Quantitative research of histone H3 acetylation levels of human hepatocellular carcinoma cells

Deciphering the potential role of post-translational modifications of histones in gastrointestinal cancers: a proteomics-based review with therapeutic challenges and opportunities

Oncogenesis is a complex and multi-step process, controlled by several factors including epigenetic modifications. It is considered that histone modifications are critical components in the regulation of gene expression, protein functions, and molecular interactions. Dysregulated post-translationally modified histones and the related enzymatic systems are key players in the control of cell proliferation and differentiation, which are associated with the onset and progression of cancers. The most of traditional investigations on cancer have focused on mutations of oncogenes and tumor suppressor genes. However, increasing evidence indicates that epigenetics, especially histone post-translational modifications (PTMs) play important roles in various cancer types. Mass spectrometry-based proteomic approaches have demonstrated tremendous potential in PTMs profiling and quantitation in different biological systems. In this paper, we have made a proteomics-based review on the role of histone modifications involved in gastrointestinal cancers (GCs) tumorigenesis processes. These alterations function not only as diagnostic or prognostic biomarkers for GCs, but a deeper comprehension of the epigenetic regulation of GCs could facilitate the treatment of this prevalent malignancy through the creation of more effective targeted therapies.

Advances in targeting histone deacetylase for treatment of solid tumors

Histone deacetylase (HDAC) serves as a critical molecular regulator in the pathobiology of various malignancies and have garnered attention as a viable target for therapeutic intervention. A variety of HDAC inhibitors (HDACis) have been developed to target HDACs. Many preclinical studies have conclusively demonstrated the antitumor effects of HDACis, whether used as monotherapy or in combination treatments. On this basis, researchers have conducted various clinical studies to evaluate the potential of selective and pan-HDACis in clinical settings. In our work, we extensively summarized and organized current clinical trials, providing a comprehensive overview of the current clinical advancements in targeting HDAC therapy. Furthermore, we engaged in discussions about several clinical trials that did not yield positive outcomes, analyzing the factors that led to their lack of anticipated therapeutic effectiveness. Apart from the experimental design factors, issues such as toxicological side effects, tumor heterogeneity, and unexpected off-target effects also contributed to these less-than-expected results. These challenges have naturally become significant barriers to the application of HDACis. Despite these challenges, we believe that advancements in HDACi research and improvements in combination therapies will pave the way or lead to a broad and hopeful future in the treatment of solid tumors.

Potential Biomarkers for Liver Cancer Diagnosis Based on Multi-Omics Strategy

Liver cancer is the fourth leading cause of cancer-related death worldwide. Hepatocellular carcinoma (HCC) accounts for about 85%-90% of all primary liver malignancies. However, only 20-30% of HCC patients are eligible for curative therapy mainly due to the lack of early-detection strategies, highlighting the significance of reliable and accurate biomarkers. The integration of multi-omics became an important tool for biomarker screening and unique alterations in tumor-associated genes, transcripts, proteins, post-translational modifications and metabolites have been observed. We here summarized the novel biomarkers for HCC diagnosis based on multi-omics technology as well as the clinical significance of these potential biomarkers in the early detection of HCC.

Ras-ERK1/2 signaling contributes to the development of colorectal cancer via regulating H3K9ac

BACKGROUNDS/AIMS

Ras is a control switch of ERK1/2 pathway, and hyperactivation of Ras-ERK1/2 signaling appears frequently in human cancers. However, the molecular regulation following by Ras-ERK1/2 activation is still unclear. This work aimed to reveal whether Ras-ERK1/2 promoted the development of colorectal cancer via regulating H3K9ac.

METHODS

A vector for expression of K-Ras mutated at G12 V and T35S was transfected into SW48 cells, and the acetylation of H3K9 was measured by Western blot analysis. MTT assay, colony formation assay, transwell assay, chromatin immunoprecipitation and RT-qPCR were performed to detect whether H3K9ac was contributed to K-Ras-mediated cell growth and migration. Furthermore, whether HDAC2 and PCAF involved in modification of H3K9ac following Ras-ERK1/2 activation were studied.

RESULTS

K-Ras mutated at G12 V and T35S induced a significant activation of ERK1/2 signaling and a significant down-regulation of H3K9ac. Recovering H3K9 acetylation by using a mimicked H3K9ac expression vector attenuated the promoting effects of Ras-ERK1/2 on tumor cells growth and migration. Besides, H3K9ac can be deacetylated by HDAC2 and MDM2-depedent degradation of PCAF.

