Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
The Prostate-cancer Metabolome Prostate Cancer New MarkerSarcosine Found in Urine and Tumor Tissue Lei Wang 2/27/09 Introduction cancer — the most frequently diagnosed cancer in men — is a main cause of morbidity and mortality Current clinical effective diagnoses: Prostate Digital rectal examination Measure the levels of the enzyme PSA in blood serum Difficulty: High variable examination in PSA among patients; Hard to identify those at high risk of their disease progressing to advanced stages Nature: 12 February 2009 Sreekumar et al. report applying metabolomics to discover biomarker Sarcosine in urine and tissue (P&PCA) that concentration of a small molecule could reveal how advanced a patient's prostate cancer is. And could potentially be used for non-invasive diagnosis and prognostic evaluation of prostate cancer. So, what is metabolomics? Metabolomics In the postgenomic era, cancer researchers survey the genome, transcriptome, proteome, to figure out molecular signatures that distinguish tumors from normal tissues The metabolome is the latest ‘ome’. Analyses of the various ‘omes’ are complementary, but determining the metabolite content of cancer cells — cancer metabolomics — is particularly attractive because it can provide an accurate read-out of tumors’ cellular physiology and biochemical activity. Sreekumar’s experiments Method: both liquid and gas chromatography coupled with mass spectrometry to interrogate the relative levels of metabolites across 262 prostaterelated biospecimens Results: evaluation of the unbiased metabolomic profiles of plasma or urine did not identify robust differences between biopsy-positive and -negative individuals For plasma, 20 out of 478 (4%) metabolites were differential ( Wilcoxon P<0.05), with a false discovery rate (FDR) of 99% For urine, 36 out of 583 (6%) metabolites were differential ( Wilcoxon P,0.05), with a FDR of 67%. Tissue metabolomic profiles: method This includes tissue procurement, histopathological examination, metabolite extraction and separation, mass spectrometrybased detection, spectral analysis, data normalization, delineation of class-specific metabolites and altered pathways, validation of class-specific metabolites and their functional characterization. result Metabolomic alterations of prostate cancer progression. a, Heat map showing 87 differential metabolites in PCA relative to benign samples ( Wilcoxon P<0.05, 23% FDR). b, the relative levels of the 37 named metabolites that were differential between benign prostate and PCA samples. Benign-based z-score plot of named metabolites from a. c, Displays the levels of the 91 named metabolites altered in metastatic samples. Met samples compared to the localized tumors is 4% FDR. As in b except for the comparison between Mets (red) and PCA (yellow), with data represented relative to the mean of the PCA samples. They identify 87 metabolites that distinguish PCA from benign prostate tissue. Of these, six metabolites including sarcosine, uracil, kynurenine, glycerol-3phosphate, leucine and proline were significantly increased on disease progression from benign to PCA to metastatic PCA. Notably, metastatic samples showed markedly increased levels of sarcosine in 79% of the specimens analysed, whereas 42% of the PCA samples showed an increase in the levels of this metabolite and none of the benign samples had detectable levels of sarcosine. The authors further pursued one of these metabolites as a possible biomarker for cancer progression: sarcosine — a derivative of the amino acid glycine . To confirm this pattern of sarcosine increase in cancer progression, they developed a highly sensitive and specific isotope dilution gas chromatography– mass spectrometry (GC–MS) method for accurately quantifying the metabolite from biospecimens Sarcosine levels in prostate-cancer-related tissue specimens (n=89) Next, they monitored sarcosine levels in urine specimens from biopsy-positive and –negative individuals, most of whom have increased levels of prostate-specific antigen (PSA) (>4.0 ng ml-1) and in which prostate needle biopsy was used for diagnosis. Sarcosine levels in urine sediments from men with biopsy-proven prostate cancer (n=49) and prostatebiopsy negative controls (n=44). Notably, an area under the curve (AUC) of 1.0 indicates perfect prediction and an AUC of 0.5 indicates prediction equivalent to random selection. The AUC for sarcosine and PSA for 