A pilot study to investigate the potential of mass spectrometry profiling in the discovery of novel serum markers in chronic renal disease.

Purpose: There has been significant criticism of how technologies such as SELDI have been used in biomarker discovery and how the data have been analysed. We initiated a proof-of-principle pilot study using SELDI with stringent pre-analytic and analytical procedures with robust statistical analysis, to determine whether, under such conditions, using different degrees of renal dysfunction as a model, useful data could be obtained.

Experimental Design: SELDI-TOF-MS profiling with stringent quality control measures was used to examine the proteomic profile of serum from healthy controls (n=30), patients with end-stage renal failure being treated by dialysis (n=30) and renal transplant patients (n=50) with varying degrees of graft stability.

Changes in the urinary proteome post-operatively in renal cancer patients - a reflection of tumour or kidney removal?

During the initial phases of a study focussed on discovering new urinary biomarkers for renal cell carcinoma, a number of challenges and limitations were identified, which we subsequently investigated. The purpose of this report is to provide insight into experimental design for such investigations and potential confounding factors that can impact on such studies. Sixty urine samples from 20 patients with clear cell renal cell carcinoma and ten live renal transplant donor patients, pre- and post-nephrectomy, were profiled using SELDI-TOF-MS incorporating stringent quality control and in-house data processing/analysis.

Using the protein chip interface with quadrupole time-of-flight mass spectrometry to directly identify peaks in SELDI profiles--initial evaluation using low molecular weight serum peaks.

Mass spectrometric profiling, particularly in the form of SELDI, has been used in many studies, particularly in attempts to generate diagnostic serum profiles. Several studies have generated promising results but one of the limitations is the inability to identify easily potential discriminatory peaks. This may enable specific assays to be developed and increased biological insight.

Integrated multi-level quality control for proteomic profiling studies using mass spectrometry.

Background: Proteomic profiling using mass spectrometry (MS) is one of the most promising methods for the analysis of complex biological samples such as urine, serum and tissue for biomarker discovery. Such experiments are often conducted using MALDI-TOF (matrix-assisted laser desorption/ionisation time-of-flight) and SELDI-TOF (surface-enhanced laser desorption/ionisation time-of-flight) MS. Using such profiling methods it is possible to identify changes in protein expression that differentiate disease states and individual proteins or patterns that may be useful as potential biomarkers.

Sample size determination in clinical proteomic profiling experiments using mass spectrometry for class comparison.

Mass spectrometric profiling approaches such as MALDI-TOF and SELDI-TOF are increasingly being used in disease marker discovery, particularly in the lower molecular weight proteome. However, little consideration has been given to the issue of sample size in experimental design. The aim of this study was to develop a protocol for the use of sample size calculations in proteomic profiling studies using MS.

Serum biomarker discovery in renal cancer using 2-DE and prefractionation by immunodepletion and isoelectric focusing; increasing coverage or more of the same?

As an initial screen for novel markers of renal cancer and to minimise background heterogeneity, we have compared the within-patient profiles of serum samples from seven patients pre- and post-nephrectomy. Samples were depleted of six of the most abundant proteins using Agilent's multiple affinity removal system (MARS) followed by solution-phase IEF prior to separation by 2-DE using narrow range IPG Strips, with a total of 84 gels. The reproducibility of the various steps was demonstrated and an approximate two-fold increase (from 374 to 779) in the number of protein spots observed in the pH region 4.

Proteomic profiling using mass spectrometry--does normalising by total ion current potentially mask some biological differences?

Normalisation of data to minimise the impact of technical variation on comparative sample analysis is often carried out. Using SELDI data as a model, we have examined the effects of normalisation by TIC which is commonly used for MS data. Significant intergroup differences in normalisation factor were found for serum profiles which could not be explained by experimental factors, implying that normalisation by TIC may in some situations also normalise biological differences and should be systematically evaluated.

Urinary biomarker profiling in transitional cell carcinoma.

Urinary biomarkers or profiles that allow noninvasive detection of recurrent transitional cell carcinoma (TCC) of the bladder are urgently needed. We obtained duplicate proteomic (SELDI) profiles from 227 subjects (118 TCC, 77 healthy controls and 32 controls with benign urological conditions) and used linear mixed effects models to identify peaks that are differentially expressed between TCC and controls and within TCC subgroups. A Random Forest classifier was trained on 130 profiles to develop an algorithm to predict the presence of TCC in a randomly selected initial test set (n = 54) and an independent validation set (n = 43) several months later.

