Biomedical subjects

Christine Steinhoff

Publications and source records attributed to Christine Steinhoff.

6 recordsLinked to original sources

PubMed2003

Decrease of DNA methyltransferase 1 expression relative to cell proliferation in transitional cell carcinoma.

In many common cancers such as transitional cell carcinoma (TCC), specific genes are hypermethylated, whereas overall DNA methylation is diminished. Genome-wide DNA hypomethylation mostly affects repetitive sequences such as LINE-1 retrotransposons. Methylation of these sequences depends on adequate expression of DNA methyltransferase I (DNMT1) during DNA replication. Therefore, DNMT1 expression relative to proliferation was investigated in TCC cell lines and tissue as well as in renal carcinoma (RCC) cell lines, which also display hypomethylation, as indicated by decreased LINE-1 methylation. Cultured normal uroepithelial cells or normal bladder tissue served as controls. In all tumor cell lines, DNMT1 mRNA as well as protein was decreased relative to the DNA replication factor PCNA, and DNA hypomethylation was present. However, the extents of hypomethylation and DNMT1 downregulation did not correlate. Reporter gene assays showed that the differences in DNMT1 expression between normal and tumor cells were not established at the level of DNMT1 promoter regulation. Diminished DNMT1:PCNA mRNA ratios were also found in 28/45 TCC tissues but did not correlate with the extent of DNA hypomethylation. In addition, expression of the presumed de novo methyltransferases DNMT3A and DNMT3B mRNAs was investigated. DNMT3B overexpression was observed in about half of all high-stage TCC (DNMT3B vs. tumor stage, chi(2): p = 0.03), whereas overexpression of DNMT3A was rarer and less pronounced. Expression of DNMT3A and DNMT3B in most RCC lines was higher than in TCC lines. Our data indicate that DNMT1 expression does not increase adequately with cell proliferation in bladder cancer. This relative downregulation probably contributes to hypomethylation of repetitive DNA but does not determine its extent alone.

Aged↗

PubMed2003

Gene expression profile of mouse bone marrow stromal cells determined by cDNA microarray analysis.

Bone marrow stromal cells (BMSC) have gained increased attention because of their multipotency and adult stem cell character. They have been shown to differentiate into other cell types of the mesenchymal lineage and also into non-mesenchymal cells. The exact identity of the original cells, which are isolated from bone marrow by their selective adherence to plastic, remains unknown to date. We have established and characterized mouse BMSC cultures and analyzed three independent samples by cDNA microarrays. The expression profile was compared with two previous expression studies of human BMSC and revealed a high degree of concordance between different techniques and species. To gain clues about the positional context and biology of the isolated cells within the bone marrow stroma, we searched our data for genes that encode proteins of the extracellular matrix, cell adhesion proteins, cytoskeletal proteins and cytokines/cytokine receptors. This analysis revealed a close association of BMSC with vascular cells and indicated that BMSC resemble pericytes.

Animals↗

PubMed2003

Activities of MAP-kinase pathways in normal uroepithelial cells and urothelial carcinoma cell lines.

It is often assumed that MAPK pathways drive proliferation of normal uroepithelial (UEC) and urothelial carcinoma (TCC) cells. To check this assumption, activities and inducibilities of promoters containing serum-response elements (SRE) or AP-1 binding sites were investigated in cultured UEC and seven TCC lines. Reporter plasmids dependent on SRE or AP-1 sites were highly active in UEC, but significantly less so in TCC lines. Reporter activity in TCC lines could be induced by constitutively active MEKK4 or TPA. Accordingly, phosphorylation of the MAPK pathway components MEK, ERK, and ELK1 was most pronounced in UEC and lower in TCC lines. MAPK-dependent promoter activities and bromodeoxyuridine incorporation decreased in UEC upon withdrawal of growth factors, but less so in TCC lines, in which serum diminution increased apoptosis. Likewise, E2F-dependent promoters responded to growth factors in UEC, but were more serum-independent in the TCC lines, which lack either RB1 or p16(INK4A). MEK inhibitors inhibited BrdU incorporation in UEC more strongly than in TCC lines. Thus, proliferation of normal uroepithelial cells is indeed associated with activation of MAPK pathways. However, autonomous proliferation of TCC lines--unexpectedly--appears much less dependent on MAPK activation and may rather be promoted by defects in cell cycle regulation.

