• Yosuke Yokota, Hiroyuki Inoue, Yumiko Matsumura, Haruka Nabeta, Megumi Narusawa, Ayumi Watanabe, Chika Sakamoto, Yasuki Hijikata, Mutsunori Iga-Murahashi, Koichi Takayama, Fumiyuki Sasaki, Yoichi Nakanishi, Takehiko Yokomizo, and Kenzaburo Tani.
• Department of Molecular Genetics, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan.
• Blood. 2012 Oct 25; 120 (17): 3444-54.

AbstractBLT1 is a high-affinity receptor for leukotriene B4 (LTB4) that is a potent lipid chemoattractant for myeloid leukocytes. The role of LTB4/BLT1 axis in tumor immunology, including cytokine-based tumor vaccine, however, remains unknown. We here demonstrated that BLT1-deficient mice rejected subcutaneous tumor challenge of GM-CSF gene-transduced WEHI3B (WGM) leukemia cells (KO/WGM) and elicited robust antitumor responses against second tumor challenge with WEHI3B cells. During GM-CSF-induced tumor regression, the defective LTB4/BLT1 signaling significantly reduced tumor-infiltrating myeloid-derived suppressor cells, increased the maturation status of dendritic cells in tumor tissues, enhanced their CD4(+) T-cell stimulation capacity and migration rate of dendritic cells that had phagocytosed tumor-associated antigens into tumor-draining lymph nodes, suggesting a positive impact on GM-CSF-sensitized innate immunity. Furthermore, KO/WGM mice displayed activated adaptive immunity by attenuating regulatory CD4(+) T subsets and increasing numbers of Th17 and memory CD44(hi)CD4(+) T subsets, both of which elicited superior antitumor effects as evidenced by adoptive cell transfer. In vivo depletion assays also revealed that CD4(+) T cells were the main effectors of the persistent antitumor immunity. Our data collectively underscore a negative role of LTB4/BLT1 signaling in effective generation and maintenance of GM-CSF-induced antitumor memory CD4(+) T cells.

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