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P Vihko

Publications and source records attributed to P Vihko.

At least 73 records · Page 4Linked to original sources
PubMed1995

Expression of active, secreted human prostate-specific antigen by recombinant baculovirus-infected insect cells on a pilot-scale.

We have expressed human prostate-specific antigen (PSA) on a pilot-scale in Spodoptera frugiperda Sf9 insect cells using recombinant baculovirus system. Infected cells secreted PSA into culture medium at a concentration of 2-4 mg per liter. PSA was expressed both in active and inactive forms which were separated in a final purification step using cation-exchange chromatography eluted with a low salt gradient. The N-terminus of active PSA was correctly cleaved; two amino acids of the propeptide remained, however, at the N-terminus of the inactive PSA. Purified recombinant PSA showed a chymotrypsin-like activity with the synthetic substrate MeO-Suc-Arg-Pro-Tyr-pNA, but did not have a trypsin-like activity when Pro-Phe-Arg-pNA was used. The molecular mass of active PSA was 31.0 kDa in reduced SDS-PAGE, 26.0 kDa in nonreduced SDS-PAGE and 26.5 kDa in ion spray mass spectrometry. The active protein formed complexes with alpha 1-antichymotrypsin (ACT) and alpha 2-macroglobulin (alpha 2M) in vitro similar to the commercial PSA purified from human seminal fluid.

Amino Acid Sequence↗
PubMed1995

Mutated human androgen receptor gene detected in a prostatic cancer patient is also activated by estradiol.

Androgens are necessary for the development of prostatic cancer. The mechanisms by which the originally androgen-dependent prostatic cancer cells are relieved of the requirement to use androgen for their growth are largely unknown. The human prostatic cancer cell line LNCaP has been shown to contain a point mutation in the human androgen receptor gene (hAR), suggesting that changes in the hAR may contribute to the abnormal hormone response of prostatic cells. To search for point mutations in the hAR, we used single strand conformation polymorphism analysis and a polymerase chain reaction direct sequencing method to screen 23 prostatic cancer specimens from untreated patients, 6 prostatic cancer specimens from treated patients, and 11 benign prostatic hyperplasia specimens. One mutation was identified in DNA isolated from prostatic cancer tissue, and the mutation was also detected in the leukocyte DNA of the patient and his offspring. The mutation changed codon 726 in exon E from arginine to leucine and was a germ line mutation. The mutation we found in exon E of the hAR gene does not alter the ligand binding specificity of the AR, but the mutated receptor was activated by estradiol to a significantly greater extent than the wild-type receptor. The AR gene mutation described in this study might be one explanation for the altered biological activity of prostatic cancer.

Aged↗
PubMed1994

Structural comparison of human and rat prostate-specific acid phosphatase genes and their promoters: identification of putative androgen response elements.

Structural comparison of human and rat prostate-specific acid phosphatase (hPAP and rPAP) genes indicate that the exon number is different between these species. The hPAP gene contains 10 exons, whereas the rPAP gene was 11 exons. However, exons 2-9 of the genes are identical in size. The 5' regions of the two genes show 71% identity in the most homologous region +1 to +340. The 5' untranslated regions of the human and rat genes are 50 and 49 nucleotides long, respectively. An Alu sequence is present upstream from the proximal promoter of the hPAP gene. Five putative androgen response elements altogether were localized in both the human and rat gene, one of which is conserved in location and sequence between the two genes. Two of these elements in both genes, the conserved one in the proximal promoter region and another one in intron 1, were shown to bind androgen receptor efficiently in vitro.

Acid Phosphatase↗
PubMed1994

Crystal structures of rat acid phosphatase complexed with the transition-state analogs vanadate and molybdate. Implications for the reaction mechanism.

The three-dimensional structures of complexes of recombinant rat prostatic acid phosphatase with the transition-state analogs vanadate and molybdate were determined to 0.3-nm resolution using protein crystallographic methods. The overall structure of the enzyme remains unchanged upon binding of the metal oxyanions; only local conformational differences in the positions of some side chains at the active site were found. The metal oxyanions bind in an identical fashion at the active site with trigonal bipyramidal coordination geometry. The metal ion is within coordination distance of the His12 side chain which is located at one of the axial positions. The three equatorial oxygen atoms interact with the conserved residues Arg11, Arg15, Arg79 and His257. Within hydrogen-bonding distance of the axial oxygen atom is the side chain of the conserved residue Asp258. The implications of these results for the catalytic mechanism of acid phosphatase are discussed.

Acid Phosphatase↗
PubMed1994

Prostate-specific antigen and human glandular kallikrein: two kallikreins of the human prostate.

