OBJECTIVETo investigate the effects of direct intratumor injection of the packaged cells with retroviral vector carrying human endostatin (hEN) on the growth inhibition of B16 melanoma in C57/BL6 mice.

METHODSRetroviral vector, pLNC-hEN, was constructed with modified and identified hEN gene. The cell line, PA317, was used to establish ecotropic virus producing cells by transfecting and packing with pLNC-hEN. Then the cells were injected directly into the tumor in C57/BL6 mice bearing B16 melanoma, established by intra-cutaneous injection of B16 cell suspension. The tumor size was measured at different intervals to observe the antitumor effect. Micro-vessel density (MVD) in the tumor tissue was evaluated by immunohistological examination to count the apoptotic cells by TUMEL staining.

RESULTSTumor with diameter of 2 - 3 mm was observed in all mice after 7 - 9 days. The average tumor volume on D3, D5, D7 and D9 after gene transfection was 4.67 +/- 1.1, 22.25 +/- 13.06, 84.17 +/- 43.5 and 155.08 +/- 81.1 mm(3) in the gene therapy group but 136.17 +/- 30.61, 390.17 +/- 220.47, 1 021.67 +/- 537.4 and 2 920.2 +/- 220.01 mm(3) in the control group, the difference of which was statistically significant. The average MVD in the gene therapy and control groups were 8 +/- 2.28 and 28.17 +/- 5.31 while the average apoptotic cell number in the two groups were 23.33 +/- 3.83 and 2.33 +/- 1.21, both of which were statistically significant.

CONCLUSIONThe direct injection of packaged cells carrying hEN gene is able to inhibit the growth of micro-blood vessels and promote tumor cell apoptosis, which ultimately inhibits the growth of B16 melanoma.