Inhibition of in vitro and in vivo T cell responses by recombinant human Tim-1 extracellular domain proteins.

Members of the T cell, Ig domain and mucin domain (Tim) family of proteins have recently been implicated in the control of T cell-mediated immune responses. Tim-1 (HUGO designation HAVCR1) polymorphisms have been linked to the regulation of atopy in mice and humans, suggestive of a role in immune regulation. Tim-1 is expressed upon activation of T cells. In concert with the increased expression of Tim-1, a binding partner for the extracellular domain of Tim-1 (eTim-1) was induced on activated T cells, and mRNA expression data was consistent with the binding partner being Tim-4. We found that co-immobilized recombinant eTim-1 was able to inhibit T cell activation mediated by CD3 + CD28 mAb. eTim-1 mediated its inhibitory effects on proliferation by arresting cell cycle at G(0)/G(1) phase through regulation of cell cycle proteins. In vivo, administration of eTim-1 proteins led to a decrease in both ear (contact hypersensitivity to oxazolone) and joint (methylated BSA antigen-induced arthritis) swelling. The inhibitory activity of eTim-1 in the T(h)1-dependent models was evidence that eTim-1 is able to modulate T cell responses. Manipulation of the Tim-1 interaction with its binding partner on T cells may therefore provide a novel target for therapeutic intervention in T cell-mediated diseases.

Preclinical characterization of CG53135 (FGF-20) in radiation and concomitant chemotherapy/radiation-induced oral mucositis.

PURPOSE: The purpose of this study was to evaluate the activity of CG53135 (FGF-20), a protein with in vitro mitogenic activity on epithelial and mesenchymal cells, in two in vivo models of oral mucositis (OM). EXPERIMENTAL DESIGN: Radiation or concomitant chemotherapy/radiation-induced OM was elicited in hamsters. Activity of CG53135 was assessed at different doses and regimens in the models. Bromodeoxyuridine (BrdUrd) incorporation and pharmacokinetic studies were also performed to correlate in vivo activity of CG53135 with exposure. RESULTS: In the hamster radiation model, administration of CG53135 (600 or 1200 micro g/day, i.p.) on days 3-15 resulted in a statistically significant (P < 0.001) reduction in days spent with severe mucositis. CG53135 administered at 12 mg/kg, i.p. (days 1-2 or 1-8) in the concomitant chemotherapy/radiation model resulted in a statistically significant (P < 0.001) reduction in severe mucositis. Maximal BrdUrd incorporation was observed in cheek pouch and jejunal tissues at 8 h, and peak plasma levels of CG53135 were reached 1 h after administration. CONCLUSIONS: CG53135 demonstrates potent, regimen-dependent activity in hamster models of OM. The activity was regimen dependent. BrdUrd incorporation studies confirmed that CG53135 had proliferative activity in vivo with a favorable pharmacokinetic profile. Based in part on work described herein, CG53135 has received approval from the United States Food and Drug Administration to be evaluated in a Phase I clinical trial of cancer patients at risk for developing OM.

Molecular cloning and developmental expression of the caveolin gene family in the amphibian Xenopus laevis.

Caveolae are approximately 50-100 nm invaginations of the plasma membrane thought to form as a result of a local accumulation of cholesterol, sphingolipids, and a unique family of three proteins known as the caveolins: Cav-1, -2, and -3. Here, we report the identification, sequence, and developmental expression of the three caveolin genes in the amphibian Xenopus laevis. Sequence comparisons show that Xenopus Cav-1, -2, and -3 are approximately 80, 64, and 45% identical, respectively, to their counterparts in humans. Furthermore, Northern blotting experiments demonstrate that the Xenopus caveolins have tissue-specific expression profiles consistent with those previously reported in adult mammals. In the adult frog, Xenopus Cav-1 and Cav-2 are most abundantly expressed in the fat body and the lungs, while Xenopus Cav-3 is primarily expressed in muscle tissue types (heart and skeletal muscle). However, our temporal and spatial analyses of these expression patterns during embryogenesis reveal several novel features, with possible relevance to developmental signaling. Transcripts encoding Xenopus Cav-1 and -2 first appear in the notochord of neurula stage embryos, which represents a key signaling tissue. In contrast, Xenopus Cav-3 shows a highly specific punctate expression pattern in the embryonic epidermis, similar to previous patterns implicated in Notch signaling. These findings are in striking contrast to their steady-state expression patterns in the adult frog. Taken together, our results show that the Xenopus caveolin gene family is present and differentially expressed in both embryonic and adult tissues. This report is the first detailed study of caveolin gene expression in a developing embryo.

Retinoid signaling regulates primitive (yolk sac) hematopoiesis.

It is known from nutritional studies that vitamin A is an important factor for normal hematopoiesis, though it has been difficult to define its precise role. The vitamin A-deficient (VAD) quail embryo provides an effective ligand "knockout" model for investigating the function of retinoids during development. The VAD embryo develops with a significant reduction in erythroid cells, which has not been noted previously. Activation of the primitive erythroid program and early expression of the erythroid marker GATA-1 occurs, though GATA-1 levels eventually decline, consistent with the erythropoietic and hemoglobin deficits. However, from its early stages, the GATA-2 gene fails to be expressed normally in VAD embryos. The bone morphogenetic protein (BMP)-signaling pathway regulates GATA-2, and BMP4 expression becomes reduced in the caudal embryonic region of VAD embryos. Adding BMP4 to cultured VAD-derived explants rescues the production of erythroid cells, whereas normal embryos cultured in the presence of the BMP antagonist noggin are defective in primitive hematopoiesis. We find that cell clusters of primitive blood islands undergo an inappropriate program of apoptosis in the VAD embryo, which can explain the deficit in differentiated primitive blood cells. We propose that vitamin A-derived retinoids are required for normal yolk sac hematopoiesis and that an embryonic retinoid-BMP-GATA-2 signaling pathway controls progenitor cell survival relevant to primitive hematopoiesis.