Objective     To study the expression of matrix metalloproteinase 8 (MMP-8) in esophageal squamous cell carcinoma (ESCC) and its relationship with tumor invasion and metastasis.     Methods     MMP-8 mRNA expressions in 67 ESCC tissue specimens and in 27 normal tissue specimens were detected by real-time PCR. MMP-8 protein expression in 15 paired specimens of ESCC and in normal tissues were detected by Western blotting. The relationship between MMP-8 expression level and the clinical stage

invasion and metastasis of ESCC was statistic

ally analyzed.     Results     MMP-8 expression was detected in both ESCC tissues and normal tissues

and the expression level in ESCC tissues was significantly lower than that in normal tissues (

P

=0.003 for mRNA expression and

P

=0.031 for protein expression). MMP-8 expression in ESCC tissues had significant differences among T1

T2

T3 and T4 stages (

P

=0.002)

increasing from T1 to T4 stage

and rose when tumor invasion degree heightened. No obvious correlation was found between the MMP-8 mRNA and protein expression levels and lymph node metastasis of ESCC.     Conclusions     Expression of MMP-8 is low in ESCC tissues and increases with elevated invasion degree

which may reflect different mechanisms of MMP-8 in ESCC carcinogenesis and invasion.