AKAP-4 as a biomarker for prostate cancer

Objective. Prostate cancer (PC) is the second most common cancer in older men, after skin cancer, with 218,890 new cases estimated and 27,050 deaths expected in the United States for 2007. PC is difficult to diagnose because prostate specific antigen (PSA) screening method is associated with many false positives. Therefore there is a need to discover new screening targets for the detection of PC. Cancer testis antigens (CTA) are a class of tumor associated antigens (TAA), showing a restricted expression in cancer, a strong immunogenicity and weak expression or absence in normal tissues. AKAP proteins are a growing family of scaffolding proteins involved in signal transduction control. Our aim in here was to investigate the expression of AKAP-4 in different staged PC patients. Methods. We analyzed normal prostate tissues, 20 patients with PC and an LnCaP human prostate cancer cell line by immunohistochemical methods. Results. AKAP-4 was highly expressed in the PC patients and not in normal tissues. The positive brown staining was present throughout the prostate tissue, especially in the epithelium lining the prostate glands at the cytoplasmic level in 13/20 (65%) patients. Conclusions. This study demonstrates the high aberrant expression of AKAP-4 in PC cases and in a PC cell line, LnCAP. Further studies are necessary to elucidate the relevance of AKAP-4 as biomarker in PC and its reliability as screening target vs. the common used PSA, as well as its use as potential immunotherapeutic target antigen for PC treatment.