The median survival for metastatic melanoma is in the realm of 8–16 months and there are few therapies that offer significant improvement in overall survival. One of the recent advances in cancer treatment focuses on epigenetic modifiers to alter the survivability and immunogenicity of cancer cells. Our group and others have previously demonstrated that pan-HDAC inhibitors induce apoptosis, cell cycle arrest and changes in the immunogenicity of melanoma cells. Here we interrogated specific HDACs which may be responsible for this effect. We found that both genetic abrogation and pharmacologic inhibition of HDAC6 decreases in vitro proliferation and induces G1 arrest of melanoma cell lines without inducing apoptosis. Moreover, targeting this molecule led to an important upregulation in the expression of tumor associated antigens and MHC class I, suggesting a potential improvement in the immunogenicity of these cells. Of note, this anti-melanoma activity was operative regardless of mutational status of the cells. These effects translated into a pronounced delay of in vivo melanoma tumor growth which was, at least in part, dependent on intact immunity as evidenced by the restoration of tumor growth after CD4+ and CD8+ depletion. Given our findings, we provide the initial rationale for the further development of selective HDAC6 inhibitors as potential therapeutic anti-melanoma agents.
Therapeutic vaccines for the treatment of cancer are an attractive alternative to some of the conventional therapies that are currently used. More importantly, vaccines could be very useful to prevent recurrences when applied after primary therapy. Unfortunately, most therapeutic vaccines for cancer have performed poorly due to the low level of immune responses that they induce. Previous work done in our laboratory in cancer mouse models demonstrated that vaccines consisting of synthetic peptides representing minimal CD8 T cell epitopes administered i.v. mixed with poly-IC and anti-CD40 antibodies (TriVax) were capable of inducing massive T cell responses similar to those found during acute infections. We now report that some peptides are capable of inducing similarly large T cell responses after vaccination with poly-IC alone (BiVax). The results show that amphiphilic peptides are more likely to function as strong immunogens in BiVax and that systemic immunizations (i.v. or i.m.) were more effective than local (s.c.) vaccine administration. The immune responses induced by BiVax were found to be effective against established tumors in two mouse cancer models. The roles of various immune related pathways such as type-I IFN, CD40 costimulation, CD4 T cells, TLRs and the MDA5 RNA helicase were examined. The present findings could facilitate the development of simple and effective subunit vaccines for diseases where CD8 T cells provide a therapeutic benefit.
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Background Therapeutic vaccines for cancer are an attractive alternative to conventional therapies, since the later result in serious adverse effects and in most cases are not effective against advanced disease. Human Papillomavirus (HPV) is responsible for several malignancies such as cervical carcinoma. Vaccines targeting oncogenic viral proteins like HPV16-E6 and -E7 are ideal candidates to elicit strong immune responses without generating autoimmunity because: i) these products are not expressed in normal cells; and ii) their expression is required to maintain the malignant phenotype. Our group has developed peptide vaccination strategy called TriVax, which is effective in generating vast numbers of antigen-specific T cells in mice capable of persisting for long time periods. Materials and methods We have used two HPV-induced mouse cancer models (TC-1 and C3.43) to evaluate the immunogenicity and therapeutic efficacy of TriVax prepared with the immunodominant CD8 T cell epitope HPV16-E749–57, mixed with poly-IC adjuvant and costimulatory anti-CD40 antibodies. Results TriVax using HPV16-E749–57 induced large and persistent T cell responses that were therapeutically effective against established HPV16-E7 expressing tumors. In most cases, TriVax was successful in attaining complete rejections of 6–11 day established tumors. In addition, TriVax induced long-term immunological memory, which prevented tumor recurrences. The antitumor effects of TriVax were independent of NK and CD4 T cells and surprisingly, did not rely to a great extent on type-I or type-II interferon. Conclusions These findings indicate that the TriVax strategy is an appealing immunotherapeutic approach for the treatment of established viral-induced tumors. We believe that these studies may help to launch more effective and less invasive therapeutic vaccines for HPV-mediated malignancies.
Tumor-associated myeloid cells, including dendritic cells and macrophages, are immune suppressive. The current study demonstrates a novel mechanism involving FOXO3 and NF-κB RelA that controls myeloid cell signaling and impacts their immune suppressive nature. We find that FOXO3 binds NF-κB RelA in the cytosol, impacting both proteins by preventing FOXO3 degradation and preventing NF-κB RelA nuclear translocation. The location of protein-protein interaction was determined to be near the FOXO3 transactivation domain. In turn, NF-κB RelA activation was restored upon deletion of the same sequence in FOXO3 containing the DNA binding domain. We have identified for the first time, a direct protein-protein interaction between FOXO3 and NF-κB RelA in tumor-associated dendritic cells. These detailed biochemical interactions provide the foundation for future studies to utilize the FOXO3-NF-κB RelA interaction as a target to enhance tumor-associated dendritic cell function to support or enhance anti-tumor immunity.
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