CONCLUSION

H3K9ac was a specific target for Ras-ERK1/2 signaling pathway. H3K9 acetylation can be modulated by HDAC2 and MDM2-depedent degradation of PCAF. The revealed regulation provides a better understanding of Ras-ERK1/2 signaling in tumorigenesis.

1,25(OH)2D3 inhibits the progression of hepatocellular carcinoma via downregulating HDAC2 and upregulating P21(WAFI/CIP1)

Vitamin D, termed 1,25(OH)2D3 in it's active form, activity is associated with a reduced risk of hepatocellular carcinoma (HCC) and is an important immune regulator. However, the detail molecular mechanisms underlying the effects of 1,25(OH)2D3 on the progression of HCC are widely unknown. Histone deacetwylase 2 (HDAC2) is usually expressed at high levels in tumors, and its downregulation leads to high expression levels of cell cycle components, including p21(WAF1/Cip1), a well-characterized modulator, which is critical in cell senescence and apoptosis. The present study investigated whether vitamin D inhibits HCC via the regulation of HDAC2 and p21(WAF1/Cip1). Firstly, the toxic concentrations of 1,25(OH)2D3 were determined, according to trypan blue and [(3)H]thymidine incorporation assays. Secondly, HCC cells lines were treated with different concentrations of 1,25(OH)2D3. The expression of HDAC2 was either silenced via short hairpin (sh)RNA or induced by transfection of plasmids expressing the HDAC2 gene in certain HCC cells. Finally the mRNA and protein levels of HDAC2 and p21(WAF1/Cip1) were measured using reverse transcription-quantitative polymerase chain reaction and western blot analyses. The results revealed that 1,25(OH)2D3 treatment reduced the expression of HDAC2 and increased the expression of p21(WAF1/Cip1), in a dose-dependent manner, resulting in the reduction of HCC growth. Elevated levels of HDAC2 reduced the expression of p21(WAF1/Cip1), resulting in an increase in HCC growth. HDAC2 shRNA increased the expression of p21(WAF1/Cip1), resulting in reduction in HCC growth. Thus, 1,25(OH)2D3 exerted antitumorigenic effects through decreasing the expression levels of HDAC2 and increasing the expression of p21(WAF1/Cip1), which inhibited the development of HCC and may indicate the possible underlying mechanism. These results suggest that vitamin D3 may be developed as a potential drug for effective therapy in the treatment of HCC.

High throughput screening identifies modulators of histone deacetylase inhibitors

Background

Previous studies from our laboratory and others have demonstrated that in addition to altering chromatin acetylation and conformation, histone deacetylase inhibitors (HDACi) disrupt the acetylation status of numerous transcription factors and other proteins. A whole genome yeast deletion library screen was used to identify components of the transcriptional apparatus that modulate the sensitivity to the hydroxamic acid-based HDACi, CG-1521.

Results

Screening 4852 haploid Saccharomyces cerevisiae deletion strains for sensitivity to CG-1521 identifies 407 sensitive and 80 resistant strains. Gene ontology (GO) enrichment analysis shows that strains sensitive to CG-1521 are highly enriched in processes regulating chromatin remodeling and transcription as well as other ontologies, including vacuolar acidification and vesicle-mediated transport. CG-1521-resistant strains include those deficient in the regulation of transcription and tRNA modification. Components of the SAGA histone acetyltransferase (HAT) complex are overrepresented in the sensitive strains, including the catalytic subunit, Gcn5. Cell cycle analysis indicates that both the wild-type and gcn5Δ strains show a G₁ delay after CG-1521 treatment, however the gcn5Δ strain displays increased sensitivity to CG-1521-induced cell death compared to the wild-type strain. To test whether the enzymatic activity of Gcn5 is necessary in the response to CG-1521, growth assays with a yeast strain expressing a catalytically inactive variant of the Gcn5 protein were performed and the results show that this strain is less sensitive to CG-1521 than the gcn5Δ strain.

Conclusion

Genome-wide deletion mutant screening identifies biological processes that affect the sensitivity to the HDAC inhibitor CG-1521, including transcription and chromatin remodeling. This study illuminates the pathways involved in the response to CG-1521 in yeast and provides incentives to understand the mechanisms of HDAC inhibitors in cancer cells. The data presented here demonstrate that components of the SAGA complex are involved in mediating the response to CG-1521. Additional experiments suggest that functions other than the acetyltransferase activity of Gcn5 may be sufficient to attenuate the effects of CG-1521 on cell growth.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-528) contains supplementary material, which is available to authorized users.