Biomedical subjects

C Deng

Publications and source records attributed to C Deng.

At least 73 records · Page 4Linked to original sources

PubMed1999

Genetic polymorphism of human O6-alkylguanine-DNA alkyltransferase: identification of a missense variation in the active site region.

O6-Alkylguanine-DNA alkyltransferase (AGT, EC 2.1.1.63) is a principle DNA repair protein in repairing O6-alkylguanine in DNA, a major premutagenic lesion produced by environmental and therapeutic alkylating agents. AGT plays a critical role in protecting cells against mutation and cytotoxicity induced by these alkylating agents. The existence of a large interindividual variation in human AGT activity level has been observed and we hypothesize that genetic polymorphism of AGT could be an important determinant for this variation. The present study reports the identification of a novel missense polymorphism in the human AGT gene. The polymorphic alteration occurs at codon 143 in exon 5, converting isoleucine (ATC) to valine (GTC). Because Ile143 is adjacent to the alkyl acceptor Cys145 of the AGT active site and is conserved among mammalian AGTs, amino acid substitution at this position may affect the function of AGT. The codon 143 polymorphism appears to be linked to another new polymorphic alteration at codon 178, which converts lysine (AAG) to arginine (AGG). Because it has been reported that human AGT can be truncated at position 176 without loss of activity, the codon 178 polymorphism may not affect AGT activity. The codon 143/178 polymorphism was found in two of 90 (2%) esophageal cancer patients residing in a high incidence area of China, but was not detected in 60 normal individuals residing in the same area. Six of 28 (210%) non-cancer Caucasian individuals, however, were found to carry this polymorphic allele, suggesting a significant ethnic difference in distribution of this codon 143/178 polymorphism between Chinese and Caucasian individuals. In addition, we confirmed the existence of a codon 84 genetic polymorphism previously identified in a Japanese population, which converts leucine (CTT) to phenylalanine (TTT). The distribution of codon 84 polymorphism was 16%, 20% and 36%, respectively, in the Chinese esophageal cancer patients, Chinese and Caucasian non-cancer individuals. Coexistence of codons 84 and 143/178 polymorphic alterations was found in one Caucasian individual. In all the Chinese (n = 150) and Caucasian (n = 28) samples examined, we were unable to detect a previously reported codon 160 polymorphism (Gly to Arg) which occurred in 10-25% of the Japanese individuals and was shown to affect the reaction of AGT with the drug O6-benzylguanine. The functional significance of the codon 143/178 genetic polymorphism of human AGT and its role in determining an individual's susceptibility to environmental alkylating carcinogens and response to alkylating chemotherapeutic drugs both remain to be studied.

Adult↗

PubMed1999

A genetic model of substrate deprivation therapy for a glycosphingolipid storage disorder.

Inherited defects in the degradation of glycosphingolipids (GSLs) cause a group of severe diseases known as GSL storage disorders. There are currently no effective treatments for the majority of these disorders. We have explored a new treatment paradigm, substrate deprivation therapy, by constructing a genetic model in mice. Sandhoff's disease mice, which abnormally accumulate GSLs, were bred with mice that were blocked in their synthesis of GSLs. The mice with simultaneous defects in GSL synthesis and degradation no longer accumulated GSLs, had improved neurologic function, and had a much longer life span. However, these mice eventually developed a late-onset neurologic disease because of accumulation of another class of substrate, oligosaccharides. The results support the validity of the substrate deprivation therapy and also highlight some limitations.

Animals↗

PubMed1999

Differential regulation of p21 by p53 and Rb in cellular response to oxidative stress.

