High KI67 expression is associated, in a multi-variate model, with lower risk of biochemical recurrence in prostate cancer patients following radical prostatectomy

21112

Background: The prediction of disease progression in prostate cancer patients following radical prostatectomy (RP) remains problematic. The use of molecular markers could offer a better stratification of patients more at risk of progression. As such, we recently reported that nuclear ErbB3 was associated with Gleason score and hormone-refractory status. The objective of this study was to evaluate whether ErbB3 could predict overall biochemical recurrence (BCR). In addition, we evaluated if three nuclear markers known to be associated with progression (Cyclin D1, Ki67 and androgen receptor) were more significant predictors of BCR than ErbB3 alone or in combination. Methods: Using immunohistochemistry, we analyzed a tissue microarray containing 373 cores from 63 RP specimens. No patient had received hormone therapy prior to surgery and prior to BCR. The quantitative analysis of nuclear staining was measured by two independent observers (ErbB3, Cyclin D1 and AR) or with the ImagePro Plus softwareTM (Ki67). Marker expressions were categorized as either positive or negative according to the median expression. Results: Of the four markers analyzed, Ki67 alone was the strongest predictor of overall BCR. In a multi-variate Cox regression model (backward conditional), while controlling for the pre-operative PSA, Gleason score and lymph node invasion at time of surgery, KI67 was found to be an independent predictor of BCR with a KI67+ patients having lower risk of BCR (HR=-2.51, p=0.015, CI 95%: 1.19–5.29). We then analyzed if different marker combinations could predict BCR. Patients positive for nuclear AR or AR+/Cyclin D1+ double positive were found to have lower risk of BCR (Kaplan-Meier, p=0.047 and p=0.026, respectively). However, in the multi- variate model, the combinations of Cyclin D1+/AR+ (HR=-2.28, p=0.053, CI 95%: 0.94–5.49), ErbB3+/Ki67+ (HR=-2.43, p=0.034, CI 95%: 1.07- 5.52) and AR+/Ki67+ (HR=-2.32, p=0.049, CI 95%: 1.01–5.35) could not improve on the predictive value of KI67 alone. Conclusions: The major new finding of the study is that patients positive for KI67 expression were at a lower risk of developing BCR, which contrast previously published results, and warrants further investigations.

No significant financial relationships to disclose.

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.

ErbB3, Cyclin D1 and Ki67 nuclear staining predicts biochemical recurrence in prostate cancer treated by radical prostatectomy

10096

Background: The nuclear accumulation of growth factor receptor was reported to be associated to increased cell proliferation. Cyclin D1 and Ki67 are nuclear markers of cell proliferation. Deregulation of Cyclin D1 and Ki67 expression play a role in tumorigenesis and metastasis. Recently, we observed that nuclear localization of ErbB3 was associated with prostate cancer progression. The objective of this study was to determine if the association of cell proliferation markers and nuclear localization of ErbB3 could predict biochemical recurrence (BCR) in patients with prostate cancer following radical prostatectomy. Methods: Using immunohistochemistry we analyzed a tissue microarray containing 386 cores from 64 formalin-fixed paraffin embedded specimens from prostate cancer patients who had undergone radical prostatectomy. No patient had received hormone therapy prior to surgery and prior to BCR. Antibodies against Cyclin D1, ErbB3 and Ki67 proteins were used. Results: Nuclear staining was 60%, 67% and 86% for Cyclin D1, ErbB3 and Ki67 respectively. In our cohort, 29 of 64 PCa patients (45%) had a BCR after a median 3 years of follow-up. Thirty seven (37) percent of patients had positive nuclear staining for all three markers. BCR free survival probability at 3 years was not significant for each marker individually, except for ErbB3 in positive surgical margin patients. When all three markers were combined for nuclear staining Kaplan-Meier analysis BCR free was 0.4 and 0.1 for positive and negative nuclear staining respectively (p=0.0068). Univariate COX regression analysis shows a 2.98 fold (95% CI: 1.29 - 6.86, p=0.01) higher rate of BCR in patients positive for these three markers. In addition, in a multivariate model, including pre-operative PSA (p=0.19), pathologic stage (p=0.29), Gleason grade (p=0.40) and specimens that had positive nuclear staining for the 3 markers were associated with a 3.97 fold higher rate of BCR (95% CI: 1.54 - 10.25, p=0.0068). Conclusion: These results suggest that the association of cell proliferation markers and nuclear localization of ErbB3 could be useful in predicting recurrence following radical prostatectomy and guide therapeutic decisions. Large scale trials are needed to confirm these results.

No significant financial relationships to disclose.

A ligand-independent androgen receptor function protects from inositol hexakisphosphate-induced cell death

