TY - JOUR
T1 - Novel mechanism of reduced proliferation in ovarian clear cell carcinoma cells
T2 - Cytoplasmic sequestration of CDK2 by p27
AU - Itamochi, Hiroaki
AU - Yoshida, Tomokazu
AU - Walker, Cheryl Lyn
AU - Bartholomeusz, Chandra
AU - Aoki, Daisuke
AU - Ishihara, Hideki
AU - Suzuki, Nao
AU - Kigawa, Junzo
AU - Terakawa, Naoki
AU - Ueno, Naoto T.
N1 - Funding Information:
This work was supported by grants from the US National Institutes of Health ( R01HD046282 to C. L. Walker, R01CA127562 to N. T. Ueno) and Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan ( 17244120 to H. Itamochi, 20249066 to N. Terakawa).
Funding Information:
Daisuke Aoki has received a research grant from Sysmex Corporation.
PY - 2011/9
Y1 - 2011/9
N2 - Objective: Ovarian clear cell carcinoma (CCC) carries a poor prognosis because of its insensitivity to chemotherapy. We previously found an association between reduced proliferation of CCC and chemoresistance; here we investigated the mechanism of the reduced proliferation. Methods: We assessed cell cycle function by measuring the activity of cyclin-dependent kinases (CDKs) and the protein expression of cyclins, the CDK inhibitors, and p53 in 22 ovarian cancer cell lines and 60 human ovarian cancer specimens. We examined the cellular location of p27, p27 phosphorylated at threonine 157 (p27Thr157), and CDK2 protein by confocal microscopy and western blotting. We tested the effect of the inhibitor of phosphatidylinositol-3-kinase (PI3K) and small interfering RNA against p27 (si-p27) in two CCC cell lines (RMG-I, SMOV-2). Results: CCC cells had lower CDK2 activity and higher p27 expression than serous adenocarcinoma (SA) cells. Low CDK2 activity correlated with high p27 protein expression. p27Thr157 sequestered CDK2 in the cytoplasm, but PI3K inhibitor or si-p27 maintained CDK2 in the nucleus and restored its activity. In human specimens, CDK2 was mostly in the cytoplasm and was spatially associated with p27; CDK2 activity was lower in the CCC than in the SA specimens. si-p27 enhanced the cytotoxic effect of cisplatin, doxorubicin, and gemcitabine in both RMG-I cells and SMOV-2 cells. Conclusions: Reduced CDK2 activity via the cytoplasmic sequestration of CDK2 by p27Thr157 may contribute to suppression of CCC proliferation. A prospective study is needed to determine whether the cytoplasmic sequestration of CDK2 results in the chemoresistance of CCC.
AB - Objective: Ovarian clear cell carcinoma (CCC) carries a poor prognosis because of its insensitivity to chemotherapy. We previously found an association between reduced proliferation of CCC and chemoresistance; here we investigated the mechanism of the reduced proliferation. Methods: We assessed cell cycle function by measuring the activity of cyclin-dependent kinases (CDKs) and the protein expression of cyclins, the CDK inhibitors, and p53 in 22 ovarian cancer cell lines and 60 human ovarian cancer specimens. We examined the cellular location of p27, p27 phosphorylated at threonine 157 (p27Thr157), and CDK2 protein by confocal microscopy and western blotting. We tested the effect of the inhibitor of phosphatidylinositol-3-kinase (PI3K) and small interfering RNA against p27 (si-p27) in two CCC cell lines (RMG-I, SMOV-2). Results: CCC cells had lower CDK2 activity and higher p27 expression than serous adenocarcinoma (SA) cells. Low CDK2 activity correlated with high p27 protein expression. p27Thr157 sequestered CDK2 in the cytoplasm, but PI3K inhibitor or si-p27 maintained CDK2 in the nucleus and restored its activity. In human specimens, CDK2 was mostly in the cytoplasm and was spatially associated with p27; CDK2 activity was lower in the CCC than in the SA specimens. si-p27 enhanced the cytotoxic effect of cisplatin, doxorubicin, and gemcitabine in both RMG-I cells and SMOV-2 cells. Conclusions: Reduced CDK2 activity via the cytoplasmic sequestration of CDK2 by p27Thr157 may contribute to suppression of CCC proliferation. A prospective study is needed to determine whether the cytoplasmic sequestration of CDK2 results in the chemoresistance of CCC.
KW - CDK2
KW - Cell cycle
KW - Clear cell
KW - Ovarian carcinoma
KW - p27
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UR - http://www.scopus.com/inward/citedby.url?scp=80051550209&partnerID=8YFLogxK
U2 - 10.1016/j.ygyno.2011.05.003
DO - 10.1016/j.ygyno.2011.05.003
M3 - Article
C2 - 21652059
AN - SCOPUS:80051550209
SN - 0090-8258
VL - 122
SP - 641
EP - 647
JO - Gynecologic Oncology
JF - Gynecologic Oncology
IS - 3
ER -
