Histone Deacetylase Inhibitor FK228 Research Articles

FK228 sensitizes radioresistant small cell lung cancer cells to radiation

BackgroundConcurrent thoracic radiation plus chemotherapy is the mainstay of first-line treatment for limited-stage small cell lung cancer (LS-SCLC). Despite initial high responsiveness to combined chemo- and radiotherapy, SCLC almost invariably relapses and develops resistance within one year, leading to poor prognosis in patients with LS-SCLC. Developing new chemical agents that increase ionizing radiation’s cytotoxicity against SCLC is urgently needed.ResultsDual histone deacetylase (HDAC) and PI3K inhibitor FK228 not only displayed potent anticancer activity, but also enhanced the therapeutic effects of radiotherapy in SCLC cells. Mechanistically, radioresistant SCLC cells exhibit a lower level of histone H3K9 acetylation and a higher expression level of the MRE11-RAD50-NBS1 (MRN) complex and show more efficient and redundant DNA damage repair capacities than radiosensitive SCLC cells. FK228 pretreatment resulted in marked induction of H3k9 acetylation, attenuated homologous recombination (HR) repair competency and impaired non-homologous end joining (NHEJ) repair efficacy, leading to the accumulation of radiation-induced DNA damage and radiosensitization.ConclusionThe study uncovered that FK228 sensitized human radioresistant SCLC cells to radiation mainly through induction of chromatin decondensation and suppression of DNA damage signaling and repair. Our study provides a rational basis for a further clinical study to test the potential of FK228 as a radiosensitizing agent to increase the radiation-induced tumor cell kill in LS-SCLC patients.

Abstract PS16-11: Potential therapeutic effects of HDACi FK228 on TNBC using various models

Abstract Breast cancer is the most prevalent type of cancer among women. Most breast cancers are hormone sensitive, however triple negative breast cancer (TNBC), a more aggressive subtype of breast cancer is characterized by its negative expression of estrogen and progesterone receptors, and lack of Her2/NEU amplification. Because of its receptor status, hormone receptor targeted treatments are ineffective against TNBC making it difficult to treat. FK228, known as Romidepsin, is a histone deacetylase inhibitor (HDACi) that specifically targets the enzymes HDACs 1 and 2, tumor suppressor and other proteins exerting epigenetic changes on tumor cells resulting in anticancer activity. FK228 has not been studied in TNBC, but has been approved by the FDA for the treatment of peripheral T-cell lymphoma (PTCL), where the mechanism of action has demonstrated cell cycle arrest and apoptosis [1,2]. To assess the preliminary role of FK228 in breast cancer, a number of TNBC cell lines were treated with the drug and analyzed for suppression of cell cycle genes. Similar to PTCL, TNBC cell lines showed an increase in cell cycle arrest genes such as p21 and others subsequent to treatment. Moving forward, to recapitulate the tumor microenvironment we have utilized 2D and 3D culture, while PDXs (patient derived xenografts), an excellent translational tool. We first identified changes in morphology and migration in 2k1, MDA-MB 231 and HS-578t cell lines treated with FK228 under in-vitro conditions. Additional molecular studies also show a reversal of the epithelial to mesenchymal transition (EMT) in FK228 treated BC cell lines; specifically in relation to EMT genes CDH1 and ZEB2, both directly connected to HDAC1/2 activity. To further study the effects of FK228, PDXs are implanted into mice to study growth patterns, recurrence, metastatic potential and response to FK228 in different patient tumor models. FK228 showed a drastic suppression in tumorigenesis in model TU-BCX-2O0, prompting the study of several other models in tumorigenesis including TU-BX-4IC, 4M4 and 4QX. Metastasis was also monitored by H&E staining lung and liver tissue for analysis for each model, and using an in vivo model consisting of GFP/luciferase transfected breast cancer cells MDA-MB-231 and SUM-159 to monitor both the proliferation and spread of disease in mice. Ultimately this study aims to characterize the FK228 alteration of pathways involved in tumorigenesis, metastasis and resistance within TNBC. Citation Format: Madlin Alzoubi, Khoa Nguyen, Katherine Hebert, Margarite Matossian, Hope Burks, Bridgette Collins-Burow, Matthew Burow. Potential therapeutic effects of HDACi FK228 on TNBC using various models [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS16-11.

