Apoptosis induced by the histone deacetylase inhibitor sodium butyrate in human leukemic lymphoblasts

Chromatin remodeling and stem cell theory of relativity

The field of stem cell biology is currently being redefined. Stem cell (hematopoietic and non-hematopoietic) differentiation has been considered hierarchical in nature, but recent data suggest that there is no progenitor/stem cell hierarchy, but rather a reversible continuum. The stem cell (hematopoietic and non-hematopoietic) phenotype, the total differentiation capacity (hematopoietic and non-hematopoietic), gene expression as well as other stem cell functional characteristics (homing, receptor and adhesion molecule expression) vary throughout a cell-cycle transit widely. This seems to be dependent on shifting chromatin and gene expression with cell-cycle transit. The published data on DNA methylation, histone acetylation, and also RNAi, the major regulators of gene expression, conjoins very well and provides an explanation for the major issues of stem cell biology. Those features of stem cells mentioned above can be rather difficult to apprehend when a classical hierarchy biology view is applied, but they become clear and easier to understand once they are correlated with the underlining epigenetic changes. We are entering a new era of stem cell biology the era of "chromatinomics." We are one step closer to the practical use of cellular therapy for degenerative diseases.

Sodium 4-phenylbutyrate induces apoptosis of human lung carcinoma cells through activating JNK pathway

Sodium 4-phenylbutyrate (PB) has been used in the therapy of urea cycle defects for many years. Recently, it has been shown to cause cellular differentiation, growth arrest, and apoptosis in certain malignancies. We have analyzed the effects of PB on human lung carcinoma cells. PB has distinct patterns of effects on different lung carcinoma cells, inducing apoptosis in NCI-H460 and NCI-H1792 cells, causing G1 arrest in A549 and SK-LU-1 cells, but having no effect on a non-transformed bronchial epithelial cell line HBE4-E6/E7. We investigated the role of MAP kinase family members, extracellular signal-regulated kinase (ERK), JNK, and p38 mitogen-activated protein kinase (MAPK), as well as other important cell survival signaling molecules in PB-induced apoptosis. We observed activation of JNK and ERK by PB in the lung cancer cells. JNK was activated only in the two apoptotic cells, whereas ERK was activated in both the apoptotic and the growth-arrested cells, demonstrating a correlation between apoptosis and activation of JNK in response to PB. Both JNK inhibitor and JNK RNA interference (RNAi) inhibited PB-induced apoptosis, whereas MEK inhibitor did not, supporting that apoptosis induced by PB is through activation of JNK. De novo protein synthesis is required for the PB-induced JNK activation and induction of apoptosis. However, the production of known upstream activators of JNK, namely Fas/Fas ligand, tumor necrosis factor (TNF)-alpha, TNF-beta, and TRAIL, are not altered by PB treatment. Therefore, PB activates JNK through an unidentified and cell type-specific mechanism. Understanding of this mechanism is of therapeutic value in treating cancer patients with PB.

Age-dependent response of lymphocytes in the induction of the linker histone variant, H1 degrees and histone H4 acetylation after treatment with the histone deacetylase inhibitor, trichostatin A

In the present study we investigated the age-related response of Phytohemaglutinin (PHA)-activated S phase human lymphocytes isolated from peripheral blood from donors of four different age groups, namely young (25-30 years), mid-aged (40-45 years), senior (60-65 years) and elderly (80-95 years) on the induction of the linker histone variant, H1 degrees and histone H4 acetylation after treatment with the very specific histone deacetylase (HDAC) inhibitor, trichostatin A (TSA). The cell system of peripheral blood lymphocytes is ideal for the study of H1 degrees induction since they do not synthesize this particular linker histone variant. Lymphocytes isolated from peripheral blood were activated with PHA (5 microg/10(6) cells/ml medium) and placed in culture for a duration of 72 h at which time cells are in the S phase. Forty-eight hours after inoculation, TSA (250 ng/10(6) cells/ml medium) was added to the cell cultures for a period of 24 h. Assays were performed 72 h after initiation of cultures. The results showed that the induction of H1 degrees after TSA treatment increased to a statistically significant degree in the elderly age group with respect to both the young and the mid-aged age groups. Moreover histone H4 acetylation was found to increase as a function of increasing donor age. A hyperacetylation pattern was observed even in the youngest age group analyzed. Specifically, the tetra-acetylated (H4.4) H4 form increased to a statistically significant degree with the concomitant decrease in the non-acetylated H4 for (H4.0) as a function of donor age. The other acetylated H4 forms (H4.1, H4.2, and H4.3) remained more or less constant, irrespective of donor age. These results show that the sensitivity of lymphocytes to TSA is enhanced with increasing donor age. Since to date, 11 class I and II HDACs have been isolated that have been found by other investigators to have differential responses to HDAC inhibitors, these findings may indicate that there is also a differential age-related response of certain HDACs or perhaps a senescent-specific HDAC. This line of research warrants further study.

Synergistic induction of apoptosis in breast cancer cells by cotreatment with butyrate and TNF-alpha, TRAIL, or anti-Fas agonist antibody involves enhancement of death receptors' signaling and requires P21waf1

Inhibitors of histone deacetylase (HDAC) are considered as potential anticancer agents. We have previously demonstrated that an inhibitor of HDAC, sodium butyrate (NaB), induces apoptosis of breast cancer cells in a P53-independent and P21(waf1)-dependent manner. In this study, we showed that tumor necrosis factor-alpha (TNF-alpha), TNF-related apoptosis-inducing ligand (TRAIL), and anti-Fas agonist antibody potentiated NaB-induced growth inhibition through synergistic induction of apoptosis in breast cancer cell lines (MCF-7, T47-D, and BT-20). In MCF-7 cells, NaB increased the expression of death receptors; NaB alone or in combination with TNF-alpha, TRAIL, and anti-Fas agonist antibody increased the levels of Bid, tBid, and that of cytosolic cytochrome c. Synergistic induction of apoptosis was strongly inhibited by dominant-negative Fas-associated death domain (FADD) and inhibitors of caspases-8 and -9, indicating that potentiation of apoptosis involved key elements of death receptors' signaling pathways. Moreover, cotreatment of NaB and ligands of death receptors up-regulated the levels of P21(waf1) and that of proliferating cell nuclear antigen (PCNA) associated with P21(waf1). Transient transfections of p21(waf1) antisense or p21(waf1) deficient for its interaction with PCNA abolished synergistic induction of apoptosis. This suggested that potentiation of apoptosis by cotreatments required P21(waf1) and its interaction with PCNA. Since breast tumors contain rarely p21 mutations, our results may open interesting prospects in the fight against breast cancer.