Prostate-specific antigen (PSA) is a 33 kD protein synthesized in the epithelial cells of the prostate gland. It is a serine protease that belongs to the subgroup of kallikreins, among which it is very similar to a putative enzyme called human glandular kallikrein (hGK-1). Although the hGK-1 enzyme remains to be characterized in vivo, the hGK-1 gene is expressed in the same prostatic epithelial cells as the PSA gene. Expression of the PSA gene is under complex control and the steady-state level of PSA mRNA is increased by androgens, and decreased by epidermal growth factor and activation of protein kinase C. This suggests the existence of several regulatory elements within the cis-acting control elements of the PSA gene. As a seminal serine protease, PSA has been shown to digest the high molecular weight seminal vesicle protein, seminogelin. However, it is likely that this does not constitute the only natural substrate of PSA, as PSA has been shown to degrade insulin-like growth factor-binding protein-3. Serum PSA concentrations are frequently increased in patients with prostatic cancer, but this is also the case in patients with benign prostatic hyperplasia. Thus, PSA measurements alone are not useful as a screening tool for undiagnosed prostatic cancer. However, serum PSA concentrations can be successfully used together with other methods in diagnosing prostatic diseases and in monitoring the successfulness of treatments for prostatic cancer.

Biomarkers, Tumor↗
PubMed1994

Molecular biology techniques in the diagnosis of monogenic diseases.

Monogenic diseases are defined by their patterns of inheritance: autosomal dominant, autosomal recessive, or X-linked. This article examines the molecular biology techniques available for their study and detection. These techniques comprise direct detection of mutations (including trinucleotide repeats) and linkage analysis. The usefulness of these techniques is compared to conventional biochemical tests for the diagnosis of various inherited diseases. The authors stress the need for caution in the interpretation of test results and the importance of genetic counseling.

Forecasting↗
PubMed1993

Evaluation of PAP and PSA gene expression in prostatic hyperplasia and prostatic carcinoma using northern-blot analyses, in situ hybridization and immunohistochemical stainings with monoclonal and bispecific antibodies.

In this report we have investigated levels of prostatic acid phosphatase (PAP) and prostate-specific antigen (PSA) gene expression in prostatic carcinoma (Ca) and benign prostatic hyperplasia (BPH) specimens. Northern-blot analyses of total prostatic mRNA indicated that there was a tendency towards lower amounts of PAP mRNA and PSA mRNA in the Ca specimens than in the BPH specimens, although, because of the great variation in the expression levels of both mRNAs, these differences were not statistically significant. In situ hybridization analyses clearly showed that both PAP and PSA mRNAs were confined to the columnar epithelial cells and that stromal cells were devoid of these mRNAs. In addition, PAP and PSA mRNAs were more abundant in BPH tissue than in adjacent Ca tissue within the same specimen. The levels of PAP and PSA enzymes were analyzed immunohistochemically using a bispecific antibody having high affinity for both PAP and PSA, and the results were compared with those obtained using monoclonal anti-PAP and anti-PSA antibodies. All 3 antibodies stained only epithelial cells and BPH tissue consistently gave more intense staining than Ca tissue. Furthermore, the anti-PSA and the bispecific anti-PAP-PSA antibodies stained well or moderately differentiated Ca tissues more strongly than poorly differentiated Ca tissues. No PSA staining was detected in 3 and no PAP staining in 5 of the moderately or poorly differentiated carcinomas (grades II or III). Our results show that, in comparison with BPH tissue, prostatic Ca tissue is associated with significantly lower levels of mRNAs coding for the prostatic marker enzymes PAP and PSA, as well as with lower concentrations of these enzymes. Furthermore, dedifferentiation of prostate Ca is associated with a decrease in the level of intraprostatic PSA.

Acid Phosphatase↗
PubMed1993

Three-dimensional structure of rat acid phosphatase in complex with L(+)-tartrate.

The crystal structure of recombinant rat prostatic acid phosphatase in complex with the inhibitor L(+)-tartrate was determined to 3-A resolution with protein crystallographic methods. The inhibitor binds at the carboxyl end of the parallel strands of the alpha/beta domain. One of the carboxyl groups of the tartrate molecule interacts with the conserved residues Arg-11, His-12, and Arg-15, which form part of the phosphate binding site. Furthermore, the C2 and C3 hydroxyl groups interact with His-257 and Arg-79. The second carboxyl group is close to Arg-79 but makes no direct hydrogen bonds to the protein. A sequence comparison between tartrate-sensitive and -resistant acid phosphatases suggests that these enzymes have different three-dimensional structures.

Acid Phosphatase↗
PubMed1993

Growth factor regulation of gene expression in the human prostatic carcinoma cell line LNCaP.

