NeuroD1 expression in human prostate cancer: can it contribute to neuroendocrine differentiation comprehension?

OBJECTIVES: Neuroendocrine differentiation is a common feature of prostate cancer (pCA). NeuroD1 is a neuronal transcription factor able to convert epithelial cells into neurons. The aim of the study is to investigate NeuroD1 expression and compare it with chromogranin-A, synaptophysin, and CD56 staining in human prostate cell lines and surgical specimens. METHODS: We detected NeuroD1 gene expression, by duplex reverse transcriptase-polymerase chain reaction, in primary human prostate fibroblasts, in EPN, LNCaP, DU145, and PC3 cell lines before and after cAMP exposure, in 6 BPH and 11 pCA samples. Thereafter 166 paraffin sections from normal and neoplastic prostates were stained with NeuroD1, chromogranin-A, synaptophysin, and CD56 antibodies. The relationships between chromogranin-A and NeuroD1 and clinicopathologic parameters were evaluated by multivariate logistic regression analysis. RESULTS: NeuroD1 is inactive in baseline prostate cell lines and BPHs, whereas it is actively expressed in cAMP-treated EPN, PC3, and DU145 cells. In our surgical series, positive chromogranin-A, synaptophysin, CD56, and NeuroD1 staining was detected in 26.5%, 4.3%, 3.1%, and 35.5%, respectively (difference between chromogranin-A and NeuroD1: p<0.05). The multivariate analysis showed a strong association between chromogranin-A and microscopic perineural invasion (OR: 2.49; 95%CI, 0.85-7.32; p=0.097) and a high primary Gleason score (OR: 1.96; 95%CI, 1.14-3.39; p=0.015), whereas NeuroD1 expression strictly correlated to microscopic perineural invasion (OR: 2.97; 95%CI, 1.05-8.41; p=0.04). CONCLUSIONS: Expression of NeuroD1 versus chromogranin-A is more frequent in pCA, and correlates to increased indicators of malignancy in moderately to poorly differentiated pCA, and could be involved in the pathophysiology of the neuroendocrine differentiation of pCA.