IRE1α Activation in Bone Marrow-Derived Dendritic Cells Modulates Innate Recognition of Melanoma Cells and Favors CD8+ T Cell Priming

The IRE1α/XBP1s signaling pathway is an arm of the unfolded protein response (UPR) that safeguards the fidelity of the cellular proteome during endoplasmic reticulum (ER) stress, and that has also emerged as a key regulator of dendritic cell (DC) homeostasis. However, in the context of DC activation, the regulation of the IRE1α/XBP1s axis is not fully understood. In this work, we report that cell lysates generated from melanoma cell lines markedly induce XBP1s and certain members of the UPR such as the chaperone BiP in bone marrow derived DCs (BMDCs). Activation of IRE1α endonuclease upon innate recognition of melanoma cell lysates was required for amplification of proinflammatory cytokine production and was necessary for efficient cross-presentation of melanoma-associated antigens without modulating the MHC-II antigen presentation machinery. Altogether, this work provides evidence indicating that ex-vivo activation of the IRE1α/XBP1 pathway in BMDCs enhances CD8+ T cell specific responses against tumor antigens

Functional gap junctions accumulate at the immunological synapse and contribute to T cell activation

Gap junction (GJ) mediates intercellular communication through linked hemichannels from each of two adjacent cells. Using human and mouse models, we show that connexin 43 (Cx43), the main GJ protein in the immune system, was recruited to the immunological synapse during T cell priming as both GJs and stand-alone hemichannels. Cx43 accumulation at the synapse was Ag specific and time dependent, and required an intact actin cytoskeleton. Fluorescence recovery after photobleaching and Cx43- specific inhibitors were used to prove that intercellular communication between T cells and dendritic cells is bidirectional and specifically mediated by Cx43. Moreover, this intercellular cross talk contributed to T cell activation as silencing of Cx43 with an antisense or inhibition of GJ docking impaired intracellular Ca2+ responses and cytokine release by T cells. These findings identify Cx43 as an important functional component of the immunological synapse and reveal a crucial role for GJs and hemichannels as coordinators of the dendritic cell-T cell signaling machinery that regulates T cell activation. Copyright © 2011 by The American Association of Immunologists, Inc

Tumor recognition by cytotoxic T cells. : Definition of new tumor antigens and the effect of interleukin-10 on antigen presentation

The tumor antigens against which T cell responses have been demonstrated most frequently are not tumor specific but are also expressed on normal tissues. This observation has been interpreted as evidence for breaking of immunological tolerance to normal cellular proteins. In the first part of this thesis we define HLA-A2 restricted CTL epitopes from the Melanocortin 1 Receptor (MC1R) which is expressed on cells of melanocytic origin, including melanoma cells. Peptides derived from this protein were selected on the basis of HLA-A2 binding motifs and tested for their HLA-A2 binding capacity. Three high- or intermediate binding nonamers were found to induce peptide-specific CTL from PBMC of healthy HLA-A2+ donors after in vi~ro stimulation with peptide-pulsed antigen presenting cells (APC). The CTL elicited against MCIR derived peptides could recognize HLA A2+/MC1R expressing melanomas. Using a similar protocol, four new epitopes derived from the proto-oncogene Her2/neu were identified. The CTL raised from ascites fluid of patient with ovarian carcinomas against these HLA-A2+ restricted peptides could recognize naturally processed peptides from HLA-A2+ tumors and from cell lines co-transfected with the antigenic protein gene and HLA-A2. Furthermore, we screened for the expression of MC1R in normal tissues and found this protein to be express to a low degree in adrenal gland and activated monocytes. The screening of anti-melanoma CTL from TIL or PBMC of melanoma patients revealed the presence of anti-MC1R CTL precursors in 50% of the patients, indicating that MC1R is an immunodominant melanoma antigen. Taken together, our findings have implications in relation both to autoimmunity as well as immunotherapy of malignant melanomas and carcinomas. The majority of human tumors are defective in their MHC class I antigen presenting capacity. In the second part of this thesis we have studied the role of Interleukin-10 (IL-10). We showed that IL-10 inhibits antigen presentation to specific CD8+ cytotoxic T Iymphocytes in melanomas. Furthermore, we demonstrated that pre treatment of the mouse Iymphoma RMA with IL-10 resulted in a dose dependent inhibition of Iysis by CTL. However, IL-10 treatment of RMA led to an increased sensitivity to Iysis by NK cells. RMA cells showed an IL-10 dependent downregulation of H-2 expression which could be normalized by addition of H-2 binding peptides, indicating that IL-10 exerts a post transcriptional effect on H-2 expression. Oligopeptides are delivered to the secretory pathway by the TAP protein complex. Relative to normal cells, TAP-deficient cells express substantially lower levels of intracellular antigens to CTL. We demonstrated that IL-10 expression in the RMA Iymphoma and other murine tumors inhibits the TAP-dependent translocation of peptides to the endoplasmic reticulum (ER), resulting in a low expression of cell surface MHC class I molecules. This finding is explained by a down regulation of expression of TAPI and TAP2, observed in IL-10 transfected murine tumor cells. In the J558L plasmacytoma cell line constitutively expressing high levels of IL-10, an increased TAP-dependent translocation of peptides and expression of cell surface MHC class I could be induced by IL-10 anti-sense expression. The effect of IL-10 on a biological relevant system was demonstrated using the NK sensitive prototype tumor YAC-1. Our studies showed that the NK sensitivity of this cell line correlates with the capability of the cells to produce IL-10. IL-10 is the first example of a cytokine which can decrease the expression and function of the TAP1/2 molecular complex, and in more general terms the first example of a cytokine with an inhibitory effect on MHC class I mediated antigen presentation

