Antitumor immune response by CX3CL1 fractalkine gene transfer depends on both NK and T cells

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Abstract
The CX3C chemokine fractalkine (CX3CL1) exists as both a membrane‐bound form promoting firm cell‐cell adhesion and a soluble form chemoattracting leukocytes expressing its receptor CX3CR1. When adenoviral vector expressing mouse fractalkine (AdFKN) was transduced to the tumor cells, fractalkine was expressed as both membrane‐bound form on the tumor cells and soluble form in the supernatant in vitro. Intratumoral injection of AdFKN (1×109PFU/tumor) into C26 and B16F10 tumors resulted in marked reduction of tumor growth compared to control (C26: 86.5%, pp+ T lymphocytes 3 and/or 6 days after treatment with AdFKN. Splenocytes from mice treated by AdFKN developed tumor‐specific cytotoxic T cells, and thereby protected from rechallenging with parental tumor cells. Antitumor effects by AdFKN were completely abrogated in both NK cell‐depleted mice and CD8–/– mice, and partially blocked in CD4–/– mice. These data indicated that fractalkine mediates antitumor effects by both NK cell‐dependent and T cell‐dependent mechanisms. This study suggests that fractalkine can be a suitable candidate for immunogene therapy of cancer because fractalkine induces both innate and adaptive immunity.