Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0006142 (breast cancer)
 160,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A novel gene therapy strategy is the use of suicide genes that transfer a drug sensitivity to cancer cells. We present preliminary in vitro efficacy data and in vivo toxicity data using the herpes simplex thymidine kinase (HStk) gene for breast cancer. The long-term objective of this project is to develop novel approaches for the treatment of breast cancer using in vivo retroviral gene transfer. Intraductal breast cancer cell line HTB126 transduced by an HStk retroviral vector is efficiently inhibited in vitro after GCV exposure. Further analysis revealed a bystander effect through which nontransduced HTB126 cells were also inhibited by GCV when cocultured with HStk-transduced HTB126 cells. In cell mixture experiments if only 1% of the cells in culture contained the HStk gene, 83% of the culture could be destroyed. Next safety studies were performed. Vector producer cells (VPC) were implanted into the mammary fat pads of athymic nude mice. The mice were then treated with GCV and monitored for regression of the VPC. The injected VPC regressed rapidly in response to the GCV therapy and produced no evidence of local or systemic toxicity in the animals. These in vitro efficacy data and in vivo toxicity studies lend support to the further development of an in vivo therapy model to treat breast cancer.
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PMID:Preliminary in vitro efficacy and toxicities studies of the herpes simplex thymidine kinase gene system for the treatment of breast cancer. 759 Jul 71

The lactoferrin gene is highly expressed in many different tissues, and its expression is controlled by different regulators. In this report, we have defined a retinoic acid response element (RARE) in the 5'-flanking region of the lactoferrin gene promoter. The lactoferrin-RARE is composed of two AGGTCA-like motifs arranged as a direct repeat with 1-bp spacing (DR-1). A gel retardation assay demonstrated that it bound strongly with retinoid X receptor (RXR) homodimers and RXR-retinoic acid receptor (RAR) heterodimers as well as chicken ovalbumin upstream promoter transcription factor (COUP-TF) orphan receptor. In CV-1 cells, the lactoferrin-RARE linked with a heterologous thymidine kinase promoter was strongly activated by RXR homodimers in response to 9-cis-retinoic acid (9-cis-RA) but not to all-trans-RA. When the COUP-TF orphan receptor was cotransfected, the 9-cis-RA-induced RXR homodimer activity was strongly repressed. A unique feature of the lactoferrin-RARE is that it has an AGGTCA-like motif in common with an estrogen-responsive element (ERE). The composite RARE/ERE contributes to the functional interaction between retinoid receptors and the estrogen receptor (ER) and their ligands. In CV-1 cells, cotransfection of the retinoid and estrogen receptors led to mutual inhibition of the other's activity, while an RA-dependent inhibition of ER activity was observed in breast cancer cells. Furthermore, the lactoferrin-RARE/ERE showed differential transactivation activity in different cell types. RAs could activate the lactoferrin-RARE/ERE in human leukemia HL-60 cells and U937 cells but not in human breast cancer cells. By gel retardation analyses, we demonstrated that strong binding of the endogenous COUP-TF in breast cancer cells to the composite element contributed to diminished RA response in these cells. Thus, the lactoferrin-RARE/ERE functions as a signaling switch module that mediates multihormonal responsiveness in the regulation of lactoferrin gene expression.
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PMID:A retinoic acid response element that overlaps an estrogen response element mediates multihormonal sensitivity in transcriptional activation of the lactoferrin gene. 762 14

