Spontaneous antibodies against Engrailed-2 (EN2) protein in patients with prostate cancer

A simple urine test by 3D-plus-3D immunoassay guides precise in vitro cancer diagnosis

Although a variety of urinary cancer markers are available for in vitro diagnosis, inherent problems of urine environment-containing various inorganic/organic ions/molecules that vary in concentration over a 20-fold range or more and significantly attenuate antibody avidity for markers-render conventional immunoassays unsuitable, remaining unresolved and a major challenge. Here we developed a 3D-plus-3D (3p3) immunoassay method, based on a single-step urinary marker detection by 3D-antibody probes, which are free of steric hindrance and capable of omnidirectional capture of markers in a 3D solution. The 3p3 immunoassay showed an excellent performance in the diagnosis of prostate cancer (PCa) through detecting PCa-specific urinary engrailed-2 protein, demonstrating 100% sensitivity and 100% specificity with the urine specimens of PCa-related and other related disease patients and healthy individuals. This innovative approach holds a great potential in opening up a novel clinical route for precise in vitro cancer diagnosis and also pushing urine immunoassay closer to more widespread adoption.

Is Engrailed-2 (EN2) a truly promising biomarker in prostate cancer detection?

Purpose: Prostate-specific antigen (PSA) is a sensitive but unspecific marker for prostate cancer (PC) detection, which may result in harms including overdiagnosis and overtreatment. Therefore, the development of new markers is of absolute value. The urinary level of engrailed-2 (EN2) protein has been recently suggested as a promising PC biomarker, correlating with tumour volume and stage. This study evaluated EN2 and its potential use in clinical practice.Materials and methods: Urinary EN2 was assessed by different commercially available enzyme-linked immunosorbent assay kits. The study sample included 90 patients with clinically localized PC compared to 30 healthy controls, and a group of 40 patients indicated for prostate biopsy due to an elevated PSA level where both pre- and post-digital rectal examination urine samples were collected.Results: No statistical difference between the patient group and the control group was obtained in all measured variables. There was no significant correlation between urinary EN2 and serum PSA, tumour staging and grading. Attentive DRE did not lead to significant changes of urinary EN2 or impact on its predictive power.Conclusions: Our results show that EN2 as a PC biomarker brings no additional value to the current use of PSA in clinical practice.

EN2 in Prostate Cancer

Despite extensive efforts to identify a clinically useful diagnostic biomarker in prostate cancer, no new test has been approved by regulatory authorities. As a result, this unmet need has shifted to biomarkers that additionally indicate presence or absence of "significant" disease. EN2 is a homeodomain-containing transcription factor secreted by prostate cancer into the urine and can be detected by enzyme-linked immunoassay. EN2 may be an ideal biomarker because normal prostate tissue and benign prostatic hypertrophic cells do not secrete EN2. This review discusses the enormous potential of EN2 to address this unmet need and provide the urologist with a simple, inexpensive, and reliable prostate cancer biomarker.