SK-7041, a new histone deacetylase inhibitor, induces G2-M cell cycle arrest and apoptosis in pancreatic cancer cell lines

Anticancer Study of a Novel Pan-HDAC Inhibitor MPT0G236 in Colorectal Cancer Cells

Colorectal cancer (CRC) is one of the most commonly diagnosed malignancies and a leading cause of cancer worldwide. Histone deacetylases (HDACs), which regulate cell proliferation and survival, are associated with the development and progression of cancer. Moreover, HDAC inhibitors are promising therapeutic targets, with five HDAC inhibitors approved for cancer treatment to date. However, their safety profile necessitates the exploration of well-tolerated HDAC inhibitors that can be used in cancer therapeutic strategies. In this study, the pan-HDAC inhibitor MPT0G236 reduced the viability and inhibited the proliferation of human colorectal cancer cells, and normal human umbilical vein endothelial cells (HUVECs) showed reduced sensitivity. These findings indicated that MPT0G236 specifically targeted malignant tumor cells. Notably, MPT0G236 significantly inhibited the activities of HDAC1, HDAC2, and HDAC3, Class I HDACs, as well as HDAC6, a Class IIb HDAC, at low nanomolar concentrations. Additionally, it promoted the accumulation of acetyl-α-tubulin and acetyl-histone H3 in HCT-116 and HT-29 cells in a concentration-dependent manner. Furthermore, MPT0G236 treatment induced G2/M cell cycle arrest in CRC cells by initially regulating the levels of cell-cycle-related proteins, such as p-MPM2; specifically reducing p-cdc2 (Y15), cyclin B1, and cdc25C levels; and subsequently inducing apoptosis through the caspase-dependent pathways and PARP activation. Our findings demonstrate that MPT0G236 exhibits significant anticancer activity in human colorectal cancer cells.

Epigenetic drugs as new emerging therapeutics: What is the scale's orientation of application and challenges?

Epigenetics is the study of heritable changes in gene expression or function without altering the DNA sequence. Important factors are part of epigenetic events, such as methylation, DNA histone rearrangements, nucleosome transposition, and non-coding RNAs. Dysregulated epigenetic mechanics are associated with various cancers' initiation, development, and metastasis. It is known that the occurrence and development of cancer can be controlled by regulating unexpected epigenetic events. Epi-drugs are used singly or in combination with chemotherapy and enhance antitumor activity, reduce drug resistance, and stimulate the host immune response. Despite these benefits, epigenetic therapy as a single therapy or in combination with other drugs leads to adverse effects. This review article introduces and compares the advantages, disadvantages, and side effects of using these drugs for the first time since their introduction. Also, this article describes the mechanism of action of various epigenetic drugs. Recommendations for future use of epigenetic drugs as cancer therapeutics are suggested as an overall conclusion.

MiR-373-3p enhances the chemosensitivity of gemcitabine through cell cycle pathway by targeting CCND2 in pancreatic carcinoma cells

OBJECTIVE

This study aimed to detect the expression of miR-373-3p and CCND2 in gemcitabine-resistance pancreatic carcinoma (PC) cells, investigate the relationship between miR-373-3p and CCND2, and explore their effects on PC propagation, migration, invasion and apoptosis.

METHODS

R software was applied for analyzing differentially expressed genes (DEGs) in cell samples. The potential biological pathway was determined by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, based on R software. The gemcitabine-resistance PC cells were screened out using MTT assay, and they were applied in the next experiments. MiR-373-3p and CCND2 expression in GEM-PANC-1 cells were measured by qRT-PCR. After transfection, the expression of CCND2 protein was examined via western blot assay. Cells viability and apoptosis were confirmed by MTT proliferation assay and Flow cytometry, whereas cells migration and invasion were analyzed by transwell assay. The targeting relationship between miR-373-3p and CCND2 was identified by dual-luciferase reporter assay.

