Ability Of Histone Deacetylase Inhibitors Research Articles

HDACi Delivery Systems Based on Cellulose Valproate Nanoparticles.

The ability of histone deacetylase inhibitors (HDACi) like valproic acid (VPA) as a therapeutic for inflammatory diseases or cancer has increased the interest in HDACi and their targeted transport to diseased tissues. Administration of VPA immobilized on polymeric carriers was found to be a suitable approach to circumvent drawbacks such as rapid metabolization, short serum half-life, or side effects. Polysaccharides are convenient biopolymeric carriers due to their biocompatibility and biodegradability. Furthermore, the hydroxy-, amino-, or carboxylic groups are predestinated for functionalization. The esterification of three hydroxy groups of cellulose with VPA leads to products having a high amount of VPA loading. Subsequent shaping yielded uniform nanoparticles (NPs) of around 150nm in size capable of releasing VPA in a controlled way under physiological conditions.

Abstract 562: Novel combination therapy for treating TNBC using LIFR and HDAC Inhibitors

Abstract Background: Triple-negative breast cancer (TNBC) lacks targeted therapies and represents a disproportional share of the breast cancer (BC) mortality rate. TNBC exhibits autocrine stimulation of the LIF/LIFR axis and overexpression of LIF is associated with poorer relapse-free survival in BC patients. Histone deacetylase inhibitors (HDACIs) are emerging as promising multifunctional agents in TNBC to elicit cytotoxic actions. Recent studies have shown that cancer cells elicit feedback activation of leukemia inhibitory factor receptor (LIFR) which in turn curtails response to HDACIs. We developed a first-in-class inhibitor of LIFR, EC359 that directly interacts with LIFR and effectively blocks LIFR downstream signaling. The objective of this study is to examine the therapeutic efficacy of combination therapy using preclinical and patient-derived xenograft (PDX) models. Methods: We tested utility of combination therapy using multiple HDACIs that are currently in clinical trails along with EC359. The effect of combination therapy was evaluated using MTT, invasion, colony formation, and Caspase3/7 assays. Mechanistic studies were performed using Western blotting, qRT-PCR, and STAT3 reporter assays. The efficacy of combination therapy in vivo was examined using xenograft, PDX, and patient-derived explant (PDEx) models. Results: Immunohistochemical analyses of breast tumors using tissue microarrays revealed significant expression of LIFR in TNBC tissues. Treatment of TNBC model cells with four different HDACIs increased the expression of LIFR. LIFR inhibitor EC359 at nM concentration is additive to HDACIs in reducing cell viability. Knockdown of LIFR or treatment with EC359 significantly enhanced the efficacy of HDACIs in reducing the cell viability, colony formation ability, and invasiveness as well as promoted apoptosis compared to monotherapy in TNBC model cells. On the contrary, treatment with STAT3 inhibitor requires µM concentrations to reduce the cell viability of TNBC cells and is not additive to HDACIs. Mechanistic studies utilizing STAT3 reporter gene assays and biochemical studies using multiple TNBC model cells exhibited activation of the LIFR signaling pathway upon HDACIs treatment but was attenuated by EC359 therapy. Treatment of human TNBC utilizing PDEx assays showed that EC359 enhanced the ability of HDACIs to decrease proliferation (Ki-67 positivity) compared to monotherapy. Using TNBC xenografts and PDX models, we demonstrated that EC359 treatment enhanced the ability of HDACIs to reduce in vivo tumor growth compared to monotherapy. Conclusions: Our results suggest that the combination therapy of HDACIs and EC359 provides therapeutic utility in overcoming the limitation of feedback activation of LIFR observed in the treatment of HDACIs in treating TNBC. Supported by DOD BCRP grant W81XWH-18-1-0016 (R.K. Vadlamudi; K.J. Nickisch) Citation Format: Suryavathi Viswanadhapalli, Mengxing Li, Bindu Santhamma, Uday P. Pratap, Yiliao Luo, Junhao Liu, Kristin A. Altwegg, Xiaonan Li, Ahmed Gulzar, Hui Yan, Zhenming Xu, Andrew Brenner, Gangadhara R. Sareddy, Manjeet K. Rao, Rajeshwar R. Tekmal, Hareesh B. Nair, Klaus J. Nickisch, Ratna K. Vadlamudi. Novel combination therapy for treating TNBC using LIFR and HDAC Inhibitors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 562.