Oxidative stress to mammalian cells causes cellular damage and triggers inducible cellular responses leading to cell death by apoptosis. In this paper, we report that p53 was required for programmed cell death induced by oxidative stress in both mouse and human cells and that p53 transactivation was involved in induction of oxidative cell death. Furthermore, we show that p21 was highly responsive to oxidative stress in a p53-dependent manner and that ectopic expression of p21 could increase cellular susceptibility to oxidative stress in the absence of p53. However, p21 was not required for p53-directed oxidative cell death because mouse embryo fibroblasts MEFs lacking p21(p21-/- MEFs) were still susceptible to oxidative cell death. Interestingly, bax, a cell-death mediator regulated by p53, was overexpressed in p21-/- MEFs that underwent cell death by oxidative stress, suggesting a compensation for loss of p21 that may be responsible for the existence of cell-death responses in p21-knockout mouse fibroblasts. Finally, we provide evidence that the retinoblastoma gene product (Rb) is a negative regulator of p21 and a repressor of the cellular apoptotic process. Because p21 is regulated by p53 positively and by Rb negatively, p21 may be a link between p53 and Rb in determining cell fate after oxidative damage.

Animals↗

PubMed1999

[HLA-DQA1 genes involved in the genetic susceptibility to duodenal ulcer in Wuhan Hans].

OBJECTIVE: To study the genetic susceptibility of HLA-DQA1 alleles to duodenal ulcer in Chinese Hans from Wuhan and its nearby regions. METHODS: Seventy patients with duodenal ulcer and fifty healthy controls were examined for HLA-DQA1 genotypes. HLA-DQA1 typing was carried out by digesting the locus specific polymerase chain reaction amplified products with alleles specific restriction enzymes (PCR-RFLP), Apal I, Basj I, Hph I, Fok I, Mbo II and Mnl I. RESULTS: The allele frequency of DQA1 0301 in patients with duodenal ulcer (64.3%) was significantly higher than that in healthy controls (36%). In contrast, the allele frequency of DQA1 0102 in patients with duodenal ulcer (8.6%) was significantly lower than that in healthy controls (26%). CONCLUSION: These findings suggest that DQA1 0301 is a susceptible gene for duodenal ulcer in Wuhan Hans while DQA1 0102 is its resistant gene, and there are immunogenetic differences in HLA-DQA1 locus between duodenal ulcer patients and healthy controls.

Adolescent↗

PubMed1999

[Effects of protocol HX-97 on mobilization, collection and hematopoietic reconstitution of peripheral blood stem cells transplantation].

In order to enhance the effects of peripheral blood stem cell mobilization, collection and hematopoietic reconstitution, we observed and evaluated the effects of Protocol HX-97 on 22 patients who received allogeneic or autologous peripheral blood stem cell transplants from April 1997 to June 1999. rhG-CSF was used for mobilization at a dose of 300 micrograms/day for 6 days; the sixth dose was given an hour and a half before leukapheresis. High dose chemotherapy and rhG-CSF were given for autologous peripheral blood stem cell mobilization; the chemotherapy should be intensive enough to reduce the patients' peripheral WBC to less than 1.0 x 10(9)/L, and the beginning of using rhG-CSF should be just at the time of WBC's rising from the nadir. rhGM-CSF and rhG-CSF were given sequentially for hematopoietic reconstitution after transplantation. The results showed that leukaphereses were successfully performed for peripheral blood stem cell collection. Sixteen cases needed apheresis only once, and 6 cases needed it twice. The harvests were 2.5-10.7 x 10(8)/kg MNC, 2.5-20.0 x 10(6)/kg CD34+ cells (including 1.8-7.5 x 10(6)/kg CD34+CD33-, 0.7-12.5 x 10(6)/kg CD34+CD33+), and 3.5-6.3 x 10(5)/kg CFU-GM. Hematopoietic function recovered to > 0.5 x 10(9)/L of neutrophil count in allo-PBSCT at 14-20 days and in auto-PBSCT at 12-20 days, and to > 20 x 10(9)/L of platelet count in allo-PBSCT and in auto-PBSCT at 16-34 days and 16-28 days, respectively. At day +30 post-transplantation, chromosome analysis and DNA finger print assessment of bone marrow cells indicated that the patients' hematopoietic function had been reconstituted. This study suggests that Protocol HX-97 is an effective approach to mobilization of peripheral blood stem cell transplantation, and it is relatively cost-effective.

Adult↗

PubMed1999

[The effects of Xuezhikang on serum lipid profile, thromboxane A2 and prostacyclin in patients with hyperlipidemia].