RESULTS

MiR-373-3p was found to be low expressed in GEM-PANC-1 cells while CCND2 was highly expressed in GEM-PANC-1 cells. MiR-373-3p negatively regulated CCND2 expression through KEGG_Cell_Cycle_Signaling_Pathway. The targeted relationship between miR-373-3p and CCND2 could be verified using dual luciferase reporter assay. MTT proliferation assay, transwell assay and Annexin V assay demonstrated that miR-373-3p suppressed GEM-PANC-1 cells propagation and invasion and promoted cell apoptosis, while CCND2 showed totally reverse effects compared with miR-373-3p. All the results suggested that miR-373-3p could enhance the chemosensitivity of GEM-PANC-1 cells by regulating CCND2.

CONCLUSION

MiR-373-3p inhibited cell propagation, migration and invasion and boosted apoptosis in gemcitabine resistance pancreatic carcinoma cells by targeting CCND2.

HDAC Inhibitor-Induced Mitotic Arrest Is Mediated by Eg5/KIF11 Acetylation

Histone deacetylase 1 (HDAC1) is an epigenetic enzyme that regulates key cellular processes, such as cell proliferation, apoptosis, and cell survival, by deacetylating histone substrates. Aberrant expression of HDAC1 is implicated in multiple diseases, including cancer. As a consequence, HDAC inhibitors have emerged as effective anti-cancer drugs. HDAC inhibitor-induced G₀/G₁ cell-cycle arrest has been attributed to epigenetic transcriptional changes mediated by histone acetylation. However, the mechanism of G₂/M arrest remains poorly understood. Here, we identified mitosis-related protein Eg5 (KIF11) as an HDAC1 substrate using a trapping mutant strategy. HDAC1 colocalized with Eg5 during mitosis and influenced the ATPase activity of Eg5. Importantly, an HDAC1- and HDAC2-selective inhibitor caused mitotic arrest and monopolar spindle formation, consistent with a model in which Eg5 deacetylation by HDAC1 is critical for mitotic progression. These findings revealed a previously unknown mechanism of action of HDAC inhibitors involving Eg5 acetylation, and provide a compelling mechanistic hypothesis for HDAC inhibitor-mediated G₂/M arrest.

Panobinostat as Pan-deacetylase Inhibitor for the Treatment of Pancreatic Cancer: Recent Progress and Future Prospects

The histone deacetylase (HDAC) inhibitors have been demonstrated as an emerging class of anticancer drugs. HDACs are involved in regulation of gene expression and in chromatin remodeling, thus indicating valid targets for different types of cancer therapeutics. The pan-deacetylase inhibitor panobinostat (Farydac^®, LBH589) was developed by Novartis Pharmaceuticals and has been recently approved by the US Food and Drug Administraion (FDA) as a drug to treat multiple myeloma. It is under clinical investigation for a range of haematological and solid tumors worldwide in both oral and intravenous formulations. Panobinostat inhibits tumor cell growth by interacting with acetylation of histones and non-histone proteins as well as various apoptotic, autophagy-mediated targets and various tumorogenesis pathways involved in development of tumors. The optimal combination regimen for pancreatic cancer remains to be fully elucidated with various combination regimens, and should be investigated in clinical trials. This article summarizes the current preclinical and clinical status of panobinostat in pancreatic cancer. Preclinical data suggests that panobinostat has potential inhibitory activity in pancreatic cancer cells by targeting various pathways and factors involved in the development of cancer. Herein, we reviewed the status of mono and combination therapy and the rationale behind the combination therapy undergoing trials, as well as possible future prospective use in the treatment of pancreatic cancer.

Selective inhibition of esophageal cancer cells by combination of HDAC inhibitors and Azacytidine

