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)

In situ photoaffinity labelling of the human androgen receptor has been performed in the LNCaP (Lymph Node Carcinoma of the Prostate) cell line. The covalently labelled receptors were identified by SDS-PAGE. Intact LNCaP cells, incubated with [3H]-R1881 and subsequently irradiated with u.v. light and directly solubilized in SDS-buffer, revealed two photolabelled protein bands at 110 and 50 kDa. Irradiation of intact cells and subsequent isolation of nuclei followed by extraction with 0.5 M NaCl resulted in one major photolabelled protein band at 110 kDa. The labelling of this band could be completely suppressed by a 100-fold molar excess of non-radioactive R1881. Photolabelling of androgen receptors in a cytosolic preparation of LNCaP cells after anion exchange chromatography resulted in a much lower labelling efficiency compared with the in situ labelling procedure, although the androgen receptor was purified 100-fold. The steroid binding domain of the human androgen receptor has been partially mapped with chymotrypsin and S. aureus V8 protease digestion. Proteolytic digestion with chymotrypsin of purified photoaffinity-labelled 110 kDa human androgen receptor resulted in the generation of a 15 kDa peptide which still contains the covalently linked hormone. It is concluded that the in situ photoaffinity labelling technique can be applied successfully for characterization of the steroid binding domain of androgen receptors in prostate cancer cells and in other androgen target cells. Furthermore, it was demonstrated that the human androgen receptor is a monomer with a molecular mass of 110 kDa, of which the steroid binding site is confined to a 15 kDa domain.
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PMID:In situ photolabelling of the human androgen receptor. 326 Mar 9

Pathways of testosterone metabolism in tissue slices and cell suspensions of human benign hyperplastic prostate (BPH) tissue and human prostate cancer cell lines (DU145, HPC-36M, PC-3/MA2 and LNCaP) were investigated. Thin layer chromatography analysis was used to identify the following tritiated metabolites: testosterone, 5 alpha-dihydrostestosterone (DHT), 5 alpha-androstane-3 alpha/3 beta-17 beta-diol (androstanediols), 4-androstene-3,17-dione (androstenedione) and 5 alpha-androstanedione. The predominant pathway for testosterone metabolism in BPH was via 5 alpha-reductase producing 5 alpha-dihydrotestosterone (71% and 75% total metabolites in slices and suspensions incubated for 24 h, respectively). The cancer cell lines DU145 and HPC-36M resembled BPH by metabolizing testosterone predominantly to DHT (68% and 82% total metabolites, respectively), although the rate of metabolism was much lower in the cell lines (0.099 and 0.05 pmol testosterone/mg protein/h in DU145 and HPC-36M) compared to the BPH cell suspensions (6.4 pmol testosterone/mg protein/h). In contrast, PC-3/MA2 contained high 17 beta-HSD activity forming large amounts of 4-androstene-3,17-dione (84% total metabolites), converting testosterone at a rate faster (12.8 pmol testosterone/mg protein/h) than the BPH cell suspensions. LNCaP rapidly converted testosterone exclusively to a glucuronide conjugate (7.4 pmol testosterone/mg protein/h), although after incubation with [3H]-4-androstene-3,17-dione, 5 alpha-reductase activity was demonstrated. LNCaP was the only cell line whose growth and colony-forming ability was stimulated by testosterone and DHT. BPH and all the cell lines tested had 5 alpha-reductase activity, but only the prostate tissue and the cell lines DU145 and HPC-36M converted testosterone predominantly to DHT.
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PMID:Comparison of testosterone metabolism in benign prostatic hyperplasia and human prostate cancer cell lines in vitro. 751 39

The three dimensional structures of human prostate specific antigen (PSA) and glandular kallikrein (hGK) were modeled based on porcine pancreatic kallikrein A. High sequence similarity and conserved framework of serine proteases enabled accurate modeling. The catalytic site region consisting of catalytic triad, residues forming oxyanion hole and main-chain substrate binding residues were conserved. The substrate specificity pocket of PSA resembles that of chymotrypsin and hGK is most related with tonin. The models were used to predict interactions with substrate and inhibitor molecules. The models are valuable in interpreting mutant and epitope mapping data as well as when modifying properties of the proteases or when developing diagnostic detection methods for prostatic cancer.
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PMID:Modeling of prostate specific antigen and human glandular kallikrein structures. 752 61

