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T Lahaye

Publications and source records attributed to T Lahaye.

At least 19 recordsLinked to original sources
PubMed2003

Molecular monitoring of response to imatinib (Glivec) in CML patients pretreated with interferon alpha. Low levels of residual disease are associated with continuous remission.

A significant proportion of chronic myeloid leukemia (CML) patients achieve a major cytogenetic remission (MCR) to imatinib therapy after failing interferon (IFN) alpha-based protocols. We sought to determine levels of residual disease in patients with MCR using various molecular methods and to establish a relation between residual BCR-ABL transcript levels and rate of relapse in complete cytogenetic remission (CCR). Response was measured by conventional cytogenetic analysis, hypermetaphase and interphase fluorescence in situ hybridization (HM-FISH, IP-FISH) of bone marrow (BM) cells, qualitative nested and quantitative reverse transcriptase polymerase chain reaction (RT-PCR) for BCR-ABL transcripts. We investigated 323 peripheral blood (PB) and BM samples from 48 CML patients who achieved a complete (Ph+ 0%; n=41) or partial (Ph+ 1-34%; n=7) cytogenetic remission after 3-20 months of imatinib therapy. Prior to imatinib, 35 patients were in chronic phase (CP), eight in accelerated phase (AP), four in myeloid and one in lymphoid blast crisis. HM-FISH results correlated with ratios BCR-ABL/ABL in PB and BM. In patients with CCR, residual disease was detectable by HM-FISH (31%), IP-FISH (18%), and RT-PCR (100%). During follow-up, BCR-ABL became undetectable in two patients (one CP, one AP) by both nested and quantitative RT-PCR. CCR is ongoing in 30 evaluable patients, 11 patients have relapsed. At the time of best response, median ratios BCR-ABL/ABL were 2.1% (range 0.82-7.8) in patients with subsequent relapse and 0.075% (range 0-3.9) in patients with ongoing remission (P=0.0011). All 16 CP patients, who achieved ratios BCR-ABL/ABL <0.1% as best molecular response are in continuous remission, while 6/13 patients (46%) with ratios >/=0.1% have relapsed (P=0.0036). We conclude that: (i) in patients with CCR to imatinib, HM-FISH and RT-PCR usually reveal residual BCR-ABL+ cells; (ii) RT-PCR results derived from PB and BM are comparable in CP CML; and (iii) low levels of residual disease with ratios BCR-ABL/ABL &<0.1% are associated with continuous remission.

Adult↗
PubMed2002

[Resistance to tumor specific therapy with imatinib by clonal selection of mutated cells].

HISTORY AND CLINICAL FINDINGS: A 60-year-old woman presented with night-sweats and increasing weakness. Physical examination revealed no abnormalities. For 27 years she had been treated for Philadelphia-positive chronic myeloid leukemia (CML). Because of progressive disease treatment with the tyrosine kinase inhibitor imatinib (STI571, Glivec (R)) had been started 9 months before. She had achieved complete hematological remission within 8 weeks, but not a cytogenetic response. INVESTIGATIONS: Elevated WBC count (26.7/nl) with a differential displaying typical features of acceleration in bone marrow aspirate confirmed CML in accelerated phase. Sequencing of the ATP binding site of the BCR-ABL gene, which - at protein level - is the target for imatinib, revealed the clonal selection of cells harboring a point mutation leading to the exchange of amino acid 253 from tyrosine to histidine. This was considered to be the cause of resistance to imatinib. TREATMENT AND COURSE: Dose increase of imatinib up to 600 mg daily and administration of cytarabine did not overcome resistance. Imatinib therapy was discontinued; hematologic remission was induced by oral therapy with hydroxyurea and mercaptopurine. In the course of the following 6 months a gradual decrease of the resistant clone from 100 % down to lower than the detection limit of the method was demonstrated. CONCLUSIONS: Clonal mutations are often the cause of resistance to imatinib therapy. They can be detected by sequencing of the ATP binding site of BCR-ABL in specialized laboratories. This case shows that discontinuation of imatinib therapy can significantly reduce the mutated (resistant) clone and thereby restore sensitivity to imatinib.

