| BACKGROUNDColorectal carcinoma is one of the most forms of malignancy and metastasis is the major cause of mortality in the population. Identifications on the occurance of metastasis or not and the influence factors on it are very important to estimate prognosis or instruct treatments. So working out the metastasis-associated factors and finding out the preventive and therapeutic methods become the most urgent in the modern oncological research.Metastasis is the process with multiple-steps and stages. Recently studies have showed that many specific genes are involved in the process of metastasis, mainly classified as metastasis accelerating genes and metastasis suppressor genes. Those genes may regulate every stage of metastasis by the cooperative or inhibitive interactions, which could finally affect the biological characters of tumor cells.More than hundreds of genes have been reported to be involved in the regulations of metastasis in colorectal carcinoma. Studies on these genes have offered important clues for illustrating the molecular mechanisms of metastasis. However, they are still far to fully explain the complexity and diversity of metastasis. And the detecting methods of them are mostly limited by analysis of the expressions of only one or several genes, which makes it difficult to understand the interactions of genes and find the new genes. So finding a systemic, efficient, easy and time-saving method becomes vital to solve this problem.One of the most important ways to understand the basic of thecarcinogenesis and development of tumors is to clone the differentially expressed genes and analyze their functions. Recently several differentially expressed gene cloning techniques, such as suppression subtractive hybridization, two-dimensional gel electrophoresis and mass spectrometry have become the important way to illustrate the molecular mechanisms of the carcinogenesis and development of tumors, clone the aimed genes and find new genes. Analyses on differentially expressed genes in complex organisms concern with the applications of the transcriptome and proteome methods, which has advantages and limitations respectively. The combination of studies at the RNA level and the protein level is the effective way to fully and systematically illustrate the molecular mechanisms of tumor metastasis.PURPOSE AND METHODSIn our studies, a pair of high metastatic cell lines SW620 and low metastatic cell lines SW480 of human colorectal carcinoma was used. They has the same genetic background and have been widely used in national or international research. Firstly, experiments of the growth curve, metastasis in vivo and invasion in vitro were carried out between the pair of cell lines to observe the influences of long-term passage on their metastatic phenotypes. Secondly, at the RNA level, SSH and blue-white screening techniques were performed to construct the metastasis-related genes subtracted cDNA library of colorectal carcinoma. Partial positive clones were screened and validated by differential screening and Northern Blot techniques. Preliminary analyses on characters or functions of the acquired differentially expressed fragments were then made. Finally, at the protein level, the protein expression spectrums of the pair of cell lines were obtained by 2-DE technique. After the software analysis, several differentially expressed proteins were picked out and then digested in gel. Their characters were primarily identified by mass spectrometry. Our studies not only help to illustrate the molecular mechanisms of metastasis in colorectal carcinoma, but provide newinformation for net public database and would have the potentials to find new targets for clinical diagnosis at early stage, drug screening and prognosis estimation.RESULTS1. Studies on the biological characters related with metastasis between the pair of colorectal carcinoma cell linesHigh metastatic cell lines SW620 cell lines of human colorectal carcinoma had the higher proliferative ability than low metastatic cell...
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