Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0376358 (prostate cancer)
 59,338 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Methionine (MET) is required for cell metabolism. MET endogenously synthesized from homocysteine (HCY) supports the proliferation of normal cells, but not that of numerous malignant cells, as shown previously. MET starvation should have an anti-tumour effect, and its deleterious effects on the hosts might be prevented by HCY. Anti-tumour effects of MET starvation must be reinforced by ethionine (ETH), a MET analogue. MET dependency of PC-3, a human prostate cancer cell line, was studied in vitro. Proliferation of PC-3 cells, cultivated in MET-free medium, was 29% compared with growth in MET+HCY- medium. Addition of HCY to MET-free medium increased the proliferation rate to 56%. The concentration of ETH required to decrease the PC-3 cell proliferation rate to 50% (IC50) was 0.5 mg ml(-1) in MET-HCY- medium. ETH-induced inhibition was abolished by MET addition and was reinforced by HCY. PC-3 cell cycle was blocked in the S-G2-phase after 30 h culture in the absence of MET; this blockage was not reversed by addition of HCY. ETH at the IC50 in MET-HCY+ medium blocked DNA replication. Apoptotic cells appeared after 30 h incubation in MET-HCY+ medium only when ETH was added. ATP pools were decreased after 15 h of culture in MET-free medium. In vivo, MET starvation was obtained by feeding tumour-bearing mice a diet containing a synthetic amino acid mixture as the protein supply, in which HCY replaced MET. Given to nude mice bearing xenografted PC-3, from day 1 after grafting and for 3 weeks, this diet inhibited tumour growth (34% on day 20, P < 0.007); this effect was potentiated by ETH (200 mg kg(-1) day(-1) i.p.) (56% on day 20, P < 5 x 10(-5)). The differences between the effects of these two treatments were significant (P < 0.017) and optimal on day 20. These data showed that combination of ETH and HCY slowed the proliferation of prostate cancer cells in vitro and in vivo, decreased ATP synthesis and caused cell cycle arrest and apoptosis. Experimental therapy based on cancer cell MET metabolism deficiency could be efficient for treating advanced prostate cancers refractory to current therapies.
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PMID:Growth of methionine-dependent human prostate cancer (PC-3) is inhibited by ethionine combined with methionine starvation. 918 75

A novel monoclonal antibody has been developed that reacts strongly with human prostatic cancer, especially tumors of high grade. This antibody (7E11C-5) is currently in Phase 3 trials as an imaging agent for metastatic disease. We have cloned the gene that encodes the antigen that is recognized by the 7E11C-5 monoclonal antibody and have designated this unique protein prostate-specific membrane (PSM) antigen. PSM antigen is a putative class II transmembranous glycoprotein exhibiting a molecular size of Mr 94,000. Functionally, class II membrane proteins serve as transport or binding proteins or have hydrolytic activity. Preliminary studies have demonstrated binding of pteroylmonoglutamate (folate) to membrane fractions that also cross-reacted with the PSM monoclonal antibody. We observed substantial carboxypeptidase activity as folate hydrolase associated with PSM antigen. The purpose of our study was to demonstrate that human prostatic carcinoma cells expressing PSM antigen exhibit folate hydrolase activity using methotrexate triglutamate (MTXGlu3) and pteroylpentaglutamate (PteGlu5) as substrates. Isolated membrane fractions from four human prostate cancer cell lines (LNCaP, PC-3, TSU-Prl, and Duke-145) were examined for folate hydrolase activity using capillary electrophoresis. After timed incubations at various pH ranges and in the presence and absence of thiol reagents, separation of pteroyl(glutamate)n derivatives was achieved with an electrolyte of sodium borate and SDS, while absorbance was monitored at 300 nm. The results demonstrate clearly that LNCaP cells, which highly express PSM, hydrolyze gamma-glutamyl linkages of MTXGlu3. The membrane-bound enzyme is an exopeptidase, because it progressively liberates glutamates from MTXGlu3 and PteGlu5 with accumulation of MTX and PteGlu1, respectively. The semipurified enzyme has a broad activity from pH 2.5 to 9.5 and exhibits activity maxima at pH 5 and 8. Enzymatic activity is maintained in the presence of reduced glutathione, homocysteine, and p-hydroxymercuribenzoate (0.05-0.5 mm) but was inhibited weakly by DTT (>/=0.2 mm). By contrast to LNCaP cell membranes, membranes isolated from other human prostate adenocarcinoma cells (PC-3, Duke-145, and TSU-Pr1) did not exhibit comparable hydrolase activity, nor did they react with 7E11-C5 monoclonal antibody. After transfection of PC-3 cells with a full-length 2.65-kb PSM cDNA subcloned into a pREP7 eukaryotic expression vector, non-PSM antigen-expressing PC-3 cells developed immunoreactivity to 7E11-C5 monoclonal antibody and demonstrated folate hydrolase activities and optimum pH activity profiles identical to those of LNCaP cells. The membrane-bound enzymes from both LNCaP- and PC-3-transfected cells also have a capacity to hydrolyze an alpha-linked glutamyl moiety from N-acetyl-alpha-aspartylglutamate. We have identified that PSM antigen is a pteroyl poly-gamma-glutamyl carboxypeptidase (folate hydrolase) and is expressed strongly in human prostate cancer. Cancer cells that express this enzyme are resistant to methotrexate therapy. Those developing future therapeutic strategies in the treatment of prostate cancer that utilize folate antagonists need to consider this mechanism of resistance.
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PMID:Prostate-specific membrane antigen: a novel folate hydrolase in human prostatic carcinoma cells. 981 19