Esophageal cancers are highly aggressive tumors with poor prognosis despite some recent advances in surgical and radiochemotherapy treatment options. This study addressed the feasibility of drugs targeting epigenetic modifiers in esophageal squamous cell carcinoma (ESCC) and esophageal adenocarcinoma (EAC) cells. We tested inhibition of histone deacetylases (HDACs) by SAHA, MS-275, and FK228, inhibition of DNA methyltransferases by Azacytidine (AZA) and Decitabine (DAC), and the effect of combination treatment using both types of drugs. The drug targets, HDAC1/2/3 and DNMT1, were expressed in normal esophageal epithelium and tumor cells of ESCC or EAC tissue specimens, as well as in non-neoplastic esophageal epithelial (Het-1A), ESCC (OE21, Kyse-270, Kyse-410), and EAC (OE33, SK-GT-4) cell lines. In vitro, HDAC activity, histone acetylation, and p21 expression were similarly affected in non-neoplastic, ESCC, and EAC cell lines post inhibitor treatment. Combined MS-275/AZA treatment, however, selectively targeted esophageal cancer cell lines by inducing DNA damage, cell viability loss, and apoptosis, and by decreasing cell migration. Non-neoplastic Het-1A cells were protected against HDACi (MS-275)/AZA treatment. RNA transcriptome analyses post MS-275 and/or AZA treatment identified novel regulated candidate genes (up: BCL6, Hes2; down: FAIM, MLKL), which were specifically associated with the treatment responses of esophageal cancer cells. In summary, combined HDACi/AZA treatment is efficient and selective for the targeting of esophageal cancer cells, despite similar target expression of normal and esophageal cancer epithelium, in vitro and in human esophageal carcinomas. The precise mechanisms of action of treatment responses involve novel candidate genes regulated by HDACi/AZA in esophageal cancer cells. Together, targeting of epigenetic modifiers in esophageal cancers may represent a potential future therapeutic approach.

Lead Induces Apoptosis and Histone Hyperacetylation in Rat Cardiovascular Tissues

Acute and chronic lead (Pb) exposure might cause hypertension and cardiovascular diseases. The purpose of this study was to evaluate the effects of early acute exposure to Pb on the cellular morphology, apoptosis, and proliferation in rats and to elucidate the early mechanisms involved in the development of Pb-induced hypertension. Very young Sprague-Dawley rats were allowed to drink 1% Pb acetate for 12 and 40 days. Western blot analysis indicated that the expression of proliferating cell nuclear antigen (PCNA) decreased in the tissues of the abdominal and thoracic aortas and increased in the cardiac tissue after 12 and 40 days of Pb exposure, respectively. Bax was upregulated and Bcl-2 was downregulated in vascular and cardiac tissues after 40 days of Pb exposure. In addition, an increase in caspase-3 activity was observed after 40 days of exposure to Pb. In terms of morphology, we found that the internal elastic lamina (IEL) of aorta lost the original curve and the diameter of cardiac cell was enlarged after 40 days. Furthermore, the exposure led to a marked increase in acetylated histone H3 levels in the aortas and cardiac tissue after 12 and 40 days, than that in the control group. These findings indicate that Pb might increase the level of histone acetylation and induce apoptosis in vascular and cardiac tissues. However, the mechanism involved need to be further investigated.

Therapeutic potential of histone deacetylase inhibitors in pancreatic cancer

Pancreatic cancer is a devastating disease with a dismal prognosis. Surgical resection is the only curative option but is heavily hampered by delayed diagnosis. Due to few therapeutic treatments available, novel and efficacious therapy is urgently needed. Histone deacetylase inhibitors (HDACIs) are emerging as a prominent class of therapeutic agents for pancreatic cancer and have exhibited significant anticancer potential with negligible toxicity in preclinical studies. Clinical evaluations of HDACIs are currently underway. HDACIs as monotherapy in solid tumors have proven less effective than hematological malignancies, the combination of HDACIs with other anticancer agents have been assessed for advanced pancreatic cancer. In this review, we describe the molecular mechanism underpin the anticancer effect of HDACIs in pancreatic cancer and summarize the recent advances in the rationale for the combination strategies incorporating HDACIs. In addition, we discuss the importance of identifying predictors of response to HDACI-based therapy.

Development of histone deacetylase inhibitors for cancer treatment

Histone deacetylase (HDAC) inhibitors are an exciting new addition to the arsenal of cancer therapeutics. The inhibition of HDAC enzymes by HDAC inhibitors shifts the balance between the deacetylation activity of HDAC enzymes and the acetylation activity of histone acetyltransferases, resulting in hyperacetylation of core histones. Exposure of cancer cells to HDAC inhibitors has been associated with a multitude of molecular and biological effects, ranging from transcriptional control, chromatin plasticity, protein-DNA interaction to cellular differentiation, growth arrest and apoptosis. In addition to the antitumor effects seen with HDAC inhibitors alone, these compounds may also potentiate cytotoxic agents or synergize with other targeted anticancer agents. The exact mechanism by which HDAC inhibitors cause cell death is still unclear and the specific roles of individual HDAC enzymes as therapeutic targets has not been established. However, emerging evidence suggests that the effects of HDAC inhibitors on tumor cells may not only depend on the specificity and selectivity of the HDAC inhibitor, but also on the expression patterns of HDAC enzymes in the tumor tissue. In this review, the recent advances in the understanding and clinical development of HDAC inhibitors, as well as their current role in cancer therapy, will be discussed.

The in vitro apoptotic effects of A248 and A1659, newly synthetic histone deacetylase inhibitors in oral cancer cells

OBJECTIVES

Histone deacetylase (HDAC) inhibitors represent potential therapeutic agents against various cancers. In this study, we attempt to identify whether newly synthesized HDAC inhibitors, A248 and A1659, can be effective anti-cancer drug candidates for oral cancer.

MATERIALS AND METHODS

The anti-cancer activities of A248 and A1659 in MC-3 and HN22 human oral cancer cells were evaluated by 3-(4,5-dimethylthiazol-20yl)-(3-carboxymethoxyphenyl)-2-(4-sulphophenyl)-2H-tetrazolium (MTS) assay, 4'-6-diamidino-2-phenylindole (DAPI) staining, Western blot analysis, immunocytochemistry, and small interference RNA (siRNA) technology.

RESULTS

A248 and A1659 enhanced histone acetylation and decreased the viability of MC-3 and HN22 cells. A248 and A1659 also induced apoptosis, as evidenced by altered nuclear features and poly(ADP-ribose)polymerase (PARP) cleavage. A248 and A1659 markedly decreased Sp1 expression in a concentration- or time-dependent manner and blocked nuclear translocation of Sp1 protein from the cytosol, which contributed to an increase in p27 expression and a decrease in cyclin D1 expression. Furthermore, the knockdown of Sp1 protein with siRNA caused marked alteration of p27 and cyclin D1 expression to induce apoptosis. The most popular HDAC inhibitor, trichostatin A (TSA) also induced apoptosis and reduced the expression level of Sp1 protein.

CONCLUSION

These results suggest that A248 and A1659, two new HDAC inhibitors, may be attractive therapeutic drug candidates for targeting Sp1 in human oral cancer cells.

Current evidence for histone deacetylase inhibitors in pancreatic cancer

Pancreatic cancer is one of the most aggressive human cancers, with more than 200 000 deaths worldwide every year. Despite recent efforts, conventional treatment approaches, such as surgery and classic chemotherapy, have only slightly improved patient outcomes. More effective and well-tolerated therapies are required to reverse the current poor prognosis of this type of neoplasm. Among new agents, histone deacetylase inhibitors (HDACIs) are now being tested. HDACIs have multiple biological effects related to acetylation of histones and many non-histone proteins that are involved in regulation of gene expression, apoptosis, cell cycle progression and angiogenesis. HDACIs induce cell cycle arrest and can activate the extrinsic and intrinsic pathways of apoptosis in different cancer cell lines. In the present review, the main mechanisms by which HDACIs act in pancreatic cancer cells in vitro, as well as their antiproliferative effects in animal models are presented. HDACIs constitute a promising treatment for pancreatic cancer with encouraging anti-tumor effects, at well-tolerated doses.

