The Effect And Mechanism Of5-FU And Capecitabine Metronomic Chemotherapy On Gastric Cancer In Vitro And In Vivo

Background and ObjectiveIn clinic,most of the drugs used for gastric cancer are compounds with cytotoxicity activities.These have strong side effects and are more prone to drug resistance,which limits the clinical usage.Metronomic chemotherapy emerging not too long ago that is totally different from the traditional dose regimen of chemotherapy and shows satisfying results in preclinical research and clinical studies recently.It not only inhibits the tumor proliferation,but also inhibits the angiogenesis in tumor through decreasing the endothelial cells.Compared to traditional chemotherapy,metronomic chemotherapy has advantages of lower side effects and could reduce the possibility of drug resistance.Whether metronomic chemotherapy will show effective treatment outcomes for the gastric cancer and it may serve as novel treatment method need to be addressed.Thus,in the current study,we compared the traditional chemotherapy and metronomic treatment methods for 5-FU analogs in the gastric cancer cellsfor cellular proliferation,apoptosis and tumor growth in vivo,evaluated the toxicology effects of the methods and angiogenesis inhibition activities of these treatment methods.The results may guide the metronomic chemotherapy treatment in clinic in future.Methods(1)We evaluated the effects of 5-FU on the inhibition of proliferation and apoptosis induction in vivo and in vitro;(2)The tube formation assay using HUVEC was applied to determine the suppression activities in angiogenesis and the secreted VEGF and PDGF levels were also determined under the chemotherapy treatments;(3)We compared the MVD status and the VEGF expression level in the tumor tissues after the metronomic and traditional chemotherapy;(4)The circulating CEP in the peripheral blood of mouse was estimated by the way of flow cytometry and the circulating VEGF and PDGF levels were also performed.Results(1)Metronomic chemotherapy with 5-FU showed obvious direct inhibition of gastric cancer proliferation but weaker than traditional dose regimen group.No statistical significance of difference between the metronomic group and the negative control was noticed.However,theamount,total length and the number of junction formation in the in vitro tube formation assay were significantly less than traditional dose regimen and negative control in the metronomic group.Both SGC-7901 and AGS showed a lower expression level of VEGF in the culture supernatant in the metronomic group compared to the other two control group(All P<0.01).(2)The average tumor volume in the xenograft model was significantly smaller than the negative control(All P<0.01)and was comparable to the traditional dose regimen(P=0.531 for 5-FU and P=0.296 for Capecitabine)in 5-FU and Capecitabine treatment.A similar trend was also obtained for the average tumor weight.(3)The body weight of the mice in the metronomic group surpassed that of traditional dose regimen group for5-FU(P < 0.05)and was comparable to that of negative control in Capecitabine(P=0.41).(4)The cellular proliferation and apoptosis was significantly lower in the metronomic group than that of traditional dose regimen for both 5-FU and Capecitabine treated mice(All P<0.01).(5)The metronomic regimen induced a significantly lower MVD and VEGF expression level than that of traditional dose regimen(All P<0.05).(6)The proportion of CEP in the peripheral blood of mice is lower in the metronomic group than that of the other two groups(All P<0.05).And the levels of VEGF and PDGF in the peripheral blood of mice was lowerin the metronomic group as expected compared to traditional chemotherapy group(All P<0.01).ConclusionIn conclusion,we found that metronomic therapy using 5-FU and Capecitabine could inhibit the growth of gastric cancer cell both in vitro and in vivo,which could be comparable to that in the traditional dose regimen and is superior due to its small side effects.Anti-angiogenesis activities play an important role in the metronomic therapy of 5-FU and Capecitabine to fight against cancer.These results suggested that metronomic treatment is a novel effective treatment method for gastric cancer in future.