Sulforaphane induces cell cycle arrest by protecting RB-E2F-1 complex in epithelial ovarian cancer cells.
BACKGROUND
Sulforaphane (SFN), an isothiocyanate phytochemical present predominantly in cruciferous vegetables such as brussels sprout and broccoli, is considered a promising chemo-preventive agent against cancer. In-vitro exposure to SFN appears to result in the induction of apoptosis and cell-cycle arrest in a variety of tumor types. However, the molecular mechanisms leading to the inhibition of cell cycle progression by SFN are poorly understood in epithelial ovarian cancer cells (EOC). The aim of this study is to understand the signaling mechanisms through which SFN influences the cell growth and proliferation in EOC.


RESULTS
SFN at concentrations of 5-20 microM induced a dose-dependent suppression of growth in cell lines MDAH 2774 and SkOV-3 with an IC50 of ~8 microM after a 3 day exposure. Combination treatment with chemotherapeutic agent, paclitaxel, resulted in additive growth suppression. SFN at ~8 microM decreased growth by 40% and 20% on day 1 in MDAH 2774 and SkOV-3, respectively. Cells treated with cytotoxic concentrations of SFN have reduced cell migration and increased apoptotic cell death via an increase in Bak/Bcl-2 ratio and cleavage of procaspase-9 and poly (ADP-ribose)-polymerase (PARP). Gene expression profile analysis of cell cycle regulated proteins demonstrated increased levels of tumor suppressor retinoblastoma protein (RB) and decreased levels of E2F-1 transcription factor. SFN treatment resulted in G1 cell cycle arrest through down modulation of RB phosphorylation and by protecting the RB-E2F-1 complex.


CONCLUSIONS
SFN induces growth arrest and apoptosis in EOC cells. Inhibition of retinoblastoma (RB) phosphorylation and reduction in levels of free E2F-1 appear to play an important role in EOC growth arrest.
Bryant
Christopher S
CS
Department of Surgery, Wayne State University, 4100 John R Street, Detroit, MI 48201, USA.
Kumar
Sanjeev
S
Chamala
Sreedhar
S
Shah
Jay
J
Pal
Jagannath
J
Haider
Mahdi
M
Seward
Shelly
S
Qazi
Aamer M
AM
Morris
Robert
R
Semaan
Assaad
A
Shammas
Masood A
MA
Steffes
Christopher
C
Potti
Ravindra B
RB
Prasad
Madhu
M
Weaver
Donald W
DW
Batchu
Ramesh B
RB
D017209:Apoptosis / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D004273:DNA, Neoplasm / Q000096:biosynthesis; D050687:E2F1 Transcription Factor / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D017879:Isothiocyanates; D009361:Neoplasm Invasiveness; D020411:Oligonucleotide Array Sequence Analysis; D010051:Ovarian Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D017239:Paclitaxel / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D016160:Retinoblastoma Protein / Q000378:metabolism*; D016196:S Phase / Q000187:drug effects; D013454:Sulfoxides; D013861:Thiocyanates / Q000494:pharmacology*; D014945:Wound Healing / Q000187:drug effects
D018797:Cell Cycle Proteins; D004273:DNA, Neoplasm; D050687:E2F1 Transcription Factor; D017879:Isothiocyanates; D016160:Retinoblastoma Protein; D013454:Sulfoxides; D013861:Thiocyanates; C016766:sulforaphane; D017239:Paclitaxel