Hepatocellular carcinoma (HCC) is the major primary malignant tumor in the human liver, but the molecular changes leading to liver cell transformation remain largely unknown. The Wnt-beta-catenin pathway is activated in colon cancers and some melanoma cell lines, but has not yet been investigated in HCC. We have examined the status of the beta-catenin gene in different transgenic mouse lines of HCC obtained with the oncogenes c-myc or H-ras. Fifty percent of the hepatic tumors in these transgenic mice had activating somatic mutations within the beta-catenin gene similar to those found in colon cancers and melanomas. These alterations in the beta-catenin gene (point mutations or deletions) lead to a disregulation of the signaling function of beta-catenin and thus to carcinogenesis. We then analyzed human HCCs and found similar mutations in eight of 31 (26%) human liver tumors tested and in HepG2 and HuH6 hepatoma cells. The mutations led to the accumulation of beta-catenin in the nucleus. Thus alterations in the beta-catenin gene frequently are selected for during liver tumorigenesis and suggest that disregulation of the Wnt-beta-catenin pathway is a major event in the development of HCC in humans and mice.

Hepatocyte transplantation might represent a potential therapeutic alternative to liver transplantation in the future; however, transplanted cells have a limited capacity to repopulate the liver, as they do not proliferate under normal conditions. Recently, studies in urokinase (uPA) transgenic mice and in fumarylacetoacetate hydrolase (FAH)-deficient mice have shown that the liver can be repopulated by genetically engineered hepatocytes harboring a selective advantage over resident hepatocytes. We have reported that transgenic mice expressing human Bcl-2 in their hepatocytes are protected from Fas/CD95-mediated liver apoptosis. We now show that Bcl-2 transplanted hepatocytes selectively repopulate the liver of mice treated with nonlethal doses of the anti-Fas antibody Jo2. FK 506 immunosuppressed mice were transplanted by splenic injection with Bcl-2 hepatocytes. The livers of female recipients were repopulated by male Bcl-2 transgenic hepatocytes, as much as 16%, after 8 to 12 administrations of Jo2. This only occurred after anti-Fas treatment, confirming that resistance to Fas-induced apoptosis constituted the selective advantage of these transplanted hepatocytes. Thus, we have demonstrated a method for increasing genetic reconstitution of the liver through selective repopulation with modified transgenic hepatocytes, which will allow optimization of cell and gene therapy in the liver.

Fas ligand (CD95L) and tumor necrosis factor-α (TNF-α) are pivotal inducers of hepatocyte apoptosis. Uncontrolled activation of these two systems is involved in several forms of liver injury. Although the broad antiapoptotic action of Bcl-2 and Bcl-xL has been clearly established in various apoptotic pathways, their ability to inhibit the Fas/CD95- and TNF-α-mediated apoptotic signal has remained controversial. We have demonstrated that the expression of BCL-2 in hepatocytes protects them against Fas-induced fulminant hepatitis in transgenic mice. The present study shows that transgenic mice overexpressing[Formula: see text]in hepatocytes are also protected from Fas-induced apoptosis in a dose-dependent manner. Bcl-xL and Bcl-2 were protective without any change in the level of endogenous[Formula: see text]or Bax and inhibited hepatic caspase-3-like activity. In vivo injection of TNF-α caused massive apoptosis and death only when transcription was inhibited. Under these conditions,[Formula: see text]mice were partially protected from liver injury and death but PK-BCL-2 mice were not. A similar differential protective effect of Bcl-xL and Bcl-2 transgenes was observed when Fas/CD95 was activated and transcription blocked. These results suggest that apoptosis triggered by activation of both Fas/CD95 and TNF-α receptors is to some extent counteracted by the transcription-dependent protective effects, which are essential for the antiapoptotic activity of Bcl-2 but not of Bcl-xL. Therefore, Bcl-xL and Bcl-2 appear to have different antiapoptotic effects in the liver whose characterization could facilitate their use to prevent the uncontrolled apoptosis of hepatocytes.

The role of the hepatitis B virus protein HBx in liver cell proliferation and apoptosis remains controversial. Using a transgenic mouse model, we have recently shown that HBx stimulates the apoptotic turnover of hepatocytes, independently of p53. In this paper, we tested whether the proapoptotic function of HBx can interfere with Bcl-2 during hepatic apoptosis in vivo. HBx transgenic mice were crossed with PK-hBcl-2 mice that are protected against Fas killing by constitutive overexpression of Bcl-2 in hepatocytes. In a lethal challenge with Fas antibodies, HBx expressed at low levels restored sensitivity to Fas-mediated apoptosis and fulminant hepatic failure in mice overexpressing Bcl-2. Furthermore, cytochrome c release from mitochondria and caspase 3 activation were restored to normal levels in HBx/Bcl-2 mice during transduction of the Fas signal. Thus, the proapoptotic activity of HBx overcomes or bypasses the inhibitory e ect of Bcl-2 against Fas cytotoxicity. This e ect was not apparently mediated through downregulation of the PK-hBcl-2 transgene or via delocalization of the Bcl-2 protein, and a direct interaction of HBx with Bcl-2, Bcl-X L or Bax could not be evidenced in yeast two-hybrid assays. We further show that apoptosis induced by ectopic expression of HBx is associated with mitochondrial membrane alterations and caspase 3 activation. Our data indicate that the dominant function of HBx upon Bcl-2-regulated control of apoptosis might play an important role in the pathogenesis of chronic hepatitis B.

