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

Hepatocellular carcinoma (HCC) can arise from chronic inflammation due to viral infection, organ damage, drug toxicity, or alcohol abuse. Moreover, gene desensitization via aberrant CpG island methylation is a frequent epigenetic defect in HCC. However, the details of how inflammation is linked with epigenetic-mediated desensitization of tumor suppressor genes remains less investigated. In this study, we found that loss of CEBPD enhances the growth of liver cancer cells and is associated with the occurrence of liver cancers, as determined by the assessment of clinical specimens and in vivo animal models. Moreover, E2F1-regulated epigenetic axis attenuated CEBPD expression in liver cancer cells. CEBPD is responsive to the hydroxymethyldibenzoylmethane (HMDB)-induced p38/CREB pathway and plays an important role in the HMDB-induced apoptosis of cancer cells. Regarding depression of epigenetic effects to enhance HMDB-induced CEBPD expression, the combination of HMDB and 5-Aza-2'-deoxycytidine (5-AzadC) could enhance the death of liver cancer cells and reduce the tumor formation of Huh7 xenograft mice. In conclusion, these results suggest that CEBPD could be a useful diagnostic marker and therapeutic target in HCC. The results also reveal the therapeutic potential for low-dose 5-AzadC to enhance the HMDB-induced death of HCC cells.

CEBPD reverses RB/E2F1-mediated gene repression and participates in HMDB-induced apoptosis of cancer cells.

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.