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Biomedical subjects

M Fabre

Publications and source records attributed to M Fabre.

At least 37 records · Page 2Linked to original sources
PubMed2001

Transgenic expression of CD95 ligand on thyroid follicular cells confers immune privilege upon thyroid allografts.

Constitutive Fas ligand (FasL) expression by specialized cells in the body participates in the immune privilege status of tissues containing these cells. This property has been used to prevent rejection of allogeneic grafts. Nevertheless, the mechanism responsible for such protection has not been fully elucidated. Unfortunately, grafting of FasL transgenic (TG) tissues has been unsuccessful. We have generated TG mice expressing FasL (soluble + membrane bound) on thyroid follicular cells (TFC), and used them to show that ectopic FasL expression prevents thyroid allograft rejection. FasL expression on TFC led to markedly decreased anti-allogeneic, cytotoxic, and helper T lymphocyte activities. The alloantibody response in TG thyroid recipients was either completely inhibited or switched toward a T2-Ab response. Surprisingly, the beneficial effect of FasL on TG thyroid grafts was abolished by host CD4(+) T cell depletion. Host CD8(+) T cell depletion improved nontransgenic (NTG), but not TG graft survival. Altogether, our results suggest that FasL-induced tolerance is concomitant with a move away from a T1 type response, and a CD4 T cell-mediated regulation of the allocytotoxic T cell response. These results were dependent upon the level of FasL expression on TFC, in that low expression of FasL led to a less marked effect compared with the effect observed with high expression of FasL. These results provide some insight into the role of FasL in regulating destructive alloimmune responses in the case of whole organ grafting, and they have important implications for the development of FasL-based immunotherapy in organ transplantation.

Animals↗
PubMed2001

Hepatomegaly in transgenic mice expressing an oncogenic form of beta-catenin.

Inappropriate activation of the Wnt/beta-catenin signaling, resulting mainly from activating mutations of the beta-catenin gene, has been implicated recently in the development of hepatocellular carcinoma (HCC). We have generated transgenic mice expressing an oncogenic form of beta-catenin in their hepatocytes to analyze the effect of deregulated beta-catenin signaling on liver homeostasis. These mice rapidly developed hepatomegaly soon after birth, with livers three to four times heavier than those of nontransgenic littermates. The liver cell hyperplasia resulted from increased cell proliferation without any compensatory apoptosis. Although the genes encoding c-myc and cyclin D1 are potential targets of the beta-catenin signaling pathway, neither of them was overexpressed in the hyperplastic livers of beta-catenin transgenic mice. Thus, the key target genes of the beta-catenin signaling pathway in the liver remain to be identified.

Animals↗
PubMed2001

Fas/CD95 pathway induces mouse liver regeneration and allows for highly efficient retrovirus-mediated gene transfer.

Stable gene transfer into hepatocytes has been proposed to compensate for genetic deficiencies that affect liver function, or to deliver diffusible factors into the circulation. This strategy can be achieved using retroviral vectors; however, cell division must occur. We describe a simple and reproductive method that enables the induction of hepatocyte replication in a controlled fashion, thus allowing an efficient in vivo retroviral liver transduction that is applicable to mouse models of human genetic disorders. The approach is based on liver susceptibility to apoptosis via the Fas/CD95 pathway. We show that, 4 days following a single Fas agonist antibody (JO2) injection, hepatocyte replication occurs, the intensity of which is correlated with the level of the induced hepatic cytolysis. This treatment enables in vivo liver transduction, and its efficiency also correlates with the level of hepatic cytolysis. When recombinant retroviral vectors were infused intravenously during the period of hepatocyte replication, 15.4% +/- 1.7% of the hepatocytes were transduced, reaching up to 32.5%.

Alanine Transaminase↗
PubMed2001

Bone marrow involvement in lymphomas with hemophagocytic syndrome at presentation: a clinicopathologic study of 11 patients in a Western institution.