PSA is a 34-kDa 240-amino-acid glycoprotein produced exclusively by prostatic epithelial cells. PSA is a serine protease, is a member of the kallikrein gene family, and has a high sequence homology with human glandular kallikrein. It has chymotrypsin-, trypsin-, and esterase-like activities. In the serum it is present mainly in a complex form with alpha 1-antichymotrypsin. It is secreted in the seminal plasma and is responsible for liquefaction of the seminal coagulum. The production of PSA proteins appears to be under the control of circulating androgens acting through the androgen receptors. The PSA gene is up-regulated predominantly by androgens at both the protein and mRNA levels. DRE causes minimal changes in the PSA level, while prostate massage, ultrasonography, systoscopic examination, and prostate biopsy can all cause clinically significant elevations. Other conditions, such as prostatitis, prostate intraepithelial neoplasia, acute urinary retention, and renal failure can also elevate the PSA level. The value of PSA as a screening tool is questionable because of the great deal of overlap in PSA levels between BPH and prostate cancer. However, if used in men over 50, in conjunction with DRE and/or ultrasonography, it may become a vital part of the early detection program. PSA's role in determining the clinical and pathological stage is also limited, in spite of the direct correlation between the pathological stage and the PSA level, because of great overlap in the PSA levels in various stages. The most important clinical utility of PSA is in monitoring patients after definitive therapy. PSA is most sensitive and reliable in the detection of a residual tumor, possibly recurrence, or disease progression following treatment, irrespective of the treatment modality. PSA can accurately predict the tumor status and can detect recurrence several months before its detection by any other method. PSA is also a very sensitive and specific immunohistochemical marker for tumors of prostatic origin. Compared to PAP, PSA is a more precise and meaningful marker in all clinical situations. With the development of ultrasensitive assays and the adoption of an international standard PSA calibrator, so that results from multicenter studies can be compared, PSA could become one of the most useful tumor marker in cancer biology.
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PMID:Prostatic specific antigen. 753 74

Prostate-specific antigen (PSA) provides an excellent serum marker for prostate cancer, the most frequent form of cancer in American males. PSA is a 237-residue protease based on sequence homology to kallikrein-like enzymes. To predict the 3-dimensional structure of PSA, homology modeling studies were performed based on sequence and structural alignments with tonin, pancreatic kallikrein, chymotrypsin, and trypsin. The structurally conserved regions of the 4 reference X-ray proteins provided the core structure of PSA, whereas the loop structures were modeled on the loops of tonin and kallikrein. The unique "kallikrein loop" insert, between Ser 95b and Pro 95k of kallikrein, was constructed using molecular mechanics, dynamics, and electrostatics calculations. In the resulting PSA structure, the catalytic triad, involving residues His 57, Asp 102, and Ser 195, and hydrophobic and electrostatic interactions typical of serine proteases were extremely well conserved. Similarly, the 5-disulfide bonds of kallikrein were also conserved in PSA. These results, together with the fact that no major steric clashes arose during the modeling process, provide strong evidence for the validity of the PSA model. Calculation of the electrostatic potential contours of kallikrein and PSA was carried out using the finite difference Poisson-Boltzmann method. The calculations revealed matching areas of negative potential near the catalytic triad, but differences in the positive potential surrounding the active site. The PSA glycosylation site, Asn 61, is fully accessible to the solvent and is enclosed in a positive region of the isopotential map. The bottom of the substrate specificity pocket, residue S1, is a serine (Ser 189) as in chymotrypsin, rather than aspartate (Asp 189) as in tonin, kallikrein, and trypsin. This fact, plus other features of the S1 binding-pocket region, suggest that PSA would prefer substrates with hydrophobic residues at the P1 position. The location of a potential zinc ion binding site involving the side chain of histidines 91, 101, and 233 is also suggested. This PSA model should facilitate the understanding and prediction of structural and functional properties of this important cancer marker.
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PMID:A structural model for the prostate disease marker, human prostate-specific antigen. 753 13

Prostate-specific antigen (PSA) is a tissue-specific serine protease similar in structure to the trypsin-like glandular kallikreins but which is unique inasmuch as the enzyme activity is similar to that of chymotrypsin. The active enzyme is a single chain glycoprotein of 237 amino acids. The major form of PSA in serum is complexed to alpha 1-antichymotrypsin (ACT). A small amount is free, non-complexed despite a large excess of ACT. This suggests that the form in serum lacks enzyme activity. Although serum PSA concentrations are regularly abnormally high (above 4 micrograms/L) in prostate cancer (CAP), the utility of PSA measurements in the early detection of CAP is limited, as many tumors are undetected at a cut-off of 4 micrograms/L. Also, 25% of all men with benign prostate hyperplasia (BPH) have serum PSA levels above 4 micrograms/L. Using assays specially developed to measure free and complexed forms of PSA in serum, we found the proportion of PSA-ACT complexes to be higher in CAP than in BPH, but the ratio of free-to-total PSA in serum to be lower. Using an abnormally low ratio of free-to-total PSA to detect CAP increases diagnostic specificity by 15 to 20%, compared to using a high serum PSA concentration. This suggests that the ratios of free-to-total PSA significantly increase the ability to distinguish BPH from localized CAP. The molecular basis is unclear, but may be related to the high incidence of prostate tumor cells producing both PSA and ACT. This is in contrast to the lack of ACT production in BPH epithelium. Possibly owing to lack of ACT production in BPH areas, conditions are not optimal for complex formation, whereas tumors producing both ACT and PSA may promote the formation of PSA-ACT complexes in CAP.
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PMID:Regulation of the enzymatic activity of prostate-specific antigen and its reactions with extracellular protease inhibitors in prostate cancer. 754 78

