[Identification and characterization of stem cells in an ovarian cancer cell line and examination their drug resistance].

OBJECTIVE

To isolate side population (SP) cells from an established ovarian cancer (OC) cell line, characterize these cells, and examine their drug resistance.

METHODS

SP and non-SP (NSP) cells were isolated by fluorescence-activated cell sorting (FACS), and cultured in differential conditions, then detected their SP ratio to compare their capability of differentiation and self-renewal. Moreover, SP and NSP cell tumorigenesis was examined by subcutaneous and intraperitoneal injection of these cells to nonobes ediabetic (NOD)-severe combined immundeficient (SCID) mice. Drug resistance to cisplatin was examined by cell counting kit-8 (CCK-8).

RESULTS

SP cells could be isolated stablly and insistently. There was (4.81 ± 0.43)% of SP cells in the established OC cell line and (4.89 ± 0.33)% of SP cells after cultured the isolated SP cells in differentiation condition, and there was no significant different between these two quantities (P > 0.05). However, after cultured the NSP cells, there was only (0.10 ± 0.03)% of SP cells which was significantly lower than that contained in the OC cell line (P < 0.01). In the tumorigenesis assay 1.0 × 10(3) SP cells were injected subcutaneously and formed the xenografted tumors in 6 weeks (3/3), and 1.0 × 10(4) NSP cells were injected subcutaneously and did not form xenografted tumors in 12 weeks (0). The tumorigenic capability of SP cells was higher than that of NSP cells (P < 0.01). Both the original and the xenografted tumors were low differentiated serous cystadenocarcinomas and expressed the ovarian serous cystadenocarcinomas CA125 marker after stained by HE and immunohistochemistry. Simultaneously, the SP cells were also capable to form tumors as shown by intraperitoneal injection. In the drug resistance assay shown that the 50% inhibitory concentration (IC50) of the SP and NSP cells were respectively (2.33 ± 0.14) µg/ml and (1.60 ± 0.04) µg/ml (P < 0.05). After treated the unsorted OC cells with cisplatin, the quantity of SP cells increased to (40.10 ± 4.22)% and there was significant difference, when compared to the untreated cells which was (4.81 ± 0.43)% (P < 0.01). The SP cells survival rate was (58.7 ± 3.3)% when treated with cisplatin at its IC50 dose, and the rate decreased to (7.2 ± 1.3)% (P < 0.01) when verapamil was present.

CONCLUSIONS

The SP cells could be isolated from the established OC cell line. They had the capacities of self-renewal, differentiation, and tumorigenesis, and the new tumor demonstrated the original tumor's phenotype. The SP cells also had stem cells' biological characteristics and is resistant to cisplatin.