Kenjiro Imada

Mutual regulation between Raf/MEK/ERK signaling and Y-box-binding protein-1 promotes prostate cancer progression

Purpose: Y-box–binding protein-1 (YB-1) is known to conduct various functions related to cell proliferation, anti-apoptosis, epithelial–mesenchymal transition, and castration resistance in prostate cancer. However, it is still unknown how YB-1 affects cancer biology, especially its correlations with the mitogen-activated protein kinase (MAPK) signaling pathway. Therefore, we aimed to examine the interaction between YB-1 and the MAPK pathway in prostate cancer. Experimental Design: Quantitative real-time PCR, Western blotting, and co-immunoprecipitation assay were conducted in prostate cancer cells. YB-1, phosphorylated YB-1 (p-YB-1), and ERK2 protein expressions in 165 clinical specimens of prostate cancer were investigated by immunohistochemistry. YB-1, p-YB-1, and ERK2 nuclear expressions were compared with clinicopathologic characteristics and patient prognoses. Results: EGF upregulated p-YB-1, whereas MEK inhibitor (U0126, PD98059) decreased p-YB-1. Inversely, silencing of YB-1 using siRNA decreased the expression of ERK2 and phosphorylated MEK, ERK1/2, and RSK. Furthermore, YB-1 interacted with ERK2 and Raf-1 and regulated their expressions, through the proteasomal pathway. Immunohistochemical staining showed a significant correlation among the nuclear expressions of YB-1, p-YB-1, and ERK2. The Cox proportional hazards model revealed that high ERK2 expression was an independent prognostic factor [HR, 7.947; 95% confidence interval (CI), 3.527–20.508; P < 0.0001]. Conclusion: We revealed the functional relationship between YB-1 and MAPK signaling and its biochemical relevance to the progression of prostate cancer. In addition, ERK2 expression was an independent prognostic factor. These findings suggest that both the ERK pathway and YB-1 may be promising molecular targets for prostate cancer diagnosis and therapeutics. Clin Cancer Res; 19(17); 4638–50. ©2013 AACR.

Inhibition of Protein Kinase C/Twist1 Signaling Augments Anticancer Effects of Androgen Deprivation and Enzalutamide in Prostate Cancer

Purpose: The progression of prostate cancer to metastatic and castration-resistant disease represents a critical step. We previously showed that the transcription factor Twist1, which promotes epithelial–mesenchymal transition, was involved in castration-resistant progression. Similarly, protein kinase C (PKC) has been implicated in both metastatic progression and castration resistance in prostate cancer. Experimental Design: In this study, we aimed to elucidate the role of PKC/Twist1 signaling in castration resistance, and to apply this information to the development of a novel therapeutic concept using PKC inhibitor Ro31-8220 against prostate cancer using various prostate cancer cell lines. Results: Androgen deprivation and the next-generation antiandrogen enzalutamide induced PKC activation and Twist1 expression, which were reversed by the PKC inhibitor Ro31-8220. Ro31-8220 suppressed cell proliferation in androgen-dependent prostate cancer LNCaP cells, which was augmented by its combination with androgen deprivation or enzalutamide. The favorable anticancer effects of the combination of Ro31-8220 and enzalutamide were also observed in castration-resistant C4-2 and 22Rv1 cells. Furthermore, PKC phosphorylation was elevated in castration-resistant and enzalutamide-resistant cells compared with their parental cells, leading to persistent sensitivity to Ro-31-8220 in castration- and enzalutamide-resistant cells. Conclusions: Taken together, these findings indicate that PKC/Twist1 signaling contributes to castration resistance as well as enzalutamide resistance in prostate cancer, and suggest that therapeutics targeting PKC/Twist1 signaling, such as PKC inhibitors, represent a promising novel therapeutic strategy for prostate cancer, especially castration-resistant prostate cancer, when combined with enzalutamide. Clin Cancer Res; 20(4); 951–61. ©2013 AACR.

The feature of metabolic syndrome is a risk factor for biochemical recurrence after radical prostatectomy

To examine the association between the features of metabolic syndrome (MetS) (obesity, hypertension, diabetes mellitus, and dyslipidemia) and the risk of biochemical recurrence (BCR) after radical prostatectomy in patients with prostate cancer.