Suramin has shown antitumour activity in vitro and in vivo. At plasma levels higher than 200 microM there is, however, excessive toxicity. We have, therefore, attempted to improve the antitumour effects of suramin in vitro by combining it with several other antitumour agents. The MCF-7 mammary carcinoma and PC3 prostate cancer cell lines were exposed continuously to suramin and the other agents for 6 days. The sulphorhodamine B (SRB) assay was used for the assessment of growth inhibition. The dose-response interactions were evaluated using the median-effect analysis with the Chou and Talalay computer programme. In the MCF-7 cell line, the combination of suramin plus doxorubicin (DXR), cisplatin (CDDP), 5-fluorouracil (5-FU) or tumour necrosis factor (TNF) resulted in synergistic growth inhibition, whilst its combination with miltefosine (HPC) was antagonistic. In the PC-3 cell line, suramin plus CDDP or TNF was synergistic, whilst its combination with DXR, 5-FU and HPC was antagonistic. All tested combinations with interferon-alpha (IFN-alpha), interferon-gamma (IFN-gamma) and with the combination of both IFN-alpha+IFN-gamma were not synergistic. The synergistic effect of suramin with DXR was schedule dependent. Pretreatment (addition of DXR on day 1 and suramin on days 2-5) was additive at the IC50 level, in both cell lines. Addition of DXR at day 5 was more effective than simultaneous exposure. We found a synergistic effect for the combination of suramin with CDDP and TNF in both cell lines. In addition the combination with DXR and 5-FU was synergistic in MCF-7. Sequential administration of DXR-suramin or suramin-DXR increased the growth inhibition.
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PMID:The synergistic and antagonistic effects of cytotoxic and biological agents on the in vitro antitumour effects of suramin. 783 16

The prostate specific antigen (PSA) level represents all of the immunoreactive serum PSA, either free or bound to alpha-1-anti-chymotrypsin. Isolated assay of free PSA has demonstrated a higher free PSA/total PSA ratio in cases of benign prostatic hyperplasia (BPH) than in cases of cancer, suggesting the possible use of this ratio in the detection of prostatic cancer when the PSA level is between 4 and 10 ng/mL. We retrospectively assayed free PSA in 64 cases of localized prostate cancer, 90 cases of BPH before transurethral resection and 59 healthy controls. By comparing the mean values of the 3 populations and the ROC curves, we confirmed the superiority of the free PSA/total PSA ratio over total PSA in the detection of prostatic cancer, but these results, established in a retrospectively constituted population, need to be confirmed by prospective epidemiological studies. Nevertheless, in routine urological practice, we propose that free PSA assay be performed in all men with a PSA level between 4 and 10 ng/mL and a normal prostate on digital rectal examination.
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PMID:[Clinical assessment of free serum prostate specific antigen (PSA)]. 876 91

Prostate-specific antigen (PSA) is a serine protease secreted by both normal prostate glandular cells and prostate cancer cells. The major proteolytic substrates for PSA are the gel-forming proteins in semen, semenogelin (Sg) I and II. On the basis of the PSA cleavage map for Sg I and II, a series of small peptides (i.e., < or = 7 amino acids) was synthesized and coupled at the COOH terminus to 7-amino-4-methyl coumarin. Using these fluorescently tagged substrates, K(m)s and k(cat)s were determined for PSA hydrolysis, and the substrates were also tested for activity against a panel of purified proteases. Previously, a variety of chymotrypsin substrates have been used to assay the enzymatic activity of PSA. The present studies have identified a peptide sequence with a high degree of specificity for PSA (ie., no detectable hydrolysis by chymotrypsin) and improved K(m)s and k(cat)s over previously used substrates. On the basis of these parameters, the best peptide substrate for PSA has the amino acid sequence HSSKLQ. Using PC-82 human prostate cancer xenografts and human prostate tissues, this PSA substrate was used to document that prostate cancer cells secrete enzymatically active PSA into the extracellular fluid but that once in the blood, PSA is not enzymatically active. On the basis of this information, it should be possible to use the HSSKLQ peptide as a carrier to target peptide-coupled prodrugs for selective activation within sites of PSA-secreting, metastatic prostate cancer cells and not within the blood or other nonprostatic normal tissues.
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PMID:Specific and efficient peptide substrates for assaying the proteolytic activity of prostate-specific antigen. 935 59

Prostate cancer is currently the most common malignancy among men in Sweden, and an estimated 5-10 per cent of cases are hereditary. Several epidemiological studies have shown men whose close relatives are affected to be at 2-4-fold increased risk of developing prostate cancer. In a recent genetic linkage study of 91 Swedish and North American families with hereditary prostate cancer, the first susceptibility locus, HPC 1 (hereditary prostate cancer 1), was localised at positions 1q24-25 on the long arm of chromosome 1. In Sweden, we recommend men with a strong family history of prostate cancer to undergo annual prostate-specific antigen testing and digital rectal examination from the age of 50.
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PMID:[Gene for hereditary prostatic cancer has been located. New possibilities for early identification of men at risk]. 956 39


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