Identification of the metabolic signatures of prostate cancer by mass spectrometry-based plasma and urine metabolomics analysis.

OBJECTIVE: Prostate cancer (PCa) is one of the most commonly diagnosed cancers among men which is associated with profound metabolic changes. Systematic analysis of the metabolic alterations and identification of new biomarkers may benefit PCa diagnosis and a deep understanding of the pathological mechanism. The purpose of this study was to determine the metabolic features of PCa. METHODS: Plasma and urine metabolites from 89 prostate cancer (PCa) patients, 84 benign prostatic hyperplasia (BPH) patients, and 70 healthy males were analyzed using LC-MS/MS and GC-MS. The Orthogonalised Partial Least Squares Discriminant Analysis (OPLS-DA) was used to find the significantly changed metabolites. The clinical value of the candidate markers was examined by receiver operating characteristic curve analysis and compared with prostate-specific antigen (PSA). RESULTS: Multivariate statistical analyses found a series of altered metabolites, which related to the urea cycle, tricarboxylic acid cycle (TCA), fatty acid metabolism, and the glycine cleavage system. Plasma Glu/Gln showed the highest predictive value (AUC = 0.984) when differentiating PCa patients from healthy controls, with a higher sensitivity than PSA (96.6% vs. 94.4%). Both Glu/Gln and PSA displayed a low specificity when differentiating PCa patients from BPH patients (<53.2%), while the combination of Glu/Gln and PSA can further increase the diagnostic specificity to 66.9%. CONCLUSIONS: The present study showed the metabolic features of PCa, provided strong evidence that the amide nitrogen and the energy metabolic pathways could be a valuable source of markers for PCa. Several candidate markers identified in this study were clinically valuable for further assessment.

Long noncoding RNA HOTAIR regulates the invasion and metastasis of prostate cancer by targeting hepaCAM.

BACKGROUND: The role of HOX transcript antisense RNA (HOTAIR) has been proven to be important in tumorigenesis. However, how this molecule promotes metastasis and invasion in PCa is still unclear. METHODS: The relationship between HOTAIR and hepatocellular adhesion molecule (hepaCAM) in PCa was identified by immunohistochemistry, immunofluorescence, plasmid transfection, quantitative real-time PCR and immunoblotting. The regulatory effects of HOTAIR on hepaCAM and MAPK signalling and their key roles in PCa metastasis were investigated in vitro. RESULTS: The expression of HOTAIR was inversely correlated with hepaCAM in the blood and tissue of PCa patients. Here, hepaCAM was identified as a novel target gene of HOTAIR and was critical for the invasiveness of PCa. HOTAIR recruited PRC2 to the hepaCAM promoter, resulting in high levels of H3K27me3 and the absence of hepaCAM with an abnormally activated MAPK pathway. Both HOTAIR depletion and EZH2 inhibition could induce hepaCAM re-expression with inhibitory MAPK signalling and decrease the invasive and metastatic capabilities of PCa cells. CONCLUSIONS: This study demonstrates that HOTAIR promotes invasion and metastasis of PCa by decreasing the inhibitory effect of hepaCAM on MAPK signalling. Therefore, the HOTAIR/hepaCAM/MAPK axis may provide a new avenue towards therapeutic strategies and prognostic indicators for advanced prostate cancer.

PLCε regulates metabolism and metastasis signaling via HIF-1α/MEK/ERK pathway in prostate cancer.

Phospholipase C-ε (PLCε) is frequently overexpressed in tumors and plays an important role in the regulation of tumorigenesis. Although great progress has been made in understanding biological roles of PLCε, the relevant molecular mechanisms underlying its pro-tumor activity remain largely unclear. Here, we demonstrated that PLCε knockdown reduced cell metastasis, glucose consumption and lactate production in a manner that depended on hypoxia inducible factor 1α (HIF-1α) expression in prostate cancer cells. Interestingly, our findings showed that the expression levels of PLCε were positively associated with those of HIF-1α in clinical prostate carcinoma samples. Knockdown of PLCε impaired HIF-1α levels and transcriptional activity by regulating the extracellular-signal-regulated kinase pathway, and blocking HIF-1α nuclear translocation. Furthermore, PLCε could interact with the von Hippel-Lindau E3 ligase complex to modulate the stability of HIF-1α. Collectively, our findings demonstrate that PLCε could be a crucial positive regulator of HIF-1α, which would promote PLCε-enhanced tumorigenesis.

PLCε regulates prostate cancer mitochondrial oxidative metabolism and migration via upregulation of Twist1.