Histone deacetylase inhibitors specifically kill nonproliferating tumour cells

Conventional chemotherapeutic drugs target proliferating cells, relying on often small differences in drug sensitivity of tumour cells compared to normal tissue to deliver a therapeutic benefit. Consequently, they have significant limiting toxicities and greatly reduced efficacy against nonproliferating compared to rapidly proliferating tumour cells. This lack of selectivity and inability to kill nonproliferating cells that exist in tumours with a low mitotic index are major failings of these drugs. A relatively new class of anticancer drugs, the histone deacetylase inhibitors (HDI), are selectively cytotoxic, killing tumour and immortalized cells but normal tissue appears resistant. Treatment of tumour cells with these drugs causes both G1 phase cell cycle arrest correlated with increase p21 expression, and cell death, but even the G1 arrested cells died although the onset of death was delayed. We have extended these observations using cells that were stably arrested by either serum starvation or expression of the cyclin-dependent kinase inhibitor p16(ink4a). We report that histone deacetylase inhibitors have similar cytotoxicity towards both proliferating and arrested tumour and immortalized cells, although the onset of apoptosis is delayed by 24 h in the arrested cells. Both proliferating and arrested normal cells are unaffected by HDI treatment. Thus, the histone deacetylase inhibitors are a class of anticancer drugs that have the desirable features of being tumour-selective cytotoxic drugs that are equally effective in killing proliferating and nonproliferating tumour cells and immortalized cells. These drugs have enormous potential for the treatment of not only rapidly proliferating tumours, but tumours with a low mitotic index.

Development and evaluation of an in vitro model for the analysis of cigarette smoke effects on cultured cells and tissues

INTRODUCTION

Smokers have an increased risk for a variety of diseases. Among the most prominent is atherosclerosis, the leading cause of death in the Western world. Although this conjunction is accepted knowledge, the basic biological mechanisms and the identities of the active tobacco smoke constituents surprisingly are still unknown. One reason for this is the lack of accurate in vitro models.

METHODS

Cell culture experiments, including cell morphology and cell death analyses, high-performance liquid chromatography, and liquid chromatography coupled to mass spectrometry via an electrospray ionization interface allowing collision-induced dissociation analyses, were applied.

RESULTS AND DISCUSSION

In this study, we present and validate an in vitro model that has proven to be useful for standardized studies of cellular and histological effects of cigarette smoke. The system consists of a cigarette smoke sampling device in which water-soluble cigarette smoke constituents pass over from the gas phase into the aqueous phase resulting in nicotine concentrations identical to the in vivo concentrations, suggesting in vivo similar conditions for gas-to-liquid compound exchange.

T-cell lymphoma as a model for the use of histone deacetylase inhibitors in cancer therapy: impact of depsipeptide on molecular markers, therapeutic targets, and mechanisms of resistance

Depsipeptide (FK228) is a novel histone deacetylase inhibitor currently in clinical trials and the first to demonstrate clinical activity in patients. Responses have been observed in patients with T-cell lymphomas, despite prior treatment with multiple chemotherapeutic agents. To better understand the effects of histone deacetylase inhibitors on T-cell lymphoma, the human T-cell lymphoma cell line HUT78 was tested for sensitivity and molecular response to depsipeptide. Treatment with depsipeptide, as well as other histone deacetylase inhibitors, caused induction of histone acetylation, induction of p21 expression, and substantial apoptosis without significant cell cycle arrest. Treatment with the caspase inhibitor z-VAD-fmk significantly inhibited depsipeptide-induced apoptosis, enabling detection of cell cycle arrest. Treatment with depsipeptide increased expression of the interleukin-2 (IL-2) receptor, and combination with the IL-2 toxin conjugate denileukin diftitox resulted in more than additive toxicity. Cells selected for resistance to depsipeptide overexpressed the multidrug resistance pump, P-glycoprotein (Pgp). However, cells selected for resistance to depsipeptide in the presence of a Pgp inhibitor had a Pgp-independent mechanism of resistance. These studies confirm the activity of depsipeptide in a T-cell lymphoma model and suggest a general sensitivity of T-cell lymphoma to histone deacetylase inhibitors, an emerging new class of anticancer agents. (Blood. 2004;103:4636-4643)

Trichostatin A activates the osteopontin gene promoter through AP1 site

In this study, we investigated osteoblastic differentiation by trichostatin A (TSA), a histone deacetylase inhibitor in mouse undifferentiated mesenchymal cell line. TSA increased the osteopontin (OPN) mRNA level and OPN protein. Deletion analysis of the promoter region revealed TSA-induced luciferase response was regulated by -75 to -65 of the OPN promoter. There was an AP1-binding sequence at the site of the OPN promoter. In an electrophoretic mobility shift assay, bands of the complexes were supershifted by addition of antibody to c-fos and phosphorylated c-jun. These data suggested that AP1 plays a crucial role in the TSA-induced OPN expression.

The histone deacetylase inhibitor suberic bishydroxamate regulates the expression of multiple apoptotic mediators and induces mitochondria-dependent apoptosis of melanoma cells

Histone deacetylase (HDAC) inhibitors have attracted much interest because of their ability to arrest cell growth, induce cell differentiation, and in some cases, induce apoptosis of cancer cells. In the present study, we have examined a new HDAC inhibitor, suberic bishydroxamate (SBHA), for its effect on a panel of human melanoma cell lines. We report that it induces varying degrees of apoptosis in the melanoma lines but not in melanocytes and fibroblasts. Induction of apoptosis was caspase dependent and was associated with induction of changes in mitochondrial membrane permeability, which could be inhibited by overexpression of Bcl-2. The changes in mitochondria were independent of caspase activation and were associated with changes in conformation of Bax. SBHA down-regulated several key antiapoptotic proteins including X-linked inhibitor of apoptosis and the Bcl-2 family proteins, Bcl-XL and Mcl-1. In contrast, it induced up-regulation of the Bcl-2 family proapoptotic proteins, Bim, Bax, and Bak. In addition, SBHA induced relocation of the protein Bim to mitochondria and its association with Bcl-2. De novo protein synthesis was required for initiation of apoptosis in that the protein synthesis inhibitor, cycloheximide, inhibited SBHA-induced conformational changes in Bax as well as changes in mitochondrial membrane permeability and activation of caspase-3. These results suggest that SBHA induces apoptosis by changing the balance between proapoptotic and antiapoptotic proteins in melanoma cells. The protein Bim may be a key initiator of apoptosis in cells treated with SBHA.

