Intratumoral electroporation of IL-12 cDNA eradicates established melanomas by Trp2180–188-specific CD8+ CTLs in a perforin/granzyme-mediated and IFN-γ-dependent manner: application of Trp2180–188 peptides

Abstract

Intratumoral electroporation (IT-EP) with IL-12 cDNA (IT-EP/IL12) can lead to the eradication of established B16 melanoma tumors in mice. Here, we explore the immunological mechanism of the antitumor effects generated by this therapy. The results show that IT-EP/IL12 applied only once resulted in eradication in 70% animals with large established B16 tumors. Tumor eradication required the participation of CD8+ T cells, but not CD4+ T cells and NK cells. IT-EP/IL12 induced antigen-specific CD8+ T cell responses against the immunodominant Trp2(180-188) epitope and generated a systemic response, resulting in significant therapeutic effects against distal, untreated tumors. The therapeutic effect of IT-EP/IL12 was absent in perforin-deficient mice, indicating that tumor elimination occurred through conventional perforin/granzyme lysis by CTLs. Moreover, this therapy induced some degree of immunological memory that protected approximately one-third of the cured mice against a subsequent tumor challenge. Moreover, antitumor efficacy and long-term protection against B16 were significantly improved by concurrent Trp2 peptide immunization through more induction of Ag-specific CTL responses and more attraction of IFN-γ-expressing CD8+ T cells into tumor sites. The antitumor effect of IT-EP/IL12 required the participation of IFN-γ, which was shown to induce MHC class I expression on B16 cells and increase the lytic activity of the CD8+ CTL generated by IT-EP/IL12. The results from these animal studies may help in the development of IT-EP/IL12 for cancer patients.

Melanoma Treatment with Intratumoral Electroporation of Tavokinogene Telseplasmid (pIL-12, Tavokinogene Telseplasmid)

“…Rechallenge with B16.F10 cells in these studies indicate the generation of a systemic antitumor memory response. These antitumor effects of pIL-12-EP have been shown to be associated with a local influx of activated cytotoxic T lymphocytes and partially dependent on IFN-γ, granzyme and perforin [42]. This study also demonstrated generation of CD8 + T cells specific to tumor-associated antigen tyrosinase-related peptide 2 (Trp2).…”

“…Electroporation of pIL-12 DNA has been demonstrated to yield high levels of IL-12 expression [41] leading to IFN-γ-mediated tumor cell killing [42,43], immune cell recruitment [41] and objective tumor regressions in animal models [43][44][45] including regression of untreated lesions [46]. In vivo tumor regressions have been durable and treated animals may be resistant to tumor reimplantation suggesting that intratumoral electroporation of pIL-12 DNA induces memory immune responses in these models [47,48].…”

How Do Cytotoxic Lymphocytes Kill Cancer Cells?

“…The elimination of melanoma and sarcoma murine cell lines by IL12 (66,67) or IL15 (68) was found to be dependent on PRF1 expression. PRF1 was also required to control melanoma tumor metastasis by IL12 (69,70).…”

New insights into IL-12-mediated tumor suppression

“…[77][78][79][80][81][82][83] Furthermore, the combination with chemotherapeutic or antiangiogenic agents in lung, skin and colorectal cancer, or with antiangiogenic agents in prostate cancer proved to be more efficient than viral-mediated IL-12 gene therapy alone in different types of tumors. [84][85][86][87][88][89] Even though local delivery of IL-12 by gene therapy resulted in a more sustained expression of IL-12 in comparison with the levels obtained by injecting the recombinant protein, the lack of selectivity and the occurrence of non-specific immune responses associated with the use of viral vectors remain a major concern when using this strategy to deliver IL-12.…”