Abstract P3-11-08: Targeting LIFR enhances the activity of HDAC inhibitors for the treatment of triple negative breast cancer

Abstract Background: Triple-negative breast cancer (TNBC) is a heterogeneous disease. TNBC lacks targeted therapies and represents a disproportional share of the breast cancer (BC) mortality rate. Histone deacetylase inhibitors (HDACIs) are emerging as promising multifunctional agents in TNBC to elicit cytotoxic actions. Recent studies have shown that cancer cells elucidate feedback activation of leukemia inhibitory factor receptor (LIFR) which in turn curtails response to HDACIs. We developed a first-in-class inhibitor of LIFR, EC359 that directly interacts with LIFR and effectively blocks LIFR downstream signaling. Here, we examined whether the novel LIFR inhibitor, EC359, has the ability to counteract negative effects of LIFR signaling to enhance HDACIs therapeutic efficacy in the treatment of TNBC. Methods: We tested multiple HDACIs currently in clinical trials including vorinostat, panobinostat, romidepsin, and givinostat using multiple TNBC models. The effect of combination therapy of HDACIs and EC359 on TNBC cell viability and invasion was examined using MTT assays and matrigel invasion assays respectively. The efficacy of combination therapy on cell survival and apoptosis was determined using clonogenic assays and Caspase 3/7 assays, respectively. Mechanistic studies were performed using Western blotting, qRT-PCR, and reporter gene assays. The efficacy of combination therapy in vivo was examined using Xenograft, patient-derived xenograft (PDX), and patient-derived explant (PDEX) models. Results: We demonstrated that the treatment of TNBC models with HDACIs increased the expression of LIFR. Immunohistochemistry analyses of breast tumors using tissue microarrays revealed significant expression of LIFR in TNBC samples. Knockdown of LIFR or treatment with a small molecule inhibitor of LIFR (EC359) significantly enhanced the efficacy of HDACIs in reducing cell viability, colony formation ability, and invasiveness as well as promoted apoptosis compared to monotherapy of HDACIs or EC359 in TNBC cell lines. Mechanistic studies, reporter gene assays and biochemical studies using multiple TNBC models exhibited activation of the LIFR signaling pathway upon HDACIs treatment but was attenuated by EC359+HDACI combination therapy. Treatment of human breast tumors utilizing PDEX assays showed that EC359 enhanced the ability of HDACIs to decrease the proliferation (Ki-67 positivity) compared to monotherapy. Furthermore, using TNBC xenografts and PDX models, we demonstrated that EC359 treatment enhanced the ability of HDACIs to reduce in vivo tumor growth compared to monotherapy. Conclusions: Our results suggest that the combination therapy of HDACIs and EC359 provides greater therapeutic efficacy than monotherapy. In addition, treatment with EC359 can overcome the feedback activation of LIFR currently observed in the treatment of TNBC with HDACIs. Citation Format: Suryavathi Viswanadhapalli, Mengxing Li, Bindu Santhamma, Uday P Pratap, Yiliao Luo, Junhao Liu, Kristin A Altwegg, Xiaonan Li, Hui Yan, Zhenming Xu, Andrew Brenner, Gangadhara R Sareddy, Rajeshwar R Tekmal, Hareesh B Nair, Klaus J Nickisch, Ratna K Vadlamudi. Targeting LIFR enhances the activity of HDAC inhibitors for the treatment of triple negative breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-11-08.

Energy metabolism regulated by HDAC inhibitor attenuates cardiac injury in hemorrhagic rat model.

A disturbance of energy metabolism reduces cardiac function in acute severe hemorrhagic patients. Alternatively, adequate energy supply reduces heart failure and increases survival. However, the approach to regulating energy metabolism conductive to vital organs is limited, and the underlying molecular mechanism remains unknown. This study assesses the ability of histone deacetylase inhibitors (HDACIs) to preserve cardiac energy metabolism during lethal hemorrhagic injury. In the lethally hemorrhagic rat and hypoxic myocardial cells, energy metabolism and heart function were well maintained following HDACI treatment, as evident by continuous ATP production with normal cardiac contraction. Valproic acid (VPA) regulated the energy metabolism of hemorrhagic heart by reducing lactate synthesis and protecting the mitochondrial ultrastructure and respiration, which were attributable to the inhibition of lactate dehydrogenase A activity and the increased myeloid cell leukemia-1 (mcl-1) gene expression, ultimately facilitating ATP production and consumption. MCL-1, the key target of VPA, mediated this cardioprotective effect under acute severe hemorrhage conditions. Our results suggest that HDACIs promote cardioprotection by improving energy metabolism during hemorrhagic injury and could therefore be an effective strategy to counteract this process in the clinical setting.

Abstract B108: The HDAC inhibitor HBI-8000 enhances immunotherapy with either PD-1 or PD-L1 blockade in the MC38 model of colon cancer