Previous studies have shown that dietary or pharmacological methionine restriction inhibits growth of human prostate cancer cells in vitro or as xenografts in mice. We undertook the present studies to clarify the molecular mechanisms by which methionine restriction inhibits prostate cancer cell growth. We found that PC-3 and DU 145 cells stopped proliferating within six days in growth medium containing homocysteine in place of methionine. In contrast, proliferation of LNCaP cells was only partially inhibited by the absence of methionine. Using flow cytometry, we found that methionine restriction caused PC-3 cells to arrest in all phases of the cell cycle, but predominantly in the G2/M phase, whereas LNCaP cells accumulated exclusively in the G1 phase. Methionine restriction led to accumulation of the cyclin-dependent kinase inhibitors p21 and p27, as determined by Western blot analysis, and inhibited the enzymatic activities of the cyclin-dependent kinases CDK2 and cdc2, as determined by an in vitro kinase assay: However, methionine restriction had little or no effect on CDK2 or cdc2 protein levels. Methionine restriction also induced PC-3 cells to undergo apoptosis, as indicated by the appearance of a typical nucleosomal ladder on gel electrophoresis of genomic DNA. We conclude that methionine restriction has potential as a novel treatment strategy for prostate cancer.
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PMID:Molecular mechanisms of cell cycle block by methionine restriction in human prostate cancer cells. 1134 Oct 37

In vitro exposure of malignant prostate cell lines to ascorbic acid-menadione showed that tumor cells were killed through a mechanism named autoschizis. Experimental animal studies showed that autoschizis is also evident when ascorbic acid-menadione is administered to nude mice with implanted human prostate tumors. Prostate-specific antigen (PSA) is a known serum marker of prostate tumor cells specific activity. Recently, total serum homocysteine has been identified as a marker of tumor cell numbers with sensitivity for early detection of tumor cell death induced by treatments. A clinical trial with prostate cancer patients submitted to the association of ascorbic acid-menadione was performed and PSA/homocysteine was assessed in the follow- up. The early response in serum PSA and homocysteine levels was reported. The results showed that ascorbic acid-menadione produced an immediate drop in tumor cell numbers as assessed by homocysteine levels. Serum PSA levels showed an early rise and later dropped. These results suggest that autoschizis can also be induced by this pharmacological association at the clinical level in prostate cancer patients. Further studies are being performed in order to research if these results can be found with other primary tumors as it was shown in in vitro and experimental models. Ascorbic acid-menadione could be emerging as a new antitumoral chemotherapy.
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PMID:Serum markers variation consistent with autoschizis induced by ascorbic acid-menadione in patients with prostate cancer. 1266 84

