Biomedical subjects

A C Lambrechts

Publications and source records attributed to A C Lambrechts.

11 recordsLinked to original sources

PubMed1999

Comparison of immunocytochemistry, reverse transcriptase polymerase chain reaction, and nucleic acid sequence-based amplification for the detection of circulating breast cancer cells.

Detection of tumor cells in blood and bone marrow is increasingly used for the staging of patients with breast cancer and to evaluate the presence of tumor cells in peripheral blood progenitor cell collections to be used after high-dose therapy. We evaluated the sensitivity and specificity of three different methods for detection of tumor cells among non-tumor tissue. An immunocytochemical assay using antibodies directed against epitopes of the cytokeratin-19 (CK19) protein and two RNA-based methods: reverse transcriptase polymerase chain reaction (RT-PCR) and Nucleic Acid Sequence-Based Amplification (NASBA) for the same target gene were tested. With all the three methods, false-positive results were observed when peripheral blood mononuclear cells (PBMC) of healthy volunteers were tested. There was no concordance between the RNA-based assays and the immunocytochemical assay. The false-positive results in the RNA-based assays may be due to 'illegitimate expression' of epithelial genes in normal PBMC. The false-positive results in the immunocytochemical assay resulted from background staining of monocytes and granulocytes. This study demonstrates that CK19 is not a suitable target to detect the presence of breast tumor tells in PBMC. To reliably detect circulating tumor cells with RNA methods, the selection of suitable target genes is required, which are highly expressed in tumors but not at all in normal cells of blood and bone marrow. Genes with such characteristics may be identifiable with novel differential display techniques.

Breast Neoplasms↗

PubMed1998

The detection of minimal numbers of contaminating epithelial tumor cells in blood or bone marrow: use, limitations and future of RNA-based methods.

BACKGROUND: Many solid tumors commonly metastasize to the bone marrow and the presence of tumor cells in the bone marrow is associated with a poor prognosis. Detection of tumor cells in the bone marrow has been reported to be important to determine the prognosis of newly diagnosed patients and may be helpful in deciding whether or not systemic treatment is indicated. PATIENTS AND METHODS: The majority of the studies focus on the detection of tumor cells in non-tumor tissue using immunocytochemistry and antibodies directed against epitopes of epithelial genes. Recently, the sensitive reverse-transcriptase polymerase chain reaction (RT-PCR) has been employed for the detection of tumor cells in bone marrow, using mRNA transcribed from epithelial genes as targets for RT-PCR. RESULTS: In some studies, encouraging results were reported when RT-PCR was used to detect expression of epithelial genes, but in many others frequent false-positive results were observed. These may results from the 'illegitimate expression' of epithelial genes in cells of non-epithelial tissues, such as bone marrow. CONCLUSIONS: Micrometastases in bone marrow can be detected with some sensitivity by antibodies directed against epithelial genes. RNA based methods, using epithelial genes as target for amplification, are less reliable. To improve these methods, a systematic approach is required to identify genes which are highly expressed in solid tumors and completely silent in blood and bone marrow of healthy individuals. Novel techniques, e.g., 'sequential analysis of gene expression (SAGE), are now available that allow such an endeavor.

Biomarkers, Tumor↗

PubMed1995

Lymphomas with testicular localisation show a consistent BCL-2 expression without a translocation (14;18): a molecular and immunohistochemical study.

The presence of the BCL-2 protein was studied in nine non-Hodgkin's lymphomas with testicular localisation. A consistent presence of the BCL-2 protein was found. The chromosomal translocation (14;18) was seen neither by cytogenetic analysis (n = 4) nor by polymerase chain reaction amplification and Southern blotting (n = 9). Therefore, this translocation is not responsible for the presence of the BCL-2 protein in non-Hodgkin's lymphomas with testicular localisation. We suggest that the presence of the BCL-2 protein in these lymphomas is related to the differentiation stage of the B-lymphocytes or may play a role in the pathogenesis of these lymphomas. The consistent finding of the BCL-2 protein in lymphomas with testicular localisation may support the clinical observation that these lymphomas are a separate entity.

Adult↗

PubMed1994

A new B-cell line showing a complex translocation (8;14;18) and BCL2 rearrangement.