Hemophagocytic syndrome (HPS) is a clinicopathologic syndrome that can reveal a non-Hodgkin's lymphoma. The pathologic features of lymphoma associated with HPS remain ill defined. We studied 11 lymphomas associated with HPS on initial bone marrow biopsies, consecutively diagnosed during a 6-year period in a Western institution. There were seven diffuse large B-cell lymphomas (DLBCLs), three T-cell lymphomas (one peripheral T-cell lymphoma unspecified, two hepatosplenic gammadelta T-cell lymphomas [HS gammadeltaTLs]), and one aggressive NK-cell lymphoma/leukemia (NKL). These lymphomas shared common clinicopathologic features with a systemic presentation, a poor outcome (nine patients died within 2 years), and a mild interstitial lymphoid infiltrate of the bone marrow at presentation in nine patients. This equivocal lymphoma infiltrate was blending with normal hematopoietic cells, and CD20 and CD3 immunolabelings were essential for its detection. A high number of reactive T (CD3+) cells, most often with a predominant cytotoxic (CD8+ TiA1+) phenotype, was present in all DLBCLs. By in situ hybridization, Epstein-Barr virus was detected in neoplastic cells of three cases (one DLBCL, one HS gammadeltaTL, and one NKL), which also showed serum viral DNA. Polymerase chain reaction studies disclosed HHV6 DNA sequences in tumor tissues of two DLBCLs, whereas HHV8 DNA was not detected. Because tumor mass indicative of lymphoma was not striking in most patients, bone marrow biopsy appears to be of great value for the diagnosis of an HPS-associated lymphoma, which may be, in Western patients, of B- as well as T- or NK-cell type. Immunostaining for CD3 and CD20 is essential to identify the common subtle lymphoma involvement. Together with a better understanding of the pathogenic processes, an early diagnosis may improve the prognosis of HPS-associated lymphoma.

Adolescent↗
PubMed2001

[Macronodules, dysplastic nodules and cirrhosis].

For a few years, many descriptions and studies have been published regarding precancerous nodular liver lesions. As a result, several terms and classifications have been proposed leading to poor reproducibility. In 1995, an International Working Party defined nodular lesions called low grade and high grade dysplastic nodules. A good correlation between clinical, radiological and pathological lesions was then obtained. This article summarizes the histopronostic features of the nodules observed in cirrhotic liver, and attempts to specify the diagnostic criteria to distinguish dysplastic from regenerative macronodules and hepatocellular carcinomas.

Biopsy↗
PubMed2001

[Primary uterine and vulvar Ewing's sarcoma/peripheral neuroectodermal tumors in children: two unusual locations].

Two genital cases of Ewing's sarcoma/peripheral neuroectodermal tumor in 14 and 15 year old teenagers are reported. They arose in uteri and vulva, as small round cell tumors with some rosette-like formations and intense membranous immunoreactivity for CD99. The EWS/FLI-1 transcript was present in the vulvar tumor. Under chemotherapy, uterine tumor outcome was fatal within 9 months. The vulvar lesion was treated by surgery and chemotherapy, without relapse after 7 months. Likewise to these 2 cases, the literature seems to indicate different prognosis for uterine and vulvar tumors.

12E7 Antigen↗
PubMed2001

[Gastric epithelioid angiosarcoma, a biopsy diagnostic pitfall].

We report the case of a 70-year-old man who presented a bulky gastric mass. The diagnosis of poorly differenciated adenocarcinoma was made on the biopsy. On surgical specimen, the final diagnosis of gastric angiosarcoma with secondary intestinal involvement was established. The patient did not respond to chemotherapy and died 8 months later. The diagnosis was difficult because of epithelioid areas which expressed both cytokeratin and vascular antigens. Human herpesvirus 8 previously detected in some soft tissue angiosarcoma was not found by polymerase chain reaction.

Aged↗
PubMed2000

The 18q21 region in colorectal and pancreatic cancer: independent loss of DCC and DPC4 expression.