Amino Acid Substitution↗
PubMed2002

Early reduction of BCR-ABL mRNA transcript levels predicts cytogenetic response in chronic phase CML patients treated with imatinib after failure of interferon alpha.

The degree of tumor load reduction as measured by cytogenetic response is an important prognostic factor for chronic myelogenous leukemia (CML) patients on therapy. We sought to determine whether BCR-ABL transcript levels can predict chromosomal response. Residual disease was evaluated in 120 CML patients in chronic phase (CP) treated with the selective tyrosine kinase inhibitor imatinib after resistance or intolerance to interferon alpha (IFN). Median time of therapy was 401 days (range 111-704). BCR-ABL and total ABL transcripts were measured in 486 peripheral blood (PB) specimens with a real time RT-PCR approach using fluorescent-labeled hybridization probes (LightCycler technology) and results were expressed as the ratio BCR-ABL/ABL. Cytogenetic response was determined in 3-monthly intervals: From 101 evaluable patients, 42 achieved a complete (CR, 0% Philadelphia chromosome (Ph)- positive metaphases), 18 a partial (PR, 1-34% Ph+), 13 a minor (MR, 35-94% Ph+), and 26 no response (NR, >94% Ph+). All PB samples were RT-PCR positive. The proportion of Ph+ metaphases and simultaneous BCR-ABL/ABL ratios correlated with r = 0.74, P < 0.0001. In order to investigate whether early molecular analysis may predict cytogenetic response, quantitative RT-PCR data obtained after 1 and 2 months of therapy were compared with cytogenetic response at 6 months. BCR-ABL/ABL ratios after 1 month were not predictive, but results after 2 months correlated with the consecutive cytogenetic response (P = 0.0008). The probability for a major cytogenetic response was significantly higher in patients with a BCR-ABL/ABL ratio <20% after 2 months of imatinib therapy. We conclude that: (1) quantitative determination of residual disease with real time RT-PCR is a reliable and sensitive method to monitor CML patients on imatinib therapy; (2) BCR-ABL/ABL ratios correlate well with cytogenetic response; (3) in IFN-pretreated patients all complete responders to imatinib have evidence of residual disease with the limited follow-up available; and (4) cytogenetic response at 6 months of therapy in CP patients is predictable with real time RT-PCR at 2 months.

Adult↗
PubMed2002

Improvement of molecular monitoring of residual disease in leukemias by bedside RNA stabilization.

The sensitivity of assays designed to monitor minimal residual disease (MRD) by RT-PCR in leukemia depend on quality and quantity of RNA derived from peripheral blood (PB) and bone marrow (BM) leukocytes. Shipment of material may lead to RNA degradation resulting in a loss of sensitivity and, potentially, false negative results. Furthermore, degradation may lead to inaccurate estimates of MRD in positive specimens. We sought to determine feasibility and efficacy of a novel blood collection and processing system which is based on integrated RNA stabilization at the time of phlebotomy (PAXgene Blood RNA Kit) by comparison with standard methods of RNA extraction (cesium chloride gradient ultracentrifugation and RNeasy Mini Kit) using unstabilized EDTA anticoagulated PB. In 26 patients with chronic myelogenous leukemia (CML) on therapy, PB was processed after a storage time at room temperature of 2 and 72 h according to these protocols. BCR-ABL, total ABL and glucose-6-phosphate dehydrogenase (G6PD) mRNA transcripts of PB samples were quantified as a measure for response to therapy and RNA integrity. RNA yield expressed as the ratio of ABL transcripts after a storage time of 72 h/ABL transcripts after a storage time of 2 h at room temperature was significantly higher with the stabilizing method (median 0.40) compared to the RNeasy method using unstabilized PB (median 0.13, P = 0.01). Furthermore, ratios BCR-ABL/ABL after 72 vs 2 h still correlated well using the PAXgene method (r = 0.99, P < 0.0001) in contrast to the standard method which did not (r = 0.65, P = 0.03). Even investigation of complete cytogenetic responders with very low tumor burden showed a good correlation of ratios BCR-ABL/ABL compared to the reference method. Comparable results were achieved using G6PD transcripts as standard. We conclude that the new PAXgene stabilization method could improve RNA quality and the comparability of molecular monitoring within and between multicenter trials.