Contribution of STAT3 and RAD23B in Primary Sézary Cells to Histone Deacetylase Inhibitor FK228 Resistance

FK228 (romidepsin) and suberoylanilide hydroxamic acid (vorinostat) are histone deacetylase inhibitors (HDACi) approved by the US Food and Drug Administration for cutaneous T-cell lymphoma (CTCL), including the leukemic subtype Sézary syndrome. This study investigates RAD23B and STAT3 gene perturbations in a large cohort of primary Sézary cells and the effect of FK228 treatment on tyrosine phosphorylation of STAT3 (pYSTAT3) and RAD23B expression. We report RAD23B copy number variation in 10% (12/119, P ≤ 0.01) of SS patients, associated with reduced mRNA expression (P= 0.04). RAD23B knockdown in a CTCL cell line led to a reduction in FK228-induced apoptosis. Histone deacetylase inhibitor treatment significantly reduced pYSTAT3 in primary Sézary cells and was partially mediated by RAD23B. A distinct pattern of RAD23B-pYSTAT3 co-expression in primary Sézary cells was detected. Critically, Sézary cells harboring the common STAT3 Y640F variant were less sensitive to FK228-induced apoptosis and exogenous expression of STAT3 Y640F, and D661Y conferred partial resistance to STAT3 transcriptional inhibition by FK228 (P ≤ 0.0024). These findings suggest that RAD23B and STAT3 gene perturbations could reduce sensitivity to histone deacetylase inhibitors in SS patients.

Global analysis of histone lysine acetylation and proteomic changes in EC109 cells treated with the histone deacetylase inhibitor FK228

FK228 is a selective inhibitor of histone deacetylases that exhibits marked antitumor activity in cancer cells and xenograft models. However, the effect of FK228 on the global profile of histone lysine acetylation and the proteome of EC109 cells remains poorly understood. The present study aimed at analyzing histone lysine acetylation and identifying the proteomic changes in EC109 cells following treatment with FK228, using the stable isotope labelling by amino acids in cell culture technique and a high-sensitivity mass spectrometer. In total, 87 acetylation sites and 3,515 proteins revealed changes in response to FK228 treatment. Of the 87 acetylation sites, 25 were quantifiable and 19 were quantified with ratio of >1.3. Notably, no downregulated lysine acetylation (Kac) sites were quantified in the present study and the 62 unquantified Kac sites were only identified in the FK228-treated cells. Bioinformatic analysis revealed that these quantifiable proteins were primarily involved in multiple biological functions and metabolic pathways as well as in protein complexes. The results of the present study revealed the extensive lysine acetylome and proteome in EC109 cells and expanded upon the current understanding of the anticancer mechanism of FK228 in EC109 cells.

Effect of histone deacetylase inhibitor romidepsin on the in vitro growth of foetal fibroblast cells and early development of porcine-cloned embryos

This study was designed to explore the effects of histone deacetylase inhibitor romidepsin (FK228) treatment on the morphology, proliferation and karyotype of porcine foetal fibroblast cells and early developmental competence of somatic cell nuclear transfer (SCNT) embryos. We found that the treatment of foetal fibroblast cells with 0.1μM FK228 for 24 h did not alter normal morphology, proliferation rate and chromosome number of donor cells, while other treatments with different does and durations altered the above characteristics of donor cells seriously. Simultaneously, fusion rate, blastocyst rate and total cell number per SCNT blastocysts from different donor cell treatment groups were similar to the control group. We further found that the treatment of SCNT embryos with low-dose FK228 did not affect their developmental efficiency, but treatment with high dose dramatically caused blastocyst formation failure. In addition, 0.1μM FK228 treatment for 36 h significantly elevated total cell number per SCNT blastocysts. Finally, combined treatments of both donor cells and embryos significantly improved the cleavage rate of cloned embryos, but did not affect the blastocyst rate and total cell number. Taken together, histone deacetylase inhibitor FK228 with optimal dose and exposure duration can enhance early developmental efficiency of porcine SCNT embryos and blastocyst quality.

