Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.1.27.1 (RNase)
16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Serum RNase (ribonuclease) of normal persons and of patients with pancreatitis, carcinoma of pancreas, or other neoplasms was determined with poly(C) as substrate. Strikingly abnormal elevations occur in the serum RNase of patients with pancreatic cancer. There is no elevation in the serum RNase level of patients with pancreatitis. Average serum RNase values of 52 normal persons, 10 patients with pancreatitis, 30 patients with pancreatic cancer, 28 patients with breast cancer, 11 patients with lung cancer, 20 patients with colon cancer, six patients with stomach cancer, and four patients with liver cancer, respectively, were 104, 120, 383, 131, 173, 197, 194, and 152 units/ml of serum. Ninety percent of the patients with pancreatic cancer were above the level of 250 units of serum and 90% of all patients with varied cancers were below this level. In the presence of severe renal insufficiency, marked elevation of serum RNase was also observed. Serum RNase, because of its unique specificity, pancreatic origin, and its abnormal elevation in sera of patients with pancreatic cancer, serves as a reliable biochemical marker of carcinoma of the pancreas in the presence of normal renal function.
...
PMID:Elevated serum ribonuclease in patients with pancreatic cancer. 106 80

A mitoxantrone-resistant human MCF-7 breast cancer subline (MCF/MX) which is approximately 4000-fold resistant to mitoxantrone was isolated by serial passage of the parental wild-type MCF-7 cells (MCF/WT) in stepwise increasing concentrations of drug. MCF/MX cells were also approximately 10-fold cross-resistant to doxorubicin and etoposide but were not cross-resistant to vinblastine. Intracellular accumulation of radiolabeled mitoxantrone was markedly reduced in MCF/MX cells relative to that in the drug-sensitive MCF/WT cells. This decrease in intracellular drug accumulation into MCF/MX cells was associated with enhanced drug efflux, which was reversed when cells were incubated in the presence of sodium azide and 2, 4-dinitrophenol, suggesting an energy-dependent process. Incubation of MCF/MX cells with verapamil did not affect either the accumulation of mitoxantrone or the level of resistance in these cells. Furthermore, RNase protection and Western blot analyses failed to detect the expression of the mdr1 RNA or P-glycoprotein, a drug efflux pump known to be associated with the development of multidrug resistance in vitro. However, a polyclonal antibody directed against a synthetic peptide corresponding to the putative ATP binding domain of P-glycoprotein reacted with two (M(r) 42,000 and 85,000) membrane proteins from MCF/MX cells which were not found in MCF/WT. Functional assays and Western blot analysis for topoisomerase II revealed no differences in topoisomerase II activity or protein levels in MCF/MX cells. Thus, resistance in this cell line is apparently associated with enhanced drug efflux involving a pathway distinct from the mdr1-encoded multidrug transporter P-glycoprotein.
...
PMID:Reduced intracellular drug accumulation in the absence of P-glycoprotein (mdr1) overexpression in mitoxantrone-resistant human MCF-7 breast cancer cells. 135 31

In human breast carcinoma MCF-7 cells, phorbol diesters inhibit proliferation and induce cell maturation. We investigated the involvement of TGF-beta 1 in the PCK-mediated inhibition of breast cancer cell proliferation. Using an RNase protection assay, we showed that TPA induced a dose-dependent increase in levels of TGF-beta 1 mRNA that paralleled the inhibitory effect on MCF-7 proliferation. Similar results were obtained with another TPA-sensitive breast cancer cell line (BT-20). TPA did not increase TGF-beta 1 mRNA levels in the MCF-7:RPh-4 and T47D cell lines, which are both insensitive to the growth inhibitory effects of phorbol esters. In addition, the increase in TGF-beta 1 mRNA level was not observed after treatment of the MCF-7 cell with other inducers of cell differentiation such as forskolin, DMF, HMBA and sodium butyrate. The induction of TGF-beta 1 mRNA by TPA along with its inhibitory effect on cell proliferation suggests that TGF-beta 1 mediates, at least in part, the inhibitory effect of PKC activation.
...
PMID:[Regulation by protein kinase C of TGF-beta 1 expression in cultured cells of breast adenocarcinoma]. 142 93

