Caffeic acid phenethyl ester suppresses androgen receptor signaling and stability via inhibition of phosphorylation on Ser81 and Ser213.

BACKGROUND: Androgen receptor (AR) plays important role in the development, progression, and metastasis of prostate cancer (PCa). Caffeic acid phenethyl ester (CAPE) is the main component of honey bee propolis. We determined if CAPE affects the signaling and stability of AR in PCa cells. METHODS: Effects of CAPE on AR transcriptional activity and localization were determined by reporter gene assay and immunofluorescent microscopy. Western blotting, fluorescent polarization, computer simulation, and animal experiment were performed to investigate the molecular mechanism how CAPE reduces the stability of AR. RESULTS: CAPE treatment dose-dependently suppressed the transcriptional activity of AR as well as the protein levels of AR and its target gene PSA. Cyclohexamide treatment revealed that androgen stabilized AR protein, but AR stability was diminished by CAPE. Fluorescence microscopy demonstrated that androgen promoted the nucleus translocation of AR in PCa cells, while treatment with CAPE reduced protein level of AR in both nucleus and cytoplasm. CAPE treatment suppressed the phosphorylation of Ser81 and Ser213 on AR, which regulates the stability of AR. CDK1 and AKT are the kinases phosphorylating Ser81 and Ser213 on AR, respectively. CAPE treatment significantly reduced the protein level and activity of CDK1 and AKT in PCa cells. Overexpression of CDK1 or AKT rescued the AR protein level under CAPE treatment. CONCLUSIONS: Our results suggested that CAPE treatment reduced AR stability and AR transcriptional activity in PCa cells, implying the possibility of using CAPE as a treatment for advanced PCa.

Elevation of androgen receptor promotes prostate cancer metastasis by induction of epithelial-mesenchymal transition and reduction of KAT5.

Androgen receptor (AR), an androgen-activated transcription factor, belongs to the nuclear receptor superfamily. AR plays an important role in the development and progression of prostate cancer (PCa). However, the role of AR in PCa metastasis is not fully understood. To investigate the role of AR in PCa metastasis, we examined AR expression level in primary and metastatic PCa by analyzing gene array data of 378 primary prostate tumors and 120 metastatic prostate tumors from Oncomine, as well as carrying out immunohistochemical (IHC) staining of 56 prostate cancer samples. Expression of mRNA and protein of AR as well as its target gene prostate-specific antigen (PSA) was much higher in metastatic prostate tumors than in primary prostate tumors. Knockdown of AR with siRNA or treating with anti-androgen Casodex reduced migration and invasion ability of C4-2B PCa cells. Knockdown of AR increased protein expression of E-cadherin and AR coregulator KAT5 but reduced expression of epithelial-mesenchymal transition (EMT) marker proteins Slug, Snail, MMP-2, vimentin, and ß-catenin. Knockdown of KAT5 increased migration of C4-2B cells, whereas overexpression of KAT5 suppressed cell migration. KAT5 knockdown rescues the suppressive effect of AR knockdown on migration of C4-2B cells. Gene expression level of AR and KAT5 showed a negative correlation. PCa patients with higher AR expression or lower KAT5 expression correlated with shorter recurrence-free survival. Our study suggested that elevation of AR expression and AR signaling in prostate tumors promotes PCa metastasis by induction of EMT and reduction of KAT5.

Caffeic Acid phenethyl ester is a potential therapeutic agent for oral cancer.

Head and neck cancers, which affect 650,000 people and cause 350,000 deaths per year, is the sixth leading cancer by cancer incidence and eighth by cancer-related death worldwide. Oral cancer is the most common type of head and neck cancer. More than 90% of oral cancers are oral and oropharyngeal squamous cell carcinoma (OSCC). The overall five-year survival rate of OSCC patients is approximately 63%, which is due to the low response rate to current therapeutic drugs. In this review we discuss the possibility of using caffeic acid phenethyl ester (CAPE) as an alternative treatment for oral cancer. CAPE is a strong antioxidant extracted from honeybee hive propolis. Recent studies indicate that CAPE treatment can effectively suppress the proliferation, survival, and metastasis of oral cancer cells. CAPE treatment inhibits Akt signaling, cell cycle regulatory proteins, NF-κB function, as well as activity of matrix metalloproteinase (MMPs), epidermal growth factor receptor (EGFR), and Cyclooxygenase-2 (COX-2). Therefore, CAPE treatment induces cell cycle arrest and apoptosis in oral cancer cells. According to the evidence that aberrations in the EGFR/phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signaling, NF-κB function, COX-2 activity, and MMPs activity are frequently found in oral cancers, and that the phosphorylation of Akt, EGFR, and COX-2 correlates to oral cancer patient survival and clinical progression, we believe that CAPE treatment will be useful for treatment of advanced oral cancer patients.

