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

Surface-activated chemical ionization-electrospray ionization source improves biomarker discovery with mass spectrometry

RATIONALE

Mass spectrometry (MS) is increasingly employed for the discovery of clinical biomarkers. However, due to sensitivity limitations related to in-source ionization yield, many potential biomarkers are not detected by standard mass spectrometers. Therefore, more efficient ion-source technologies are needed to improve MS applications in biomarker discovery.

METHODS

Among novel ion-source technologies, Surface-Activated Chemical Ionization (SACI), although endowed with high sensitivity linked to its ability to reduce chemical noise in mass spectra, has seen limited application in biomarker discovery to date, due to its selectivity for highly polar compounds. However, in combination with an Electrospray Ionization (ESI) source, SACI selectivity can be enlarged in the range of less polar compounds. To validate the new SACI-ESI approach in biomarker discovery, we applied it to a translational setting in oncology. We performed MS profiles of 101 human serum samples from a male population, aged 40 or older, coming to the clinic for prostate cancer evaluation based on multiple PSA exams, digital rectal examination and echography. The SACI-ESI MS spectra were analyzed and classified with an innovative bioinformatic approach based on the MS-search freeware developed in house.

RESULTS

Here we demonstrate that the SACI-ESI combination can produce MS spectra with greater sensitivity and lower noise than those obtained with the common ESI alone. We found that the SACI-ESI combination increased the number of detectable compounds and produced better quality of profiles in liquid chromatography (LC) coupled with MS (LC/MS) analysis of human serum samples, improving disease prediction potential.

CONCLUSIONS

SACI-ESI can facilitate MS-based discovery of potential biomarkers in human serum. Combined with the proposed bioinformatic approach (based on XCMS and NIST data elaboration) for the analysis of the MS spectra obtained, the potential for developing biomarkers with diagnostic capabilities are demonstrated in a prostate cancer diagnosis clinical setting.

Expression profile of the polycomb group protein enhancer of Zeste homologue 2 and its prognostic relevance in renal cell carcinoma

PURPOSE

EZH2 increases the proliferation rate and apoptosis resistance of renal cell carcinoma cell lines. To date its clinical impact on the outcome in patients with renal cell carcinoma is not known. To our knowledge this is the first study of the association of EZH2 expression with histopathological features and disease outcomes in a large cohort of patients who underwent surgery for renal cell carcinoma.

MATERIALS AND METHODS

Real-time reverse transcriptase-polymerase chain reaction was done to quantify EZH2 expression in malignant and adjacent benign renal tissue from a cohort of 119 patients with clear cell renal cell carcinoma. Median followup was 51 months. Immunohistochemistry was performed in a subset of samples. The impact of EZH2 expression on clinicopathological tumor features and outcome was investigated.

RESULTS

EZH2 was over expressed in renal cell carcinoma compared to adjacent benign renal parenchyma (median 57.02, range 0 to 368.11 vs 0, range 0 to 280.87, p <0.001). Immunohistochemistry showed concordant results and revealed EZH2 protein predominantly located in the nucleus. EZH2 expression was not associated with histopathological tumor features and patient characteristics. High EZH2 levels predicted a lower disease recurrence rate on univariate and multivariate analysis (p = 0.047 and 0.037, respectively).

CONCLUSIONS

These data support a role of EZH2 expression for renal cell carcinoma tumorigenesis rather than tumor progression. Contrary to previous EZH2 findings in cases of various human malignancies, high tumor EZH2 levels appear to indicate less aggressive tumor phenotypes with a favorable prognosis in renal cell carcinoma cases. Our findings suggest that EZH2 provides not only a potential therapeutic target, but also a molecular parameter for outcome prediction in patients with renal cell carcinoma.

Molecular biomarkers in prostate cancer

BACKGROUND

After more than two decades of clinical use, serum prostate-specific antigen (PSA) has increased the early diagnosis of prostate cancer, detecting the disease even when small volumes are present. Although stage migration of prostate cancer has occurred, PSA has well-known limitations, despite attempts at refinement and modification, such as the use of PSA velocity, which have been used to improve it. New biomarkers for prostate cancer have been discovered, with promising early results.

OBJECTIVE/METHODS

This article reviews the ubiquitous current literature on biomarkers in prostate cancer. A search using MEDLINE and EMBASE databases was performed and those articles reporting biomarkers in prostate cancer with clinically significant findings in terms of detection were analyzed. Immunohistochemical markers were not considered for this review.

