A perspective on protein profiling of blood

The application of SELDI-TOF-MS in clinical diagnosis of cancers

Cancer diagnosis is important, and the early diagnosis of cancers could predict a more successful treatment. The proteomic studies emerged to be useful in combined analyses of samples from patients and provide more accurate diagnosis when compared to the single-factor-based diagnosis. In recent years, cancer detection with surface-enhanced laser desorption/ionization time of flight mass spectrometry (SELDI-TOF MS) is flourishing and brought significant progress in this area. This paper summarizes some recent results with this technique for cancer diagnosis.

Beta-2-microglobulin is an androgen-regulated secreted protein elevated in serum of patients with advanced prostate cancer

PURPOSE

A better understanding of secreted proteins may lead to the discovery of new biomarkers, which, along with prostate-specific antigen (PSA), may be useful in the diagnosis and treatment of prostate cancer patients.

EXPERIMENTAL DESIGN

Conditioned medium was collected from LNCaP cells following stimulation with methyltrienolone (R1881), 17beta-estradiol (estradiol), or interleukin-6 and analyzed for differential protein expression with surface-enhanced laser desorption/ionization-time of flight mass spectrometry. Quantitative reverse transcription-PCR, immunoblots, and ELISA were used to measure beta-2-microglobulin (B2M) message and protein levels in cells, conditioned medium, and serum.

RESULTS

Surface-enhanced laser desorption/ionization-time of flight revealed that many peaks were induced or repressed following stimulation with R1881 or estradiol. A peak of interest centered at 11.8 kDa was chosen for additional analysis. Immunodepletion identified the peak of interest as B2M. Reverse transcription-PCR and immunoblots confirmed that PSA and B2M were induced by R1881. However, unlike PSA, B2M was not increased on stimulation with estradiol or interleukin-6. Human B2M is identified in the serum of mice bearing human prostate cancer xenograft. B2M is expressed in human prostate cancer cell lines and tissues. Serum B2M levels are elevated in patients with metastatic, androgen-independent prostate cancer.

CONCLUSIONS

B2M is a secreted protein expressed in prostate cancer, which is more specific for androgen stimulation than PSA under the conditions tested. Additional studies are warranted to explore if B2M is as useful marker for prostate cancer. Identification of proteins secreted from cancer cells in preclinical models may be a useful strategy for biomarker discovery.

Conference report and review: current status of biomarkers potentially associated with prostate cancer outcomes

PURPOSE

The use of prostate specific antigen screening to diagnose and monitor prostate cancer is associated with well-known shortcomings. A 2-day Prostate Cancer Biomarker Conference was convened to identify promising areas of research and focus efforts on the most critical needs.

MATERIALS AND METHODS

The conference provided a forum for the presentation and discussion of ongoing prostate cancer biomarker research. This meeting also sought to identify a range of critical issues in the development and validation of biomarkers, foster research collaboration between groups representing government, academic and industry initiatives, and coordinate efforts with planned and ongoing clinical trials.

RESULTS

Taken collectively the conference presentations offered various new technologies for biomarker discovery and pathological assessment of clinical disease as well as the promise of biomarkers for improving prostate cancer diagnosis and treatment decisions. However, research efforts focused on biomarker validation and implementation clearly lag behind those directed toward initial biomarker discovery. It is apparent that guidelines are desperately needed to ensure the consistency of sample collection across institutions.

CONCLUSIONS

Several ongoing and planned adjuvant prostate cancer trials will provide a tremendous opportunity for biological sample collection along with the potential to validate many biomarkers. Practicing urologists have an opportunity to have a critical role in the successful accrual of patients into these trials.

Biomarker discovery from body fluids using mass spectrometry

Systems analysis of body fluids by mass spectrometry (MS) is an upcoming field of biomarker research. This approach is extremely attractive because it does not require biomarker candidates and the sample preparation is simple. However, during the development of the technique strong critical comments were made on the poor reproducibility, the special characteristics of blood as a source of peptides and on the frequent non-adequate statistical analysis of the data. Here we discuss the efforts made in the last few years to develop suitable protocols, which could lead to biomarker discovery from body fluids by mass spectrometry. Our review focuses on the systems analysis of non-digested blood serum or plasma samples by MALDI-TOF and SELDI-TOF.