Human selenium-dependent glutathione peroxidase (hGPx1) (EC 1.11.1.9) is thought to be involved in many critical cellular functions as a result of its role in glutathione-mediated reduction of toxic peroxides, and it is implicated as a mechanism of resistance against oxygen free radicals. Previous studies have demonstrated that the gene encoding hGPx1 (hgpx1) is more highly expressed in multidrug-resistant AdrR MCF-7 human breast cancer cells than in the parental WT MCF-7 cell line. In order to further study the transcriptional regulation of hgpx1, we have cloned the genomic hgpx1 gene and determined its nucleotide sequence. The 2550-base pair (bp) 5'-flanking sequence of hgpx1 contained the terminal 511 bp of the 3' end of a previously reported rhoH12 cDNA (Yeramian, P., Chardin, P., Madaule, P., and Tavitian, A. (1987) Nucleic Acids Res. 15, 1989), a ras-related oncogene. Further downstream from rhoH12, but before the start of transcription of hgpx1, RNase protection analysis revealed a transcribed sequence of at least 270 bp which we have called mid. RNA transcripts homologous to both rhoH12 (1.8 and 1.5 kilobase pairs (kb)) and mid (1.8 kb) are also more highly expressed in AdrR MCF-7 cells than in WT MCF-7 cells. We screened an AdrR MCF-7 cDNA library with the mid sequence and isolated a partial cDNA clone which contains both mid and rhoH12 sequences and is colinear with the genomic sequence which extends from 10 bp 3' to the rhoH12 stop codon to 810 bp 5' to the start of transcription of hgpx1. The start of transcription of hgpx1 in AdrR MCF-7 cells was determined by primer extension analysis. The promoter and 2 kb of the 5'-flanking sequence of hgpx1 was fused to the bacterial chloramphenicol acetyltransferase gene (hGPx1-CAT1). Analysis of deletion constructs of hGPx1-CAT1 revealed three possible cis-acting regulatory regions. The transcriptional regulation of hgpx1 was examined using the hGPx1-CAT hybrid genes and nuclear run-on studies. We found no evidence that increased mRNA transcript formation could account for different levels of hgpx1 RNA either in different breast cancer cell lines or in response to selenium.
...
PMID:Structure and function of the 5'-flanking sequence of the human cytosolic selenium-dependent glutathione peroxidase gene (hgpx1). 155 8

The insulin-like growth factors IGF-I and IGF-II are potent mitogens for several breast tumor cell lines in culture. Additionally, both IGF-I and IGF-II mRNAs are easily detected in the majority of breast tumor specimens examined, while no breast cancer epithelial cell lines we have studied express authentic IGF-I mRNA, and few lines express IGF-II mRNA. Although receptors for insulin, IGF-I, and IGF-II have been described, there is significant cross-reactivity between the various receptors and ligands in the insulin/insulin-like growth factor family, and it is not clear which receptor or receptors are responsible for the biological effects of these growth factors in this system. Using an RNase protection assay, we examined breast tumor specimens and breast cancer epithelial cell lines for expression of mRNA encoding the type I and type II IGF receptors as well as the insulin receptor. Virtually all of the specimens examined expressed mRNA for all three receptors. We then examined estrogen-dependent MCF-7 cells for the mitogenic effects of IGF-I and II in the presence of antibodies to both the type I and type II receptors. alpha IR-3, a monoclonal antibody which blocks the type I receptor, abolished the mitogenic effects of both IGF-I and IGF-II. It did not, however, block the mitogenic effects of insulin. We conclude that type I and type II IGF receptors are ubiquitously expressed in breast cancer, and our experiments with MCF-7 cells suggest the mitogenic effects of both IGF-I and IGF-II are mediated via the type I IGF receptor.
...
PMID:Insulin-like growth factor receptor expression and function in human breast cancer. 215 73

The p53 gene initially was thought to be an oncogene, but recent evidence suggests that wild-type p53 can function as a tumor suppressor gene in lung, colon, and breast cancer as well as less common malignancies. This study reports the first identification of intronic point mutations as a mechanism for inactivation of the p53 tumor suppressor gene. Abnormally sized p53 mRNAs found in a small cell and a non-small cell lung cancer cell line were characterized by sequence analysis of cDNA/PCR products, the RNase protection assay and immunoprecipitation. These mRNAs were found to represent aberrant splicing leading to the production of abnormal or no p53 protein. Sequence analysis of genomic DNA revealed that a point mutation at the splice acceptor site in the third intron or the splice donor site in the seventh intron accounts for the abnormal mRNA splicing. In one patient the same intronic point mutation was found in the tumor cell line derived from a bone marrow metastasis and in multiple liver metastases but not in normal DNA, indicating that it occurred as a somatic event before the development of these metastases. These findings further support the role of inactivation of the p53 gene in the pathogenesis of lung cancer and indicate the role of intronic point mutation in this process.
...
PMID:Identification of intronic point mutations as an alternative mechanism for p53 inactivation in lung cancer. 216 47

The IGFs may be important autocrine, paracrine or endocrine growth factors for human breast cancer. IGF-I and II stimulate growth of cultured human breast cancer cells. IGF-I is slightly more potent, paralleling its higher affinity for the IGF-I receptor. Antibody blockade of the IGF-I receptor inhibits growth stimulation induced by both IGFs, suggesting that this receptor mediates the growth effects of both peptides. However, IGF-I receptor blockade does not inhibit estrogen (E2)-induced growth suggesting that secreted IGFs are not the major mediators of E2 action. Several breast cancer cell lines express IGF-II mRNA by both Northern analysis and RNase protection assay. IGF-II activity is found in conditioned medium by radioimmuno and radioreceptor assay, after removal of somatomedin binding proteins (BP) which are secreted in abundance. IGF-I is undetectable. BPs of congruent to 25 and 40 K predominate in ER-negative cell lines while BPs of 36 K predominate in ER-positive cells. Blockade of the IGF-I receptor inhibits anchorage-independent and monolayer growth in serum of a panel of breast cancer cell lines. Growth of one line (MDA-231) was also inhibited in vivo by receptor antibody treatment of nude mice. The antibody had no effect on growth of MCF-7 tumors. These data suggest that IGFs are important regulators of breast cancer cell proliferation and that antagonism of this pathway may offer a new treatment strategy.
...
PMID:Regulation of breast cancer growth by insulin-like growth factors. 217 63

