Objective To investigate the expressions of metastasis suppressor 1 (MTSS1 )and calcium activated protein 43 (Cap43)in esophageal squamous cell carcinoma (ESCC)tissue,and to clarify the relationship between the expressions of MTSS1,Cap43 and the clinicopathological features of ESCC.Methods 80 cases of ESCC tissue and 30 cases of normal adjacent-cancer tissue were collected,and the protein and mRNA expressions of MTSS1 and Cap43 in ESCC tissue and normal tissue were detected by streptavidin-perosidase (SP)immunohistochemistry and RT-PCR;their relationships with the clinicopathological features of ESCC were analyzed.Results The positive expression rate of MTSS1 in normal esophagus tissue was significantly higher than that in ESCC tissue detected by SP (83.3%vs 21.3%,P<0.01)and RT-PCR (0.703±0.085 vs 0.295±0.065,P<0.01),However,the positive expression rate of Cap43 in normal esophagus tissue was significantly lower than that in ESCC tissue by SP method (16.7%vs 76.3%,P<0.01)and by RT-PCR (0.236±0.052 vs 0.693±0.078,P<0.01).The mRNA expression levels of MTSS1 and Cap43 in ESCC tissue were significantly related with the invasive extent, histological differentiation,TNM stage,and lymphatic metastases (P<0.05)of ESCC,but not related with the age,sex,tumor size and pathological type (P>0.05). The mRNA expression of MTSS1 was negatively correlated with the expression of Cap43 (r=-0.457,P<0.05).Conclusion The low-expression of MTSS1 and over-expression of Cap43 in ESCC tissue may contribute to tumor invasion and metastasis;the imbalance of MTSS1 and Cap43 may be one of the mechanisms of tumor invasion and metastases.