Citations

Abstract Glutathione S-transferase P1 (GSTP1) is of importance for cancer research because of its role in detoxifying carcinogens, activating antineoplastic prodrugs, metabolizing chemotherapeutic agents, and its involvement in cell cycle and apoptosis regulation. Two common GSTP1 genetic polymorphisms have been studied extensively. However, the full range of GSTP1 genetic variation has not been systematically characterized in the absence of disease pathology. We set out to identify common GSTP1 polymorphisms in four ethnic groups, followed by functional genomic studies. All exons, splice junctions, and the 5′-flanking region of GSTP1 were resequenced using 60 DNA samples each from four ethnic groups. The 35 single-nucleotide polymorphisms (SNP) identified included six nonsynonymous SNPs and 17 previously unreported polymorphisms. GSTP1 variant allozymes were then expressed in COS-1 cells, and five displayed significantly altered levels of enzyme activity. One decreased to 22% of the wild-type (WT) activity. Four variant allozymes had Km values that differed significantly from that of the WT, and five showed altered levels of immunoreactive protein compared with WT, with a significant correlation (r = 0.79, P < 0.007) between levels of immunoreactive protein and enzyme activity in these samples. In the Mexican American population, five linked SNPs were significantly associated with GSTP1 mRNA expression, one of which was found by electrophoretic mobility shift assay to alter protein binding. These studies have identified functionally significant genetic variation, in addition to the two frequently studied GSTP1 nonsynonymous SNPs, that may influence GSTP1's contribution to carcinogen and drug metabolism, and possibly disease pathogenesis and/or drug response. [Cancer Res 2008;68(12):4791–801]

Abstract Purpose: The proteasome is a multisubunit cellular organelle that functions as a nonlysosomal threonine protease. Proteasomes play a critical role in the degradation of proteins, regulating a variety of cellular processes, and they are also the target for antineoplastic proteasome inhibitors. Genetic variation in proteasome subunits could influence both proteasome function and response to drug therapy. Experimental Design: We resequenced genes encoding the three active proteasome β subunits using 240 DNA samples from four ethnic groups and the β5 subunit gene in 79 DNA samples from multiple myeloma patients who had been treated with the proteasome inhibitor bortezomib. Resequencing was followed by functional studies of polymorphisms identified in the coding region and 3′-flanking region (3′-FR) of PSMB5, the gene encoding the target for clinically useful proteasome inhibitors. Results: Resequencing of 240 DNA samples identified a series of novel ethnic-specific polymorphisms that are not represented in public databases. The PSMB5 3′-FR 1042 G allele significantly increased transcription during reporter gene studies, observations confirmed by genotype-phenotype correlations between single nucleotide polymorphisms (SNP) in PSMB5 and mRNA expression in the 240 lymphoblastoid cell lines from which the resequenced DNA was obtained. Studies with patient DNA samples identified additional novel PSMB5 polymorphisms, including a SNP and an insertion in the 3′-FR. Reporter-gene studies indicated that these two novel polymorphisms might decrease transcription. Conclusions: These results show that nonsynonymous coding SNPs in the PSMB5 gene did not show significant effects on proteasome activity, but SNPs did influence transcription. Future studies might focus on regulatory region polymorphisms.

The importance of the DNA damage response (DDR) pathway in development, genomic stability, and tumor suppression is well recognized. Although 53BP1 and MDC1 have been recently identified as critical upstream mediators in the cellular response to DNA double-strand breaks, their relative hierarchy in the ataxia telangiectasia mutated (ATM) signaling cascade remains controversial. To investigate the divergent and potentially overlapping functions of MDC1 and 53BP1 in the ATM response pathway, we generated mice deficient for both genes. Unexpectedly, the loss of both MDC1 and 53BP1 neither significantly increases the severity of defects in DDR nor increases tumor incidence compared with the loss of MDC1 alone. We additionally show that MDC1 regulates 53BP1 foci formation and phosphorylation in response to DNA damage. These results suggest that MDC1 functions as an upstream regulator of 53BP1 in the DDR pathway and in tumor suppression.

