Proteomic approaches to biomarker discovery in prostate and bladder cancers

Proteomic technologies, including high resolution two-dimensional electrophoresis (2-DE), antibody/protein arrays, and advances in mass spectrometry (MS), are providing the tools needed to discover and identify disease associated biomarkers. Although application of these technologies to search for potential diagnostic/prognostic biomarkers associated with prostate and bladder cancer have been somewhat limited to date, proteins either overexpressed or underexpressed have been detected in both these urological cancers. Recent advances in mass spectrometry, especially platforms that permit rapid "fingerprint" profiling of multiple biomarkers, and tandem mass spectrometers for protein identification, will most assuredly enhance the discovery, identification, and characterization of potential cancer associated biomarkers. Furthermore, application of laser capture microdissection microscopes has provided a rapid and reproducible approach to procure pure populations of cells. This technology coupled to 2-DE and MS has significantly aided the elucidation of the differential expression profiles between disease, benign and normal prostate and bladder cell populations. Finally, development and application of learning algorithms and bioinformatics to the data generated by these proteomic technologies will be essential in determining the clinical potential of a protein biomarker. The purpose of this review is to provide the reader with an overview of the application of these technologies in the search and identification of potential diagnostic/prognostic biomarkers for prostate and bladder cancers.

Proteomic approaches to biomarker discovery in prostate and bladder cancers

Proteomic technologies, including high resolution two-dimensional electrophoresis (2-DE), antibody/protein arrays, and advances in mass spectrometry (MS), are providing the tools needed to discover and identify disease associated biomarkers. Although application of these technologies to search for potential diagnostic/prognostic biomarkers associated with prostate and bladder cancer have been somewhat limited to date, proteins either overexpressed or underexpressed have been detected in both these urological cancers. Recent advances in mass spectrometry, especially platforms that permit rapid "fingerprint" profiling of multiple biomarkers, and tandem mass spectrometers for protein identification, will most assuredly enhance the discovery, identification, and characterization of potential cancer associated biomarkers. Furthermore, application of laser capture microdissection microscopes has provided a rapid and reproducible approach to procure pure populations of cells. This technology coupled to 2-DE and MS has significantly aided the elucidation of the differential expression profiles between disease, benign and normal prostate and bladder cell populations. Finally, development and application of learning algorithms and bioinformatics to the data generated by these proteomic technologies will be essential in determining the clinical potential of a protein biomarker. The purpose of this review is to provide the reader with an overview of the application of these technologies in the search and identification of potential diagnostic/prognostic biomarkers for prostate and bladder cancers.

Quantitation of serum prostate-specific membrane antigen by a novel protein biochip immunoassay discriminates benign from malignant prostate disease

The lack of a sensitive immunoassay for quantitating serum prostate-specific membrane antigen (PSMA) hinders its clinical utility as a diagnostic/prognostic biomarker. An innovative protein biochip immunoassay was used to quantitate and compare serum PSMA levels in healthy men and patients with either benign or malignant prostate disease. PSMA was captured from serum by anti-PSMA antibody bound to ProteinChip arrays, the captured PSMA detected by surface-enhanced laser desorption/ionization mass spectrometry, and quantitated by comparing the mass signal integrals to a standard curve established using purified recombinant PSMA. The average serum PSMA value for prostate cancer (623.1 ng/ml) was significantly different (P < 0.001) from that for benign prostate hyperplasia (117.1 ng/ml) and the normal groups (age <50, 272.9 ng/ml; age >50, 359.4 ng/ml). These initial results suggest that serum PSMA may be a more effective biomarker than prostate-specific antigen for differentiating benign from malignant prostate disease and warrants additional evaluation of the surface-enhanced laser desorption/ionization PSMA immunoassay to determine its diagnostic utility.

Identification of a superimmunoglobulin gene family member overexpressed in benign prostatic hyperplasia

BACKGROUND

Benign prostate hyperplasia (BPH), a nonmalignant disease with an increasing rate of occurrence associated with advancing age, requires auxiliary markers to help identify its presence and distinguish its progression from prostate cancer.

METHODS

Hybridoma technology was used to generate an antibody against a BPH antigen, which was subsequently characterized by Western blot analysis, sequence homology, and RT-PCR.