Carbonic Anhydrase I as a New Plasma Biomarker for Prostate Cancer

Serum prostate-specific antigen (PSA) levels ranging from 4 to 10 ng/mL is considered a diagnostic gray zone for detecting prostate cancer because biopsies reveal no evidence of cancer in 75% of these subjects. Our goal was to discover a new highly specific biomarker for prostate cancer by analyzing plasma proteins using a proteomic technique. Enriched plasma proteins from 25 prostate cancer patients and 15 healthy controls were analyzed using a label-free quantitative shotgun proteomics platform called 2DICAL (2-dimensional image converted analysis of liquid chromatography and mass spectrometry) and candidate biomarkers were searched. Among the 40,678 identified mass spectrum (MS) peaks, 117 peaks significantly differed between prostate cancer patients and healthy controls. Ten peaks matched carbonic anhydrase I (CAI) by tandem MS. Independent immunological assays revealed that plasma CAI levels in 54 prostate cancer patients were significantly higher than those in 60 healthy controls (P = 0.022, Mann-Whitney U test). In the PSA gray-zone group, the discrimination rate of prostate cancer patients increased by considering plasma CAI levels. CAI can potentially serve as a valuable plasma biomarker and the combination of PSA and CAI may have great advantages for diagnosing prostate cancer in patients with gray-zone PSA level.

Targeting ribosomal S6 kinases/Y-box binding protein-1 signaling improves cellular sensitivity to taxane in prostate cancer

Taxanes are the only cytotoxic chemotherapeutic agents proved to prolong the survival in patients with castration‐resistant prostate cancer. However, because of intrinsic and acquired resistances to taxanes, their therapeutical efficiencies are modest, bringing only a few months of survival benefit. Y‐box binding protein‐1 (YB‐1) promotes cancer cell resistance to various anticancer treatments, including taxanes. Here, we aimed to elucidate the mechanism of taxane resistance by YB‐1 and examined overcoming resistance by targeting YB‐1 signaling.

Potential Role for YB-1 in Castration-Resistant Prostate Cancer and Resistance to Enzalutamide Through the Androgen Receptor V7

BACKGROUND Although androgen deprivation therapy for advanced prostate cancer initially exerts excellent anticancer effects, most prostate cancer treated with androgen deprivation therapy eventually recurs as castration-resistant prostate cancer (CRPC). Although aberrant kinase activation has been proposed as a mechanism of castration resistance, comprehensive kinase profiles in CRPC remain unknown. Therefore, we aimed to elucidate the kinome in CRPC as well as the role of key molecules. METHODS We utilized a kinome array in androgen-dependent LNCaP and castration-resistant CxR cells. The effect of Y-box binding protein-1 (YB-1) on androgen receptor (AR) expression was examined by quantitative polymerase chain reaction and western blot analysis. The association between polymorphisms in the YB-1 gene determined by genotyping and YB-1 expression evaluated by immunohistochemistry in prostate cancer tissues, as well as outcome in metastatic prostate cancer, were investigated by the Cochran-Armitage test and the Cox proportional hazards model, respectively. All statistical tests were two-sided. RESULTS One hundred fifty-six of 180 kinase phosphorylation sites, including ERK and RSK, were activated in CRPC cells, leading to increased phosphorylation of YB-1, which is a key molecule in the progression to CRPC. YB-1 signaling regulated AR V7 expression, and YB-1 inhibition augmented the anticancer effect of enzalutamide. Moreover, polymorphism (rs12030724) in the YB-1 gene affected YB-1 expression in 93 prostate cancer tissues (YB-1 positive rate; 14.3% in TT, 40.0% in AT, and 52.9% in AA, P = .04) and associated with probability of progression in 104 metastatic prostate cancer case patients (AT/TT vs AA, hazard ratio = 0.49, 95% confidence interval = 0.32 to 0.77, P = .001). CONCLUSIONS YB-1 appears to be a promising target to inhibit the development of castration resistance, even at the AR variant-expressing stage. Polymorphism in the YB-1 gene may be a promising predictive biomarker in hormonal therapy.

Crosstalk between epithelial-mesenchymal transition and castration resistance mediated by Twist1/AR signaling in prostate cancer.

