Prostate cancer: prognostic significance of the association of heterogeneous nuclear ribonucleoprotein K and androgen receptor expression.

The management of prostate cancer (PCa) remains challenging because to date, there has been no way to distinguish between indolent and aggressive tumors. Heterogeneous nuclear ribonucleoprotein K (hnRNP K) is implicated in the network of mechanisms that control androgen receptor (AR) expression. We studied the expression of the two proteins in PCa to evaluate their prognostic potential and elucidate the hnRNP K function in PCa progression. HnRNP K and AR expression were analyzed immunohistochemically in 105 patients who had undergone radical prostatectomy. The association between the expression of hnRNP K and/or AR and PSA progression or death was evaluated by univariate and multivariate analyses. The expression of hnRNP K was also investigated in vitro using the BPH-1 cell line and two different LNCaP populations that recapitulate the progression of PCa towards a more aggressive disease. AR and hnRNP K were differentially expressed between cancer and normal prostate tissues. A strong association with a good prognosis was evident in PCa exhibiting high percentage of AR-positive cells (>75%) (p≤0.005) and more interestingly, the combination of high AR and low cytoplasmic hnRNP K expression emerged as the most significant independent prognostic marker for PSA failure-free survival, in a multivariate analysis (p≤0.001). In vitro, a higher expression of hnRNP K and pERK was associated with higher PSA levels, suggesting a relationship between hnRNP K phosphorylation and AR-regulated genes. These results indicate that the interaction between the AR and hnRNP K has an important role in the progression of PCa. Changes of the expression of the two proteins are strongly associated with the clinical outcome and may be a potential prognostic marker.