Histone Deacetylase Inhibitor RGFP109 Overcomes Temozolomide Resistance by Blocking NF-κB-Dependent Transcription in Glioblastoma Cell Lines

Neurochem Res. 2016 Dec;41(12):3192-3205. doi: 10.1007/s11064-016-2043-5. Epub 2016 Sep 8.


Glioblastoma (GBM) is the most frequent and aggressive tumour in the central nervous system. Many studies have demonstrated that upregulation of the NF-κB onco-pathway is accompanied by the acquisition of Temozolomide (TMZ) resistance in GBM cells. Here, we show that RGFP109, a selective histone deacetylase (HDAC1 and HDAC3) inhibitor, overcomes TMZ resistance and downregulates the expression of NF-κB-regulated pro-survival genes in a TMZ-resistant (TR) GBM cell line. RGFP109 did not alter the phosphorylation levels of NF-κB/p65 or inhibitory κBα (IκBα). Immunofluorescence microscopy showed that RGFP109 does not block the nuclear translocation of NF-κB/p65. However, co-immunoprecipitation assays revealed that RGFP109 induces the hyperacetylation of NF-κB/p65 and histones, and blocks interactions between NF-κB/p65 and its coactivators, p300 and p300/CBP-associated factor (PCAF). These results indicate that RGFP109-mediated post-translational nuclear acetylation may be involved in the regulation of NF-κB. Electrophoretic mobility shift assays revealed that RGFP109 reduces NF-κB/p65 binding to κB-DNA and decreased the transcriptional level of κB-mediated genes, suggesting that RGFP109-induced hyperacetylation leads to attenuated transcription of the κB gene. In addition, RGFP109 elevates the expression of inhibitor of growth 4 (ING4), which is typically downregulated in GBM cells. Importantly, we found that RGFP109 enhances ING4 recognition and binding to NF-κB/p65, which may be positively correlated with reduced interactions between NF-κB/p65 and p300/PCAF, thereby effecting transcription of the κB gene. Finally, we show that knockdown of ING4 with plasmids containing pcDNA3.1-ING4 shRNA abolished the effect of RGFP109. Therefore, ING4 may act as a corepressor and facilitate RGFP109-triggered suppression of the NF-κB pathway. Taken together, our data show that RGFP109, an HDAC inhibitor, in combination with TMZ may be a therapeutic candidate for patients with temozolomide-resistant GBM.

Keywords: Histone deacetylase; ING4; NF-κB; RGFP109; Temozolomide.

MeSH terms

  • Acetylation
  • Active Transport, Cell Nucleus
  • Antineoplastic Agents, Alkylating / pharmacology*
  • Apoptosis
  • Benzamides / pharmacology*
  • Cell Cycle Proteins / metabolism
  • Cell Line, Tumor
  • Cell Nucleus / metabolism
  • Central Nervous System Neoplasms
  • Dacarbazine / analogs & derivatives*
  • Dacarbazine / pharmacology
  • Drug Resistance, Neoplasm / drug effects*
  • Drug Synergism
  • Glioblastoma
  • Histone Deacetylase Inhibitors / pharmacology*
  • Homeodomain Proteins / metabolism
  • Humans
  • NF-kappa B / genetics
  • NF-kappa B / metabolism*
  • Signal Transduction
  • Temozolomide
  • Transcription Factor RelA / genetics
  • Transcription Factor RelA / metabolism
  • Transcription, Genetic
  • Transcriptional Activation
  • Tumor Suppressor Proteins / metabolism


  • Antineoplastic Agents, Alkylating
  • Benzamides
  • Cell Cycle Proteins
  • Histone Deacetylase Inhibitors
  • Homeodomain Proteins
  • ING4 protein, human
  • N-(6-(2-aminophenylamino)-6-oxohexyl)-4-methylbenzamide
  • NF-kappa B
  • Transcription Factor RelA
  • Tumor Suppressor Proteins
  • Dacarbazine
  • Temozolomide