A cell line named ROS-50 (Rotterdam suspension cell line no. 50) has been established from peripheral blood of a 69-year-old male with acute lymphoblastic leukemia (FAB type L3). Among the aberrations, cytogenetic analysis showed the presence of 14q+, 18q-, and two 8q- marker chromosomes. With fluorescence in situ hybridization (FISH) we characterized the chromosomal translocations, t(8;14) and t(14;18), in which the same chromosome 14 is involved. PCR analysis demonstrated the presence of on IGH-BCL2 rearrangement with a breakpoint in the minor cluster region (mcr) confirming the t(14;18) characteristic for follicular lymphoma. Additional studies showed high expression of BCL2 protein, an early B-cell immunophenotype, and an unusual pattern of IGH gene rearrangement.

Aged↗

PubMed1994

Clinical significance of t(14; 18)-positive cells in the circulation of patients with stage III or IV follicular non-Hodgkin's lymphoma during first remission.

PURPOSE: To evaluate polymerase chain reaction (PCR) analysis as a method for the detection of circulating lymphoma cells in patients with stage III and IV t(14; 18)-positive follicular Non-Hodgkin's lymphoma (NHL) in first remission in a longitudinal prospective study. PATIENTS AND METHODS: Peripheral blood or bone marrow from eight patients with stage III and IV t(14; 18)-positive NHL was studied using PCR to detect the presence of t(14; 18)-positive cells in the circulation at different times during first remission. RESULTS: In four of six patients with no clinical evidence of disease (NCED), t(14; 18)-positive cells were detectable in the circulation. In one of two patients with clinical evidence of disease (CED), no t(14; 18)-positive cells were found at the four different occasions tested during first remission. First-remission duration ranged from 17 to 81+ months. The duration from the first PCR determination in remission until first relapse or the end of the observation period ranged from 10 to 37+ months. CONCLUSION: In patients with t(14; 18)-positive follicular NHL stage III and IV, treated with conventional remission induction therapy, the presence or absence of t(14; 18)-positive cells in the circulation shows no obvious correlation with the clinical remission status and the remission duration.

Chromosomes, Human, Pair 14↗

PubMed1994

Genomic organization of the translocations (8;14) and (14;18) in a new lymphoma cell line.

We generated a new lymphoma cell line carrying the translocations (8;14) and (14;18) and studied the genomic organization and expression of the BCL-2 and MYC genes. Polymerase chain reaction (PCR) and Southern analysis showed that the breakpoints of t(14;18) were located in the major breakpoint region (mbr) of the BCL-2 gene and just 5' of JH6 in the IgH locus. The breakpoints of the t(8;14) were located upstream of exon 2 in the non-coding region of the MYC gene and near the switch region of the IgH locus. Both IgH loci were involved in chromosomal translocations resulting in the absence of a functional B-cell receptor. Normal BCL-2 and truncated MYC transcripts were detected in these cells. The BCL-2 protein was expressed.

Aged↗

PubMed1993

Translocation (14;18)-positive cells are present in the circulation of the majority of patients with localized (stage I and II) follicular non-Hodgkin's lymphoma.

Stage I and II follicular non-Hodgkin's lymphoma (NHL) is clinically defined as a localized disease. To study the possibility that this disease is in fact disseminated, we used the sensitive polymerase chain reaction (PCR) method using translocation (14;18) as marker. Samples from 21 patients who were clinically diagnosed with stage I or II follicular NHL were analyzed for the presence of t(14;18)-positive cells using PCR. We analyzed (1) the diagnostic lymph node biopsy and (2) the peripheral blood or bone marrow samples from these patients. Translocation (14;18) cells were detected in the diagnostic lymph node biopsies of 12 patients. In 9 of these patients, t(14;18)-positive cells were detected in peripheral blood and/or bone marrow samples at diagnosis and/or after therapy. Thus, in 75% of the follicular NHL patients carrying the t(14;18) as a marker for lymphoma cells, t(14;18)-positive cells were detected in peripheral blood and bone marrow at diagnosis and after therapy. Our results show that t(14;18)-positive cells can be detected in the circulation of patients with stage I and II follicular NHL, indicating that, although diagnosed as localized, the disease is disseminated.

Adult↗

PubMed1992

Detection of residual disease in translocation (14;18) positive non-Hodgkin's lymphoma, using the polymerase chain reaction: a comparison with conventional staging methods.