Long-term Engraftment of Multipotent Mesenchymal Stromal Cells That Differentiate to Form Myogenic Cells in Dogs With Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is an incurable genetic disease with early mortality. Multipotent mesenchymal stromal cells (MSCs) are of interest because of their ability to differentiate to form myogenic cells in situ. In the present study, methods were developed to expand cultures of MSCs and to promote the myogenic differentiation of these cells, which were then used in a new approach for the treatment of DMD. MSC cultures enriched in CD271(+) cells grew better than CD271-depleted cultures. The transduction of CD271(+) MSCs with MyoD caused myogenic differentiation in vitro and the formation of myotubes expressing late myogenic markers. CD271(+) MSCs in the myogenic cell lineage transplanted into dog leukocyte antigen (DLA)-identical dogs formed clusters of muscle-like tissue. Intra-arterial injection of the CD271(+) MSCs resulted in engraftment at the site of the cardiotoxin (CTX)-injured muscle. Dogs affected by X-linked muscular dystrophy in Japan (CXMD(J)) treated with an intramuscular injection of CD271(+) MSCs similarly developed muscle-like tissue within 8-12 weeks in the absence of immunosuppression. In the newly formed tissues, developmental myosin heavy chain (dMyHC) and dystrophin were upregulated. These findings demonstrate that a cell transplantation strategy using CD271(+) MSCs may offer a promising treatment approach for patients with DMD.

The HDAC Inhibitor FK228 Enhances Adenoviral Transgene Expression by a Transduction-Independent Mechanism but Does Not Increase Adenovirus Replication

The histone deacetylase inhibitor FK228 has previously been shown to enhance adenoviral transgene expression when cells are pre-incubated with the drug. Upregulation of the coxsackie adenovirus receptor (CAR), leading to increased viral transduction, has been proposed as the main mechanism. In the present study, we found that the highest increase in transgene expression was achieved when non-toxic concentrations of FK228 were added immediately after transduction, demonstrating that the main effect by which FK228 enhances transgene expression is transduction-independent. FK228 had positive effects both on Ad5 and Ad5/f35 vectors with a variety of transgenes and promoters, indicating that FK228 works mainly by increasing transgene expression at the transcriptional level. In some cases, the effects were dramatic, as demonstrated by an increase in CD40L expression by FK228 from 0.3% to 62% when the murine prostate cancer cell line TRAMP-C2 was transduced with Ad[CD40L]. One unexpected finding was that FK228 decreased the transgene expression of an adenoviral vector with the prostate cell-specific PPT promoter in the human prostate adenocarcinoma cell lines LNCaP and PC-346C. This is probably a consequence of alteration of the adenocarcinoma cell lines towards a neuroendocrine differentiation after FK228 treatment. The observations in this study indicate that FK228 enhances adenoviral therapy by a transduction-independent mechanism. Furthermore, since histone deacetylase inhibitors may affect the differentiation of cells, it is important to keep in mind that the activity and specificity of tissue- and tumor-specific promoters may also be affected.

A potential activity of valproic acid in the stimulation of interleukin-3−mediated megakaryopoiesis and erythropoiesis

Although the anticancer activities of histone deacetylase (HDAC) inhibitors have been studied, a role for HDAC in normal hematopoiesis has not been clearly defined. Previous studies have shown that the potent HDAC inhibitor FK228 stimulates interleukin (IL)-3-mediated erythropoiesis. Here, we examined whether the widely used valproic acid (VPA) affects megakaryopoiesis as well as erythropoiesis. CD34(+) cells were incubated in serum-free or serum-containing cultures with cytokines, with or without VPA. In the serum-free cultures containing IL-3+stem cell factor (SCF), VPA significantly increased generation of CD61(+)GPA(-) megakaryocytic and a CD61(+)GPA(+) mixture of megakaryocytic and erythroid precursors from CD34(+) hematopoietic precursors at a pharmacological concentration (100 microg/mL). The increase in generation of megakaryocytic and erythroid precursors by VPA was confirmed by replating cultured cells with thrombopoietin+SCF and erythropoietin+SCF, respectively. VPA was as potent as FK228. In cultures with granulocyte-macrophage colony-stimulating factor+SCF, where CD61(-)GPA(+) erythroid precursors were mostly developed, VPA mainly enhanced the generation of CD61(-)GPA(+) erythroid precursors. In serum-containing cultures, only low numbers of CD61(+) or GPA(+) cells were developed with IL-3+SCF. Nevertheless, a substantial number of these cells were generated with VPA. Furthermore, these stimulating effects of VPA were observed by incubating CD34(+) cells from patients with myelodysplastic syndrome. Quantitative reverse transcription polymerase chain reaction showed that VPA enhanced GATA-2, but not GATA-1, messenger RNA expression with IL-3+SCF. These results indicate a novel role for VPA in enhancing the potential of IL-3 to stimulate megakaryopoiesis as well as erythropoiesis and suggest a new therapeutic approach of epigenetic therapy for hematological disease.