OBJECTIVE: To study the effects of Xuezhikang on lipid profile, thromboxane (TX) A(2), prostacyclin (PGI(2)) in patients with hyperlipidemia. METHODS: 91 patients with hyperlipidemia were randomly divided into a treatment group (n = 47, Xuezhikang 1.2 g/d Bid, p.o) and control group (n = 44, gemfibrozil 1.2 g/d Bid, p.o). serum lipids, TXB(2) and 6-Keto-PGF(1alpha) were determined before and 8 weeks after the treatment. RESULTS: (1) After 8 weeks of treatment, the level of serum total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C) decreased by 21.6% (P < 0.01) and 33.3% (P < 0. 01) in the Xuezikang group and by 20.4% (P < 0.01) and 24.8% (P < 0.01) in the gemfibrozil group respectively. Serum high density lipoprotein cholesterol (HDL-C) level elevated by 33.7% in the Xuezhikang group (P < 0.01) and 26.9% in the gemfibrozil group (P < 0.01). The effect of Xuezhikang was the same as gemfibrozil. There was no statistically significant difference between the effects of these two drugs. Triglyceride (TG) level decreased by 23.3% in the Xuezhikang group (P < 0.01) and 40.3% in the gemfibrozil group (P < 0.01). TG lowering effect of gemfibrozil was superior to that of Xuezhikang (P < 0.05). (2) The level of lipoprotein (a) [LP (a)] in the plasma decreased by 28.2% (P < 0.01) in the Xuezhikang group and by 4.9% (P > 0.05) in the gemfibrozil group. LP (a) lowering effect of Xuezhikang was superior to that of gemfibrozil (P < 0.01). (3)The Level of thromboxane (TX) B(2) in the plasma decreased by 34.2% in the Xuezhikang group (P < 0.01) and by 8.4% in the gemfibrozil group (P < 0.01). TXB(2) lowering effect of Xuezhikang was superior to that of gemfibrozil (P < 0.01). The level of 6-KetO-PGF(1alpha) in the plasma elevated by 65.4% in the Xuezhikang group (P < 0.01) and by 11.7% in the gemfibrozil group (P < 0.01); the effect of Xuezhikang was superior to that of gemfibrozil (P < 0.01). CONCLUSION: Xuezhikang could markedly decrease the level of TC and LDL-C and elevate that of HDL-C in patients with hyperlipidemia and the effects of Xuezhikang were the same as those of gemfibrozil. TG lowering effect of gemfibrozil was superior to that of Xuezhikang, but Xuezhikang could markedly decrease the level of Lp (a) and regluate the balance between TXA(2) and PGI(2), its effect being superior to that of gemfibrozil.

Aged↗

PubMed1999

[Effect of in vitro interferon on bone marrow megakaryocyte in patients with idiopathic thrombocytopenic purpura].

The effect of rIFN alpha-2a on the megakaryocyte colony growth and maturation was observed in 33 patients with idiopathic thrombocytopenic purpura (CITP) in vitro by plasma clot cultures and by GP III a McAb and ABC kit. Twenty five healthy persons were in the control group. The results showed that the number of colony formation units of megakaryocyte in the patients was similar to that in the controls, but the diameter and area levels of megakaryocyte in the patients were lower. The ratio of inhibition of rIFN alpha-2a on megakaryocyte progenitors colony growth was significantly lower in the patients and was lowest in the group with increasing number of megakaryocytes on bone marrow smear. The rIFN alpha-2a had no effect on promoting the megakaryocyte maturation. Since this study has indicated that the inhibition of rIFN alpha-2a on colony formation unit of megakaryocyte is slight in CITP, interferon therapy should be a suitable prescription for the CITP patients who have an increasing number of megakaryocyte on bone marrow smear.

Adolescent↗

PubMed1999

[Detection of Epstein-Barr viral genome in tumor cells of Warthin's tumor of parotid gland].