Abstract Immunomodulatory antibodies targeting the immune checkpoint receptors CTLA-4, PD-1 and its ligand PD-L1, have resulted in significantly improved clinical benefits over the standard of care in many cancer types. While these immune checkpoint inhibitors have successfully exploited the adaptive immune system to produce remarkable clinical responses in various cancers, a significant number of patient's tumors are either innately resistant or develop resistance, and the disease eventually progresses. For this reason, rational drug combinations with checkpoint inhibitors and other immunomodulating agents are imperative to improve the rate of durable responses and patient survival. Histone deacetylase inhibitors (HDACi) have been successful as monotherapy for hematologic malignancies, but their clinical effectiveness against solid tumors has been limited to date. The long-held belief that HDACi are immunosuppressive has been challenged recently by data demonstrating the ability of HDACi to enhance anti-tumor immunity through effects on tumor immunogenicity, regulatory T cells, myeloid-derived suppressor cells (MDSCs), as well as effector cell functions. HBI-8000 (chidamide) is a novel, orally bioavailable Class I (HDAC 1,2,3) and Class II (HDAC 10) selective HDACi with a demonstrated positive effects on antitumor immunity, enhancing the activity of CTL and NK cells, as well as having direct activity against tumor cells through reversal of apoptosis resistance. We report here that HBI-8000 enhances the activity of both PD-1 and PD-L1 blocking antibody (Ab) in the MC38 syngeneic mouse model of colon cancer. Combinations of HBI-8000 with PD-1 or PD-L1 Ab resulted in statistically significant decreases in tumor progression and increases in survival compared to single agent therapy. Analysis of tumor infiltrating lymphocytes (TIL) revealed a significant increase in the percentage of intratumoral CD8+ T cells in tumors treated with both HBI-8000/PD-1 Ab and HBI-8000/PD-L1 Ab combinations. The TIL analysis also revealed a trend towards lower percentages of Tregs and granulocytic MDSCs. To evaluate the potential role of this combination as a 2nd line treatment option, i.e., in subjects failing 1st line checkpoint antibody therapy, we developed a model of immune checkpoint antibody failure, where tumor-bearing mice were initially treated (1st line) with either PD-1 or PD-L1 blocking Ab. Mice which had either slow disease progression or stable disease followed by progression, were randomized into one of six 2nd line treatment groups, including combinations of anti PD-1 or PD-L1 blocking Ab with HBI-8000. Fifty percent of mice failing 1st line PD-1 Ab treatment experienced a complete response, and were rescued by treatment with HBI-8000 combined with PD-L1 Ab. Altogether our data suggest that the addition of the HDACi HBI-8000 can improve the anti-tumor response to either PD-1 or PD-L1 blocking antibodies, increase the percentage of intratumoral immune effector cells and potentially counter innate resistance to checkpoint inhibitors. Our data also suggests that combination therapy with HBI-8000 and a checkpoint inhibitor can rescue tumor-bearing mice that have failed 1st line therapy with different checkpoint inhibitor. These results provide a strong rationale for the evaluation of therapeutic regimens utilizing PD-L1 or PD-1 blocking antibodies in combination with HBI-8000. Citation Format: Reid P. Bissonnette, Alain Rolland, Bob Goodeneow, Mireille Gillings. The HDAC inhibitor HBI-8000 enhances immunotherapy with either PD-1 or PD-L1 blockade in the MC38 model of colon cancer [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr B108.

Abstract 4478: EGFR tyrosine kinase inhibitors overcome resistance to chemotherapy in malignant pleural mesothelioma

Abstract Background: Malignant pleural mesothelioma (MPM) is a cancer of the pleura mainly caused by exposure to asbestos fibers. Current treatments are unsatisfactory due to intrinsic chemoresistance of the tumor. We hypothesized that chemoresistance was due to epigenetic errors and evaluated the ability of HDAC inhibitors to improve treatment efficacy. We previously showed that valproic acid (VPA) improves the first line regimen of MPM both in vitro and in vivo (Vandermeers et al, 2009, Clinical Cancer Research 15: 2818). A clinical trial also demonstrated that VPA in combination with doxorubicin increases the response rate of second line patients (Scherpereel et al, 2011, European Respiratory Journal 37:129). Methods: Transcriptomic profiling was performed by microarray analyses (Agilent). Gene expression was validated by quantitative RT-qPCR. Modulation of TGFα expression was performed by shRNA interference and transfection of a cDNA vector. Onset of apoptosis was assessed with the Annexin V assay. Results: To evaluate the mechanisms associated with the response to chemotherapy, we compared two types of MPM cell lines (M14K and H28) characterized by a difference in sensitivity to doxorubicin+VPA. Microarray analyses and bioinformatic modeling of gene expression profiles revealed the most relevant candidate genes associated with sensitivity or resistance to this regimen. Among these, TGFα expression was associated with resistance to doxorubicin + VPA in a series of MPM cell lines. Silencing of TGFα by RNA interference in H28 cells correlated with a significant increase in apoptosis. On the other hand, overexpression of TGFα desensitized M14K cells to doxorubicin+VPA -induced apoptosis. Since TGFα interacts with the EGF receptor, we evaluated pharmacological inhibition using EGFR tyrosine kinase inhibitors (erlotinib and gefitinib) and the dual HDAC/EGFR inhibitor CUDC-101. As predicted, these TKI inhibitors improved efficacy of doxorubicin+VPA. Conclusions: Our data demonstrate that TGFα is involved in resistance of MPM to chemotherapy and that TKI inhibitors overcome resistance to second line regimen. Citation Format: Bernard Staumont, Chrisostome Costa, Fabian Vandermeers, Sathya Neelature Sriramareddy, Céline Mascaux, Arnaud Scherpereel, Bernard Duysinx, Renaud Louis, Philippe Delvenne, Pascale Hubert, Luc Willems. EGFR tyrosine kinase inhibitors overcome resistance to chemotherapy in malignant pleural mesothelioma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4478.

