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Understanding the essential mechanisms by which cancer develops in association with Li-Fraumeni syndrome has been insufficient, in part because of the lack of an appropriate model of human cells. Here we describe successful culture of human ovarian surface epithelial cells from a patient with Li-Fraumeni syndrome with a single allelic germline p53 mutation in exon 5. We immortalized these cells by the consecutive introduction of small interfering RNA to p53 or pRb followed by introduction of human telomerase reverse transcriptase (hTERT). After 50 proliferative passages, the cells still showed epithelial morphology, elevated telomerase activity, and continuing robust growth. Silencing p53 or pRb sharply decreased the numbers of cells in G0/G1 and increased the numbers in S and G2/M; immortalization of these cells with hTERT enhanced these changes. Silencing p53 or pRb and ectopically expressing hTERT had different effects on cell-cycle regulatory proteins including p15, p16, and p21. Finally, the immortalized cells were proved nontumorigenic but were still heterozygous for the p53 mutation, with some chromosome abnormalities. These cells represent an improved immortalized human cell model that will be useful for investigating initial events in the development of ovarian cancer associated with Li-Fraumeni syndrome and for seeking molecular therapeutic targets for various types of cancer.

98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA