Abstract: Background and purpose: Women with BRCA1 mutations have an increased risk of breast and ovarian cancer. However, it is unclear how the mutation in a single allele of BRCA1 contributes to ovarian carcinogenesis. Thus, establishment of an immortalized cell line carrying BRCA1 mutation may provide a useful model to study the tumorigenesis. Methods: We isolated and established an ovarian surface epithelial cell line OSE236 from a woman carrying an allelic 185delAG mutation of BRCA1 who treated in Wuxi People’s Hospital. Then, by using retroviral system-mediated techniques, we stably silenced p53 with a pair of specific shRNA, consecutively introduced human telomerase reverse transcriptase (hTERT) catalytic subunit and oncogenic HRAS to establish a series cell lines and tested their growth, senescence, cell cylces and tumorigenecity. Results: We successfully constructed an immortalized cell line OSE236/p53i/hTERT. But the cell line OSE236/p53i/hTERT/HRAS generated by further transfection with oncogenic HRAS into the immortalized cells failed to induce transformation in vitro and in vivo. Analysis of the cell lines showed that cellular senescence was inhibited as the activity of β-galactosidase was decreased in the immortalized cell line OSE236/p53i/hTERT, compared with the parental cell line OSE236, and that the BRCA1 mutation occured in all cell lines. Cell cycles were markedly increased, and the related cell cycle regulatory factors such as CDK4, Cyclin B1/Cyclin D1/Cyclin E were up-regulated in immortalized cells. The immortalized cell line was passaged over 100 times in cultured dishes. Conclusion: Although we failed to transform the immortalized cells into tumorigenic cells, this immortal cell line carrying an allelic BRCA1-185delAG mutation may provide a valuable cell model to study the BRCA1 mutation-associated ovarian or breast tumorigenesis.