TAPCells, the Chilean dendritic cell vaccine against melanoma and prostate cancer

Here we summarize 10 years of effort in the development of a biomedical innovation with global projections. This innovation consists of a novel method for the production of therapeutic dendritic-like cells called Tumor Antigen Presenting Cells (TAPCells®). TAPCells-based immunotherapy was tested in more than 120 stage III and IV melanoma patients and 20 castration-resistant prostate cancer patients in a series of phase I and I/II clinical trials. TAPCells vaccines induced T cell-mediated memory immune responses that correlated with increased survival in melanoma patients and prolonged prostate-specific antigen doubling time in prostate cancer patients. Importantly, more than 60% of tested patients showed a Delayed Type Hypersensitivity (DTH) reaction against the lysates, indicating the development of anti-tumor immunological memory that correlates with clinical benefits. The in vitro analysis of the lysate mix showed that it contains damage-associated molecular patterns such as HMBG-1 protein which are capable to improve, through Toll-like receptor-4, maturation and antigen cross-presentation of the dendritic cells (DC). In fact, a Toll-like receptor-4 polymorphism correlates with patient clinical outcomes. Moreover, Concholepas concholepas hemocyanin (CCH) used as adjuvant proved to be safe and capable of enhancing the immunological response. Furthermore, we observed that DC vaccination resulted in a three-fold increase of T helper-1 lymphocytes releasing IFN-γ and a two-fold increase of T helper-17 lymphocytes capable of producing IL-17 in DTH+ with respect to DTH- patients. Important steps have been accomplished for TAPCells technology transfer, including patenting, packaging and technology assessment. Altogether, our results indicate that TAPCells vaccines constitute an exceptional Chilean national innovation of international value

Mind the gaps in tumor immunity: impact of connexin mediated intercellular connections

Gap junctions (GJs)-mediated intercellular communications (GJICs) are connexin (Cx)-formed plasma membrane channels that allow for the passage of small molecules between adjacent cells, and are involved in several physiopathological processes, including immune responses against cancer. In general, tumor cells are poorly coupled through GJs, mainly due to low Cx expression or reduced channel activity, suggesting that Cxs may have tumor suppressor roles. However, more recent data indicate that Cxs and/or GJICs may also in some cases promote tumor progression. This dual role of Cx channels in tumor outcome may be due, at least partially, to the fact that GJs not only interconnect cells from the same type, such as cancer cells, but also promote the intercellular communication of tumor cells with different types of cells from their micro-environment, and such diverse intercellular interactions have distinctive impact on tumor development. For example, whereas GJ-mediated interactions among tumor cells and microglia have been implicated in promotion of tumor growth, tumor cells delivery to dendritic cells of antigenic peptides through GJs have been associated with enhanced immune-mediated tumor elimination. In this review, we provide an updated overview on the role of GJICs in tumor immunity, focusing on the pro-tumor and antitumor effect of GJs occurring among tumor and immune cells. Accumulated data suggest that GJICs may act as tumor suppressors or enhancers depending on whether tumor cells interact predominantly with antitumor immune cells or with stromal cells. The complex modulation of immune-tumor cell GJICs should be taken into consideration in order to potentiate current cancer immunotherapies.Millennium Science Initiative of Ministry of Economy, Development and Tourism P09/016-F Chilean National Fund of Scientific and Technological Development FONDECYT 1130320 FONDECYT 11160380 FONDECYT 317091