Identification of Clinically Relevant Protein Targets in Prostate Cancer with 2D-DIGE Coupled Mass Spectrometry and Systems Biology Network Platform

Prostate cancer (PCa) is the most common type of cancer found in men and among the leading causes of cancer death in the western world. In the present study, we compared the individual protein expression patterns from histologically characterized PCa and the surrounding benign tissue obtained by manual micro dissection using highly sensitive two-dimensional differential gel electrophoresis (2D-DIGE) coupled with mass spectrometry. Proteomic data revealed 118 protein spots to be differentially expressed in cancer (n = 24) compared to benign (n = 21) prostate tissue. These spots were analysed by MALDI-TOF-MS/MS and 79 different proteins were identified. Using principal component analysis we could clearly separate tumor and normal tissue and two distinct tumor groups based on the protein expression pattern. By using a systems biology approach, we could map many of these proteins both into major pathways involved in PCa progression as well as into a group of potential diagnostic and/or prognostic markers. Due to complexity of the highly interconnected shortest pathway network, the functional sub networks revealed some of the potential candidate biomarker proteins for further validation. By using a systems biology approach, our study revealed novel proteins and molecular networks with altered expression in PCa. Further functional validation of individual proteins is ongoing and might provide new insights in PCa progression potentially leading to the design of novel diagnostic and therapeutic strategies

Screening for prostate cancer: an update.

The introduction of total prostate-specific antigen (tPSA) testing in serum has revolutionized the detection and management of men with prostate cancer. This review will highlight some of the exciting new developments in the field of prostate cancer screening in general and from our SPORE research program at Memorial-Sloan Kettering Cancer Center. First, it is important to understand that the inherent variability of tPSA levels affects the interpretation of any single results. Total variation in tPSA includes both analytical (i.e., pre-analytical sample handling, laboratory processing, assay performance, and standardization) and biological variation (i.e., metabolism, renal elimination, medication, physical and sexual activity, size and integrity of the prostate). Second, recent evidence demonstrates that no single tPSA cut-off separates men at high risk for prostate cancer from men at low risk or men with "significant" (high grade, high volume) cancer from those with low grade, indolent cancer. Taken together with a man's age, family history, ethnicity, and digital rectal exam results, tPSA levels add to the overall estimate of the risk of cancer, allowing men to share in the decision about a biopsy. Third, men who will eventually develop prostate cancer have increased tPSA levels years or decades before the cancer is diagnosed. These tPSA levels may reflect the long duration of prostate carcinogenesis and raise the question about a causal role for tPSA in prostate cancer development and progression. Total prostate-specific antigen measurements before age 50 could help risk stratify men for intensity of prostate cancer screening. Fourth, enhancing the diagnostic accuracy of tPSA, especially its specificity, is of particular importance, since higher specificity translates into fewer biopsies in men not affected by prostate cancer. While tPSA velocity has been shown to improve the specificity of tPSA, its sensitivity is too low to avoid prostate biopsy in a patient with an elevated tPSA level. Moreover, prospective screening studies have reported that tPSA velocity does not add diagnostic value beyond tPSA level. At this time, tPSA velocity appears most useful after diagnosis and after treatment, but its value in screening and prognostication remains to be shown. Finally, while free PSA molecular isoforms and human kallikrein-related peptidase 2 (hK2) hold the promise for detection, staging, prognosis, and monitoring of prostate cancer, evidence from large prospective clinical trials remain to be reported

Defining biochemical recurrence of prostate cancer after radical prostatectomy: a proposal for a standardized definition.

PURPOSE: Prostate-specific antigen (PSA) defined biochemical recurrence (BCR) of prostate cancer is widely used for reporting the outcome of radical prostatectomy (RP). A standardized BCR definition is lacking, and overall progression-free probability and risk of subsequent metastatic disease progression may vary greatly depending on the PSA criterion used. Ten definitions of BCR were evaluated to identify the one that best explains metastatic progression. METHODS: Of 3,125 patients who underwent RP at our institution since 1985, 75 developed distant metastasis during a median follow-up of 49 months. To predict metastasis progression, we modeled the clinical information using multivariable Cox regression analysis. BCR was included in the model as a time-dependent covariate, and separate models were developed for each definition. A goodness-of-fit (R2) statistic was used to determine the Cox model (and thereby the BCR definition) that best explained metastatic progression. RESULTS: The 10-year progression-free probability ranged from 63% to 79%, depending on the BCR definition. The model containing BCR defined as a PSA of at least 0.4 ng/mL followed by another increase best explained metastatic progression (R2 = 0.21). This definition was also associated with a high probability of subsequent secondary therapy, continued PSA progression, and rapid PSA doubling time. CONCLUSION: BCR defined as a PSA value of at least 0.4 ng/mL followed by another increase best explains the development of distant metastasis among 10 candidate definitions, after controlling for clinical variables and the use of secondary therapy. On the basis of this evidence, we propose that this definition be adopted as the standard for reporting the outcome of RP