AIM: To provide the expression profile of serine protease SNC19/matriptase and its inhibitor hepatocyte growth factor activator inhibitor type 1 (HAI-1) in normal and malignant tissues of gastrointestinal tract at mRNA level for further study on their correlations with tumor progression and metastasis. METHODS: Total RNAs were prepared from 37 samples of colorectal cancer tissues, 40 samples of gastric cancer tissues, and their adjacent normal tissues. The expression of SNC19/matriptase and HAM in these samples was detected by real-time fluorescent quantitative PCR using glyceraldehyde-3-phosphate dehydrogenase as internal standard, and the clinical significance for the correlation with clinicopathological parameters was evaluated. RESULTS: In gastric cancer tissues the expression of HAI-1 and SNC19/matriptase was significantly lower than that in the corresponding adjacent normal tissues (Z=-3.280, P= 0.006; Z=-4.651, P=0.000). HAI-1:SNC19/matriptase ratio showed no difference between normal and malignant tissues (P>0.05). Analysis of clinicopathological parameters showed decreased expression of HAM and HAI-1:SNC19/ matriptase ratio associated with stage Ⅲ/Ⅳ gastric tumors as compared to stage Ⅰ/Ⅱ ones (Z = -2.140, P= 0.031; Z= -2.155, P= 0.031), and with lymph node-positive gastric cancer tissues as compared to lymph node-negative ones (Z= -2.081, P= 0.036; Z= -2.686, P= 0.006). The expression of SNC19/matriptase had no relationship with stages and lymph node metastasis (P>0.05). The expression of HAM and HAM:SNC19/matriptase ratio increased in well-differentiated gastric cancer tissues, but there was no statistical significance (P>0.05). The difference of SNC19/matriptase expression was not significant in gastric cancer tissues of different histological differentiation status (P>0.05). In colorectal cancer tissues, the expression of HAI-1 and SNC19/matriptase was also markedly lower than that in their adjacent normal tissues (Z=-3.100, P=0.002; Z=-2.731, P=0.006), whereas HAI-1:SNC19/matriptase ratio showed no difference. Decreased expression of HAI-1 was associated with increased invasive depth and lymph node metastasis, but there was no statistical significance (P>0.05). The difference of SNC19/matriptase expression and HAI-1: SNC19/matriptase ratio was not significant in different stages and different lymph node metastasis status (P>0.05). The expression of SNC19/matriptase, HAI-1 or HAI-1: SNC19/matriptase ratio showed no difference in colorectal cancer tissues of different histological differentiation status (P>0.05). CONCLUSION: The expressions of SNC19/matriptase and its inhibitor HAI-1 are decreased in gastrointestinal cancer tissues compared to their normal counterparts, and the decreased expression of HAI-1 may correlate with invasion and lymph node metastasis. The possible mechanisms involved need to be further investigated. AIM: To provide the expression profile of serine protease SNC19 / matriptase and its inhibitor hepatocyte growth factor activator inhibitor type 1 (HAI-1) in normal and malignant tissues of gastrointestinal tract at mRNA level for further study on their correlations with tumor progression and metastasis METHODS: Total RNAs were prepared from 37 samples of colorectal cancer tissues, 40 samples of gastric cancer tissues, and their adjacent normal tissues. The expression of SNC19 / matriptase and HAM in these samples was detected by real-time fluorescent quantitative PCR using glyceraldehyde -3-phosphate dehydrogenase as internal standard, and the clinical significance for the correlation with clinicopathological parameters was evaluated. RESULTS: In gastric cancer tissues the expression of HAI-1 and SNC19 / matriptase was significantly lower than that in the corresponding adjacent normal tissues Z = -3.280, P = 0.006; Z = -4.651, P = 0.000). HAI-1: SNC19 / matriptase ratio showed no difference between Normal and malignant tissues (P> 0.05). Analysis of clinicopathological parameters showed decreased expression of HAM and HAI-1: SNC19 / matriptase ratio associated with stage III / IV gastric tumors as compared to stage I / II ones (Z = -2.140, P = 0.031; Z = -2.155, P = 0.031), and with lymph node-positive gastric cancer tissues as compared to lymph node-negative ones (Z = -2.081, P = 0.036; Z = -2.686, P = 0.006) . The expression of SNC19 / matriptase had no relationship with stages and lymph node metastasis (P> 0.05). The expression of HAM and HAM: SNC19 / matriptase ratio increased in well-differentiated gastric cancer tissues, but there was no statistical significance (P > 0.05). The difference of SNC19 / matriptase expression was not significant in gastric cancer tissues of different histological differentiation status (P> 0.05). In colorectal cancer tissues, the expression of HAI- 1 and SNC19 / matriptase was also markedly lower than that that in their adjacent normal tissues (Z = -3.100, P = 0.002; Z = -2.731, P = 0.006),n HAI-1: SNC19 / matriptase ratio showed no difference. Decreased expression of HAI-1 was associated with increased invasive depth and lymph node metastasis, there was no statistical significance (P> 0.05). The difference of SNC19 / matriptase expression and The expression of SNC19 / matriptase, HAI-1 or HAI-1: SNC19 / matriptase ratio was no significant in different stages and different lymph node metastasis status (P> 0.05) cancer tissues of different histological differentiation status (P> 0.05). CONCLUSION: The expressions of SNC19 / matriptase and its inhibitor HAI-1 are decreased in gastrointestinal cancer tissues compared to their normal counterparts, and the decreased expression of HAI- 1 may correlate with invasion and lymph node metastasis. The possible mechanisms involved need to be further investigated.