Semiallogenic fusions of MSI+ tumor cells and activated B cells induce MSI-specific T cell responses

<p>Abstract</p> <p>Background</p> <p>Various strategies have been developed to transfer tumor-specific antigens into antigen presenting cells in order to induce cytotoxic T cell responses against tumor cells. One approach uses cellular vaccines based on fusions of autologous antigen presenting cells and allogeneic tumor cells. The fusion cells combine antigenicity of the tumor cell with optimal immunostimulatory capacity of the antigen presenting cells.</p> <p>Microsatellite instability caused by mutational inactivation of DNA mismatch repair genes results in translational frameshifts when affecting coding regions. It has been shown by us and others that these mutant proteins lead to the presentation of immunogenic frameshift peptides that are - in principle - recognized by a multiplicity of effector T cells.</p> <p>Methods</p> <p>We chose microsatellite instability-induced frameshift antigens as ideal to test for induction of tumor specific T cell responses by semiallogenic fusions of microsatellite instable carcinoma cells with CD40-activated B cells. Two fusion clones of HCT116 with activated B cells were selected for stimulation of T cells autologous to the B cell fusion partner. Outgrowing T cells were phenotyped and tested in functional assays.</p> <p>Results</p> <p>The fusion clones expressed frameshift antigens as well as high amounts of MHC and costimulatory molecules. Autologous T cells stimulated with these fusions were predominantly CD4⁺, activated, and reacted specifically against the fusion clones and also against the tumor cell fusion partner. Interestingly, a response toward 6 frameshift-derived peptides (of 14 tested) could be observed.</p> <p>Conclusion</p> <p>Cellular fusions of MSI⁺carcinoma cells and activated B cells combine the antigen-presenting capacity of the B cell with the antigenic repertoire of the carcinoma cell. They present frameshift-derived peptides and can induce specific and fully functional T cells recognizing not only fusion cells but also the carcinoma cells. These hybrid cells may have great potential for cellular immunotherapy and this approach should be further analyzed in preclinical as well as clinical trials. Moreover, this is the first report on the induction of frameshift-specific T cell responses without the use of synthetic peptides.</p

Interaction of oligonucleotide-conjugates with the dipeptide transporter system in Caco-2 cells.

Oligonucleotide-based therapies represent novel strategies for manipulating the expression and function of target proteins and are undergoing clinical evaluation for the treatment of viral diseases and malignancies. However, poor biological stability and cellular delivery represent potential limitations to the therapeutic development of oligonucleotides. Conjugation of oligonucleotides to lipophilic groups can improve delivery to cells but the enhanced cellular binding may also facilitate nonspecific interactions. In this report, we show that phosphorothioate oligonucleotides conjugated to lipophilic groups, either tocopherol (Vitamin E) or 2-Di-O-hexadecyl-3-glycerol, can significantly inhibit the functioning of the dipeptide transporter system (DTS) in cultured Caco-2 intestinal cells. Because the DTS mediates the binding and absorption of nutrient peptides and important drugs, such as the cephalosporin and penicillin antibiotics, this finding has important implications in relation to the potential toxicity of lipophilic conjugates in vivo. It also suggests a potential drug interaction with lipophilic oligonucleotide-conjugates if they were to be delivered orally