UNLABELLED: The 18q21 region is frequently altered in gastrointestinal tumors. Three candidate tumor suppressor genes have been identified in it: DCC, Smad4/DPC4 and Smad2; the mechanisms involving their inactivation have not been completely elucidated. In this study, genetic losses at 18q21 and expression of DCC and DPC4 in colorectal (n=12) and pancreatic (n=16) cell lines and in colorectal tissues (n=10) were analyzed. The status of the 18q21 region was assessed using microsatellite analysis and duplex PCR of exonic sequences; expression was analyzed by RT-PCR; mutational analysis of DPC4 cDNA was performed in selected cases. Homozygous losses of microsatellite markers at 18q21 were not observed in colon or pancreas lines; however, a higher proportion of apparent homozygosity than expected was found. DCC and DPC4 transcripts were detected in 11/12 and 12/12 colorectal cancer lines, respectively. In tumors, homozygous losses at 18q21 were detected in three cases, without affecting DCC. All tumors retained DCC and DPC4 mRNA expression. In pancreatic lines, DPC4 was inactivated through homozygous deletion (n=5), intragenic mutation (n=3), and lack of protein (n=2). IN CONCLUSION: (1) microsatellite analysis does not provide adequate information regarding homozygous losses at 18q21; (2) approximately 65% of pancreas cancer lines show inactivation of DPC4; and (3) loss of DCC and DPC4 occur independently.

Aged↗
PubMed2000

Therapeutic liver repopulation in a mouse model of hypercholesterolemia.

Liver repopulation constitutes an attractive approach for the treatment of liver disorders or of diseases requiring abundant secretion of an active protein. We have described previously a model of selective repopulation of a normal liver by Fas/CD95-resistant hepatocytes, in which we achieved up to 16% hepatocyte repopulation. In the present study, we investigated the therapeutic efficacy of this strategy. With this aim, apolipoprotein E (ApoE) knockout mice were transplanted with Fas/CD95-resistant hepatocytes which constitutively express ApoE. Transplanted mice were submitted to weekly injections of non-lethal doses of the Fas agonist antibody Jo2. After 8 weeks of treatment, we obtained up to 30% of the normal level of plasma ApoE. ApoE secretion was accompanied by a drastic and significant decrease in total plasma cholesterol, which even fell to normal levels. Moreover, this secretion was sufficient to markedly reduce the progression of atherosclerosis. These results demonstrate the efficacy of this repopulation approach for correcting a deficiency in a protein secreted by the liver.

Animals↗
PubMed2000

Activation of beta-catenin in epithelial and mesenchymal hepatoblastomas.

Wnt/beta-catenin signaling is frequently activated in cancer cells by stabilizing mutations of beta-catenin or loss-of-function mutations of the APC tumor suppressor gene. We have analysed the role of beta-catenin in the pathogenesis of hepatoblastoma (HB), an embryonic liver tumor occurring mainly in children under 2 years of age. Sequence analysis of the beta-catenin NH2-terminal domain in 18 epithelial and mixed HBs revealed missense mutations in the GSK3beta phosphorylation motif or interstitial deletions in 12 tumors (67%). In the remaining cases, no truncating mutation of APC could be evidenced. Immunohistochemical analysis of beta-catenin in 11 HBs demonstrated nuclear/cytoplasmic accumulation of the protein in all tumors analysed, with predominant nuclear beta-catenin immunostaining in undifferentiated cells. Membranous beta-catenin localization was preserved only in fetal-type tumoral hepatocytes and was associated with E-cadherin expression. Moreover, we show that beta-catenin is aberrantly overexpressed in a large spectrum of tumor components, including hepatocyte-like cells at various differentiation stages and heterologous elements such as squamous, osteoid and chrondroid tissues, and in occasional other mesenchymally-derived cells. These data strongly suggest that activation of beta-catenin signaling is an obligatory step in HB pathogenesis, and raise the possibility that it interferes with developmental signals that specify different tissue types at early stages of hepatic differentiation.

Biological Transport↗
PubMed2000

[Renal inflammatory pseudotumor manifesting as a prolonged fever].

INTRODUCTION: Inflammatory pseudo-tumors (IPT) are benign neoplasms associated with local or general manifestations. Renal localization seems exceptional, and no case of fever of unknown origin caused by renal inflammatory pseudo-tumors have been reported. EXEGESIS: The authors report the case of a man presenting fever of unknown origin and inflammatory syndrome. Computerized tomography showed a renal mass. Nephrectomy was performed, and renal inflammatory pseudo-tumor was diagnosed. After surgical exeresis, the clinical and biological abnormalities vanished. CONCLUSION: This rare diagnosis must be considered in these situations. The outcome is excellent.

