Macrophage Polarization In The Tumor Microenvironment.

Area of Science:

• Immunology
• Cancer Biology
• Molecular Biology

Background:

• Tumor-associated macrophages (TAMs) promote tumor progression and are linked to poor prognosis.
• Apoptotic tumor cells initiate a program that shifts macrophages from tumor-attacking to tumor-supportive phenotypes.

Purpose of the Study:

• To investigate macrophage phenotype shifts during tumor progression.
• To analyze the macrophage nitric oxide (NO)-output system and potential NO targets.

Main Methods:

• Biochemical and molecular biology cell culture experiments.
• Three-dimensional (3D) tumor spheroid models.
• Animal experiments (xenograft model).

Main Results:

• Apoptotic cells induce a tumor-supportive macrophage phenotype via sphingosine-1-phosphate (S1P), increasing arginase 2 and decreasing NO production.
• S1P-mediated arginase 2 expression involves the S1P2 receptor and CRE binding site.
• Reduced NO production in macrophages correlates with tumor-associated S1P formation and tumor growth.
• The role of NO in targeting hypoxia-inducible factor-1 (HIF-1) and jumonji histone demethylases (JHDMs) within the tumor microenvironment will be discussed.

Conclusions:

• Apoptotic tumor cells and subsequent macrophage activation promote malignant disease progression.
• Macrophage polarization critically impacts the NO-output system, influencing their capacity to support or restrict tumor growth.