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Nitric oxide synthesis contributes to IL-2-induced antitumor responses against intraperitoneal Meth A tumor

C Y Yim1, J R McGregor, O D Kwon

  • 1Department of Internal Medicine (Hematology/Oncology), Chonbuk National University Medical School, Korea.

Journal of Immunology (Baltimore, Md. : 1950)
|November 1, 1995
PubMed

Insights

Interleukin-2 (IL-2) therapy boosts nitric oxide (NO) production in cancer patients. This NO synthesis, primarily by macrophages, enhances anti-tumor immune responses and improves survival, but can be blocked by NO synthase inhibitors.

Area of Science:

  • Immunology
  • Cancer Biology
  • Biochemistry

Background:

  • Interleukin-2 (IL-2) therapy is a known stimulator of nitric oxide (NO) synthesis in both mice and humans.
  • The precise role of NO in mediating IL-2's therapeutic effects remains unclear.
  • The Meth A murine skin cancer model offers a system to study IL-2-induced NO synthesis in vivo, independent of lymphokine-activated killer (LAK) cell activity.

Purpose of the Study:

  • To investigate the contribution of IL-2-induced nitric oxide (NO) synthesis to the therapeutic response against Meth A tumors in mice.
  • To identify the cellular sources of IL-2-induced NO production within the tumor microenvironment.
  • To evaluate the impact of NO inhibition on immune cell infiltration and tumor progression during IL-2 therapy.

Main Methods:

  • Administration of subcutaneous IL-2 to mice bearing Meth A tumors.
  • Measurement of nitrite production in ascites-derived cells and urinary nitrate excretion.
  • Inhibition of NO synthesis using N omega-monomethyl-L-arginine (MLA).
  • Assessment of tumor cell proliferation in vitro and immune cell populations (lymphocytes, macrophages) in ascites via cytology and flow cytometry.
  • Electron paramagnetic resonance (EPR) spectroscopy to detect heme nitrosylation.

Main Results:

  • IL-2 treatment significantly increased nitrite production in ascites cells, an effect abrogated by MLA.
  • NO production showed an inverse correlation with tumor cell proliferation in vitro.
  • Macrophages were identified as a major source of IL-2-induced NO synthesis.
  • IL-2 therapy enhanced lymphocyte and macrophage infiltration into ascites, reducing tumor cell recovery; MLA administration reversed this effect.
  • IL-2 therapy increased survival, which was diminished by MLA administration.

Conclusions:

  • IL-2 therapy potently induces nitric oxide (NO) synthesis, primarily from macrophages, in the context of Meth A tumor growth.
  • The induced NO production contributes to the anti-tumor effects of IL-2, including enhanced immune cell recruitment and improved survival.
  • Inhibition of NO synthesis counteracts the beneficial effects of IL-2 therapy, highlighting NO's critical role in IL-2-mediated anti-cancer immunity.

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