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Cyclin E mRNA overexpression in epithelial ovarian cancers: inverse correlation with p53 protein accumulation
T Sawasaki1, K Shigemasa, Y Shiroyama
1Department of Obstetrics and Gynecology, Kure National Hospital, Chugoku Cancer Center, Kure, Japan.
Objective:
We investigated the relationship between cyclin E mRNA overexpression and p53 protein accumulation in epithelial ovarian cancers.
Methods:
mRNA was isolated and cDNA was prepared from 36 epithelial ovarian tumors (three adenomas, three low malignant potential tumors, and 30 carcinomas), and six normal ovaries. The cyclin E mRNA expression levels relative to an internal control, beta-tubulin, were determined by semiquantitative polymerase chain reaction (PCR). Cyclin E and p53 protein expression in ovarian cancer tissues were examined by immunohistochemistry using the same series of samples. Fisher exact test of significance and an unpaired t test were used for statistical analysis.
Results:
Considerable levels of cyclin E mRNA were detected in all normal ovaries and ovarian tumor samples examined by semiquantitative PCR amplification. mRNA levels of cyclin E were significantly higher in nine of 30 (30%) ovarian cancers compared with those in normal ovaries. The immunohistochemical expression of cyclin E protein was confirmed in the nuclei of tumor cells in 13 of 30 (43%) ovarian cancers. p53 protein accumulation was detected in 12 of 30 (40%) ovarian cancers examined. There was a significant inverse correlation between cyclin E mRNA overexpression and p53 protein accumulation (P <.01, Fisher exact test).
Conclusions:
Cyclin E mRNA overexpression frequently occurs in ovarian cancers without p53 protein accumulation. Cyclin E might have an important effect on the development of a limited number of ovarian cancers.