AIM To investigate the interference ofmethionine.free parenteral nutrition plus 5-Fu(-MetTPN+5-Fu)in gastric cancer cell kineticsand the side effects of the regimen.METHODS Fifteen patients with advancedgastric cancer were randomly divided into twogroups,7 patients were given preoperatively aseven-day course of standard parenteralnutrition in combination with a five-day courseof chemotherapy(sTPN+5-Fu),while the other8 patients were given methionine-deprivedparenteral nutrition and 5-Fu(-MetTPN+5-Fu).Cell cycles of gastric cancer and normal mucosawere studied by flow cytometry(FCM).Bloodsamples were taken to measure the serumprotein,methionine(Met)and cysteine(Cys)levels,and liver and kidney functions.RESULTS As compared with the resultsobtained before the treatment,the percentage ofG_0/G_1 tumor cells increased and that of S phasedecreased in the-MetTPN+5-Fu group,while thecontrary was observed in the sTPN+5-Fu group.Except that the ALT,AST and AKP levels wereslightly increased in a few cases receiving-MetTPN+5-Fu,all the other biochemicalparameters were within normal limits.Serum Cys level decreased slightly after the treatmentin both groups.Serum Met level of patientsreceiving sTPN+5-Fu was somewhat higher aftertreatment than that before treatment;however,no significant change occurred in the -MetTPN+5-Fu group,nor operative complications in bothgroups.CONCLUSION -MetTPN+5-Fu exerted asuppressive effect on cancer cell proliferation,probably through a double mechanism ofcreating a state of“Met starvation”adverse tothe tumor cell cycle,and by allowing 5-Fu to killspecifically cells in S phase.Preoperative short-term administration of -MetTPN+5-Fu had littleundesirable effect on host metabolism. AIM To investigate the interference of methionine. Free parenteral nutrition plus 5-Fu (-MetTPN + 5-Fu) in gastric cancer cell kinetics and the side effects of the regimen. METHODS Fifteen patients with advanced gastric cancer were randomly divided into twogroups, 7 patients were given preoperatively aseven-day course of standard parenteral nutrition in combination with a five-day course of chemotherapy (sTPN + 5-Fu), while the other 8 patients were given methionine-deprivedparenteral nutrition and 5-Fu (-MetTPN + of gastric cancer and normal mucosawere studied by flow cytometry (FCM). Bloodsamples were taken to measure the serumprotein, methionine (Met) and cysteine ​​(Cys) levels, and liver and kidney functions .RESULTS As compared with the resultsobtained before the treatment, the percentage ofG_0 / G_1 tumor cells increased and that of S phase created in the-MetTPN + 5-Fu group, while thecontrary was observed in the sTPN + 5-Fu group. Except that the ALT, AST and AKP levels wereslightly increased in af ew cases receiving-MetTPN + 5-Fu, all the other biochemical parameters were within normal limits. Serum Cys level decreased slightly after the treatment in both groups. Serum Met level of patients receiving sTPN + 5-Fu was somewhat higher aftertreatment than that before treatment; however , no significant change occurred in the -MetTPN + 5-Fu group, nor operative complications in both groups. CONCLUSION- MetTPN + 5-Fu exerted asuppressive effect on cancer cell proliferation, probably through a double mechanism ofcreating a state of “Met starvation ”adverse tothe tumor cell cycle, and by allowing 5-Fu to killspecifically cells in S phase. Preoperative short-term administration of-MetTPN + 5-Fu had littleundesirable effect on host metabolism.