Evaluation of Potential role for Valproic Acid in IL-3-Mediated Megakaryopoiesis and Erythropoiesis in Serum-Free and Serum-Containing Cultures.

Abstract 2746Poster Board II-722Although attention has been paid to the antitumor activity of histone deacetylase (HDAC) inhibitors in hematologic disease, a role for HDAC in normal hematopoiesis has not been clearly defined. Previous study have shown that the potent HDAC inhibitor FK228 (romidepsin, depsipeptide) stimulates IL-3-mediated erythropoiesis in serum-free cultures. Here, we precisely examined the effects of well-tolerated antiepileptic drug valproic acid (VPA) on IL-3-mediated megakaryopoiesis and erythropoiesis in serum-free and serum-containing cultures. After incubation of CD34+ cells in serum-free medium containing IL-3+SCF, CD61+GPA− megakaryocytic, a CD61+GPA+ mixture of megakaryocytic and erythroid, and CD61−GPA+ erythroid precursors were generated. Pharmacological concentration of VPA (100 μg/ml) and FK228 (0.45 ng/ml) remarkably increased the number of CD61+GPA+ cells by 7-fold and 9-fold, respectively. Other populations were also increased by FK228 and VPA. VPA and FK228 enhanced the generation of megakaryocytic and erythroid precursors from more mature CD34+ cell-derived CD36+ erythroid and megakaryocytic precursors. Thus, VPA was found to be as potent as FK228 in stimulating the IL-3-mediated megakaryopoiesis and erythropoiesis. In the presence of GM-CSF+SCF, CD61−GPA+ erythroid precursors were mostly developed. Addition of VPA to the cultures mainly promoted the generation of CD61−GPA+ erythroid precursors, while the generation of megakaryocytic precursors was also moderately enhanced. In serum-containing cultures, there were only low numbers of CD61+ or GPA+ cells detected even in the presence of IL-3+SCF. Nevertheless, addition of VPA to the cultures containing IL-3+SCF increased the numbers of CD61+GPA−, CD61+GPA+, and CD61−GPA+ cells by 3-fold, 18-fold, and 4-fold, respectively from three independent experiments. In megakaryopoiesis and erythropoiesis, GATA-1 and GATA-2 are shown to play important roles in the proliferation and differentiation process, respectively. By quantitative RT-PCR analysis, after incubation of CD34+ cells with IL-3+SCF, GATA-2 m-RNA expression was increased at day1 but returned to initial levels at day3. VPA increased the expression level of GATA-2 gene by 1.6-fold and 1.7-fold at day1 and day3, respectively. While GATA-1 gene expression was remarkably elevated at day1 and day3, its expression was not affected by VPA. Our data reveal a potential for VPA to promote the ability of IL-3 to stimulate megakaryopoiesis and erythropoiesis in serum-free and serum-containing cultures and thus implicate a novel therapeutic approach of epigenetic therapy for treatment of hematologic disease such as myelodysplastic syndrome. Disclosures:No relevant conflicts of interest to declare.

Synthesis and Conformation−Activity Relationships of the Peptide Isosteres of FK228 and Largazole

The peptide isosteres (10 and 11) of the naturally occurring and potent histone deacetylase (HDAC) inhibitors FK228 and largazole have been synthesized and evaluated side-by-side with FK228, largazole, and SAHA for inhibition of the class I HDACs 1, 2, 3, and 6.

Induction of autophagy in malignant rhabdoid tumor cells by the histone deacetylase inhibitor FK228 through AIF translocation

