Biomedical subjects

Hans-Helge Seifert

Publications and source records attributed to Hans-Helge Seifert.

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

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↗

PubMed2002

Tumour class prediction and discovery by microarray-based DNA methylation analysis.

Aberrant DNA methylation of CpG sites is among the earliest and most frequent alterations in cancer. Several studies suggest that aberrant methylation occurs in a tumour type-specific manner. However, large-scale analysis of candidate genes has so far been hampered by the lack of high throughput assays for methylation detection. We have developed the first microarray-based technique which allows genome-wide assessment of selected CpG dinucleotides as well as quantification of methylation at each site. Several hundred CpG sites were screened in 76 samples from four different human tumour types and corresponding healthy controls. Discriminative CpG dinucleotides were identified for different tissue type distinctions and used to predict the tumour class of as yet unknown samples with high accuracy using machine learning techniques. Some CpG dinucleotides correlate with progression to malignancy, whereas others are methylated in a tissue-specific manner independent of malignancy. Our results demonstrate that genome-wide analysis of methylation patterns combined with supervised and unsupervised machine learning techniques constitute a powerful novel tool to classify human cancers.

Algorithms↗

PubMed2002

Genomewide DNA hypomethylation is associated with alterations on chromosome 8 in prostate carcinoma.

To elucidate the relationship between genomewide DNA hypomethylation and chromosome instability, 55 prostate carcinoma specimens were analyzed for extent of hypomethylation by Southern blot analysis of LINE-1 sequence methylation and for loss or gain of chromosomal material by comparative genomic hybridization. Seventeen (31%) tumors showed strong hypomethylation of DNA, whereas four (7%) displayed slight hypomethylation and the rest of the tumors normal-level methylation. Chromosomal aberrations were observed in 34 carcinomas. The most frequent chromosomal alterations were loss of 13q in 18 cases and aberrations in 8p (loss) or 8q (gain) in 16 cases. The presence of chromosomal loss or gain was significantly associated with the presence of strong hypomethylation. A striking correlation (P = 0.00001) was observed between aberrations on chromosome 8 and hypomethylation, whereas no association was seen between DNA hypomethylation and loss of 13q. The association between DNA hypomethylation and the presence of metastases was statistically significant (P = 0.044), and both chromosomal alterations and DNA hypomethylation tended to be more frequent in higher-stage tumors. In conclusion, the data indicate that hypomethylation is associated with chromosomal instability in prostate cancer. Specifically, a surprisingly strong association between alterations on chromosome 8 and genomewide hypomethylation was found. This association suggests that DNA hypomethylation and alterations in chromosome 8 may be mechanistically linked to each other in prostate carcinoma.

Aged↗

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↗

PubMedDate not supplied

Detection of circulating prostate cells during radical prostatectomy by standardized PSMA RT-PCR: association with positive lymph nodes and high malignant grade.

BACKGROUND: The purpose of this study was to establish a quantitative standardized RT-PCR for the detection of Prostate Specific Membrane Antigen (PSMA)-expressing circulating cells and to evaluate clinical relevance in patients undergoing radical retropubic prostatectomy (RRP) for clinically localized prostate cancer (PCa). MATERIALS AND METHODS: An external standard molecule (PSMA MIMIC) was constructed for standardization of PSMA RT-PCR reactions. It has the same sequence as endogenous PSMA, except for a central 85 bp deletion, allowing the amplification of both targets simultaneously with nearly the same amplification characteristics as in a nested PCR. PSMA RT-PCR was performed from peripheral blood samples of 73 patients with clinically localized PCa, 4 with metastatic PCa, 27 with benign prostatic hyperplasia (BPH) and 27 controls. Pre, intra- and postoperative blood samples were tested for circulating PSMA expressing cells in 54 out of 73 patients with clinically localized PCa. We also tested intraoperative blood samples of 19 BPH patients treated by transurethral or open surgery. RESULTS: Endogenous PSMA signals from PCa patients varied between 850 and 9900 transcript molecules, corresponding to 2-20 PSMA-expressing cells/ml blood. Standardized RT-PCR using the PSMA MIMIC molecule revealed a significant decrease of "false-positives" in cancer-free controls (p = 0.004). Controls could clearly be distinguished from prostate cancer patients based on PSMA PCR positivity (p = 0.003). Thirty-two % of patients with localized prostate cancer, 11% of BPH patients and 7% of healthy controls were positive in standardized assays compared to 48%, 30% and 27% without PSMA MIMIC, respectively. Preoperatively, a correlation with tumor stage (p = 0.030), grade (p = 0.035) and Gleason Score (p = 0.03) could be demonstrated in clinically localized PCa patients. Dissemination of prostate cells during surgery occurred in 32% of the RRPs and 21% of BPH patients. Positive PCR signals from intraoperative blood samples correlated with positive lymph node status (p = 0.007) and tumor grade (p = 0.005). Postoperative positive results correlated with grade (p = 0.012) and Gleason Score (p = 0.035). CONCLUSION: Counseling the patient with clinically localized prostate cancer can be challenging. Surgery may be, in retrospect, inappropriate in a number of patients due to preoperative understaging. This newly constructed external standard allows quantitative detection of circulating prostate cells, and therefore may open new perspectives for PSMA RT-PCR techniques as diagnostic assays and tools for post-therapeutic follow-up.

Antigens, Surface↗