Background: Regardless of its etiology, colorectal cancer development is intimately associated with dysregulation of the intestinal immune system. Sustained release, orally delivered IL-10 not only inhibits colon tumor growth but restores T cell homeostasis both locoregionally and systemically. However, it does not induce tumor regression. We aimed to combine orally delivered IL-12, a potent immunostimulatory molecule with robust anti-tumor effect, with oral IL-10 therapy to induce tumor regression.

Methods: 6 week old APCmin mice were inoculated with enterotoxic Bacteroides fragilis (serotype 086) after five days of intestinal flora depletion with antibiotics dissolved in drinking water. 7-10 days after bacterial inoculation, mice were treated three times weekly with either 1) blank polylactic acid microspheres for 3 weeks, 2) IL-10 containing microspheres (0.5 microgram/dose) for 3 weeks, 3) IL-12 containing microspheres (0.25 micrograms/dose) for 3 weeks, or 4) IL-10 containing microspheres for 1 week followed by a combination of IL-10 and IL-12 containing microspheres for 2 weeks. After euthanasia, colons were assessed for polyp counts and select polyps were isolated for confocal microscopy analysis. Mesenteric lymph node lymphocytes were isolated and analyzed using flow cytometry.

Results: Mice treated with oral IL-10 and IL-12 demonstrated a reduction in polyp number compared to those mice treated with IL-10 alone, and both groups had fewer polyps than mice treated with either IL-12 or blank microspheres. Addition of IL-12 resulted in increased CD8+ T cell numbers and IFN-γ production compared to treatment with IL-10 alone. IL-10 retained its effect on CD4+ T cells when combining it with IL-12, resulting in a decrease in conventional regulatory T cells (FoxP3+ RORγT -) as well as pathogenic regulatory T cells (FoxP3+ RORγT+) and IL-17 producing CD4+ T cells.

Conclusions: The addition of IL-12 to IL-10 therapy augments the therapeutic effect of oral cytokine treatment on colon adenocarcinoma in the APCmin B. fragilis model. The effect appears additive and mediated by both IL-10’s effect on regulatory T cell populations and IL-12’s effect on CD8+ T cells. Further studies in the setting of more advanced disease, including liver metastases, will elucidate the therapeutic potential of combination oral cytokine therapy with IL-10 and IL-12 for treatment of colorectal cancer.

Citation Format: Neal Bhutiani, Qingsheng Li, Charles D. Anderson, Tao Gu, Nejat K. Egilmez. Combined oral cytokine therapy effectively treats colon cancer in a murine model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1605. doi:10.1158/1538-7445.AM2017-1605