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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Thirty postmenopausal women (11 omnivores, 10 vegetarians and 9 apparently healthy women with surgically removed breast cancer) were investigated with regard to the association of their urinary excretion of estrogens, lignans and isoflavonoids (all diphenols) with plasma sex hormone binding globulin (SHBG). A statistically significant positive correlation between urinary total diphenol excretion and plasma SHBG was found which remained statistically significant after elimination of the confounding effect of body mass determined by body mass index (BMI). Furthermore we found a statistically significant negative correlation between plasma SHBG and urinary excretion of 16 alpha-hydroxyestrone and estriol which also remained significant after eliminating the effect of BMI. Furthermore we observed that enterolactone (Enl) stimulates the synthesis of SHBG by HepG2 liver cancer cells in culture acting synergistically with estradiol and at physiological concentrations. Enl was rapidly conjugated by the liver cells, mainly to its monosulfate. Several lignans and the isoflavonoids daidzein and equol were found to compete with estradiol for binding to the rat uterine type II estrogen binding site (the s.c. bioflavonoid receptor). It is suggested that lignans and isoflavonoids may affect uptake and metabolism of sex hormones by participating in the regulation of plasma SHBG levels and in this way influence their biological activity and that they may inhibit cancer cell growth like some flavonoids by competing with estradiol for the type II estrogen binding sites.
J Steroid Biochem Mol Biol 1992 Mar
PMID:Dietary phytoestrogens and cancer: in vitro and in vivo studies. 131 77

Point-mutational activation of the c-Ki-ras proto-oncogene has been shown to be rare in human hepatocellular carcinoma, the most common primary liver cancer and one usually associated with chronic viral infection. To reveal the association of c-Ki-ras activation with cholangiocarcinogenesis under different etiological backgrounds, the incidence of point mutation at codons 12 and 13 of the c-Ki-ras proto-oncogene was examined in three groups of human liver cancers with differentiation to biliary epithelial cells: Group 1, cholangiocellular carcinoma in Japanese with normal livers; Group 2, cholangiocellular carcinoma in Thais who had lived in an area where the liver fluke Opisthorchis viverrini is endemic; and Group 3, combined hepatocellular-cholangiocellular carcinoma, a rare type showing features of both hepatocellular and biliary epithelial differentiation, in Japanese with chronic viral hepatitis with or without cirrhosis. The polymerase chain reaction and direct sequencing of its product were used to detect the mutation. Point mutation at codon 12 of the c-Ki-ras gene was detected in five (56%) of nine cases in Group 1. In contrast, the mutation was not detected in any of the cases in Groups 2 and 3. Therefore, point-mutational activation of c-Ki-ras did not seem to be involved in the development of primary liver cancers associated with apparent chronic irritation of liver cells or biliary epithelial cells caused by exogenous liver-fluke or viral infection. On the other hand, point-mutational activation of the c-Ki-ras proto-oncogene may be involved in cholangiocarcinogenesis in liver without preexisting liver-fluke or viral infection.
Mol Carcinog 1992
PMID:Cholangiocarcinomas in Japanese and Thai patients: difference in etiology and incidence of point mutation of the c-Ki-ras proto-oncogene. 133 66

A diet deficient in choline can cause liver cancer in rats. The previous work since 1932 emphasized the fat-removing ability of choline from the liver. There are other dietary factors, including methionine, which, like choline, can remove fat from the liver. These factors were termed as lipotropes. Since then, choline deficiency and lipotrope deficiency are used synonoumously. Recent work since 1980 has clearly demonstrated that choline deficiency (CD) and lipotrope deficiency (LD) are not the same. Generation of free radicals, DNA alterations, liver cell death, and liver cancer that occur due to CD are not generated by LD. Generation of free radicals due to CD diet and some of the agents that counteract free radical action also prevent CD effects except for lipid accumulation in the liver. Despite the recent observations on the role of phospholipase A2 (PLA2) as the protector of the membranes, it has been found that by preventing the rise of PLA2 in the liver, cell death can be prevented. These new findings give choline a distinct role in liver cell death and cancer rather than the role of lipotrope. A new hypothesis linking dietary choline deficiency and liver cancer has been discussed.
Crit Rev Biochem Mol Biol 1995
PMID:New insight into the biochemical pathology of liver in choline deficiency. 758 79

The gene encoding the tumour suppressor protein p53 is one of the most commonly mutated genes in human cancers. Analysis of the mutational events that target the p53 gene has revealed evidence for both exogenous and endogenous mutational mechanisms. For example, the p53 mutational spectrum reveals evidence for a direct causal effect of ultraviolet radiation in skin cancer, of aflatoxin B1 in liver cancer and of tobacco smoke in lung cancer. This novel field, molecular epidemiology of human cancer risk, has added a new dimension to classical associative epidemiology by providing a direct link between human cancer and carcinogen exposure.
Mol Med Today 1996 Jan
PMID:The p53 tumour suppressor gene: a model for molecular epidemiology of human cancer. 879 49

