Expression of the tumour antigen T21 is up-regulated in prostate cancer and is associated with tumour stage

OBJECTIVES To define the expression pattern of the tumour antigen T21 at the protein level in prostate tissues, prostate cell lines and a panel of normal tissues. To correlate the expression pattern of T21 in prostate cancer with clinical parameters. PATIENTS AND METHODS Tissue samples were collected from 79 patients presenting at clinic with either prostate cancer (63 patients) or benign prostatic hyperplasia (BPH, 16 patients). A tissue microarray (TMA) was constructed from 44 of the prostate cancer tissues and areas of benign disease (43 patients) from these tissues were also included on the TMA. The remaining tissues (prostate cancer 19 patients and BPH 16 patients) were mounted fresh frozen onto cork boards and sectioned. Full ethical approval was granted for all aspects of the study and informed patient consent was taken before tissue collection. Immunohistochemistry was used on the prostate tumour TMA, the normal tissue TMA and the fresh-frozen prostate tissues. Fluorescent microscopy and flow cytometry was performed on prostate cell lines. RESULTS Expression of T21 was highly restricted within normal tissues with only the stomach, ovary, breast and prostate having detectable T21 expression. T21 was significantly over-expressed in prostate cancer glands compared with benign tissue and was present in >80% of the malignant specimens analysed. Increased expression was positively correlated to pathological stage of prostate tumours. Additionally, T21 was associated with Gleason grade and prostate-specific antigen recurrence, although statistical significance was not reached in this restricted cohort of patients. CONCLUSION Taken together these results show that T21 is a potential new biomarker for advanced disease and that elevated levels of T21 appear relevant to prostate cancer development.