Synergistic effect of rapamycin and cisplatin in endometrial cancer cells.
BACKGROUND
Mammalian target of rapamycin (mTOR) inhibitors modulate signaling pathways involved in cell cycle progression, and phase 2 trials for endometrial cancer are currently being conducted. Because rapamycin is known to enhance the cytotoxicity of chemotherapeutic drugs, the authors' goal was to examine the effects of rapamycin and cisplatin in endometrial cancer cell lines.


METHODS
By using Ishikawa and ECC-1 cells, cell proliferation was assessed after exposure to rapamycin, cisplatin, or both in combination. The combination index (CI) was calculated using the method of Chou and Talalay. Apoptosis was evaluated by flow cytometry. Immunoblot analysis was performed to assess expression of S6 kinase 1 and the DNA mismatch repair proteins, MSH2 and MSH6. mTOR small interfering (siRNA) was transfected into the cell lines, and proliferation and apoptosis were assessed after exposure to cisplatin.


RESULTS
Cisplatin inhibited growth in a dose-dependent manner in both cell lines (median inhibition concentration of 8-13 muM). Simultaneous exposure of cisplatin in combination with rapamycin resulted in a significant synergistic antiproliferative effect (CI < 1). Rapamycin increased cisplatin-induced apoptosis and stimulated expression of MSH2 and MSH6 in the cisplatin-treated cell lines. Cell growth was significantly decreased in cells transfected with mTOR siRNA and treated with cisplatin compared with either alone (CI < 1). Transfection of mTOR siRNA did not induce apoptosis, but combined treatment with cisplatin increased apoptosis over that of cisplatin alone.


CONCLUSIONS
The results of the current study provide evidence of a synergistic relation between rapamycin and cisplatin in both inhibition of cell growth and induction of apoptosis. This suggests that rapamycin and cisplatin may be a rational combination of a targeted therapy for endometrial cancer.
Bae-Jump
Victoria L
VL
Department of Obstetrics and Gynecology, University of North Carolina, Chapel Hill, NC, USA. vbae@unch.unc.edu
Zhou
Chunxiao
C
Boggess
John F
JF
Gehrig
Paola A
PA
D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002945:Cisplatin / Q000008:administration & dosage*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004354:Drug Screening Assays, Antitumor; D004357:Drug Synergism; D016889:Endometrial Neoplasms / Q000188:drug therapy*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051718:MutS Homolog 2 Protein / Q000378:metabolism; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D020123:Sirolimus / Q000008:administration & dosage*; D058570:TOR Serine-Threonine Kinases; D014162:Transfection
D004268:DNA-Binding Proteins; C094443:G-T mismatch-binding protein; D011494:Protein Kinases; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; C497172:MSH2 protein, human; D051718:MutS Homolog 2 Protein; D002945:Cisplatin; D020123:Sirolimus