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M F Poupon

Publications and source records attributed to M F Poupon.

At least 55 records · Page 3Linked to original sources
PubMed1996

Intracellular pH governs the subcellular distribution of hexokinase in a glioma cell line.

Hexokinase plays a key role in regulating cell energy metabolism. Hexokinase is mainly particulate, bound to the mitochondrial outer membrane in brain and tumour cells. We hypothesized that the intracellular pH (pH1) controls the intracellular distribution of hexokinase. Using the SNB-19 glioma cell line, pH1 variations were imposed by incubating cells in a high-K+ medium at different pH values containing specific ionophores (nigericin and valinomycin), without affecting cell viability. Subcellular fractions of cell homogenates were analysed for hexokinase activity. Imposed pH1 changes were verified microspectrofluorimetrically by using the pH1-sensitive probe SNARF-1-AM (seminaphtho-rhodafluor-1-acetoxymethyl ester). Imposition of an acidic pH1 for 30 min strongly decreased the particulate/total hexokinase ratio, from 63% in the control sample to 31%. Conversely, when a basic pH1, was imposed, the particulate/total hexokinase ratio increased to 80%. The glycolytic parameters, namely lactate/pyruvate ratio, glucose 6-phosphate and ATP levels, were measured concomitantly. Lactate/pyruvate ratio and ATP level were both markedly decreased by acidic pH1 and increased by basic pH1. Conversely, the glucose 6-phosphate level was increased by acidic pH1 and decreased by basic pH1. To demonstrate that the change of hexokinase distribution was not due to altered metabolite levels of glycolysis, a pH1 was imposed for a 5 min incubation time. Modification of the hexokinase distribution was similar to that noted after a 30 min incubation, whereas metabolite levels of glycolysis were not affected. These results provide evidence that the intracellular distribution of hexokinase is highly sensitive to variations of the pH1, and regulates hexokinase activity.

Adenosine Triphosphate↗
PubMed1996

High glycolysis in gliomas despite low hexokinase transcription and activity correlated to chromosome 10 loss.

Loss of chromosome 10 was observed in 10 out of 12 xenografted glioblastomas studied. Chromosome 10 carries the gene coding the hexokinase type 1 isoenzyme (HK-I), which catalyses the first step of glycolysis, which is essential in brain tissue and glioblastomas. We investigated the relationships between the relative chromosome 10 number, the amount of HK-I mRNA, HK-I activity and its intracellular distribution, and glycolysis-related parameters such as the lactate-pyruvate ratio, lactate dehydrogenase (LDH) and ATP contents. Individual tumour HK-I mRNA amounts were 23-65% lower than that of normal human brain and reflected the relative decrease of chromosome 10 number (alpha < 0.01). Total HK activities of individual glioblastomas varied considerably but were constantly (a mean of seven times) lower than that of normal brain tissue. The mitochondria-bound HK-I fraction of individual tumours was generally over 50%, compared with that of normal brain tissue. As shown by lactate - pyruvate ratios, in all the gliomas, glycolysis was elevated to an average of 3-fold that measured in normal brain. An elevated ATP content was also constantly noted. Adaptation of glioblastoma metabolism to the chromosome 10 loss and to the HK-I transcription unit emphasises the critical role of glycolysis in their survival. We hypothesise that HK-I, the enzyme responsible for initiating glycolysis necessary for brain function, may approach its lowest limit in gliomas, thereby opening therapeutic access to pharmacological anti-metabolites affecting energy metabolism and tumour growth.

Adenosine Triphosphate↗
PubMed1996

Inefficient growth arrest in response to dNTP starvation stimulates gene amplification through bridge-breakage-fusion cycles.