Histone-deacetylase inhibitors produce positive results in the GADD45a-GFP GreenScreen HC assay

Histone-deacetylase inhibitors (HDACi) are able to induce cell-cycle arrest, apoptosis and differentiation in a variety of tumour cell lines. The mechanisms leading to these cellular outcomes are not fully understood, however, it is has been proposed that induction of cell-cycle arrest might be a result of genotoxic stress. Despite the potential for genotoxic activity of this class of compounds, there are very few data available to provide evidence for this, either in vitro or in vivo. In this study, four HDACi, viz. trichostatin A, sodium butyrate, APHA compound 8 and apicidin, were tested in the human lymphoblastoid TK6 cell line-hosted GADD45a-GFP assay, which has high sensitivity and specificity in the detection of genotoxic carcinogens and in vivo genotoxicants. All four compounds produced positive genotoxicity results within the acceptable toxic dose range of the assay, with APHA compound 8 producing the weakest response. Taken alongside recent evidence demonstrating that GADD45a is not induced by non-genotoxic apoptogens, this study suggests that genotoxicity contributes to the anti-tumour activity of HDACi drugs.

Overcoming nucleoside analog chemoresistance of pancreatic cancer: a therapeutic challenge

Clinical refractoriness to nucleoside analogs (e.g., gemcitabine, capecitabine) is a major scientific problem and is one of the main reasons underlying the extremely poor prognostic state of pancreatic cancer. The drugs' effects are suboptimal partly due to cellular mechanisms limiting their transport, activation, and overall efficacy. Nonetheless, novel therapeutic approaches are presently under study to circumvent nucleoside analog resistance in pancreatic cancer. With these new approaches come additional challenges to be addressed. This review describes the determinants of chemoresistance in the gemcitabine cytotoxicity pathways, provides an overview of investigational approaches for overcoming chemoresistance, and discusses new challenges presented. Understanding the future directions of the field may assist in the successful development of novel treatment strategies for enhancing chemotherapeutic efficacy in pancreatic cancer.

Developing histone deacetylase inhibitors in the therapeutic armamentarium of pancreatic adenocarcinoma

INTRODUCTION

Histone deacetylases (HDACs) are commonly dysregulated in pancreatic adenocarcinoma (PA) and have a central role in the development and progression of the disease. HDAC is a family of enzymes involved in deacetylation of lysine residues on histone and non-histone proteins. Deacetylation of histone proteins leads to compaction of the DNA/histone complex resulting in inhibition of gene expression. Deacetylation of non-histone proteins can affect the stability and function of key proteins leading to dysregulation of cellular signaling pathways. HDAC inhibitors have been shown to potentiate the antiproliferative and proapoptotic effects of several cytotoxic agents, in vitro and in vivo PA xenograft models.

AREAS COVERED

The areas covered include the biology and function of the HDAC isoenzymes and their significant role in multiple oncogenic pathways in PA. Preclinical and clinical trials evaluating HDAC inhibitors are also reviewed.

EXPERT OPINION

Despite discouraging early phase clinical trials evaluating HDAC inhibitors in PA, this strategy deserves further evaluation guided by better preclinical studies in identifying the role of specific HDAC isoenzyme inhibitors in PA. Evaluation of the effects of HDAC inhibitors on PA stem cell function and epithelial to mesenchymal transformation is also an evolving area that holds future potential for these agents. Such preclinical studies will yield insight into the functionality of HDAC isoenzymes, which can then be translated into rationally designed clinical trials. One such strategy could focus on HDAC inhibition employed in combination with proteasome inhibition targeting the aggresome pathway in PA.

Effects and mechanisms of the combination of suberoylanilide hydroxamic acid and bortezomib on the anticancer property of gemcitabine in pancreatic cancer

OBJECTIVES

Earlier studies that dealt with the combination therapy of gemcitabine and histone deacetylation inhibitors for pancreatic cancer revealed unsatisfactory results. The activation of nuclear factor κB (NF-κB) was referred as one of the attributable causes, and we attempted to overcome this resistance by the addition of a proteasome inhibitor.

METHODS

The influences of suberoylanilide hydroxamic acid (vorinostat, SAHA), a histone deacetylase inhibitor, and bortezomib, a novel selective antagonist of 26S proteasome, with or without gemcitabine on cell growth and apoptosis and the expressions of related proteins were observed in pancreatic cancer cell lines (MiaPaCa-2 and ASPC-1). The xenograft model of pancreatic cancer was used to notice effects in vivo.

