Silibinin inhibits glioma cell proliferation via Ca2+/ROS/MAPK-dependent mechanism in vitro and glioma tumor growth in vivo.
Anticancer activity of silibinin, a flavonoid, has been demonstrated in various cancer cell types. However, the underlying mechanism and in vivo efficacy in glioma were not elucidated. The present study was undertaken to determine the effect of silibinin on glioma cell proliferation in vitro and to examine whether silibinin inhibits tumor growth in vivo. Silibinin resulted in inhibition of proliferation in a dose- and time-dependent manner, which was largely attributed to cell death. Silibinin induced a transient increase in intracellular Ca2+ followed by an increase in reactive oxygen species (ROS) generation. The silibinin-induced cell death was prevented by EGTA, calpain inhibitor and antioxidants (N-acetylcysteine and Trolox). Western blot analysis showed that silibinin also induced ROS-dependent activation of extracellular signal-regulated kinase, p38 kinase, and c-Jun N-terminal kinase. Inhibitors of these kinases prevented the silibinin-induced cell death. Silibinin caused caspase activation and the silibinin-induced cell death was prevented by caspase inhibitors. Glioma cell migration was also decreased by silibinin treatment. Oral administration of silibinin in animals with subcutaneous U87MG glioma cells reduced tumor volume. Subsequent tumor tissue analysis showed a decrease in Ki-67 positive cells, an increase in TUNEL-positive cells, and caspase activation. These results indicate that silibinin induces a caspase-dependent cell death via Ca2+/ROS/MAPK-mediated pathway in vitro and inhibits glioma growth in vivo. These data suggest that silibinin may serve as a potential therapeutic agent for malignant human gliomas.
Kim
Kwang Won
KW
Department of Neurosurgery, College of Medicine, Pusan National University, Pusan 602-739, Korea.
Choi
Chang Hwa
CH
Kim
Thae Hyun
TH
Kwon
Chae Hwa
CH
Woo
Jae Suk
JS
Kim
Yong Keun
YK
D000975:Antioxidants / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D001932:Brain Neoplasms / Q000473:pathology*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects*; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D005910:Glioma / Q000473:pathology*; D006801:Humans; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D007202:Indicators and Reagents; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D000077385:Silybin; D012838:Silymarin / Q000494:pharmacology
D000975:Antioxidants; D007202:Indicators and Reagents; D017382:Reactive Oxygen Species; D012838:Silymarin; D000077385:Silybin; D020928:Mitogen-Activated Protein Kinases; D053148:Caspase 3; D002118:Calcium