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The expression of the KAI1 gene, a tumor metastasis suppressor, is directly activated by p53
Abstract:
KAI1 is a tumor metastasis suppressor gene that is capable of inhibiting the metastatic process in animals. The expression of the KAI1 gene also is found to be down-regulated during the tumor progression of prostate, breast, lung, bladder, and pancreatic cancers in humans, and this down-regulation appears to be at or posttranscription level. We have found that the tumor suppressor gene p53 can directly activate the KAI1 gene by interacting with the 5' upstream region. The p53 responding region is located at approximately 860 bases upstream of the transcriptional initiation site, and it contains a typical tandem repeat of the p53 consensus-binding sequence. A gel-shift mobility analysis showed that this sequence indeed had the ability to bind to the purified p53 protein. Mutations of this sequence abolished the responsiveness to p53 and also the binding ability to the p53 protein. Furthermore, immunohistochemical analysis of 177 samples of human prostate tumors revealed that the expression of the KAI1 gene was correlated strongly to that of the p53 gene and that the loss of these two markers resulted in poor survivals of patients. Our data indicate a direct relationship between p53 and KAI1 genes and suggest that the loss of p53 function, which is commonly observed in many types of cancer, leads to the down-regulation of the KAI1 gene, which may result in the progression of metastasis.
Insights
The tumor suppressor gene p53 directly activates the KAI1 gene, inhibiting metastasis. Loss of p53 function down-regulates KAI1, promoting cancer progression and poor patient survival.
Area of Science:
- Molecular Biology
- Cancer Research
- Genetics
Background:
- KAI1 acts as a tumor metastasis suppressor gene.
- KAI1 expression is down-regulated in various human cancers, including prostate, breast, lung, bladder, and pancreatic cancers.
- This down-regulation occurs at or post-transcription levels during tumor progression.
Purpose of the Study:
- To investigate the regulatory relationship between the tumor suppressor gene p53 and the KAI1 gene.
- To determine if p53 directly activates KAI1 expression.
- To explore the clinical implications of the p53-KAI1 interaction in prostate cancer.
Main Methods:
- Identifying the p53 response region in the KAI1 gene's 5' upstream region.
- Utilizing gel-shift mobility assays to confirm p53 binding to the identified sequence.
- Performing immunohistochemical analysis on human prostate tumor samples.
Main Results:
- The tumor suppressor gene p53 directly activates the KAI1 gene by binding to a specific sequence approximately 860 bases upstream of the transcriptional initiation site.
- Mutations in this p53-binding sequence abolished both p53 responsiveness and p53 protein binding.
- A strong correlation was observed between KAI1 and p53 gene expression in 177 human prostate tumors.
- Loss of both KAI1 and p53 expression was associated with poor patient survival.
Conclusions:
- The p53 and KAI1 genes exhibit a direct regulatory relationship.
- Loss of p53 function, common in many cancers, leads to KAI1 down-regulation.
- Down-regulation of KAI1 may contribute to cancer metastasis and progression.