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04). In multivariate analysis, FADD؊/low protein expression was independently associated with a poor EFS and overall survival (P ‫؍‬ 0.002 and P ‫؍‬ 0.026, respectively). Importantly, FADD ؊/low protein expression predicted poor EFS even in patients with standard-or good-risk AML (P ‫؍‬ 0.009). Thus, we identified low or absent expression of the FADD protein in leukemic cells at diagnosis as a poor independent prognostic factor that can predict worse clinical outcome even for patients with standard-or good-risk AML.

We previously compared by microarray analysis gene expression in rheumatoid arthritis (RA) and osteoarthritis (OA) tissues. Among the set of genes identified as a molecular signature of RA, clusterin (clu) was one of the most differentially expressed. In the present study we sought to assess the expression and the role of CLU (mRNA and protein) in the affected joints and in cultured fibroblast-like synoviocytes (FLS) and to determine its functional role. Quantitative RT-PCR, Northern blot, in situ hybridization, immunohistochemistry, and Western blot were used to specify and quantify the expression of CLU in ex vivo synovial tissue. In synovial tissue, the protein was predominantly expressed by synoviocytes and it was detected in synovial fluids. Both full-length and spliced isoform CLU mRNA levels of expression were lower in RA tissues compared with OA and healthy synovium. In synovium and in cultured FLS, the overexpression of CLU concerned all protein isoforms in OA whereas in RA, the intracellular forms of the protein were barely detectable. Transgenic overexpression of CLU in RA FLS promoted apoptosis within 24 h. We observed that CLU knockdown with small interfering RNA promoted IL-6 and IL-8 production. CLU interacted with phosphorylated IκBα. Differential expression of CLU by OA and RA FLS appeared to be an intrinsic property of the cells. Expression of intracellular isoforms of CLU is differentially regulated between OA and RA. We propose that in RA joints, high levels of extracellular CLU and low expression of intracellular CLU may enhance NF-κB activation and survival of the synoviocytes.

Downregulation of proapoptotic molecules like Fas or caspase 8, or upregulation of antiapoptotic molecules like FLICE inhibitory protein has been suggested to be a regulatory mechanism set up by tumor cells to block the death signal received via death receptors. In an in-depth study of the Fas/FasL-signaling pathway in thyroid tumor development, we have demonstrated that tumor cells specifically downregulate the multideath receptor adapter Fas-associated death domain (FADD). The regulation of FADD expression occurred only at the protein level. Furthermore, in the absence of FADD, Fas-signaling resulted in accelerated growth of thyrocytes. Since thyrocytes also acquired FasL expression during tumor development, the absence of FADD protein could lead to greater resistance to numerous death receptor-mediated apoptosis, stimulation of their own proliferation through Fas/FasL interaction, and the capacity to counter-attack the infiltrating lymphocytes.