Proteomic identification of a role for the von Hippel Lindau tumour suppressor in changes in the expression of mitochondrial proteins and septin 2 in renal cell carcinoma.

The von Hippel Lindau (VHL) tumour suppressor gene, VHL, plays a central role in development of sporadic conventional renal cell carcinomas (RCCs). Studying VHL function may, therefore, increase understanding of the pathogenesis of RCC and identify markers/therapeutic targets. Comparison of 2-DE protein profiles of VHL-defective RCC cells (UMRC2) transfected with control vector or wild-type VHL showed differences in 30 proteins, including several novel changes.

Proteomic analysis of primary cell lines identifies protein changes present in renal cell carcinoma.

New markers/targets for renal cell carcinoma (RCC) are needed to enable earlier detection and monitoring of disease and therapeutic targeting. To identify such molecules, normal and RCC-derived primary cell lines have been used as a simplified model system for studying changes that accompany tumorigenesis. Short-term cultures allow enrichment of relevant cell types from tissue samples, which is balanced against the potential for in vitro changes.

Genetic and epigenetic analysis of von Hippel-Lindau (VHL) gene alterations and relationship with clinical variables in sporadic renal cancer.

Genetic and epigenetic changes in the von Hippel-Lindau (VHL) tumor suppressor gene are common in sporadic conventional renal cell carcinoma (cRCC). Further insight into the clinical significance of these changes may lead to increased biological understanding and identification of subgroups of patients differing prognostically or who may benefit from specific targeted treatments. We have comprehensively examined the VHL status in tissue samples from 115 patients undergoing nephrectomy, including 96 with sporadic cRCC.

Influences of blood sample processing on low-molecular-weight proteome identified by surface-enhanced laser desorption/ionization mass spectrometry.

Background: Profiling approaches in proteomics, such as surface-enhanced laser desorption/ionization (SELDI) mass spectrometry, are used in disease marker discovery. The aim of this study was to investigate the potential influence of selected preanalytical factors on the results obtained.

Methods: Plasma samples anticoagulated with EDTA, citrate, or heparin, and serum samples from healthy volunteers were profiled by SELDI on CM10, immobilized metal affinity capture (IMAC) array with copper, and H50 chip surfaces.

Resistance to the tubulin-binding agents in renal cell carcinoma: no mutations in the class I beta-tubulin gene but changes in tubulin isotype protein expression.

Purpose: The primary purpose of this study was to determine whether mutations of the class I beta-tubulin gene may be implicated in the inherent resistance to tubulin-binding agents (TBA) in renal cancer, with a small number of samples and cell lines also being examined for class I and III beta-tubulin isotype protein expression.

Experimental Design: DNA was extracted from 90 renal tumors and the class I beta-tubulin gene analyzed for mutations. For each sample, eight PCRs were used to cover the complete coding sequence with intronic primers ensuring highly homologous pseudogenes were not coamplified.

Intrinsic chemotherapy resistance to the tubulin-binding antimitotic agents in renal cell carcinoma.

Renal cancer is one of the most chemoresistant tumor types. Using a panel of 10 established renal cancer cell lines that have not been subjected to prior drug selection, the range of functional resistance phenotypes to the tubulin-binding agents paclitaxel, vinblastine, vincristine and patupilone (epothilone B, EPO906) was determined, together with expression of P-glycoprotein (PgP), multidrug resistance associated protein-2 (MRP2) and major vault protein (MVP) proteins. The IC(50) values for vincristine correlated positively with PgP expression (r = 0.

Identification of proteins regulated by interferon-alpha in resistant and sensitive malignant melanoma cell lines.

Treatment of patients with malignant melanoma with interferon-alpha achieves a response in a small but significant subset of patients. Currently, although much is known about interferon biology, little is known about either the particular mechanisms of interferon-alpha activity that are crucial for response or why only some patients respond to interferon-alpha therapy. Two melanoma cell lines (MeWo and MM418) that are known to differ in their response to the antiproliferative activity of interferon-alpha, have been used as a model system to investigate interferon-alpha action.