Although invasive and metastatic progression via the epithelial-mesenchymal transition (EMT) and acquisition of resistance to castration are both critical steps in prostate cancer, the molecular mechanism of this interaction remains unclear. In this study, we aimed to elucidate the interaction of signaling between castration resistance and EMT, and to apply this information to the development of a novel therapeutic concept using transforming growth factor-β (TGF-β) inhibitor SB525334 combined with androgen-deprivation therapy against prostate cancer using an in vivo model. This study revealed that an EMT inducer (TGF-β) induced full-length androgen receptor (AR) and AR variant expression. In addition, a highly invasive clone showed augmented full-length AR and AR variant expression as well as acquisition of castration resistance. Conversely, full-length AR and AR as well as Twist1 and mesenchymal molecules variant expression were up-regulated in castration-resistant LNCaP xenograft. Finally, TGF-β inhibitor suppressed Twist1 and AR expression as well as prostate cancer growth combined with castration. Taken together, these results demonstrate that Twist1/AR signaling was augmented in castration resistant as well as mesenchymal-phenotype prostate cancer, indicating the molecular mechanism of mutual and functional crosstalk between EMT and castration resistance, which may play a crucial role in prostate carcinogenesis and progression.

Inhibition of RSK/YB‐1 signaling enhances the anti‐cancer effect of enzalutamide in prostate cancer

Previously, we have shown that Y‐box binding protein‐1 (YB‐1) regulates androgen receptor (AR) expression and contributes to castration resistance. However, the mechanism of YB‐1 activation remains unknown. In this study, we aimed to elucidate the mechanism and role of YB‐1 activation in relation to castration resistance as well as enzalutamide resistance, with a view to developing a novel therapeutic concept for castration‐resistant prostate cancer (CRPC) treatment.

The Oncological Outcomes and Risk Stratification in Docetaxel Chemotherapy for Castration-resistant Prostate Cancer

OBJECTIVE To clarify the risk factors and develop a refined risk-stratification model to help in the appropriate selection of docetaxel chemotherapy in patients with castration-resistant prostate cancer. METHODS This study included 97 Japanese patients with castration-resistant prostate cancer who were treated with 70-75 mg/m(2) docetaxel and 10 mg prednisone every 3 or 4 weeks from 2008 to 2013. The oncological outcomes and prognostic significance of clinicopathological factors were analyzed, and significant prognostic factors were used to develop a risk-stratification model. RESULTS Prostate-specific antigen decline was observed in 75 patients (77.3%), including 43 (44.3%) who achieved a prostate-specific antigen decline of ≥ 50%. The median progression-free survival and overall survival were 5.1 and 20.8 months, respectively. Univariate analysis identified performance status, alkaline phosphatase value, visceral metastasis, duration from diagnosis, duration from initiation of hormone treatment and prior treatment with estramustine as significant predictors of overall survival. Among these, alkaline phosphatase value, visceral metastasis and duration from initiation of hormone treatment were independent prognostic factors in multivariate analysis. Furthermore, risk classification according to the number of independent risk factors present effectively stratified survival among docetaxel-treated castration-resistant prostate cancer patients. CONCLUSIONS Oncologic outcomes in Japanese patients with castration-resistant prostate cancer receiving docetaxel chemotherapy were comparable to or slightly better than those in Western populations, and the risk-stratification model developed in this study may help to predict prognosis and contribute to the selection of suitable therapy after castration resistance.

Renal cancer treatment with recipient lymphocyte infusion enhanced the antitumor effect of nonmyeloablative allogeneic stem cell transplantation

BACKGROUND Nonmyeloablative allogeneic stem cell transplantation (SCT) is an option for the treatment of metastatic renal cancer. Mature donor T cells cause graft versus-host disease (GVHD) although they are also the main mediators of the beneficial graft-versus-tumor (GVT) activity associated with this treatment. Hence, the segregation of GVT activity from GVHD is an important challenge in managing the clinical course of treatment. We previously reported a series of studies regarding the allograft tolerance induced by allogeneic spleen cells (with bone marrow cells) and cyclophosphamide in mice. METHODS The aim of the present study was to modify the cyclophosphamide-using cell therapy to reduce the risk of GVHD while preserving the antitumor activity against RENCA, a murine carcinogen-induced renal cell carcinoma with recipient lymphocyte infusion (RLI). RESULTS Regarding the in vivo antitumor effect, there was a significant difference between RLI and no lymphocyte infusion after the cyclophosphamide treatment, whereas the histologic findings of the small intestine showed that the cyclophosphamide-using cell therapy with RLI decreased the risk of GVHD as compared with donor lymphocyte infusion. In addition, the acquired immunity against RENCA was clearly observed in RLI-treated mice. CONCLUSIONS Our results show that RLI during cyclophosphamide-using nonmyeloablative cell therapy can dissociate GVT effects from GVHD by reducing the risk of GVHD. We considered that this was the first report to provide the evidence of nonmyeloablative allogeneic SCT with RLI for the treatment of renal cell carcinoma which never induce complete chimerism.