Abstract:Objective:To investigate the relationship between the expression of T lymphoma invasion and metastasis inducing factor 1 (Tiam1), ras-related C3 botulinum toxin substrate 1 (Rac1) with the invasion and metastasis of gastric cancer. Methods: The expressions of Tiam1 and Rac1 proteins in 60 cases of gastric cancer and paracarcioma gastric mucosa tissues were detected using Strept Avidin-Biotin Complex(SABC) immunohistochemical method,and the correlation between the expression of Tiam1, Rac1 and clinicopathological parameters of gastric cancer were analysed. Results: (1)There was negative staining of Tiam1 protein in paracarcioma gastric mucosa tissues, while positive staining was detected in gastric cancer tissues(78.33%)(P< 0.01). (2)The positive staining rate of Rac1 in gastric cancer tissues(71.67%) was significantly higher than that in paracarcioma gastric muscosa(18.33%)(P< 0.01). (3)As the degree of histologic differentiation of gastric cancer decreased, depth of invasion increased, stage of TNM was upgraded or lymph node metastasis appeared, the positive staining rate of Tiam1 and Rac1 proteins in gastric cancer tissues significantly increased(P< 0.05), but there was no obvious correlation between their expression with the sex, age of patient, primary pathological location or size of gastric cancer(P> 0.05). (4) The expression of Rac1 in patients with positive staining of Tiam1 was significantly higher than that in patients with negative staining(P< 0.01). Conclusions:Positive correlation existed between the expression of Tiam1, Rac1 and the infiltration and metastasis of gastric cancer, which suggested that combined examination of Tiam1 and Rac1 in gastric cancer can be helpful to forecast its pathobiological behavior.