In a recent study in Journal of Proteome Research by Human Protein Atlas-researchers a new reactive epitope of a prostate specific protein, particularly reactive in the late stages of prostate cancer is identified.

According to WHO, prostate cancer is the second most incident cancer in men and the fifth leading cause of death in men worldwide, and there is a demand for novel targets and approaches to diagnose and treat this cancer type. Five-year survival is reached by almost 100% of patients if the disease is still at a local and regional stage; however, the survival rate drops down to 30% in the case of aggressive form with distant metastasis and relapse after treatment. Thus the identification of new biomarkers for patient stratification would be a major advance in prostate cancer management. To date, only very few biomarkers for the prediction of prostate cancer progression have been verified and none was translated into clinical practice.

Proteomics keeps adding tiles to the molecular picture of prostate cancer development and progression by means of high-throughput and sensitive technologies, allowing us to detect and quantify proteins in tissue and body fluids. Serological biomarkers are desirable due to low invasiveness, low cost, and standardized handling procedures. Among serological biomarkers are autoantibodies. The relatively high frequency of antibody responses against tumor-associated antigens led to the assumption that they could be of use in the clinical setting.

With the aim to identify additional autoantibodies correlating with prostate cancer prognosis, the researchers have in this study profiled the IgG repertoire of 589 plasma and serum samples from prostate cancer patients with early- and late-stage disease plus 20 controls, starting from 3768 antigens on protein microarrays. The antigens were derived from the Human Protein Atlas that generates antibodies specific for each human protein using antigens selected within regions with low homology to other proteins.

The main finding of the study is related to higher IgG reactivity found toward SLC45A3, also known under the name of prostein, in samples from patient with late stages of prostate cancer.

Elisa Pin is the first author of the paper, and a Post Doc in the Biobank Profiling Group led by Jochen Schwenk at the Science for Life Laboratory.

– I think we have moved a step forward in the study of the complex scenario of autoimmune response in prostate cancer by the identification of a new reactive epitope of the prostate specific protein prostein, she says.

The work demonstrates the fascinating complexity of the immune system response and that a deep characterization of its specificity is essential when looking for biomarkers or assessing potential side effects during vaccine and drug development based on autoimmune targets.

–The workflow we propose (as shown in figure 1) could be of help in future studies on autoimmunity in cancer and other diseases, Elisa Pin explains.

This paper is the result of two years of experiments and data analysis and Elisa Pin was the main contributor for the validation part, statistical analysis and paper writing.

– When you come to the end of a project, sum up your findings and see that they can be somehow useful to the research community, that is the best part to me, she concludes.

Read the whole paper: Identification of a Novel Autoimmune Peptide Epitope of Prostein in Prostate Cancer