Histone deacetylase inhibitors: a potential epigenetic treatment for Duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD) is a life-threatening genetic disease that currently has no available cure. A number of pharmacological strategies that aim to target events downstream of the genetic defect are currently under clinical investigation, and some of these are outlined in this report. In particular, we focus on the ability of histone deacetylase inhibitors to promote muscle regeneration and prevent the fibro-adipogenic degeneration of dystrophic mice. We describe the rationale behind the translation of histone deacetylase inhibitors into a clinical approach, which inspired the first clinical trial with an epigenetic drug as a potential therapeutic option for DMD patients.

Abstract 643: The histone deacetylase inhibitor Quisinostat augments the anti-tumor reponses of T-cells: Implications in adoptive cell therapy

Abstract It has become increasingly clear that histone deacetylases (HDACs), a family of epigenetic modifiers, play intimate roles in both tumor and immune biology. Indeed, two HDAC inhibitors (HDACi) are FDA approved for the treatment of cutaneous T-cell leukemia, and various others are currently undergoing clinical trials for the treatment of both solid and hematological malignancies. Beyond direct anti-tumor effects, HDACi have shown pronounced abilities to augment the immunogenicity of tumor cells leading to an improved ant-tumor immune response. Furthermore, in addition to anti-tumor effects, several studies have demonstrated a profound ability of HDACi to tip the scale between tolerance and inflammation in antigen presenting cells, leading to enhanced T-cell activation. However, less well studied is the ability of HDACi to directly influence the function and fate of T-cells. Here we report that the HDACi JNJ-264-81585 (Quisinostat) is able to augment the pro-inflammatory phenotype of T-cells in vitro and in vivo. Quisinostat is a hydroxamic acid with potent sub-nanomolar inhibition of several HDACs, and reported anti-tumor activity. Here we report that Quisinostat has a potent HDAC inhibition in T-cells, with sub-nanomolar doses increasing histone 3 acetylation levels in a dose dependent manner. Intriguingly, when treated with Quisinostat in vitro, activated murine CD4+ and CD8+ T-cells produced significantly higher levels of the pro-inflammatory cytokines IL-2, IFN-g, and TNF. Concomitantly, treated T-cells produced decreased levels of IL-6 and IL-17. To determine the efficacy of Quisinostat at augmenting T-cell function in vivo, a novel T-cell adoptive transfer model was utilized. In this model syngeneic T-cells from B6.SJL mice were stained with the proliferation tracking dye CellTrace™ Violet and activated in the presence of Quisinostat, then subsequently adoptively transferred into sub-lethally irradiated C57BL/6 recipient mice. Analysis of proliferation of transferred T-cells showed that CD8+ T-cells treated with Quisinostat had significantly higher rates of proliferation than those treated with DMSO control. As well, in a result similar to that seen in vitro, adoptively transferred T-cells had skewing towards a predominantly CD8+ composition. Finally, T-cells treated with Quisinostat displayed a reconstitution advantage over DMSO treated cells, with higher percentages of transferred T-cells relative to endogenous T-cells. Collectively, these results demonstrate a profound and important ability of HDAC inhibition to modulate the T-cell response, highlighting a role of HDACi, particularly Quisinostat, in augmenting the efficacy of adoptive cell therapy, giving rationale for clinical investigation. Citation Format: David M. Woods, Andressa L. Sodre, Jason B. Brayer, Eduardo M. Sotomayor. The histone deacetylase inhibitor Quisinostat augments the anti-tumor reponses of T-cells: Implications in adoptive cell therapy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 643. doi:10.1158/1538-7445.AM2014-643

Abstract 1725: HDAC inhibition induces Bim expression and apoptosis in breast cancer cells undergoing paclitaxel or antiestrogen treatment.

