Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In prostate cancer cells, the binding of peptide growth factors to specific receptors increases tyrosine kinases (TK) activity to regulate cell proliferation, cell differentiation, and signaling processes. To determine whether inhibition of receptor TK activity inhibits tumor growth, we studied the effects of a tyrosine kinase inhibitor, RG-13022 (tyrphostin), on cultured human prostate cancer cells. RG-13022 significantly inhibited TGF alpha-induced phosphorylation of EGF receptor (EGFR). This compound inhibited TGF alpha-stimulated [3H]thymidine incorporation in a dose-dependent manner with IC50 being 30 microM. Clonogenicity in soft agar was reduced in the presence of RG-13022. Inhibitory effects were also observed in androgen-positive LNCaP cells and androgen-negative PC3 cells. RG-13022 not only inhibited TGF alpha-induced growth but also growth stimulated by epidermal growth factor (EGF), acidic fibroblast growth factor (aFGF) and serum. In addition, RG-13022 also blocked androgen-stimulated cell proliferation, suggesting that functioning TK pathways are required for androgen-induced growth. This novel synthetic inhibitor may be useful in providing a new strategy for future therapeutic intervention for prostate cancer.
Mol Cell Endocrinol 1996 Mar 01
PMID:Tyrosine kinase inhibitor as a novel signal transduction and antiproliferative agent: prostate cancer. 873 73

We have examined whether keratinocyte growth factor (KGF) and its receptor are expressed in normal, fetal, and prostate cancer cells since KGF may play a role in the growth of adenocarcinomas. In situ hybridization studies with digoxigenin-labeled oligonucleotides (anti-sense and sense controls) were employed to examine KGF and KGF receptor mRNA expression in prostate cancer. We found that the KGF and KGF receptor genes were faintly expressed in the stromal and epithelial cells, respectively, in both fetal (n = 6) and normal adult prostate (n = 6) tissues examined. In 10 benign prostatic hyperplasias (BPH), and in low- and high-grade prostatic carcinoma (32 total), both the KGF gene and the receptor mRNA were expressed in the glandular epithelial cells. KGF was also expressed by the stromal cells in BPH and low-grade carcinoma. Computer assisted system analysis indicated that the intensity of epithelial labeling by both probes was increased in high Gleason score carcinomas ( > 8) and in metastatic nodules. We interpret the data to mean that the paracrine loop in normal prostate may be replaced by an autocrine loop in BPH and adenocarcinomas.
Exp Mol Pathol 1995 Aug
PMID:Keratinocyte growth factor and receptor mRNA expression in benign and malignant human prostate. 875 54

Bombesin and gastrin-releasing peptide (GRP) are potent neuropeptides expressed by prostate cancer neuroendocrine cells and are related to the progression of this malignancy. This study characterizes bombesin receptors in human prostate cancer cell lines (PC-3, DU-145, LNCaP) and assesses the in vitro effect of bombesin on signal transduction and cell proliferation. [125I]Tyr4-bombesin binding assays (37 degrees C) and Scatchard analyses revealed the presence of a single class of high-affinity receptors with similar Kd values (1.5, 1.1 and 3.6 x 10(-10) M in PC-3, DU-145 and LNCaP cells respectively) but with significant differences in the number of binding sites per cell (47.6, 1.5 and 0.1 x 10(3) in PC-3, DU-145 and LNCaP cells respectively). Molecular characterization of the binding sites performed in PC-3 cells by cross-linking experiments and SDS/PAGE revealed a single radioactive band of 85 kDa. To determine which of the three known bombesin receptor subtypes (GRP receptor (GRP-R), neuromedin B receptor, bombesin receptor subtype-3) were expressed in the cell lines, reverse transcription/PCR analysis of cellular RNA followed by hybridization with receptor-specific cDNA was performed. This revealed the presence of GRP-R transcript in all cell lines, while neither of the other two receptor transcripts were expressed. When intracellular calcium mobilization was measured by Fura-2/AM cell labeling and spectrofluorometric monitoring, bombesin (100 nM) induced rapid calcium mobilization in both PC-3 (> 200% of baseline) and DU-145 (> 100% of baseline) cells, but not in LNCaP cells. However, as measured by 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay and [3H]thymidine incorporation, no growth modulation was observed with bombesin or bombesin receptor antagonist at various concentrations (0-500 nM). Our data indicate that bombesin is a potent inducer of signal transduction via GRP-R receptors in androgen-insensitive PC-3 and DU-145 prostate cancer cells. This suggests that the bombesin/GRP family of neuropeptides may play a regulatory role in the biology of androgen-independent prostate cancer.
J Mol Endocrinol 1996 Jun
PMID:Bombesin specifically induces intracellular calcium mobilization via gastrin-releasing peptide receptors in human prostate cancer cells. 878 88

In most patients with prostate cancer, continuous androgen suppression (CAS) therapy causes tumour regression and an accompanying decrease in serum prostate specific antigen (PSA). However, with tumour progression, regulation of both tumour growth and PSA gene expression becomes androgen-independent. Because androgen resistance develops, in part, from adaptive cell survival mechanisms activated by androgen withdrawal, we hypothesize that intermittent re-exposure to androgens may prolong time to androgen-independent progression. The objective of this study was to determine whether intermittent androgen suppression (IAS) could delay the onset of androgen-independent PSA gene regulation in LNCaP prostate tumour model when compared to CAS. Five or six cycles of IAS were possible before progression developed. IAS prolonged time to androgen-independent PSA gene regulation from an average of 26 days in CAS to 77 days in IAS. Serum PSA increased above pre-castrate levels in all mice treated with CAS by 28 days post-castration, but remained below pre-castrate levels in 75% of IAS-treated mice by 60 days post-castration. By 15 weeks post-castration, serum PSA levels increased 7-fold above pre-castrate levels in CAS-treated mice compared to 1.9-fold increase in IAS-treated mice. PSA mRNA expression levels highly correlated with serum PSA levels in both groups. Maintenance of androgen dependency through IAS may be due to androgen-induced differentiation and/or down-regulation of androgen-suppressed gene expression.
J Steroid Biochem Mol Biol 1996 May
PMID:Intermittent androgen suppression delays progression to androgen-independent regulation of prostate-specific antigen gene in the LNCaP prostate tumour model. 880 95

The conversion of testosterone (T) to dihydrotestosterone (DHT) has been demonstrated to be catalysed by at least two isoforms of human steroid 5 alpha-reductase, designated types I and II. Type II 5 alpha-reductase expression predominates in human accessory sex tissues, localized to the fibromuscular stromal compartment. The type I isoform predominates in skin, prostatic epithelia and, to a lesser extent, in prostatic fibromuscular stroma. The significance of the type I isoform to prostatic cellular growth and function remains undefined. In cultured DU145 cells, we evaluated the metabolism of [14C]-T and demonstrated the time-dependent formation of [14C]-DHT. Oxidative metabolism (conversion of [14C]-T to [14C]-androstenedione) and the formation of conjugated androgen metabolites occurred at a relatively low rate in the DU145 cells. Using human type I 5 alpha-reductase cDNA, Northern blot analysis of DU145 cell mRNA revealed high levels of type I isoform expression. Analogous probing of the DU145 cells with a human 5 alpha-reductase II cDNA failed to reveal expression of the type II isoform. The expression of functional type I activity has been confirmed pharmacologically using isoform-selective 5 alpha-reductase inhibitors. Reductive metabolism of [3H]-T in the DU145 cells was inhibited in a concentration-dependent manner by LY306089, a potent non-steroidal type I-selective inhibitor (IC50 = 10.0 nM). SKF105657, a steroidal type II-specific inhibitor was distinctly less active at inhibiting [3H]-DHT formation. LY306089 was a non-competitive inhibitor of type I 5 alpha-reductase in DU145 cellular homogenates with an apparent Ki value of 4.0 nM. These studies have identified and pharmacologically defined type I 5 alpha-reductase activity in an androgen-insensitive prostatic cancer cell line and provide the basis for additional investigations into the significance of type I 5 alpha-reductase to human prostatic pathophysiology.
J Steroid Biochem Mol Biol 1996 May
PMID:Characterization of type I 5 alpha-reductase activity in DU145 human prostatic adenocarcinoma cells. 880 1

