• Biomolecules & Therapeutics
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• v.31 no.1
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• pp.73-81
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• 2023

Sirtuins (SIRTs) belong to the nicotinamide adenine dinucleotide (NAD+)-dependent class III histone deacetylase family. They are key regulators of cellular and physiological processes, such as cell survival, senescence, differentiation, DNA damage and stress response, cellular metabolism, and aging. SIRTs also influence carcinogenesis, making them potential targets for anticancer therapeutic strategies. In this study, we investigated the anticancer properties and underlying molecular mechanisms of a novel SIRT1 inhibitor, MHY2251, in human colorectal cancer (CRC) cells. MHY2251 reduced the viability of various human CRC cell lines, especially those with wild-type TP53. MHY2251 inhibited SIRT1 activity and SIRT1/2 protein expression, while promoting p53 acetylation, which is a target of SIRT1 in HCT116 cells. MHY2251 treatment triggered apoptosis in HCT116 cells. It increased the percentage of late apoptotic cells and the sub-G1 fraction (as detected by flow cytometric analysis) and induced DNA fragmentation. In addition, MHY2251 upregulated the expression of FasL and Fas, altered the ratio of Bax/Bcl-2, downregulated the levels of pro-caspase-8, -9, and -3 proteins, and induced subsequent poly(ADP-ribose) polymerase cleavage. The induction of apoptosis by MHY2251 was related to the activation of the caspase cascade, which was significantly attenuated by pre-treatment with Z-VAD-FMK, a pan-caspase inhibitor. Furthermore, MHY2251 stimulated the phosphorylation of c-Jun N-terminal kinase (JNK), and MHY2251-triggered apoptosis was blocked by pre-treatment with SP600125, a JNK inhibitor. This finding indicated the specific involvement of JNK in MHY2251-induced apoptosis. MHY2251 shows considerable potential as a therapeutic agent for targeting human CRC via the inhibition of SIRT1 and activation of JNK/p53 pathway.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.18
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• pp.7849-7855
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• 2014

Purpose: To investigate the effect of deacetylase inhibitory trichostatin A (TSA) on anti HepG2 liver carcinoma cells and explore the underlying mechanisms. Materials and Methods: HepG2 cells exposed to different concentrations of TSA for 24, 48, or 72h were examined for cell growth inhibition using CCK8, changes in cell cycle distribution with flow cytometry, cell apoptosis with annexin V-FTIC/PI double staining, and cell morphology changes under an inverted microscope. Expression of ${\beta}$-catenin, HDAC1, HDAC3, H3K9, CyclinD1 and Bax proteins was tested by Western blotting. Gene expression for ${\beta}$-catenin, HDAC1and HDAC3 was tested by q-PCR. ${\beta}$-catenin and H3K9 proteins were also tested by immunofluorescence. Activity of Renilla luciferase (pTCF/LEF-luc) was assessed using the Luciferase Reporter Assay system reagent. The activity of total HDACs was detected with a HDACs colorimetric kit. Results: Exposure to TSA caused significant dose-and time-dependent inhibition of HepG2 cell proliferation (p<0.05) and resulted in increased cell percentages in G0/G1 and G2/M phases and decrease in the S phase. The apoptotic index in the control group was $6.22{\pm}0.25%$, which increased to $7.17{\pm}0.20%$ and $18.1{\pm}0.42%$ in the treatment group. Exposure to 250 and 500nmol/L TSA also caused cell morphology changes with numerous floating cells. Expression of ${\beta}$-catenin, H3K9and Bax proteins was significantly increased, expression levels of CyclinD1, HDAC1, HDAC3 were decreased. Expression of ${\beta}$-catenin at the genetic level was significantly increased, with no significant difference in HDAC1and HDAC3 genes. In the cytoplasm, expression of ${\beta}$-catenin fluorescence protein was not obvious changed and in the nucleus, small amounts of green fluorescence were observed. H3K9 fluorescence protein were increased. Expression levels of the transcription factor TCF werealso increased in HepG2 cells following induction by TSA, whikle the activity of total HDACs was decreased. Conclusions: TSA inhibits HDAC activity, promotes histone acetylation, and activates Wnt/${\beta}$-catenin signaling to inhibit proliferation of HepG2 cell, arrest cell cycling and induce apoptosis.