Malignant rhabdoid tumors (MRT) exhibit a very poor prognosis because of their resistance to chemotherapeutic agents and new therapies are needed for the treatment of this cancer. Here, we show that the histone deacetylase (HDAC) inhibitor FK228 (depsipeptide) has an antitumor effect on MRT cells both in vitro and in vivo. FK228 is a unique cyclic peptide and is among the most potent inhibitors of both Class I and Class II HDACs. FK228 inhibited proliferation and induced apoptosis in all MRT cell lines tested. Preincubation with the pancaspase inhibitor zVAD-fmk did not completely rescue FK228-induced cell death, although it did inhibit apoptosis. Transmission electron microscopy (TEM) showed that FK228 could stimulate MRT cells to undergo apoptosis, necrosis or autophagy. FK228 converted unconjugated microtubule-associated protein light chain 3 (LC3-I) to conjugated light chain 3 (LC3-II) and induced localization of LC3 to autophagosomes. Apoptosis inducing factor (AIF), which plays a role in caspase-independent cell death, translocated to the nucleus in response to FK228 treatment. Moreover, small interfering RNA (siRNA) targeting of AIF prevented the morphological changes associated with autophagy and redistribution of LC3 to autophagosomes. Disrupting autophagy with chloroquine treatment enhanced FK228-induced cell death. In vivo, FK228 caused a reduction in tumor size and induced autophagy in tumor tissues. Using immunoelectron microscopy, we confirmed AIF translocation into the nucleus of FK228-induced autophagic cells in vivo. Thus, FK228 is a novel candidate for an antitumor agent for MRT cells.

Histone deacetylase inhibitor FK228 enhances adenovirus-mediated p53 family gene therapy in cancer models

Therapeutic replacement of the wild-type p53 gene has been pursued as a potential gene therapy strategy in a variety of cancer types; however, some cancer models are resistant to p53 in vivo and in vitro. Therefore, to improve p53 gene therapy, it is important to overcome the resistance to p53-mediated apoptosis. Histone deacetylase inhibitors are a novel class of chemotherapeutic agents that are able to reverse the malignant phenotype of transformed cells. A natural histone deacetylase inhibitor, FK228, is reported to enhance adenovirus infection due in part to the up-regulation of coxsackievirus adenovirus receptor expression. In this study, preclinical experiments were done to establish a mechanistic rationale for the combination of adenovirus-mediated p53 family gene transfer and FK228 pretreatment in future clinical trials. Pretreatment with FK228 enhanced apoptosis in human cancer cells through enhanced transduction of Ad-p53. FK228 also induced hyperacetylation of the p53 protein and specifically enhanced p53-mediated Noxa expression. Additionally, the combination of FK228 and Ad-p53 induced Bax translocation to the mitochondria. The double knockdown of Bax and Noxa expression by small interfering RNA antagonized the synergistic effect of Ad-p53 and FK228 on apoptosis induction. In human cancer xenograft models, FK228 significantly increased the therapeutic effectiveness of p53 as well as p63 gene therapy. These results provide a strong rationale for combining p53 gene therapy and FK228 pretreatment in cancer therapy.

Improved Total Synthesis of the Potent HDAC Inhibitor FK228 (FR-901228)

A scaleable synthesis of the potent histone deacetylase (HDAC) inhibitor FK228 is described. A reliable strategy for preparing the key beta-hydroxy mercapto heptenoic acid partner was accomplished in nine steps and 13% overall yield. A Noyori asymmetric hydrogen-transfer reaction established the hydroxyl stereochemistry in >99:1 er via the reduction of a propargylic ketone.

Gene expression profiling induced by histone deacetylase inhibitor, FK228, in human esophageal squamous cancer cells

Histone deacetylase inhibitors (HDACIs) are promising therapeutic agents with the potential for regulating cell cycle, differentiation and apoptosis in cancer cells. HDACI activity is associated with selective transcriptional regulation and altering gene expression. However, the exact mechanisms leading to the antitumor effect of HDACIs are not fully understood. FK228, one of the powerful HDACIs, strongly inhibited cell growth of T.Tn and TE2 cells and induced apoptosis. Therefore, comprehensive analysis of the changes in gene expression in human esophageal cancer cell lines by the HDACI FK228 was carried out by microarray analysis. This analysis was used to clarify the expression profiles of genes after exposure to FK228. Of the 4,608 genes analyzed, 93 genes in T.Tn and 65 genes in TE2 were up- or down-regulated 2-fold or more at least at one time point during FK228 exposure and they were classified into four clusters based on their expression patterns. Among them, 15 genes were contained in both cell lines and their expression patterns were similar. Except p21, Prdx1 (reported by us) and IGFBP3, the behaviour/expression of 12 highly responsive genes has still not been reported in esophageal cancer cells. These observations of the expression patterns of functionally classified genes provided insights into the mechanism of the antitumor effect of FK228 in esophageal squamous carcinoma.

Cyclic disulfides as functional mimics of the histone deacetylase inhibitor FK-228

FK-228 is a potent histone deacetylase (HDAC) inhibitor with tremendous therapeutic potential against a wide array of human cancers. We describe the development of analogs that share FK-228’s novel mechanism of activation and HDAC inhibition.