This paper reports the detection of residual lymphoma cells in blood and bone marrow samples from patients with translocation (t) (14;18) positive non-Hodgkin's lymphoma by the polymerase chain reaction (PCR) compared with conventional staging techniques. In 15 of 22 samples, in which no lymphoma cells could be detected by morphological examination, t(14;18) positive cells were detected by PCR. In 13 of 21 samples, in which a monoclonal B-cell population was not detectable by immunological marker analysis, PCR was positive. The clinical status (physical examination, imaging techniques, leucocyte count, and occasionally morphology and immunological marker analysis) was documented in 30 patients at the time of PCR analysis. In three of 19 patients with clinical evidence of disease, circulating t(14;18) positive cells were not detectable by PCR. Five of 11 patients in clinical remission from 7 to 47 months, showed t(14;18) positive cells in the blood. Our data show that PCR analysis in t(14;18) positive non-Hodgkin's lymphoma offers a powerful tool in the study of residual disease.

Biomarkers, Tumor↗

PubMed1990

Regulation of phosphoinositide hydrolysis induced by histamine and guanine nucleotides in human HeLa carcinoma cells. Calcium and pH dependence and inhibitory role of protein kinase C.

The regulation of phospholipase C has been investigated in both intact and streptolysin-O permeabilized human HeLa carcinoma cells. Stimulation of phospholipase C by histamine and guanosine-5'-O-thiotriphosphate (GTP[S]) requires the presence of at least 10 nM free Ca2+, but is not significantly further increased by raising [Ca2+]i to greater than 10(-6) M. The pH optimum of the inositol phosphate response is at pH 6.8, while small changes in intracellular pH, as occur during hormonal stimulation (0.2-0.4 unit) attenuate the histamine/GTP[S]-induced stimulation of phospholipase C. Increasing cellular cAMP levels, either through addition of cell permeable cAMP analogues to intact cells or by stimulation with isoproterenol, does not affect histamine responsiveness, arguing against cross-talk between both signalling pathways. In contrast, we found that the response to histamine and/or GTP[S] is largely inhibited after brief pretreatment of the cells with phorbol esters or synthetic diacylglycerol prior to permeabilization, suggesting that protein kinase C exerts feedback inhibition at the level of, or downstream from, the putative GTP-binding protein.

Calcium↗

PubMed1990

Histamine-H1-receptor-mediated phosphoinositide hydrolysis, Ca2+ signalling and membrane-potential oscillations in human HeLa carcinoma cells.

In human HeLa carcinoma cells, histamine causes a dose-dependent formation of inositol phosphates, production of diacylglycerol and a transient rise in intracellular [Ca2+]. These responses are completely blocked by the H1-receptor antagonist pyrilamine. In streptolysin-O-permeabilized cells, formation of inositol phosphates by histamine is strongly potentiated by guanosine 5'-[gamma-thio]triphosphate and inhibited by guanosine 5'-[beta-thio]diphosphate, suggesting the involvement of a GTP-binding protein. Histamine stimulates the rapid but transient formation of Ins(1,4,5)P3, Ins(1,3,4)P3 and InsP4. InsP accumulates in a much more persistent manner, lasting for at least 30 min. Studies with streptolysin-O-permeabilized cells indicate that InsP accumulation results from dephosphorylation of Ins(1,4,5)P3, rather than direct hydrolysis of PtdIns. The rise in intracellular [Ca2+] is biphasic, with a very fast release of Ca2+ from intracellular stores, that parallels the Ins(1,4,5)P3 time course, followed by a more prolonged phase of Ca2+ influx. In individual cells, histamine causes a rapid initial hyperpolarization of the plasma membrane, which can be mimicked by microinjected Ins(1,4,5)P3. Histamine-induced hyperpolarization is followed by long-lasting oscillations in membrane potential, apparently owing to periodic activation of Ca2+-dependent K+ channels. These membrane-potential oscillations can be mimicked by microinjection of guanosine 5'-[gamma-thio]triphosphate, but are not observed after microinjection of Ins(1,4,5)P3. We conclude that H1-receptors in HeLa cells activate a PtdInsP2-specific phospholipase C through participation of a specific G-protein, resulting in long-lasting oscillations of cytoplasmic free Ca2+.

Aluminum↗

PubMed1989

Bromocriptine-induced decrease in blood pressure in conscious spontaneously hypertensive rats: evidence for a peripheral site of action.

The aim of the study was to discover whether the dopamine agonist bromocriptine has a central or peripheral site of action on blood pressure. An intraperitoneal injection of bromocriptine (0.5 mg kg-1) induced a long-lasting decrease in blood pressure in conscious spontaneously hypertensive rats (SHR). This effect was blocked by peripheral pretreatment with haloperidol or domperidone, but not by central treatment with haloperidol. A central injection of bromocriptine had only minor effects on blood pressure. These results suggest that primarily peripheral, rather than central, mechanisms are involved in the hypotensive effects of bromocriptine.

Animals↗