B-346 Serum ERG Protein as a Potential Biomarker for Prostate Cancer

Abstract Background ERG (ETS-related gene) is an oncogene, and is a member of the ETS (erythroblast transformation-specific) family of transcription factors. Genes in the ETS family regulate embryonic development, cell proliferation, differentiation, angiogenesis, inflammation, and apoptosis. ERG overexpression has been implicated in a diverse number of cancers, including prostate cancer, Ewing’s sarcoma and acute myeloid leukemia. ERG can fuse with TMPRSS2 protein to form an oncogenic fusion gene product that is commonly found in human prostate cancer, especially in hormone-refractory prostate cancer. Approximately 50% of prostate cancer cases are characterized by ERG gene fusions, which lead to ERG overexpression and may contribute to development of androgen-independence in prostate cancer. ERG overexpression in prostate cancer is critical to cancer progression and is associated with advanced stages of the disease, which has provided ERG as an additional biomarker. However, it is unclear whether ERG proteins are elevated and can be easily detected in serum samples from prostate cancer patients. Methods We developed a human ERG sandwich ELISA kit with an assay sensitivity of 66pg/mL. ERG protein levels were measured using this kit in serum samples from 36 prostate cancer patients and 27 non-cancer controls. Results Serum ERG protein was detected in all 36 prostate cancer patients (range: 4.4 to 256.5 ng/ml, mean: 23ng/ml) and was significantly elevated compared to non-cancer controls (range: 0-1.3ng/ml, mean: 0.156ng/ml) (p<0.05). Conclusion Our findings suggest that serum ERG may serve as potential prognostic biomarker and an additional diagnostic biomarker for prostate cancer. The detection of elevated serum ERG in prostate cancer patients indicates their specificity for the disease. Larger studies with more samples, different cancer stages, and longer follow-up are needed to validate these results and establish the clinical application of serum ERG level as prognostic marker and early diagnostic biomarker for prostate cancer.