Gamma-Secretase, ErbB4 nuclear localization and neuregulin expression correlates with prostate cancer patient clinical outcome

10587

Background: Membrane protein ErbB4 is a member of ErbB growth factor receptor family, which can be activated by neuregulins (NRG). Upon neuregulin activation, ErbB4 is cleaved within its transmembrane domain by presenilin γ-secratase (PSN) to release an intracellular domain that translocates into the nucleus. Although, ErbB4 ligand-dependant translocation of ErbB4 to the nucleus and its nuclear activity has been reported in breast cancer cell lines, there are few reports concerning ErbB4 nuclear localization and its clinical relevance. Here, we report for the first time the clinical relevance of ErbB4 nuclear localization, NRG, and PSN expression in prostate cancer tissues. Methods: Immunostaining using anti-ErbB4, anti-PSN2 and anti-neuregulin antibodies was done on a set of tissue microarrays (TMA) from 140 patients. The TMAs contained, 92 cores of normal prostate tissue obtained from 46 autopsy specimens from young males, 373 tumor and normal adjacent cores from 63 hormone sensitive PCa (HSPCa) patients, and 146 cores from 31 hormone refractory PCa (HRPCa) patients. Results: We found a statistically significant increase (p<0.01) in the percentage of ErbB4 nuclear localization (68.7% vs 53.2%), NRG expression (2.06 vs 1.41) and PSN2 expression (2.14 vs 1.53) when comparing cancerous tissues to normal tissue adjacent to cancer. Interestingly, a similar statistically significant increase in nuclear ErbB4 and NRG expression was observed when comparing HRPCa to HSPCa (p<0.001). In cancerous tissues, a strong correlation was found between nuclear ErbB4 and NRG expression (r=0.672), between nuclear ErbB4 and PSN2 expression (r=0.51), and between PSN2 and NRG expression (r=0.71). Nuclear ErbB4 and PSN2 inversely correlated with tumor stage and lymph node invasion. Kaplan Meier analysis of nuclear ErbB4 (p=0.030) and PSN2 expression (p=0.018) showed an inverse association with biochemical recurrence (BCR) of PCa. In multivariate analyses including these three markers and clinical parameters, only nuclear ErbB4 retained an independent prognosis value. Conclusion: Our results suggest that high nuclear ErbB4 along with increased PSN2 expression have a protective effect against prostate cancer progression and BCR.

No significant financial relationships to disclose.

Use of nuclear androgen receptor status to predict early biochemical recurrence of prostate cancer patients

21073

Background: Prostate cancer (PCa) is a leading cause of cancer death in North American men. The androgen receptor (AR) has an established role in the progression of this disease; however, it is unclear at what stage it intervenes. It is also uncertain whether the AR can be a useful prognostic marker for PCa. In this study, we assessed AR expression and sub-cellular localization in normal prostate as well as in androgen sensitive and insensitive PCa (AIPCa) tissues, and evaluated the ability of the AR to predict biochemical recurrence (BCR). Methods: We used tissue micro-arrays containing prostate tissue cores obtained from cancer-free patients (n=43), AIPCa patients (n=36), and patients with hormone-sensitive cancers (n=64) from which were collected both cancerous and normal adjacent tissue. Using immmunohistochemistry, we stained the tissue micro-arrays with a monoclonal antibody recognizing the AR. Two observers assessed the frequency and intensity of both cytoplasmic and nuclear AR staining. AR cytoplasmic (Ci) and nuclear (Ni) indices were calculated by multiplying nuclear staining frequency and nuclear staining intensity. Kaplan Meier, and Cox multivariate analyses were done using SPSS. Results: We found that AR Ci increased significantly in AIPCa although a modest but significant increase in PCa Ci was observed compared to normal tissues. In contrast, AR Ni was significantly lower in cancer-free patients as opposed to that seen in normal tissue adjacent to cancer. Similarly, cancerous tissue exhibited higher AR Ni than its adjacent normal tissue (p<0.05, Kruskal-Wallis). Kaplan Meier analyses revealed that low AR Ni was predictive of an early onset of BCR (before 3-years) in the sub-cohort of hormone-sensitive patients (LR=6.51, p=0.011). Futhermore, low AR Ni remained an independent predictor of early BCR in a Cox multivariate model controlling for age, pre-operative PSA, lymph node invasion, Gleason score and surgical margin status (HR=2.28, 95% CI=1.04 - 5, p<0.05). Conclusions: We conclude that increased nuclear AR activity could be a pre-malignant step in PCa progression whereas its role within cancer cells may be more complex, as low AR nuclear activity was associated with early onset of BCR.

No significant financial relationships to disclose.