• Radiation Oncology Journal
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• v.23 no.2
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• pp.116-122
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• 2005

Purpose: Histone deacetylase inhibitors (HDIs) are emerging as potentially useful components of anticancer therapy and their radiosensitizing effects have become evident. Specific HDAS are now available that preferentially inhibit specific HDAC classes; TSA inhibits Class I and II HDACs, and SK7041 inhibits Class I HDACs. Materials and methods: We tested the differential radiosensitization induced by two different classes of HDIs in HeLa cells. We next tested the hypothesis that p53 expression in cancer cells may influence the susceptibility to HDIs by using pharmacologic modification of the p53 status under an isogenic background. Results: It is interesting that p53 expression in the HeLa cells clearly increased the degree of radio-sensitization by TSA compared to that of the class I specific inhibitor SK7041. This suggests that p53 may, in part, be responsible for the mechanistic role for the greater radiosensitization induced by Class I & II inhibitors compared to that of the class I specific inhibitors. Thus, these studies are useful in distinguishing between events mediated solely by the Class I HDACS versus those events involving the other classes of HDACS as well. Conclusion: The anticancer efficacy of targeting Class I and II HDACS, in conjunction with radiation therapy, may be further enhanced by the restoration of p53 expression.

• Journal of Life Science
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• v.19 no.9
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• pp.1314-1320
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• 2009

Histone deacetylase inhibitor (HDACI) is a new promising candidate as an antineoplastic agent for the treatment of solid and hematologic malignancies. In order to evaluate cell death and to elucidate the related mechanism(s) in NSCLC cells after HDACI, sodium butyrate (SB), a representative HDACI, was used to treat H460 cells for 48 hrs. SB exposure resulted in a significant reduction of cell viability at concentrations below 7.5 mM, and about 50% of cell death occurred at 20 mM. The types of cell death induced by SB were both apoptosis and necrosis, evaluated by Annexin-V staining combined with propidium iodide. SB treatment significantly evoked G2/M cell cycle arrest and subsequently induced cell death with caspase-dependent manner. While ERK protein content was not altered after SB, phosphorylated forms of ERK were markedly reduced. Taken together, SB is significantly able to induce cell death in NSCLC cell line H460, and it is suggested that the reduction of ERK phosphorylation might be closely involved in the cancer cell death mechanism initiated by HDACI.

• Journal of Life Science
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• v.15 no.6 s.73
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• pp.994-1004
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• 2005

The dihydrofolate reductase (dhfr) promoter contains cis-acting element for the transcription factors Spl and E2F. Transcription of dhfr gene shows maximal activity during the Gl/S phase of cell cycle. The member of the Spl transcriptional factor family can act as both negative and positive regulators of gene expression. There was a report that Spl-Rb and E2F4-pl30 complexes cooperate to establish stable repression of dhfr gene expression in CHOC400 cells. Here, we examined the role of HDAC in dhfr, cyclin E, and cyclin A gene regulation using the histone deacetylation inhibitor, trichostatin A (TSA) in U2OS and C33A cells, a Rb-positive human osteosarcoma cell line, and a Rb-negative cervical carcinoma cell line, respectively. When the dhfr promoter constructs were applied in U2OS cells, TSA markedly stimulated over 14-fold of dhfr promoter activity through dhfr-Spl sites by the deletion of an E2F element. In contrast, the deletion of dhfr-Spl binding sites completely abolished promoter stimulation by TSA. The dhfr promoter activity including dhfr-Spl sites increased only 2-fold in C33A cells. Promoter activity containing only dhfr-E2F site did not have much effect by the treatment of TSA in both U2OS and C33A cells. On the other hand, treatment with TSA induced significantly mRNA expression of dhfr and cyclin E, whereas levels of cyclin A decreased in U2OS cells, but had no effect in C33A cells. These results indicate that TSA have contradictory effect, activation of dhfr and cyclin E genes on Gl phase, and down-regulation of cyclin A on G2 phase through transcriptional regulation in U2OS cells.