[Analysis of the characteristics of side population cells in the human ovarian cancer cell line OVCAR-3].
OBJECTIVE
To identify the presence of side population (SP) cells in human ovarian cancer cell line OVCAR-3 and to investigate whether SP cells have the characteristics of cancer stem cells.


METHODS
SP and non-SP (NSP) cells from OVCAR-3 were isolated by fluorescence-activated cell sorting after being stained by DNA-binding dye Hoechst 33342. Limiting dilution transplantation assay, real-time PCR, and drug sensitivity assay were performed to compare the tumorigenic ability, differentiation ability in vivo, the mRNA expression of "stemness" marker (Oct-4, Klf4, and Nanog) and ATP-binding cassette (ABC) transporter (ABCG2, ABCB1, and ABCC2), and response to multiple drugs (cisplatin, paclitaxel, doxorubicin, and mitoxantrone) between SP and NSP cells.


RESULTS
A few of SP cells [(1.13 ± 0.39)%] which were sensitive to reserpine were identified in OVCAR-3 cells. The injection of as few as 10(2) SP cells initiated tumors in two of five mice. Tumor latency was 52 - 61 days. However, the NSP cells did not generate any tumors in mice until 10(4) NSP cells were injected (two of five mice). Tumor latency was 64 - 98 days. Tumorigenicity of SP cells was enhanced by at least 100-fold than that of NSP cells. The SP cells regenerated both SP [(2.09 ± 0.73)%] and NSP populations in vivo with a fraction size that was comparable to the original population. The mRNA expression of "stemness" genes Oct-4, Klf4 and ABC transporters ABCG2, ABCC2 genes were elevated in SP cells compared to NSP cells, the fold changes were 1.95 ± 0.41 (P < 0.05), 4.26 ± 0.63 (P < 0.01), 3.22 ± 0.36 (P < 0.01), and 1.76 ± 0.26 (P < 0.01), respectively. The relative activity of SP and NSP cells were 0.757 ± 0.105 versus 0.474 ± 0.035 (P < 0.01), 0.521 ± 0.092 versus 0.384 ± 0.073 (P < 0.05), 0.742 ± 0.051 versus 0.526 ± 0.088 (P < 0.01), and 0.690 ± 0.096 versus 0.466 ± 0.112 (P < 0.01) when they exposed to 0.25 µg/ml cisplatin, 0.01 µmol/L paclitaxel, 0.25 µmol/L doxorubicin, and 0.05 µg/ml mitoxantrone, respectively.


CONCLUSIONS
SP cells from OVCAR-3 have enhanced self-renewal, differentiation, and tumor-initiating capacity compared to NSP cells. The mRNA expression of stemness genes and ABC transporters are markedly elevated in SP cells, which showed resistance to multiple chemotherapeutic drugs and have characteristics of cancer stem-like cells. Therefore, SP phenotype could be used as a marker to isolate the cancer stem-like cells in ovarian cancer.
Department of Obstetrics and Gynecology, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing 100730, China.
Li-Jing
LJ
Luo
Zhe
Z
Zhao
Jian-Fang
JF
Zeng
Bing
B
Liang
Jia-Xin
JX
Yang
Dong-Yan
DY
Cao
Keng
K
Shen
D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic; D019008:Drug Resistance, Neoplasm; D005260:Female; D005434:Flow Cytometry; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D000090062:Kruppel-Like Factor 4; D051379:Mice; D008819:Mice, Nude; D000089762:Multidrug Resistance-Associated Protein 2; D009368:Neoplasm Transplantation; D014411:Neoplastic Stem Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D050814:Octamer Transcription Factor-3 / Q000235:genetics / Q000378:metabolism; D010051:Ovarian Neoplasms / Q000378:metabolism / Q000473:pathology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D058985:Side-Population Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D013194:Staining and Labeling / Q000379:methods
C000715087:ABCC2 protein, human; D018528:ATP-Binding Cassette Transporters; D000970:Antineoplastic Agents; D018398:Homeodomain Proteins; C000715467:KLF4 protein, human; C000715468:Klf4 protein, mouse; D000090062:Kruppel-Like Factor 4; D000089762:Multidrug Resistance-Associated Protein 2; D050814:Octamer Transcription Factor-3; D012333:RNA, Messenger