In order to characterize the effects of growth factors on the regulation of expression of the genes coding for prostatic differentiation markers, prostatic acid phosphatase and prostate-specific antigen, we studied changes occurring in the biosynthesis of these enzymes in LNCaP prostatic cancer cells treated with growth factors. Epidermal growth factor was found to reduce the secretion of prostatic acid phosphatase and prostate-specific antigen by the cells, as the result of lowered steady-state levels of the corresponding messenger RNAs (mRNAs). In addition, epidermal growth factor (EGF) interfered with the androgen regulation of these genes. EGF evoked these changes in a concentration- and time-dependent fashion, in both the presence and absence of serum and most likely through interactions with the epidermal growth factor receptor, inasmuch as similar effects were achieved by treating the cells with transforming growth factor alpha. The regulation of the human glandular kallikrein 1 gene was quite similar to the regulation of the prostate-specific antigen gene. In addition to the expression of the genes coding for prostatic secretory proteins, the amount of the human androgen receptor mRNA was down-regulated by EGF. This reduction was more pronounced than the autologous down-regulation of human androgen receptor (hAR) mRNA by androgen and could be maintained for at least 5 days. In the presence of androgen, some of the effects of EGF and transforming growth factor alpha on the levels of androgen-regulated mRNAs may be due to down-regulation of the expression of the hAR gene. Transforming growth factor beta 1, which blocked the growth induction of LNCaP cells by EGF, increased the level of prostatic acid phosphatase and hAR mRNAs, but when given to the cells together with EGF its up-regulatory effect could not be discerned. In summary, regulation of the prostatic acid phosphatase and prostate-specific antigen genes is a complex matter, inasmuch as androgens and growth factors regulate the levels of the mRNAs originating from them. Furthermore, the interactions between the androgen-regulatory system and the growth factor-regulatory systems are likely to be at multiple levels in prostatic cells, as suggested by the modulation of the hAR gene expression by these growth factors.

Acid Phosphatase↗
PubMed1993

Rat acid phosphatase: overexpression of active, secreted enzyme by recombinant baculovirus-infected insect cells, molecular properties, and crystallization.

Rat prostatic acid phosphatase (rPAP; orthophosphoric-monoester phosphohydrolase (acid optimum), EC 3.1.3.2) was expressed in the baculovirus expression vector system. Recombinant protein was secreted into the medium at a high yield by infected insect cells, which were cultured at high density in a 30-liter bioreactor allowing high oxygen content for rapidly growing cells. About 20% of the cell protein produced was rPAP. Partial sequence determination of the N terminus of the purified recombinant secreted protein revealed identity to the native secreted protein, showing that the signal peptide is recognized and properly cleaved in insect cells. The enzyme was purified by using L-(+)-tartrate affinity chromatography. The purified protein had a high specific activity of 2620 mumol.min-1.mg-1 with p-nitrophenyl phosphate at the substrate, and it also showed phosphotyrosine phosphatase activity. The molecular mass of the recombinant rPAP was 155 kDa. Two subunits of 46 kDa and 48 kDa could be detected in SDS/PAGE, but only one subunit of 41 kDa was present after digestion with N-glycosidase. The active enzyme is a trimer of subunits differing only in glycosylation. When recombinant rPAP was crystallized with polyethylene glycol 6000 as the precipitant, the crystals were trigonal (space group P3(1)21) with cell dimensions a = 89.4 A and c = 152.0 A. The observed diffraction pattern extends to a resolution of at least 3 A.

Acid Phosphatase↗
PubMed1993

Three-dimensional structure of rat acid phosphatase.

The crystal structure of recombinant rat prostatic acid phosphatase was determined to 3 A resolution with protein crystallographic methods. The enzyme subunit is built up of two domains, an alpha/beta domain consisting of a seven-stranded mixed beta-sheet with helices on both sides of the sheet and a smaller alpha domain. Two disulfide bridges between residues 129-340 and 315-319 were found. Electron density at two of the glycosylation sites for parts of the carbohydrate moieties was observed. The dimer of acid phosphatase is formed through two-fold interactions of edge strand 3 from one subunit with strand 3 from the second subunit, thus extending the beta-sheet from seven to 14 strands. Other subunit-subunit interactions involve conserved residues from loops between helices and beta-strands. The fold of the alpha/beta domain is similar to the fold observed in phosphoglycerate mutase. The active site is at the carboxy end of the parallel strands of the alpha/beta domain. There is a strong residual electron density at the phosphate binding site which probably represents a bound chloride ion. Biochemical properties and results from site-directed mutagenesis experiments of acid phosphatase are correlated to the three-dimensional structure.