We have investigated the ability of several transcriptionally inactive estrogen receptor (ER) mutants to block endogenous ER-mediated transcription in MCF-7 human breast cancer cells. In transient transfections of MCF-7 cells, two of the mutants, a frame-shifted ER (S554fs) and a point-mutated ER (L540Q), strongly inhibit the ability of endogenous wild-type ER to activate transcription of estrogen-regulated reporter plasmids. A third mutant, ER1-530, which is missing 65 residues from its carboxy-terminus, is a weaker repressor of estradiol-stimulated transcription. When an estrogen response element (ERE)-thymidine kinase-chloramphenicol acetyltransferase reporter gene is used, S554fs, L540Q, and ER1-530 suppress the transcriptional activity of endogenous MCF-7 ER by 87%, 97%, and 62%, respectively. The magnitude of dominant negative repression is promoter specific; when an ERE-pS2-chloramphenicol acetyltransferase reporter is employed, inhibition of endogenous ER activity by equivalent amounts of S554fs, L540Q, and ER1-530 ranges from 85-97%. Dose-response studies show the S554fs mutant to be the most potent of the three ER mutants as a repressor of estrogen action in these cells. In addition, elevated levels of intracellular cAMP, achieved by the addition of 3-isobutyl-1-methylxanthine plus cholera toxin to cells, fail to compromise the effectiveness of these mutants as dominant negative ERs despite the cAMP-enhanced transcriptional activity of ER. The mutants are also powerful repressors of the agonist activity of trans-hydroxytamoxifen-stimulated ER transcription. The dominant negative activity of the three mutants is lost when the A/B domain of these receptors is deleted, implying an important role for this N-terminal region of the ER in the ability of these mutants to inhibit endogenous wild-type ER activity. All in all, the data suggest that S554fs in particular is a reasonable candidate for studies designed to use a dominant negative ER to inhibit the estrogen- and tamoxifen-stimulated growth of human breast cancer cells.
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PMID:Repression of endogenous estrogen receptor activity in MCF-7 human breast cancer cells by dominant negative estrogen receptors. 762 51

Mouse calbindin-D28k expression is regulated in vivo by estradiol in ovaries, uterus, and oviduct. To determine whether estrogen can have an effect on the transcription of the calbindin-D28k gene, the human breast cancer cells T47D were transiently transfected with a plasmid containing a 1.1 kilobase (kb) PstI/SacII fragment (-1075/+34) of the mouse calbindin gene ligated to the chloramphenicol acetyltransferase (CAT) gene and cotransfected with human estrogen receptor expression vector. T47D cells, transfected and treated with estradiol (10(-11) - 10(-7) M for 64-65 h), exhibited a dose-dependent increase in CAT activity (up to 6.2-fold). Transfection of MCF-7 breast cancer cells with the chimeric gene construct alone also resulted in an estradiol-dependent induction in CAT activity. Deletion mutant analysis demonstrated that there are two regions of the mouse calbindin-D28k promoter (between -1075/-702 and between -175/-78) that contribute to the induction by estradiol. These fragments, when linked to the thymidine kinase promoter to construct a heterologous promoter chimera, were able to convert the thymidine kinase promoter to estrogen responsiveness. In these regions there are multiple imperfect half-palindromic estrogen-responsive elements. Gel retardation assays demonstrated weak protein-DNA interactions that were competed with cold oligonucleotide containing the vitellogenin estrogen-response element. These findings indicate that the mouse calbindin-D28k promoter is capable of conferring estrogen responsiveness, which may be mediated by several imperfect half-palindromic estrogen-responsive elements, and suggest, in light of previous studies concerning 1,25-dihydroxyvitamin D regulation, multiple steroid regulation of the calbindin-D28k gene.
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PMID:Regulation by estrogen through the 5'-flanking region of the mouse calbindin-D28k gene. 777 78

We have analysed cell cycle variations in thymidylate synthase (TS) protein in asynchronously growing NCl H630 and HT 29 colon cancer and MCF-7 breast cancer cell lines. Western immunoblot analysis using the TS 106 monoclonal antibody revealed a 14- to 24-fold variation in TS levels between the peak exponential and confluent growth phase in the three cell lines. Similar variations in TS levels and TS activity were detected using the 5-fluorodeoxyuridine monophosphate and deoxyuridine monophosphate biochemical assays. The percentage of cells in S-phase, which paralleled changes in TS levels, reached a maximum of 38-60% in asynchronous exponentially growing cells compared with 5-10% in confluent cells. In asynchronous exponential cells, analysis of TS levels in each cell cycle phase using two-parameter flow cytometric analysis revealed that TS protein levels were 1.3- to 1.5-fold higher in S than in G0/G1 phase cells, and 1.5- to 1.8-fold higher in G2/M than G0/G1 cells. Similar differences of 1.1- to 1.5-fold between G0/G1 and S-phase and 1.6- to 1.9-fold between G0/G1 and G2/M-phase were detected by Western immunoblot and biochemical assays. TS protein was not detectable by Western blot analysis, flow cytometry or biochemical analysis in the G0/G1 population of confluent cells. Twenty-six per cent of cells in this population were G0 cells compared with 2% in exponentially growing cells. In contrast to TS, a 4-fold difference in thymidine kinase (TK) was detected between G0/G1 and S-phase cells in exponentially growing MCF-7 cells. The level of TS enzyme is associated with cellular proliferation and the percentage of cells in S-phase; however, TS protein is not exclusively associated with S-phase in asynchronously growing cells. The variation in TS levels between exponentially growing and confluent cell population appears to be due to differences in TS levels between G0 and G1 cells.
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PMID:Increased thymidylate synthase protein levels are principally associated with proliferation but not cell cycle phase in asynchronous human cancer cells. 777 4

