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Expression of p21WAF1/CIP1 is heterogeneous and unrelated to proliferation index in human ovarian carcinoma
N Barboule1, P Mazars, V Baldin
1Laboratoire de Pharmacologie et Toxicologie Fondamentales, CNRS, Toulouse, France.
Abstract:
The growth-inhibitory protein p21WAF1/CIP1 is a potent inhibitor of various cyclin-dependent kinases, the expression of which is regulated at the transcriptional level by p53-dependent and -independent mechanisms. We examined p21WAF1/CIP1 mRNA and protein expression in 5 human ovarian-adenocarcinoma cell lines, 1 primary culture of normal surface epithelium and 17 human ovarian-tumor specimens. In culture cells, the p21WAF1/CIP1 protein was expressed in normal ovarian epithelial cells and at a high level in the adenocarcinoma 2008 and IGROV-1 cell lines. p21 WAF1/CIP1 expression was undetectable at the mRNA and protein levels in the NIH-OVCAR-3 and SKOV-3 ovarian-adenocarcinoma cell lines which are respectively mutated and deleted in the p53 gene. Heterogeneous expression of p21WAF1/CIP1 observed in ovarian-cancer cell lines in culture was also found in vivo on tumor specimens. p21WAF1/CIP1 expression is undetectable in 25% of the ovarian biopsies examined. Since it has been found that the p53 gene is mutated in 79% of ovarian cancer, the absence of p21WAF1/CIP1 expression in 25% of these ovarian cancer could not be correlated with p53 mutation. The proliferation index of the 17 tumors showed great variation from one tumor to another. However, no significant correlation was found between p21WAF1/CIP1 expression and the proliferation rate of the tumors.
Insights
The p21WAF1/CIP1 protein, a key cell growth inhibitor, shows varied expression in ovarian cancers. Its absence in some tumors is not linked to p53 gene mutations or tumor proliferation rates.
Area of Science:
- Oncology
- Molecular Biology
- Cell Cycle Regulation
Background:
- The p21WAF1/CIP1 protein is a critical inhibitor of cyclin-dependent kinases, regulating cell growth.
- Its expression is controlled by p53-dependent and -independent pathways.
- Understanding p21WAF1/CIP1 expression is vital in ovarian cancer research.
Purpose of the Study:
- To investigate the expression patterns of p21WAF1/CIP1 mRNA and protein in ovarian cancer.
- To explore the relationship between p21WAF1/CIP1 expression, p53 gene status, and tumor proliferation in ovarian cancer.
Main Methods:
- Analysis of p21WAF1/CIP1 mRNA and protein levels in human ovarian adenocarcinoma cell lines.
- Examination of p21WAF1/CIP1 expression in normal ovarian surface epithelium and ovarian tumor specimens.
- Assessment of p53 gene status and tumor proliferation indices.
Main Results:
- p21WAF1/CIP1 protein was detected in normal ovarian cells and some ovarian cancer cell lines (2008, IGROV-1).
- Expression was undetectable in ovarian cancer cell lines with p53 mutations (NIH-OVCAR-3) or deletions (SKOV-3).
- Heterogeneous p21WAF1/CIP1 expression was observed in vivo; 25% of tumors lacked detectable expression, independent of p53 mutation status or proliferation rate.
Conclusions:
- p21WAF1/CIP1 expression in ovarian cancer is heterogeneous and not solely dependent on p53 mutation status.
- The absence of p21WAF1/CIP1 does not correlate with tumor proliferation rates in ovarian cancer.
- Further research is needed to elucidate the regulatory mechanisms and functional significance of p21WAF1/CIP1 in ovarian tumorigenesis.