| The incidence of Gastric carcinoma is high in China; it is the first place in digestive malignant tumor and the third place in all malignant tumors. The morbidity of gastric carcinoma is reported 30.1/105. per year. The. Mortality of it is in the top place among malignant tumours. In our country 300.000 patients died from gastric carcinoma each year. Gastric carcinoma behaviors such as depth of invasion. cell differentiation, metastasis of lymphoid nodes (especially invasion or metastasis) play an important role in progression of gastric carcinoma, therefore, the research on the factors which affect biological behaviors of gastric carcinoma is very important for investigating progression, instructing clinical therapies and Judging prognosis of gastric carcinoma. Metastasis of cancer is regulated by metastatic genes and anti-metastatic genes. Tiam1 was identified firstly in 1994 by Habet, through the in vitro selection for invasiveness in T-lymphoma cells. It is reported that Tiam1 is related to malignant tumor metastasis and it promotes metastasizing of malignant tumor.The main function of Tiam1 is to respond to extracellular signals such as cytokines, growth factors, LPA, PDGF, endothelin, bombesin, bradykinin, and then it promotes conversion of inactive Rac1-GDP to the active Rac1-GTP, The activated Rac1 elicits a number of terminal kinases by inducing their phosphorylations on serine(S) and threonine(T) residues. Such kinases include p21ak for dynamicreorganization of actin cytoskeleton (DRAC), p38MAPK for transcription activation, and activition of transcript factors NFκB, AP1 and STAT3 for direct transcription. And by its biological functions: the biological behaviors of cells are regulated, such as reconstruction of cystoskeleton, cell adhesion, cell movement, cell proliferation and differentiation, and even apoptosis. In recent research, SP immunoh-istochemistry has been adopted to detect Tiam1 expression in NSCL (nonsmall-cell lung cancer), and RT-PCR was used to detect Tiam1 expression in nasopharyngeal carcinoma, but the assays may be limited in explaining some question's essence and detecting trace copies. because they cannot quantitate the given genes accurately. In 1996, the Applied Biosystems company introduced real-time fluorescence quantitative PCR technology (RT-FQ-PCR) for the first time. RT-FQ-PCR is such a method where a fluorescent ptobe is added to the PCR reaction, the whole PCR process is monitored by incorperated fluorescence signal at the real times. A standard curve can be achieved finally by which unknown template.of interests could be quantitively analyzed. The technique has been thought as a break-though in PCR measurement from qualitation to quantification. RT-FQ-PCR has been considered the most specific, accurate and reproducible method in the qualitative and quantitive detection for a given gene. RT-FQ-PCR has not been used to detect the exression of Tiam1 by now. For the first time, RT-FQ-PCR was utilized to detect Tiam1 expression in 66 cases of gastric carcinomas. 11 cases ofbenign gastric diseases were included in the study as.the negtaive control. Based on the construction of a standard curve for Tiam1 by TaqMan, we detected Tiam1 expression in tissues from gastric cancers and tissues in para-cacinomas.It was shown that up to 92.42% of the 66 patients was Tiam1 positive in their tissue samples of gastric carcinomas but only 13 of them were found Tiam1 positive in the para-carcinoma tissues with percentage of 19.70% and 1 in 11 samples of the benign gastric diseases was positive in detection of Tiam1 expression. It might illustrate that the expression of Tiam1 transcripts would be a common event in gastric cancers. The median for expressing amount of Tiam1 reached 7.38×105 in carcinoma tissues of the cases in the study, much higher than those of both para-carcinoma tissues and the negative control (0 for both, respectively). It had been pointed out that 13 para-carcinoma samples were Tiam1 positive, and their median was 2.78×104, 1 eighteenth of the amount of expressing in cancerous tissues. Obviously, the transcripts of Tiam1 in gastric carcinoma was significantly more than those in control samples. Analysis in combination with the clinical data, the expressing level of Tiam1 was not related to the ethic factors of the individuals, such as sex or age. The patients were grouped in terms of the degree of cell differentiation in the in situ carcinoma, depth of the tumor invasion, metastasis into lymph nodes and the TNM staging for the patients, the so-called biological behaviors of the tumor cells. It was indicated that thebiological behaviors of gastric cancer closely concerned the expressing levels of Tiam1 in the carcinoma tissue, all with p less than 0.05. For instance, the super- expression of Tiam1 in the carcinoma tissues was accompanied with lower degrees of the cancer cell differentiation, and the deeper the invasion was, the higher were the levels for Tiam1 expression. As the result, the statistical analysis for sum-ranking revealed significant correlation between expressing amount of Tiam1 and staging for TNMs of the patients with gastric carcinomas (P<0.05).Therefore, it is concluded that there may be the gastric carcinoma-related super- expression of Tiam1 in the cancerous tissues and it may reflect the severity of gastric cancers. Quantification for Tiam1 may be a valuable criterion in distinguishing benign from malignant gastric illness. Besides these, it is suggested that the expressing levels of Tiam1 may be correlated with biological behaviors of gastric carcinoma and be involved in pathogenesis of the disease. Tiam1 may become a novel target in the gene-related regimen for gastric cancers.
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