Direct intratumoral introduction of therapeutic or regulatory genes is a developing technology with potentialapplication for cancer gene therapy.Macrophage inflammatory protein-I beta(MIP-Iβ)is a chemokine whichcan chemoattract immune cells such as T cells.In the present study,murine colorectal adenocarcinoma CT26cells were transfected with a recombinant adenovirus (AdhMIP-Iβ)carrying the human MIP-Iβ gene.24 hpost-transfection,hMIP-1β levels reached approximately 980 pg/ml in supernatants of 10~6 hMIP-Iβ-transfectedCT26 cells.Moreover,the supernatants exhibited chemotactic activity for CD8~+ T cells,CD4~+ T cells,NK cellsand immature DCs.Intratumoral injection of AdhMIP-Iβ significantly inhibited tumor growth and prolongedthe survival time of tumor-bearing mice.Intratumoral hMIP-Iβ gene transfer also induced powerfultumor-specific CTL responses in vivo.The therapeutic effects of hMIP-Iβ gene therapy were greatly reducedfollowing in vivo depletion of both CD4~+ and CD8~+ cells,but were unaffected by depletion of single T cellsubsets.Immune cell depletion experiments also revealed that NK cells played an important role inhMIP-1β-induced antitumor responses.These results suggest that intratumoral expression of hMIP-1β has thepotential effect to induce host antitumor immunity and may prove to be a useful form of cancer gene therapy.Cellular & Molecular Immunology.2004;1(3):199-204. Direct intratumoral introduction of therapeutic or regulatory genes is a developing technology with potentialapplication for cancer gene therapy. Macrophage inflammatory protein-I beta (MIP-Iβ) is a chemokine whichcan chemoattract immune cells such as T cells. In the present study, murine colorectal adenocarcinoma CT26 cells were transfected with recombinant adenovirus (AdhMIP-Iβ) carrying the human MIP-Iβ gene.24 hpost-transfection, hMIP-1β levels reached approximately 980 pg / ml in supernatants of 10 -6 hMIP-Iβ- transfected CT26 cells. Moreover, the supernatants illustrative chemotactic activity for CD8 ~ + T cells, CD4 ~ + T cells, NK cells and immature DCs. Intratumoral injection of AdhMIP-Iβ significantly inhibited tumor growth and prolonged the survival time of tumor- bearing mice. Intratumoral hMIP-Iβ gene transfer also also induced powerfultumor-specific CTL responses in vivo. The therapeutic effects of hMIP-Iβ gene therapy were greatly reduced in vivo depletion of both CD4 ~ + and CD8 ~ + cells, but were unaffected by depletion of single T cellsubsets. Immune cell depletion experiments also revealed that NK cells played an important role in hMIP-1β-induced antitumor responses. These results suggest suggest that intratumoral expression of hMIP-1β has the potential effect to induce host antitumor immunity and may prove to be a useful form of cancer gene therapy. Cellular & Molecular Immunology. 2004; 1 (3): 199-204.