Caffeic acid phenethyl ester suppresses the expression of androgen receptor variant 7 via inhibition of CDK1 and AKT.

Androgen receptor (AR) splice variant 7 (AR-V7) is capable to enter nucleus and activate downstream signaling without ligand. AR-V7 assists the tumor growth, cancer metastasis, cancer stemness, and the evolvement of therapy-resistant prostate cancer (PCa). We discovered that caffeic acid phenethyl ester (CAPE) can repress the expression and downstream signaling of AR-V7 in PCa cells. CAPE blocked the gene transcription, nuclear localization, and protein abundance of AR-V7. CAPE inhibited the expression of U2AF65, SF2 and hnRNPF, which were splicing factors for AR-V7 intron. Additionally, CAPE decreased protein stability of AR-V7 and enhanced the proteosome-degradation of AR-V7. We observed that CDK1 and AKT regulated the expression and stability of AR-V7 via phosphorylation of Ser81 and Ser213, respectively. CAPE decreased the expression of CDK1 and AKT. Overexpression of CDK1 restored the abundance of AR-V7 in CAPE-treated PCa cells. Overexpression of AR-V7, AKT or CDK1 rescued the proliferation of PCa cells under CAPE treatment. Intraperitoneal injection of 10 mg/kg CAPE retarded the growth of 22Rv1 xenografts in nude mice and suppressed the protein levels of AR-V7, CDK1 and AKT in 22Rv1 xenografts. Our study provided the rationale of applying CAPE for inhibition of AR-V7 in prostate tumors.

The miRNAs 203a/210-3p/5001-5p regulate the androgen/androgen receptor/YAP-induced migration in prostate cancer cells.

BACKGROUND: Prostate cancer (PCa) patients with elevated level of androgen receptor (AR) correlate with higher metastatic incidence. Protein expression of AR and its target gene prostate-specific antigen (PSA) are elevated in metastatic prostate tumors as compared to organ-confined tumors. Androgen treatment or elevation of AR promotes metastasis of PCa in cell culture and murine model. However, under androgen depleted condition, AR suppressed cell mobility and invasiveness of PCa cells. Androgen deprivation therapy in PCa patients is associated with higher risk of cancer metastasis. We therefore investigated the dual roles of AR and miRNAs on PCa metastasis. METHODS: The PC-3AR (PC-3 cells re-expressing AR) and LNCaP cells were used as PCa cell model. Transwell migration and invasion assay, wound-healing assay, zebrafish xenotransplantation assay, and zebrafish vascular exit assay were used to investigate the role of AR and androgen on PCa metastasis. Micro-Western Array, co-immunoprecipitation and Immunofluorescence were applied to dissect the molecular mechanism lying underneath. The miRNA array, miRNA inhibitors or plasmid, and chromatin immunoprecipitation assay were used to study the role of miRNAs on PCa metastasis. RESULTS: In the absence of androgen, AR repressed the migration and invasion of PCa cells. When androgen was present, AR stimulated the migration and invasion of PCa cells both in vitro and in zebrafish xenotransplantation model. Androgen increased phospho-AR Ser81 and yes-associated protein 1 (YAP), decreased phospho-YAP Ser217, and altered epithelial-mesenchymal transition (EMT) proteins in PCa cells. Co-IP assay demonstrated that androgen augmented the interaction between YAP and AR in nucleus. Knockdown of YAP or treatment with YAP inhibitor abolished the androgen-induced migration and invasion of PCa cells, while overexpression of YAP showed opposite effects. The miRNA array revealed that androgen decreased hsa-miR-5001-5p but increased hsa-miR-203a and hsa-miR-210-3p in PC-3AR cells but not PC-3 cells. Treatment with inhibitors targeting hsa-miR-203a/hsa-miR-210-3p, or overexpression of hsa-miR-5001-5p decreased YAP expression as well as suppressed the androgen-induced migration and invasion of PCa cells. Chromatin immunoprecipitation (ChIP) assay demonstrated that AR binds with promoter region of has-miR-210-3p in the presence of androgen. CONCLUSIONS: Our observations indicated that miRNAs 203a/210-3p/5001-5p regulate the androgen/AR/YAP-induced PCa metastasis.