Disruption of vascular endothelial homeostasis by tobacco smoke: impact on atherosclerosis

The World Health Organization (WHO) predicts that by 2020 tobacco will become the largest single health problem worldwide and will cause an estimated 8.4 million deaths annually (http://www5.who.int/tobacco/). Although the impact of smoking on human health is well defined from the medical point of view, surprisingly little is known about the mechanisms by which tobacco smoke mediates its disastrous effects. Here, we demonstrate that tobacco smoke dramatically changes vascular endothelial cell and tissue morphology, leading to a loss of endothelial barrier function within minutes. Long-term exposure of endothelial cells to tobacco smoke extracts induces necrosis that may trigger a pro-inflammatory status of the vessel wall. Pre-incubation of the extracts without cells for 6 h at 37 degrees C led to a complete loss of activity. Further, the endothelium could be rescued by changing to fresh medium even at times when the extracts had lost their activity. Finally, we show that N-acetyl cysteine and statins inhibit the adverse tobacco smoke effects.

Apoptotic pathways activated by histone deacetylase inhibitors: implications for the drug-resistant phenotype

Histones are abundant proteins that coordinate the organization of eukaryotic nucleosomes. Post-translational modifications of histones-acetylation, phosphorylation and methylation-locally modulate the higher order nucleosome structure. Acetylation and deacetylation of histones occur at their N-terminal tails in a dynamic fashion and influence DNA accessibility to factors regulating replication, repair and transcription. Acetylation, catalyzed by histone acetyltransferases (HATs) on the epsilon-NH(2) group of lysine residues, neutralizes the positive charge and thereby triggers transcriptional activation. Deacetylation, catalyzed by histone deacetylases (HDACs) on the same lysine residues, unmasks the charge and triggers transcriptional repression. Inhibition of HDACs has thus a broad effect on chromatin architecture, and possibly on protein function, and multiple effects on cell growth. HDAC inhibitors (HDIs) are promising as single anti-cancer agents and in combination therapies. Understanding of the molecular basis for HDIs action is needed to better design the clinical antitumor treatments. The apoptotic pathways induced by HDIs are emerging and we provide an overview of the recent findings that regard apoptotic key elements. We also propose that transformed cells discern the widespread effect of HDIs on chromatin architecture as a genotoxic insult to respond to through induction of apoptosis.

The histone deacetylase inhibitor suberic bishydroxamate: a potential sensitizer of melanoma to TNF-related apoptosis-inducing ligand (TRAIL) induced apoptosis

TRAIL appears to be a promising anticancer agent in that it induces apoptosis in a wide range of cancer cells but not normal tissues. Sensitivity of melanoma cells to TRAIL-induced apoptosis varied considerably because of their development of various resistance mechanisms against apoptosis. We discuss in this report the potential effect of a histone deacetylase inhibitor SBHA on TRAIL-induced apoptosis. Histone deacetylase (HDAC) inhibitors regulate histone acetylation and thereby modulate the transcriptional activity of certain genes leading to cell growth arrest, cellular differentiation, and apoptosis. Suberic bishydroxamate (SBHA) is a relatively new HDAC inhibitor that induced apoptosis in the majority of melanoma cell lines through a mitochondrial and caspase-dependent pathway. This was due to its regulation of the expression of multiple proteins that are involved in either the mitochondrial apoptotic pathway (Bcl-2 family members) or the final phase of apoptosis (caspase-3 and XIAP). Co-treatment with SBHA at nontoxic doses and TRAIL resulted in a marked increase in TRAIL-induced apoptosis of melanoma, but showed no toxicity to melanocytes. SBHA appeared to sensitize melanoma to TRAIL-induced apoptosis by up-regulation of pro-apoptotic proteins in the TRAIL-induced apoptotic pathway such as caspase-8, caspase-3, Bid, Bak, and Bax, and up-regulation of the BH3 domain only protein, Bim. This, together with activated Bid, may have acted synergistically to cause changes in mitochondria. Treatment with SBHA also resulted in down-regulation of antiapoptotic members of the Bcl-2 family, Bcl-X(L) and Mcl-1, and the IAP member, XIAP. These changes would further facilitate apoptotic signaling. SBHA appeared therefore to be a potent agent in overcoming resistance of melanoma to TRAIL-induced apoptosis.

NVP-LAQ824 is a potent novel histone deacetylase inhibitor with significant activity against multiple myeloma

Histone deacetylase (HDAC) inhibitors are emerging as a promising new treatment strategy in hematologic malignancies. Here we show that NVP-LAQ824, a novel hydroxamic acid derivative, induces apoptosis at physiologically achievable concentrations (median inhibitory concentration [IC50] of 100 nM at 24 hours) in multiple myeloma (MM) cell lines resistant to conventional therapies. MM.1S myeloma cell proliferation was also inhibited when cocultured with bone marrow stromal cells, demonstrating ability to overcome the stimulatory effects of the bone marrow microenvironment. Importantly, NVP-LAQ824 also inhibited patient MM cell growth in a dose- and time-dependent manner. NVP-LAQ824-induced apoptotic signaling includes up-regulation of p21, caspase cascade activation, and poly (adenosine diphosphate [ADP]) ribose (PARP) cleavage. Apoptosis was confirmed with cell cycle analysis and annexin-propidium iodide staining. Interestingly, treatment of MM cells with NVPLAQ824 also led to proteasome inhibition, as determined by reduced proteasome chymotrypsin-like activity and increased levels of cellular polyubiquitin conjugates. Finally, a study using NVP-LAQ824 in a preclinical murine myeloma model provides in vivo relevance to our in vitro studies. Taken together, these findings provide the framework for NVP-LAQ824 as a novel therapeutic in MM.

Che-1 arrests human colon carcinoma cell proliferation by displacing HDAC1 from the p21WAF1/CIP1 promoter

Che-1 is a recently identified human RNA polymerase II binding protein involved in the regulation of gene transcription and cell proliferation. We previously demonstrated that Che-1 inhibits the Rb growth-suppressing function by interfering with Rb-mediated HDAC1 recruitment on E2F target gene promoters. By hybridization of cancer profile arrays, we found that Che-1 expression is strongly down-regulated in several tumors, including colon and kidney carcinomas, compared with the relative normal tissues. Consistent with these data, Che-1 overexpression inhibits proliferation of HCT116 and LoVo human colon carcinoma cell lines by activation of the cyclin-dependent kinase inhibitor p21WAF1/Cip1 in a p53-independent manner and by promoting growth arrest at the G1 phase of the cell cycle. Che-1 activates p21WAF1/Cip1 by displacing histone deacetylase (HDAC)1 from the Sp1 binding sites of the p21WAF1/Cip1 gene promoter and accumulating acetylated histone H3 on these sites. Accordingly, Che-1-specific RNA interference negatively affects p21WAF1/Cip1 transactivation and increases cell proliferation in HCT116 cells. Taken together, our results indicate that Che-1 can be considered a general HDAC1 competitor and its down-regulation is involved in colon carcinoma cell proliferation.

