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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A number of glycoproteins are regulators of the complement cascade and prevent damage to cells by inappropriate activation of complement. In humans, all of them are encoded by a multigene family on chromosome I and share a characteristic structural feature, the short consensus repeats of about 61 amino acids with a constant framework of cysteine, proline, and tryptophan. We found the gene for glycoproteins of analogous structure in herpesvirus saimiri, a T-lymphotropic tumor virus of New World primates. Unspliced transcripts code for a membrane-bound 65- to 75-kDa virion surface component, while spliced mRNA instructs a secreted glycoprotein of 47 to 53 kDa. Expression of complement control proteins suggests a novel mechanism of counteracting host immune defense to prevent elimination of a virus that is capable of persisting in circulating lymphocytes.
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PMID:New member of the multigene family of complement control proteins in herpesvirus saimiri. 131 92

We investigated whether replication-competent pre-C/C defective mutants of hepatitis B virus (HBV) are detectable in primary human hepatocellular carcinoma (HCC) tissues from patients of a geographic area endemic for such mutants. DNAs extracted from formalin-fixed paraffin-embedded HCC samples were checked for the presence of specific HBV DNA sequences using the polymerase chain reaction (PCR). Amplified pre-C regions from nine HCC samples were directly sequenced as were samples of nontumoral liver tissues from five of these patients. The data show that hypervariable distal pre-C sequences were present in all nine HCC samples; this high variability was dependent on point mutations, which led to amino acid substitutions in nearly all cases. Interestingly, seven of the nine HBV DNA-positive samples from HCC tissues (but not samples from peritumoral liver tissue) showed mutations leading to amino acid substitution at the level of a distal cysteine residue. No mutation generating a translationally defective pre-C/C region was detectable in the tumor samples. Otherwise, in four of the six nontumoral liver tissues available from the same patients, a pre-C sequence with an in-frame TAG stop codon was detectable, although in three cases as a component of mixed population.
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PMID:Sequence analysis of the hepatitis B virus pre-C region in hepatocellular carcinoma [HCC] and nontumoral liver tissues from HCC patients. 131 86

A proposed Wilms tumor gene, WT1, which encodes a zinc finger protein, has previously been isolated from human chromosome 11p13. Chemical mismatch cleavage analysis was used to identify point mutations in the zinc finger region of this gene in a series of 32 Wilms tumors. Two exonic single base changes were detected. In zinc finger 3 of a bilateral Wilms tumor patient, a constitutional de novo C----T base change was found changing an arginine to a stop codon. One tumor from this patient showed allele loss leading to 11p hemizygosity of the abnormal allele. In zinc finger 2 of a sporadic Wilms tumor patient, a C----T base change resulted in an arginine to cysteine amino acid change. To our knowledge, a WT1 gene missense mutation has not been detected previously in a Wilms tumor. By comparison with a recent NMR and x-ray crystallographic analysis of an analogous zinc finger gene, early growth response gene 1 (EGR1), this amino acid change in WT1 occurs at a residue predicted to be critical for DNA binding capacity and site specificity. The detection of one nonsense point mutation and one missense WT1 gene point mutation adds to the accumulating evidence implicating this gene in a proportion of Wilms tumor patients.
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PMID:Zinc finger point mutations within the WT1 gene in Wilms tumor patients. 131 72

The three ras genes code for proteins with a putative role in cellular signal transduction. They belong to a larger family of small guanosine-triphosphate (GTP)-binding proteins. The ras proteins acquire transforming activity when amino acids are substituted at one of a few specific sites, as a result of a point mutation in the gene. In about one third of adenocarcinomas of the lung, a K-ras mutation is present in codon 12 of the gene. Patients with early stages of K-ras mutation-positive tumors have a very unfavorable prognosis, even if apparently radical resection of the tumor has taken place. K-ras mutations are very rare among nonsmokers, and it is reasonable to assume that carcinogens in tobacco smoke directly cause the mutation. The types of ras mutations found in lung cancer are different from those in gastrointestinal malignancies. Colon cancer is mainly associated with mutations leading to substitution of the normal glycine at amino acid position 12 of K-ras by either valine or aspartic acid, and mutations in N-ras are not exceptional. In contrast, the predominant mutation in lung cancer leads to substitution of cysteine in codon 12. Several other members of the ras gene superfamily are also expressed in human lung cancer, but a possible relationship with lung tumorigenesis remains to be established.
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PMID:The ras gene family in human non-small-cell lung cancer. 132 34