Adult↗
PubMed2002

Molecular and chromosomal mechanisms of resistance to imatinib (STI571) therapy.

Selective inhibition of the BCR-ABL tyrosine kinase by imatinib (STI571, Glivec/Gleevec) is a promising new therapeutic strategy in patients with chronic myelogenous leukemia (CML). Despite significant hematologic and cytogenetic responses, resistance occurs, particularly in patients with advanced disease. We sought to determine the underlying mechanisms. Sixty-six patients with CML in myeloid blast crisis (n = 33), lymphoid blast crisis (n = 2), accelerated phase (n = 16), chronic phase (n = 13), and BCR-ABL-positive acute lymphoblastic leukemia (n = 2) resistant to imatinib were investigated. Median duration of imatinib therapy was 148 days (range 6-882). Patients were evaluated for genomic amplification of BCR-ABL, overexpression of BCR-ABL transcripts, clonal karyotypic evolution, and mutations of the imatinib binding site in the BCR-ABL tyrosine kinase domain. Results were as follows: (1) Median levels of BCR-ABL transcripts, were not significantly changed at the time of resistance but 7/55 patients showed a >10-fold increase in BCR-ABL levels; (2) genomic amplification of BCR-ABL was found in 2/32 patients evaluated by fluorescence in situ hybridization; (3) additional chromosomal aberrations were observed in 19/36 patients; (4) point mutations of the ABL tyrosine kinase domain resulting in reactivation of the BCR-ABL tyrosine kinase were detected in 23/66 patients. In conclusion, although the heterogeneous development of imatinib resistance is challenging, the fact that BCR-ABL is active in many resistant patients suggests that the chimeric oncoprotein remains a good therapeutic target. However, patients with clonal evolution are more likely to have BCR-ABL-independent mechanisms of resistance. The observations warrant trials combining imatinib with other agents.

Antineoplastic Agents↗
PubMed2002

Active neutron dosemeters based on microdosimetric principles: research studies.

Over the past few years, the Institute for Radiation Protection and Nuclear Safety (IRSN) has been studying a personal electronic neutron dosemeter and an ambient electronic neutron dosemeter based on experimental microdosimetric principles using low pressure proportional counters. The results obtained in 2000 and in 2001 with the cylindrical tissue-equivalent proportional counter developed for use in radiation protection and filled with a low pressure tissue-equivalent gas (propane based) are presented here.

Dose-Response Relationship, Radiation↗
PubMed2002

Gamma-probe-directed lymphatic mapping and sentinel lymphadenectomy in primary cutaneous melanoma.

BACKGROUND: Radiotracer and blue-dye lymphatic mapping is a recommended combined method to guide sentinel lymphadenectomy and full regional lymph node dissection in selected patients with cutaneous melanoma. OBJECTIVE: To evaluate the diagnostic accuracy and the prognostic value of gamma-probe-directed lymphatic mapping in cutaneous melanomas. METHODS: Sixty-five stage I and II melanoma patients underwent gamma-probe-directed lymphatic mapping. Sentinel lymph nodes were studied by both conventional and immunohistochemical stainings. The median follow-up was 11 months. RESULTS: Sensitivities of preoperative and intraoperative sentinel lymph node detection were 100 and 98%, respectively. Only 1 failure of detection and 1 missed same-basin metastasis were experienced in the axillary and cervical areas, respectively. Eleven patients (16.9%) had sentinel node metastases leading to adjuvant therapy. CONCLUSION: Gamma-probe-directed lymphatic mapping is useful for staging melanoma. However, in the expectation of a more specific identification of the sentinel lymph node, the standard protocol remains recommended for exploring the axillary and cervical areas. The histological examination supported in some cases by immunohistochemistry remains mandatory in all cases.

