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

Previous studies suggested that GnRH gene transcripts in human tissues may be derived from an upstream transcriptional start site in addition to the well characterized hypothalamic start site. To resolve this issue we characterized the transcriptional start sites of the human GnRH gene in a human placental tumor cell line (JEG) and a human breast tumor cell line (MDA). Using primer extension and reverse transcription-polymerase chain reaction (RT-PCR) assay, we identified a discrete upstream transcriptional start site 579 bases up-stream from the hypothalamic site in both JEG and MDA cell lines. The up-stream start site lacks the TATA and CAAT elements often present in RNA polymerase-II promoters, but contains the sequence GGTCTTGCT located 84 bases 5' to the up-stream start site similar to other genes that lack TATA/CAAT boxes. RT-PCR quantitation shows that the up-stream start site is the major transcriptional start site, representing 74% of the cytoplasmic transcripts in JEG cells and 67% in MDA cells. Supporting this observation, transfection assay using a human GnRH promoter/luciferase reporter gene construct containing only the up-stream transcription start site has a higher level of transcriptional activity than the human GnRH promoter/luciferase reporter construct containing only the down-stream start site. A high relative abundance (approximately 45%) of total GnRH mRNAs were also found in the nucleus of both cell lines, which did not appear to be a consequence of the nuclear/cytoplasmic fractionation procedure. To determine if this upstream start site was used in normal GnRH-expressing human tissues, we analyzed RNA from a variety of postmortem/surgical procedure tissue samples. RT-PCR analysis together with Southern blot analysis demonstrated the presence of GnRH mRNA in human pituitary, cerebral cortex, testes, ovary, and mammary gland for the first time as well as verified GnRH gene expression in hypothalamus and placenta. The up-stream transcriptional start site is used only in reproductive tissues, such as placenta, testes, ovary, and mammary gland, suggesting tissue-specific regulation at this site.
Mol Endocrinol 1993 Dec
PMID:Identification of a major up-stream transcription start site for the human progonadotropin-releasing hormone gene used in reproductive tissues and cell lines. 814 71

MCF-7 cells transfected with human prepro-IGF-II cDNA secreted two large precursor forms of 22 and 15 kDa, with trace amounts of the mature 7 kDa IGF-II, suggesting that overexpression leads to saturation of processing and the secretion of precursors. The 15 kDa form was separated from 22 and 7 kDa IGF-II by cation-exchange chromatography. Intracellular IGF-II, detectable only in detergent buffers, existed in two forms of 24 and 22 kDa. Conditioned media from four other breast cancer cell lines (MDA-231, HBL-100, T47D and MCF-7 McG), all contained mature 7 kDa IGF-II with trace amounts (< 10%) of the 15 kDa IGF-II. Oestradiol induced IGF-II secretion in oestrogen-sensitive MCF-7 and T47D cells, but secretion was constitutively higher in oestrogen-unresponsive MDA-231 and HBL-100 cells. This indicates, for the first time, that oestrogen regulation of IGF-II peptide in breast cancer cells, and expression throughout all cell lines tested, would support the hypothesis that IGF-II has an autocrine regulatory function in breast cancer.
Mol Cell Endocrinol 1994 Mar
PMID:Processing of insulin-like growth factor-II (IGF-II) by human breast cancer cells. 820 29

The antiestrogen tamoxifen [(Z)-1(p-beta-dimethylamino-ethoxyphenyl)-1,2- diphenylbut-1-ene] is an effective anticancer agent for the treatment of hormone responsive breast cancer. Previous studies have demonstrated that a point mutation in the estrogen receptor (ER) resulted in an alteration of the pharmacology of 4-hydroxytamoxifen, the active metabolite of tamoxifen (Jiang et al, Mol Endocrinol 6:2167-2174, 1992). We have extended our studies to evaluate the effect of a point mutation, a Val substitution for Gly at amino acid 400 in the ligand binding domain of ER, on the pharmacology of other antiestrogens in ER stable transfectants derived from the ER-negative breast cancer cell line MDA-MB-231 CL10A. The compounds were tested with or without estradiol-17 beta (E2) for their effects on cell growth in cells expressing the wild type ER (S30) or the mutant ER (ML alpha 2H) or in control antisense ER transfectant AS23 which does not express ER protein. MCF-7 cells, which express the wild type ER, were also used as a control. The growth of AS23 cells was not affected by any of the compounds at a concentration of 1 microM. E2 stimulated the growth of MCF-7 cells but inhibited the growth of ER transfectants S30 and ML alpha 2H. The ML alpha 2H cells were about 10 to 100-fold less sensitive to E2 and antiestrogens than S30 and MCF-7 cells. Keoxifene, an antiestrogen with a high affinity for the ER, maintained antiestrogenic activities in both ER transfectants and MCF-7 cells.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:A model to describe how a point mutation of the estrogen receptor alters the structure-function relationship of antiestrogens. 821 51