Cells often acquire resistance to the antiproliferative agents methotrexate (MTX) or N-phosphonacetyl-L-aspartate (PALA) through amplification of genes encoding the target enzymes dihydrofolate reductase or carbamylphosphate synthetase/aspartate transcarbamylase/dihydroorotase (CAD), respectively. We showed previously that Syrian hamster BHK cells resistant to selective concentrations of PALA (approximately 3 x ID50) arise at a rate of approximately 10(-4) per cell per generation and contain amplifications of the CAD gene as ladder-like structures on one of the two B9 chromosomes, where CAD is normally located. We now find that BHK cells resistant to high concentrations of PALA (approximately 15 x ID50) appear only after prior exposure to selective concentrations of PALA for approximately 72 h. Furthermore, in contrast to untreated cells, BHK cells pretreated with selective concentrations of MTX give colonies in high concentrations of PALA, and cells pretreated with selective concentrations of PALA give colonies in high concentrations of MTX or 5-fluorouracil. As judged by measuring numbers of cells and metaphase cell pairs, BHK cells do not arrest completely when starved for pyrimidine nucleotides by treatment with selective concentrations of PALA for up to 72 h. We propose that DNA damage, caused when cells fail to stop DNA synthesis promptly under conditions of dNTP starvation, stimulates amplification throughout the genome by mechanisms--such as bridge-breakage-fusion cycles--that are triggered by broken DNA. Amplified CAD genes were analyzed by fluorescence in situ hybridization both in cells where amplification was induced by PALA pretreatment and in cells in which the amplification occurred spontaneously, before selection with PALA. The ladder-like structures that result from bridge-breakage-fusion cycles were observed in both cases.

Animals↗
PubMed1996

Fine mapping of human HOX gene clusters.

The chromosome localization of human HOX gene clusters has been reinvestigated by fluorescence in situ hybridization (FISH). Three loci were precisely localized in 7p15.3 (HOXA@), 17q21.3 (HOXB@) and 12q13.3 (HOXC@). The localization of HOXD@ was confirmed to 2q31.

Cells, Cultured↗
PubMed1996

[The annual meeting of the American Association for Cancer Research (AACR), Toronto (Ontario), 18-22 May 1995].

The state of the art concerning major biological phenomenons of importance for current research on urological cancers is first briefly presented, followed by notes on the more outstanding presentations in this field. These notes are organized in a synthetic fashion, in order to point to the meaning of the hypotheses and findings presented, when taken together, as they pertain to the understanding of the mechanisms at play in urological cancers, as we see them in 1995. Some concepts seem to have now reached a point where we can expect to see some applications in a not so distant future: in prostate cancer, it is confirmed that the machinery of apoptosis is functional even in the hormone-insensitive cells, suggesting that its enhancement might be useful in these often difficult situations; techniques to detect circulating malignant cells, which have been greatly refined (RT-PCR of PSA and PSM), are now extremely sensitive and may prove unvaluable in providing intermediate end points to compare the relative efficacy of treatment regimens in clinical trials; the symposium on prostate cancer screening by PSA dosage was an excellent opportunity to review extensively the data available on this topic, but -as expected- it could not decide on some essential issues; in bladder tumors, data on the expression of adhesion molecules (CD44 variant) are still preliminary, but some provocative observations have been reported (presence on mature ARN, only in bladder cancer cells, of intronic sequences that have not been excised); in renal cell cancer, a considerable amount of knowledge has accumulated on the von Hippel-Lindau gene, a putative anti-oncogene, and work is in progress to define the function of its protein; finally, pathways essential to understanding and treating cancer have been dissected, particularly the apoptosis-proliferation network, and the involvement in it of p53, Waf-1 and the bcl-2 gene family cascade.

Apoptosis↗
PubMed1995

Mitochondria-bound hexokinase as target for therapy of malignant gliomas.

Hexokinase plays an important role in glucose-utilizing tissues like normal brain and cancers. In these tissues, hexokinase (HK) is mainly bound to mitochondria (mHK). Our objectives were to evaluate total HK (tHK) activity and mHK fraction in gliomas and to determine whether mHK binding could be targeted for therapy. Tumors were obtained from 26 patients and 13 were xenografted. HK, lactate and ATP were measured in cytosol and mitochondria extracts. The tHK expressed in mU/mg protein were 147 +/- 19 and 78 +/- 12, in fresh gliomas and xenografts, respectively, and of 489 in the normal brain. The mHK fraction was 76% in normal brain, 74 +/- 4% in fresh tumors and 53 +/- 6% in xenografts. Lactate/mHK ratios were higher in gliomas than in normal brain. The ATP was 10, 52 +/- 31 and 19 +/- 8 nmol/mg protein in normal brain, xenografts and fresh gliomas respectively. Loss of one copy of chromosome 10 which carries the HK1 gene, was evidenced in 11 of the 13 xenografted gliomas. The anti-tumor effect of lonidamine (LND), which affects glycolysis in interfering with mHK activity, was tested in nude mice bearing 4 gliomas. LND (125 mg/kg, given i.p., twice daily for 5 days) led to a growth inhibition of TG-7-RO of 72%, with 2-fold growth retardation, and had no effect for TG-8-OZ. Intermediate LND-sensitivities for TG-11-DU and TG-10-PY were noted. The LND-sensitivity was correlated with the mHK activity (R2 = 0.73) and mHK fraction (R2 = 0.88). HK binding to mitochondria is a key of glycolysis in malignant gliomas, and targetting this binding with appropriate agents could be an effective therapeutic approach.