Female↗
PubMed2002

[Systemic infections of dental origin].

Microorganisms harbored in the oral cavity have long been recognized to cause systemic disease with a well known mechanism of spread via the blood stream. Different factors, including the presence of periodontal disease, the number of dental extractions or the duration of dental surgery have an influence on the risk of bacteremia. Infectious endocarditis is classically cited, but there are other potential problems including brain abscess, meningitis, lung or lie abscess, and even for some authors, a risk of thrombotic heart disease. It is important to keep in mind that some of these focal infections may be possible complications of dental (or buccal) infection. Prevention is crucial.

Bacteremia↗
PubMed2001

Chromosome landing at the tomato Bs4 locus.

The tomato (Lycopersicon esculentum) Bs4 gene confers resistance to strains of Xanthomonas campestris pathovar vesicatoria that express the avirulence protein AvrBs4. As part of a map-based cloning strategy for the isolation of Bs4, we converted Bs4-linked amplified fragment length polymorphism (AFLP) and restriction fragment length polymorphism (RFLP) markers into locus-specific sequence-tagged-site (STS) markers. The use of these markers for the analysis of 1972 meiotic events allowed high-resolution genetic mapping within a 1.2-cM interval containing the target gene. Two tomato yeast artificial chromosome (YAC) clones, each harboring inserts of approximately 250 kb, were identified using the marker most closely linked to Bs4. YAC end-specific markers were established and employed to construct a local YAC contig. The ratio of physical to genetic distance at Bs4 was calculated to be 280 kb/cM, revealing that recombination rates in this region are about three times higher than the genome-wide average. Mapping of YAC end-derived markers demonstrated that the Bs4 locus maps within a region of 250 kb, corresponding to a genetic interval of 0.9 cM.

Chromosome Mapping↗
PubMed2001

Molecular secrets of bacterial type III effector proteins.

Most Gram-negative phytopathogenic bacteria are thought to inject effector proteins into the plant cell via a type III secretion system that is essential for pathogenicity. Plant targets and the mode of action of type III effector proteins, which include avirulence (Avr) proteins, are largely unknown. However, recent findings have shed light on the molecular mechanisms of Avr action. Here, we focus on two classes of Avr proteins (the AvrBs3 and AvrRxv/YopJ families) that have been suggested to act as transcription factors and proteases, respectively.

Apoptosis↗
PubMed2001

The first operational dosemeter for neutrons which complies with IEC standard 1323.

Individual neutron dosimetry represents one of the current difficulties in the field of radiological protection of workers. Since March 1999, the regulatory requirements in France for active (i.e. operational) dosimetry have been those of ICRP Publication 60, applicable from May 2000, necessitating the introduction of a new generation of neutron dosemeters. Over the last few years, the Institute for Nuclear Safety and Protection has been studying an individual electronic dosemeter for neutrons based on a semiconducting detector, capable of meeting the specifications laid down by a neutron dosimetry work group, including members from all the main players in the French nuclear industry. In 1998, the IPSN began transferring technology to the Saphymo company which, by the end of 2001, will be marketing Saphydose-n, the first individual dosemeter for neutrons which complies with IEC Standard 1323. This dosemeter is of compact design and can assess the individual dose equivalent Hp(10) in mixed neutron and gamma radiation fields. It wil be usable in any nuclear facility without prior knowledge of the average neutron spectrum or of the neutron-gamma ratio. It will be possible to connect the Saphydose-n dosemeter to any of the existing gamma deserter terminals to read the dose data and recharge the batteries.