Methylenetetrahydrofolate reductase (MTHFR) catalyzes the synthesis of 5-methyltetrahydrofolate, which is involved in the methylation of homocysteine to methionine. Genetic polymorphisms that decrease MTHFR activity result in an altered cancer risk depending on folic acid intake. In this study we examined the C677T and A1298C polymorphisms of the MTHFR gene in specimens from 81 patients with prostate cancer and 42 controls selected from patients with benign prostatic hypertrophy (BPH). Genomic DNA was isolated from archived formaldehyde-fixed and paraffin-embedded tissue blocks. MTHFR genotypes were determined by restriction-fragment-length-polymorphism polymerase chain reaction. The MTHFR polymorphism frequencies in the prostate-cancer and BPH specimens were, respectively, 60% and 48% for 677CC, 31% and 48% for 677CT, 9% and 5% for 677TT, 36% and 43% for 1298AA, 53% and 40% for 1298AC, and 11% and 17% for 1298CC. Although such differences fall within the realm of chance variation (P>0.05), the data suggest that the 677CT genotype may be associated with a reduced risk of prostate cancer: the age-adjusted odds ratio (aOR) was 0.6 [95% confidence interval (CI): 0.3-1.4]; the odds-ratio reduction was similar in both blacks and whites (aOR=0.4 in blacks, and 0.6 in whites); and when polymorphisms at the 677 and 1298 loci were analyzed in conjunction, a lower frequency of the 677CT-1298AA genotype was observed in the patients with prostate cancer (aOR=0.3, 95% CI: 0.1-1.1). This particular genotype, moreover, was associated with lower Gleason score tumors (aOR=0.1 for Gleason-score 7 versus 6 tumors, 95% CI: 0.0-0.7) and earlier stage disease (aOR=0.3 for stage III versus II, 95% CI: 0.3-2.6). These findings suggest that polymorphisms of the MTHFR gene may alter the risk of developing prostate cancer.
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PMID:Polymorphisms in the methylenetetrahydrofolate reductase gene and prostate cancer risk. 1549 40

The role of folate metabolism in cancer development is a topic of much current interest, with maintenance of adequate folate status tending to show a protective effect. Aberrant methylation, primarily hypermethylation of certain genes including tumor suppressors, has been implicated in prostate cancer development. Folate, vitamin B12 and homocysteine are essential for methyl group metabolism and thus also for DNA methylation. We related plasma levels of these factors to prostate cancer risk in a prospective study of 254 case subjects and 514 matched control subjects. Increasing plasma levels of folate and vitamin B12 were statistically significantly associated with increased prostate cancer risk, with an odds ratio of 1.60 (95% CI = 1.03-2.49; p(trend) = 0.02) for folate and 2.63 (95% CI = 1.61-4.29; p(trend) < 0.001) for vitamin B12 for highest vs. lowest quartile. Increasing plasma homocysteine levels were associated with a reduced risk of borderline significance (OR = 0.67; 95% CI = 0.43-1.04; p(trend) = 0.08). After adjustment for the other 2 plasma variables, body mass index and smoking, a statistically significant increased risk remained only for vitamin B12 (OR = 2.96; 95% CI = 1.58-5.55; p(trend) = 0.001). Adjusted OR for folate and homocysteine were 1.30 (95% CI = 0.74-2.24; p(trend) = 0.17) and 0.91 (95% CI = 0.51-1.58; p(trend) = 0.60), respectively. Our results suggest that factors contributing to folate status are not protective against prostate cancer. On the contrary, vitamin B12, associated with an up to 3-fold increase in risk, and possibly also folate, may even stimulate prostate cancer development. These findings are novel and should be explored further in future studies.
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PMID:Plasma folate, vitamin B12, and homocysteine and prostate cancer risk: a prospective study. 1549 34

Methionine metabolism provides two key cellular reagents: S-adenosylmethionine and glutathione, derived from the common intermediate, homocysteine. A majority of cancer cells exhibit a methionine-dependent phenotype whereby they are unable to grow in medium in which methionine is replaced by its precursor, homocysteine. Additionally, CpG island hypermethylation of tumor suppressor gene promoters is observed in a background of global hypomethylation in cancerous cells. In this study, we have profiled the expression levels of the homocysteine junction enzymes, methionine synthase (MS), MS reductase (MSR), and cystathionine beta-synthase (CBS) in the NCI60 panel of cancer cell lines. The doubling time of non-small lung cell cancer lines, which exhibit the lowest levels of MS within the panel, was significantly correlated with expression of MS. The ratio of MS to MSR varied over a 5-fold range in the different cell types, which may modulate methionine synthesis. Interestingly, markedly reduced CBS expression was seen in the methionine-dependent prostate cancer cell line, PC-3, but not in the methionine-independent cell line, DU-145. However, neither provision of the transsulfuration pathway product, cysteine, nor overexpression of CBS rescued the growth impairment, indicating that reduced CBS was not responsible for the methionine-dependent phenotype in this cell line.
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PMID:Expression profiling of homocysteine junction enzymes in the NCI60 panel of human cancer cell lines. 1573 45