ZBP-89 mediates butyrate regulation of gene expression

Inducible p53-independent regulation of the cyclin-dependent kinase inhibitor p21(Waf1) transcription is mediated through its proximal GC-rich sites. Prior studies have shown that Sp1, Sp3 and the histone acetyltransferase coactivator p300 are components of the complexes that bind to these sites. Although Sp1 and Sp3 collaborate with p300, a direct interaction between Sp1 and p300 does not occur. Zinc-finger binding protein-89 (ZBP-89, also known as BFCOL1, BERF-1 and ZNF-148) is a Krüppel-type zinc-finger transcription factor that binds to the same GC-rich sequences as Sp1. We sought to determine whether ZBP-89 is a target of p300 during butyrate induction of p21(Waf1). This review summarizes the evidence that supports a crucial role for ZBP-89 in butyrate regulation of p21(Waf1). Adenovirus-mediated expression of ZBP-89 in HT-29 cells reveals that ZBP-89 potentiates butyrate induction of endogenous p21(Waf1) gene expression. DNA-protein interaction assays demonstrate that Sp1, Sp3 and ZBP-89 bind the p21(Waf1) promoter at -245 to -215. Coprecipitation assays reveal that p300 preferentially binds to the N-terminus of ZBP-89. ZBP-89 also induces p21(Waf1) through stabilization of p53. Although ZBP-89 binds mutant and wild-type p53, only wild-type p53 is stabilized. Moreover, mutant p53 shifts the subnuclear location of ZBP-89 to the nuclear periphery, which is a domain rich in heterochromatin. This finding led to the conclusion that mutant p53 exerts a dominant negative effect on ZBP-89. We propose that gene silencing by mutant p53 might be mediated by sequestering ZBP-89 within heterochromatin regions at the nuclear periphery. Overall, ZBP-89 is a butyrate-regulated coactivator of p53 and is able to induce p21(Waf1) gene expression through both p53-dependent and -independent mechanisms to inhibit cell growth.

Enhanced MTT-reducing activity under growth inhibition by resveratrol in CEM-C7H2 lymphocytic leukemia cells

Inhibition of proliferation by resveratrol of CEM-C7H2 lymphocytic leukemia cells was paradoxically associated with an enhanced cellular 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT)-reducing activity. This phenomenon was most pronounced at the sub-apoptotic concentration range of 5-20 microM resveratrol. The results of our study show that the MTT-reducing activity can be increased by the polyphenolic antioxidant resveratrol without a corresponding increase in the number of living cells and that this occurs at a concentration range of the antioxidant which is not sufficient to induce apoptosis but suffices to slow down cell growth. This phenomenon appears to be restricted to proliferation inhibitors with antioxidant properties and is cell type-specific. Thus, in determining the effects of flavonoids and polyphenols on proliferation, in certain cell types this might represent a pitfall in the MTT proliferation assay.

Histone deacetylase inhibitors: a new class of immunosuppressors targeting a novel signal pathway essential for CD154 expression

Here we report that histone deacetylase inhibitors (HDAC-i) comprise a new class of immunosuppressive agents. HDAC-i inhibited CD4 T-cell proliferation in a dose-dependent manner, which was not caused by apoptosis or decreased viability. Although early intracellular signals such as tyrosine kinase activity and elevation of intracellular calcium concentration were not affected, the characteristic aggregation of T cells following activation was completely abrogated. This correlated with diminished activation-induced expression of the adhesion molecules. HDAC-i furthermore inhibited activation-induced CD25 and CD154 expression on CD4 cells, without affecting induction of CD69. HDAC-i inhibited CD154 expression by a mechanism distinctly different from cyclosporine-mediated inhibition. HDAC-i thus inhibited interleukin 2 (IL-2)-induced CD154 expression on effector T cells and constitutively expressed CD154 on various tumor cells, events that were not affected by cyclosporine. Additional studies showed that HDAC-i treatment inhibited c-Myc expression, which was further shown to be important for CD154 gene activation. These results demonstrate pronounced T-cell inhibitory activity of HDAC-i, which may form the basis of novel therapeutic interventions against autoimmune diseases and allograft rejection.

Apoptosis sensitivity is not correlated with sensitivity to proliferation inhibition by the histone deacetylase inhibitors butyrate and TSA

We investigated a set of cell lines as to their sensitivity to proliferation inhibition, on the one side, and apoptosis induction, on the other, by the core histone deacetylase inhibitors butyrate and trichostatin A (TSA), respectively. The results can be summarized as follows: (i) the investigated cell lines can be classified into three groups of high, medium and low sensitivity to proliferation inhibition by the histone deacetylase inhibitors; (ii) there is no correlation between the sensitivities to proliferation inhibition and the sensitivities to apoptosis induction by the histone deacetylase inhibitors; (iii) a comparison of the relative sensitivities to butyrate versus TSA with regard to proliferation inhibition and apoptosis induction, respectively, revealed that besides a good correlation most often encountered, there are also cell lines with conspicuously differing relative sensitivities to the two structurally different histone deacetylase inhibitors.

Histone deacetylase inhibitors potently repress CXCR4 chemokine receptor expression and function in acute lymphoblastic leukaemia

The chemokine receptor CXCR4 plays a crucial role in the survival and trafficking of leukaemia cells and requires further attention as human immunodeficiency virus type I (HIV-I) utilises CXCR4 as the major coreceptor for cellular entry. We demonstrated that inhibitors of histone deacetylases, currently being tested in clinical trials for the treatment of various tumours, extensively downregulated CXCR4 protein and mRNA levels in leukaemia cell lines and lymphoblasts from patients with childhood acute leukaemia. As a result, the ability of stromal cell-derived factor-1 to induce cellular migration was impaired. Repression of CXCR4 transcription by inhibitors of histone deacetylases might therefore represent a promising novel approach in the treatment of acute leukaemias.

Transcriptional regulation of cyclooxygenase-1 by histone deacetylase inhibitors in normal human astrocyte cells

While cyclooxygenase (COX)-2 is a highly inducible gene, COX-1 is widely known as a noninducible gene and is constitutively expressed in a variety of cell lines and human tissues. Recently, several reports have indicated that COX-1 is also regulated at the transcriptional level by various stimuli. We present evidence that histone deacetylase (HDAC) inhibitors induce COX-1 transcription and translation in normal human astrocyte (NHA) cells and glioma cell lines. HDAC inhibitors increased acetylated histone H4 protein expression in NHA cells. The levels of COX-1 mRNA and protein were maximal at 24 and 48 h, respectively, after treatment with the specific HDAC inhibitor, trichostatin A (TSA). In addition, TSA-treated NHA cells produced prostaglandin E(2) as determined by enzyme-linked immunosorbent assay after incubation with 10 microm exogenous arachidonic acid, indicating that the induced COX-1 is functionally active. In addition to NHA cells, this up-regulation of COX-1 after treatment with HDAC inhibitors was observed in 5 different glioma cell lines. The nucleotide sequence of the inducible COX-1 cDNA was confirmed identical to human COX-1 that was previously reported. HDAC inhibitors stimulated COX-1 promoter activity as measured by luciferase reporter assays, suggesting that the induction of COX-1 is regulated at the transcriptional level. Furthermore, mutation analysis of the COX-1 promoter suggests that TSA-responsive element exists in the proximal Sp1-binding site at +25 to +31. In conclusion, COX-1 is an inducible gene in glial-derived cells including immortalized cells, and appears to be transcriptionally regulated by a unique mechanism associated with histone acetylation.

