Treatment of tumor cells with histone deacetylase inhibitors results in altered recruitment of methyl-CpG binding proteins to a methylated CpG island

Histone H3 (lys-9) deacetylation is associated with transcriptional silencing of E-cadherin in colorectal cancer cell lines

Epigenetic parameters linked to E-cadherin gene were investigated in 5 human colorectal cancer cell lines. Treatment with trichostatin A led to enhanced acetylation of histone H3-K9 with concurrent induction of E-cadherin mRNA in 3 E-cadherin low/negative cell lines that are not DNA methylated. Co-treatment with 5-aza-2'-deoxycytidine and trichostatin A resulted in additive/synergic induction of E-cadherin mRNA in all 5 cell lines with concomitant enhancement of histone H3-K9 acetylation in 4 E-cadherin low/negative cell lines. Our results suggest that histone H3-K9 deacetylation appears to play a crucial role in transcriptional repression of E-cadherin in colorectal cancers.

Trichostatin A, a histone deacetylase inhibitor, attenuates invasiveness and reactivates E-cadherin expression in immortalized endometriotic cells

The objective of this study is to determine whether trichostatin A (TSA) can suppress the invasiveness of 2 endometriotic cell lines known to be invasive and E-cadherin negative. The membrane invasion culture system was used to assess cell invasion using invasive and a noninvasive bladder cancer cell lines as positive and negative controls, respectively. The E-cadherin mRNA levels and protein expression were evaluated by real-time reverse transcriptase polymerase chain reaction and Western blot analysis, respectively. The authors found that TSA attenuates the invasiveness of 2 cell lines in the presence or absence of tumor necrosis factor alpha (TNFalpha) stimulation. In addition, TSA treatment reactivates E-cadherin gene and protein expression in these cell lines. These results, along with recent findings that TSA suppresses proliferation, interleukin-1 beta-induced cyclo-oxygenase 2 expression, and constitutive or TNFalpha-stimulated nuclear factor kappa B activation in endometrial and endometriotic cells, makes histone deacetylase inhibitors a promising class of compounds for novel and more effective medical treatment of endometriosis, especially given the mounting evidence that endometrios be an epigenetic disease.

Histone deacetylase inhibitors – a new tool to treat cancer

Transcriptional regulation in eukaryotes is a multilevel hierarchical process. It is becoming clear that higher-order chromatin structure, occurring via modifications of histones in their nucleosome structure, plays a crucial role in regulating gene expression, both in normal and pathological states. Deacetylation of histones by histone deacetylases (HDACs) modifies the chromatin from an open gene active euchromatin structure to a closed gene silenced heterochromatin structure. Several cancer promoting mutations and chromosomal translocations result in repression of transcription through abnormal recruitment and activation of HDACs, leading to neoplastic transformation. This is the rationale for the evolvement of HDAC inhibitors as a new class in cancer therapy. Trials have shown anti-proliferation effect of histone deacetylase inhibitors in cell culture, animal models and in human with both hematological and solid tumors. The exact mechanism by which histone deacetylase inhibitors exert their effect is still obscure. Reversal of the alteration in gene expression by fusion transcription factors or overexpressed repressors is just one of several possible explanations. The territory of heterochromatin in the vicinity of the nuclear periphery raised the possibility of involvement of nuclear envelope proteins in the regulation of transcription. Our laboratory is interested in the transcription repression mechanism induced by the nuclear envelope lamina associated polypeptide 2 (LAP2) family of proteins through chromatin modification. Here, we will describe the structure of the nucleosome, review regulation of gene expression by acetylation of histones and give an update on the current phase I and phase II clinical trials with histone deacetylase inhibitors.