In the model of transient brain ischemia of 6-min duration in gerbils we have estimated: 1. The concentration of brain gangliosides: A significant decrease to about 70% of control was observed selectively in the hippocampus at 3 and 7 d after ischemia. 2. The activity of Na+,K(+)-ATPase: The enzyme activity was not affected in either hippocampus nor in cerebral cortex. 3. The malonaldehyde (MDA) concentration: The levels of MDA had increased at 30 min after ischemia up to 123 and 129% of control in hippocampus and cerebral cortex, respectively. 4. Immunoreactivity of protein kinase C detected by Western blotting: In hippocampus the early translocation toward membranes was followed by a decrease in total enzyme content at 6, 24, 72, and 96 h of postischemic recovery. Also, a sharp increase of 50 kDa isoform (PKM) was noticed immediately and at the early recovery times. The behavior of these biochemical markers of ischemic brain injury in the hippocampus after the short (6 min) insult was contrasted with their reaction in the cerebral cortex as well as after prolongation of the ischemia to 15 min. These results taken together indicate that an early increase in PKC translocation followed by a decrease is the most symptomatic for selective, delayed, postischemic hippocampal injury, resulting from short duration (6 min) ischemia of the gerbil brain.
Mol Chem Neuropathol 1993 Oct
PMID:Protein kinase C as an early and sensitive marker of ischemia-induced progressive neuronal damage in gerbil hippocampus. 829 17

Expression of matrix Gla protein (MGP) gene and its regulation by retinoic acid (RA) and estrogen was investigated in eight human breast cancer cell lines. The promoter region of the MGP gene contains a consensus retinoic acid response element (RARE) and the MGP gene expression has been shown to be strongly induced by RA in other systems. Our results suggest that RA negatively regulates MGP mRNA expression in human breast cancer cells that have high levels of estrogen receptors (ER), i.e. MCF-7, ZR-75 and BT474 and positively regulates its expression in cells with either no ERs, i.e. MDA-MB-468 or very low levels of ERs, i.e. T47D. This indicates that ER levels may affect RA modulation of MGP gene expression in human breast cancer cells. The inhibitory effect of RA on MGP gene expression was abolished in RRO-I, the RA-resistant MCF-7 subline. We also demonstrate for the first time that estrogen strongly induces MGP gene expression in ER-positive cells and that estrogen-mediated induction of MGP is blocked by RA even in otherwise RA-resistant cells.
Mol Cell Endocrinol 1993 Apr
PMID:Differential regulation of matrix Gla protein (MGP) gene expression by retinoic acid and estrogen in human breast carcinoma cells. 831 25

In the present studies the action of Danazol on the conversion of estrone sulfate (E1S) to estradiol (E2) as well as on the sulfatase activity in the MCF-7 and T-47D, hormone-dependent, and MDA-MB-231, hormone-independent, mammary cancer cell lines was explored. Using intact cells we observed that Danazol blocks very significantly the radioactivity uptake and the conversion of [3H]E1S to E2 in all the cells studied. In particular, a very strong effect (85% decrease of these parameters versus the control values) is observed in the T-47D cells. In another series of studies using cell homogenates it is observed that Danazol inhibits the sulfatase activity in all these cell lines. The effect of Danazol is dose-dependent and significant from a concentration of 1 microM. At concentrations of 8 microM E1S, 10(-5) M Danazol, the inhibition of sulfatase activity is 38% in MCF-7, 36% in MDA-MB-231, and 27% in T-47D cells. Analysis by Lineweaver-Burk plot shows that the inhibitory effect is competitive. As E1S is one of the main sources of E2 in human mammary tumors, the present data could open new possibilities for therapeutic applications in hormone-dependent breast cancer.
J Steroid Biochem Mol Biol 1993 Jul
PMID:Action of danazol on the conversion of estrone sulfate to estradiol and on the sulfatase activity in the MCF-7, T-47D and MDA-MB-231 human mammary cancer cells. 833 87