The use of histone deacetylase inhibitor FK228 and DNA hypomethylation agent 5‐azacytidine in human bladder cancer therapy

The long-term disease-free survival in patients with metastatic transitional cell carcinoma (TCC) is still considerably low. Novel chemotherapeutic agents are needed to decrease the morbidity and mortality of TCC. In this study, we have evaluated several epigenetic modifiers for their therapeutic application in bladder cancer. Both histone deacetylase inhibitors (FK228, TSA) and DNA hypomethylating agent (5-Azacytidine) were tested using in vitro assays such as cell viability, cell cycle analysis and western blot to determine their mechanisms of action. Drug combination experiments were also designed to study any additive or synergistic effects of these agents. In addition, two bladder cancer xenograft models (one subcutaneous and one orthotopic) were employed to assess the therapeutic efficacy of these agents in vivo. Three agents exhibited various growth inhibitory effects on 5 different TCC cell lines in a dose- and time-dependent manner. In addition to G2/M cell cycle arrest, FK228 is more potent in inducting apoptosis than the two other single agents, and combination of both FK228 and 5-Aza further enhances this effect. p21 induction is closely associated with FK228 or TSA but not 5-Aza, which is mediated via p53-independent pathway. Consistent with in vitro results, FK228 exhibited a significant in vivo growth inhibition of TCC tumor in both subcutaneous and orthotopic xenograft models. FK228 is a potent chemotherapeutic agent for TCC in vivo with minimal undesirable side effects. The elevated p21 level mediated via p53 independent pathway is a hallmark of FK228 mechanism of action.

A Histone Deacetylase Inhibitor Enhances Adenoviral Infection of Renal Cancer Cells

Coxsackie and adenovirus receptor is a high affinity receptor for adenovirus type 5. To our knowledge the expression profile of coxsackie and adenovirus receptor in renal cancer has not been described. We evaluated the expression of coxsackie and adenovirus receptor in human renal cancer specimens and determined whether the histone deacetylase inhibitor FK-228 (Astelas Pharmaceutical, Osaka, Japan) increases the efficiency of adenoviral infections in renal carcinoma cells in vivo and in vitro. We used randomly selected renal cancer specimens. Specimens were analyzed for coxsackie and adenovirus receptor expression using reverse transcriptase-polymerase chain reaction and immunohistochemistry. In vitro experiments on cytotoxicity were performed to determine a nontoxic dose of FK-228 for renal cancer cells. The level of coxsackie and adenovirus receptor expression was determined by fluorescence activated cell scanning and/or reverse transcriptase-polymerase chain reaction in FK-228 treated renal cancer cells. The effect in vivo on adenoviral gene expression was investigated in athymic mice. In several human renal cancer specimens a loss of or decreased coxsackie and adenovirus receptor expression was detected by reverse transcriptase-polymerase chain reaction based analysis and immunohistochemistry. The nontoxic dose of FK-228 for renal carcinoma cells was 0.5 ng/ml. Treatment of cancer cells with 0.5 ng/ml FK-228 increased levels of coxsackie and adenovirus receptor RNA and acetylated histone H3. This increase was associated with an approximately 10-fold increase in adenoviral infection, as evidenced by increased transgene expression from a beta-galactosidase containing adenoviral vector. Intravenous administration of FK-228 enhanced coxsackie and adenovirus receptor expression in athymic mice. The combination of beta-galactosidase adenovirus and FK-228 was significantly more effective than adenovirus only in A498 cells 3 weeks after treatment in vivo. The combination of p21 adenovirus and FK-228 resulted in significant tumor inhibition in vitro and in vivo. In human renal cancer specimens a loss of or decrease in coxsackie and adenovirus receptor expression may be an early event in renal cancer progression. Pretreatment with FK-228 may increase tumor cell sensitivity to adenoviral gene therapy vectors.