Abstract Paclitaxel functions by preventing microtubule degradation, leading to mitotic arrest and apoptotic death. Of particular interest, paclitaxel-induced death in breast cancer cells is dependent, in part, on the levels of BimEL, a pro-apoptotic member of the Bcl-2 family of proteins. In addition, our recent studies demonstrated that BimEL is required for 4-hydroxytamoxifen-induced apoptosis of estrogen receptor positive (ER+) MCF-7 breast cancer cells [Breast Cancer Res. 2012 Mar 19;14(2):R52]. In contrast, we demonstrated low-level BimEL expression in ER+ T47D breast cancer cells that do not undergo antiestrogen-induced apoptosis. Thus, low-level BimEL expression in ER+ breast cancer may predict a poor apoptotic threshold which ultimately would facilitate the development of acqured resistance to paclitaxel, as well as antiestrogen therapy. Based on the ability of HDAC inhibitors to increase the transcription of pro-apoptotic genes, we hypothesized that the HDAC inhibitor suberoylanilide hydroxamic acid (SAHA) would increase BimEL expression in T47D breast cancer cells and induce a robust apoptotic response to paclitaxel chemotherapy and antiestrogen treatment. In this study, we now demonstrate that SAHA does significantly up-regulate BimEL expression in T47D cells, as well as in MCF-7 cells. Concomitant with BimEL upregulation, SAHA sensitizes T47D and MCF-7 cells to paclitaxel-induced apoptosis. Similarly, SAHA sensitizes T-47D cells to antiestrogen-induced apoptosis, while augmenting the level of antiestrogen-induced apoptosis in MCF-7 cells. These studies indicate that the pro-apoptotic protein BimEL is required for SAHA-induced sensitization of breast cancer cells to paclitaxel and/or antiestrogen-induced apoptosis. Currently, siRNA studies are being conducted to determine if BimEL is a key death effector in response to SAHA treatment and if the increased death from SAHA and paclitaxel or SAHA and antiestrogens is synergistic or additive. Our results provide strong support for the use of HDAC inhibitors when designing novel combination therapies to reduce the emergence of acquired resistance in breast cancer cells undergoing chemo- or antihormonal therapy. Acknowledgement: this work was supported by teh MCG foundation and NIHRO1 CA121438 to P.V.S. Citation Format: Aric Berning, Alexander Eason, Nathan Gilley, Suchreet Takhar, Sally ElShafey, Muthusamy Thangaraju, Patricia V. Schoenlein. HDAC inhibition induces Bim expression and apoptosis in breast cancer cells undergoing paclitaxel or antiestrogen treatment. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1725. doi:10.1158/1538-7445.AM2013-1725

Synergistic interaction between the novel histone deacetylase inhibitor ST2782 and the proteasome inhibitor bortezomib in platinum-sensitive and resistant ovarian carcinoma cells

The ability of histone deacetylase inhibitors to modulate the expression of genes relevant for growth or apoptotis regulation supports their interest in combination treatments of resistant tumors. We explored the effect of the combination of the histone deacetylase inhibitor ST2782 and the proteasome inhibitor bortezomib in ovarian carcinoma cell lines, including the IGROV-1 cell line and two p53 mutant platinum-resistant sublines (IGROV-1/OHP and IGROV-1/Pt1). We found a synergistic interaction between the two drugs, more evident in the p53-mutant resistant sublines, which was associated with increa sed apoptosis. The treatment with ST2782 resulted in early induction of Bax as well as in cleavage of caspase 3 and poly (ADP-ribose) polymerase only in the resistant cell lines. The inhibition of p53-transcriptional transactivation by pifithrin alpha in IGROV-1 cells enhanced the synergism. Conversely, knockdown of endogenous wild-type p53 in IGROV-1 cells determined synergism reduction. These opposite effects support the relevance of the transactivation-deficient mutant p53 as a synergism determinant. Moreover, in vivo studies indicated that tumor growth inhibition tended to be more evident in mice receiving the drug combination than in those treated with bortezomib alone. Overall, our study supports the potential effectiveness of the combination in platinum drug-resistant ovarian cancer carrying mutant p53.

Abstract C34: Synergistic interaction between a novel histone deacetylase inhibitor and the proteasome inhibitor bortezomib in platinum-resistant ovarian carcinoma cells.

Abstract Based on the ability of histone deacetylase inhibitors to modulate the expression of genes relevant for growth regulatory or apoptotic pathways, the purpose of the present study was to explore the interest of novel combination treatments for drug-resistant tumors. Thus, using cellular and biochemical pharmacology approaches, we examined the effect of the combination between the novel histone deacetylase inhibitor ST2782 and the proteasome inhibitor bortezomib in ovarian carcinoma cell lines, including the parental IGROV-1 cell line and two platinum-resistant sublines. The IGROV-1/OHP and IGROV-1/Pt1 cells, selected for resistance to oxaliplatin and cisplatin respectively, are characterized by a mutant p53 gene. Using the combination index method and cell sensitivity assays, we found a synergistic interaction between ST2782 and bortezomib, more evident in the p53-mutant resistant sublines. Such an interaction was associated with increased apoptotic cell death, as shown by TUNEL assays. The treatment with ST2782 resulted in early induction of the pro-apoptotic protein Bax as well as in cleavage of caspase 3 and PARP only in the resistant cell lines, as supported by Western blot analyses. The inhibition of p53-transcriptional transactivation by pifithrin alpha in IGROV-1 cells enhanced the synergism between the two drugs. Conversely, knockdown of endogenous wild-type p53 in IGROV-1 cells following transfection of small interfering RNAs determined a considerable synergism reduction. These opposite effects support the relevance of the transactivation-deficient mutant p53 as a determinant of the synergism. Moreover, in vivo studies in IGROV-1/Pt1 xenografts indicated that tumor growth inhibition tended to be more marked in mice receiving the drug combination with respect to those treated with bortezomib alone. In conclusion, the present study supports the potential effectiveness of this combination in p53-mutant ovarian cancer models resistant to platinum compounds. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C34.