A missense mutation at cysteine 706, resulting in a retinoblastoma (RB) protein defective in phosphorylation and oncoprotein binding, has been isolated from a human tumor cell line. Since this residue is conserved in murine RB and in the related p107 protein, we studied the activity of in vitro mutants flanking this position. These experiments demonstrated that the thiol atom at codon 706 does not possess intrinsic functional activity as small polar or nonpolar residues could substitute at either codons 706 or 707, while bulkier R-group changes in these positions interfered with in vitro oncoprotein binding or in vivo protein phosphorylation. A series of missense mutants in an adjacent leucine repeat domain also demonstrated a loss of oncoprotein binding that was proportional to the magnitude of amino acid substitutions. To determine whether the cysteine 706 --> phenylalanine RB mutant retained any protein binding activity, we examined its ability to precipitate MYC, which was recently identified as a potential RB-associated protein. These experiments demonstrated that the mutant RB product is capable of binding in vitro to c-myc and L-myc proteins with comparable affinity as wild-type RB. These findings raise questions about the functional role of the RB:MYC interactions and emphasize important differences in the binding patterns between MYC and the other RB-associated proteins.
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PMID:Functional analysis at the Cys706 residue of the retinoblastoma protein. 133 91

The amino- and carboxyl-terminal globular domains of type VI collagen are composed of several homologous modules similar to the type A collagen-binding modules present in von Willebrand factor. The human alpha 3(VI) chain that contributes most of the amino-terminal globule appears heterogeneous in size as a result of alternative splicing of two exons (Stokes D. G., Saitta, B., Timpl, R., and Chu, M.-L. (1991) J. Biol. Chem. 266, 8626-8633). In the present study, we report a further characterization of the 5'-end of the gene of the human alpha 3(VI) chain and show that transcription initiates at multiple sites. Southern blotting and DNA sequencing indicate that there is an additional type A exon (A9/N10) at about 1.8 kilobase pairs downstream of the exon coding for the signal peptide. The open reading frame of this additional exon reveals 1 cysteine and three potential N-glycosylation sites. Polymerase chain reaction, Northern blotting, and RNase protection assays demonstrate that exon A9/N10 is subject to alternative splicing in normal and tumor cell lines and that this generates more protein variants of the alpha 3(VI) chain than expected before. A comparison with the corresponding amino-terminal globule of the chicken alpha 3(VI) chain shows the presence of 1 additional cysteine in this portion of the molecule and suggests that human type VI collagen has more possibilities for structural and functional variations compared to chicken type VI collagen.
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PMID:The human type VI collagen gene. mRNA and protein variants of the alpha 3 chain generated by alternative splicing of an additional 5-end exon. 133 40

The DNA from a pituitary adenoma of a patient with multiple endocrine neoplasia (MEN) type 1 was analyzed to detect a point mutation of the Gs alpha gene (gsp) by the PCR direct-sequencing method. The patient had galactorrhea, amenorrhea and acromegalic features. Hormonal examination revealed high serum levels of PRL and GH. The tumor was histologically diagnosed as a mixed GH cell-PRL cell adenoma in which GH and PRL were produced by different cells. Sequence analysis of the DNAs extracted from paraffin sections of pituitary, parathyroid, and pancreas tumors demonstrated the substitution of thymidine for cytidine in codon 201 of the Gs alpha gene that resulted in replacement of arginine (CGT) with cysteine (TGT) only in the pituitary adenoma, but not in the parathyroid and pancreas tumors. These results suggest that a pituitary specific point mutational activation of the Gs alpha gene may be involved in the development of the pituitary adenoma in this patient.
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PMID:A pituitary specific point mutation of codon 201 of the Gs alpha gene in a pituitary adenoma of a patient with multiple endocrine neoplasia (MEN) type 1. 135 1

