:awa LUniveritY. 13-1, Takara-machi, Kana:awa 920. Japan.Summarv To studv the effect of localised secretion of chemokines on tumour growth. the genes for human (hu interleukin 8 (IL-8). hu-MCP-1 (NICAF). hu-MIP-12 (LD78). murine (mu)-MCP-1 (JE). mu-MIP-lx or mu-MIP-2 A-ere introduced. v-ia mammalian expression vectors. into Chinese hamster ovarv (CHO) cells. and the abilitv of transfected cells to form tumours in vivo uas evaluated. The production of hu-IL-8. hu-MIP-lx or mu-MIP-lx bv transfected clones did not influence the growth rate in iitro. but drastically suppressed tumour growth A-hen injected subcutaneouslv (s.c.) into nude mice. However. clones transfected with hu-MCP-1. mu-NMCP-I or mu-MIP-2 did not shou-anv significant difference in growth rate in vivo compared u-ith clones transfected u-ith sector alone. Histological examination of the site of injection of CHO clones transfected w-ith hu-IL-8. hu-MIP-l1 or mu-MIP-lE showed predominantly neutrophilic infiltration. These results indicate that chemokines have potent anti-tumour activitv A-hen released. even at lou-doses. at the tumour site. A-hich mav be mediated by recruitment and targeting of neutrophilic granulocvtes to chemokinereleasing cells. Our studies highlight the potential usefulness of localised chemokine secretion in inducing potent host anti-tumour defensive responses.