Objective To investigate the etfect of microenvironment simulated by colon carcinoma homogenate supernatant on the differentiation and development of human dendritic ceils (DCs), and to investigate the function of vascular endothelial growth factor A (VEGF-A) during this process . Methods Fresh colon carcinoma and peri-cancer tissues were collected to prepare homogenate supernatant. The pe-ripberal blood mononuclear cells were isolated and cultured with 1640 medium including rhGM-CSF and rhIL-4. Then the colon carcinoma homogenate supernatant, peri--carcinoma homogenate supernatant and VEGF-A were added to the cultures at day 2. Antigen of colon carcinoma cell line SW620 was added at day 4 and lipopolysaccharide (LPS) was added at day 6. DCs were collected at day 8 for further study. The con-tent of VEGF-A was tested by ELISA. The morphology and the immunopbenotype of DCs were checked by microscope and flow cytometry, respectively. The expression of CDIa was tested by RT-PCR, and the prolif-eration and killing rate of T cell was measured by CCK-8. Results The content of VEGF-A in the homoge-nate supernatant of colon carcinoma was significantly higher than that of the peri-carcinoma (P ＜ 0. 05). Compared with normal DCs, the cell morphology of colon carcinoma homogenate aupernatant group was in-hibited, and the cell number was decreased. Besides, the positive expression rate of DC surface markers de-creased (P ＜ 0.01). The capacity of mixed lymphocyte reaction (MLR) and killing capacity of T cells de-creased(P ＜0.01). However, there was almost no difference between VEGF-A group and normal DCs on the cell morphology and cell number, and VEGF-A had no obvious inhibition on the expression of DCs sur-face markers (P ＞ 0.05). But VEGF-A group had significantly inhibitory effect on the MLR and T cells kill-ing. Conclusion The tumor microenvironment simulated by the colon carcinoma homogenate supernatant obviously has inhibitory effect on the differentiation and function of DCs, and VEGF-A has the inhibitory effect on DC function, but the inhibitory effect is not through the inhibition of the expression of DC costimu-lators.