Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027627 (metastases)
 103,950 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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

Human Prostate Specific Membrane Antigen (PSMA), also known as folate hydrolase I (FOLH1), is a 750-amino acid type II membrane glycoprotein, which is primarily expressed in normal human prostate epithelium and is upregulated in prostate cancer, including metastatic disease. We have cloned and sequenced the mouse homolog of PSMA, which we have termed Folh1, and have found that it is not expressed in the mouse prostate, but primarily in the brain and kidney. We have demonstrated that Folh1, like its human counterpart, is a glutamate-preferring carboxypeptidase, which has at least two enzymatic activities: (1) N-acetylated alpha-linked L-amino dipeptidase (NAALADase), an enzyme involved in regulation of excitatory signaling in the brain, and (2) a gamma-glutamyl carboxypeptidase (folate hydrolase). The 2,256-nt open reading frame of Folh1 encodes for a 752-amino acid protein, with 86% identity and 91% similarity to the human PSMA amino acid sequence. Cells transfected with Folh1 gained both NAALADase and folate hydrolase activities. Examination of tissues for NAALADase activity correlated with the mRNA expression pattern for Folh1. Fluorescent in situ hybridization (FISH) revealed Folh1 maps to only one locus in the mouse genome, Chromosome 7D1-2.
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PMID:Cloning, expression, genomic localization, and enzymatic activities of the mouse homolog of prostate-specific membrane antigen/NAALADase/folate hydrolase. 1121 Jan 80

Prostate specific membrane antigen (PSMA) is a folate gamma glutamyl carboxypeptidase that is oriented on the plasma membrane of normal and prostate cancer cells. A cytosolic version of PSMA, PSM', results from alternative splicing of the PSMA gene. Two additional alternatively spliced variants of PSMA, PSM-C and PSM-D, have been described recently. The ratio of PSMA to PSM' mRNA was higher in a small number of prostate cancer specimens compared to normal prostate cancer and benign prostatic hypertrophy (Su et al. Cancer Res 1995;55:1441). The intent of our study was to measure the gene expression of PSMA and the 3 PSMA splice variants in a large number of patient's tissues. A real-time, quantitative PCR assay was developed to quantify PSMA, PSM', PSM-C and PSM-D. Discrimination among the variants was achieved by designing unique primers and TaqMan probes for each gene. Amplification and detection was specific for the desired splice variant and was sensitive to one gene copy per reaction. The assay was used to quantify the gene expression in specimens of normal, benign, primary and metastatic prostate cancer from 72 patients. The mean PSMA expression (relative to 18S rRNA) was 2- to 3-fold lower in normal prostate (n = 4) compared to primary (n = 55, p = 0.31) and metastatic (n = 20, p = 0.33) prostate cancer. There was no difference in the PSMA expression between benign and cancerous prostate tissue from the same patients (n = 35). The ratio of PSMA to PSM' was lowest in the normal prostate and increased with increasing Gleason score (p < 0.001). The increased ratio in these tissues was a reflection of both increasing PSMA levels and decreasing PSM' mRNA. The expression of PSM-C did not differ in any of the tissue categories studied. The expression of PSM-D was similar in normal and primary prostate cancer but was 2-fold higher in lymph node (p < 0.005) and bone metastases (p < 0.05) compared to the primary tumors. Our results of the first detailed quantitative analysis of PSMA mRNA expression in patient's tissues demonstrate that PSMA and the 3 PSMA splice variants are expressed in normal, benign, cancerous and metastatic prostate cancer. We note increased PSMA expression in some malignant tissues, however, these increases are modest in magnitude. We also report that the expression of a novel splice variant, PSM-D, is elevated in prostate cancer metastases.
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PMID:Expression of prostate specific membrane antigen and three alternatively spliced variants of PSMA in prostate cancer patients. 1294 15