OBJECTIVE: To evaluate the relations between Warthin's tumors of salivary gland and Epstein-Barr virus (EBV). METHODS: 75 cases of salivary gland Warthin's tumor and 20 cases of normal salivary gland tissue were examined for to detect EBV genoma by using the polymerase chain reaction (PCR) of DNA, 62 cases of single Warthin's tumor and 13 cases of multiple/bilateral Warthin's tumor's. RESULTS: EBV DNA was detected in 13 cases of single Wathin's tumors, 9 cases of multiple/bilateral Warthin's tumor and 3 cases of normal salivary gland. CONCLUSION: There was a close relationship between EBV and multiple/bilateral Warthin's tumors.

Adenolymphoma↗

PubMed1998

The Th2 cytokine IL-4 is not required for the progression of antibody-dependent autoimmune myasthenia gravis.

Experimental autoimmune myasthenia gravis (EAMG), a disorder of the neuromuscular junction, is mediated by autoantibodies against muscle nicotinic acetylcholine receptor (AChR). The roles of IFN-gamma (Th1) and IL-4 (Th2) cytokines in the initiation and progression of this disease are not fully understood. Recently, we have demonstrated that IFN-gamma is necessary for the initiation of tAChR-induced EAMG in mice. However, the role of IL-4 in the progression of clinical EAMG remained undetermined. In this study we have addressed the contribution of IL-4 in the disease progression in IL-4(-/-) C57BL/6j mice whose IL-4 gene has been disrupted. Following immunization with Torpedo (t) AChR, the IL-4(-/-) mice readily developed signs of muscle weakness and succumbed to clinical EAMG with kinetics similar to the susceptibility of IL-4(+/+) mice. The tAChR-primed lymph node cells from IL-4(-/-) mice vigorously proliferated to tAChR and to its dominant alpha146-162 sequence associated with disease pathogenesis. However, these T cells secreted higher levels of IFN-gamma and IL-2, suggesting the development of a Th1 default pathway in these mice. Nevertheless, the IL-4 mutation had no effect on the recruitment of CD4+ Vbeta6+ T cells specific to the dominant tAChR alpha146-162 sequence in vivo. Immune sera from IL-4(-/-) mice showed a dramatic increase in mouse AChR-specific IgG2a levels followed by a concomitant decrease in IgG1 levels, but these mice did not exhibit an accelerated disease. In conclusion, we have demonstrated for the first time that IL-4 is not required either for the generation of a pathogenic anti-AChR humoral immune response or for progression of clinical EAMG in mice.

Amino Acid Sequence↗

PubMed1998

Bilaterally projecting neurons in the two visual pathways of chicks.

By means of a double-labeling technique, we have investigated the organization of the bilateral thalamo-Wulst and tecto-rotundal projections in 2-day old chicks. After injecting fluorogold (FG) into one side of the visual Wulst and rhodamine B isothiocyanate (RITC) into the other side of the visual Wulst, the labeled neurons in the nucleus geniculatus lateralis pars dorsalis (GLd) were examined. Although the distribution areas of ipsilaterally and contralaterally labeled neurons overlap partly, very few double-labeled neurons were found (only 0.01% double-labeled neurons). This suggests that the ipsilateral and contralateral projections to the Wulst come from different neuronal populations of the thalamus. The FG and RITC were also injected into the rotundal nuclei (Rt) on each side of the thalamus and the labeled neurons in the optic tectum (TeO) were examined. In the TeO, the distribution areas of the neurons labeled ipsilaterally and contralaterally to Rt overlap completely and we found that up to 45% of the tectal cells were double-labeled by both FG and RITC. Therefore, many tectal neurons have axon collaterals so that they project to the Rt on both sides of the thalamus and must send information simultaneously to both sides of the brain. The differences in the structural organization of the two visual pathways are discussed with reference to the transmission of information to higher centers on both sides of the brain.

Animals↗

PubMed1998

Organisation of the tectorotundal and SP/IPS-rotundal projections in the chick.