Caffeic acid phenethyl ester suppresses proliferation and survival of TW2.6 human oral cancer cells via inhibition of Akt signaling.

Caffeic acid phenethyl ester (CAPE) is a bioactive component extracted from honeybee hive propolis. Our observations indicated that CAPE treatment suppressed cell proliferation and colony formation of TW2.6 human oral squamous cell carcinoma (OSCC) cells dose-dependently. CAPE treatment decreased G1 phase cell population, increased G2/M phase cell population, and induced apoptosis in TW2.6 cells. Treatment with CAPE decreased protein abundance of Akt, Akt1, Akt2, Akt3, phospho-Akt Ser473, phospho-Akt Thr 308, GSK3ß, FOXO1, FOXO3a, phospho-FOXO1 Thr24, phospho-FoxO3a Thr32, NF-κB, phospho-NF-κB Ser536, Rb, phospho-Rb Ser807/811, Skp2, and cyclin D1, but increased cell cycle inhibitor p27Kip. Overexpression of Akt1 or Akt2 in TW2.6 cells rescued growth inhibition caused by CAPE treatment. Co-treating TW2.6 cells with CAPE and 5-fluorouracil, a commonly used chemotherapeutic drug for oral cancers, exhibited additive cell proliferation inhibition. Our study suggested that administration of CAPE is a potential adjuvant therapy for patients with OSCC oral cancer.

Caffeic Acid phenethyl ester as a potential treatment for advanced prostate cancer targeting akt signaling.

Prostate cancer is the fifth most common cancer overall in the world. Androgen ablation therapy is the primary treatment for metastatic prostate cancer. However, most prostate cancer patients receiving the androgen ablation therapy ultimately develop recurrent castration-resistant tumors within 1-3 years after treatment. The median overall survival time is 1-2 years after tumor relapse. Chemotherapy shows little effect on prolonging survival for patients with metastatic hormone-refractory prostate cancer. More than 80% of prostate tumors acquire mutation or deletion of tumor suppressor phosphatase and tensin homolog (PTEN), a negative regulator of PI3K/Akt signaling, indicating that inhibition of PI3K/Akt might be a potential therapy for advanced prostate tumors. Caffeic acid phenethyl ester (CAPE) is a strong antioxidant extracted from honeybee hive propolis. CAPE is a well-known NF-κB inhibitor. CAPE has been used in folk medicine as a potent anti-inflammatory agent. Recent studies indicate that CAPE treatment suppresses tumor growth and Akt signaling in human prostate cancer cells. We discuss the potential of using CAPE as a treatment for patients with advanced prostate cancer targeting Akt signaling pathway in this review article.

Application of Micro-Western Array for Identifying Different Serum Protein Expression Profile among Healthy Control, Alzheimer's Disease Patients and Patients' Adult Children.

(1) Background: Alzheimer's disease (AD) is the most common form of dementia. Increased levels of inflammatory proteins have been observed in brain and plasma samples of AD patients; however, it is not clear if other serum proteins correlate to the development or disease progression of AD. (2) Methods: Micro-Western Array (MWA) is a high-throughput antibody-based proteomics system which allows detection of the expression levels of 24-96 different proteins within 6-30 samples simultaneously. We applied MWA to explore potential serum protein biomarkers correlated to the development and progression of AD by examining the difference in serum protein profile of 31 healthy control (HC), 30 patients with AD and 30 patients' adult children (ACS). (3) Results: Compared to HC, AD and ACS express similar pattern of serum proteins, including higher protein levels of ABCA1, ABCG1, SREBP1 and LXRß but lower protein levels of ApoD, ApoE, ApoH, c_Myc, COX2 and Hippo-YAP signaling proteins. AD patients had higher serum levels of ABCG1, ApoD, ApoH, COX2, LXRα and YAP, but lower levels of ABCA1, ApoE, c_Myc, LATS1, MST1, MST2, Nanog, NFκB_p50, PPARγ and SREBP2, as compared to ACS. Pearson's correlation analysis revealed that the protein expression level of ApoE, c_Myc, LATS1, MST2, NFκB p50, PPARγ and SREBP1 was negatively correlated to age, while that of ApoE, c_Myc, LATS1, MST1, MST2, Nanog, NFκB p50 and PPARγ was positively correlated to age. (4) Conclusions: We identified a group of serum proteins which may correlate to disease progression of AD and can be potential diagnostic serum protein biomarkers.