It has been proposed that folate and polymorphisms of the enzyme methylenetetrahydrofolate reductase (MTHFR), which regulates influx of folate from DNA synthesis and repair to methylation reactions, are involved in the aetiology of cancer. To relate the MTHFR 677C-->T and 1298A-->C polymorphisms to the risk of prostate cancer, taking into consideration prospective plasma levels of folate, vitamin B12 and homocysteine. The design was a case-control study of 223 prostate cancer cases and 435 matched controls nested within the population-based Northern Sweden Health and Disease Cohort. Neither the MTHFR 677C-->T nor the MTHFR 1298A-->C polymorphism was statistically significantly associated with the risk of prostate cancer in univariate analysis by conditional logistic regression. After adjustment for MTHFR 1298A-->C, plasma folate, vitamin B12, homocysteine, body mass index and smoking, the odds ratios were, for the 677 CT genotype, 1.52 [95% confidence interval (CI) 1.02-2.26], and for TT, 0.91 (95% CI 0.41-2.04). Our previously reported observation of a possible increase in the risk of prostate cancer at high plasma folate levels was attributable in this study to subjects having the MTHFR 677C-->T polymorphism. We found that the MTHFR 677C-->T polymorphism is not likely to have a major role in the development of prostate cancer, although it may possibly increase the risk in combination with high plasma folate levels. Further investigation in larger studies is warranted.
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PMID:Polymorphisms of methylenetetrahydrofolate reductase and the risk of prostate cancer: a nested case-control study. 1637 29

Clearance of homocysteine via the transsulfuration pathway provides an endogenous route for cysteine synthesis and represents a quantitatively significant source of this amino acid needed for glutathione synthesis. Men have higher plasma levels of total homocysteine than do women, but the mechanism of this sex-dependent difference is not known. In this study, we investigated regulation by testosterone of cystathionine beta-synthase (CBS), which catalyzes the committing step in the transsulfuration pathway. We report that testosterone downregulates CBS expression via a posttranscriptional mechanism in the androgen-responsive prostate cancer cell line, LNCaP. This diminution in CBS levels is accompanied by a decrease in flux through the transsulfuration pathway and by a lower intracellular glutathione concentration. The lower antioxidant capacity in testosterone-treated prostate cancer cells increases their susceptibility to oxidative stress conditions. These results demonstrate regulation of the homocysteine-clearing enzyme, CBS, by testosterone and suggest the potential utility of targeting this enzyme as a chemotherapeutic strategy.
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PMID:Testosterone regulation of homocysteine metabolism modulates redox status in human prostate cancer cells. 1785 88

The cardio protective effect of estrogen in women has come under scrutiny as recent evidence from long-term trials has demonstrated negative findings. In contrast, the effect of endogenous sex hormones, specifically estrogen, on cardiovascular disease, inflammation and clotting parameters in men has not been well-studied. Men receiving androgen deprivation therapy for prostate cancer provide a unique model to study the effect of estrogen alone on inflammation and clotting factors. In a short-term randomized controlled trial of 17-beta estradiol (E(2)) versus placebo, we measured sex hormones, markers of inflammation including homocysteine (HC), C-reactive protein (CRP), interleukin-6 (IL-6) and coagulation factors including fibrinogen, plasminogen activator-inhibitor-1 (PAI-1) and anti-thrombin-III (AT-III) in 27 older men without bone metastases receiving androgen deprivation therapy or neoadjuvant treatment for prostate cancer. After 9 weeks of E(2) treatment, there was no difference in inflammation or clotting parameters between groups, but after 9 weeks of treatment AT-III increased in the E(2) treated group and decreased in the placebo group. CRP, homocysteine and IL-6 did not show any significant differences. We also evaluated the above parameters in 12 men 3 weeks after acute steroid withdrawal with androgen deprivation therapy and found no significant changes. We found an increase in AT-III in men receiving E(2) which may be related to gonadal steroid withdrawal, but no significant differences in other inflammatory or clotting factor parameters. While the current report is very preliminary in a small group of subjects, further studies are needed to determine the long-term effects of E(2) in this population of hypogonadal men.
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PMID:The effect of short-term estradiol therapy on clotting and inflammatory markers in older men receiving hormonal suppression therapy for prostate cancer. 1857 58


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