BACKGROUND: Metabolic rewiring is a common feature of many cancer types, including prostate cancer (PCa). Alterations in master genes lead to mitochondrial metabolic rewiring and provide an appealing target to inhibit cancer progression and improve survival. Phospholipase C (PLC)ε is a regulator of tumor generation and progression. However, its role in mitochondrial metabolism remains unclear. METHODS: The GEO, The Cancer Genome Atlas, and the GTEx databases were used to determine Twist1 mRNA levels in tumors and their non-tumor counterparts. Fifty-five PCa and 48 benign prostatic hypertrophy tissue samples were tested for the presence of PLCε and Twist1 immunohistochemically. An association between PLCε and Twist1 was determined by Pearson's correlation analysis. PLCε was knocked down with a lentiviral short hairpin RNA. Mitochondrial activity was assessed by measuring the oxygen consumption rate. Western blotting analyses were used to measure levels of PPARß, Twist1, phosphorylated (p)-Twist1, p-MEK, p-ERK, p-P38, and p-c-Jun N-terminal kinase (JNK). Cells were treated with inhibitors of MEK, JNK, and P38 MAPK, and an agonist and inhibitor of peroxisome proliferator activated receptor (PPAR) ß, to evaluate which signaling pathways were involved in PLCε-mediated Twist1 expression. The stability of Twist1 was determined after blocking protein synthesis with cycloheximide. Reporter assays utilized E-cadherin or N-cadherin luciferase reporters under depletion of PLCε or Twist1. Transwell assays assessed cell migration. Finally, a nude mouse tumor xenograft assay was conducted to verify the role of PLCε in tumor formation. RESULTS: Our findings revealed that the expression of PLCε was positively associated with Twist1 in clinical PCa samples. PLCε knockdown promoted mitochondrial oxidative metabolism in PCa cells. Mechanistically, PLCε increased phosphorylation of Twist1 and stabilized the Twist1 protein through MAPK signaling. The transcriptional activity of Twist1, and the Twist1-mediated epithelial-to-mesenchymal transition, cell migration, and transcription regulation, were suppressed by PLCε knockdown and by blocking PPARß nuclear translocation. The tumor xenograft assay demonstrated that PLCε depletion diminished PCa cell tumorigenesis. CONCLUSIONS: These findings reveal an undiscovered physiological role for PLCε in the suppression of mitochondrial oxidative metabolism that has significant implications for understanding PCa occurrence and migration.

Phospholipase C (PLC)ε Promotes Androgen Receptor Antagonist Resistance via the Bone Morphogenetic Protein (BMP)-6/SMAD Axis in a Castration-Resistant Prostate Cancer Cell Line.

BACKGROUND Primary therapy for patients with advanced prostate cancer (PCa) consists of androgen deprivation therapy targeting the androgen receptor (AR) axis. However, most tumors progress to castration-resistant prostate cancer (CRPC) within 18-24 months. The purpose of the present study was to investigate the mechanisms through which PCa acquires drug resistance after long-term treatment with AR antagonists. MATERIAL AND METHODS Online database analysis and bioinformatics analysis were performed to identify signaling activated during anti-androgen treatment. MTT assay was used to detect cell viability. RT-qPCR was performed to examine the mRNA expression of the indicated genes. Colony formation assay was performed to observe cell proliferation. Transwell assay was conducted to demonstrate invasive ability. Protein levels were determined by Western blot analysis and immunofluorescence assays. RESULTS An online database search and bioinformatics analysis indicated that bone morphogenetic protein (BMP)-6/SMAD signaling was activated in enzalutamide-resistant LNCaP cells. Furthermore, this signaling interaction was experimentally verified in bicalutamide- and enzalutamide-resistant LNCaP cells, which may be regulated by phospholipase C (PLC)ε and induced cell proliferation and invasion. Of note, a positive correlation was observed between PLCε and BMP-6 in CRPC tissue samples, which may promote bone metastasis and suggests a poor prognosis. CONCLUSIONS The present results suggest that targeting of PLCε/BMP-6/SMAD signaling may increase the sensitivity of CRPC to AR antagonists and inhibit tumor progression.

Simvastatin delays castration­resistant prostate cancer metastasis and androgen receptor antagonist resistance by regulating the expression of caveolin­1.

