| KAIl gene,a new metastasis suppressor gene,was firstly reported by Dong J.T. in 1995 (Science). Although the metastatic suppressing function of KAIl has been proved in various tumors and cancer cell lines with different metastasis potential,the mechanism of KAIl expression and its functions is still largely unknown. In present study,we explore the critical functions of KAIl gene and its protein in various levels by means of modern technique in the fields of cell biology,molecular biology,immunology and experimental animals. Furthermore,the relationship between KAIl and tumor suppressor gene p53 is discussed,which may associate with metastasis of tumor. In addition,various chemetheraputic drugs,such as VP 16,are found to specially increase KAI1/CD82 protein level. Thus,this study will provide new idea and theoretical evidence for clinical therapyFirstly,KAI1/CD82 protein expression level was detected with immunohistochemistry in surgically tumor tissues from colon cancer patients. The result showed that KAI1/CD82 expression was closely correlated with the stage of metastasis. Tumor tissues from high metastasis expressed low level of KAI1/CD82 protein,whereas high level of KAI1/CD82 protein was expressed in the relative low metastatic tumor tissues. The relationship between KAIl mRNA expression and malignance of tumor was also detected with in situ hybridization,which showed negative relevance These results indicate that the expression of KAIl gene isconsistent with its protein expression in clinical tumor samples,thus may be used clinically as an indicator to show the grade of metastasis and malignance,which is closely related with stages of cancer malignance.In the study of cell level,Flowcytometry and Westen Blot were used to investigate KAI1/CD82 protein level in various tumor cell lines. Results showed that KAI1/CD82 protein were expressed in most cancer cell lines,and after treatment of cells with VP16,upregulation of KAI1/CD82 level was shown in different cell lines. Furthermore,among 3 gastric cancer cell lines,SGC-7901 cells showed the strongest expression of KAI1/CD82 induced by VP16. In addition,the effect of VP16 on inducting KAI1/CD82 protein expression was time-dependent. Accordingly,we came to a conclusion that VP16 has much better effect on upregulation of KAI1/CD82 protein in cell lines with high metastatic potential. Aside from VP16,we also investigated the effects of some other drugs and chemicals with anticancer effect on regulation of KAI2/CD82 protein. Results showed that ATRA plus VP16 or Taxol treatment could effectively induced KAI1/CD82 expression in gastric cancer cells.Secondary,we discussed the relevance between KAI1 and p53 proteins. Results from Western Blot showed that VP16 can upregulated not only KAI1/CD82 protein expression but also p53 protein expression in cancer cell lines,and this effect was also time-dependent. Under the observation of Laser-Scanning Confocal microscope,location of KAI1/CD82 protein in BGC-823 cells was clearly visualized in the area of cell membrane;after VP16-treated for 12 hours,KAI1/CD82 protein translocated to pemuclear region;in time of 24 hour treatment by VP16,KAI1/CD82 protein was translocated to nucleus completely. During the course of KAI/CD82 protein translocation in BGC-823 cells,p53 protein still localized in nucleus,no matter how long the cells were treated with VP16. Furthermore,the location of p63 protein (amember of p53 family) was also detected. Similar result was seen:p63 remained in nucleus with or without VP-16 treatment.Last,with the help of the animal model,we proved that VP16 could effectively suppress the experimental liver metastasis of SGC-7901 cells in nude mice. The growth of xenograft tumor was inhibited in nude mice fed with VP16,which showed less amount of liver metastatic lesion. Higher level of KAI1/CD82 protein expression was also detected with immunohistochemistry in nude mice fed with VP16.Originalities of our work:1. Discovered,for the first time,that translocation of KAI1/CD82 protein fr... |