The growth of prostate cancer is androgen responsive, and androgen receptor (AR) is thought to play an important role in the development of this cancer. Recently, some reports demonstrated that AR gene mutations were detected in human prostate cancer tissues. We have previously reported that one of eight endocrine therapy-resistant prostate cancer cases showed AR gene mutation [Suzuki et al: J Steroid Biochem Mol Biol 46:759-765, 1993]. To further investigate structural abnormality of the AR in a large number of human prostate cancers, exons B-H encoding DNA-and hormone-binding domains were examined by single-strand conformation polymorphism analysis of polymerase chain reaction products and direct sequencing. Tissues surgically removed from 30 cases of stage B or C prostate cancer and from 22 cases of endocrine therapy-resistant cancers obtained at autopsy were used in the study. Three out of 22 cancer death cases (14%) revealed AR gene mutations, one of which contained two different mutations-exon D in cancerous prostate and exon H in metastatic tissues. In the other two cases, AR gene mutations in exon H were found in metastatic tissues. All three cases in metastatic tissues showed the same mutation at codon 877 (877Thr-->Ala). In stage B or C cancer tissues and the other cancer death samples, no AR mutation was detected. The mutation in exon H was identical to that reported in a human prostate cancer cell line, LNCaP. These results indicate that AR gene mutation scarcely occurs in the early stage of prostate cancer and that the mutation is found in relation to endocrine therapy resistance. Two patients with an AR gene mutation at codon 877 revealed a remarkable fall in prostate-specific antigen after withdrawal of antiandrogen. Data on the other case were not available. These results indicate that a codon 877 mutation in the AR gene in advanced prostate cancer evokes the antiandrogen withdrawal syndrome. To our knowledge, this report is the first description of relationship between an AR mutation at codon 877 and the antiandrogen withdrawal syndrome.
 ...
PMID:Codon 877 mutation in the androgen receptor gene in advanced prostate cancer: relation to antiandrogen withdrawal syndrome. 882 83

Epidemiological data suggest that vitamin D3, obtained from dietary sources and sunlight exposure, protects against mortality from prostate cancer (PC). In agreement with this, the most active vitamin D metabolite 1 alpha,25-dihydroxyvitamin D3 [1,25(OH)2 D3] regulates the growth and differentiation of several human PC cell lines. Both genomic and non-genomic signalling pathways for 1,25(OH)2 D3 have been reported, although the mechanism of action in PC cells has not been defined. We now provide data supporting an active role for the nuclear vitamin D receptor (VDR) in mediating the growth-inhibitory effects of 1,25(OH)2 D3 on these cells. In the VDR-rich cell line ALVA-31, the observed changes in growth by 1,25(OH)2 D3 are preceded by significant changes in VDR mRNA expression. In contrast, the cell line JCA-1, containing few VDRs, fails to show both early changes in VDR gene expression and later changes in growth with 1,25(OH)2 D3. To assess the role of the VDR more directly, transfection studies were pursued. ALVA-31 cells were stably transfected with an antisense VDR cDNA construct in an attempt to reduce VDR expression. Antisense mRNA expression among clones was associated with: (a) reduced or abolished sensitivity to the effects of 1,25(OH)2 D3 on growth; (b) decreased numbers of VDRs per cell, as measured by radiolabelled-ligand binding; and (c) a lack of induction of the VDR-regulated enzyme 24-hydroxylase in response to 1,25(OH)2 D3. From these studies we conclude that the antiproliferative effects of 1,25(OH)2 D3 require expression of the nuclear VDR in this system.
J Steroid Biochem Mol Biol 1996 Jun
PMID:Vitamin D receptor expression is required for growth modulation by 1 alpha,25-dihydroxyvitamin D3 in the human prostatic carcinoma cell line ALVA-31. 883 63

Cancer of the prostate is the most frequent cancer and the second leading cause of cancer death in men in North America. The growth of Shionogi carcinoma-115 (SC-115) cells is highly sensitive to androgens, and this cell line is a well known experimental model of prostate cancer. The transplantable Shionogi carcinoma tumor was used to assess the influence of tumor size on the response to flutamide treatment. Two weeks after subcutaneous inoculation of tumor fragments in Shionogi mice, six groups of animals bearing SC-115 tumors ranging from 0.1 to 1.8 cm in diameter were treated with flutamide (1 mg, twice daily). The castrated mice received an androstenedione (delta4-dione) implant to mimic the human situation, where the adrenals produce precursor steroids which are transformed into androgens in peripheral intracrine tissues. After 16 days, treatment with flutamide inhibited tumor growth by 32 to 57% in the four groups of mice having tumors ranging from 0.1 to 1.0 cm in diameter at day 0, whereas no significant inhibitory effect was observed in larger tumors. The same treatment, however, caused potent inhibitory effects on other androgen-sensitive parameters, namely prostatic and seminal vesicle weight and kidney ornithine decarboxylase (ODC) activity, the effect on these parameters being similar in all groups of animals, irrespective of tumor size. Furthermore, when those larger tumors unresponsive to antiandrogenic treatment were cut into small fragments and inoculated into new groups of mice, the same treatment with flutamide efficiently inhibited tumor growth, treatment being started at tumor sizes of 0.1 to 0.3 cm in diameter. The present data clearly demonstrate that small tumors are highly sensitive to androgen deprivation, while loss of response develops with increasing tumor size, thus indicating that, for optimal efficacy, androgen blockade should be given at the early stages of prostate cancer.
J Steroid Biochem Mol Biol 1996 Aug
PMID:Large Shionogi tumors lose their responsiveness to flutamide treatment. 891 74