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Late-onset neutropenia following rituximab results from a hematopoietic lineage competition due to an excessive BAFF-induced B-cell recoveryRituximab is used in the treatment of lymphoma and autoimmune diseases, for which late-onset neutropenia (LON) were reported. LON-related mechanisms remain unclear. To obtain insights into the mechanisms, we assessed serum, peripheral blood and bone marrow (BM) samples of a patient with LON. Factors classically associated with neutropenia such as anti-neutrophil antibodies, T-LGL, soluble Fas Ligand were not detectable. We then evaluated the kinetics of various cytokines involved in B-cell and granulocyte homeostasis. We found that LON is related to a lack of granulopoiesis in the BM that coincides with a very high level of BAFF, a strong stimulator of B-cell recovery, and hypothesized a hematopoietic lineage competition due to an excessive B-cell recovery in the BM by promotion of B-cell lymphopoiesis over granulopoiesis within common developmental niches. Assessment of serum BAFF levels following rituximab could detect patients at risk of developing LON.Haematologica 2007; 92:(2)e20-e23 IntroductionRituximab, an anti-CD20 monoclonal antibody, is increasingly used in the treatment of lymphoma and autoimmune diseases. CD20 is expressed on malignant B-cells, normal differentiated B-cells and pre-B-cells, but not on stem cells and granulocyte precursors. Late-onset neutropenia following rituximab (LON) have been reported, 1-7 occurring 1 to 6 months after last rituximab infusion, as being severe (<0.5x10 9 /L), spontaneously reversible and without life-threatening infections.Several studies suggest that LON could be related to an excess of T-Large Granular Lymphocyte (LGL) in the bone marrow (BM) and peripheral blood (PB) which express and secrete large amounts of Fas and Fas Ligand (FasL) leading to apoptosis of mature neutrophils, 4 or to a production of autoantibodies binding to the neutrophil surface during recovery of a new immune repertoire. 2,6 On the other hand, a recent study suggests that LON is not related to circulating factors but to perturbations of Stromal-derived Factor 1 (SDF-1) and granulopoiesis homeostasis during B-cell recovery.7 This is reinforced by previous studies showing the hypocellularity of the marrow at the time of LON [1][2][3]6 and the absence of anti-neutrophil antibodies in the serum or T-LGL in the PB., 2,6,7 We report here that LON is related to a lack of granulopoiesis in the BM that coincides with the time of maximum B-cell depletion in PB, and proposed the hypothesis that LON is due to a hematopoietic lineage competition in the BM by promotion of B-cell lymphopoiesis over granulopoiesis within common developmental niches. Study designCase report. /L). At admission on day 84, blood tests revealed a severe neutropenia (0.2x10 9 /L), with normal hemoglobin level and platelet count, but the exact time from last treatment to the development of neutropenia could not be precisely determined with the available data. The serum monoclonal component...

FADD (Fas Associated protein with Death Domain) is a key adaptor molecule transmitting the death signal mediated by death receptors. In addition, this multiple functional protein is implicated in survival/proliferation and cell cycle progression. FADD functions are regulated via cellular sublocalization, protein phosphorylation, and inhibitory molecules. In the present review, we focus on the role of the FADD adaptor in cancer. Increasing evidence shows that defects in FADD protein expression are associated with tumor progression both in mice and humans. Better knowledge of the mechanisms leading to regulation of FADD functions will improve understanding of tumor growth and the immune escape mechanisms, and could open a new field for therapeutic interventions. The FADD moleculeThe FADD gene is located on chromosome 11q13.3 in humans and 7 in mice [1]. Mutations in the FADD gene containing locus are frequently observed in human malignancies [2]. For instance, the 11q13 region contains the fibroblast growth factor 3 and 4 genes which are coamplified in melanoma. It also includes the multiple endocrine neoplasia I gene whose mutation leads to tumor development of several endocrine glands including thyroid. Moreover, two genes implicated in leukemia are found in this locus: NUMA1 which is translocated in acute promyelocytic leukemia, and BCL1 which is located very close to the FADD gene and is mutated in B-cell leukemia/lymphoma. Although FADD has a central role in multiple receptor-induced cell death as discussed hereafter, no mutation of the FADD gene itself has been reported so far.Human and mouse FADD genes have the same quite simple organization consisting of two exons (286 bp and 341 bp in humans; 332 bp and 286 bp in mice) separated by a unique intron of approximately 2 kb. Interestingly, no cap site was reported on the human FADD mRNA [1], suggesting a particular regulation of FADD mRNA translation, although this topic has not been further investigated.Human and mouse FADD proteins are very similar (Figure 1). They consist of 208 and 205 amino acids (AA) respectively, and share 80% similarity and 68% identity [3]. FADD mRNA and protein are almost ubiquitously expressed in fetal and adult tissues, both in humans and mice [4]. Two domains are particularly well conserved between species: the death domain (DD) at the COOHterminus of the protein, and the death effector domain (DED) at the NH2-terminus of the protein [5,6]. Both domains play a crucial role in transducing the apoptotic signal mediated by death receptors. Furthermore, a single serine (Ser) phosphorylation site essential for determining cell cycle progression is conserved in both species (human Ser 194 [7] and mouse Ser 191 [8]).

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.