Notch signaling is a highly conserved pathway involved in cell fate choice during development with Delta and Jagged constituting the two evolutionary conserved families of Notch ligands. These ligands are transmembrane proteins with conserved biochemical structure that share their receptors and signal through a common mechanism.

OBJECTIVES: To determine the frequency and prognosis of invasive pulmonary aspergillosis in critically ill patients with severe influenza pneumonia. DESIGN: Retrospective multicenter cohort study. SETTING: Five French ICUs. PATIENTS: Patients with influenza admitted to ICU between 2009 and 2018. MEASUREMENTS AND MAIN RESULTS: Of the 524 patients admitted for severe influenza diagnosed with a positive airway reverse-transcriptase polymerase chain reaction test, 450 (86%) required mechanical ventilation. A lower respiratory tract sample yielded with Aspergillus (Asp+) in 28 patients (5.3%). Ten patients (1.9%) were diagnosed with putative or proven invasive pulmonary aspergillosis, based on the validated AspICU algorithm. A multivariate model was built to identify independent risk factors for Aspergillus-positive pulmonary culture. Factors independently associated with Aspergillus-positive culture were liver cirrhosis (odds ratio = 6.7 [2.1–19.4]; p < 0.01), hematologic malignancy (odds ratio = 3.3 [1.2–8.5]; p = 0.02), Influenza A(H1N1)pdm09 subtype (odds ratio = 3.9 [1.6–9.1]; p < 0.01), and vasopressor requirement (odds ratio = 4.1 [1.6–12.7]; p < 0.01). In-hospital mortality of Asp+ patients was 36% versus 21% in patients without Aspergillus-positive pulmonary culture (p = 0.09). CONCLUSIONS: In this large retrospective multicenter cohort of critically ill patients, putative invasive pulmonary aspergillosis according to AspICU algorithm was a relatively rare complication of influenza. Patients at higher risk of Aspergillus pulmonary colonization included those with liver cirrhosis, hematologic malignancy, H1N1pdm09 influenza A virus, and requiring vasopressors. Our results provide additional data on the controversial association between severe influenza and invasive pulmonary aspergillosis. Reaching a consensual definition of invasive pulmonary aspergillosis becomes mandatory and confers further prospective research.

Heat-killed Brucella abortus (HBa) has been proposed as a carrier for therapeutic vaccines for individuals with immunodeficiency, due to its abilities to induce interleukin-2 (IL-2) and gamma interferon (IFN-␥) in both CD4؉ and CD8 ؉ T cells and to upregulate antigen-presenting cell functions (including IL-12 production). In the current study, we investigated the ability of HBa or lipopolysaccharide isolated from HBa (LPS-Ba) to elicit ␤-chemokines, known to bind to the human immunodeficiency virus type 1 (HIV-1) coreceptor CCR5 and to block viral cell entry. It was found that human peripheral blood mononuclear cells secreted ␤-chemokines following stimulation with HBa, and this effect could not be blocked by anti-IFN-␥ neutralizing antibodies. Among purified T cells, macrophage inflammatory protein 1␣ and 1␤ (MIP-1␣ and MIP-1␤, respectively) secretion was observed primarily in human CD8؉ T cells. The kinetics of ␤-chemokine induction in T cells were slow (3 to 4 days). The majority of ␤-chemokine-producing CD8 ؉ T cells also produced IFN-␥ following HBa stimulation, as determined by triple-color intracellular staining. A significant number of CD8 ؉ T cells contained stored MIP-1␤ that was released after HBa stimulation. Both HBa and LPS-Ba stimulated high levels of MIP-1␣ and MIP-1␤ production in elutriated monocytes and even higher levels in macrophages. In these cells, ␤-chemokine mRNA was upregulated within 30 min and proteins were secreted within 4 h of stimulation. The monocyte-and macrophage-derived ␤-chemokines were sufficient to block CCR5-dependent HIV-1 envelope-mediated cell fusion. These data suggest that, in addition to the ability of HBa to elicit antigen-specific humoral and cellular immune responses, HBa-conjugated HIV-1 proteins or peptides would also generate innate chemokines with antiviral activity that could limit local viral spread during vaccination in vivo.The discovery that several ␤-chemokines (i.e., macrophage inflammatory proteins 1␣ and 1␤ [MIP-1␣ and MIP-1␤, respectively] and RANTES) secreted by short-term human CD8 ϩ cell lines can effectively block infection of human peripheral blood mononuclear cells (PBMCs) with macrophage-

The use of gene-modified tumor cells as a strategy for active immunotherapy is currently undergoing intensive fundamental and clinical research. Most clinical trials use gamma-ray-irradiated tumor cells as vaccine, although little is known about the effects of irradiation on the immunogenicity of tumor cells. In particular, no data have been reported so far concerning the effects of gamma-ray irradiation on the expression of B7 molecules in tumor cells. In this paper, we show a neoexpression of the B7.1 molecule after gamma-ray irradiation in tumor cell lines from different tissues, while the B7.2 molecule remains unexpressed in all the cell lines tested. Furthermore, the induction of B7.1 molecule membrane expression after irradiation is shown to result from the neoexpression of B7.1 mRNA, and to be reproduced with H2O2 oxidative stress. These data could explain the enhanced immunogenicity of many tumor cells after irradiation, and could lead to new immunotherapy protocols.