HDAC Inhibition and Graft Versus Host Disease

Histone deacetylase (HDAC) inhibitors are currently used clinically as anticancer drugs. Recent data have demonstrated that some of these drugs have potent antiinflammatory or immunomodulatory effects at noncytotoxic doses. The immunomodulatory effects have shown potential for therapeutic benefit after allogeneic bone marrow transplantation in several experimental models of graft versus host disease (GVHD). These effects, at least in part, result from the ability of HDAC inhibitors (HDACi) to suppress the function of host antigen presenting cells such as dendritic cells (DC). HDACi reduce the dendritic cell (DC) responses, in part, by enhancing the expression of indoleamine 2,3-dioxygenase (IDO) in a signal transducer and activator of transcription-3 (STAT-3) dependent manner. They also alter the function of other immune cells such as T regulatory cells and natural killer (NK) cells, which also play important roles in the biology of GVHD. Based on these observations, a clinical trial has been launched to evaluate the impact of HDAC inhibitors on clinical GVHD. The experimental, mechanistic studies along with the brief preliminary observations from the ongoing clinical trial are discussed in this review.

Effects of Histone Deacetylase Inhibitors on Modulating H3K4 Methylation Marks - A Novel Cross-Talk Mechanism between Histone-Modifying Enzymes.

A recent study reports that histone deacetylase (HDAC) inhibitors, AR42 and MS- 275, upregulated H3K4 methylation marks in prostate cancer cells, leading to transcriptional activation of genes including those associated with roles in tumor suppression and cell differentiation (1). Evidence suggests that the crosstalk between histone deacetylation and histone H3K4 methylation is attributable to the ability of these HDAC inhibitors to repress the JARID1 family of histone H3 lysine 4 demethylases (H3K4DMs), including RBP2, PLU-1, SMCX, and LSD1, through the downregulation of Sp1 expression. This demonstrates the complexity of the functional roles of HDACs in the regulation of histone modifications as well as the activation of epigenetically silenced gene expression. Equally important is the ability of HDAC inhibitors to transcriptionally suppress H3K4DM gene expression which has therapeutic implications, in that several H3K4DMs such as LSD1 and PLU-1 have been implicated in the pathogenesis of many types of malignancies.

Abstract 3652: HDAC inhibitors activate NF-κB in human leukemia cells through an ATM/NEMO-dependent DNA Damage-related pathway

Abstract The ability of HDAC inhibitors (HDACIs) to induce sustained activation of NF-κB (p65/RelA) has been attributed to reversible RelA acetylation (Chen et al., Science 293:1653-7, 2001), a phenomenon that diminishes HDACI antineoplastic activity (Dai et al., Mol Cell Biol. 25:5429-44, 2005). However, the process by which HDACIs initially activate NF-κB has yet to be elucidated. To address this question, mechanisms underlying HDAC inhibitor (HDACI)-mediated NF-κB activation were investigated in human myeloid leukemia cells. Exposure of U937 and other leukemia cells to the pan-HDACI LBH-589 induced reactive oxygen species (ROS) and p65/RelA activation, the NF-κB-dependent induction of Mn-SOD2 mRNA and protein accompanied by ROS elimination, and sequential induction of XRCC1 (single strand) followed by γ-H2A. X (double strand) DNA breaks. LBH-589 lethality was significantly attenuated by siRNA knockdown of the chromatin-linked DNA damage protein histone H1.2. U937 IκBα super-repressor cells lacking serine 32 and 36 IκBα phosphorylation sites displayed diminished HDACI-mediated NF-κB activation/Mn-SOD2 induction, accompanied by enhanced ROS accumulation, DNA damage, and apoptosis. In contrast, TRAF2 siRNA knockdown blocked TNFα- but not HDACI-mediated NF-κB activation and lethality. The Mn-SOD2 mimetic TBAP prevented HDACI-induced NF-κB activation and nuclear localization, while dramatically attenuating DNA damage and apoptosis. Notably, LBH-589 exposure activated ATM (on serine 1981) and increased its association with NEMO, events comprising a recently described “inside-out” nuclear NF-κB activation pathway (Wu et al., Science 311:1110-1, 2006). Notably, siRNA NEMO or ATM knockdown blocked HDACI-mediated NF-κB nuclear translocation/activation, diminished MnSOD2 induction, and potentiated oxidative injury, DNA damage and cell death. Similarly, SUMOylation-site mutant NEMO (K277A and/or K309A) cells exposed to LBH-589 displayed diminished association of ATM with NEMO, reduced NEMO and p65/RelA nuclear localization/activation, and MnSOD2 down-regulation. These events were accompanied by increased ROS production, γ-H2A. X formation, and enhanced lethality. Collectively, these findings indicate that in human leukemia cells, HDACIs activate the cytoprotective NF-κB pathway through an ATM/NEMO-dependent process involving the induction of ROS and DNA damage. They also raise the possibility that blocking NF-κB activation via the atypical DNA damage-related ATM/NEMO nuclear pathway has the potential to enhance HDACI antileukemic activity. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3652.

