Objective To study the effect of all trans retinoic acid on growth of xenograft tumor and its metastasis in nude mice Methods Human gastric cancer BGC 823 and MKN 45 cells were inoculated into spleen subcapsule of nude mice, respectively The nude mice were subsequently administered with all trans retinoic acid every other day Food consuming and body weight of nude mice were measured weekly Six weeks later, the nude mice were killed Xenograft tumors in spleen and metastatic tumors in liver were pathologically examined Microvessel density in the tumors was detected immunohistochemically, and serum carcinoembryonic antigen was measured by radioimmunoassay Results After the nude mice were fed with all trans retinoic acid, the growth of splenic tumor and its liver metastasis were inhibited and the metastatic rates decreased by 50% (BGC 823) and 33 3% (MKN 45), respectively The microvessel density in splenic and hepatic tumors reduced by 28 58% and 35 47% (BGC 823), 19 45% and 14 52% (MKN 45), respectively The concentration of carcinoembryonic antigen decreased by 50 24% (BGC 823) and 48 10% (MKN 45) Conclusion All trans retinoic acid may effectively inhibit the growth of xenograft tumor in spleen and its metastasis to liver in nude mice, which can be corroborated by the decrease of carcinoembryonic antigen and microvessel density Objective To study the effect of all trans retinoic acid on growth of xenograft tumor and its metastasis in nude mice Methods Human gastric cancer BGC 823 and MKN 45 cells were inoculated into spleen subcapsule of nude mice, respectively The nude mice were subsequently administered with all trans retinoic acid every other day Food consuming and body weight of nude mice were measured weekly for six weeks later, the nude mice were killed Xenograft tumors in spleen and metastatic tumors in liver were pathologically examined in Microvessel density in the tumors was immunohistochemically, and serum carcinoembryonic antigen was measured by radioimmunoassay Results After the nude mice were fed with all trans retinoic acid, the growth of splenic tumor and its liver metastasis were inhibited and the metastatic rates decreased by 50% (BGC 823) and 33 3% (MKN 45), respectively The microvessel density in splenic and hepatic tumors reduced by 28 58% and 35 47% (BGC 823), 19 45% and 14 52% (MKN 45), respectively The concentration of carcinoembryonic antigen decreased decreased by 50 24% (BGC 823) and 48 10% (MKN 45) Conclusion All trans retinoic acid may effectively inhibit the growth of xenograft tumor in spleen and its metastasis to liver in nude mice, which can be corroborated by the decrease of carcinoembryonic antigen and microvessel density