Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.30.2 (endonuclease)
 18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Androgen-dependent normal prostatic glandular cells and androgen-dependent prostatic cancer cells can be induced to undergo cell death after androgen ablation. This death does not require the cells to proliferate and occurs as an energy-dependent process collectively referred to as "programmed cell death" in which the cells actively commit "suicide." Associated with this programmed cell death pathway is the enhanced expression of a series of genes and the fragmentation of the genomic DNA into nucleosomal oligomers. This genomic DNA fragmentation is the irreversible commitment step in the death of the cell and results from activation of Ca2+/Mg(2+)-dependent endonuclease activity within the cell nucleus. This activation is due to sustained elevation of intracellular free Ca2+ (Cai) induced after androgen ablation. Metastatic prostatic cancer within an individual patient is heterogeneous, including both androgen-dependent and -independent cancer cells. Thus, androgen ablation is rarely curative since it only induces the programmed death of the androgen-dependent cancer cells without activating this pathway in the androgen-independent cancer cells within the patient. Androgen-independent prostatic cancer cells do not activate this death process after androgen ablation, since this does not induce a sustained increase in Cai. A new approach to treat androgen-independent prostatic cancer cells has focused on the use of chemotherapeutic agents to induce a sustained increase in Cai. These studies demonstrate that if such a sustained elevation in Cai is maintained, even androgen-independent prostatic cancer cells undergo programmed cell death.
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PMID:Androgen regulation of programmed death of normal and malignant prostatic cells. 129 27

Androgen ablation induces an energy-dependent process of programmed death in nonproliferating androgen-dependent prostatic cancer cells which involves fragmentation of genomic DNA into nucleosomal oligomers catalyzed by nuclear Ca2+, Mg(2+)-dependent endonuclease enzymes activated following a sustained elevation in intracellular free Ca2+ (Cai). In contrast, androgen-independent prostatic cancer cells are not induced to undergo such programmed cell death by androgen ablation. One explanation for the inability of androgen ablation to induce programmed death of androgen-independent prostatic cancer cells is that such ablation does not result in a sustained elevation in Cai in these cells. This raises the issue of whether androgen-independent prostatic cancer cells can be induced to undergo programmed death if an elevation in the Cai is sufficiently sustained by nonhormonal means. To test this possibility, androgen-independent, highly metastatic Dunning R-3327 AT-3 rat prostatic cancer cells were chronically exposed in vitro to the calcium ionophore ionomycin to sustain an elevation in their Cai. These studies demonstrated that an elevation of Cai as small as only 3-6-fold above baseline can induce the death of these cells if sustained for greater than 12 h. Temporal analysis demonstrated that the death of these cells does not require cell proliferation and involves Ca(2+)-induced fragmentation of genomic DNA into nucleosome-sized pieces as the commitment step in this process. These results demonstrate that even nonproliferating androgen-independent prostatic cancer cells can be induced to undergo programmed cell death if a modest elevation in the Cai is sustained for a sufficient time. These observations identify Cai as a potential target for therapy for androgen-independent prostatic cancer cells.
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PMID:Programmed death of nonproliferating androgen-independent prostatic cancer cells. 187 14

Apoptosis in the androgen-sensitive Dunning R3327 PAP prostatic adenocarcinoma was studied during the post castration period of 14 days and compared with the ventral prostate. The mRNA expression of testosterone repressed prostatic message-2 and tissue-type plasminogen activator in the Dunning tumor and in the ventral prostate was analyzed by Northern blot experiments and immunohistochemical procedures. The degree of endonuclease-degraded genomic DNA was examined by gel electrophoresis. Apoptotic tumor epithelial cells were identified with in situ end labeling. Epithelial cells incorporating bromodeoxyuridine (BrdUrd) after castration in the ventral prostate and the Dunning tumors were localized with immunostaining. Androgen ablation resulted in an induction of testosterone repressed prostatic message-2 and tissue-type plasminogen activator transcripts in the normal prostate with a peak at approximately 2 to 5 days post castration. These transcript levels in the Dunning prostatic tumors did not show any induction during the same period. Immunohistochemical staining for sulfated glycoprotein-2 and tissue-type plasminogen activator confirmed this difference between the tumor tissue and the ventral prostate at the transcriptional level. The determination of DNA integrity showed similar results in that the degree of DNA fragmentation in the tumor was much lower than the initial and marked degradation of DNA in the ventral prostate. The number of in situ end-labeled epithelial tumor cells were not increased by castration. BrdUrd immunodetection showed that castration induced an initial increase in the number of BrdUrd-positive epithelial cells in the ventral prostate. In the tumors, castration resulted in a decrease in BrdUrd-positive epithelial cells. It was concluded that in the androgen-sensitive prostatic Dunning R3327 PAP adenocarcinoma, the biochemical cascade leading to apoptosis is not activated by androgen withdrawal, as in the ventral prostate.
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PMID:Castration induces apoptosis in the ventral prostate but not in an androgen-sensitive prostatic adenocarcinoma in the rat. 801 87

Androgen receptor (AR) plays a key role in cell growth both in the normal prostate and in prostate cancer. Androgen ablation and prolonged antiandrogen therapy can give rise to AR-dependent prostate tumors, which nonetheless can grow in the androgen-deprived milieu. Here we describe the ribozyme approach to selectively degrading the AR mRNA and thereby inhibiting AR function. A trans-acting hammerhead ribozyme was designed to cleave the rat AR mRNA at the position +1827/ 1828, a region predicted to be minimally involved in generating stable secondary structures. Using AR mRNA fragments as substrates, it was established that this ribozyme can specifically cleave the RNA target in a sequence-specific manner. Kinetic experiments determined a Km for the substrate of 77 nM and a kcat/Km value of 1.8 x 10(7) M(-1) x min(-1), suggesting a catalytic efficiency similar to that of protein enzymes such as the relatively nonspecific ribonuclease A and a sequence-specific endonuclease EcoRI. Transient cotransfections of prostate-derived PC3 cells with three plasmids, an AR-inducible chloramphenicol acetyltransferase (CAT) reporter, an AR expression vector, and a ribozyme expression vector, showed that the ribozyme was capable of reducing the functional activity of AR. At an equimolar ratio of the AR expression plasmid to ribozyme expression plasmid, androgen-inducible CAT activity was inhibited 70%. Similar extents of inhibition were also observed at the cellular mRNA level using ribonuclease protection assays, indicating that the ribozyme functioned as an AR mRNA cleaving enzyme in cellulo. Immunocytochemical examination revealed a decline of AR immunoreactivity in ribozyme-transfected cells. In addition, no morphologically detectable cellular abnormalities were associated with ribozyme expression, indicating the absence of deleterious side effects. These results offer a new avenue for the control of AR function and cell growth, especially in the case of androgen-resistant, but AR-dependent, prostate cancer cells.
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PMID:Catalytic cleavage of the androgen receptor messenger RNA and functional inhibition of androgen receptor activity by a hammerhead ribozyme. 977 79