In the present study, we show that Fas receptor ligation or cellular treatment with synthetic C 6 -ceramide results in activation or phosphorylation, respectively, of the small G-protein Rac1, Jun N-terminal kinase (JNK)/ p38 kinases (p38-K), and the transcription factor GADD153. A signaling cascade from the Fas receptor via ceramide, Ras, Rac1, and JNK/p38-K to GADD153 is demonstrated employing transfection of transdominant inhibitory N17Ras, N17Rac1, c-Jun, or treatment with a specific p38-K inhibitor. The critical function of this signaling cascade is indicated by prevention of Fas-or C 6 -ceramide-induced apoptosis after inhibition of Ras, Rac1, or JNK/p38-K.

Purpose: The L1adhesion molecule (CD171) is overexpressed in human ovarian and endometrial carcinomas and is associated with bad prognosis. Although expressed as a transmembrane molecule, L1is released from carcinoma cells in a soluble form. Soluble L1is present in serum and ascites of ovarian carcinoma patients.We investigated the mode of L1cleavage and the function of soluble L1. Experimental Design: We used ovarian carcinoma cell lines and ascites from ovarian carcinoma patients to analyze soluble L1and L1cleavage byWestern blot analysis and ELISA. Results: We find that in ovarian carcinoma cells the constitutive cleavage of L1proceeds in secretory vesicles. We show that apoptotic stimuli like C 2 -ceramide, staurosporine, UV irradiation, and hypoxic conditions enhance L1-vesicle release resulting in elevated levels of soluble L1. Constitutive cleavage of L1 is mediated by a disintegrin and metalloproteinase 10, but under apoptotic conditions multiple metalloproteinases are involved. L1cleavage occurs in two types of vesicles with distinct density features: constitutively released vesicles with similarity to exosomes and apoptotic vesicles. Both types of L1-containing vesicles are present in the ascites fluids of ovarian carcinoma patients. Soluble L1 from ascites is a potent inducer of cell migration and can trigger extracellular signal-regulated kinase phosphorylation. Conclusions: We suggest that tumor-derived vesicles may be an important source for soluble L1 that could regulate tumor cell function in an autocrine/paracrine fashion.

Infants with very low birth weights have less need of transfusions if given epoetin beta during the first six weeks of life (250 IU per kilogram three times a week). We recommend early epoetin treatment for all such infants, but further studies of nutrition and iron supplementation during treatment are needed.

IntroductionThere is now clear evidence that CD4 ϩ T cells contain a population of naturally immunosuppressive T cells characterized by constitutive expression of CD25, CTLA-4, and FOXP3. 1 Because not all potentially autoreactive T cells are deleted in the thymus, 2,3 peripheral control of T-cell responses by naturally occurring CD4 ϩ CD25 ϩ FOXP3 ϩ immunoregulatory T cells (T regs ) is crucial to prevent autoimmunity. 1 Depletion of T regs contributes to the induction of severe autoimmune diseases in animal models, and several studies have reported a defect of T regs in various human autoimmune diseases. 1,4,5 Despite extensive research to unravel the immunosuppressive function of T reg , the exact molecular mechanism of immunosuppression is still elusive. Promising targets for pharmacologic mimicking of T regs function remain undefined. Consequently, direct use of T regs for therapy is currently under examination. Therapeutic expansion or depletion of T regs with defined antigen specificity offers new treatment options for human diseases. 6 Because accumulation of T regs has been shown to be detrimental in cancer, 7 new insights into mechanisms of T reg homeostastis are required.To gain new insight into the modulation of T reg numbers as well as their antigen specificity, the development of natural T regs during ontogeny and in the adult needs to be explored. The peripheral T reg compartment consists mainly of thymus-derived T regs . 1 However, under specific circumstances T regs can also be generated out of conventional T cells (T convs ) (eg, if the antigen is targeted to immature dendritic cells [DCs]). [8][9][10] It has yet to be established how much "converted" T regs contribute to the total number of T regs in the periphery of adult mice and humans.At a given time, the overall number of T regs is defined by a balance of generation and demise of T regs . At the end of an immune reaction, T cells are depleted by apoptosis. Activation-induced cell death (AICD) through CD95/CD95L has been described as such an apoptosis-inducing mechanism. 11 While naive T cells are CD95 Ϫ and resistant to apoptosis induction, activated T cells (CD45RO hi ) up-regulate CD95 and become sensitive to apoptosis. Upon T-cell receptor (TCR) restimulation, activated effector T cells (T effs ) up-regulate CD95L and induce AICD through crosslinking of CD95 by CD95L. AICD eliminates T effs after an immune response and contributes to T-cell homeostasis. We have previously shown that most T regs constitutively express CD95 and can easily be killed via crosslinking of this death receptor by CD95L. 12 Together with the fact that most T regs express high levels of CD45RO, we contributed expertise in microarray analysis; J.P. contributed clinical samples; P.K. analyzed data and assisted in writing the paper; O.L. contributed clinical samples and assisted in writing the paper; and E.S.-P. designed research and wrote the paper.The online version of this article contains a data supplement. For personal use only. on April 5, 2019. by guest www....