Background: Studies have failed to show a survival difference between intermittent hemodialysis (IHD) and continuous renal replacement therapy (CRRT). Comparative cost analyses are limited and fail to control for differences in patient disease severity and comorbid conditions. The authors retrospectively estimated clinical and economic outcomes associated with CRRT and IHD among critically ill patients experiencing acute renal failure (ARF) in 2 tertiary care hospitals in Rochester, Minnesota, between January 1, 2000, and December 12, 2001. Methods: 161 critically ill patients requiring dialysis for ARF were analyzed. Patient demo-graphics, comorbid conditions, ARF etiology, mode of renal replacement therapy (RRT), renal recovery, and survival were abstracted from medical chart. APACHE II scores at dialysis initiation were calculated. Administrative data tracked length of stay (LOS) and direct medical costs from initiation of RRT to death or intensive care unit (ICU) and hospital discharge. Multivariate modeling was used to adjust outcomes for baseline differences. Results: 84 (52%) of the patients received CRRT and 77 (48%) received IHD. CRRT-treated patients were younger (58 vs 65 years), less likely male (58% vs 77%), had higher APACHE II scores (32 vs 27) with a higher incidence of sepsis (46% vs 30%) and respiratory disease (56% vs 39%), and were less likely to have chronic renal insufficiency (32% vs 49%). With adjustment for differences in baseline patient characteristics, the RRT method did not affect the likelihood of renal recovery, in-hospital survival, or survival during follow-up. Mean adjusted ICU LOS was 9.5 days shorter for IHD-treated than CRRT-treated patients ( P < .001), and the adjusted mean difference in hospital and total costs associated with ICU stay was $56 564 and $60 827, in favor of IHD ( P < .001). Mean adjusted total costs through hospital discharge were $93 611 and $140 733 among IHD-treated and CRRT-treated patients, respectively ( P < .001). Conclusions: This observational study suggests that costs may significantly differ by mode of RRT despite similar severity-adjusted patient outcomes. Future prospective comparisons of renal replacement modalities will need to include both clinical and economic outcomes.

Abstract Barrett's esophagus, a columnar metaplasia of the lower esophagus epithelium related to gastroesophageal reflux disease, is the strongest known risk factor for the development of esophageal adenocarcinoma (EAC). Understanding the signal transduction events involved in esophageal epithelium carcinogenesis may provide insights into the origins of EAC and may suggest new therapies. To elucidate the molecular pathways of bile acid–induced tumorigenesis, the newly identified inflammation-associated signaling pathway involving IκB kinases β (IKKβ), tuberous sclerosis complex 1 (TSC1), and mammalian target of rapamycin (mTOR) downstream effector S6 kinase (S6K1) was confirmed to be activated in immortalized Barrett's CPC-A and CPC-C cells and esophageal cancer SEG-1 and BE3 cells. Phosphorylation of TSC1 and S6K1 was induced in response to bile acid stimulation. Treatment of these cells with the mTOR inhibitor rapamycin or the IKKβ inhibitor Bay 11-7082 suppressed bile acid–induced cell proliferation and anchorage-independent growth. We next used an orthotopic rat model to evaluate the role of bile acid in the progression of Barrett's esophagus to EAC. Of interest, we found high expression of phosphorylated IKKβ (pIKKβ) and phosphorylated S6K1 (pS6K1) in tumor tissues and the Barrett's epithelium compared with normal epithelium. Furthermore, immunostaining of clinical EAC tissue specimens revealed that pIKKβ expression was strongly correlated with pS6K1 level. Together, these results show that bile acid can deregulate TSC1/mTOR through IKKβ signaling, which may play a critical role in EAC progression. In addition, Bay 11-7082 and rapamycin may potentially be chemopreventive drugs against Barrett's esophagus–associated EAC. [Cancer Res 2008;68(8):2632–40]

Abstract Aberrant crypt foci (ACF) are the earliest visible neoplastic lesions in the colorectum. The natural history of these lesions and their role in the adenoma-carcinoma sequence are unknown. We studied ACF in a subset of patients randomized to placebo (n = 17), celecoxib (200 mg twice daily; n = 15), or celecoxib (400 mg twice daily; n = 13) in the Adenoma Prevention with Celecoxib (APC) trial. Magnification chromoendoscopy was done to identify, count, and biopsy ACF within the rectum at baseline and after 8 to 12 months of treatment. A total of 655 ACF were identified in 45 patients. We examined 70 of these ACF histologically, and all 70 were nondysplastic. Cohort characteristics and APC trial treatment results for substudy patients were similar to those of the overall APC trial. There was no significant modulation of ACF by celecoxib (versus placebo; P = 0.77). Immunohistochemical comparison of ACF with adjacent normal mucosa showed that ACF had an increased proliferative index as determined by Ki-67 (P &lt; 0.0001), but lacked other features of neoplasia such as increased cyclooxygenase-2 expression and microvessel density, nuclear localization of β-catenin, or decreased expression of the tumor suppressors SMAD4, Estrogen Receptor α, or MGMT. Only baseline SMAD4 expression in ACF correlated with posttreatment adenoma recurrence (independent of treatment arm; P = 0.01). The presence or number of nondysplastic ACF did not correlate with a higher risk of synchronous advanced or recurrent adenomas. Our overall results indicated that nondysplastic ACF were not accurate surrogate endpoint biomarkers of recurrent colorectal adenomas in the APC trial.