The failure of androgen deprivation therapy in prostate cancer treatment mainly results from drug resistance to androgen receptor antagonists. Although an aberrant caveolin­1 (Cav­1) expression has been reported in multiple tumor cell lines, it is unknown whether it is responsible for the progression of castration­resistant prostate cancer (CRPC). Thus, the aim of the present study was to determine whether Cav­1 can be used as a key molecule for the prevention and treatment of CRPC, and to explore its mechanism of action in CRPC. For this purpose, tissue and serum samples from patients with primary prostate cancer and CRPC were analyzed using immunohistochemistry and enzyme­linked immunosorbent assay, which revealed that Cav­1 was overexpressed in CRPC. Furthermore, Kaplan­Meier survival analysis and univariate Cox proportional hazards regression analysis demonstrated that Cav­1 expression in tumors was an independent risk factor for the occurrence of CRPC and was associated with a shorter recurrence­free survival time in patients with CRPC. Receiver operating characteristic curves suggested that serum Cav­1 could be used as a diagnostic biomarker for CRPC (area under the curve, 0.876) using a cut­off value of 0.68 ng/ml (with a sensitivity of 82.1% and specificity of 80%). In addition, it was determined that Cav­1 induced the invasion and migration of CRPC cells by the activation of the H­Ras/phosphoinositide­specific phospholipase Cε signaling cascade in the cell membrane caveolae. Importantly, simvastatin was able to augment the anticancer effects of androgen receptor antagonists by downregulating the expression of Cav­1. Collectively, the findings of this study provide evidence that Cav­1 is a promising predictive biomarker for CRPC and that lowering cholesterol levels with simvastatin or interfering with the expression of Cav­1 may prove to be a useful strategy with which to prevent and/or treat CRPC.

PLCε knockdown overcomes drug resistance to androgen receptor antagonist in castration-resistant prostate cancer by suppressing the wnt3a/ß-catenin pathway.

Most prostate cancers (Pcas) develop into castration-resistant prostate cancer (CRPC) after receiving androgen deprivation therapy (ADT). The expression levels of PLCε and wnt3a are increased in Pca and regulate androgen receptor (AR) activity. However, the biological function and mechanisms of PLCε and wnt3a in CRPC remain unknown. In this study, we found that the expression levels of PLCε, wnt3a, and AR were significantly increased in CRPC tissues as well as bicalutamide-resistant-LNCaP and enzalutamide-resistant-LNCaP cells. In addition, PLCε knockdown partly restored the sensitivity of drug-resistant cells to bicalutamide and enzalutamide by inhibiting the activity of the wnt3a/ß-catenin/AR signaling axis. Interestingly, the resistance of LNCaP cells docetaxel is related to PLCε but not the wnt3a/ß-catenin pathway. We also found that the combination of PLCε knockdown and enzalutamide treatment synergistically suppressed cell proliferation, tumor growth, and bone metastasis using in vitro and in vivo experiments. Our study revealed that PLCε is involved in the progression of drug-resistance in CRPC and could be a new target for the treatment of CRPC.

HepaCAM Regulates Warburg Effect of Renal Cell Carcinoma via HIF-1α/NF-κB Signaling Pathway.

OBJECTIVE: To investigate how hepatocyte cell adhesion molecule (hepaCAM) regulates cancer energy metabolism through hypoxia-inducible factor (HIF-1α) in renal cell carcinoma (RCC). MATERIALS AND METHODS: The expression of hepaCAM and HIF-1α in RCC tissue samples was examined by immunohistochemistry. Glucose consumption and lactate production assays were used to detect metabolic activity in RCC cell lines. P65 and IκB kinase (IKKß) mRNA and protein expression were detected using quantitative real-time polymerase chain reaction and western blotting, respectively. Nuclear translocation of P65 was observed by immunofluorescence staining after re-expressing hepaCAM. The luciferase reporter assay was applied to validate the transcriptional activity of HIF-1α. RESULTS: HIF-1α expression was elevated and hepaCAM suppressed in RCC compared with adjacent normal tissues. Furthermore, hepaCAM re-expression significantly decreased glycolytic metabolism in RCC cell lines, and reduced HIF-1α, IKKß, and P65 expression. The expression of HIF-1α, GLUT1, LDHA, and PKM2 were further reduced with combined hepaCAM overexpression and treatment with the NF-κB inhibitor BAY11-7082, compared to hepaCAM overexpression alone. Additionally, hepaCAM decreased the transcriptional activity of HIF-1α and blocked P65 nuclear translocation by the NF-κB pathway. CONCLUSION: Our data suggest that hepaCAM suppresses the Warburg effect via the HIF-1α/NF-κB pathway in RCC, which is a facilitating factor in hepaCAM-reduced tumorigenesis.