Acid Phosphatase↗
PubMed1993

Pilot-scale production of murine monoclonal antibodies in agitated, ceramic-matrix or hollow-fiber cell culture systems.

The purpose of this research was to compare three bioreactor systems for the pilot-scale production of monoclonal antibodies (MAbs). We needed to produce gram quantities of murine MAbs against human prostatic acid phosphatase for use in fragmentation, radiolabeling and in vivo radio-imaging studies. The stable hybridoma cell line secreting IgG1 antibodies was chosen for production. Of the available bioreactor systems, we chose to test an agitating 30-liter bioreactor in repeated batch mode, a ceramic-matrix bioreactor in both repeated batch and continuous perfusion modes and a hollow-fiber bioreactor in continuous perfusion mode. The highest cultured MAb yield, 151 +/- 126 mg/day (mean +/- SD, n = 22), was achieved in the 30-liter bioreactor in repeated batch mode with the MAb being harvested in a large volume of medium, giving a reactor productivity of 4.3 +/ 3.4 mg/liter/day (mean +/- SD, n = 22). The most concentrated MAb was harvested from the continuously perfused hollow-fiber bioreactor, which had the highest reactor productivity, 307 +/ 142 mg/liter/day (mean +/- SD, n = 47) and an average rate of MAb production of 55.3 +/- 25.7 mg/day (mean +/- SD, n = 47). Taking the use of serum into consideration, the cost of MAb production was lowest in the continuously fed and harvested ceramic-matrix and hollow-fiber cell culture systems. A compact blood glucose meter proved to be a novel and suitable device for the rapid monitoring of glucose concentrations in hybridoma cultures.

Acid Phosphatase↗
PubMed1992

Detection of hematogenous micrometastasis in patients with prostate cancer.

The goal of this study was to determine if patients with stage D0-3 prostatic adenocarcinoma have detectable hematogenous micrometastasis. Polymerase chain reaction amplification of prostate-specific antigen mRNA, which is exclusively expressed by prostatic epithelial cells, was used to detect circulating prostatic cells. Peripheral venous blood was obtained from 17 control and 12 prostate cancer patients with stage D0-3 prostatic adenocarcinoma. Of the 12 cancer cases, four patients (stage D1-3) tested positive for prostate-specific antigen RNA, indicating the presence of circulating micrometastasis. The 17 negative controls all tested negative. Contrary to a long held hypothesis, these data point to the possibility that hematogenous metastasis may be a relatively early event in the natural history of human prostate cancer. These findings may have an important impact on our understanding and treatment of prostate cancer.

Base Sequence↗
PubMed1992

Steroids inversely affect the biosynthesis and secretion of human prostatic acid phosphatase and prostate-specific antigen in the LNCaP cell line.

In order to elucidate the mechanism of androgen-regulation of genes expressed only in the prostate gland, the effects of steroid hormones on the biosynthesis and secretion of human prostatic acid phosphatase (PAP) and prostate-specific antigen (PSA) were studied in the human prostatic carcinoma cell line, LNCaP. This cell line produces PAP and PSA, both of which were found to be similar to the proteins purified from and located in human prostatic tissue, as shown by Western blot analysis. The synthetic androgen, R1881, regulated the biosynthesis of these two important tumour marker proteins inversely: the amount of PSA released into the medium was increased to 506% +/- 100 of the control levels, while that of PAP was decreased to 26% +/- 3, in 7 days. These effects were dependent on the concentration of the steroid in the growth medium. The androgen-dependent changes observed in the amounts of the secreted proteins were correlated with alterations in their intra-cellular levels. LNCaP cells were found to have very different capacities for secreting PAP and PSA. Whereas the measurable, cellular amounts of PSA and PAP were of similar magnitudes, much larger amounts of PSA than PAP were secreted into the medium. PSA was also found to be more stable than PAP in the culture medium of the LNCaP cells. Other steroids could elicit effects on PAP and PSA biosynthesis similar to those induced by R1881, and the combined effects of effective concentrations of these steroids were undistinguishable from those caused by each one of them separately, suggesting that all these compounds compete for binding to the same modified androgen receptors of the LNCaP cells. Thus, our results confirm the observations of the altered nature of the LNCaP androgen receptors, and demonstrate the ability of these ligands to produce changes in the expression of androgen-dependent prostatic genes. The fact that the changes observed at the protein level were accompanied by increased levels of PSA mRNAs and by decreased levels of PAP mRNA in steroid-treated cells, suggests that one of the targets of androgen and steroid action in the regulation of these genes is at the mRNA level.

Acid Phosphatase↗