Adenosine Triphosphate↗
PubMed1995

Regulation and mechanisms of gene amplification.

Amplification in rodent cells usually involves bridge-breakage-fusion (BBF) cycles initiated either by end-to-end fusion of sister chromatids, or by chromosome breakage. In contrast, in human cells, resistance to the antimetabolite N-(phosphonacetyl)-L-aspartate (PALA) can be mediated by several different mechanisms that lead to overexpression of the target enzyme carbamyl-P synthetase, aspartate transcarbamylase, dihydro-orotase (CAD). Mechanisms involving BBF cycles account for only a minority of CAD amplification events in the human fibrosarcoma cell line HT 1080. Here, formation of a 2p isochromosome and overexpression of CAD by other types of amplification events (and even without amplification) are much more prevalent. Broken DNA is recognized by mammalian cells with intact damage-recognition pathways, as a signal to arrest or to die. Loss of these pathways by, for example, loss of p53 or pRb tumour suppressor function, or by increased expression of ras and myc oncogenes, causes non-permissive rat and human cells to become permissive both for amplification and for other manifestations of DNA damage. In cells that are already permissive, amplification can be stimulated by overexpressing oncogenes such as c-myc or ras, or by damaging DNA in a variety of ways. To supplement genetic analysis of amplification in mammalian cells, an amplification selection has been established in Schizosaccharomyces pombe. Selection with LiCl yields cells with amplified sod2 genes in structures related to those observed in mammalian cells. The effect on amplification in S. pombe can now be tested for any mutation in a gene involved in repair of damaged DNA or in normal cellular responses to DNA damage.

Animals↗
PubMed1995

Evolution of chromosomal alterations and biologic features in two small cell lung carcinoma cell lines established from one patient during the course of the disease.

Two small cell lung cancer (SCLC) cell lines were established from metastases of a patient during the course of the disease. SCLC 74A was derived from biopsy material obtained at the time of diagnosis and SCLC 74B was from a biopsy specimen of a relapsed tumor obtained after treatment. A transition occurred from SCLC 74A, an intermediate form with 5% large cells to SCLC 74B, a standard mixed form with 20% of large cells, with a decrease in neuroendocrine markers and a substantial increase in P-glycoprotein, a multidrug resistance marker. For both cell lines, R-banding and FISH indicated a del(1)(p35pter) also found in other neural-crest-derived tumors, the loss of regions with suspected tumor suppressor genes at 3p, 5q, and 17p, and a recurrent translocation of the 6q24-6qter region to 10p14. Further genetic modifications in SCLC 74B affected chromosomes 2, 3, 5, 10, 11, 14, and 15. The main observations were a der(2)t(2;5)(p16;q?); a der(3;11)(q10;p10) in SCLC 74A which became der(3;14)(q10;p10) and der(11;14)(p10;q10) in SCLC 74B; and the insertion of the 5q13-5q31 region in the der(10)t(6;10). The finding of the same structural abnormalities in both cell lines suggests a monoclonal origin for both metastases. Hypotetraploid cells were in the same proportion as large cells whose number was a characteristic feature of each cell line. They possessed twice the same chromosomal alterations observed in the hypodiploid cells. This suggests a permanent process of tetraploidization.

Aged↗
PubMed1995

Adding a reverser (verapamil) to combined chemotherapy overrides resistance in small cell lung cancer xenografts.

