Non-immunogenic murine hepatocellular carcinoma Hepa1-6 cells expressing the membrane form of macrophage colony stimulating factor are rejected in vivo and lead to CD8+ T-Cell immunity against the parental tumor

Hepatocellular carcinoma is a lethal disease and methods that develop effec tive cellular-based immunotherapy are needed. We retrovirally transduced no n-immunogenic mouse Hepa1-6 hepatoma cells with the gene encoding the membr ane form of macrophage colony stimulating factor (mM-CSF). Excess recombina nt M-CSF and phagocytosis-inhibiting chemicals blocked macrophage-mediated killing of cloned mM-CSF transfected Hepa1-6 hepatoma cells. Macrophages de rived from Hck/(-) Fgr/(-) and Lyn(-)/(-) triple knockout mice, which are i ncapable of performing phagocytosis, failed to kill the mM-CSF transduced c ells. The mM-CSF transfected tumor clones failed to grow when injected into C57BL/6 or C57L/J mice. Splenocytes from these vaccinated mice displayed c ytotoxicity against parental Hepa1-6 cells, but not against B16 and CT-26 t umor cells in vitro. Mice that rejected the mM-CSF transfected Hepa1-6 tumo r subsequently rejected parental Hepa1-6 cells but not the B16 melanoma cel ls when rechallenged. Elimination of the CD8+ effector cells by an anti-CD8 antibody and complement treatment prevented the adoptive transfer of anti- Hepa1-6-specific immunity into naive animals. Thus, mM-CSF provides a metho d of generating effective anti-tumor immune responses by macrophages and cy totoxic T cells against the parental Hepa1-6 cells. Our work suggests that mM-CSF transduced hepatoma cells could be used as a tumor vaccine to stimul ate immune responses against hepatocellular carcinoma.