive of therapeutic benefit. Conclusions: Obesity is associated with intact DNA mismatch repair status and was an adverse, independent prognostic variable in colon cancer survivors. Interventions to reduce obesity have the potential to improve patient outcomes in colon cancer survivors. Citation Information: Cancer Prev Res 2010;3(1 Suppl):B111.

Glioblastoma, the most common primary malignant cancer of the brain, is characterized by rapid tumor growth and infiltration of tumor cells throughout the brain. These traits cause glioblastomas to be highly resistant to current therapies with a resultant poor prognosis. Although aberrant oncogenic signaling driven by signature genetic alterations, such as EGF receptor (EGFR) gene amplification and mutation, plays a major role in glioblastoma pathogenesis, the responsible downstream mechanisms remain less clear. Here, we report that EGFRvIII (also known as ΔEGFR and de2-7EGFR), a constitutively active EGFR mutant that is frequently co-overexpressed with EGFR in human glioblastoma, promotes tumorigenesis through Src family kinase (SFK)-dependent phosphorylation of Dock180, a guanine nucleotide exchange factor for Rac1. EGFRvIII induces phosphorylation of Dock180 at tyrosine residue 722 (Dock180 Y722 ) and stimulates Rac1-signaling, glioblastoma cell survival and migration. Consistent with this being causal, siRNA knockdown of Dock180 or expression of a Dock180 Y722F mutant inhibits each of these EGFRvIII-stimulated activities. The SFKs, Src, Fyn, and Lyn, induce phosphorylation of Dock180 Y722 and inhibition of these SFKs by pharmacological inhibitors or shRNA depletion markedly attenuates EGFRvIII-induced phosphorylation of Dock180 Y722 , Rac1 activity, and glioblastoma cell migration. Finally, phosphorylated Dock180 Y722 is coexpressed with EGFRvIII and phosphorylated Src Y418 in clinical specimens, and such coexpression correlates with an extremely poor survival in glioblastoma patients. These results suggest that targeting the SFK-p-Dock180 Y722 -Rac1 signaling pathway may offer a novel therapeutic strategy for glioblastomas with EGFRvIII overexpression.