Yoshiteru Nakano1, Takehiro Kitagawa2, Yoshio Osada3, Tohru Tanaka4, Shigeru Nishizawa2, Junkoh Yamamoto2. 1. Department of Neurosurgery, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan. Electronic address: yo-naka@med.uoeh-u.ac.jp. 2. Department of Neurosurgery, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan. 3. Department of Immunology and Parasitology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan. 4. SBI Pharmaceuticals Co., Ltd., Minato-Ku, Tokyo, Japan.
Abstract
BACKGROUND: 5-Aminolevulinic acid (5-ALA) induces the accumulation of a large amount of protoporphyrin IX (PpIX) in tumors, which has been used in the treatment of several cancers. 5-ALA is commonly used for fluorescence-guided tumor resection in clinical neurosurgery and for photodynamic therapy based on the generation of cytotoxic oxygen. OBJECTIVE: The purpose of this study was to identify the mechanisms of 5-ALA-induced immune response in macrophages in malignant glioma. METHODS: Intracellular levels of 5-ALA-induced PpIX in C3H/HeN murine peritoneal macrophages were measured by the median fluorescence intensity using flow cytometry and confocal laser scanning microscopy. Macrophages were cultured in vitro with or without 0.5 mM 5-ALA, 0.1 μg/mL lipopolysaccharide, and 20% glioma-conditioned medium. Levels of immunosuppressive prostaglandin E2 (PGE2), interleukin-10, and transforming growth factor β were measured using enzyme immunoassay in the culture supernatant. In addition, macrophages and RSV-M mouse glioma cells were co-cultured in vitro with cell culture inserts with or without 5-ALA (0.1 and 0.5 mM) and lipopolysaccharide (0.1 μg/mL). RESULTS: We found that 5-ALA-induced PpIX accumulated in macrophages and significantly suppressed PGE2 production and expression of both cyclooxygenase-2 and microsomal prostaglandin E synthase-1. 5-ALA treatment also suppressed PGE2 production by glioma-conditioned medium. 5-ALA suppressed RSV-M glioma cell proliferation in a concentration-dependent manner. CONCLUSIONS: These results indicate that 5-ALA suppressed PGE2 production by macrophages via the downregulation of cyclooxygenase-2 and microsomal prostaglandin E synthase-1 expression levels. This is a novel mechanism to induce effective immune response against glioma in macrophages.
BACKGROUND:5-Aminolevulinic acid (5-ALA) induces the accumulation of a large amount of protoporphyrin IX (PpIX) in tumors, which has been used in the treatment of several cancers. 5-ALA is commonly used for fluorescence-guided tumor resection in clinical neurosurgery and for photodynamic therapy based on the generation of cytotoxic oxygen. OBJECTIVE: The purpose of this study was to identify the mechanisms of 5-ALA-induced immune response in macrophages in malignant glioma. METHODS: Intracellular levels of 5-ALA-induced PpIX in C3H/HeN murine peritoneal macrophages were measured by the median fluorescence intensity using flow cytometry and confocal laser scanning microscopy. Macrophages were cultured in vitro with or without 0.5 mM 5-ALA, 0.1 μg/mL lipopolysaccharide, and 20% glioma-conditioned medium. Levels of immunosuppressive prostaglandin E2 (PGE2), interleukin-10, and transforming growth factor β were measured using enzyme immunoassay in the culture supernatant. In addition, macrophages and RSV-M mouseglioma cells were co-cultured in vitro with cell culture inserts with or without 5-ALA (0.1 and 0.5 mM) and lipopolysaccharide (0.1 μg/mL). RESULTS: We found that 5-ALA-induced PpIX accumulated in macrophages and significantly suppressed PGE2 production and expression of both cyclooxygenase-2 and microsomal prostaglandin E synthase-1. 5-ALA treatment also suppressed PGE2 production by glioma-conditioned medium. 5-ALA suppressed RSV-M glioma cell proliferation in a concentration-dependent manner. CONCLUSIONS: These results indicate that 5-ALA suppressed PGE2 production by macrophages via the downregulation of cyclooxygenase-2 and microsomal prostaglandin E synthase-1 expression levels. This is a novel mechanism to induce effective immune response against glioma in macrophages.
Authors: Jeffrey I Traylor; Mark N Pernik; Alex C Sternisha; Samuel K McBrayer; Kalil G Abdullah Journal: Cancers (Basel) Date: 2021-02-02 Impact factor: 6.639