RESULTS

Vorinostat and bortezomib had independent inhibitory effects and potentiated the antitumor property of gemcitabine in vitro. In the xenograft model, more augmented effects were achieved when bortezomib was combined with gemcitabine than gemcitabine alone. The down-regulation of pAkt and suppression of NF-κB activity was induced by the triple combination.

CONCLUSIONS

The triple combination of vorinostat, bortezomib, and gemcitabine resulted in the strongest antitumor effects both in vitro and in vivo and pAkt and NF-κB seems to be involved in this process.

Histone deacetylase 1 is required for exocrine pancreatic epithelial proliferation in development and cancer

Histone deacetylases (HDACs) play important roles in the epigenetic control of development, and aberrant expression of HDACs has been implicated in human diseases including cancer. Among the mammalian HDACs, HDAC1 has been extensively studied, but its role in exocrine pancreatic morphogenesis and cancer is still poorly understood. The goal of this study is to determine the functional role of HDAC1 in normal development of exocrine pancreas using zebrafish as the model organism as well as in human pancreatic adenocarcinoma. The zebrafish germline loss-of-function mutation hdac1(hi1618) caused impaired cell cycle progression in pancreatic epithelia, resulting in growth arrest and dysmorphogenesis of exocrine pancreas. In human pancreatic adenocarcinoma tissues and cell lines, HDAC1 was expressed at variably elevated levels. RNA interference-induced silencing of HDAC1 diminished proliferation of the cancer cells and cell cycle progression. The proliferative arrest in the developing exocrine pancreas and pancreatic cancer cells was associated with up-regulated expression of the cyclin-dependent kinase inhibitors and the sonic hedgehog signaling components. This study indicates that HDAC1 is required for pancreatic epithelial proliferation in development and cancer. We hypothesize that aberrant expression of HDAC1 modulates the developmental and signaling pathways in exocrine pancreatic epithelia and consequently the genes required for cellular proliferation during development and progression of pancreatic neoplasia.

The molecular targets for the diagnosis and treatment of pancreatic cancer

Pancreatic cancer is considered an aggressive malignancy that responds poorly to current treatments and therefore has a dismal survival rate. This disease is usually not diagnosed until a late stage, at which point palliative chemotherapy with the purine analogue gemcitabine and/or a fluoropyrimidine or a platinum agent is the standard approach. There are some new data on the molecular and genetic changes that take place in pancreatic cancer, which may facilitate the accuracy of diagnosis and efficacy of treatments. However, translational efforts in clinical practice have increased clinicians' options with a targeted agent, erlotinib, in combination with the standard gemcitabine chemotherapy. Many other novel drugs currently being tested in the field of pharmaco-oncology target various altered biological pathways and molecules. Nevertheless, the lack of clinically significant improvements in treatments is rendering efforts to develop methods of early diagnosis both more urgent and promising. The aim of this review was to summarize the molecular basis of pancreatic carcinogenesis and the latest developments in diagnosis by molecular means, focusing on the results of clinical research into targeted and personalized treatments.

Targeting histone deacetylases in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a dismal disease with a median survival below 6 months and a 5-year survival rate below 1%. Effective therapies for locally advanced or metastatic tumours are missing and curatively resected patients relapse in over 80% of the cases. Although histone deacetylases (HDACs) are involved in the control of proliferation, apoptosis, differentiation, migration and angiogenesis of cancer cells, knowledge about the expression patterns and functions of individual HDAC isoenzymes in pancreatic cancer is sparse. This review summarizes the roles of HDACs as novel therapeutic targets and the molecular mode of action of HDAC-inhibitors (HDACI) in PDACs. Success of HDACI in clinical settings will depend on an increased knowledge of HDAC functions as well as on a better understanding of the mode of action of HDACI. Pre-clinical experimental data that constitute the basis for rational therapeutic strategies to treat PDAC are described here. Translating these rational-based therapies into the clinic will finally increase our chance to establish an effective HDACI-containing combination therapy effective against PDAC.