Valproic acid induces apoptosis in human leukemia cells by stimulating both caspase-dependent and -independent apoptotic signaling pathways

We investigated the effects of valproic acid (VPA) on the growth and survival of human leukemia cell lines. VPA induced cell death in all of the nine cell lines tested in a dose dependent manner. VPA-treatment induced apoptotic changes in MV411 cells including DNA fragmentation, phosphatidylserine externalization, cytochrome c release from mitochondria, and activation of caspases-3, -8, and -9. A caspase inhibitor, zVAD-FMK, inhibited the DNA fragmentation induced by VPA but not cell death. These findings suggest that VPA exerts an anti-leukemic effect by both caspase-dependent and -independent apoptotic signaling pathways.

Differential effects of short-chain fatty acids on head and neck squamous carcinoma cells

OBJECTIVES/HYPOTHESIS

Head and neck squamous cell carcinoma (HNSCC) is a major cause of mortality. Despite advances in therapeutic modalities, recurrences and second primaries are commonly observed. Biological agents that can suppress growth of tumors that are otherwise difficult to treat are greatly needed. The present study examined the effects of short-chain fatty acids on HNSCC cell lines.

STUDY DESIGN

The effects of short-chain fatty acids on HNSCC cells was examined using tissue culture and immunoblotting techniques.

METHODS

The effects of four short-chain fatty acids, arginine butyrate, alpha-methyl hydrocinnamic acid, 2,2-dimethylbutyrate, and alpha-lipoic acid, were evaluated on four HNSCC cell lines (FaDu, SCC9, SCC25, and Detroit-562). Proliferation assays were performed by means of spectrophotometric techniques. Histone deacetylase activity was assessed by identifying the amount of acetylated histone H4. Involucrin expression was determined to assess cellular differentiation.

RESULTS

Inhibition of cellular proliferation was determined after 5 days of incubation with increasing doses with short-chain fatty acids. Arginine butyrate and alpha-lipoic acid were most effective in suppressing growth. Arginine butyrate demonstrated strong histone deacetylase inhibition in FaDu cells, while not inducing cellular differentiation. The short-chain fatty acid alpha-lipoic acid demonstrated weak histone deacetylase inhibition but was the only short-chain fatty acid that induced involucrin expression in at least two of the cell lines. Histone deacetylase inhibitory activity or induction of involucrin expression correlated with suppression of cell growth.

CONCLUSIONS

Short-chain fatty acids have variable effects on HNSCC cells. Arginine butyrate and alpha-lipoic acid are the most effective in suppressing growth and appear to do so through different biochemical mechanisms. These compounds warrant further research as chemotherapeutic or chemopreventive agents in HNSCC.

Histone-deacetylase inhibitors: novel drugs for the treatment of cancer

The opposing actions of histone acetyltransferases (HATs) and histone deacetylases (HDACs) allow gene expression to be exquisitely regulated through chromatin remodelling. Aberrant transcription due to altered expression or mutation of genes that encode HATs, HDACs or their binding partners, is a key event in the onset and progression of cancer. HDAC inhibitors can reactivate gene expression and inhibit the growth and survival of tumour cells. The remarkable tumour specificity of these compounds, and their potency in vitro and in vivo, underscore the potential of HDAC inhibitors as exciting new agents for the treatment of cancer.

Potentiating antitumor effects of a combination therapy with lovastatin and butyrate in the Lewis lung carcinoma model in mice

Lovastatin, the drug used for the treatment of hypercholesterolemia, has previously been reported to exert antitumor activity in experimental murine models. Butyrate and butyric acid derivatives are well known to induce differentiation and apoptosis of tumour cells and also have recently gained acceptance as potential anticancer agents. In this study, we examined the antitumor effects of the combination of lovastatin and butyrate or its prodrug tributyrin in vitro and in vivo against a murine Lewis lung carcinoma (3LL). This combination therapy showed synergistic antitumor activity against 3LL cells in vitro. These effects were at least in part due to apoptosis induction that occurred after 12 hr of incubation with lovastatin and butyrate and was preceded by changes in cell cycle distribution of treated cells and expression of p21, p53 and cyclin D1. Remarkably, a systemic treatment of syngeneic mice inoculated with 3LL cells with both drugs resulted in significant tumour growth retardation.

Propionibacteria induce apoptosis of colorectal carcinoma cells via short-chain fatty acids acting on mitochondria

The genus Propionibacterium is composed of dairy and cutaneous bacteria which produce short-chain fatty acids (SCFA), mainly propionate and acetate, by fermentation. Here, we show that P. acidipropionici and freudenreichii, two species which can survive in the human intestine, can kill two human colorectal carcinoma cell lines by apoptosis. Propionate and acetate were identified as the major cytotoxic components secreted by the bacteria. Bacterial culture supernatants as well as pure SCFA induced typical signs of apoptosis including a loss of mitochondrial transmembrane potential, the generation of reactive oxygen species, caspase-3 processing, and nuclear chromatin condensation. The oncoprotein Bcl-2, which is known to prevent apoptosis via mitochondrial effects, and the cytomegalovirus-encoded protein vMIA, which inhibits apoptosis and interacts with the mitochondrial adenine nucleotide translocator (ANT), both inhibited cell death induced by propionibacterial SCFA, suggesting that mitochondria and ANT are involved in the cell death pathway. Accordingly, propionate and acetate induced mitochondrial swelling when added to purified mitochondria in vitro. Moreover, they specifically permeabi-lize proteoliposomes containing ANT, indicating that ANT can be a critical target in SCFA-induced apoptosis. We suggest that propionibacteria could constitute probiotics efficient in digestive cancer prophylaxis via their ability to produce apoptosis-inducing SCFA.