The organisation of the neural projections from the optic tectum and pretectal nuclei complex, n. subpretectalis / n. interstitio-pretecto-subpretectalis (SP/IPS), to the nucleus rotundus (Rt) in chicks was studied by using retrograde tracing techniques. After the injection of fluorescent retrograde tracers, rhodamine-conjugated latex microspheres, fluorescein-conjugated latex microspheres, True Blue, Fluoro-Gold, or rhodamine B isothiocyanate, into different regions of Rt and its middorsal extension, the nucleus triangularis (T), the distribution of retrogradely labelled neuronal cell bodies in the tectum and pretectal nuclei was assessed. Both the ipsilateral and contralateral tectorotundal projections were found to be organised topographically in as much as different sublaminas of the stratum griseum centrale (SGC) project in an orderly manner to Rt and T. The deepest stratum of SGC overlapping into the stratum album centrale projects to T. Deep SGC projects to the dorsal Rt and superficial SGC to the ventral Rt. A band running through the centre of Rt receives input from the central sublamina of SGC, and the caudal central Rt receives input from a deeper sublamina than does the rostral central Rt. The SP/IPS projects to the ipsilateral Rt only and the projection order is dorsal SP to dorsal Rt, ventral SP to ventral Rt and middle SP to the central band of Rt. The neurones in IPS and the nucleus of the tractus tectothalamicus project to T. Thus, Rt and T receive topographically both tecto- (excitatory) and SP/IPS- (inhibitory) projections. The possible functional implications for parallel information processing in these projections are discussed.

Animals↗

PubMed1998

Involvement of p21 and p27 in the regulation of CDK activity and cell cycle progression in the regenerating liver.

In tissue culture systems, p21 and p27 inhibit cyclin-dependent kinase (CDK) activity and cell cycle progression in response to numerous stimuli, but little is known about their involvement in cell growth in vivo. We examined the modulation of CDK activity by these proteins after 70% partial hepatectomy (PH), an in vivo model of synchronous hepatocyte cell cycle progression. After PH in BALB/c mice, p21 was induced during the prereplicative (G1) phase and was maximally expressed after peak hepatocyte DNA synthesis. p27 was present in quiescent liver and was minimally induced after PH. p21 and p27 immunoprecipitated with CDK2, CDK4, and cyclin D1 in the regenerating liver. The activity of CDK2-, CDK4- and cyclin D1-associated kinases was upregulated after PH, and maximal activity of these enzyme complexes corresponded to peak DNA synthesis. Immunodepletion experiments suggested that p27 plays a role in downregulating CDK2 activity before and after peak DNA synthesis. Compared to cogenic wild-type mice, p21-/- mice demonstrated evidence of markedly accelerated hepatocyte progression through G1 phase after PH: DNA synthesis, upregulation of cyclin A and PCNA, induction of cyclin D1- and CDK2-associated kinase activity, and appearance of a phosphorylated retinoblastoma protein (Rb) species occurred earlier in the p21-/- mice. These results suggest that p21 and p27 modulate CDK activity in the regenerating liver, and that p21 regulates the rate of progression through G1 phase of the cell cycle in vivo.

Animals↗

PubMed1998

The tumor suppressor SMAD4/DPC4 is essential for epiblast proliferation and mesoderm induction in mice.

Members of the transforming growth factor (TGF)-beta superfamily have been shown to play a variety of important roles in embryogenesis, including dorsal and ventral mesoderm induction. The tumor suppressor SMAD4, also known as DPC4, is believed to be an essential factor that mediates TGF-beta signals. To explore functions of SMAD4 in development, we have mutated it by truncating its functional C-domain. We show that Smad4 is expressed ubiquitously during murine embryogenesis. Mice heterozygous for the Smad4(ex8/+) mutation are developmentally normal, whereas homozygotes die between embryonic day 6.5 (E6.5) and 8.5. All Smad4(ex8/ex8) mutants are developmentally delayed at E6 and show little or no elongation in the extraembryonic portion of late egg cylinder stage embryos. Consistent with this, cultured Smad4(ex8/ex8) blastocyst outgrowths suffer cellular proliferation defects and fail to undergo endoderm differentiation. Although a portion of mutant embryos at E8.5 show an increase in the embryonic ectoderm and endoderm, morphological and molecular analyses indicate that they do not form mesoderm. Altogether, these data demonstrate that SMAD4-mediated signals are required for epiblast proliferation, egg cylinder formation, and mesoderm induction.

