In cancer therapy, specific radioprotection of normal tissue and antiangiogenesis are the ways to increase the therapeutic gain. Here we describe a novel gene therapy, which uses attenuated salmonella SL3261 as oral vectors carrying with cDNA of platelet factor 4 (PF4) or that of a truncated PF4. After oral administrations of attenuated salmonella carrying with cDNA of PF4 or truncated PF4, the survival rate of mice which received sublethal total body irradiation was improved by 50%, In comparison with the control mice, the bone marrow cells obtained from the mice of experimental group increased (13.2±8.3, 15.7±1.5 vs 4.1 ± 2.0 P<0.05) at day 7 after TBI, and the number of HPP-CFC of bone marrow cells also increased significantly (15.7±9, 11.7±5 vs 4.3±4.1 P<0.05) at day 7, suggesting a stimulating effect of PF4 on hematopoietic recovery. This gene therapy also caused significant tumor regression. The microvessel density (MVD) of tumors was significantly decreased in the group of treated mice compared to controls (4.25±0.96, 4.08±0.56 vs 11±0.83 P<0.05). Analysis TUNEL kit revealed an increase in the number of apoptosis cells in tumors of mice treated by SL3261 carrying with cDNA of PF4 or a truncated PF4. GFP expression and gene integration were detected in the liver, kidney, spleens, intestine, peripheral blood, bone marrow and tumors samples of the SL3261 treated mice, and the expression of GFP was higher in tumors than that in other tissues. These data demonstrate for the first time a dual biological function of PF4 against tumor growth and radiation injury. These results also demonstrate that attenuated salmonella can be used in vivo as a DNA delivery vector

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