Potentiation of electrochemotherapy by intramuscular IL-12 gene electrotransfer in murine sarcoma and carcinoma with different immunogenicity

Abstract

Background.Electrochemotherapy provides good local tumor control but requires adjuvant treatment for increased local response and action on distant metastasis. In relation to this, intramuscular interleukin-12 (IL-12) gene electro-transfer, which provides systemic shedding of IL-12, was combined with local electrochemotherapy with cisplatin. Furthermore, the dependence on tumor immunogenicity and immunocompetence of the host on combined treatment response was evaluated.Materials and methods.Sensitivity of SA-1 sarcoma and TS/A carcinoma cells to electrochemotherapy with cisplatin was tested in vitro. In vivo, intratumoral electrochemotherapy with cisplatin (day 1) was combined with a single (day 0) or multiple (days 0, 2, 4) intramuscular murine IL-12 (mIL-12) gene electrotransfer. The antitumor effectiveness of combined treatment was evaluated on immunogenic murine SA-1 sarcoma in A/J mice and moderately immunogenic murine TS/A carcinoma, in immunocompetent BALB/c and immunodeficient SCID mice.Results.Electrochemotherapy in vitro resulted in a similar IC50 values for both sarcoma and carcinoma cell lines. However, in vivo electrochemotherapy was more effective in the treatment of sarcoma, the more immunogenic of the tumors, resulting in a higher log cell kill, longer specific tumor growth delay, and also 17% tumor cures compared to carcinoma where no tumor cures were observed. Adjuvant intramuscular mIL-12 gene electrotransfer increased the log cell kill in both tumor models, potentiating the specific tumor growth delay by a factor of 1.8-2 and increasing tumor cure rate by approximately 20%. In sarcoma tumors, the potentiation of the response by intramuscular mIL-12 gene electrotransfer was dose-dependent and also resulted in a faster onset of tumor cures. Comparison of the carcinoma response to the combined treatment modality in immunocompetent and immunodeficient mice demonstrated that the immune system is needed both for increased cell kill and for attaining tumor cures.Conclusions.Based on the comparison of the antitumor effectiveness of electrochemotherapy to intratumoral cisplatin administration, we can conclude that the fraction of cells killed and the tumor cure rate are higher in immunogenic sarcoma tumor compared to moderately immunogenic carcinoma tumor. The tumor cell kill and cure rate depend on the immune response elicited by the destroyed tumor cells, which might depend on the tumor immunogenicity. The effect of adjuvant intramuscular mIL-12 gene electrotransfer is dependent on the amount of IL-12 in the system and the immune competence of the host, as demonstrated by the dose-dependent increase in the cure rate of SA-1 tumors after multiple intramuscular mIL-12 gene electrotransfer and in the differential cure rate of TS/A tumors growing in immunocompetent and immunodeficient mice.

Efficacy and safety of electrochemotherapy combined with peritumoral IL‐12 gene electrotransfer of canine mast cell tumours

“…Although it was recently demonstrated that electrochemotherapy induces immunological cell death, the therapy on its own is not able to induce a systemic immunity, thus not having the abscopal effect . Therefore, to add a systemic component to local electrochemotherapy treatment, it was combined on a preclinical level with several immunological approaches, such as the addition of IL‐2 secreting cells, recombinant TNF‐α and also IL‐12 gene electrotransfer, which proved to be very effective . Even on its own, IL‐12 electrogene therapy was successful in the eradication of melanoma and sarcoma tumours in mice .…”

Radiosensitizing effect of intratumoral interleukin-12 gene electrotransfer in murine sarcoma

“…All the mice cured by multiple mIL-12 gene electrotransfer alone or combined with radiation were also resistant to secondary challenge, however the same phenomena was observed with mice treated with treatments used as pertinent controls (multiple therapies with electric pulse application or plasmid coding for dsRed combined with tumor irradiation) that resulted in tumors cures, due to their immunogenicity. This indicates that multiple mIL-12 gene electrotransfer alone or combined with irradiation and also treatments used as pertinent controls might have either increased the immunogenicity of SA-1 sarcoma [28,41] (increased tumor antigen availability after radiation induced apoptosis) or stimulated the immune cells (control plasmid coding for immunogenic protein) [34,42,43] leading to a better tumor immunosurveillance and prevention of tumor outgrowth after secondary challenge. Thus, in contrast to the effects of IL-12 on tumor cures its contribution to the long term immunity could not be evaluated.…”

Electroporation-Based Technologies for Medicine: Principles, Applications, and Challenges

“…During preclinical studies, several mechanisms that contribute to the overall effectiveness of ECT have been demonstrated. Besides the basic mechanism of increased membrane permeability leading to increased drug cytotoxicity (50), reduced tumor blood flow (vascular lock) is observed (51) and results in a vascular disruption effect of ECT (52)(53)(54)(55); an enhanced immune response is also observed (56)(57)(58). Thus, combining ECT with an immunostimulatory approach using recombinant cytokines or GET-delivered plasmids encoding these cytokines (e.g., IL-2, IL-12, IL-15, GM-CSF, and TNF-α) can give rise to a significant potentiation of ECT treatment (59)(60)(61)(62).…”