Rottlerin induces apoptosis via death receptor 5 (DR5) upregulation through CHOP-dependent and PKC delta-independent mechanism in human malignant tumor cells.
Rottlerin has been shown to induce antiproliferation and apoptosis of human cancer cell lines. In this study, we demonstrate a novel mechanism of rottlerin-induced apoptosis via death receptor (DR) 5 upregulation. We found that treatment with rottlerin significantly induces DR5 expression both at its messenger RNA and protein levels. Downregulation of DR5 expression with small-interfering RNA (siRNA) efficiently attenuated rottlerin-induced apoptosis, showing that the critical role of DR5 in this cell death. Rottlerin-induced DR5 upregulation was accompanied by CCAAT/enhancer-binding protein-homologous protein (CHOP) protein expression and rottlerin-induced increase of DR5 promoter activity was diminished by mutation of a CHOP-binding site of DR5 promoter. Although rottlerin is known to be as an inhibitor of novel isoforms of protein kinase C (PKC), specifically PKC delta, not only suppression of PKC delta expression by siRNA but also overexpression of wild-type-PKC delta or dominant-negative-PKC delta did not affect the rottlerin-mediated induction of DR5 in our study. These results suggest that rottlerin induces upregulation of DR5 via PKC delta-independent pathway. Furthermore, subtoxic dose of rottlerin sensitizes human cancer cells, but not normal cells, to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis. Thus, DR5-mediated apoptosis, which is induced by rottlerin alone or by the combined treatment with rottlerin and TRAIL, may offer a new therapeutic strategy against cancer.
Lim
Jun Hee
JH
Department of Immunology and Chronic Disease Research Center and Institute for Medical Science, School of Medicine, Keimyung University, 194 DongSan-Dong Jung-Gu, Taegu 700-712, South Korea.
Park
Jong-Wook
JW
Choi
Kyeong Sook
KS
Park
Yong Bok
YB
Kwon
Taeg Kyu
TK
D000098:Acetophenones / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001578:Benzopyrans / Q000494:pharmacology*; D002460:Cell Line; D045744:Cell Line, Tumor; D017931:DNA Primers; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005434:Flow Cytometry; D017930:Genes, Reporter; D005920:Glomerular Mesangium / Q000166:cytology; D006801:Humans; D011401:Promoter Regions, Genetic / Q000187:drug effects; D051745:Protein Kinase C-delta / Q000235:genetics*; D034741:RNA, Small Interfering / Q000235:genetics; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000187:drug effects / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051742:Transcription Factor CHOP / Q000502:physiology*; D014162:Transfection; D015854:Up-Regulation
D000098:Acetophenones; D001578:Benzopyrans; C497249:DDIT3 protein, human; D017931:DNA Primers; D004791:Enzyme Inhibitors; D034741:RNA, Small Interfering; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D051742:Transcription Factor CHOP; C085746:rottlerin; D051745:Protein Kinase C-delta