Androgen suppresses proliferation of castration-resistant LNCaP 104-R2 prostate cancer cells through androgen receptor, Skp2, and c-Myc.

Androgen ablation therapy is the primary treatment for metastatic prostate cancer. However, this therapy is associated with several undesired side-effects, including increased risk of cardiovascular diseases. To study if termination of long-term androgen ablation and restoration of testosterone levels could suppress the growth of relapsed hormone-refractory prostate tumors, we implanted testosterone pellets in castrated nude mice carrying androgen receptor (AR)-positive LNCaP 104-R2 cells, which relapsed from androgen-dependent LNCaP 104-S cells after long-term androgen deprivation. 104-R2 tumor xenografts regressed after testosterone pellets were implanted. Of 33 tumors, 24 adapted to elevation of testosterone level and relapsed as androgen-insensitive tumors. Relapsed tumors (R2Ad) expressed less AR and prostate-specific antigen. We then studied the molecular mechanism underlying the androgenic regulation of prostate cancer cell proliferation. Androgen suppresses proliferation of 104-R2 by inducing G(1) cell cycle arrest through reduction of S-phase kinase-associated protein 2 (Skp2) and c-Myc, and induction of p27(Kip1). 104-R2 cells adapted to androgen treatment and the adapted cells, R2Ad, were androgen-insensitive cells with a slower growth rate and low protein level of AR, high levels of c-Myc and Skp2, and low levels of p27(Kip1). Nuclear AR and prostate-specific antigen expression is present in 104-R2 cells but not R2Ad cells when androgen is absent. Overexpression of AR in R2Ad cells regenerated an androgen-repressed phenotype; knockdown of AR in 104-R2 cells generated an androgen-insensitive phenotype. Overexpression of Skp2 and c-Myc in 104-R2 cells blocked the growth inhibition caused by androgens. We concluded that androgens cause growth inhibition in LNCaP 104-R2 prostate cancer cells through AR, Skp2, and c-Myc.

Androgen receptor inhibits epithelial-mesenchymal transition, migration, and invasion of PC-3 prostate cancer cells.

Bone metastasis is very common in prostate cancer (PCa) and causes severe pain. PC-3 is an androgen receptor (AR)-negative PCa cell line with high metastatic potential established from PCa bone metastasis. We observed that re-expression of AR, which is located in the cytoplasm in the absence of androgen, suppressed cell motility, migration, and invasion of PC-3 cells as determined by wound healing assay and transwell assay. Micro-Western Array and Western blotting analysis indicated that re-expression of AR increased APC, Akt2, Akt3, PI3K p85, phospho-PI3K p85 Tyr458, PI3K p85, and E-cadherin but decreased GSK-3ß, phospho-GSK-3ß Ser9, phospho-mTOR Ser2448, Skp2, NF-κB p50, Slug, N-cadherin, ß-catenin, vimentin, MMP-9, and Snail. Migration and invasion of PC-3 and PC-3(AR) cells were promoted by EGF or IGF-1 but were suppressed by Casodex. Re-expression of AR reduced the activity of MMP-2 and MMP-9 in PC-3 cells. Our observations suggested that re-expressing AR suppresses migration and invasion of PC-3 cells via regulation of EMT marker proteins and MMP activity.

Caffeic acid phenethyl ester induced cell cycle arrest and growth inhibition in androgen-independent prostate cancer cells via regulation of Skp2, p53, p21Cip1 and p27Kip1.

Prostate cancer (PCa) patients receiving the androgen ablation therapy ultimately develop recurrent castration-resistant prostate cancer (CRPC) within 1-3 years. Treatment with caffeic acid phenethyl ester (CAPE) suppressed cell survival and proliferation via induction of G1 or G2/M cell cycle arrest in LNCaP 104-R1, DU-145, 22Rv1, and C4-2 CRPC cells. CAPE treatment also inhibited soft agar colony formation and retarded nude mice xenograft growth of LNCaP 104-R1 cells. We identified that CAPE treatment significantly reduced protein abundance of Skp2, Cdk2, Cdk4, Cdk7, Rb, phospho-Rb S807/811, cyclin A, cyclin D1, cyclin H, E2F1, c-Myc, SGK, phospho-p70S6kinase T421/S424, phospho-mTOR Ser2481, phospho-GSK3α Ser21, but induced p21Cip1, p27Kip1, ATF4, cyclin E, p53, TRIB3, phospho-p53 (Ser6, Ser33, Ser46, Ser392), phospho-p38 MAPK Thr180/Tyr182, Chk1, Chk2, phospho-ATM S1981, phospho-ATR S428, and phospho-p90RSK Ser380. CAPE treatment decreased Skp2 and Akt1 protein expression in LNCaP 104-R1 tumors as compared to control group. Overexpression of Skp2, or siRNA knockdown of p21Cip1, p27Kip1, or p53 blocked suppressive effect of CAPE treatment. Co-treatment of CAPE with PI3K inhibitor LY294002 or Bcl-2 inhibitor ABT737 showed synergistic suppressive effects. Our finding suggested that CAPE treatment induced cell cycle arrest and growth inhibition in CRPC cells via regulation of Skp2, p53, p21Cip1, and p27Kip1.