Animals↗

PubMed1998

The effect of B cell deficiency on the immune response to acetylcholine receptor and the development of experimental autoimmune myasthenia gravis.

To study the involvement of B cells in the immune response to acetylcholine receptor (AChR), B-cell-deficient (mu mutant) and control wild-type C57BL/6 mice were immunized with AChR and assessed for clinical and immunopathological manifestations of experimental autoimmune myasthenia gravis (EAMG). The mu mutant mice failed to generate anti-AChR antibodies and were completely resistant to the induction of EAMG. However, mu mutant mice developed clinical EAMG when antibodies to the AChR main immunogenic region were passively transferred. Further, the in vivo expansion of lymph node cells after AChR immunization was greatly impaired in mu mutant mice. The mu mutant mice gave an effective in vitro T cell immune response to the immunodominant pathogenic AChR alpha chain peptide 146-162 (alpha 146-162) and to the whole AChR protein when tested on day 90 after immunization with AChR, whereas the response to both AChR and its alpha 146-162 peptide was reduced when tested on day 7 after immunization. The in vitro production of IFN-gamma and IL-2 by AChR-specific and alpha 146-162 peptide-specific lymphocytes was lower in mu mutant mice. The AChR immune mu mutant T cells proliferated and produced IFN-gamma when AChR or alpha 146-162 peptide was presented by wild-type irradiated AChR-primed antigen-presenting cells (APCs). This indicates that B cells are important in the processing and presentation of AChR dominant peptide in vitro during the initial immune response to AChR. However, APCs of non-B-cell lineage are sufficient to process AChR and prime the T cells to AChR dominant T cell epitope peptides.

Animals↗

PubMed1998

Fibroblast growth factor receptor 2 (FGFR2)-mediated reciprocal regulation loop between FGF8 and FGF10 is essential for limb induction.

FGFR2 is a membrane-spanning tyrosine kinase that serves as a high affinity receptor for several members of the fibroblast growth factor (FGF) family. To explore functions of FGF/FGFR2 signals in development, we have mutated FGFR2 by deleting the entire immunoglobin-like domain III of the receptor. We showed that murine FGFR2 is essential for chorioallantoic fusion and placenta trophoblast cell proliferation. Fgfr2(DeltaIgIII/DeltaIgIII) embryos displayed two distinct defects that resulted in failures in formation of a functional placenta. About one third of the mutants failed to form the chorioallantoic fusion junction and the remaining mutants did not have the labyrinthine portion of the placenta. Consequently, all mutants died at 10-11 days of gestation. Interestingly, Fgfr2(DeltaIgIII/DeltaIgIII) embryos do not form limb buds. Consistent with this defect, the expression of Fgf8, an apical ectodermal factor, is absent in the mutant presumptive limb ectoderm, and the expression of Fgf10, a mesenchymally expressed limb bud initiator, is down regulated in the underlying mesoderm. These findings provide direct genetic evidence that FGF/FGFR2 signals are absolutely required for vertebrate limb induction and that an FGFR2 signal is essential for the reciprocal regulation loop between FGF8 and FGF10 during limb induction.

Animals↗

PubMed1998

[MMC conditioning regimen (Melphalan, MeCCNU and cyclophosphamide) followed by allogeneic peripheral blood stem cells transplantation for chronic myeloid leukemia].

