Biomedical subjects

Inko Nimmrich

Publications and source records attributed to Inko Nimmrich.

6 recordsLinked to original sources

PubMed2005

Association of DNA methylation of phosphoserine aminotransferase with response to endocrine therapy in patients with recurrent breast cancer.

To understand the biological basis of resistance to endocrine therapy is of utmost importance in patients with steroid hormone receptor-positive breast cancer. Not only will this allow us prediction of therapy success, it may also lead to novel therapies for patients resistant to current endocrine therapy. DNA methylation in the promoter regions of genes is a prominent epigenetic gene silencing mechanism that contributes to breast cancer biology. In the current study, we investigated whether promoter DNA methylation could be associated with resistance to endocrine therapy in patients with recurrent breast cancer. Using a microarray-based technology, the promoter DNA methylation status of 117 candidate genes was studied in a cohort of 200 steroid hormone receptor-positive tumors of patients who received the antiestrogen tamoxifen as first-line treatment for recurrent breast cancer. Of the genes analyzed, the promoter DNA methylation status of 10 genes was significantly associated with clinical outcome of tamoxifen therapy. The association of the promoter hypermethylation of the strongest marker, phosphoserine aminotransferase (PSAT1) with favorable clinical outcome was confirmed by an independent quantitative DNA methylation detection method. Furthermore, the extent of DNA methylation of PSAT1 was inversely associated with its expression at the mRNA level. Finally, also at the mRNA level, PSAT1 was a predictor of tamoxifen therapy response. Concluding, our work indicates that promoter hypermethylation and mRNA expression of PSAT1 are indicators of response to tamoxifen-based endocrine therapy in steroid hormone receptor-positive patients with recurrent breast cancer.

Adult↗

PubMed2005

Differential DNA methylation of gene promoters in small B-cell lymphomas.

Improved care of patients with small B-cell lymphomas (SBCLs) is likely to result from the ongoing discovery of molecular markers that better define these malignant neoplasms. We identified multiple gene loci whose DNA methylation patterns differed between 3 types of SBCL: B-cell chronic lymphocytic leukemia/small lymphocytic lymphoma, mantle cell lymphoma, and grades I and II follicular lymphoma. This analysis was performed using an oligonucleotide microarray that allowed determination of the DNA methylation status of 156 loci in 38 genes. Combined bisulfite restriction analysis and methylation-specific polymerase chain reaction were used to validate the differential methylation of 6 of these genes. By using non-Hodgkin lymphoma cell lines as models, these genes were examined further for methylation and gene expression relationships. This study illustrates nonrandom epigenetic alterations in SBCLs that seem to preferentially involve lymphomas of germinal center derivation.

DNA Methylation↗

PubMed2004

Distinction of acute lymphoblastic leukemia from acute myeloid leukemia through microarray-based DNA methylation analysis.

Patterns of DNA methylation are substantially altered in malignancies compared to normal tissue, with both genome-wide hypomethylation and regional increase of cytosine methylation at dinucleotides of cytosine and guanine, i.e., CpG dinucleotides. While genome-wide hypomethylation renders chromosomes instable, hypermethylation of CpGs in promoter regions is generally associated with transcriptional silencing, e.g., of tumor suppressor genes. To investigate whether disease-specific methylation profiles exist for different entities of acute leukemia, a microarray-based DNA methylation analysis simultaneously assessing 249 CpG dinucleotides originating from 57 genes was employed. Hereby, samples from precursor B-cell acute lymphoblastic leukemia (ALL) could be distinguished from cases of acute myeloid leukemia by virtue of N33, EGR4, CDC2, CCND2, or MOS hypermethylation in ALL.

Acute Disease↗

PubMed2003

The androgen receptor gene is preferentially hypermethylated in follicular non-Hodgkin's lymphomas.

This investigation examined promoter DNA methylation of the androgen receptor (AR) gene in non-Hodgkin's lymphoma (NHL) representing different stages of B-cell differentiation. Steroid hormones are important endocrine messengers with a broad range of physiological functions, including regulation of B-cell lymphopoiesis. Some of these effects are mediated via specific receptors such as AR that can act as a ligand-dependent transcription factor for other genes. DNA was isolated from 76 NHL specimens representing pregerminal center, germinal center, and postgerminal center states of differentiation. Initial methylation data were obtained from oligonucleotide microarrays and was confirmed and extended using methylation-specific PCR. Methylation of the AR gene promoter was present in a nonrandom pattern. Those tumors derived from pregerminal center or postgerminal center stages showed virtually no methylation and expressed AR mRNA. Cases of germinal center origin, mainly follicular lymphomas and some diffuse large B-cell lymphomas, showed hypermethylation. Studies with NHL cell lines revealed that demethylation or reversal of histone deacetylation partially restored AR expression but reversal of both simultaneously provided a synergistic release from suppression. Promoter methylation of AR occurs in a differentiation stage-selective manner; those cases arising in the germinal center are preferentially methylated. Full re-expression of AR requires both demethylation and reacetylation, a finding that may affect treatment decisions.

Cell Line, Tumor↗

PubMed2003

Oligonucleotide-based microarray for DNA methylation analysis: principles and applications.

Gene silencing via promoter CpG island hypermethylation offers tumor cells growth advantages. This epigenetic event is pharmacologically reversible, and uncovering a unique set of methylation-silenced genes in tumor cells can bring a new avenue to cancer treatment. However, high-throughput tools capable of surveying the methylation status of multiple gene promoters are needed for this discovery process. Herein we describe an oligonucleotide-based microarray technique that is both versatile and sensitive in revealing hypermethylation in defined regions of the genome. DNA samples are bisulfite-treated and PCR-amplified to distinguish CpG dinucleotides that are methylated from those that are not. Fluorescently labeled PCR products are hybridized to arrayed oligonucleotides that can discriminate between methylated and unmethylated alleles in regions of interest. Using this technique, two clinical subtypes of non-Hodgkin's lymphomas, mantle cell lymphoma, and grades I/II follicular lymphoma, were further separated based on the differential methylation profiles of several gene promoters. Work is underway in our laboratory to extend the interrogation power of this microarray system in multiple candidate genes. This novel tool, therefore, holds promise to monitor the outcome of various epigenetic therapies on cancer patients.

CpG Islands↗

PubMed2002

Murine Nr4a1 and Herpud1 are up-regulated by Wnt-1, but the homologous human genes are independent from beta-catenin activation.

The Wnt signal transduction pathway regulates morphogenesis and mitogenesis of cells in multicellular organisms. A major downstream consequence of Wnt-1 signalling is the activation of beta-catenin/T-cell factor (TCF)-mediated transcription. We compared Wnt-1-transformed murine mammary epithelial cells with control cells by subtractive hybridization. We found the two genes Nr4a1 and Herpud1 to be overexpressed in Wnt-1-transformed cells. Remarkably, the transcription levels of the two homologous human genes NR4A1 and HERPUD1 are neither activated in cells with activated beta-catenin/TCF-mediated transcription nor can be induced by beta-catenin transfection. These results indicate different regulation mechanisms of the two genes in murine and human cells.

Animals↗