14566

Background: The androgen receptor (AR) is often aberrantly expressed or activated in hormone-refractory (HR) prostate cancer (PCa). Though it is not clear whether this is directly linked to AR expression, various cell survival pathways are over-activated in HR-PCa, which is characterized by its poor clinical outcome and resistance to available therapies. Inositol hexakisphosphate (IP6) is a phytochemical anti-cancer agent, which we have found to be more effective in PCa cell lines that do not express the AR. Our goal was to address the mechanism of IP6-induced cell death and to evaluate if and how the AR may interfere with its activity. Methods: We used LNCaP, DU145, 22Rv1 as well as wild-type PC3 and AR-expressing PC3 (PC3AR) cell lines to assess the metabolic toxicity of IP6 by WST-1 assay in normal, androgen-supplemented, and androgen-depleted cell culture conditions. A siRNA targeting the androgen receptor (AR) was used to control for genuine AR-mediated effects in the PC3/PC3AR cell lines. Apoptosis was quantified using fluorogenic caspase-3 assays as well as quantitative DNA fragmentation assays. Expression of a variety of genes involved in apoptosis and cell survival pathways was evaluated by real time PCR. Results: While the activity of IP6 was not modulated by the presence of androgens for any cell line, PC3AR cells were significantly more resistant to IP6 than wild-type PC3 cells according to WST-1, caspase-3 and DNA fragmentation assays (p < 0.05). Down-regulation of the AR in the PC3AR cell line resulted in increased metabolic toxicity of IP6 on these cells (p < 10−5). Although treatment with IP6 resulted in the up-regulation of the pro-apoptotic genes Puma, Noxa, as well as of IRF-2 and IkB-αλπηα in PC3 cells, this did not occur in PC3AR cells (p < 0.05). Conclusion: We conclude that, at least in PC3/PC3AR, cells IP6 sensitivity is linked to a ligand-independent function of the AR. To our knowledge, this is the first report of a ligand-independent AR function involved in resistance to a cytotoxic compound. Establishing the molecular details of this novel function is a major part of our ongoing research.

No significant financial relationships to disclose.

Regulation of IKKe expression by androgen receptor and NF-kB transcriptional factor in prostate cancer

10106

Background: In unstimulated cells, NF-kB transcription factor is sequestered in the cytoplasm as an inactive p65/p50 dimer through interaction with a member of the inhibitor of kB protein family (IkBa). Prominent constitutive activation of NF-kB was observed in prostate cancer (PCa) cell lines lacking androgen receptor (AR) expression (PC3 and DU145) whereas only very low levels of NF-kB activity were seen in androgen-dependent cell lines (LNCaP and CWR22Rv1). As IkB kinase-e (IKKe) has recently been shown to be controlled by NF-kB, we hypothesize that IKKe may be involved in PCa progression based on its interaction with the NF-kB protein, and that these interactions are influenced by AR signaling. Methods: LNCaP cells were used to study IKKe expression with or without stimulation by the analog of androgen R1881 and by the tumor necrosis factor (TNF)-a. IKKe protein and RNA expression were characterized by immunoblot assay and quantitative PCR, respectively. IKKe expression was then correlated with p65 nuclear localisation. NF-kB activity was inhibited using an IkBa dominant negative construction. Inhibition of AR synthesis was performed using a siRNA against AR. Results: IKKe gene expression was stimulated by TNF-a treatment in LNCaP cells and inhibited by transfection of a dominant negative form of IkBa which prevented the nuclear translocation of p65. We also observed constitutive IKKe expression in hormone-refractory cells. Furthermore, we showed that TNF-a-induced IKKe expression is inhibited by R1881 in hormone-responsive PCa cells and this inhibition was correlated with the modulation of IkBa expression by R1881. Finally, we observed that the expression of IKKe is constitutively induced after blocking AR expression in LNCaP cells. Conclusions:. Our results show that IKKe expression is regulated by NF-kB in PCa cell lines. Moreover, IKKe appears to be down-regulated by ligand-dependent AR signaling through the control of IkBa expression. Further studies will be needed in order to determine the implications of this phenomenon with regard to NF-kB regulation, androgen resistance and effect on PCa progression.

No significant financial relationships to disclose.

Nuclear localization of NF-kappaB p65 in primary prostate tumors is predictive of pelvic lymph node metastases

10077

Background: Pelvic lymph node metastases are associated with a greater risk of prostate cancer recurrence and peripheral metastasis. Unfortunately, markers predictive of lymph node metastasis and/or recurrence after radical prostatectomy are limited and new molecular markers are needed to identify patients at higher risk of progression. NF-kB (p65) is a candidate molecular marker already associated with poor clinical outcomes such as biochemical recurrence and bone metastasis. We have also reported elevated nuclear p65 expression in prostate cancer lymph node metastasis. Pertinent to this issue, we tested whether the nuclear localization of p65 in radical prostatectomy specimens could predict the presence of lymph node metastases. Methods: Following informed consent, 51 patients who underwent radical prostatectomy were included in the study: 20 patients had lymph node metastasis at surgery and 31 patients had no evidence of lymph node metastasis and were used as the control group. All cases in the control group had no biochemical relapse 5 years following radical prostatectomy. NF-kB expression in prostate tumor sections was assessed by immunohistochemistry using a monoclonal NF-kB p65 antibody. The relation between nuclear p65 expression in primary tumors and lymph node metastasis was tested in univariate and multivariate Cox regression models. Results: Primary tumors of metastatic patients had an average of 21.25% of tumor cells with nuclear p65 expression as opposed to 9.42% of tumor cells of control patients (p=0.001). Univariate Cox regression demonstrated a 7.5% increased risk of having lymph node metastases for each percent increase in p65 nuclear staining (p=0.003). In the multivariate model, after controlling for pre-operative PSA (p=0.175), Gleason patterns (p=0.382), pathological stage (p=0.436), extracapsular extension (p=0.243) and seminal vesicle invasion (p=0.016), nuclear p65 was associated with an 8.8% increased risk for lymph node metastases (p=0.024). Conclusion: In univariate and multivariate analyses, p65 nuclear expression was strongly predictive of lymph node invasion. We propose that nuclear NF-kB (p65) may serve as a useful independent molecular marker for stratifying patients at risk for lymph node metastases.

No significant financial relationships to disclose.