CD146 protein in prostate cancer: revisited with two different antibodies.

Aims: CD146 is a potentially metastasis promoting cell adhesion molecule and its expression has been described in various solid tumours. We aimed to evaluate the expression of CD146 in prostate cancer by immunohistochemistry in a clinically characterised study cohort to evaluate its prognostic properties.

Methods: We evaluated the CD146 protein expression using a polyclonal and a monoclonal antibody on 169 clinico-pathologically characterised cases. Statistical analyses were applied to test for correlations and diagnostic and prognostic associations.

Results: CD146 detection with the polyclonal antibody revealed marked differential expression between tumour and normal tissue and was also a significant marker for shortened PSA relapse free survival. The monoclonal CD146 antibody demonstrated a weaker epithelial signal, which was significantly correlated with that of the polyclonal antibody, but revealed no prognostic value. However, the Western blot of the polyclonal antibody displayed a clearly reduced specificity.

Conclusions: Evaluation of protein expression can be highly dependent on the primary antibody employed. A credible evaluation of antibody specificity is crucial to prove the validity of protein expression studies. The immunoreactivity of the polyclonal CD146 antibody (Abcam, ab28360) is prognostic of PSA-relapse in prostate cancer patients, although its immunoreactivity is possibly not restricted to CD146 associated epitopes.