Air Pollution, Radioactive↗
PubMed2001

An active personal neutron dosemeter based on microdosimetric principles: CIME.

Over the last few years IPSN has been developing a small, tissue equivalent proportional counter (TEPC) with multielement geometry for personal radiation protection monitoring. This paper presents the last prototype, which is insensitive to microphony, and the experimental results. Numerical modelling results using CERN codes are partly presented and allow an understanding of the nuclear and electrostatic physics involved in a TEPC.

Consumer Product Safety↗
PubMed2001

Genetic mapping and functional analysis of the tomato Bs4 locus governing recognition of the Xanthomonas campestris pv. vesicatoria AvrBs4 protein.

Xanthomonas campestris pv. vesicatoria is the causal agent of bacterial spot disease on pepper (Capsicum spp.) and tomato (Lycopersicon spp.). Analysis of 17 different Lycopersicon accessions with avrBs4-expressing X. campestris pv. vesicatoria strains identified 15 resistant and two susceptible tomato genotypes. Genetic analysis revealed that AvrBs4 recognition in tomato is governed by a single locus, designated Bs4 (bacterial spot resistance locus no. 4). Amplified fragment length polymorphism and bulked DNA templates from resistant and susceptible plants were used to define a 2.6-cM interval containing the Bs4 locus. A standard tomato mapping population was employed to localize Bs4-linked markers on the short arm of chromosome 5. Investigation of X. campestris pv. vesicatoria hrp mutant strains revealed that AvrBs4 secretion and avirulence activity are hrp dependent. Agrobacterium-based delivery of the avrBs4 gene into tomato triggered a plant response that phenotypically resembled the hypersensitive response induced by avrBs4-expressing X. campestris pv. vesicatoria strains, suggesting symplastic perception of the avirulence protein. Mutations in the avrBs4 C-terminal nuclear localization signals (NLSs) showed that NLSs are dispensable for Bs4-mediated recognition. Our data suggest that tomato Bs4 and pepper Bs3 employ different recognition modes for detection of the highly homologous X. campestris pv. vesicatoria avirulence proteins AvrBs4 and AvrBs3.

Bacterial Proteins↗
PubMed2001

Sequence haplotypes revealed by sequence-tagged site fine mapping of the Ror1 gene in the centromeric region of barley chromosome 1H.

We describe the development of polymerase chain reaction-based, sequence-tagged site (STS) markers for fine mapping of the barley (Hordeum vulgare) Ror1 gene required for broad-spectrum resistance to powdery mildew (Blumeria graminis f. sp. hordei). After locating Ror1 to the centromeric region of barley chromosome 1H using a combined amplified fragment length polymorphism/restriction fragment-length polymorphism (RFLP) approach, sequences of RFLP probes from this chromosome region of barley and corresponding genome regions from the related grass species oat (Avena spp.), wheat, and Triticum monococcum were used to develop STS markers. Primers based on the RFLP probe sequences were used to polymerase chain reaction-amplify and directly sequence homologous DNA stretches from each of four parents that were used for mapping. Over 28,000 bp from 22 markers were compared. In addition to one insertion/deletion of at least 2.0 kb, 79 small unique sequence polymorphisms were observed, including 65 single nucleotide substitutions, two dinucleotide substitutions, 11 insertion/deletions, and one 5-bp/10-bp exchange. The frequency of polymorphism between any two barley lines ranged from 0.9 to 3.0 kb, and was greatest for comparisons involving an Ethiopian landrace. Haplotype structure was observed in the marker sequences over distances of several hundred basepairs. Polymorphisms in 16 STSs were used to generate genetic markers, scored by restriction enzyme digestion or by direct sequencing. Over 2,300 segregants from three populations were used in Ror1 linkage analysis, mapping Ror1 to a 0.2- to 0.5-cM marker interval. We discuss the implications of sequence haplotypes and STS markers for the generation of high-density maps in cereals.

