Cellular responses to cancer chemopreventive agent D,L-sulforaphane in human prostate cancer cells are initiated by mitochondrial reactive oxygen species.
OBJECTIVE
Present study was undertaken to elucidate the mechanism of cellular responses to D,L-sulforaphane (SFN), a highly promising cancer chemopreventive agent.


METHODS
Mitochondrial DNA deficient Rho-0 variants of LNCaP and PC-3 cells were generated by culture in the presence of ethidium bromide. Apoptosis was assessed by analysis of cytoplasmic histone-associated DNA fragmentation and activation of caspase-3. Immunoblotting was performed to determine the expression of apoptosis- and cell cycle-regulating proteins. Generation of reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and cell cycle distribution were measured by flow cytometry.


RESULTS
The Rho-0 variants of LNCaP and PC-3 cells were significantly more resistant to SFN-induced ROS generation, apoptotic DNA fragmentation, disruption of MMP, cytosolic release of cytochrome c, and G2/M phase cell cycle arrest compared with corresponding wild-type cells. SFN-induced autophagy, which serves to protect against apoptotic cell death in PC-3 and LNCaP cells, was also partially but markedly suppressed in Rho-0 variants compared with wild-type cells. SFN statistically significantly inhibited activities of mitochondrial respiratory chain enzymes in LNCaP and PC-3 cells.


CONCLUSIONS
These results indicate, for the first time, that mitochondria-derived ROS serve to initiate diverse cellular responses to SFN exposure in human prostate cancer cells.
Xiao
Dong
D
Department of Pharmacology & Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA.
Powolny
Anna A
AA
Antosiewicz
Jedrzej
J
Hahm
Eun-Ryeong
ER
Bommareddy
Ajay
A
Zeng
Yan
Y
Desai
Dhimant
D
Amin
Shantu
S
Herman-Antosiewicz
Anna
A
Singh
Shivendra V
SV
D016588:Anticarcinogenic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3 / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D004579:Electron Transport / Q000187:drug effects; D017353:Gene Deletion; D006801:Humans; D017879:Isothiocyanates; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000188:drug therapy*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013454:Sulfoxides; D013861:Thiocyanates / Q000494:pharmacology* / Q000627:therapeutic use; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism
D016588:Anticarcinogenic Agents; D017879:Isothiocyanates; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D013454:Sulfoxides; D013861:Thiocyanates; D053148:Caspase 3; D020741:rho GTP-Binding Proteins; C016766:sulforaphane