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Biomedical subjects

K G Wiman

Publications and source records attributed to K G Wiman.

62 records · Page 4Linked to original sources
PubMed1992

Cell type and differentiation dependent heterogeneity in retinoblastoma protein expression in SCID mouse fetuses.

The expression pattern of retinoblastoma (Rb) protein has been studied at the single cell level in frozen sections of 16- to 18-day-old SCID mouse fetuses by immunofluorescence staining with mouse monoclonal and rabbit polyclonal antibodies, using conventional epifluorescence and confocal laser scanning microscopy. The nuclei of megakaryocytes, hemopoietic islands of the fetal liver, osteo-, amelo-, and odontoblasts, and skeletal muscle were strongly stained. There was no detectable Rb staining in the basal cell layers of stratified squamous epithelia, but the differentiating, more superficial layers were positive. Intestinal crypts were negative, whereas the villi were positive. In the retina, Rb protein was detectable in the inner ganglion layer but not in the outer neuroblastic layer. In the central nervous system, Rb protein was present in neurons and glia cells as well. The nuclei in the collecting tubules of the kidney, the pancreas, and the adrenal cortex were Rb positive. Analysis of the differentiation dependent expression of Rb protein in relation to the prospective life cycle of the cells in which it appears may pave the way toward an understanding of the tissue specific oncogenic effect of Rb loss in families with hereditary retinoblastoma.

Animals↗
PubMed1991

Mutant p53 detected in a majority of Burkitt lymphoma cell lines by monoclonal antibody PAb240.

The status of the p53 gene in lymphoblastoid cell lines (LCLs) and Burkitt lymphoma cell lines (BLs) was investigated. Southern blot analysis demonstrated that no major deletions or rearrangements had occurred in the p53 gene in any of the cell lines. The p53 protein was examined by immunoprecipitation using two monoclonal anti-p53 antibodies. PAb1801 recognizes both wild-type and mutant p53. PAb240 reacts exclusively with mutant p53. Fourteen LCLs reacted with PAb1801, but not with PAb240, suggesting that none of them expressed mutant p53. However, one LCL had mutant p53. This LCL differs from other LCLs in that it grows to higher cell densities and has a higher agarose clonability. All BLs expressed p53. Out of 15 BLs, nine (60%) carried mutant p53, as indicated by their reactivity with PAb240. Among the nine BLs with mutant p53, eight Epstein-Barr virus (EBV)-positive. Three out of the six BLs with wild-type p53 were EBV-positive. Multiple EBV-converted sublines all exhibited the same p53 status as the parental line. Our results indicate that the p53 gene is mutated in a majority of Burkitt lymphoma cell lines (BLs), and suggest that p53 mutation contributes to the malignant phenotype of these cell lines.

Antibodies, Monoclonal↗
PubMed1991

Subcellular localization of the retinoblastoma protein.

The subcellular localization of the retinoblastoma (RB) protein has been studied in primate cell lines by immunofluorescence staining using different monoclonal and polyclonal antibodies. The protein appeared as granules of heterogeneous size over the interphase nuclei. Computer assisted digital overlap analysis indicated that it was predominantly localized in euchromatic areas with low DNA density. The largest RB positive grains lined up on the heterochromatin/euchromatin boundary. During mitosis, the RB protein dissociated from the condensing chromosomes. It was dispersed throughout the cytoplasm during metaphase and anaphase, and it reassociated with the decondensing chromatin during telophase. A new monoclonal antibody, designated aRB1C1, was raised against a bacterial TrpE/human retinoblastoma protein. It specifically recognized the nonphosphorylated and differentially phosphorylated forms of the RB protein in immunoprecipitation experiments. A collection of RB expressing cell lines gave a positive staining reaction with the antibody, whereas the RB negative Weri-RB-27 retinoblastoma and OHS osteosarcoma cells failed to react. Wild-type RB complementary DNA was introduced into Weri-RB-27 by retrovirus mediated gene transfer. Similar experiments were performed with the DU145 prostatic carcinoma cell line that expresses a mutant RB protein. Reconstituted cells of both lines expressed the normal size RB protein and gave a positive immunofluorescence reaction with the aRB1C1 and other anti-RB antibodies. The new monoclonal antibody, however, showed cell type dependent differences of the staining pattern compared to other anti-RB antibodies, suggesting differentiation dependent accessibility to its epitope.