Sodium butyrate induces P53-independent, Fas-mediated apoptosis in MCF-7 human breast cancer cells

1. This study was performed to determine the effect and action mechanisms of sodium butyrate (NaB) on the growth of breast cancer cells. 2. Butyrate inhibited the growth of all breast cancer cell lines analysed. It induced cell cycle arrest in G1 and apoptosis in MCF-7, MCF-7ras, T47-D, and BT-20 cells, as well as arrest in G2/M in MDA-MB-231 cells. 3. Transient transfection of MCF-7 and T47-D cells with wild-type and antisense p53 did not modify butyrate-induced apoptosis. Pifithrin-alpha, which inhibits the transcriptional activity of P53, did not modify cell growth or apoptosis of MCF-7 and T47-D cells treated with butyrate. These results indicate that P53 was not involved in butyrate-induced growth inhibition of breast cancer cells. 4. Treatment of MCF-7 cells with anti-Fas agonist antibody induced cell death, indicating that Fas was functional in these cells. Moreover, butyrate potentiated Fas-induced apoptosis, as massive apoptosis was observed rapidly when MCF-7 cells were treated with butyrate and anti-Fas agonist antibody. In addition, butyrate-induced apoptosis in MCF-7 cells was considerably reduced by anti-Fas antagonist antibody. Western blot analysis showed that butyrate increased Fas and Fas ligand levels (Fas L), indicating that butyrate-induced apoptosis may be mediated by Fas signalling. 5. These results demonstrate that butyrate inhibited the growth of breast cancer cells in a P53-independent manner. Moreover, it induced apoptosis via the Fas/Fas L system and potentiated Fas-triggered apoptosis in MCF-7 cells. These findings may open interesting perspectives in human breast cancer treatment strategy.

Histone deacetylase inhibitors induce apoptosis in peripheral blood lymphocytes along with histone H4 acetylation and the expression of the linker histone variant, H1 degrees

The results of this study show that H1 degrees can be induced by sodium butyrate and trichostatin A in peripheral blood lymphocytes, a cell system which does not normally express this linker histone variant. Moreover, this induced expression was found to be correlated in a dose-dependent manner with the concomitant induction of apoptosis and increased levels of histone H4 acetylation. Sodium butyrate and trichostatin A, both inhibitors of histone deacetylases, are known to induce terminal differentiation and at the same time the induction of the linker histone variant, H1 degrees, in a number of tissue/cell systems. Moreover, aside from induced expression by histone deacetylase inhibitors, H1 degrees gene expression has also been tightly associated with the process of terminal differentiation in many physiological tissue/cell systems. The concomitant induction of H1 degrees expression along with apoptosis and histone acetylation in the same cell system has not been previously reported. Histone acetylation is known to be involved in chromatin remodelling events. Such events also occur during apoptosis. The association of H1 degrees gene expression with apoptosis, and not with differentiation in these cells, leads to more general implications as to a potential functional role of H1 degrees during chromatin remodelling.

Histone deacetylase inhibitors induce caspase-dependent apoptosis and downregulation of daxx in acute promyelocytic leukaemia with t(15;17)

Histone deacetylase (HDAC) appears to play an important role in the pathogenesis of acute promyelocytic leukaemia (APL) as it is recruited by both PML-RARalpha and PLZF/RAR alpha in leukaemic cells with t(15;17) and t(11;17) respectively. Recent studies have demonstrated that HDAC inhibitors can be therapeutically used in various neoplastic disorders including APL. Cell differentiation was considered the major mechanism of the anti-leukaemic effects of HDAC inhibitors in APL. However, most of these studies either evaluated the effect of HDAC inhibitors in combination with all-trans retinoic acid (ATRA) or focused on the less common form of APL with t(11;17). To investigate the cellular effects of HDAC inhibitors, including sodium butyrate, trichostatin A, and suberoylanilide hydroxamic acid (SAHA), we used two APL cell lines, NB4 and the ATRA-resistant derivative NB4.306. Moreover, primary cells from five patients with cytogenetic evidence for t(15;17) were also studied. Our results demonstrated that HDAC inhibitors induce distinct caspase-dependent apoptosis in APL, which showed both concentration-and time-dependence. In addition, changes in the apoptosis-regulatory proteins, daxx, bcl-2 and bax were analysed. HDAC inhibitors induced downregulation of daxx, but no significant changes were detected in bcl-2 or bax. In conclusion, apoptosis induced by HDAC inhibitors in APL could provide an effective strategy for treatment of patients with t(15;17).

Inhibition of histone deacetylase activity enhances Fas receptor-mediated apoptosis in leukemic lymphoblasts

We recently reported that butyrate, an inhibitor of histone deacetylases, is capable of inducing Fas-independent apoptosis in the acute lymphoblastic leukemia cell line CCRF-CEM. Here we demonstrate that butyrate enhances Fas-induced apoptosis in this cell line. The application of different histone deacetylase inhibitors revealed that tetra-acetylated histone H4 is associated with the amplifying effect of butyrate on Fas-induced cell death. FasL, Fas, FADD, RIP, caspase-8, caspase-3, Bid, FLIP(S+L), FLASH and FAP-1, proteins known to act within the Fas-apoptosis cascade, showed no changes in their expression levels in cells treated with butyrate compared with untreated cells. Analyses of Fas-oligomerization and Western blotting as well as enzyme activity assays of caspase-2, caspase-3 and caspase-8 suggest that butyrate enhances Fas-induced apoptosis downstream of Fas but upstream of caspase-8 activation. In immunoprecipitation experiments a 37 kD butyrate-regulated protein was detected which specifically interacts with caspase-8.

Butyrate sensitizes human colon cancer cells to TRAIL-mediated apoptosis

BACKGROUND

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a novel member of the tumor necrosis factor family, induces apoptosis in TRAIL-sensitive tumors through the activation of the caspase pathway. Sodium butyrate (NaBT) induces differentiation and apoptosis in certain colorectal cancers; the molecular mechanisms for these effects have not been clearly defined. The purpose of our study was to determine whether NaBT sensitizes TRAIL-resistant human colon cancer cells to the effects of TRAIL.

METHODS

Human colon cancer cells (KM12C, KML4A, and KM20) that are resistant to TRAIL treatment alone were treated with TRAIL (100 ng/mL), NaBT (5 mmol/L), or a combination of these agents and harvested for total RNA and protein. Western blots were performed to assess intracellular expression of Flice-like inhibitory protein (FLIP), a caspase inhibitor. Percent-specific apoptosis, relative caspase-3 activity, and Annexin-V immunofluorescence were determined at 24 and 48 hours. Cell cycle--related gene expression was assessed by RNase protection.

RESULTS

Treatment with NaBT for 24 and 48 hours decreased FLIP protein expression in all cell lines. Furthermore, NaBT sensitized these resistant cancer cells to the effects of TRAIL with significant increases noted in cell death, caspase-3 activity, and Annexin-V staining compared with NaBT alone.

