CEBPD reverses RB/E2F1-mediated gene repression and participates in HMDB-induced apoptosis of cancer cells.
OBJECTIVE
Recent evidence indicates that a tumor suppressor gene CEBPD (CCAAT/enhancer-binding protein delta) is downregulated in many cancers including cervical cancer, which provides a therapeutic potential associated with its reactivation. However, little is known for CEBPD activators and the effect of reactivation of CEBPD transcription upon anticancer drug treatment. In this study, we identified a novel CEBPD activator, 1-(2-hydroxy-5-methylphenyl)-3-phenyl-1,3-propanedione (HMDB). The purpose of this study is to characterize the mechanism of HMDB-induced CEBPD activation and its potential effect in cancer therapy.


METHODS
Methylation-specific PCR assay, reporter assay, and chromatin immunoprecipitation (ChIP) assay were performed to dissect the signaling pathway of HMDB-induced CEBPD transcription. Furthermore, a consequence of HMDB-induced CEBPD expression was linked with E2F1 and retinoblastoma (RB), which discloses the scenario of CEBPD, E2F1, and RB bindings and transcriptional regulation on the promoters of proapoptotic genes, PPARG2 and GADD153. Finally, the anticancer effect of HMDB was examined in xenograft mice.


RESULTS
We demonstrate that CEBPD plays an essential role in HMDB-mediated apoptosis of cancer cells. HMDB up-regulates CEBPD transcription through the p38/CREB pathway, thus leading to transcriptional activation of PPARG2 and GADD153. Furthermore, increased level of CEBPD attenuates E2F1-induced cancer cell proliferation and partially rescues RB/E2F1-mediated repression of PPARG2 and GADD153 transcription. Moreover, HMDB treatment attenuates the growth of A431 xenografts in severe combined immunodeficient mice mice.


CONCLUSIONS
These results clearly demonstrate that HMDB kills cancer cells through activation of CEBPD pathways and suggest that HMDB can serve as a superior chemotherapeutic agent with limited potential for adverse side effects.
Department of Pharmacology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Yen-Chun
YC
Pan
Chien-Feng
CF
Li
Chiung-Yuan
CY
Ko
Min-Hsiung
MH
Pan
Pei-Jung
PJ
Chen
Joseph T
JT
Tseng
Wen-Chun
WC
Wu
Wen-Chang
WC
Chang
A-Mei
AM
Huang
Esta
E
Sterneck
Ju-Ming
JM
Wang
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D051743:CCAAT-Enhancer-Binding Protein-delta / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured; D015536:Down-Regulation / Q000235:genetics; D050687:E2F1 Transcription Factor / Q000502:physiology*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D007659:Ketones / Q000494:pharmacology*; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D009369:Neoplasms / Q000235:genetics* / Q000473:pathology*; D011407:Propane / Q000031:analogs & derivatives* / Q000494:pharmacology; D016160:Retinoblastoma Protein / Q000502:physiology*; D023041:Xenograft Model Antitumor Assays
C506624:1-(2-hydroxy-5-methylphenyl)-3-phenyl-1,3-propanedione; D050687:E2F1 Transcription Factor; D007659:Ketones; D016160:Retinoblastoma Protein; D051743:CCAAT-Enhancer-Binding Protein-delta; D011407:Propane