Using tumor phenotype, histological tumor distribution, and mammographic appearance to explain the survival differences between screen-detected and clinically detected breast cancers

In the era of mass screening for breast cancer with mammography, it has been noted that conventional tumor attributes and mammographic appearance are insufficient to account for the better prognosis of screen-detected tumors. Such prognostication may require additional updated pathological information regarding tumor phenotype (e.g., basal status) and histological tumor distribution (focality). We investigated this hypothesis using a Bayesian approach to analyze breast cancer data from Dalarna County, Sweden. We used data for tumors diagnosed in the Swedish Two-County Trial and early service screening period, 1977-1995, and from the mature service screening period, 1996-1998. In the early period of mammographic screening (1977-1995), the crude hazard ratio (HR) of breast cancer death for screen-detected cases compared with symptomatic ones was 0.22 (95% CI: 0.17-0.29) compared with 0.53 (95% CI: 0.34-0.76) when adjusted for conventional tumor attributes only. Using the data from the mature service screening period, 1996-1998, the HR was 0.23 (95% CI: 0.08-0.44) unadjusted and 0.71 (95% CI: 0.26-1.47) after adjustment for tumor phenotype, mammographic appearance, histological tumor distribution, and conventional tumor attributes. The area under the ROC curve (AUC) for the prediction of breast cancer deaths using these variables without the detection mode was 0.82, only slightly less than that observed when additionally including the detection mode (AUC=0.83). Using Freedman statistics, conventional tumor attributes and mammographic appearances explained 58% (95% CI: 57.5-58.6%) of the difference of breast cancer survival between the screen-detected and the clinically detected breast cancers, whereas the corresponding figure was increased to 77% (95% CI: 75.6-77.6%) when adding the two information on tumor phenotype and histological tumor distribution. The results indicated that conventional tumor attributes and mammographic appearance are not sufficient to be interim markers for explaining the survival difference between screen-detected and clinically detected cancers in the era marked by the widespread use of mammography. Additional information on tumor phenotype and histological distribution may be added as effective interim markers for explaining the benefit of the early detection of breast cancer with mammography.

Abstract 3571: UKLS - United Kingdom Lung Cancer Screening Trial

In the UK 33,500 individuals die from lung cancer each year. The effectiveness of screening pre-symptomatic individuals urgently requires evaluation. The aim of UK Lung cancer Screening trial (UKLS) is to provide data required for an informed decision about the desirability of introducing population screening for lung cancer in the UK. The aim of the UKLS is to demonstrate a 25-30% mortality advantage and cost effectiveness of the screening. The UKLS pilot has started to recruit in 2011. The pilot sites are based at the Liverpool Heath & Chest Hospital, Liverpool and the Papworth Hospital, Cambridgeshire with a second reading site at the Royal Brompton Hospital, London. It will randomise 4,000 high risk patients identified by the Liverpool Lung Project (LLP) Risk Prediction Model. If the pilot trial is successful and funding is available, we plan to randomise a further 28,000 subjects from seven centres in the UK. Individuals are invited to participate if they have at least 5% risk of developing lung cancer over 5 years as predicted by the LLP risk model. The “Wald Single Screen” Design has been chosen for the UKLS pilot trial. Individuals meeting the inclusion/exclusion criteria will be sent invitations to participate and selected on the basis of the LLP risk questionnaire and selected to attend one of the pilot recruitment sites. After consent has been obtained, the participant will undertake spirometry and be asked to provide specimens (of blood, oral and nasal brushings and sputum) and to complete baseline lifestyle, psychosocial, and health economic questionnaire. Participants will be randomised to the study arm and will have a single low dose computed tomography scan (CT); those in the control arm will have usual care (no CT). CT scans will be read both locally and centrally and volumetric analysis will be performed on detected nodules. Both arms will be followed up for lung cancer incidence and mortality. Mortality will be documented after 10 years of follow-up. Modelling has resulted in the development of the UKLS care pathway to manage identified nodules. The aim of the main UKLS trial is to assess whether screening by low dose CT will confer a mortality advantage of 30% and also be cost effective for the UK population.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3571. doi:1538-7445.AM2012-3571

Amino acid-dependent regulation of the Saccharomyces cerevisiae GSH1 gene by hydrogen peroxide

The tripeptide gamma-L-glutamyl-L-cysteinylglycine (glutathione) is one of the major antioxidant molecules of cells and plays a vital role in buffering the cell against reactive oxygen species and toxic electrophiles. In the yeast Saccharomyces cerevisiae, the first enzyme involved in glutathione biosynthesis, gamma-glutamylcysteine synthetase, is encoded by the GSH1 gene. This study shows that the regulation of the yeast GSH1 gene by oxidants and the heavy metal cadmium is at the level of transcription. We also demonstrate that the regulation of the GSH1 gene by H2O2 depends upon the presence of the amino acids glutamate, glutamine and lysine in the media. Moreover, regulation of the GSH1 gene by H2O2, although requiring the Yap1 protein, appears to be mediated by a mechanism distinct from that which regulates the Yap1-dependent induction of genes encoding thioredoxin (TRX2) and a stress-inducible HSP70 (SSA1) by H2O2.