CONCLUSIONS

Our findings suggest that the reduction of FLIP protein levels by NaBT renders TRAIL-resistant human colon cancer cells sensitive to TRAIL-mediated apoptosis. The combination of TRAIL with agents (such as NaBT, which target proteins that prevent cell death) may provide a more effective and less toxic regimen for the treatment of resistant colon cancers.

Synergistic growth inhibition of prostate cancer cells by 1 alpha,25 Dihydroxyvitamin D(3) and its 19-nor-hexafluoride analogs in combination with either sodium butyrate or trichostatin A

Prostate cancer is a major cause of male cancer death. In vitro and in vivo data support a role for 1 alpha,25 Dihydroxyvitamin D(3) (1 alpha,25(OH)(2)D(3)) in regulating the growth and differentiation of the normal prostate gland yet prostate cancer cells appear significantly less sensitive to this action. Vitamin D(3) receptor (VDR) content or mutational status do not correlate clearly with the antiproliferative effects of 1 alpha,25(OH)(2)D(3) and therefore it is unclear why prostate cancer cell lines are significantly less sensitive to this action. We hypothesized that the antiproliferative responses of prostate cancer cells to 1 alpha,25(OH)(2)D(3) are suppressed by a process involving histone deacetylation. Sodium butyrate (NaB) and trichostatin A (TSA) are inhibitors of histone deacetylase (HDAC) activity. Low doses of NaB or TSA (300 microM and 15 nM respectively), which alone were relatively inactive, synergized with 1 alpha,25(OH)(2)D(3) in liquid and semi-solid agar to inhibit the growth of LNCaP, PC-3 and DU-145 prostate cancer cells. Still greater synergy was observed between vitamin D(3) hexafluoride analogs and either NaB or TSA. The mechanism appeared to involve neither the cyclin-dependent kinase inhibitor, p21((waf1/cip1)) nor cell cycle arrest, but rather induction of apoptosis. These data suggest that cells dysregulate the normal pro-apoptotic signals of 1 alpha,25(OH)(2)D(3) during prostate cancer development by a mechanism involving histone deacetylation. Combination therapy with potent vitamin D(3) analogs and clinically approved HDAC inhibitors may overcome this lesion and improve the treatment of both androgen-dependent and independent prostate cancer.

Region of herpes simplex virus type 1 latency-associated transcript sufficient for wild-type spontaneous reactivation promotes cell survival in tissue culture

The latency-associated transcript (LAT) is the only abundant herpes simplex virus type 1 (HSV-1) transcript expressed during latency. In the rabbit eye model, LAT null mutants do not reactivate efficiently from latency. We recently demonstrated that the LAT null mutant dLAT2903 induces increased levels of apoptosis in trigeminal ganglia of infected rabbits compared to LAT+ strains (G.-C. Perng, C. Jones, J. Ciacci-Zarella, M. Stone, G. Henderson, A. Yokht, S. M. Slanina, F. M. Hoffman, H. Ghiasi, A. B. Nesburn, and C. S. Wechsler, Science 287:1500-1503, 2000). The same study also demonstrated that a plasmid expressing LAT nucleotides 301 to 2659 enhanced cell survival of transfected cells after induction of apoptosis. Consequently, we hypothesized that LAT enhances spontaneous reactivation in part, because it promotes survival of infected neurons. Here we report on the ability of plasmids expressing different portions of the 5' end of LAT to promote cell survival after induction of apoptosis. A plasmid expressing the first 1.5 kb of LAT (LAT nucleotides 1 to 1499) promoted cell survival in neuro-2A (mouse neuronal) and CV-1 (monkey fibroblast) cells. A plasmid expressing just the first 811 nucleotides of LAT promoted cell survival less efficiently. Plasmids expressing the first 661 nucleotides or less of LAT did not promote cell survival. We previously showed that a mutant expressing just the first 1.5 kb of LAT has wild-type spontaneous reactivation in rabbits, and a mutant expressing just the first 811 nucleotides of LAT has a reactivation frequency higher than that of dLAT2903 but lower than that of wild-type virus. In addition, mutants reported here for the first time, expressing just the first 661 or 76 nucleotides of LAT, had spontaneous reactivation indistinguishable from that of the LAT null mutant dLAT2903. In summary, these studies provide evidence that there is a functional relationship between the ability of LAT to promote cell survival and its ability to enhance spontaneous reactivation.

Histone deacetylase inhibitors promote apoptosis and differential cell cycle arrest in anaplastic thyroid cancer cells

Little information exists concerning the response of anaplastic thyroid carcinoma (ATC) cells to histone deacetylase inhibitors (HDAIs). In this study, the cellular response to the histone deacetylase inhibitors, sodium butyrate and trichostatin A, was analyzed in cell lines derived from primary anaplastic thyroid carcinomas. HDAIs repress the growth (proliferation) of ATC cell lines, independent of p53 status, through the induction of apoptosis and differential cell cycle arrest (arrested in G1 and G2/M). Apoptosis increases in response to drug treatment and is associated with the appearance of the cleaved form of the caspase substrate, poly-(ADP-ribose) polymerase (PARP). Cell cycle arrest is associated with the reduced expression of cyclins A and B, the increased expression of the cyclin-dependent kinase inhibitors, p21(Cip1/WAF1) and p27Kip1, the reduced phosphorylation of the retinoblastoma protein (pRb), and a reduction in cdk2 and cdk1-associated kinase activities. In ATC cells overexpressing cyclin E, drug treatment failed to replicate these events. These results suggest that growth inhibition of ATC cells by HDAIs is due to the promotion of apoptosis through the activation of the caspase cascade and the induction of cell cycle arrest via a reduction in cdk2- and cdk1-associated kinase activities.

Functional analysis of the leukemia protein ELL: evidence for a role in the regulation of cell growth and survival

The ELL gene encodes an RNA polymerase II transcription factor that frequently undergoes translocation with the MLL gene in acute human myeloid leukemia. Here, we report that ELL can regulate cell proliferation and survival. In order to better understand the physiological role of the ELL protein, we have developed an ELL-inducible cell line. Cells expressing ELL were uniformly inhibited for growth by a loss of the G(1) population and an increase in the G(2)/M population. This decrease in cell growth is followed by the condensation of chromosomal DNA, activation of caspase 3, poly(ADP ribose) polymerase cleavage, and an increase in sub-G(1) population, which are all indicators of the process of programmed cell death. In support of the role of ELL in induction of cell death, expression of an ELL antisense RNA or addition of the caspase inhibitor ZVAD-fmk results in a reversal of ELL-mediated death. We have also demonstrated that the C-terminal domain of ELL, which is conserved among the ELL family of proteins that we have cloned (ELL, ELL2, and ELL3), is required for ELL's activity in the regulation of cell growth. These novel results indicate that ELL can regulate cell growth and survival and may explain how ELL translocations result in the development of human malignancies.

