Effect of whole peptidoglycan of bifidobacterium on proliferation and apoptosis in experimental gastric cancer

OBJECTIVE:To explore the effects of whole peptidoglycan(WPG)from bifidobacterium on proliferation and apoptosis in experimental gastric cancer in vivo.METHODS:Thirty nude mice subcutaneously transplanted with MKN-45 human gastric cancer cells were administered with different doses of WPG and 5-FU by intraperitoneal injection when the tumors were palpable.The weights of the tumors and inhibitory rates were observed.TUNEL staining was used to detect the apoptosis of transplanted tumor cells.The immunohistochemical staining was used to detect the expression of bcl-2,bax and proliferating cell nuclear antigen(PCNA)in the transplanted tumor.RESULTS:The growth rates of the tumors in vivo were obviously slower when intragastric administration of WPG,and the tumor weights were significantly lower than those in the NS group when the study was over,P0.01.But not significantly different from 5-FU group,P0.05.The apoptosis indexes in the three WPG groups and 5-FU group were significantly higher than that in the normal saline group,P0.01.The immunohistochemical staining showed that the expression rate of bcl-2 protein and proliferating cell nuclear antigen were significantly lowed down in the WPG group compared with the normal saline group(P0.05),while the expression of apoptosis-inducing protein and bax was just the opposite.It was greatly up-regulated by WPG,P0.01.CONCLUSIONS:The whole peptidoglycan of bifidobacterium exerts an inhibiting effect on the growth of human gastric cancer in nude mice.The possible antitumor mechanisms are to decrease the proliferating activity of tumor cells or the expression of bcl-2 gene and increase the expression of bax gene,which can induce the apoptosis of the tumor cells.