In this present study, we report the mutation of the p53 gene in vivo in human primary carcinomas of cervix and cervical intraepithelial neoplasia (CIN). The association of the HPV subtypes with the tumors was determined by multiplex primer polymerase chain reaction (PCR) amplification. The mutation of the p53 gene was detected using PCR amplification of the p53 exons followed by SSCP (single strand conformation polymorphism) and DNA sequencing analysis. The p53 mutation was detected in two out of two HPV-33 positive carcinomas but was absent in the HPV-16/-18 positive carcinomas (0 out of 8 cases). The p53 mutation was also detected in one out of four HPV-negative cervical carcinomas. No mutation of the p53 gene was detected in the CIN specimens (0 out of 7 cases). The two mutations in the HPV-33 associated cervical carcinoma were detected at codon 273 (CGT to TGT; arginine to cysteine) and intron 5 (24 base pair downstream of the 3' end of exon 5). The p53 mutation at codon 273 has been previously reported in one of the HPV-negative cervical carcinoma cell line (C33A). Our results indicate that mutation of the p53 gene is not a common event in human cervical cancers (3/14), and may be related to the infection of HPV-16/18 in the tumor. However, mutation of the p53 gene was detected in cervical carcinomas associated with HPV-33 and may be an important genetic event in this subgroup of carcinomas.
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PMID:Presence of p53 mutation in human cervical carcinomas associated with HPV-33 infection. 136 12

Many clinical uses of antibodies will require large quantities of fragments which are bivalent and humanized. We therefore attempted to generate humanized F(ab')2 fragments by secretion from E. coli. Titers of 1-2 g l-1 of soluble and functional Fab' fragments have been routinely achieved as judged by antigen-binding ELISA. Surprisingly, this high expression level of Fab' in the periplasmic space of E. coli does not drive dimerization. However, we have developed a protocol to directly and efficiently recover Fab' with the single hinge cysteine in the free thiol state, allowing F(ab')2 formation by chemically-directed coupling in vitro. The E. coli derived humanized F(ab')2 fragment is indistinguishable from F(ab')2 derived from limited proteolysis of intact antibody in its binding affinity for the antigen, p185HER2, and anti-proliferative activity against the human breast tumor cell line, SK-BR-3, which over-expresses p185HER2. This system makes E. coli expression of bivalent antibody fragments for human therapy (or other uses) practical.
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PMID:High level Escherichia coli expression and production of a bivalent humanized antibody fragment. 136 28

Herpesvirus saimiri (HSV) is a T-lymphotropic tumor virus that causes fulminant lymphomas and leukemias in various New World primates other than its natural host, the squirrel monkey (Saimiri sciureus). In the course of completing the nucleotide sequence of its genome, we identified an open reading frame of 363 nucleotides, designated HVS-15, that has no detectable homology to any other viral sequences to date. HVS-15 encodes a 121-amino-acid protein which shows significant similarities to human CD59, a phosphatidyl-inositol-glycan-anchored glycoprotein involved in T-cell activation and restriction of complement-mediated lysis. The predicted HVS-15 gene product is more similar to human CD59 than to the related murine Ly-6 antigens. A nucleotide sequence identity of 64% was found between HVS-15 and the CD59 reading frame, and a 48% identity exists between the corresponding protein sequences. The comparison of the amino acid sequences revealed a number of conserved structural features such as a similar pattern of hydrophobic termini and an identical cysteine skeleton.
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PMID:Herpesvirus saimiri has a gene specifying a homologue of the cellular membrane glycoprotein CD59. 138 44


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