[Identification and characterization of ovarian cancer stem-like cells from primary tumor.].

Objective: To study whether the primary ovarian cancer cells containing cancer stem cells and its characterization in serum-free culture condition.

Methods: The primary cancer cells were isolated from one stage III, grade 2 serous adenocarcinoma tissue. Cells were cultured in serum-free culture system supplemented with epidermal growth factor, basic fibroblast growth factor, leukemia inhibitory factor and insulin, or standard serum-containing system. Methyl thiazolyl tetrazolium assay, quantitative PCR analysis, flow-cytometric analysis and xenograft experiments in vivo were performed.

Results: The primary cancer cells could maintain and form cell sphere in serum-free culture system. These cells had the properties of self-renewal, overexpression of stem cell marker genes Nanog, Oct-4, Sox-2, nestin, ABCG2, CD(133) and CD(117). By contrast with the differentiated cells under standard serum-containing culture conditions, these sphere-forming cells were more resistant to cisplatin and paclitaxel after treated 48 and 72 hours (61% vs. 31%, 73% vs. 29%, P < 0.05). With Hoechst 33342 exclusion assay, only 21.83% of sphere-forming cells were positive with the dye, compared with 83.04% positive cells in differentiated cells (P < 0.01). Only 500 sphere-forming cells resulted subcutaneous xenograft tumors. All of these xenografts were categorized as serous adenocarcinomas, overexpression of CA(125) and cytokeratin-7 which were original tumor phenotype of ovarian cancer.

Conclusion: The sphere-forming cells isolated from primary ovarian cancer tissues have the characterization of cancer stem cell and may be a more reliable model system for understanding the biology of primary human tumors.