CEBPD Reverses RB/E2F1-Mediated Gene Repression and Participates in HMDB-Induced Apoptosis of Cancer Cells

Abstract

Purpose: 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.Experimental Design: 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. Clin Cancer Res; 16(23); 5770-80. Ó2010 AACR.

HMDB and 5-AzadC Combination Reverses Tumor Suppressor CCAAT/Enhancer-Binding Protein Delta to Strengthen the Death of Liver Cancer Cells

“…S2). Consistent with our previous report in cervical cancer (12), a reporter assay showed that the dominant negative form of p38 and CREB repressed HMDB-induced CEBPD reporter activity in liver cancer cells (Supplementary Fig. S3A).…”

“…S3B). CEBPD can induce PPARG2 and GADD153 expression to promote apoptotic cell death (12). CEBPD, PPARG2, and GADD153 were coordinately activated by HMDB or 5-AzadC (Fig.…”

“…These findings indicate that CEBPD may be a common effector in response to inducers of stresses, epigenetic change, and differentiation. HMDB can induce CEBPD expression via activation of the p38 MAPK/CREB pathway (12). To efficiently activate CEBPD to kill cancer cells, we assessed whether CEBPD expression was higher during the combination of two regulations, activation of the p38/CREB pathway and demethylation of the CEBPD promoter ( Supplementary Fig.…”

“…Hydroxymethyldibenzoylmethane (HMDB) has been suggested to serve as a potent anticancer drug (10,11). The p38 MAPK/cAMP response element-binding protein (CREB) pathway contributes to HMDB-induced CEBPD activation (12). Increased CEBPD participates in the transcription of peroxisome proliferator-activated nuclear receptor g 2 (PPARG2), an adipogenic and proapoptotic inducer, and DNA-damage-inducible protein 153 (GADD153, also known as CHOP), a proapoptotic inducer (13,14).…”

HER-2/neu Mediates Oncogenic Transformation via Altered CREB Expression and Function

“…The human HER-2/ neu þ mammary carcinoma cell line MCF-7 was purchased from the ATCC. The cell lines were routinely maintained in Eagle's modified essential medium (EMEM; Lonza) supplemented with 10% (v/v) heat-inactivated FBS, 2 mmol/L L-glutamine, 100 U/mL penicillin, and 100 mg/mL streptomycin (all supplements obtained from PAA) at 37 C in 5% (v/v) CO 2 humidified air.…”