Abstract A189: Expression of fusion proteins in acute myeloid leukemia cells increases sensitivity to histone deacetylase inhibitors

Abstract Acute Myeloid Leukemias (AMLs) are often characterized by chromosomal rearrangements that result in fusion proteins with aberrant transcriptional regulatory activities. These fusion proteins bind to gene promoters and recruit corepressors such as histone deacetylases (HDACs), which remodel chromatin into a closed conformation thereby silencing genes and contributing to a malignant phenotype. Aberrantly silenced genes include tumor suppressor and pro-differentiation genes. In addition, multiple groups have reported a DNA repair deficient phenotype concurrent with the expression of different fusion proteins in leukemia. Small molecule HDAC inhibitors (HDACi) were devised as a strategy to reverse transcriptional repression. Indeed, many studies have demonstrated the ability of HDACi to re-sensitize leukemic cells to differentiating stimuli. However, other studies have revealed alternate methods by which HDACi exert anti-tumor activity, including induction of apoptosis that may be dependent on induction of ROS, MAPK signaling etc. We find that low doses of HDACi, including Vorinostat and LBH589, induce cell death in the AML cell line U937 in a dose and time-dependant manner. Further, Vorinostat induced cell death in U937 cells is preceded by DNA damage and a G2/M arrest. This correlates with reports that HDACi repress DNA repair, by down-regulating DNA repair genes and by acetylating repair proteins thereby impairing their repair function. Due to the inhibitory effect of leukemic fusion proteins on DNA repair, we predicted that DNA damage induced by HDACi, and thus cell death, would be amplified in AML cells expressing PML-RARα and PLZF-RARα fusion proteins. Sensitivity to Vorinostat and LBH589 was tested in three U937 derived cell lines: PR9 (PML-RARα inducible), B412 (PLZF-RARα inducible) and SN4 (mock transfected control). Indeed, induction of PLZF-RARα increased sensitivity of B412 cells to both Vorinostat- and LBH-mediated cell death. Assaying for DNA damage using alkaline comet assay, PR9 and B412 cells displayed an increase in DNA damage when their respective fusion protein is expressed. Nonetheless, the contribution of DNA damage to HDACi-mediated cell death remains unclear and further study is necessary. These findings are significant as they point to fusion protein expressing AMLs as a target group that may respond better to HDACi-based therapies. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A189.

Blockade of mTOR Signaling Potentiates the Ability of Histone Deacetylase Inhibitor to Induce Growth Arrest and Differentiation of Acute Myelogenous Leukemia Cells.

This study found that MS-275, a novel synthetic benzamide histone deacetylase inhibitor (HDACI), blocked Akt/mTOR signaling in acute myelogenous leukemia (AML) HL60 and acute promyelocytic leukemia (APL) NB4 cells, as assessed by decreased levels of the phosphorylated (p)-Akt, p-p70 ribosomal S6 kinase (p70S6K), and p-S6K by Western blot analysis. Interestingly, further inactivation of mTOR by rapamycin analogue RAD001 (everolimus) significantly enhanced MS-275-mediated growth inhibition and apoptosis of these cells in parallel with enhanced upregulation of p27 kip1 and downregulation of c-Myc. In addition, RAD001 potentiated the ability of MS-275 to induce differentiation of HL60 and NB4 cells, as measured by expression of CD11b cell surface antigens, as well as reduction of nitroblue tetrazolium. Importantly, RAD001 potentiated the ability of MS-275 to induce expression of the myeloid differentiation-related transcription factor CCAAT enhancer binding protein e in these cells in association with enhanced acetylation of histone H3 on its promoter. Furthermore, RAD001 (5 mg/kg) significantly enhanced the effects of MS-275 (10 mg/kg) to inhibit proliferation of HL60 tumor xenografts in nude mice without adverse effects. Taken together, concomitant administration of a HDACI and a mTOR inhibitor may be a promising treatment strategy for the individuals with a subset of human leukemia.