This paper reports 3 cases of allogeneic peripheral blood stem cell transplantation (Allo-PBSCT) for the patients with chronic myeloid leukemia (CML). The patients received MMC preparative regimen with high dose chemotherapy (Melphalan 170 mg/m2, p.o. on Day-5, MeCCNU 400 mg/m2, p.o. on Day-4, and Cyclophosphomide 60 mg/kg/day, i.v. on Days-3 and -2). The HLA-identical sibling donors received filgrastim (rhG-CSF) for mobilization at a dose of 300 micrograms/day for 6 days. Leukaphereses were done at the 6th day of mobilization. A median of 8000 ml (2 times total blood volume) of blood was processed the collecting: 2.5-4.5 x 10(8)/kg MNC, 12.8-20.0 x 10(6)/kg CD34+ cells (including 4.8-7.5 x 10(6)/kg CD34+CD33-, 8.0-13.0 x 10(6)/kg CD34+CD33+), and 3.5-4.3 x 10(5)/kg CFU-GM. Cyclosporin A and methotrexate were used for GVHD prophylaxis. Hematopoitic function recovered as for 14-20 days to > 0.5 x 10(9)/L of neutrophil count, and for 16-34 days to > 20 x 10(9)/L of platelet count. At day + 100, chromosome analysis of bone marrow cells showed that complete chimera without ph1 positive chromosome in Cases 1 and 3, and a partial chimera with 73% donor karyotype in Case 2. All patients now are in disease free survival. No episode of acute graft versus host disease (GVHD) developed. It was concluded that HLA matched sibling allogeneic PBSCT result in rapid hematopoitic reconstitution and the MMC conditioning regimen is effective both in leukemic cells eradication and in immunosuppression for stem cells engraftment, and the drug related toxicity could be tolerated by patients.

Adult↗

PubMed1998

Expression of estrogen sulfotransferase in MCF-7 cells by cDNA transfection suppresses the estrogen response: potential role of the enzyme in regulating estrogen-dependent growth of breast epithelial cells.

Estrogen sulfotransferase (EST) is a cytosolic enzyme that catalyzes the sulfonation of estrogens at the 3-hydroxyl position by use of 3'-phosphoadenosine-5'-phosphosulfate as an activated sulfate donor. Although largely known and studied as a phase II metabolic enzyme with prominent expression in the liver, the high substrate specificity of EST (with a high Vmax/Km value for estrogen) suggests that expression of the enzyme in extrahepatic, estrogen target tissues, such as the breast epithelium, may constitute an effective mechanism for local estrogen regulation as well. In this study, we have evaluated the physiological significance of EST expression by cDNA transfection studies with use of the estrogen-dependent MCF-7 breast cancer cell line as a model system. We show that expression of EST in MCF-7 cells effectively reduces the cells' response to physiological concentrations of estradiol (10 nM) by up to 70% as determined in an estrogen-responsive reporter gene assay. In addition, we demonstrate that expression of EST similarly inhibits estrogen-stimulated DNA synthesis and cell proliferation by 21% and 46%, respectively. (The thymidine incorporation rate was measured 3 days after and the cell numbers were counted 8 days after transfection.) These results provide direct evidence for the functional significance of in situ EST expression in the breast epithelium and suggest that abnormal regulation of the enzyme may have pathological implications in the development and maintenance of hormone-dependent breast carcinomas.

Breast↗

PubMed1998

Fibroblast growth factor receptor 4, implicated in progression of islet cell carcinogenesis by its expression profile, does not contribute functionally.

Fibroblast growth factor receptor 4 (FGFR4) gene expression is activated in late-stage beta-cell tumors that develop in transgenic mice harboring SV40 large T antigen (Tag) gene that is under the transcriptional control of the insulin promoter (RIP-Tag). The FGFR4 gene was active in cell lines derived from tumors but not in cells derived from hyperplastic islets. We used both gain-of-function and loss-of-function FGFR4 transgenic mice to determine whether FGFR4 modulates islet cell tumorigenesis and, if so, to identify the nature of the effect. Both types of FGFR4 transgenic mice were viable and fertile and developed islet tumors when crossed with RIP-Tag mice. Remarkably, there was no significant perturbation in the tumorigenesis pathway resulting from either chronic up-regulation or absence of FGFR4 gene expression. Analyses included the incidence and size of tumors, rate of cell proliferation, cell density, and life span. We conclude that FGFR4 gene activation is a marker of but is not causal for beta-cell transformation.

Adenoma, Islet Cell↗