The histone deacetylase inhibitor FK228 given prior to adenovirus infection can boost infection in melanoma xenograft model systems

A major limitation of adenovirus type 5-mediated cancer gene therapy is the inefficient infection of many cancer cells. Previously, we showed that treatment with low doses of the histone deacetylase inhibitor FK228 (FR901228, depsipeptide) increased coxsackie adenovirus receptor (CAR) levels, histone H3 acetylation, and adenovirus infection efficiencies as measured by viral transgene expression in cancer cell lines but not in cultured normal cells. To evaluate FK228 in vivo, the effects of FK228 therapy in athymic mice bearing LOX IMVI or UACC-62 human melanoma xenografts were examined. Groups of mice were treated with FK228 using several dosing schedules and the differences between treated and control animals were determined. In mice with LOX IMVI xenografts (n = 6), maximum CAR induction was observed 24 h following a single FK228 dose of 3.6 mg/kg with a 13.6 +/- 4.3-fold (mean +/- SD) increase in human CAR mRNA as determined by semiquantitative reverse transcription-PCR analysis. By comparison, mouse CAR levels in liver, kidney, and lung from the same animals showed little to no change. Maximum CAR protein induction of 9.2 +/- 4.8-fold was achieved with these treatment conditions and was associated with increased histone H3 acetylation. Adenovirus carrying a green fluorescent protein (GFP) transgene (2 x 10(9) viral particles) was injected into the xenografts and GFP mRNA levels were determined. A 7.4 +/- 5.2-fold increase in GFP mRNA was found 24 h following adenovirus injection into optimally FK228-treated mice (n = 10). A 4-fold increase in GFP protein-positive cells was found following FK228 treatment. These studies suggest that FK228 treatment prior to adenovirus infection could increase the efficiency of adenovirus gene therapy in xenograft model systems.

The Histone Deacetylase Inhibitor FK228 Distinctly Sensitizes the Human Leukemia Cells to Retinoic Acid‐Induced Differentiation

FK228 (depsipeptide) is a novel histone deacetylase inhibitor (HDACI) that has shown therapeutical efficacy in clinical trials for malignant lymphoma. In this article, we examined in vitro effects of FK228 on human leukemia cell lines, NB4 and HL-60. FK228 alone (0.2-1 ng/mL) inhibited leukemia cell growth in a dose-dependent manner and induced death by apoptosis. FK228 had selective differentiating effects on two cell lines when used for 6 h before induction of granulocytic differentiation by retinoic acid (RA) or in combination with RA. These effects were accompanied by a time- and dose-dependent histone H4 hyper-acetylation or histone H3 dephosphorylation and alterations in DNA binding of NF-kappaB in association with cell death and differentiation. Pifithrin-alpha (PFT), an inhibitor of p53 transcriptional activity, protected only NB4 cells with functional p53 from FK228-induced apoptosis and did not interfere with antiproliferative activity in p53-negative HL-60 cells. In NB4 cells, PFT inhibited p53 binding to the p21 (Waf1/Cip1) promotor and induced DNA binding of NF-kappaB leading to enhanced cell survival. Thus, beneficial effects of FK228 on human promyelocytic leukemia may be exerted through the induction of differentiation or apoptosis via histone modification and selective involvement of transcription factors, such as NF-kappaB and p53.

Mechanism of Increased Coxsackie and Adenovirus Receptor Gene Expression and Adenovirus Uptake by Phytoestrogen and Histone Deacetylase Inhibitor in Human Bladder Cancer Cells and the Potential Clinical Application

Coxsackie and adenovirus receptor (CAR) is known as a principal receptor for adenovirus commonly used as a gene delivery vector. Down-regulation of CAR is often detected in several cancer types. Epigenetic modifiers such as histone deacetylase inhibitor FK228 (depsipeptide) have been shown to increase CAR expression as well as the uptake of adenovirus in bladder cancer in vivo and in vitro, indicating that altered transcriptional regulation of CAR is the key mechanism responsible for the decreased CAR levels in this cancer. In this study, we screened agents that could induce CAR expression in bladder cancer cells. Fifty-eight drugs with various chemical properties were tested. Ipriflavone and plant isoflavones were found to exhibit the ability to induce CAR gene expression in combination with FK228. Genistein, the natural isoflavone found in soybean, when combined with FK228, exerts a synergistic effect on CAR gene and protein expression in bladder cancer cells. Chromatin immunoprecipitation results showed an increased histone acetylation in the CAR promoter gene, which is due to the suppression of histone deacetylase activity by both agents. Also, our data indicated that combination treatment is a potent chemotherapeutic regimen for bladder cancer cells and the subsequent administration of recombinant adenovirus could further eliminate the remaining cells. Taken together, our results provide a strong rationale for combining chemotherapeutic and gene therapeutic agents to enhance the therapeutic efficacy in bladder cancer.