Involvement of cyclin B1 in progesterone-mediated cell growth inhibition, G2/M cell cycle arrest, and apoptosis in human endometrial cell.
BACKGROUND
Progesterone plays an important role in the proliferation and differentiation of human endometrial cells (hECs). Large-dose treatment with progesterone has been used for treatment of endometrial proliferative disorders. However, the mechanisms behind remain unknown.


METHODS
To investigate the role of cyclin B1 in proliferation and differentiation of hECs in menstrual cycle, the expression of cyclin B1 throughout the menstrual cycle was evaluated in hECs. To determine the effects of progesterone on the proliferation, cell cycle progression and apoptosis of hECs and to test if cyclin B1 is involved in these effects, progesterone and/or Alsterpaullone (Alp, a specific inhibitor of Cyclin B1/Cdc2) were added to primary hECs. Cellular proliferation was evaluated with MTT test, cell cycle with propidium iodide (PI) staining and flow cytometry, apoptosis with FITC-Annexin V and the expression of cyclin B1 with Western blotting.


RESULTS
The expression level of cyclin B1 in secretory endometria was significantly lower than in proliferative endometria (p < 0.01). Progesterone significantly inhibited the growth of hECs in a concentration-dependent manner (P < 0.01). The treatment with progesterone significantly decreased the expression of cyclin B1, increased the proportions of cell in G2/M phase, and apoptotic cells (P < 0.05 for all). The presence of Alp significantly enhanced the effects of progesterone on cyclin B1 down-regulation, G2/M cell cycle arrest and induction of apoptosis (P < 0.01 for all).


CONCLUSIONS
Our findings suggest that cyclin B1 is a critical factor in proliferation and differentiation of hECs. Progesterone may inhibit cell proliferation, mediate G2/M cell cycle arrest and induce apoptosis in hECs via down-regulating Cyclin B1.
Tang
Li
L
Department of Reproductive Endocrinology, Women's Hospital, School of Medicine, Zhejiang University, Hangzhou, China.
Zhang
Yu
Y
Pan
Hong
H
Luo
Qiong
Q
Zhu
Xiao-Ming
XM
Dong
Min-Yue
MY
Leung
Peter Ck
PC
Sheng
Jian-Zhong
JZ
Huang
He-Feng
HF
D000328:Adult; D017209:Apoptosis / Q000502:physiology*; D001552:Benzazepines / Q000494:pharmacology; D015153:Blotting, Western; D002453:Cell Cycle / Q000502:physiology*; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000502:physiology*; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D004396:Coloring Agents; D056744:Cyclin B1 / Q000096:biosynthesis / Q000502:physiology*; D004717:Endometrium / Q000166:cytology*; D005260:Female; D005434:Flow Cytometry; D016195:G2 Phase / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D011374:Progesterone / Q000494:pharmacology*; D013778:Tetrazolium Salts; D013844:Thiazoles
D001552:Benzazepines; D004396:Coloring Agents; D056744:Cyclin B1; D007211:Indoles; D013778:Tetrazolium Salts; D013844:Thiazoles; C120793:alsterpaullone; D011374:Progesterone; C022616:thiazolyl blue