AKT3 promotes prostate cancer proliferation cells through regulation of Akt, B-Raf, and TSC1/TSC2.

The qRT-PCR analysis of 139 clinical samples and analysis of 150 on-line database clinical samples indicated that AKT3 mRNA expression level was elevated in primary prostate tumors. Immunohistochemical staining of 65 clinical samples revealed that AKT3 protein expression was higher in prostate tumors of stage I, II, III as compared to nearby normal tissues. Plasmid overexpression of AKT3 promoted cell proliferation of LNCaP, PC-3, DU-145, and CA-HPV-10 human prostate cancer (PCa) cells, while knockdown of AKT3 by siRNA reduced cell proliferation. Overexpression of AKT3 increased the protein expression of total AKT, phospho-AKT S473, phospho-AKT T308, B-Raf, c-Myc, Skp2, cyclin E, GSK3ß, phospho-GSK3ß S9, phospho-mTOR S2448, and phospho-p70S6K T421/S424, but decreased TSC1 (tuberous sclerosis 1) and TSC2 (tuberous Sclerosis Complex 2) proteins in PC-3 PCa cells. Overexpression of AKT3 also increased protein abundance of phospho-AKT S473, phospho-AKT T308, and B-Raf but decreased expression of TSC1 and TSC2 proteins in LNCaP, DU-145, and CA-HPV-10 PCa cells. Oncomine datasets analysis suggested that AKT3 mRNA level was positively correlated to BRAF. Knockdown of AKT3 in DU-145 cells with siRNA increased the sensitivity of DU-145 cells to B-Raf inhibitor treatment. Knockdown of TSC1 or TSC2 promoted the proliferation of PCa cells. Our observations implied that AKT3 may be a potential therapeutic target for PCa treatment.

Cholestane-3ß, 5α, 6ß-triol suppresses proliferation, migration, and invasion of human prostate cancer cells.

Oxysterols are oxidation products of cholesterol. Cholestane-3ß, 5α, 6ß-triol (abbreviated as triol) is one of the most abundant and active oxysterols. Here, we report that triol exhibits anti-cancer activity against human prostate cancer cells. Treatment of cells with triol dose-dependently suppressed proliferation of LNCaP CDXR-3, DU-145, and PC-3 human prostate cancer cells and reduced colony formation in soft agar. Oral administration of triol at 20 mg/kg daily for three weeks significantly retarded the growth of PC-3 xenografts in nude mice. Flow cytometric analysis revealed that triol treatment at 10-40 µM caused G1 cell cycle arrest while the TUNEL assay indicated that triol treatment at 20-40 µM induced apoptosis in all three cell lines. Micro-Western Arrays and traditional Western blotting methods indicated that triol treatment resulted in reduced expression of Akt1, phospho-Akt Ser473, phospho-Akt Thr308, PDK1, c-Myc, and Skp2 protein levels as well as accumulation of the cell cycle inhibitor p27(Kip). Triol treatment also resulted in reduced Akt1 protein expression in PC-3 xenografts. Overexpression of Skp2 in PC-3 cells partially rescued the growth inhibition caused by triol. Triol treatment suppressed migration and invasion of DU-145, PC-3, and CDXR-3 cells. The expression levels of proteins associated with epithelial-mesenchymal transition as well as focal adhesion kinase were affected by triol treatment in these cells. Triol treatment caused increased expression of E-cadherin protein levels but decreased expression of N-cadherin, vimentin, Slug, FAK, phospho-FAK Ser722, and phospho-FAK Tyr861 protein levels. Confocal laser microscopy revealed redistribution of ß-actin and α-tubulin at the periphery of the CDXR-3 and DU-145 cells. Our observations suggest that triol may represent a promising therapeutic agent for advanced metastatic prostate cancer.