Binding Sites↗

PubMed2003

Using hidden Markov models to analyze gene expression time course data.

MOTIVATION: Cellular processes cause changes over time. Observing and measuring those changes over time allows insights into the how and why of regulation. The experimental platform for doing the appropriate large-scale experiments to obtain time-courses of expression levels is provided by microarray technology. However, the proper way of analyzing the resulting time course data is still very much an issue under investigation. The inherent time dependencies in the data suggest that clustering techniques which reflect those dependencies yield improved performance. RESULTS: We propose to use Hidden Markov Models (HMMs) to account for the horizontal dependencies along the time axis in time course data and to cope with the prevalent errors and missing values. The HMMs are used within a model-based clustering framework. We are given a number of clusters, each represented by one Hidden Markov Model from a finite collection encompassing typical qualitative behavior. Then, our method finds in an iterative procedure cluster models and an assignment of data points to these models that maximizes the joint likelihood of clustering and models. Partially supervised learning--adding groups of labeled data to the initial collection of clusters--is supported. A graphical user interface allows querying an expression profile dataset for time course similar to a prototype graphically defined as a sequence of levels and durations. We also propose a heuristic approach to automate determination of the number of clusters. We evaluate the method on published yeast cell cycle and fibroblasts serum response datasets, and compare them, with favorable results, to the autoregressive curves method.

Algorithms↗

PubMed2003

Effect of routine repeat transurethral resection for superficial bladder cancer: a long-term observational study.

PURPOSE: We determined the long-term outcome in patients with superficial bladder cancer (Ta and T1) undergoing routine second transurethral bladder tumor resection (ReTURB) in regard to recurrence and progression. MATERIALS AND METHODS: We performed an inception cohort study of 124 consecutive patients with superficial bladder cancer undergoing transurethral resection and routine ReTURB (83) between November 1993 and October 1995 at a German university hospital. Immediately after transurethral resection all lesions were documented on a designed bladder map. ReTURB of the scar from initial resection and other suspicious lesions was performed at a mean of 7 weeks. Patients were followed until recurrence or death, or a minimum of 5 years. RESULTS: Residual tumor was found in 33% of all ReTURB cases, including 27% of Ta and 53% of T1 disease, and in 81% at the initial resection site. Five of the 83 patients underwent radical cystectomy due to ReTURB findings. The estimated risk of recurrence after years 1 to 3 was 18%, 29% and 32%, respectively. After 5 years 63% of the patients undergoing ReTURB were still disease-free (mean recurrence-free survival 62 months, median 87). Progression to muscle invasive disease was observed in only 2 patients (3%) after a mean observation of 61 months. CONCLUSIONS: These data suggest a favorable outcome regarding recurrence and progression in patients with superficial bladder cancer who undergo ReTURB. ReTURB is suggested at least in those at high risk when bladder preservation is intended.

Adult↗

PubMed2002

Activity of E2F-dependent promoters in bladder carcinoma cells and their use for tumour-specific targeting of p53-induced apoptosis.

Inactivation of P53 and RB functions are crucial changes in bladder cancer (TCC). High-level re-expression of P53 elicits apoptosis in TCC cell lines, but also--as shown here--in normal uroepithelial cells. Compromised RB function is thought to cause increased activity of E2F-dependent promoters in carcinoma cells. Indeed, several, but not all E2F-dependent promoters were stronger in TCC lines than in normal cells, with the highest activities in cell lines lacking RB rather than p16INK4A. Re-expression of p53 from an E2F-dependent promoter suppressed clone formation and induced apoptosis in TCC lines as efficiently as expression from the stronger RSV-LTR or LINE-1 promoters. In normal cells, p53 expression from an E2F-dependent promoter was tolerated, whereas expression from both stronger promoters was lethal. Thus, specific E2F-dependent promoters allow adjustment of p53 expression to selectively induce apoptosis in TCC vs. normal uroepithelial cells. This approach could be useful in targeting apoptosis to TCC and other carcinomas lacking p53 and RB function.

Apoptosis↗