Interleukin-12 gene therapy of a weakly immunogenic mouse mammary carcinoma results in reduction of spontaneous lung metastases via a T-cell-independent mechanism

Abstract

In our previous studies using gene gun-mediated delivery of interleukin 12 (IL-12) cDNA in vivo, we observed T-cell-mediated regression of established murine tumors and demonstrated the induction of systemic immunity in test animals. In this study, we further characterized the antitumoral and anti-metastatic effect of this gene therapy approach by employing two murine metastatic mammary tumor models: the immunogenic TS/A adenocarcinoma and the weakly immunogenic 4T1 adenocarcinoma. In the TS/A model, gene transfer into the skin overlying an established intradermal tumor with an IL-12 cDNA expression vector resulted in complete tumor regression in 50% of mice followed by the development of immunological memory. In contrast, the growth of the intradermal 4T1 tumors was not affected by the IL-12 gene therapy protocol. However, this treatment resulted in a substantial reduction of spontaneous metastases in the lungs of 4T1 tumor-bearing mice and significantly prolonged their survival time. T cells were not required for this anti-metastatic effect, because it was also observed in nude mice and in mice depleted of CD4 ϩ and CD8 ϩ T cells. Tumor-draining lymph node cells obtained from 4T1 tumor-bearing mice treated with IL-12 cDNA exhibited increased natural killer (NK) activity and produced enhanced levels of interferon-␥ (IFN-␥) compared with similar mice treated with luciferase cDNA. In addition, in vivo depletion of NK cells or neutralization of IFN-␥ resulted in partial suppression of the anti-metastatic effect of IL-12 gene therapy, suggesting the involvement of both NK cells and IFN-␥ in this effect. Cancer Gene Therapy (2000) 1, 826 -838

New insights into IL-12-mediated tumor suppression

“…Whereas IL-12 led to regression of highly immunogenic TS/A tumors, the growth of 4T1 tumors, which are considered less immunogenic, was not affected. 75 In the 4T1 model, however, the treatment resulted in a marked reduction of lung metastasis, an effect that was partially dependent on IFNg-producing NK cells. 75,76 Despite most of these strategies provided a continuous release of IL-12 and IFNg within the tumor, just a few of them reported that IL-12 was acting locally by showing low serum levels of these cytokines.…”

“…75 In the 4T1 model, however, the treatment resulted in a marked reduction of lung metastasis, an effect that was partially dependent on IFNg-producing NK cells. 75,76 Despite most of these strategies provided a continuous release of IL-12 and IFNg within the tumor, just a few of them reported that IL-12 was acting locally by showing low serum levels of these cytokines. 71,74 Nevertheless, synergistic antitumor responses in breast cancer have been achieved by combining local adenovirus-mediated gene transfer of IL-12 with T-cell chemoattractants (lymphotactin, CXCL10), costimulatory molecules (B7.1, glucocorticoid induced TNF receptor ligand, 4-1BB ligands), GM-CSF, radiotherapy or antiangiogenic therapy.…”

CCL5 as a potential immunotherapeutic target in triple-negative breast cancer

“…49 In particular, substantial reduction in tumor size and in spontaneous metastases in the lungs of 4T1 tumor-bearing mice as well as prolonged survival time was accomplished by IL-12 administration. 50,51 These effects were accompanied by increased natural killer activity and enhanced levels of IFN-c in tumor-draining lymph node cells obtained from 4T1 tumor-bearing mice treated with IL-12. 50 Due to the unique characteristics of 4T1 tumor, this model has been used to investigate important issues such as immunotherapy, 52 metastasis, 53 anti-angiogenesis therapy 54 and multiple chemotherapy treatments.…”

Intratumoral injection of IL-12 plasmid DNA – results of a phase I/IB clinical trial

“…This drug was able to prevent the development of metastases and was able to elicit long-term antitumor immunity. 2,3 Depending on the tumor model, IL-12 can effect antitumor activity via T cells, 4,5 natural killer cells [6][7][8][9][10] or NK T cells. 11 IL-12 induces other cytokines such as interferon-g (IFN-g) [12][13][14][15][16] and IFN-inducible protein-10.…”

“…17 IL-12 also exerts an antiangiogenic effect which may also inhibit both metastatic and local tumor growth. [6][7][8][9][10][11][13][14][15][16][17][18] The systemic administration of IL-12 protein for the treatment of tumor has been studied in both murine models and phase I clinical trials. 12,19,9,[20][21][22] Systemic IL-12 protein therapy, however, has been associated with dose-limiting toxicity.…”