Objective This study aimed to evaluate the effect of Xiaotan Sanjie Formula-contained serum on DNA methylation of P16 in gastric cancer cell lines to study its mechanism of anticancer.Methods Human gastric cancer cell lines

MKN45 and BGC823 were cultured and Xiaotan Sanjie Formula-containing serum was prepared.Cells were divided into four groups

i.e.blank control group

blank serum group

Xiaotan Sanjie Formula-containing serum group and 5-Aza-CdR group.Cell viability was determined by CCK8.The expression of P16 gene was detected by using RT-PCR.DNA methylation level of P16 gene was detected by Methylight method.Result Cell proliferation was obviously inhibited 72 hours after 5-Aza-CdR or Xiaotan Sanjie Formula-containing serum administered.In the MKN45 cell line

cell proliferation rate was decrease to 76.14% and 83.15% after treated with 5-Aza-CdR and Xiaotan Sanjie Formula-containig serum respectively;in the BGC823 cell line

the above indices were 76.17% and 83.44% respectively.The cell proliferation rate of Xiaotan Sanjie Formula-containing serum group was obviously lower than that of the 5-Aza-CdR group.Both drug containing serum could reverse methylation of P16 gene and increase expression of P16 mRNA.There was significant difference as compared with the blank control group （P<0.05）.Conclusion Xiaotan Sanjie Formula could suppress gastric cancer cell proliferation by reversing DNA methylation of P16 gene.