Original ArticleAndrogen-deprivation therapy with enzalutamide enhances prostate cancer metastasis via decreasing the EPHB6 suppressor expression
Introduction
Prostate cancer (PCa) is the most commonly diagnosed cancer and the second leading cause of cancer death in men [1], [2], which may involve the development of PCa metastasis [3]. Since the androgen receptor (AR), a classical nuclear receptor that binds androgens to activate gene transcription, plays very important roles in PCa progress [4], targeting these androgen/AR signals with the androgen deprivation therapy (ADT) with various antiandrogens remains as an effective therapy to suppress the PCa progression. However, most of PCa patients will progress into metastatic castration resistant prostate cancer (CRPC) inevitably after an average treatment of 12–18 months [5], [6].
Enzalutamide (Enz, also named MDV3100) is a recently developed powerful antiandrogen with a better capacity to prevent the androgens from binding to the AR and the AR nuclear translocation that results in better suppression of the AR target genes [7]. Enz has been approved recently by the FDA after demonstration of improving the overall survival of 4.8 months in men with metastatic CRPC [8], [9]. However, recent preclinical studies using multiple CRPC cells and in vivo mouse models also indicated that ADT with Enz (ADT-Enz) might have the unwanted side-effects of increasing PCa cell invasion that involves multiple mechanisms [10], [11], [12]. The tumor suppressor EPHB6, is a member of erythropoietin-producing hepatocyte (Eph) tyrosine kinase receptor family that involves migration during embryonic development [13], [14] and cancer invasiveness [15], [16]. However, the linkage of Enz-increased CRPC cell invasion to altering the expression of tumor suppressors, remains unclear.
Recent studies indicated that EPHB6 downregulation was consistently correlated with enhanced aggressiveness and invasiveness in colorectal cancers, non-small cell lung carcinoma, melanoma, and breast cancers [17], [18], [19], [20], [21]. EPHB6 could inhibit the JNK activation following the stimulation with ephrinB1 [22], and EPHB6 could also suppress cancer cells' aggressiveness through interacting with EPHB4 [23]. However, the role of EPHB6 in the progression of CRPC, especially the Enz-increased CRPC cell invasion, has been poorly investigated.
Here, we found Enz could promote CRPC cell invasion via regulating the AR/EPHB6/JNK signals, and targeting this newly identified signaling with the small molecule JNK inhibitor may help us to increase the Enz efficacy to better suppress the metastatic PCa at the castration-resistant stage.
Section snippets
Cell culture
The C4-2 cell line was from Dr. Jer-Tsong Hsieh, UT Southwestern Medical Center, Dallas and CWR22Rv1 cell lines were obtained from American Type Culture Collection (ATCC) and maintained in RPMI 1640 media containing 10% fetal bovine serum (FBS), antibiotics (100 units/ml penicillin, 100 μg/ml streptomycin), and 2 mM glutamine (Invitrogen, Grand Island, NY) in a humidified 5% CO2 environment at 37 °C.
Reagents and materials
GAPDH (6c5), AR (N-20) antibodies were purchased from Santa Cruz Biotechnology. EPHB6 antibody
Clinical surveys indicated that EPHB6 expression is negatively correlated with PCa metastasis and progression
Early studies of EPHP6 suggested that it might function as suppressor in several cancers [17], [18], [19], [20]. The role of EPHB6 in PCa metastasis, especially the impacts on ADT, however, remains unclear. We first performed clinical surveys using the TCGA databases to analyze the linkage of EPHP6 expression to the PCa progression. The results revealed that EPHP6 expression was negatively correlated with PCa Gleason score showing lower EPHP6 expression in patients with higher Gleason score (
Discussion
For PCa patients, metastasis is the primary underlying cause of fatality and only one-third of metastatic PCa patients survive for five years after diagnosis [26]. The detailed mechanisms of PCa metastasis, however, remain to be further elucidated.
ADT-Enz has been reported to improve the survival and quality-of-life of CRPC patients [8], [27]. However, recent clinical and preclinical studies indicated that ADT-Enz might also induce some unwanted side-effects including inducing the
Acknowledgements
We thank Karen Wolf for help with manuscript preparation. This work was supported by NIH grant CA156700 and George Whipple Professorship Endowment, Taiwan Department of Health Clinical Trial and Research Center of Excellence grant DOH99-TD-B-111-004 and the National Natural Science Foundation of China (81072107, 81130041, 81773206, 81472679) and the National Key Research and Development Program (2016YFC0902603).
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2020, Pharmacological ResearchCitation Excerpt :Based on these observations, increase the expression of EPHB6 might be a therapy strategy to prevent or inhibit metastasis formation in NSCLC. However, there are no reports of chemicals targeting EPHB6 apart from enzalutamide, which was reported to bind to the androgen-response-element (ARE) on the EPHB6 promoter and decrease the EPHB6 expression [29,30]. In our study, we found DFX24, a novel PI3Kα inhibitor, significantly upregulated the mRNA and protein expression of EPHB6 through decreasing the promotor methylation of EPHB6 and finally suppressed the cell migration and invasion of A549 cells (Figs. 2–4).
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2020, Biomedicine and PharmacotherapyCitation Excerpt :Furthermore, JNK related signaling pathways involved in prostate cancer progression. Correspondingly, it was found that targeting AR/EPHB6/JNK signaling with SP600125 may block the Enzalutamide (Enz)-increased cell invasion in two CRPC cell lines (C4-2 and CWR22Rv1) [56]. Jazf1 enhanced cell progression and metastasis via regulating JNK/Slug signaling in both LNCaP and DU145 cells [57].
Targeting AR-Beclin 1 complex-modulated growth factor signaling increases the antiandrogen Enzalutamide sensitivity to better suppress the castration-resistant prostate cancer growth
2019, Cancer LettersCitation Excerpt :To investigate whether Enz-resistance was partly due to dysregulation of growth factor signals, we focused on the insulin-like growth factor-1 receptor (IGF-1R) and the epidermal growth factor receptor (EGFR), as their higher expression have been frequently observed in PCa patients and their activations are often correlated with poor prognosis of PCa (Fig. S1A-D) [1,12,43]. We compared the EnzR1-C4-2 cells with their parental Enz-sensitive C4-2 cells (EnzS1-C4-2) for the activation of growth factor signals [10,42], via assaying the phosphorylation of key downstream signaling effectors of the IGF-1R and EGFR, including serine/threonine kinases AKT and ERK, after treating with either EGF or IGF (Fig. 1 and Fig. S2), which could be used to activate these two signals. Before that, the basal phosphorylation levels of AKT and ERK were measured and described in Fig. S1E.
Viewing the Eph receptors with a focus on breast cancer heterogeneity
2018, Cancer LettersCitation Excerpt :EphB6 interactions – with EphA2 and EphB2, with EphA7 and EphA10 and with EphB4 – have been reported; these interactions potentially regulate tumor biologic behavior [17,106,111]. EphB6 downregulation could also be responsible for prostate, gastric and colon cancer metastasis [112–114]. EphB6 overexpression suppresses the in vitro invasiveness whereas its loss results in an aggressive phenotype of MDA-MB-231 cells [115,116].
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2024, Nature Reviews Cancer
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Contributed equally.