Transforming growth factor (TGF)-beta is a potent regulator of many cell functions and a growth inhibitor for mammary epithelial cells. We now know of three highly homologous members of the human TGF-beta gene family. We have studied the expression of TGF-beta 1, -beta 2, and -beta 3 mRNA in four human breast cancer cell lines. Using the RNase protection assay, we have detected mRNA expression of TGF-beta 1, -beta 2, and -beta 3 by T-47D cells, TGF-beta 1 and -beta 3 by ZR-75-1 cells, and TGF-beta 1 by MCF-7 cells. Treatment of these estrogen receptor-positive cells with 10 nM estradiol for 48 h resulted in decreased mRNA levels of TGF-beta 2 and -beta 3 but did not affect mRNA levels of TGF-beta 1. Expression of TGF-beta 1 and -beta 2 mRNA by an estrogen receptor-negative cell line, MDA-MB-231, was not changed by estradiol treatment. Treatment of cells with the antiestrogen tamoxifen (1 microM) did not significantly alter mRNA levels for any of the three TGF-beta species. We have further determined that estradiol treatment of T-47D was associated with diminished secretion of TGF-beta into the medium. Both TGF-beta 1 and -beta 2 inhibited the proliferation of MCF-7 cells, and neither protein affected the growth of T-47D cells. TGF-beta 1 was at least 10-fold more potent than TGF-beta 2 at inhibiting the growth of MCF-7 cells.
...
PMID:Differential regulation of expression of three transforming growth factor beta species in human breast cancer cell lines by estradiol. 229 70

Drug resistance occurs frequently during breast cancer treatment with antiestrogens. Since antiestrogen action is mediated by the estrogen receptor (ER), we have examined both the structural and functional properties of the ER present in two breast cancer cell lines, LY2 and T47D, which proliferate rapidly in the presence of antiestrogens. The ER function in LY2 cells was indistinguishable from that of the parental tamoxifen-sensitive MCF-7 cells as assessed by estrogen regulation of two endogenous genes and estrogen-regulated transcription in a transient transfection system. RNase protection assays, sensitive enough to detect single base pair mismatches, showed that the sequence of the coding region of ER of LY2 and T47D cells was wild type. Thus the ER appears to be normal in two independently isolated breast cancer cell lines whose growth is resistant to the inhibitory effect of antiestrogens. Moreover by conducting the cell proliferation studies in a phenol red-free medium, we have demonstrated that the antiestrogen resistance of LY2 and T47D cells corresponds in fact to an estrogen-independent growth.
...
PMID:Characterization of the estrogen receptor in two antiestrogen-resistant cell lines, LY2 and T47D. 229 73

Insulin-like growth factor-II (IGF-II) is a potent mitogen for several types of cultured cells and tissues. We have studied the interaction of IGF-II with a panel of cultured human breast cancer cell lines, examining the possibility that these cells synthesize and secrete IGF-II activity which could have autocrine/paracrine functions. Synthetic IGF-II was mitogenic in five of seven cell lines tested, including the estrogen receptor-positive lines MCF-7L, ZR75-1, and T47D and the estrogen receptor (ER)-negative lines Hs578T and MDA-231. IGF-II was slightly less potent than IGF-I in stimulating DNA synthesis in MCF-71 cells, an effect that paralleled its ability to compete for [125I]IGF-I binding in these cells. Affinity labeling studies revealed that IGF-II could also compete for binding to the 130,000 mol wt alpha-subunit of the IGF-I receptor. A monoclonal antibody to the IGF-I receptor inhibited the mitogenic effects of IGF-II in MCF-7L and MDA-231 cells, suggesting that this receptor mediates the growth effects of IGF-II in these breast cancer cells. Using a RIA and a RRA, IGF-II-like activity was detected in conditioned medium extracts processed to remove IGF-binding proteins from several breast cancer cell lines, with the highest levels found in conditioned medium from MCF-7L and T47D cell lines. IGF-II mRNA transcripts in MCF-7L and T47D cells were identified by Northern blot analysis and were confirmed by RNase protection assay. IGF-II mRNA was increased by estrogen in MCF-7L cells.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Insulin-like growth factor-II (IGF-II): a potential autocrine/paracrine growth factor for human breast cancer acting via the IGF-I receptor. 255 2


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

---