Pilot retrospective studies have pointed to the prognostic value of thymidine kinase (TK) in breast cancer. We studied the Prolifigen TK-REA assay (Sangtec Medical, Sweden), usually applied to serum, for TK analysis in breast cancer cytosols. Reproducibility was good, provided that small volume pipetting was performed carefully. The TK assay was not influenced by the short-term storage of cytosols in liquid nitrogen or at -80 degrees C. However, some steps appeared critical for good laboratory practice. The TK level was affected by thawing the cytosols more than twice. Tumour storage in liquid nitrogen should be preferred over storage at -80 degrees C. The components of the homogenisation buffer, especially sodium molybdate and KCl can have a marked influence on results. Finally, linearity problems arose with some cytosols. Thus, although assay of TK in cytosols is apparently simple, care must be taken in practice. The TK-REA kit should be standardised before widespread use in breast cancer.
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PMID:Technical evaluation of thymidine kinase assay in cytosols from breast cancers. EORTC Receptor Study Group Report. 785 17

A potentially novel therapeutic strategy for breast cancer treatment involves sensitization of tumor cells to chemotherapy through gene transfer. Clinical application of this approach, however, may be limited by the lack of target cell specificity of currently available gene delivery techniques. Development of vectors with tumor-selective gene expression could overcome this problem. The DF3/MUC1 gene encodes a high molecular weight mucin-like glycoprotein which is overexpressed at the transcriptional level in the majority of human breast cancers. To develop a breast tumor-selective enhancer, we cloned the upstream region of the DF3 gene and have identified a 114-base pair enhancer region that can modulate transcription from heterologous promoters. The present studies demonstrate that the DF3 enhancer sequences can direct selective gene expression in DF3-positive breast carcinoma cells. DF3-positive breast carcinoma cell lines transfected with herpes simplex virus thymidine kinase gene expression cassettes modified by the DF3 enhancer were markedly more sensitive to killing by ganciclovir than were the same cells transfected with the expression cassettes lacking the DF3 enhancer. DF3-negative cell lines transfected with the DF3 enhancer constructs, however, were no more sensitive to ganciclovir than were cells treated with the unmodified expression plasmids. Consistent with an innocent bystander effect, nontransfected human breast carcinoma cells were susceptible in a cell density-dependent manner to ganciclovir-induced cell killing when adjacent to transfected cells. The results also demonstrate that the DF3 enhancer sequences can be effectively incorporated into a retroviral vector to mediate selective gene expression following retroviral infection. These findings suggest that the DF3 promoter/enhancer may be useful for incorporation into vectors designed for gene therapy of breast cancer.
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PMID:Enhancer sequences of the DF3 gene regulate expression of the herpes simplex virus thymidine kinase gene and confer sensitivity of human breast cancer cells to ganciclovir. 792 73