Gene expression profiles of proliferating vs. G1/G0 arrested human leukemia cells suggest a mechanism for glucocorticoid-induced apoptosis

Glucocorticoids (GC) have pronounced effects on metabolism, differentiation, proliferation, and cell survival (1). In certain lymphocytes and lymphocyte-related malignancies, GC inhibit proliferation and induce apoptotic cell death, which has led to their extensive use in the therapy of malignant lymphoproliferative disorders (2). Most of these effects result from regulation of gene expression via the GC receptor (GR), a ligand-activated transcription factor (3). Although hundreds of genes are regulated by GC (1), how certain biological GC effects relate to individual gene regulation remains enigmatic. To address this question with respect to GC-induced cell cycle arrest and apoptosis, we applied DNA chip technology (4, 5) to determine gene expression profiles in proliferating and G1/G0-arrested (by conditional expression of the CDK inhibitor p16/INK4a) acute lymphoblastic T cells undergoing GC-induced apoptosis. Of 7074 genes tested, 163 were found to be regulated by dexamethasone in the first 8 h in proliferating cells and 66 genes in G1/G0-arrested cells. An almost nonoverlapping set of genes (i.e., only eight genes) was coordinately regulated in proliferating and arrested cells. Analysis of the regulated genes supports the concept that GC-induced apoptosis results from positive GR autoregulation entailing persistent down-regulation of metabolic pathways critical for survival

Downregulation of MLL-CBP fusion gene expression is associated with differentiation of SN-1 cells with t(11;16)(q23;p13)

The translocation t(11;16)(q23;p13) has only been documented in patients with acute leukemia or myelodysplasia secondary to therapy with drugs targeting DNA topoisomerase II. We have established a myeloid cell line (SN-1) with the MLL-CBP fusion gene from an acute leukemia patient with t(11;16)(q23;p13). Although SN-1 cells were not induced to differentiate by all-trans retinoic acid (ATRA) and 1alpha,25-dihydroxyvitamin D(3) (VD3), retinoid X receptor (RXR) agonists, such as 9-cis retinoic acid and Ro48-2250, effectively induced differentiation of the cells. Downregulation of the expression of the MLL-CBP fusion gene occurred during the differentiation of SN-1 cells. When SN-1 cells were treated with MLL-CBP antisense oligonucleotide, the cells were induced to differentiate by ATRA or VD3, suggesting that the MLL-CBP fusion gene dominant-negatively suppresses ATRA- or VD3-induced differentiation. Moreover, suboptimal concentrations of sodium butyrate, a histone deacetylase inhibitor, had a cooperative effect with ATRA or VD3 in inducing the differentiation of SN-1 cells. The downregulation of the expression of MLL-CBP mRNA was accompanied by the induction of differentiation. These findings suggest that RXR agonists or a clinically applicable combination of ATRA and butyrate derivatives might be useful for differentiation therapy in leukemia patients with the MLL-CBP fusion gene.

Butyrate alters the expression and activity of cell cycle components in anaplastic thyroid carcinoma cells

Anaplastic thyroid carcinoma (ATC) is the most malignant and aggressive form of thyroid cancer. Most patients die within months of diagnosis, primarily due to the absence of effective chemotherapeutic strategies. Identifying alternative therapies is necessary to increase long-term survival. Butyrate elicits a number of responses from cancer cells both in vitro and in vivo including growth repression, cell cycle arrest, differentiation, and apoptosis. Even though many types of cancer cells have been studied, little is known of the response of ATC cells to this drug. In this study, we report that butyrate induces differential cell cycle arrest (arrest in G1 and G2/M phases) in an ATC cell line that correlates with changes in the expression, phosphorylation, and activity of key components of the cell cycle machinery. Exposure to butyrate increases the expression of the cyclin-dependent kinase inhibitors, p21/Cip1 and p27/Kip1, decreases the expression of cyclin A and cyclin B, inhibits the phosphorylation of the retinoblastoma protein (pRb), and decreases the activity of cdk1 and cdk2-associated kinases. These results suggest that butyrate may be useful in the clinical treatment of ATC.

Apoptotic cytotoxic effects of a histone deacetylase inhibitor, FK228, on malignant lymphoid cells

Histone deacetylases are promising targets for cancer treatment. Here we studied the in vitro effects of a potent histone deacetylase inhibitor, FK228 (formerly FR901228), on human leukemia / lymphoma cells and cell lines compared with normal hematopoietic cells. In a lymphoma cell line, Raji, a nanomolar concentration of FK228 induced G1 arrest and / or apoptotic cell death, depending on the concentration and exposure time. Growth of lymphoid cell lines including Raji (N = 13) was inhibited by 50% (IC(50)) after 2-day treatment at concentrations of 0.83 to 1.87 ng / ml. Viability of clinical samples from patients with acute lymphoblastic leukemia was decreased by 50% at 0.78 +/- 0.46 ng / ml, whereas the IC(50) values for normal mononuclear cells from peripheral blood and bone marrow were 2.3 +/- 0.96 and 7.8 +/- 1.0 ng / ml, respectively. The IC(50) values for normal progenitor cells were 3.1, 4.4 and 7.8 ng / ml for BFU-E, CFU-GM and CFU-Mix, respectively. Expression levels of HDAC-1 and HDAC-3 proteins, which varied among cell lines, but were stable during the treatment with FK228, did not correlate with the sensitivity to FK288. This novel agent might be useful in the treatment of lymphoid malignancies, because the above concentrations are clinically achievable in vivo according to a recent clinical study.

Resveratrol causes arrest in the S-phase prior to Fas-independent apoptosis in CEM-C7H2 acute leukemia cells

Resveratrol (3,5,4'-trihydroxy-trans-stilbene), in the concentration range of 20 microM and above, induced arrest in the S-phase and apoptosis in the T cell-derived T-ALL lymphocytic leukemia cell line CEM-C7H2 which is deficient in functional p53 and p16. Expression of transgenic p16/INK4A, which causes arrest in G0/G1, markedly reduced the percentage of apoptotic cells. Antagonist antibodies to Fas or FasL, or constitutive expression of crmA did not diminish the extent of resveratrol-induced apoptosis. Furthermore, a caspase-8-negative, Fas-resistant Jurkat cell line was sensitive to resveratrol-induced apoptosis which could be strongly inhibited in the Jurkat as well as in the CEM cell line by z-VAD-fmk and z-IETD-fmk. The almost complete inhibition by z-IETD-fmk and the lack of inhibition by crmA suggested caspase-6 to be the essential initiator caspase. Western blots revealed the massive conversion of procaspase-6 to its active form, while caspase-3 and caspase-2 were proteolytically activated to a much lesser extent.