Down-regulation of hTERT expression plays an important role in 15-deoxy-Delta12,14-prostaglandin J2-induced apoptosis in cancer cells.
The cyclopentenone prostaglandin 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2) has been shown to possess antineoplastic activity in human cancers of various origins. However, the mechanism of the antineoplastic activity of 15d-PGJ2 remains to be completely elucidated. It has been reported that inhibiting the expression of human telomerase reverse transcriptase (hTERT), a major determinant of telomerase activity, induces rapid apoptosis in cancer cells. In this study, we investigated the effect of 15d-PGJ2 on hTERT expression. Treatment with 30 microM 15d-PGJ2 for 72 h induced apoptosis in the colon cancer cells LS180. 15d-PGJ2 treatment decreased hTERT protein expression in a dose-dependent manner. Down-regulation of hTERT expression by hTERT-specific small inhibitory RNA induced apoptosis. These results indicate that the down-regulation of hTERT expression by 15d-PGJ2 plays an important role in its proapoptotic properties. Since 15d-PGJ2 reduced hTERT mRNA expression, we examined the effect of 15d-PGJ2 on the DNA-binding activity of c-Myc, specificity protein 1 (Sp1) and estrogen receptor (ER) to the hTERT gene promoter using an electrophoretic mobility shift assay. 15d-PGJ2 attenuated the DNA-binding of all three transcriptional factors. Further, we observed that 15d-PGJ2 inhibited the DNA binding of these factors by different mechanisms; suppressed c-Myc mRNA expression, enhanced Sp1 protein degradation via the ubiquitin-proteasome pathway and inhibited ERbeta phosphorylation at serine residues. We conclude that hTERT down-regulation by 15d-PGJ2 plays an important role in its proapoptotic properties. Furthermore, 15d-PGJ2 inhibits the transcriptional activity of c-Myc, Sp1 and ER by three different mechanisms and results in the transcriptional repression of the hTERT gene.
Department of Clinical Laboratory Medicine, Sapporo Medical University School of Medicine, Chuo-ku, Sapporo 060-8543, Japan. watanabn@sapmed.ac.jp
Mikako
M
Moriai
Naoki
N
Tsuji
Daisuke
D
Kobayashi
Kageaki
K
Kuribayashi
Naoki
N
Watanabe
D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D003110:Colonic Neoplasms / Q000235:genetics / Q000473:pathology*; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000502:physiology; D019073:HT29 Cells; D006801:Humans; D011401:Promoter Regions, Genetic / Q000187:drug effects; D015230:Prostaglandin D2 / Q000031:analogs & derivatives* / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D011960:Receptors, Estrogen / Q000378:metabolism; D016329:Sp1 Transcription Factor / Q000378:metabolism; D019098:Telomerase / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D014407:Tumor Cells, Cultured; D054875:Ubiquitination / Q000187:drug effects
C097240:15-deoxy-delta(12,14)-prostaglandin J2; C489427:MYC protein, human; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D011960:Receptors, Estrogen; D016329:Sp1 Transcription Factor; C509186:TERT protein, human; D019098:Telomerase; D015230:Prostaglandin D2