Expression of Rb2/p130 in breast and endometrial cancer: correlations with hormone receptor status

Rb2/p130 is a member of the retinoblastoma family of proteins, consisting of Rb, Rb2 and p107, which are important negative regulators of cell cycle progression and differentiation. While Rb2 downregulation was observed in several malignant tumours including endometrial cancer, the role of p130 in breast carcinomas is still unknown. We investigated Rb2 protein expression in tumour tissue from 68 mammary and 41 endometrial carcinomas, 4 mammary cell lines, and normal tissue samples. Therefore, we performed Western blot experiments for Rb2, Rb, and the oestrogen and progesterone receptors (ER, PR-A, PR-B). Weak or absent Rb2 expression was more often found in endometrial (59%) than in mammary carcinomas (24%). We found significant positive correlations of Rb2 expression with Rb, ER, and PR-B in breast cancer samples, and of Rb2 with Rb, PR-A, PR-B, and younger age in endometrial carcinomas. No significant associations with histological grading, stage, nodal involvement, or Ki67 staining were detected. Rb2 mRNA expression was studied by semi-quantitative RT-PCR in 56 endometrial or mammary tissue samples and correlated significantly with Western blot results. Our results indicate that loss of Rb2 expression, mostly by transcriptional down-regulation, may be associated with the development and dedifferentiation of most endometrial and a subset of mammary carcinomas. © 2001 Cancer Research Campaign http://bjcancer.co

Integration of gene expression data with prior knowledge for network analysis and validation

<p>Abstract</p> <p>Background</p> <p>Reconstruction of protein-protein interaction or metabolic networks based on expression data often involves in silico predictions, while on the other hand, there are unspecific networks of in vivo interactions derived from knowledge bases.</p> <p>We analyze networks designed to come as close as possible to data measured in vivo, both with respect to the set of nodes which were taken to be expressed in experiment as well as with respect to the interactions between them which were taken from manually curated databases</p> <p>Results</p> <p>A signaling network derived from the TRANSPATH database and a metabolic network derived from KEGG LIGAND are each filtered onto expression data from breast cancer (SAGE) considering different levels of restrictiveness in edge and vertex selection.</p> <p>We perform several validation steps, in particular we define pathway over-representation tests based on refined null models to recover functional modules. The prominent role of the spindle checkpoint-related pathways in breast cancer is exhibited. High-ranking key nodes cluster in functional groups retrieved from literature. Results are consistent between several functional and topological analyses and between signaling and metabolic aspects.</p> <p>Conclusions</p> <p>This construction involved as a crucial step the passage to a mammalian protein identifier format as well as to a reaction-based semantics of metabolism. This yielded good connectivity but also led to the need to perform benchmark tests to exclude loss of essential information. Such validation, albeit tedious due to limitations of existing methods, turned out to be informative, and in particular provided biological insights as well as information on the degrees of coherence of the networks despite fragmentation of experimental data.</p> <p>Key node analysis exploited the networks for potentially interesting proteins in view of drug target prediction.</p

Fractionation of sulphur relative to iron during laser ablation-ICP-MS analyses of sulphide minerals: implications for quantification

In this study we investigate the effect that the mineral composition has on the quantification of sulphur by Laser Ablation ICP-MS (LA-ICP-MS) between a range of sulphide minerals: pyrite, pyrrhotite, bornite, chalcopyrite, sphalerite, pentlandite and tetrahedrite. The amount of S fractionation, relative to Fe, was compared between three different nano-second pulse width laser ablation systems: a 213 nm Nd:YAG, a 193 nm Nd:YAG and a 193 nm excimer. Significant matrix effects were seen for some minerals. With the 213 nm Nd:YAG laser, the yield (sensitivity per µg g⁻¹) of S relative to Fe is up to 50% higher for tetrahedrite and approximately 30% higher for bornite and chalcopyrite when compared to the yields of pyrite, whereas no fractionation was seen between Cu and Fe. For analyses on a fixed position on the sample, significant down-hole fractionation (DHF) occurred where S/Fe ratios increased during an analysis. The rate of DHF is also mineral specific, enhancing the need for matrix matched standards for accurate S analysis. The ablation properties of the minerals were also investigated by characterising the shape of the ablation craters and the composition and morphology of the deposited aerosol material around the ablation site using a field emission scanning electron microscope (FE-SEM). At fluences below 3.5 J cm⁻², pyrite is ablated efficiently by all laser systems with minimal melting around the ablation site, producing steep sided ablation craters. However, some melting occurs in and around the craters for most other sulphide minerals. The amount of melting is mineral specific and primarily dependent on its physical properties (e.g., bond strength and melting point). The greater the extent of melting, the more S fractionation occurs, consistent with the higher volatility of S relative to Fe.S. E. Gilbert, L. V. Danyushevsky, K. Goemann and D. Deat