The recent “Advanced Neuroimaging for Acute Stroke Treatment” meeting on September 7 and 8, 2007 in Washington DC, brought together stroke neurologists, neuroradiologists, emergency physicians, neuroimaging research scientists, members of the National Institute of Neurological Disorders and Stroke (NINDS), the National Institute of Biomedical Imaging and Bioengineering (NIBIB), industry representatives, and members of the US Food and Drug Administration (FDA) to discuss the role of advanced neuroimaging in acute stroke treatment. The goals of the meeting were to assess state-of-the-art practice in terms of acute stroke imaging research and to propose specific recommendations regarding: (1) the standardization of perfusion and penumbral imaging techniques, (2) the validation of the accuracy and clinical utility of imaging markers of the ischemic penumbra, (3) the validation of imaging biomarkers relevant to clinical outcomes, and (4) the creation of a central repository to achieve these goals. The present article summarizes these recommendations and examines practical steps to achieve them.

Abstract Colorectal cancer (CRC) screening rates are often ascertained via self-reports but can be subject to overreporting bias. Asking about intention to get screened before asking about past screening may minimize overreporting of cancer screening. In a statewide survey conducted from July through October of 2005, we embedded an experiment that tested the effect of question ordering (asking about future intention to get screened before or after asking about past screening; “future first” and “future second,” respectively), crossed with survey mode (mail versus telephone), on CRC screening rates. Weighted analysis focused on 752 respondents who were ages 50 years or older. We found (a) that asking about future intentions to get screened before asking about past screening (future first) statistically significantly lowers reports of past CRC screening [70.9% future second versus 58.0% future first; odds ratio (OR), 1.83; 95% confidence interval (95% CI), 1.08-3.13]; (b) that there was no main effect of survey mode; and (c) that the effect of the ordering of the future intentions item varies by survey mode. In the mailed survey, the odds of reporting past CRC screening were almost thrice greater in the future second condition compared with the future first condition (72.4% versus 49.0%, respectively; OR, 2.74; 95% CI, 1.22-6.17). In the telephone condition, the odds of reporting were only 28% higher in the future second (69.5%) condition than in the future first condition (63.9%; OR, 1.28; 95% CI, 0.64-2.57). The results suggest that asking about future intentions to get screened before the actual behavior elicits lower, and arguably more truthful reports of CRC screening but mainly in mailed surveys. (Cancer Epidemiol Biomarkers Prev 2008;17(4):785–90)

Purpose Early clinical studies with gefitinib showed promising efficacy and mild toxicity in patients with advanced non–small-cell lung cancer (NSCLC). Thus, gefitinib was an ideal agent to evaluate in a maintenance setting in stage III disease. Patients and Methods Untreated patients with stage III NSCLC, a performance score of 0 to 1, and adequate organ function were eligible. All patients received cisplatin 50 mg/m 2 on days 1 and 8 plus etoposide 50 mg/m 2 on days 1 to 5, every 28 days for two cycles with concurrent thoracic radiation (1.8- to 2-Gy fractions per day; total dose, 61 Gy) followed by three cycles of docetaxel 75 mg/m 2 . Patients whose disease did not progress were randomly assigned to gefitinib 250 mg/d or placebo until disease progression, intolerable toxicity, or the end of 5 years. The planned sample size was 672 patients to confer power of 0.89 to detect a 33% increase over the expected median survival time of 21 months (one-sided P = .025, log-rank test). Random assignment was stratified by stage, histology, and measurable versus nonmeasurable disease. Results Enrollment began in July 2001. An unplanned interim analysis conducted in April 2005 rejected the alternative hypothesis of improved survival at the P = .0015 level for 243 randomly assigned patients. The study closed, and preliminary results were reported. Now, with a median follow-up time of 27 months, median survival time was 23 months for gefitinib (n = 118) and 35 months for placebo (n = 125; two-sided P = .013). The toxic death rate was 2% with gefitinib compared with 0% for placebo. Conclusion In this unselected population, gefitinib did not improve survival. Decreased survival was a result of tumor progression and not gefitinib toxicity.