Tamoxifen, an important drug in breast cancer treatment, causes liver cancer in rats. The standard range of in vitro tests have failed to show that it causes DNA damage, but 32P-postlabelling and DNA-binding studies have shown that tamoxifen forms DNA adducts in rat liver. In 1995 a transgenic rat (Big Blue; Stratagene, La Jolla, CA) became available which harbours the bacterial lacI gene, thereby allowing the in vivo study of tamoxifen mutagenesis. Recently, we [Styles JA et al. (1996): Toxicologist 30; 161] showed that tamoxifen caused on increase in the mutation frequency at the lacI gene in these transgenic rats. In this study, we report on our preliminary analysis of the mutational spectra of 33 control and 38 tamoxifen-induced mutant lacI genes. Plasmid DNA containing the lacI gene was isolated from the mutant phages and its DNA sequence determined. In the control animal group, 81% of the mutant lacI genes were point mutations, whilst in the tamoxifen-treated group, 62% of the mutant lacI genes were point mutations. Of the tamoxifen-induced mutants, 43% were GC-->TA transversions and 70% of point mutations. In the control group, GC-->TA transversions were 19% of all mutations and 24% of point mutations. Thus, compared with control animals, tamoxifen treatment had significantly increased the proportion of GC-->TA transversions.
Environ Mol Mutagen 1996
PMID:Mutational spectra of tamoxifen-induced mutations in the livers of lacI transgenic rats. 899 Oct 74

We previously demonstrated that a locus (or loci) linked to the D11S436 marker, which is within the approximately 6-Mb cen-p12 region of human chromosome 11, suppresses the tumorigenic potential of some rat liver epithelial tumor microcell hybrid (MCH) cell lines. To more precisely map this putative liver tumor suppressor locus, we examined 25 loci from human chromosome 11 in suppressed MCH cell lines. Detailed analysis of these markers revealed a minimal area of overlap among the suppressed MCH cell lines corresponding to the chromosomal region bounded by (but not including) microsatellite markers D11S1319 and D11S1958E and containing microsatellite markers D11S436, D11S554, and D11S1344. Direct examination of the kang ai 1 (KA/1) prostatic adenocarcinoma metastasis suppressor gene (which is closely linked to D11S1344) produced evidence suggesting that this locus was not responsible for tumor suppression in this model system. In addition, our data strongly suggested that the putative liver tumor suppressor locus was distinct from other known 11p tumor suppressor loci, including the multiple exotoses 2 locus (at 11p11.2-p12), Wilms' tumor 1 locus (at 11p13), and Wilms' tumor 2 locus (at 11p15.5). The results of this study significantly narrowed the chromosomal location of the putative liver tumor suppressor locus to a region of human 11p11.2-p12 that is approximately 950 kb. This advance forms the basis for positional cloning of candidate genes from this region and, in addition, identified a number of chromosomal markers that will be useful for determining the involvement of this locus in the pathogenesis of human liver cancer.
Mol Carcinog 1997 Aug
PMID:Localization of a putative liver tumor suppressor locus to a 950-kb region of human 11p11.2-p12 using rat liver tumor microcell hybrid cell lines. 929 Jul 4

The HBx protein of hepatitis B virus (HBV) is a small transcriptional transactivator that is essential for infection by the mammalian hepadnaviruses and is thought to be a cofactor in HBV-mediated liver cancer. HBx stimulates signal transduction pathways by acting in the cytoplasm, which accounts for many but not all of its transcriptional activities. Studies have shown that HBx protein activates Ras and downstream Ras signaling pathways including Raf, mitogen-activated protein (MAP) kinase kinase kinase (MEK), and MAP kinases. In this study, we investigated the mechanism of activation of Ras by HBx because it has been found to be central to the ability of HBx protein to stimulate transcription and to release growth arrest in quiescent cells. In contrast to the transient but strong stimulation of Ras typical of autocrine factors, activation of Ras by HBx protein was found to be constitutive but moderate. HBx induced the association of Ras upstream activating proteins Shc, Grb2, and Sos and stimulated GTP loading onto Ras, but without directly participating in complex formation. Instead, HBx is shown to stimulate Ras-activating proteins by functioning as an intracellular cytoplasmic activator of the Src family of tyrosine kinases, which can signal to Ras. HBx protein stimulated c-Src and Fyn kinases for a prolonged time. Activation of Src is shown to be indispensable for a number of HBx activities, including activation of Ras and the Ras-Raf-MAP kinase pathway and stimulation of transcription mediated by transcription factor AP-1. Importantly, HBx protein expressed in cultured cells during HBV replication is shown to activate the Ras signaling pathway. Mechanisms by which HBx protein might activate Src kinases are discussed.
Mol Cell Biol 1997 Nov
PMID:Activation of Src family kinases by hepatitis B virus HBx protein and coupled signaling to Ras. 934 5