53 restricted patients samples used in this study having PSA levels in clinical grey zone of 2-10 ng/ml are 0.69 (95 % CI: 0.55, 0.84) and 0.53 (95 % CI: 0.37, 0.69) respectively. To determine whether the sarcosine increase in PCA has biological relevance, they measured its levels in: PCA cell lines: VCaP, DU145, 22RV1 and LNCaP Primary benign prostate epithelial cells: PrEC Immortalized benign RWPE prostate cells Sarcosine levels in invasive prostate cancer cells compared to non-invasive benign prostate epithelial cell lines show increasing To determine whether sarcosine has a more direct role in this process, they added the metabolite to non-invasive benign prostate epithelial cells. Alanine, an isomer of sarcosine, was used as a control for these experiments. Assessment of cell invasiveness of prostate epithelial cells upon exogenous administration of alanine, glycine or sarcosine Sarcosine treatment, however, did not affect the ability of these cells to progress through the different stages of cell cycle or impair cell proliferation Why Glycine can induce cell invasiveness of prostate epithelial cells? This invasion could result from the conversion of glycine to sarcosine by the enzyme glycine-N-methyl transferase (GNMT) In addition to GNMT, sarcosine levels are regulated by sarcosine dehydrogenase (SARDH), this enzyme converts sarcosine back to glycine, and dimethylglycine dehydrogenase (DMGDH), which generates sarcosine from dimethylglycine Knockdown of SARDH in benign prostate epithelial cells (RWPE) resulted in increase in endogenous sarcosine levels with a concomitant 3.5fold increase in invasion sarcosine levels and cell invasiveness after knockdown of GNMT in DU145. Knock-down of dimethylglycine dehydrogenase (DMGDH) attentuates invasion in DU145 prostate cancer cells Other reverse supporting rationale Mice lacking GNMT develop liver cancer with age (Hepatology 2008). Moreover, in a significant proportion of human prostate cancers, GNMT undergoes a phenomenon called loss of heterozygosity — in which one copy of the gene is lost — and the expression of this gene was documented to decrease with prostate-cancer progression (cancer res 2007). Androgen signalling and ETS family of genes (ERG, ETV1) fusions are key factors for PCA progression (Science 2005), they investigated their role in regulating GNMT and SARDH. Treatment with androgen for 48 h in VCaP (ERG-positive) and LNCaP (ETV1-positive) prostate cancer cells resulted in a stepwise increase in GNMT expression and a concomitant decrease in SARDH levels, (qPCR) qRT–PCR analysis of GNMT and SARDH mRNA expression in androgen-stimulated VCaP cells Left, overexpression of ERG or ETV1 in RWPE cells increase sarcosine levels and cell invasiveness. Right, knockdown of TMPRSS2–ERG in VCaP cells decrease sarcosine levels and cell invasiveness. summary Taken together, they explored the metabolome of prostate cancer progression. Identified sarcosine as a key metabolite increased in metastatic PCA and detectable in the urine. Sarcosine and its proximal regulatory enzymes seem to modulate cell invasion and migration. The master transcriptional regulators, AR and ETS gene fusions, seem to regulate directly sarcosine levels by control of its regulatory enzymes, GNMT etc.. Sarcosine pathway may have potential as biomarkers of PCA progression and serve as new avenues for therapeutic intervention. weakness This study just focus on sarcocine level in plasm, urine and prostate (tumor) tissue sample in patients, and ignore patients’ syndrome investigation. At least, should check if cancers associated with GNMT enriched gluconeogenic tissues such as from lung, pancreas and liver. Also in diabetic animal such as sheep and rat are showing increase in GNMT activity and sarcosine change. Animal model experiment or clinical investigation (sample AR level) will enhance the cell culture results such as sarcocine pathway, AR-ERG pathway. AR-ERG pathway in cell culture experiments is not a so strong evidence to modulate sarcocine because most of metastasis PCA that are high sarcocine level, are androgen independent, or just has low level AR. Hypothesis If there is sarcosine level change in tumor tissue or serum in PCA animal model: TRAMP, xenograft model (LNCaP,DU-145) If chemoprevention compounds can modulate metabolism of sarcocine in tumor cell or tissue or body system. Use animal graft model to ascertain which tissue or organ or tumor can produce sarcosine metabolite.