Combining Exosomes Derived from Immature DCs with Donor Antigen-Specific Treg Cells Induces Tolerance in a Rat Liver Allograft Model.

Allograft tolerance is the ultimate goal in the field of transplantation immunology. Immature dendritic cells (imDCs) play an important role in establishing tolerance but have limitations, including potential for maturation, short lifespan in vivo and short storage times in vitro. However, exosomes (generally 30-100 nm) from imDCs (imDex) retain many source cell properties and may overcome these limitations. In previous reports, imDex prolonged the survival time of heart or intestine allografts. However, tolerance or long-term survival was not achieved unless immune suppressants were used. Regulatory T cells (Tregs) can protect allografts from immune rejection, and our previous study showed that the effects of imDex were significantly associated with Tregs. Therefore, we incorporated Tregs into the treatment protocol to further reduce or avoid suppressant use. We defined the optimal exosome dose as approximately 20 µg (per treatment before, during and after transplantation) in rat liver transplantation and the antigen-specific role of Tregs in protecting liver allografts. In the co-treatment group, recipients achieved long-term survival, and tolerance was induced. Moreover, imDex amplified Tregs, which required recipient DCs and were enhanced by IL-2. Fortunately, the expanded Tregs retained their regulatory ability and donor-specificity. Thus, imDex and donor-specific Tregs can collaboratively induce graft tolerance.

MicroRNA-548a-5p promotes proliferation and inhibits apoptosis in hepatocellular carcinoma cells by targeting Tg737.

AIM: To investigate whether Tg737 is regulated by microRNA-548a-5p (miR-548a-5p), and correlates with hepatocellular carcinoma (HCC) cell proliferation and apoptosis. METHODS: Assays of loss of function of Tg737 were performed by the colony formation assay, CCK assay and cell cycle assay in HCC cell lines. The interaction between miR-548a-5p and its downstream target, Tg737, was evaluated by a dual-luciferase reporter assay and quantitative real-time polymerase chain reaction. Tg737 was then up-regulated in HCC cells to evaluate its effect on miR-548a-5p regulation. HepG2 cells stably overexpressing miR-548a-5p or miR-control were also subcutaneously inoculated into nude mice to evaluate the effect of miR-548a-5p up-regulation on in vivo tumor growth. As the final step, the effect of miR-548a-5p on the apoptosis induced by cisplatin was evaluated by flow cytometry. RESULTS: Down-regulation of Tg737, which is a target gene of miR-548a-5p, accelerated HCC cell proliferation, and miR-548a-5p promoted HCC cell proliferation in vitro and in vivo. Like the down-regulation of Tg737, overexpression of miR-548a-5p in HCC cell lines promoted cell proliferation, increased colony forming ability and hampered cell apoptosis. In addition, miR-548a-5p overexpression increased HCC cell growth in vivo. MiR-548a-5p down-regulated Tg737 expression through direct contact with its 3' untranslated region (UTR), and miR-548a-5p expression was negatively correlated with Tg737 levels in HCC specimens. Restoring Tg737 (without the 3'UTR) significantly hampered miR-548a-5p induced cell proliferation, and rescued the miR-548a-5p induced cell proliferation inhibition and apoptosis induced by cisplatin. CONCLUSION: MiR-548a-5p negatively regulates the tumor inhibitor gene Tg737 and promotes tumorigenesis in vitro and in vivo, indicating its potential as a novel therapeutic target for HCC.

Fbxw7 regulates hepatocellular carcinoma migration and invasion via Notch1 signaling pathway.

Hepatocellular carcinoma (HCC) is one of the most common human malignancies and also the leading cause of cancer-related death in the world. The mechanisms underlying the progression and metastasis of HCC remain unclear. The E3 ubiquitin ligase F-box and WD repeat domain-containing 7 (Fbxw7) is broadly considered as a tumor suppressor gene. However, the role of Fbxw7 in HCC is not clear. To investigate the expression and biological functions of Fbxw7 in HCC, we examined Fbxw7 expression level using HCC tissue microarray and immunohistochemistry. Our data showed that Fbxw7 expression is significantly reduced in HCC compared with non-cancerous tissues (P<0.05). Fbxw7 levels were significantly associated with tumor differentiation (P=0.013), the incidence of portal or hepatic venous invasion (P=0.031), metastasis (P=0.027) and AJCC cancer stage (P=0.047). Then, we observed a strong correlation between low Fbxw7 expression and a worse 5-year survival of HCC patients (P<0.001). Furthermore, multivariate Cox regression analyses demonstrated that the Fbxw7 expression (P<0.001) was an independent factor for the prediction of the overall survival of HCC patients. We also found that both Fbxw7 mRNA and protein levels were significantly reduced in HCC cell lines compared with human liver non-tumor cell line. Moreover, our in vitro experiments showed a remarkable increase of cell migration and invasion in Fbxw7-knockdown cells and a decrease in Fbxw7-overexpress cells. In addition, the present study demonstrated that Fbxw7 is involved in the migration and invasion of HCC cells via regulating Notch1 and the downstream molecules of Notch1. Taken together, our findings indicate that Fbxw7 can be used as a prognostic marker; it has an important role in HCC progression and inhibits HCC cell migration and invasion through the Notch1 signaling pathway.

Tolerance induction by exosomes from immature dendritic cells and rapamycin in a mouse cardiac allograft model.

BACKGROUND: Dendritic cells (DCs) release bioactive exosomes that play an important role in immune regulation. Because they express low levels of class I major histocompatibility complex (MHC) and co-stimulatory molecules, exosomes derived from donor immature DCs (imDex) prolong allograft survival by inhibiting T-cell activation. However, this effect is limited and does not induce immunological tolerance when imDex are administered alone. Thus, we tested the effect of combined treatment with donor imDex and low-dose rapamycin on inducing tolerance in a mouse cardiac transplantation model. METHODS: ImDex were obtained from the culture supernatant of immature DCs derived from donor mouse (C57BL/6) bone marrow and were injected with suboptimal doses of rapamycin into recipient mouse (BALB/c) before and after transplantation. The capacity of this treatment to induce immune tolerance was analyzed in vitro and in vivo using the mouse cardiac transplantation model. RESULTS: Donor imDex expressed moderate levels of MHC class II and low levels of MHC class I and co-stimulatory molecules, but neither imDex nor subtherapeutic rapamycin dose alone induced cardiac allograft tolerance. Combined treatment with imDex and rapamycin, however, led to donor specific cardiac allograft tolerance. This effect was accompanied by decreased anti-donor antigen cellular response and an increased percentage of spleen CD4(+)CD25(+) T cells in recipients. Furthermore, this donor specific tolerance could be further transferred to naïve allograft recipients through injection of splenocytes, but not serum, from tolerant recipients. CONCLUSION: Combined with immunosuppressive treatment, donor imDex can prolong cardiac allograft survival and induce donor specific allograft tolerance.