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The mammalian/mechanistic target of rapamycin (mTOR) is a key integrative kinase that functions in two independent complexes, mTOR complex (mTORC) 1 and mTORC2. In contrast to the well-defined role of mTORC1 in dendritic cells (DC), little is known about the function of mTORC2. Here, we demonstrate for the first time an enhanced ability of mTORC2-deficient myeloid DC to stimulate and polarize allogeneic T cells. We show that activated bone marrow-derived DC from conditional Rictor−/− mice exhibit lower co-inhibitory B7-H1 molecule expression independently of the stimulus and enhanced IL-6, TNFα, IL-12p70 and IL-23 production following TLR4 ligation. Accordingly, TLR4-activated Rictor−/− DC display augmented allogeneic T cell stimulatory ability, expanding IFN-γ+ and IL-17+, but not IL-10+ or CD4+Foxp3+ regulatory T cells in vitro. A similar DC profile was obtained by stimulating Dectin-1 (C-type lectin family member) on Rictor−/− DC. Using novel CD11c-specific Rictor−/− mice, we confirm the alloreactive Th1 and Th17 cell-polarizing ability of endogenous mTORC2-deficient DC after TLR4 ligation in vivo. Furthermore, we demonstrate that pro-inflammatory cytokines produced by Rictor−/− DC after LPS stimulation are key in promoting Th1/Th17 responses. These data establish that mTORC2 activity restrains conventional DC pro-inflammatory capacity and their ability to polarize T cells following TLR and non-TLR stimulation. Our findings provide new insight into the role of mTORC2 in regulating DC function and may have implications for emerging therapeutic strategies that target mTOR in cancer, infectious diseases, and transplantation.

Recently, significant developments in the field of liver tissue engineering have raised new possibilities for the study of complex physiological and pathophysiological processes in vitro, as well as the potential to assemble entire organs for transplantation. Human-induced pluripotent stem cells have been differentiated into relatively functional populations of hepatic cells, and novel techniques to generate whole organ acellular three-dimensional scaffolds have been developed. In this review, we highlight the most recent advances in organ assembly regarding the development of liver tissue in vitro. We emphasize applications that involve multiple types of cells with a biomimetic spatial organization for which three-dimensional configurations could be used for drug development or to explain mechanisms of disease. We also discuss applications of liver organotypic surrogates and the challenges of translating the highly promising new field of tissue engineering into a proven platform for predicting drug metabolism and toxicity.

Dendritic cells (DC) play a pivotal role in the induction and regulation of immune responses. In cancer, DC-based vaccines have proven to be safe and to elicit protective and therapeutic immunological responses. Recently, we showed that specific mTORC2 (mechanistic target of rapamycin complex 2) deficiency in DC enhances their ability to promote Th1 and Th17 responses after LPS stimulation. In the present study, bone marrow-derived mTORC2-deficient (Rictor ¡/¡ ) DC were evaluated as a therapeutic modality in the murine B16 melanoma model. Consistent with their pro-inflammatory profile (enhanced IL-12p70 production and low PD-L1 expression versus control DC), intratumoral (i.t.) injection of LPS-activated Rictor ¡/¡ DC slowed B16 melanoma growth markedly in WT C57BL/6 recipient mice. This antitumor effect was abrogated when Rictor ¡/¡ DC were injected i.t. into B16-bearing Rag ¡/¡ mice, and also after selective CD8 C T cell depletion in wild-type hosts in vivo, indicating that CD8 C T cells were the principal regulators of tumor growth after Rictor ¡/¡ DC injection. I.t. administration of Rictor ¡/¡ DC also reduced the frequency of myeloid-derived suppressor cells within tumors, and enhanced numbers of IFNg C and granzyme-B C cytotoxic CD8 C T cells both in the spleens and tumors of treated animals. These data suggest that selective inhibition of mTORC2 activity in activated DC augments their pro-inflammatory and T cell stimulatory profile, in association with their enhanced capacity to promote protective CD8 C T cell responses in vivo, leading to slowed B16 melanoma progression. These novel findings may contribute to the design of more effective DC-based vaccines for cancer immunotherapy.

Background Little is known about how new generation adenosine triphosphate (ATP)-competitive mechanistic target of rapamycin (mTOR) kinase inhibitors (TORKinibs) affect immunity and allograft rejection. Methods mTOR complex (C) 1 and 2 signaling in dendritic cells (DC) and T cells was analyzed by Western blotting, while immune cell populations in normal and heart allograft recipient mice were analyzed by flow cytometry. Alloreactive T cell proliferation was quantified in MLR; intracellular cytokine production and serum antidonor IgG levels were determined by flow analysis and immunofluorescence staining used to detect IgG in allografts. Results The novel TORKinib AZD2014 impaired DC differentiation and T cell proliferation in vitro and depressed immune cells and allospecific T cell responses in vivo. A 9-day course of AZD2014 (10 mg/kg ip twice daily) or rapamycin (RAPA; 1mg/kg ip daily) prolonged median heart allograft survival time significantly (25 days for AZD2014; 100 days for RAPA; 9.5 days for control). Like RAPA, AZD2014 suppressed graft mononuclear cell infiltration, increased regulatory T cell (Treg) to effector memory T cell (Tem) ratios and reduced T follicular helper (Tfh) and B cells 7 days posttransplant. By 21 days (10 days after drug withdrawal), however, Tfh and B cells and donor-specific IgG1 and IgG2c antibody titers were significantly lower in RAPA- compared with AZD2014-treated mice. Elevated Treg to Tem ratios were maintained after RAPA, but not AZD2014 withdrawal. Conclusions Immunomodulatory effects of AZD2014, unlike those of RAPA, were not sustained after drug withdrawal, possibly reflecting distinct pharmacokinetics or/and inhibitory effects of AZD2014 on mTORC2.