摘要AIM To investigate the influence of L-methioninedeprived total parentaral nutrition with 5-FU on gastric cancer and host metabolism.``METHODS N-methyI-N-nitro-nitrosoguanidine ( MNNG )induced gastric cancer rats were randomly divided into four groups: Met-containing TPN group (n= 11 ), Metdeprived TPN group (n = 12), Met-containing TPN + 5-FU group (n = 11) and Met-deprived TPN + 5-FU group (n-12). Five rats in each group were sacrificed after 7days of treatment and the samples were taken for examination. The remaining rats in each group were then fed separately with normal diet after the treatment until death, the life span was noted.``RESULTS The tumors were enlarged in Met-containing group and shrank in Met-deprived group markedly after the treatment. The DNA index (DI) of tumor cells and the body weight (BW) of rats had no significant change in the two groups, however, the ratio of tumor cells' S phase was increased The ratio of G2M phase went up in Metcontaining group, but down in Met-deprived group. In the other two groups that 5-FU was added, the BW of rats,and the diameter of tumors, the DI of tumor cells, the S and G2M phase ratio of tumor cells were all decreased,particularly in Met-deprived plus 5-FU group. Pathological examination revealed that the necrotic foci of the tumor tissue increased after Met-deprived TPN treatment, and the nucleoli of tumor cells enlarged. In -MetTPN + 5-FUgroup, severe nuclear damage was also found by karyopyknosis and karyorrhexis, meanwhile there was slight degeneration in some liver and kidney cells. The serum free Met and Cysteine decreased markedly (P<0.001), while other amino acids, such as serum free serine and glutamine increased significantly ( P< 0.005).All the rats died of multiple organ failure caused by cancer metastasis. The average survival time was 18.6 days in Met-containing TPN group. 31 days in Met-deprived TPN group, 27.5 days in Met-containing TPN + 5-FU group, and 43 days in Met-deprived TPN+ 5-FU group (P<0.05).``CONCLUSION Met-deprived TPN causes methionine starvation of tumor cells, and can enhance the anti-tumor effect of 5-FU and prolong the life span of gastric cancerbearing rats.``