Small cell lung carcinomas (SCLC) are characterised by chemosensitivity to diverse antitumoral compounds. However, responses are transitory and relapses are commonly observed. We examined the ability of verapamil, a reverser of P-glycoprotein (Pgp)-related resistance, to improve the efficacy of CyCAV combined chemotherapy (Cy, cyclophosphamide (CPA); C, cisplatin (CDDP); A, doxorubicin (ADM);V, etoposide (VP16)), as currently administered to SCLC patients at Institut Gustave-Roussy, France, and adapted to the treatment of nude mice implanted with these tumours. Although Pgp encoded by the MDR1 (multidrug resistance) gene is not the only mechanism for multidrug resistance (MDR), and not all drugs included in this regimen are recognised by Pgp, we anticipated a therapeutic benefit. Four different SCLC lines, expressing the MDR1 gene and recently grafted into nude mice, were used. SCLC-75, SCLC-6 and SCLC-41 originated from untreated patients, and SCLC-74T was derived from a patient treated with a combination of ADM, CPA and VP16. SCLC-41% and SCLC-6T tumours were used after having undergone, respectively, five and nine cycles of in vivo passage and CyCAV treatment of the tumour-bearing nude mice, to reinforce their chemoresistance. The efficacy of the CyCAV regimen, associated with or without verapamil (given 24 h before CyCAV on days 1-5), was tested on the growth of these SCLC. Verapamil (25 mg/kg) improved the antitumour effect of CyCAV in mice bearing SCLC-6T, SCLC-41T and SCLC-75 tumours, although toxicity was observed. Verapamil modestly delayed the plasma clearance of ADM. Two daily injections of 10 mg/kg of verapamil, administered at a 3 h interval, proved to be effective, whereas the same total dose administered as a bolus was not. These results indicate that the association of some reversers of MDR, including drugs possibly interacting with Pgp, might potentiate SCLC combined chemotherapy.

Animals↗
PubMed1995

[Cancer metastasis].

Metastases result from the implantation of tumor cells into various organs, distant from the primary tumor. Among primary tumor cells, a small number undergo genetic events determining metastatic function acquisition. The metastatic function comprises the lack of homotypic intercellular connections, due to proteolytic enzyme effects and/or lack of adhesion molecule synthesis, stimulation of peri- and intratumoral angiogenesis, motility adhesion molecule synthesis, stimulation of peri- and intratumoral angiogenesis, motility and invasiveness, adhesiveness to acellular substrates or heterotypic cells, resistance to immune defenses, alteration of growth factor receptivity, and even growth autonomy. Formation of metastatic foci needs the establishment of an ecosystem born from the contribution of both host and tumor and in which respective cells interact.

Cell Adhesion↗
PubMed1995

Evaluation of multidrug resistant phenotype by flow cytometry with monoclonal antibodies and functional tests.

Multidrug resistant (MDR) phenotype is characterized by a defect in drug accumulation caused by overexpression of a transmembrane glycoprotein, the P-glycoprotein (P-gp). MDR phenotype can be characterized either with monoclonal antibodies raised against P-gp or with functional tests, most often based on the incorporation of fluorescent compounds. In the present study, data obtained with the monoclonal antibodies C219, JSB1 and MRK16 are compared to those of functional tests performed by flow cytometry including uptake of daunorubicin (DNR), Rhodamine 123 (Rh 123) or Hoechst 33342. Sensitive and resistant cell lines K562S, K562R, KBA1 and KB31, derived either from a human chronic myeloid leukemia or from a human epithelial carcinoma, were used. In resistant cells, P-gp expression was revealed with either the monoclonal antibodies C219, JSB1 or MRK-16. The most specific results were obtained with MRK-16. With functional tests, no matter which dyes were used, the fluorescence was always stronger in sensitive than in resistant cells. However, with DNR and Hoechst 33342, an incorporation of these dyes was exhibited in resistant cells. This phenomenon was not observed with Rh 123, which makes it possible to distinguish clearly between sensitive and resistant cells and to detect as few as 1% of resistant cells. Because of its high sensitivity, the functional test involving incorporation of Rh 123 was successfully used in acute myeloid leukemia to detect multichemoresistant cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

[Two colons--two cancers? Proximal or distal adenocarcinoma: arguments for a different carcinogenesis].

The purpose of this review is to study the literature concerning normal colon and colorectal cancer for evidencing that the location of the primary proximal or distal tumor may determine two categories of carcinogenesis. The proximal or distal normal colon can be considered as two different organs. Their embryologic origins are different, the splenic flexure starts the distal segment. Antigenic pattern as well as the use of metabolic pathways, such as that of glucose, butyrate and polyamines differ. Epidemiologic, macroscopic and histological features and the inherited and acquired genetic abnormalities allow in some cases to distinguish between two types of cancer according to their proximal or distal location. These two forms are not entirely different and these features can overlap. However the recognition of these two different forms of colon cancer, must be taken in account for clinical or basic research and evaluation of data.