Biopsy, Needle↗
PubMed2000

Efficient suicide gene therapy of transduced and distant untransduced ovary tumors is correlated with significant increase of intratumoral T and NK cells.

Gene therapy using herpes simplex type 1 thymidine kinase gene (HSV1-TK) transfer followed by ganciclovir (GCV) treatment has revealed an important intratumoral and regional bystander effect that is at least partly immune-mediated. The aim of this work was to study the modifications of T lymphocyte subpopulations in a model of distant bystander effect occurring between ovary tumors. Bilateral ovarian tumors were generated in 21 WKY rats by injection in the ovarian pouch of either parental or HSV1-TK-expressing DWA-OC-1 ovarian cancer cells. After 14 days, rats were treated for two weeks with GCV (75 mg/kg x 2/d) or saline. All rats were killed at day 29 for pathological examination. The tumor-infiltrating mononuclear cells were analyzed by semi-quantitative immunohistochemistry. As compared to rats receiving saline, GCV-treated animals exhibited a complete disappearance of the HSV1-TK+ tumors with residual fibrotic scars (ovary weights: 0.46 +/- 0.4 g vs 10.11 +/- 1.5 g, P < 0.001). Interestingly, the contralateral HSV1-TK negative tumor showed a significant regression (12.39 +/- 1.93 g vs 22.24 +/- 237 g, P < 0.014). Furthermore, a lower incidence of tumoral ascitis was found in the GCV-receiving group (20% vs 90% P < 0.02). Within both TK- and TK+ tumors, there was a significant increase of CD4+, CD8+ and NK cells in the GCV-treated group compared to the saline-treated group. This study thus indicates that a distant bystander effect not only acts between close tumors within a given organ such as the liver, but also between more distant tumors in the peritoneal cavity. This effect is associated with significant infiltration of the tumor by immune system cells, supporting the notion that the distant bystander effect is immune-mediated.

Animals↗
PubMed2000

A preclinical model of hepatocyte gene transfer: the in vivo, in situ perfused rat liver.

Delivering retroviruses targeted to hepatocytes in vivo involves the injection of retroviruses directly into the portal vein. The aim of this work was to establish a clinically relevant system for retrovirus-mediated gene transfer in a new model of in vivo, in situ perfused rat liver and to study the transgene expression. At 24 h after partial hepatectomy, the liver was completely excluded from the splanchnic circulation using an extracorporeal shunt. Two independent normothermal, oxygenated perfusion systems were used. First, liver perfusion was carried out with a recirculating system (1 h). Culture supernatant containing retroviruses (1.5 x 10(8) ffu/ml, beta-galactosidase gene) was used as perfusate. Then the liver perfusion was maintained for more 30 min in a single liver passage system using culture medium without retroviruses as perfusate. High hepatocyte transduction rates (up to 34.4%) were obtained. PCR analysis showed no provirus in extrahepatic organs. Viral titrations performed simultaneously (inflow and outflow liver lines) showed that after 1 h of perfusion (up to 30 successive liver passages) retroviruses were still detected in the liver outflow perfusate (up to 2.0 x 10(7) ffu/ml). Washing the liver for 30 min dramatically decreased the leakage of retroviruses in the outflow. In order to be of clinical use, the injection of retroviruses targeted to hepatocytes in vivo should be done while the liver is completely excluded from the splanchnic circulation to avoid any extrahepatic retrovirus diffusion.

Animals↗
PubMed2000

Zenker's diverticulum in childhood: a new case.

Zenker's diverticulum (ZD) is a very rare pathology in childhood and to date only few pediatric cases have been reported in literature. Herein we report on a case of ZD with cervical abscess formation and oral purulent drainage in a 6-year old girl with severe malnutrition. Diverticulectomy was performed as surgical treatment. The patient is free of symptoms after two years' follow-up.

Age of Onset↗