Antibodies, Monoclonal↗
PubMed1984

Activation of a translocated c-myc gene: role of structural alterations in the upstream region.

The translocated c-myc gene in AW-Ramos, a Burkitt lymphoma cell line carrying the 8;14 translocation, is expressed at 2- to 5-fold higher levels than c-myc in lymphoblastoid cell lines. The translocation event has joined c-myc to the IgM switch region. As a consequence, a recently identified immunoglobulin transcriptional enhancer element is not linked to the translocated c-myc gene. Chromosomal recombination occurs approximately equal to 340 nucleotides upstream of the c-myc 5' cap site, leaving all three c-myc exons intact. The nucleotide sequences of the two coding exons in the translocated c-myc gene are identical to those of the normal c-myc gene. Nucleotide sequence analyses of the first, noncoding c-myc exon and of the region between this exon and the chromosomal recombination point reveal two single-base differences from normal c-myc. Our data indicate that altered expression rather than an altered gene product is responsible for c-myc activation in AW-Ramos cells and that this is a result of either loss of regulatory sequences located greater than 340 nucleotides upstream of c-myc or disruption of normal c-myc regulation by one or both base substitutions. Alternatively, unidentified enhancer-like sequences in the Ig locus may alter the expression of c-myc.

Base Sequence↗
PubMedDate not supplied

Inactivation of Myc-induced p53-dependent apoptosis in human tumors.

The Myc family of oncoproteins promote cell growth and are frequently overexpressed in human tumors. However, Myc can also trigger cell death by apoptosis. This is at least in part mediated via the ARF-p53 pathway. Myc activation leads to a selection for inactivation of ARF or p53, allowing cell survival and tumor progression. Restoration of p53-dependent apoptosis by various means is an attractive approach for new cancer therapy.

Apoptosis↗
PubMedDate not supplied

Induction of the human ARF protein by serum starvation.

The ARF protein encoded by the alternative transcript of the INK4a gene inhibits cell growth by stabilization of p53. ARF is induced by activated oncogenes sucll as c-myc, E1A and E2F-1. We show here that ARF protein expression is also induced by serum deprivation in the human tumor cell line MDA-MB-157 and in the SV40 large T-immortalized keratinocyte line Rhek. This increase of expression was reversed by the addition of serum. ARF mRNA levels also increased after serum starvation, suggesting that ARF upregulation is mediated, at least in part, by increased transcription and/or mRNA stability. These results indicate that ARF responds not only to oncogenic hyper-proliferative signals but also to suboptimal growth conditions.

Culture Media, Serum-Free↗
PubMedDate not supplied

Involvement of aberrant p53 expression and human papillomavirus in carcinoma of the head, neck and esophagus.

Biopsies from 34 patients with cancer of the head, neck or esophagus, 2 laryngeal papillomas, and 2 normal tonsils were analysed for human papillomavirus (HPV), Epstein Barr virus (EBV) genomes and mutated or elevated levels of p53. In 4 biopsies p53 was also analysed by DNA sequencing. HPV type 31 was found in one laryngeal cancer with normal p53 and HPV type 16 in two tonsil cancers with aberrant p53 expression. EBV was detected by PCR in 11 biopsies, but in situ hybridisation and immunohistochemistry, did not confirm this finding. Aberrant p53 expression was observed in approximately half of the tumours. These results support the involvement of both aberrant p53 expression and HPV in the aetiology of squamous cell carcinoma of the head and neck.

Base Sequence↗