Related Experiment Videos
Relationship between p21 expression and mutation of the p53 tumor suppressor gene in normal and malignant ovarian
A A Elbendary1, F D Cirisano, A C Evans
1Department of Obstetrics and Gynecology, Division of Gynecologic Oncology and Department of Surgery, Duke University Medical Center, Durham, North Carolina 27710, USA.
Abstract:
In many cell types, p53-mediated growth inhibition is dependent on induction of p21, which is an inhibitor of cyclin-dependent kinases that are required for cell cycle progression. Failure of mutant p53 proteins to transactivate p21 may lead to uncontrolled proliferation. Because many ovarian cancers have mutations in the p53 gene, we examined p21 levels in normal and malignant ovarian epithelial cells to determine whether p21 expression is dependent on wild-type p53. Normal ovarian epithelial cells and two ovarian cancer cell lines with wild-type p53 expressed readily detectable levels of p21, whereas in p53 null and mutant cell lines, expression of p21 was diminished strikingly. A correlation between the status of the p53 gene and p21 expression also was noted in 23 primary epithelial ovarian cancers. Normal levels of p21 RNA were seen in 4/7 (57%) cancers with wild-type p53, whereas 14/16 (88%) cancers with mutant p53 had reduced p21 expression (P < 0.05). In addition, we found that lambda-irradiation of normal and malignant ovarian epithelial cells with wild-type, but not mutant, p53 resulted in induction of p21. These data are suggestive that induction of p21 is a feature of p53-mediated growth inhibition in normal ovarian epithelial cells. Conversely, mutation of the p53 gene in ovarian cancers usually is associated with decreased p21 expression. The lack of an absolute correlation between p21 expression and the status of the p53 gene in ovarian cancers is consistent with other studies that have suggested that p21 may also be regulated by p53-independent pathways.
Insights
Wild-type p53 induces p21 (cyclin-dependent kinase inhibitor) for growth inhibition in ovarian cells. Ovarian cancers with mutant p53 typically show reduced p21 expression, impacting cell cycle control.
Area of Science:
- Oncology
- Molecular Biology
- Cell Cycle Regulation
Background:
- p53-mediated growth inhibition often relies on p21, a cyclin-dependent kinase inhibitor crucial for cell cycle progression.
- Mutations in the p53 gene can lead to uncontrolled cellular proliferation due to impaired p21 transactivation.
- Ovarian cancers frequently harbor p53 gene mutations, suggesting a potential link between p53 status and p21 expression in these tumors.
Purpose of the Study:
- To investigate the relationship between p53 gene status and p21 expression in normal and malignant ovarian epithelial cells.
- To determine if p21 expression is dependent on wild-type p53 in the context of ovarian cancer.
- To explore the role of p53 in regulating p21 induction in response to DNA damage.
Main Methods:
- Analysis of p21 expression levels in normal ovarian epithelial cells and ovarian cancer cell lines with varying p53 gene status (wild-type, mutant, null).
- Correlation analysis of p21 RNA levels with p53 gene status in 23 primary epithelial ovarian cancers.
- Assessment of p21 induction in response to lambda-irradiation in ovarian cells with wild-type versus mutant p53.
Main Results:
- Normal ovarian epithelial cells and wild-type p53 cancer cell lines exhibited detectable p21 levels.
- p53 null and mutant cell lines showed strikingly diminished p21 expression.
- A significant association was observed between p53 gene status and p21 expression in primary ovarian cancers: 57% of wild-type p53 cancers had normal p21 RNA, while 88% of mutant p53 cancers had reduced p21 (P < 0.05).
- Lambda-irradiation induced p21 in wild-type p53 cells but not in mutant p53 cells.
Conclusions:
- p21 induction appears to be a key component of p53-mediated growth inhibition in normal ovarian epithelial cells.
- Mutations in the p53 gene in ovarian cancers are generally associated with decreased p21 expression.
- The incomplete correlation between p21 expression and p53 status suggests the involvement of p53-independent pathways in p21 regulation in ovarian cancers.