The retinoid X receptor beta (RXR beta; H-2RIIBP) forms heterodimers with various nuclear hormone receptors and binds multiple hormone response elements, including the estrogen response element (ERE). In this report, we show that endogenous RXR beta contributes to ERE binding activity in nuclear extracts of the human breast cancer cell line MCF-7. To define a possible regulatory role of RXR beta regarding estrogen-responsive transcription in breast cancer cells, RXR beta and a reporter gene driven by the vitellogenin A2 ERE were transfected into estrogen-treated MCF-7 cells. RXR beta inhibited ERE-driven reporter activity in a dose-dependent and element-specific fashion. This inhibition occurred in the absence of the RXR ligand 9-cis retinoic acid. The RXR beta-induced inhibition was specific for estrogen receptor (ER)-mediated ERE activation because inhibition was observed in ER-negative MDA-MB-231 cells only following transfection of the estrogen-activated ER. No inhibition of the basal reporter activity was observed. The inhibition was not caused by simple competition of RXR beta with the ER for ERE binding, since deletion mutants retaining DNA binding activity but lacking the N-terminal or C-terminal domain failed to inhibit reporter activity. In addition, cross-linking studies indicated the presence of an auxiliary nuclear factor present in MCF-7 cells that contributed to RXR beta binding of the ERE. Studies using known heterodimerization partners of RXR beta confirmed that RXR beta/triiodothyronine receptor alpha heterodimers avidly bind the ERE but revealed the existence of another triiodothyronine-independent pathway of ERE inhibition. These results indicate that estrogen-responsive genes may be negatively regulated by RXR beta through two distinct pathways.
Mol Cell Biol 1993 Apr
PMID:Inhibition of estrogen-responsive gene activation by the retinoid X receptor beta: evidence for multiple inhibitory pathways. 838 7

Retinoic acid (RA) strongly inhibits proliferation of the estrogen (E2)-dependent human breast cancer cell lines MCF7, T47D, and ZR75-1, but not the E2-independent and E2 receptor (ER)-negative lines MDA-MB231, MDA-MB468, BT20 and Hs578T. The specific sensitivity of the E2-dependent cell lines seems not to be caused by an inhibitory effect of RA on ER functioning since RA inhibited the proliferative response not only to E2 but also to insulin. Furthermore, endogenous RA receptors (RARs) hardly impaired transcriptional activation of an E2 responsive element-tk-CAT reporter construct. RAR alpha mRNA was highly expressed in the RA-responsive lines, but not in the unresponsive lines, except BT20. With the exception of Hs578T, also RAR beta mRNA expression was low in the unresponsive lines. While in the dependent lines and Hs578T RA activated RA responsive element-dependent transcriptional activity, this response was very low in MDA-MB231, MDA-MB468, and BT20, suggesting that the RA resistance of these latter three ER-negative lines is due to underexpression of functional RARs. Our results suggest that the loss of functional RARs may be a frequent event, leading to RA unresponsiveness of ER-negative breast cancer cells. This implies that both the steroid and retinoid receptor status of breast tumors may be used to predict a successful treatment with retinoids.
Mol Cell Endocrinol 1993 Feb
PMID:Retinoic acid resistance of estradiol-independent breast cancer cells coincides with diminished retinoic acid receptor function. 838 11

MDA-modified casein, lysozyme or polylysine (MC, ML and MP respectively), was intradermically injected to rabbits in the presence of complete Freund's adjuvant (cFA). Two other animal sets received either cFA alone, or MDA alone. MDA, cFA and MP did not induce any antibody response. Both ML and MC produced an increase of antibody reactivity towards ML, but reactivity towards native lysozyme (L) was increased only by ML and not by MC. According to these results, it was concluded that the epitopes recognized by antibodies reacting with ML and not with L are AIP bridges and possibly the two surrounding aminoacyl (especially lysyl) residues.
Biochem Mol Biol Int 1993 Jan
PMID:Immunization of rabbits with proteins reacted with malonic dialdehyde (MDA): kinetics and specificity of the immune response. 849 May 60

The effect of acute ethanol intake on lipid peroxidation (LP) and proteins in red blood cells (RBC) was explored. The amount of malondialdehyde (MDA; an indicator of LP) was elevated transiently when the maximal ethanol level in whole blood was observed. In contrast, erythrocyte membrane proteins were not affected. In in vitro experiments both ethanol and acetaldehyde did not alter the MDA levels. These results indicate that the metabolism of ethanol or acetaldehyde beyond the RBCs is required in order to detect LP on these cells.
Biochem Mol Biol Int 1993 Feb
PMID:Acute ethanol intake produces lipid peroxidation in rat red blood cells membranes. 849 11


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>