Base Sequence↗
PubMed2001

[Selective inhibition of tyrosine kinases - a new therapeutic principle in oncology].

Tyrosine kinases are enzymes that regulate mitosis, differentiation, migration, neovascularization, and apoptosis. Their spectrum and association with specific malignancies offer multiple targets for therapeutic intervention. Chronic myelogenous leukemia (CML) represents an ideal target for a therapy using a selective inhibitor of the BCR-ABL tyrosine kinase. The 2-phenylpyrimidine derivative STI571 was rationally designed to inhibit ABL and BCR-ABL tyrosine kinase activities through competitive ATP-binding pocket interactions. Phase II data demonstrate hematologic and cytogenetic responses in interferon refractory chronic-phase, accelerated-phase and blast crisis patients. However, long-term observation is needed to confirm that response data result in prolongation of survival. STI571 is being studied in other malignancies, including leukemias characterized by expression of alternate molecular forms of BCR-ABL and those expressing protein tyrosine kinases with ATP-binding pockets structurally similar to ABL, e.g. c-kit and PDGF-R. Gastrointestinal stromal tumor (GIST) cells overexpress the stem cell factor receptor CD117, the product of the proto-oncogene c-kit. Inhibition of c-kit in vivo results in an immediate metabolic change of the tumor cells, detectable by positron emission tomography. Since c-kit overexpression is inhibited in small-cell lung cancer cell lines, a study with STI571 as second-line therapy of c-kit-positive small-cell lung cancer is in progress. Clinical studies are ongoing in malignancies associated with an enhanced activity of the PDGF-R, such as highgrade glioma, prostate cancer and leukemias with rearrangements of PDGF-R. The development of selective tyrosine kinase inhibitors is considered a promising approach for the design of new drugs. Clinical responses to STI571 in various malignancies may stimulate greater interest in the clinical use of tyrosine kinase inhibitors.

Antineoplastic Agents↗
PubMed2000

Promoter strength influences polyamine metabolism and morphogenic capacity in transgenic rice tissues expressing the oat adc cDNA constitutively.

We analyzed molecularly and biochemically a series of transgenic rice lines expressing the oat adc (arginine decarboxylase) cDNA under the control of the constitutive maize ubiquitin 1 promoter. We established baseline biochemical parameters to elucidate the role of polyamines (PAs) during morphogenesis. We measured mRNA levels, ADC enzyme activity and cellular PAs in dedifferentiated callus. Polyamine levels were also quantified in two subsequent developmental stages--regenerating tissue and differentiated shoots. We observed significant (P < 0.05) differences in the levels of individual PAs at the three developmental stages. The amounts of putrescine (Put) and spermidine (Spd) in dedifferentiated transgenic callus were lower than those in the wild type or in hpt (hygromycin resistant)-controls, whereas the amount of spermine (Spm) was increased up to two-fold. In regenerating tissue, this trend was reversed, with significantly higher levels of Put and Spd (P < 0.05), and lower levels of Spm (P < 0.05) compared to non-transformed or hpt-control tissues at the same developmental stage. In differentiated shoots, there was a general increase in PA levels, with significant increases in Put, Spd, and Spm (P < 0.05); on occasion reaching six times the level observed in wild type and hpt-control tissues. These results contrast those we reported previously using the weaker CaMV 35S promoter driving adc expression. mRNA measurements and ADC enzyme activity were consistently higher (P < 0.01) in all tissues expressing pUbiadcs compared to equivalent tissues engineered with 35Sadc. Our findings are consistent with a threshold model which postulates that high adc expression leading to production of Put above a basal level is necessary to generate a big enough metabolic pool to trigger PA flux through the pathway leading to an increase in the concentration of Spd and Spm. This can be best accomplished by a strong constitutive promoter driving adc. We discuss our results in the context of flux through the PA pathway and its impact on morphogenesis.

Avena↗