Glutathione is an important antioxidant molecule in the yeast Saccharomyces cerevisiae

The tripeptide gamma-L-glutamyl-L-cystinylglycine (glutathione) is one of the major antioxidant molecules of cells and is thought to play a vital role in buffering the cell against reactive oxygen species and toxic electrophiles. We wished to determine the role of glutathione in the protection of the yeast Saccharomyces cerevisiae against oxidative stress. This study shows that glutathione is an important antioxidant molecule in yeast, with gamma-glutamylcysteine synthetase (gsh1) mutants, deficient in glutathione synthesis, being hypersensitive to H2O2 and superoxide anions in both exponential- and stationary-phase cultures. Despite this, these mutants are still able to induce adaptive stress responses to oxidants.

Analysis of the adaptive oxidative stress response of Candida albicans

Treatment of Candida albicans with low concentrations of either hydrogen peroxide or menadione (a superoxide generating agent) induces an adaptive response which protects cells from the lethal effects of a subsequent challenge with higher concentrations of these oxidants. Pre-treatment with either menadione or hydrogen peroxide is protective against cell killing by either oxidant. This suggests that the pathogenic yeast C. albicans (unlike the budding yeast Saccharomyces cerevisiae which has separate responses) possesses an adaptive response that responds to both these oxidants. In addition, we found that C. albicans showed a greater level of resistance to oxidants, both H2O2 and redox-cycling agents, compared to that observed with S. cerevisiae. In an attempt to characterise the oxidative stress response in more detail we have analysed the effect of oxidants on the activities of a number of enzymes with known antioxidant activity.

The role of the YAP1 and YAP2 genes in the regulation of the adaptive oxidative stress responses of Saccharomyces cerevisiae

The YAP1 and YAP2 genes encode yeast transcription factors of the c-jun family. We show that yeast mutants deleted for either the YAP1 or the YAP2 genes are hypersensitive to oxidants, particularly H2O2, and that these genes play a role in regulating the induction of the H2O2 adaptive stress response in Saccharomyces cerevisiae. They do not significantly affect the regulation of the superoxide adaptive stress response. The intrinsic resistance of stationary-phase and respiring yeast cells towards superoxide anions is unaffected by deletion of the YAP1 and YAP2 genes. However, resistance towards H2O2 under these conditions is significantly reduced. We show that expression of the yeast GSH1 gene (encoding gamma-glutamylcysteine synthetase) and the SSA1 gene (encoding an HSP70 isoform) are induced by oxidants. Unlike the SSA1 and thioredoxin (TRX2) genes, expression of the GSH1 gene is more strongly induced by superoxide anions than by H2O2. In the absence of added oxidants, transcription of the GSH1 gene is reduced in strains carrying the yap1 deletion. However, we show that Yap1 is not required for the superoxide anion-mediated induction of GSH1 gene expression. Furthermore, while the H2O2-mediated induction of SSA1 expression is shown to by YAP1 dependent, the heat-shock-mediated induction of the SSA1 gene does not require YAP1. We also present evidence to show that the YAP2 gene does not regulate the expression of the TRX2, SSA1 or GSH1 genes.

Analysis of Saccharomyces cerevisiae proteins induced by peroxide and superoxide stress

Exponentially growing Saccharomyces cerevisiae cells are more sensitive to oxidants such as hydrogen peroxide and superoxides than stationary phase cells. Using disruption mutations in the genes encoding the two S. cerevisiae superoxide dismutases, we show that the principal mechanism of toxicity of redox-cycling compounds, such as menadione and plumbagin, is via the production of superoxide anions. Using two-dimensional polyacrylamide gel electrophoresis we have compared the pattern of protein expression in cells labelled with L-[35S]methionine and stressed with either H2O2 or menadione. Three groups of proteins were evident: those whose levels are elevated by both H2O2 and menadione, and those specifically induced by either H2O2 or menadione. Experiments with promoter fusions demonstrated that one of the heat inducible forms of HSP70 (SSA1) was inducible with H2O2. Furthermore, induction of the yeast H2O2-responsive TRX2 promoter by menadione required the metabolism of menadione.