Cytochrome P450 (CYP) 2A5 is involved in the metabolism of carcinogens like aflatoxin B1 and N-nitrosodiethylamine (NDEA), and CYP2A5 levels are increased in some pathological states of the liver (e.g., infectious hepatitis and porphyria). We analyzed the expression of CYP2A5 during experimental liver carcinogenesis in three different mouse strains (C3H/He, C57BL/6J, and B6C3F1) with immunohistochemical techniques and in situ hybridization. In normal liver, CYP2A5 protein and mRNA were detected in centrilobular hepatocytes only. Phenobarbital treatment increased the number of CYP2A5-positive centrilobular hepatocytes and the CYP2A5-positive areas were extended into the middle zone in all strains, but periportal hepatocytes remained negative. Fifty percent of the spontaneous foci in untreated mice, over 90% of the foci in mice treated with NDEA or phenobarbital and all of the hepatocellular adenomas and carcinomas displayed positive immunostaining and a strong CYP2A5 mRNA signal by in situ hybridization. In the liver tumors metastasized to the lung, expression of CYP2A5 had largely disappeared. CYP2A5 expression in neoplastic and putative preneoplastic lesions, although sometimes heterogeneous, was apparently independent of the typical zonal expression pattern in normal tissue. As expected, the C57BL/6J mice developed fewer foci and tumors than the C3H/He and B6C3F1 mice, but the phenotype of CYP2A5 overexpression was similar in all the strains. Our data suggest that the increased expression of CYP2A5 may play an important role in the development of liver cancer in mice and may be used as a novel marker for spontaneous and NDEA-induced mouse liver foci.
Mol Carcinog 1998 Aug
PMID:Expression of cytochrome P450 2A5 in preneoplastic and neoplastic mouse liver lesions. 972 15

Our earlier reports indicated that the changes of age-adjusted incidence rates (AAIRs) of any 2 tumors in time and space, as investigated by the sequential regression analysis, showed a good fitness to the equilibrium model under the control of the law of mass action. The purpose of this study is to investigate the problem of whether or not the changes of AAIRs of individual tumors in time and space show a similar fitness to the equilibrium model of the law of mass action. The cancer risk data set of: a) 20 neoplasias in scope; b) 6 cancer registration areas in space; and c) 5 sequential investigations from early 1960's to mid 1980's in time, were subjected to the sequential regression analysis - a modification of the least square method. Results obtained are as follows: a) out of 20 tumors tested, all tumors other than 5 tumor types showed a good fitness (P<0.05) to the equilibrium model of the law of mass action in their risk changes in space. The 5 tumor types that failed to fit to the equilibrium model were male gall-bladder cancer, male breast cancer, male thyroid cancer, female liver cancer and female laryngeal cancer. They were all classified as the members of low-risk gender in the cancer family with sex discrimination of cancer risk. b) All tumors other than male thyroid cancer of Birmingham-England showed a good fitness to the equilibrium model of the law of mass action in their risk changes in time. c) It is argued that the good fitness to the equilibrium model of the law of mass action and the poor fitness to the equilibrium model can be taken each as indication of the predominant expression of oncogene activation and the emergence of intervention of tumor suppressor gene inactivation to the full expression of oncogene activation in the mathematical structure of the cancer risk data set. The significance of the above findings as the supporting evidence of the steroid criminal hypothesis of carcinogenesis as well as the pertinence of the least square method to the mathematical analysis of cancer risk are discussed in the light of historical development of science from early 19th century to late 20th century.
Int J Mol Med 1999 Apr
PMID:Statistical analysis of the age-adjusted incidence rates of human neoplasias: changes in time and space from early 1960's to mid 1980's with special reference to the steroid criminal hypothesis of carcinogenesis. 1008 20

Receptor-mediated gene delivery is an attractive method for gene transfer in vitro and shows promise for in vivo gene therapy applications. In the current study, we have selected the cytokine interleukin-2 (IL-2) gene to explore the feasibility of receptor-mediated gene transfer into human hepatocellular carcinoma HepG2 cells, using Epstein-Barr virus (EBV)-based vectors. We have developed a targeted DNA delivery system for the treatment of liver cancer by gene therapy. This system utilizes the hepatocyte-specific asialoglycoprotein receptor, which is uniquely expressed on liver cell membranes but not present on other cell types. Galactosylated histone, a ligand to the asialoglycoprotein receptors, was synthesized, and a new EBV-based expression vector bearing the human IL-2 cDNA was constructed and conjugated to the ligand through ionic interactions. The ligand/IL-2 DNA complex was able to bind specifically to cell-surface receptors on the target cell and, when incubated with HepG2 cells, resulted in elevated levels of IL-2 gene expression. These results indicate that therapeutic genes like IL-2 in ligand/DNA complex can be transferred into hepatoma cells via the hepatocyte receptor. This study constitutes an encouraging first step in the assessment of receptor-mediated gene transfer as a technique for gene therapy in liver cancer.
Int J Mol Med 1999 Jun
PMID:Receptor-mediated interleukin-2 gene transfer into human hepatoma cells. 1034 Dec 90


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