Pancreatic cancer: from molecular pathogenesis to targeted therapy

Pancreatic cancer is a deadly malignancy with still high mortality and poor survival despite the significant advances in understanding, diagnosis, and access to conventional and novel treatments. Though cytotoxic chemotherapy based on the purine analogue gemcitabine remains the standard approach in adjuvant and palliative setting the need for novel agents aiming at the main pathophysiological abnormalities and molecular pathways involved remains soaring. So far, evidence of clinical benefit, though small, exists only from the addition of the targeted agent erlotinib on the standard gemcitabine chemotherapy. Apart from the popular monoclonal antibodies and small molecules tyrosine kinase inhibitors, other novel compounds being tested in preclinical and clinical studies target mTOR, NF-kappaB, proteasome and histone deacetylase. These new drugs along with gene therapy and immunotherapy, which are also under clinical evaluation, may alter the unfavorable natural course of this disease. In this review we present the main pathophysiological alterations met in pancreatic cancer and the results of the florid preclinical and clinical research with regards to the targeted therapy associated to these abnormalities.

Effect of histone deacetylase inhibitor on proliferation of biliary tract cancer cell lines

AIM: To explore the effect of histone deacetylase inhibitor, trichostatin A (TSA) on the growth of biliary tract cancer cell lines (gallbladder carcinoma cell line and cholangiocarcinoma cell line) in vivo and in vitro, and to investigate the perspective of histone deacetylase inhibitor in its clinical application.

METHODS: The survival rates of gallbladder carcinoma cell line (Mz-ChA-l cell line) and cholangiocarcinoma cell lines (QBC939, KMBC and OZ cell lines) treated with various doses of TSA were detected by methylthiazol tetrazolium (MTT) assay. A nude mouse model of transplanted gallbladder carcinoma (Mz-ChA-l cell line) was successfully established, and changes in the growth of transplanted tumor after treated with TSA were measured.

RESULTS: TSA could inhibit the proliferation of gallbladder carcinoma cell line (Mz-ChA-l cell line) and cholangiocarcinoma cell lines (QBC939, KMBC and OZ cell lines) in a dose-dependent manner. After the nude mouse model of transplanted gallbladder carcinoma (Mz-ChA-l cell line) was successfully established, the growth of cancer was inhibited in the model after treated with TSA.

CONCLUSION: TSA can inhibit the growth of cholangiocarcinoma and gallbladder carcinoma cell lines in vitro and in vivo.

Histone deacetylase inhibitor MS-275 alone or combined with bortezomib or sorafenib exhibits strong antiproliferative action in human cholangiocarcinoma cells

AIM: To investigate the antiproliferative effect of the histone deacetylase (HDAC) inhibitor MS-275 on cholangiocarcinoma cells alone and in combination with conventional cytostatic drugs (gemcitabine or doxorubicin) or the novel anticancer agents sorafenib or bortezomib.

METHODS: Two human bile duct adenocarcinoma cell lines (EGI-1 and TFK-1) were studied. Crystal violet staining was used for detection of cell number changes. Cytotoxicity was determined by measuring the release of the cytoplasmic enzyme lactate dehydrogenase (LDH). Apoptosis was determined by measuring the enzyme activity of caspase-3. Cell cycle status reflected by the DNA content was detected by flow cytometry.

RESULTS: MS-275 treatment potently inhibited the proliferation of EGI-1 and TFK-1 cholangiocarcinoma cells by inducing apoptosis and cell cycle arrest. MS-275-induced apoptosis was characterized by activation of caspase-3, up-regulation of Bax and down-regulation of Bcl-2. Cell cycle was predominantly arrested at the G₁/S checkpoint, which was associated with induction of the cyclin-dependent kinase inhibitor p21^Waf/CIP1. Furthermore, additive anti-neoplastic effects were observed when MS-275 treatment was combined with gemcitabine or doxorubicin, while combination with the multi-kinase inhibitor sorafenib or the proteasome inhibitor bortezomib resulted in overadditive anti-neoplastic effects.

CONCLUSION: The growth of human cholangiocarcinoma cells can be potently inhibited by MS-275 alone or in combination with conventional cytostatic drugs or new, targeted anticancer agents.