| Objective: The development and progression of gastric cancer are complex processes which involve the activation of oncogenes and inactivation of tumor-suppressor genes, resulting in the changing of biological behavior of cells in vivo.The Ras association domain family gene 1A (RASSF1A), a novel candidate tumor-suppressor gene mapped on human chromosome 3q21.3, is discovered in 2000 using a expression clone strategy. Ras gene with its important effects in cell proliferation, differentiation, motility and apoptosis, plays a significant role in the process of tumorigenesis and progression.Cathespin L (CL), a cysteine proteinase secreted by tumor cells and their stroma, which is stored in lysosome as the style of proenzyme, can degradate several extracellular matrix (ECM), such as collogen, elastin, fibronectin, laminin .etc and is closely associated with cell junction, therefore it has important effect on the process of tumor invasion and metastasis.To investigate the mRNA expression level of RASSF1A and CL in human gastric cancer tissue and normal gastric mucosa to determine the relationship between expression of the two markers and carcinogenesis, progression, invasion and metastasis, and biological behavior, respectively. It appears vital clinical significant to research the molecule mechanisms of development and progression of gastric cancer.Methods: In this study, we select 42 samples of gastric cancer, 42 samples of normal gastric mucosa (>5.0cm). All patients had gastrectomy in the 4th hospital of HeBei Medical University from June 2008 to December 2008. All these samples are without chemotherapy and radiotherapy or biotherapy before surgery, which are proved by pathology. In this study, we use reverse transcription polymerase chain reaction (RT-PCR) to detect the expressions of RASSF1A and CL mRNA in gastric cancer tissues and normal gastric mucosa. The Correlations between the expressions of RASSF1A and CL mRNA and the biological behavior of gastric cancer are analyzed, including sex, age, tumor location, size, gross type, histological grade, invasion depth, metastasis of lymph node and TNM stage etc. GAPDH is designed as reference standard. All statistical analyses were carried out with SPSS 16.0 and p<0.05 were considered significant.Result:1 The expression level of RASSF1A mRNA in gastric cancer tissue (0.42±0.27) is significantly lower than that in normal gastric mucosa (1.27±0.48) (p <0.05).2 The expression level of CL mRNA in gastric cancer tissue (2.39±0.46) is significantly higher than that in normal gastric mucosa (1.20±0.34) (p <0.05).3 The expressions of RASSF1A mRNA in the group of poor histological grade (0.36±0.21) were significantly lower than the group of well histological grade (0.68±0.36)(p<0.05); the expressions of RASSF1A mRNA in the group of III+IV stage (0.35±0.18) were significantly lower than group of I+II stage (0.95±0.23)(p <0.05)。4 The expressions of CL mRNA in the group of T3+T4 (2.47±0.44) were significantly higher than T1+T2 (1.91±0.27) (p<0.05); the expressions of CL mRNA in the group with metastasis of lymph node (2.50±0.42) were significantly higher than without lymph node metastasis (2.17±0.48) (p <0.05); the expressions of CL mRNA in the group of III+IV stage (2.46±0.44) were significantly higher than group of I+II stage (1.86±0.25) (p <0.05).5 The expression level of RASSF1A mRNA is not correlated with sex, years, tumor location, size, gross type, invasion depth and metastasis of lymph node.6 The expression level of CL mRNA is not correlated with sex, age, tumor location, size, gross type and histological grade.7 The expression level of RASSF1A mRNA in gastric cancer tissue is significantly lower than that in normal gastric mucosa; whereas, the expression level of CL mRNA in gastric cancer tissuet is significantly higher than that in normal gastric mucosa; there is some extent negative correlation between the expression level of RASSF1A and CL mRNA in gastric cancer tissue (rS=-0.25), however, the different is not significant.Conclusion: 1 The expression level of RASSF1A mRNA is significantly lower in gastric cancer tissue than that in normal gastric mucosa; whereas, the expression level of CL mRNA is significantly higher in gastric cancer tissue than that in normal gastric mucosa, which reveals that RASSF1A and CL play a role in the progression of gastric cancer.2 The expression level of RASSF1A in gastric cancer tissue becomes significantly lower along with the histological grade to poor and the TNM stage to higher, which suggests that the low-expression of RASSF1A is related to the histological grade and the progression of clinicopathology.3 The expression level of CL in gastric cancer tissue becomes significantly higher along with the depth of invasion to deeper, metastasis of lymph node, and the TNM stage to higher, which suggests that the high-expression of CL is related to the invasion and metastasis of gastric cancer and the progression of clinicopathology.4 The expression level of RASSF1A mRNA is not correlated with sex, years, tumor location, size, gross type, invasion depth and metastasis of lymph node.5 The expression level of CL mRNA is not correlated with sex, age, tumor location, size, gross type and histological grade.6 There is some extent antagonism effect between the expression level of RASSF1A and CL mRNA in gastric cancer tissue, however, the different is not significant, considering the small sample.
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