RESULTS/CONCLUSION

Despite many markers being promising, no single marker has satisfied the criteria as a perfect candidate. Limited clinical use of IL-6, TGF-β1 and PCA3 has commenced, and further widespread availability of these tests is expected in the coming years. The future lies in artificial neural networks and panels of markers instead of individual assays. Although PSA has some well-known limitations, it is at present the best marker available for prostate cancer when used in conjunction with nomograms or risk calculators.

Osteopontin and interleukin-8 expression is independently associated with prostate cancer recurrence

PURPOSE

Lack of reliable biomarkers limits accurate prediction of prostate-specific antigen biochemical recurrence (disease progression) in prostate cancer. The two inflammatory chemokines, osteopontin and interleukin-8 (IL-8), are associated with tumor angiogenesis and metastasis. We investigated whether osteopontin and IL-8 expression in prostate cancer correlates with disease progression.

EXPERIMENTAL DESIGN

Archival prostatectomy specimens (n = 103) were obtained from patients with minimum 72-month follow-up. Osteopontin and IL-8 expression was evaluated by immunohistochemistry and graded for intensity and the area. Association of osteopontin and IL-8 staining with biochemical recurrence was evaluated by univariate and multivariate models.

RESULTS

In tumor cells, osteopontin and IL-8 staining was higher in the recurred group (203.2 +/- 78.4; 181.1 +/- 89.3) than in the nonrecurred group (122.7 +/- 76.6; 96.4 +/- 85.6; P < 0.001). Higher osteopontin and IL-8 staining was also observed in benign areas adjacent to tumor in the recurred group, than in nonrecurred group. In univariate analysis, except age, all preoperative and postoperative variables and osteopontin and IL-8 staining scores were significantly associated with biochemical recurrence (P < 0.05). In multivariate analysis, margin status and osteopontin staining independently associated with biochemical recurrence within 72 months. Osteopontin, either alone or with IL-8 and seminal vesicle invasion, was a significant variable in predicting biochemical recurrence within 24 months. Osteopontin and IL-8 staining predicted recurrence with high sensitivity (75.5%; 73.6%) and specificity (76%; 70.6%).

CONCLUSION

In prostatectomy specimens, osteopontin expression is independently associated with biochemical recurrence. Both osteopontin and IL-8 may be predictors of early disease progression.

Association of chromosomal locus 8q24 and risk of prostate cancer: a hospital-based study of German patients treated with brachytherapy

BACKGROUND

Genetic susceptibility contributes to the risk of prostate cancer but the underlying genes are largely unknown. Polymorphic loci on chromosome 8q24 have emerged as possible risk factors for breast and prostate cancer from genome-wide association studies.

OBJECTIVE

We aimed to define the risks associated with two single nucleotide polymorphisms, rs1447295 and rs13281615, in a hospital-based series of prostate cancer patients treated with brachytherapy.

MATERIAL AND METHODS

We analyzed genomic DNA samples of 488 prostate cancer cases undergoing brachytherapy at Hannover Medical School, and of 462 male controls from the same location. Genotyping was performed using 5'-exonuclease allelic discrimination assays, and results were evaluated with chi(2) tests and logistic regression analyses.

RESULTS

We investigated whether rs1447295 and rs13281615 are associated with disease risk in a hospital-based prostate cancer case-control series from Northern Germany. The rare allele of rs1447295 was observed at higher frequency among cases than among hospital-based controls (13.9% vs. 10.2%, P = 0.01), and there was a dose-dependent trend towards a higher prevalence of heterozygous and homozygous carriers among the prostate cancer patients (per allele OR 1.42, 95% CI 1.07; 1.87, P = 0.02). By contrast, the rare allele of rs13281615 did not predispose to prostate cancer (per allele OR 0.84, 95% CI 0.70; 1.00, P = 0.05). The distribution of combined 8q24 genotypes was significantly different between cases and controls (P = 0.01).

CONCLUSION

Our results corroborate previous reports of 8q24 as a prostate cancer susceptibility locus and provide evidence for rs1447295 as a potentially important genetic marker. Further studies are required to confirm whether the adjacent breast cancer-associated variant rs13281615 may be inversely associated with prostate cancer risk.