Adenocarcinoma↗
PubMed1995

Flow cytometry evaluation of the multidrug-resistant phenotype with functional tests involving uptake of daunorubicin, Hoechst 33342, or rhodamine 123: a comparative study.

Multidrug-resistant (MDR) cells are characterized by a defect in drug accumulation caused by overexpression of a transmembrane glycoprotein, the P-glycoprotein (P-gp). The MDR phenotype can be characterized either by use of monoclonal antibodies raised against P-gp or with functional tests based on the intracellular accumulation of fluorescent molecules. The aim of the present study was to compare the effectiveness of functional tests performed by flow cytometry including uptake of daunorubicin (DNR) (2 micrograms/ml), Hoechst 33342 (5 micrograms/ml), or rhodamine 123 (RH 123) (0.1 microgram/ml); and to evaluate the effect of cell death induced by heating at 60 degrees C for 2 h on incorporation of DNR and RH 123. Sensitive and resistant human hematopoietic K 562 cells expressing P-gp were identified by monoclonal antibodies C 219 and MRK-16. Fluorescence of the dyes was always higher in sensitive than in resistant cells. However, DNR and Hoechst 33342 produced a slight incorporation in resistant cells, while RH 123 showed lack of incorporation in resistant cells. Thus, RH 123 allows sensitive and resistant cells to be clearly distinguished. In case of cell death, accumulation of RH 123 and DNR were different. With RH 123, fluorescence intensity strongly decreased in sensitive cells. With DNR, fluorescence intensity was enhanced in resistant cells. Thus, when the MDR phenotype is defined by uptake of DNR or RH 123, artifactual results due to cell death may be avoided by using a dye such as propidium iodide to eliminate dead cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

HOX gene expression in human small-cell lung cancers xenografted into nude mice.

Transcription factors are crucial to an understanding of the molecular basis of neoplasia. Homeobox-containing genes are a family of transcriptional regulators encoding DNA-binding homeodomains, involved in the control of normal development. Class-I human homeobox-containing genes (HOX genes) display a peculiar chromosomal organization, perhaps directly related to their function. Aberrant expression of homeobox-genes has been associated with both morphological abnormalities and oncogenesis. We have recently observed that alterations in HOX gene expression are detectable in kidney and colon cancer when compared to the corresponding normal organs. Here we have analyzed the expression of HOX genes in primary and metastatic human small-cell lung cancer (SCLC) xenografted in nude mice, in order to investigate whether HOX gene expression correlates with the histology and stage of SCLC progression. The results show that different SCLCs display differential patterns of HOX gene expression. Furthermore, in SCLC, the number of actively expressed HOX genes might be substantially lower in metastatic cancers than in primary tumors. The alteration in HOX gene expression in SCLCs mainly concerns the HOX B and C loci. This finding suggests that downregulation of HOX genes may play a role in small-cell lung cancer progression, possibly through their implication in tumor suppression.

Animals↗
PubMed1994

A minority of carcinoma cells producing acidic fibroblast growth factor induces a community effect for tumor progression.

It is generally accepted that primary tumors become heterogeneous as a consequence of tumor-cell genetic instability. Clonal dominance has been shown to occur in some experimental models allowing a subpopulation of cells to overgrow the primary heterogeneous tumor and to metastasize. Alternatively, interactions among coexisting tumor subpopulations may contribute to the emergence of a malignant invasive primary solid tumor. We asked the question whether emergence of carcinoma cells producing a growth/dissociating factor within a tumor cell population may be a determinant for tumor progression and for clonal dominance. To mimic such a situation, we have investigated the impact of tumor subpopulation heterogeneity in an in vivo model in which mixtures of carcinoma cells that differ in their ability to produce acidic fibroblast growth factor are injected into nude mice. Our data indicate that a growth-factor-producing cell subpopulation can confer increased tumorigenicity to an entire cell population and subsequently elicit a shorter delay for appearance of metastasis. A community effect via cell interactions may account for a heterogeneous tumor cell population rather than clonal dominance during progression of certain tumor types.

Animals↗