The relapse of prostate cancer during endocrine therapies is attributed to the proliferation of growth factor (GF)-dependent epithelial cells. Such cells are present but in a quiescent state in the normal adult human and dog (experimental model) prostates. GF-signaling pathways involve the activation of protein tyrosine kinases (PTK) whose action is also modulated by phosphotyrosine protein phosphatases (PTPs). To that effect, we have previously reported that dividing canine prostatic epithelial cells exhibited high levels of phosphotyrosyl-(pY)-proteins which were greatly enhanced when incubated in the presence of vanadate. The aim of this study, performed with pervanadate (pV), was to determine whether pV acts either directly by stimulating prostatic PTKs or indirectly by inhibiting PTPs. Upon fractionation, most of the PTK activity was found in membranes of dividing cells and pV selectively increased its activity. This was due to an inhibition of intrinsic PTPs, as demonstrated by dephosphorylation of endogenous pY-proteins which was abolished by pV. This activity was very sensitive to pV (IC50: 150 nM) and was due to non-secreted forms of prostatic acid phosphatase (PAP), a pV inhibited-enzyme, as well as to PTP-1 B, as demonstrated by gel filtration, isoelectric focusing and probing with antibodies. These enzymes were also detected in membranes from human hyperplastic/neoplastic prostates but only PTP-1 B was present in those of prostatic carcinoma PC3 cells. These PTPs, bound to membranes of dividing cells (normal vs neoplastic) where activated PTKs are also located, may be of importance in the development and progression of prostatic proliferative diseases.
Mol Cell Biochem
PMID:The enhancement by pervanadate of tyrosine phosphorylation on prostatic proteins occurs through the inhibition of membrane-associated tyrosine phosphatases. 892 29

To correlate molecular changes with clinical information in prostate tissue, it is necessary to have accurate methods for screening for mutations in clinically available specimens. We have refined the polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) analysis for detection of p53 mutations in routine pathology specimens. These improvements help overcome technical barriers that interfere with SSCP analysis of archival tissues when only small amounts of poorly preserved formalin-fixed DNA are available. Furthermore, prostate samples are heterogeneous in containing tumor, normal tissue, and hyperplastic tissue. To address the first issue, the method included an initial selection of PCR products using exonuclease I, followed by a second-step selection using nested PCR. This step ensures adequate amplification of the target sequence while minimizing artifactual products that could otherwise interfere with mutation analysis. For the second issue, in addition to morphologic selection of appropriate tissue areas, we improved the sensitivity of detection of mutations by using restriction enzyme digestion of products prior to SSCP analysis. Detection of mutations in heterogeneous tissue was evaluated by determining the minimal detectable mutant allele frequencies in exons 4, 5, 6, 7, 8-9, and 10 by using mixtures of known mutant and wild-type cell lines, which were found to be 17.6, 9.1, 12.5, 8.1 14.0, and 14.3%, respectively. To determine the utility of this method when used on heterogeneous clinical samples, we performed study of 19 archival prostate specimens (14 primary prostate cancers, three benign prostatic hyperplasia and two metastases) and detected abnormally migrating products in six of the prostate cancer specimens (four primaries and two metastases). In five of these samples, there was sufficient DNA to perform sequencing, which disclosed single-base change mutations in all five samples.
Diagn Mol Pathol 1996 Dec
PMID:Identification of p53 mutations in archival prostate tumors. Sensitivity of an optimized single-strand conformational polymorphism (SSCP) assay. 895 19


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