RESULTS

A BPH-associated protein, designated P25/26, was identified that showed a strong sequence similarity with superimmunoglobulin family members, overexpressed in BPH, with lower expression observed in both normal and prostate cancer tissues.

CONCLUSIONS

Further studies appear warranted to assess the role that this and other superimmunoglobulin family members may have in the pathogenesis of BPH, and to determine if these glycoproteins have any clinical utility in the differential diagnosis or therapeutic monitoring of BPH.

The human cytomegalovirus UL98 gene transcription unit overlaps with the pp28 true late gene (UL99) and encodes a 58-kilodalton early protein

A murine monoclonal antibody (I2) reacts strongly with the nucleus of human cytomegalovirus (HCMV)-infected human fibroblasts. Western blot (immunoblot) analysis using I2 demonstrated that a protein with an apparent molecular mass of 58-kDa (E58) was expressed at 5 h after infection, and levels increased through 72 h. Immunoblot screening of an early cDNA expression library resulted in a positive clone which hybridized to the right end of the XbaI C fragment of the HCMV Towne strain. Further analysis demonstrated that the E58-specific clone was homologous to the putative UL98 open reading frame, which has been proposed to encode the viral alkaline exonuclease homolog. RNA analysis demonstrated a 3.0-kb RNA which is expressed at early times after infection, as well as in the absence of viral DNA replication, and which is 3' coterminal with the pp28 (UL99) gene region. Insertion of the UL98 genomic sequence into a eucaryotic expression vector and subsequent Western blot analysis using I2 demonstrated that the expressed protein comigrated with E58 from infected cells. E58 also reacts specifically with a previously described antibody, anti-P2-1, which was proposed to recognize a putative late 58-kDa protein. E58 comigrates with the putative late 58-kDa protein, indicating that these two proteins are likely the same. Analysis of the UL98 promoter revealed a TATATAA sequence located at nucleotide 142525. Insertion of the putative promoter 5' to a reporter gene demonstrated that the UL98 promoter was activated in cotransfection experiments with IE1 and IE2 proteins. These studies demonstrate that UL98 is a bona fide early gene, which is consistent with its probable role as the viral alkaline exonuclease gene.

A comprehensive study of physical parameters, biomechanical properties, and statistical correlations of iliac crest bone wedges used in spinal fusion surgery. II. Mechanical properties and correlation with physical parameters

Iliac crest wedges have been the most frequently used bone graft in spinal fusion procedures since the 1970s. Physical parameters and correlations among physical parameters of allogeneic iliac crest wedges have been described in part I of this series. This article discusses the mechanical properties, as well as their correlations with physical parameters, of iliac crest wedges. A total of 250 frozen-thawed, freeze-dried, and rehydrated iliac crest wedges were used in this study. The axial load-bearing capacities for wedges in the three subgroups showed no statistically significant differences, however, rehydrated wedges appeared to have the greatest load bearing capacity and compressive strength. In addition, rehydrated wedges were more deformable than either the frozen-thawed or freeze-dried wedges. Based on biomechanical properties, it is suggested that rehydrated (1 hour in vacuo), or frozen-thawed iliac crest wedge should be used in spinal fusion procedures, and the direct clinical application of nonrehydrated freeze-dried wedges should be avoided.

A comprehensive study of physical parameters, biomechanical properties, and statistical correlations of iliac crest bone wedges used in spinal fusion surgery. I. Physical parameters and their correlations

Iliac crest bone wedges are commonly used in spinal fusion procedures and must be capable of withstanding considerable mechanical stress during the healing process. The variability of "quality" of bone materials used in the production of bone wedges suggests that some bone materials may not be suitable for use in vertebral fusion procedures and some quantifiable means of predicting the suitability of bone wedges would be desirable. A total of 250 iliac crest wedges were used in this study. Physical parameters of iliac crest wedges, such as total cross-sectional area, cancellous cross-sectional area, cortical cross-sectional area, percentage of cortical cross-sectional area, "width," and apparent density were determined. The statistical correlations among physical parameters were investigated. These correlations revealed that the relative percentage of cortical and cancellous bone remained fairly constant at 41% and 59%, respectively, regardless of total cross-sectional area of a wedge, that apparent density did not appreciably change with donor age, and that ash (inorganic) and organic content (weight) correlated well with the apparent density.