In the natural history of post-menopausal patients with primary breast cancer, high estrogen receptor levels (ER) have been associated with a poor recurrence-free survival. The purpose of this study was to investigate whether there are any biological intratumoral characteristics to support this puzzling clinical observation. In a population of 542 post-menopausal, primary-breast-cancer patients, 3 normal distributions fitted into the frequency distribution curve of the logarithmically transformed ER-EIA values. The biological profiles of the low ER group, and of the intermediate and high ER groups identified in the ER-positive population were compared. Parameters correlated with ER functional aspect (progesterone receptors and PS2), receptors of epidermal growth factor (EGFR), protease cathepsin D and tumor proliferation (deduced from thymidine kinase activity) were analyzed. As previously reported, the levels of progesterone receptors and PS2 increased significantly from the low to the high ER groups. The highest levels of cathepsin D and thymidine kinase which have been previously related to a poor prognosis in breast cancer were found in the low ER group, but high levels were, surprisingly, also found in the high ER group. This study indicates that the ER-positive post-menopausal population is biologically heterogeneous. The high levels of thymidine kinase found in the high ER group suggest that overexpression of ER may be associated with proliferation enhancement, partly explaining the poor spontaneous prognosis related to this subset.
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PMID:Biological heterogeneity of ER-positive breast cancers in the post-menopausal population. 792 97

To identify mechanisms by which the organoselenium compound 1,4-phenylenebis(methylene)selenocyanate (p-XSC) mediates its chemopreventive activities, we have examined its effects on cell lines derived from breast cancer of humans and rats. When log-phase cells were treated with a dose of 1 microM p-XSC, we observed a significant decrease in thymidine kinase (TK) activity within 4 h, and reduced thymidine incorporation after 24-48 h. When the dose of p-XSC was increased to 2 microM, the decrease in TK was accompanied by a modest, but significant, decrease in thymidine incorporation at 4 h, and a greater inhibition after 24-48 h. At a dose of > or = 3 microM, we observed a large decrease in TK, accompanied by > 70% reduction in thymidine incorporation, as well as decreases in mitochondrial activity and cell numbers, all within 4 h. Equal concentrations of selenium in the form of Na2SeO3 had no effect on the parameters described above. These data suggest that inhibition of thymidine kinase is an early effect of p-XSC in cultured breast tumor cells.
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PMID:Inhibition of thymidine kinase in cultured mammary tumor cells by the chemopreventive organoselenium compound, 1,4-phenylenebis(methylene)selenocyanate. 814 69

Malignant brain tumors are responsible for significant morbidity and mortality in both pediatric and adult populations. These common tumors present an enormous therapeutic challenge due to their poor outcome despite radical surgery, high dose radiotherapy and chemotherapy. Survival of patients from the time of diagnosis is measured in months and recurrence after treatment is associated with a life expectancy of weeks. In an attempt to improve this grim prognosis of patients with malignant brain tumors (both primary tumors and secondary metastasis from systemic cancer such as melanoma, lung and breast cancer), we have developed a novel approach to the therapy of brain tumors. This approach makes use of recombinant DNA technology to transfer a sensitivity gene into a brain tumor. This is achieved by direct injection of the tumor with a cell line actively producing a retroviral vector carrying a gene conferring drug sensitivity to the tumor. A retroviral vector is a mouse retrovirus genetically engineered to replace its own genes with a new gene. Such vectors are capable of "infecting" mammalian cells and stably incorporate their new genetic material into the genome of the infected host. The producer cell is an NIH 3T3 cell that has been genetically engineered to continually produce retroviral vectors. The new gene is incorporated into the genome of the tumor cells and expresses the protein which is encoded by the new gene. This protein (the herpes simplex virus enzyme thymidine kinase, HS-tk) sensitizes the tumor cells to an antiviral drug (ganciclovir, GCV) which is a natural substrate for HS-tk. The enzymatic process induced by GCV leads to death of the cell expressing the herpes TK activity, i.e., death of the tumor cells. Since the HS-tk enzyme which is normally present in mammalian cells has very low affinity for GCV, systemic toxicity related to this mechanism is not observed. This type of in vivo gene transfer has several unique features. First, these retroviral-vectors will only integrate and express their genes in cells which are actively synthesizing DNA. Therefore, surrounding non-proliferating normal brain tissue should not acquire the HS-tk gene and will remain insensitive to GCV. Second, all of the transduced tumor cells (and retroviral vector producing cells) will be killed by the host immune response and/or GCV treatment eliminating potential concern about insertional mutagenesis giving rise to malignant cells. This is the first clinical attempt to treat malignant tumors in human beings by in-vivo genetic manipulation of the tumor's genome.
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PMID:Gene therapy for the treatment of brain tumors using intra-tumoral transduction with the thymidine kinase gene and intravenous ganciclovir. 838 92


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