Blockade of mTOR signaling potentiates the ability of histone deacetylase inhibitor to induce growth arrest and differentiation of acute myelogenous leukemia cells

This study found that MS-275, a novel synthetic benzamide histone deacetylase inhibitor (HDACI), blocked Akt/mammalian target of rapamycin (mTOR) signaling in acute myelogenous leukemia (AML) HL60 and acute promyelocytic leukemia (APL) NB4 cells, as assessed by decreased levels of the phosphorylated (p)-Akt, p-p70 ribosomal S6 kinase (p70S6K) and p-S6K by western blot analysis. Interestingly, further inactivation of mTOR by rapamycin analog RAD001 (everolimus) significantly enhanced MS-275-mediated growth inhibition and apoptosis of these cells in parallel with enhanced upregulation of p27(kip1) and downregulation of c-Myc. In addition, RAD001 potentiated the ability of MS-275 to induce differentiation of HL60 and NB4 cells, as measured by the expression of CD11b cell surface antigens, as well as reduction of nitroblue tetrazolium. Importantly, RAD001 potentiated the ability of MS-275 to induce the expression of the myeloid differentiation-related transcription factor, CCAAT enhancer-binding protein-epsilon, in these cells in association with enhanced acetylation of histone H3 on its promoter. Furthermore, RAD001 (5 mg/kg) significantly enhanced the effects of MS-275 (10 mg/kg) to inhibit proliferation of HL60 tumor xenografts in nude mice without adverse effects. Taken together, concomitant administration of an HDACI and an mTOR inhibitor may be a promising treatment strategy for the individuals with a subset of human leukemia.

Histone deacetylase inhibitors and a functional potent inhibitory effect on human uterine contractility

This study was undertaken to investigate the effects of 3 histone deacetylase inhibitors on human uterine contractility. Biopsy specimens of human myometrium were obtained at elective cesarean section (n = 18). Dissected myometrial strips suspended under isometric conditions, undergoing spontaneous, and oxytocin-induced contractions, were subjected to cumulative additions of 3 histone deacetylase inhibitors: trichostatin A, suberic bishydroxamate (1 nmol/L-10 micromol/L) and valproic acid (100 nmol/L--1 mmol/L). Control experiments were run simultaneously. Integrals of contractile activity were measured by using the PowerLab hardware unit and Chart v3.6 software. Data were analyzed by using 1-way analysis of variance, followed by post hoc analysis. All 3 histone deacetylase inhibitor compounds exerted a potent and cumulative inhibitory effect on spontaneous (n = 18) and oxytocin-induced (n =18) contractility. The mean maximal inhibition values for the 3 compounds were as follows: trichostatin A, 46-54% (P < .05); valproic acid, 35-36% (P < .05); and suberic bishydroxamate, 53-65% (P < .05). The histone deacetylase inhibitors trichostatin A, valproic acid, and suberic bishydroxamate exerted a potent inhibitory effect on human uterine contractions. This raises the possibility that this new class of compounds may have tocolytic potential, in addition to their current clinical indications. We speculate that this inhibitory effect may be linked, at least in part, to the ability of histone deacetylase inhibitors to induce the expression of genes involved in maintaining myometrial quiescence via epigenetic mechanisms but may also potentially involve nonepigenetic pathways.

Bombesin/Gastrin-Releasing Peptide Receptor Antagonists Increase the Ability of Histone Deacetylase Inhibitors to Reduce Lung Cancer Proliferation

The effects of a bombesin/gastrin releasing peptide (BB/GRP) receptor antagonist, PD176252, and histone deacetylase (HDAC) inhibitor, MS-275, were investigated on human lung cancer cell lines. Using the MTT assay, PD176252 and MS-275 inhibited the proliferation of NCI-H1299 cells with IC50 values of 7 and 5 microg/mL, respectively. Using MS-275 and PD176252 together, the ability to inhibit lung cancer cellular growth increased significantly. The combination index for MS-275 and PD176252 was <0.2, indicating that the compounds are highly synergistic in inhibiting lung cancer cellular growth. Also, MS-275 and PD176252 together strongly inhibited the clonal growth of NCI-H345 or NCI-H1299 cells. MS-275 had little effect on the expression of lung cancer cellular GRP or GRP receptors, but increased expression of transforming growth factor-beta receptor II (TGF-beta RII). These results indicate that GRP receptor antagonists may potentiate the action of histone deacetylase inhibitors on lung cancer cellular proliferation by increasing expression of tumor suppressor genes.

Induction of apoptosis of lung and esophageal cancer cells treated with the combination of histone deacetylase inhibitor (trichostatin A) and protein kinase C inhibitor (calphostin C)

Histone deacetylase inhibitors mediate a potent growth-inhibitory effect in cancer cells through induction of cell-cycle arrest and apoptosis. Moreover, these agents significantly induce transcriptional activation of nuclear factor kappaB, as well as p21 regulated by protein kinase C, and are thought to negatively influence the ability of histone deacetylase inhibitor to effectively mediate apoptosis. This study aimed to evaluate the effect of calphostin C (a protein kinase C inhibitor) on trichostatin A (a histone deacetylase inhibitor)-mediated upregulation of nuclear factor kappaB and p21 promotor transcriptional activity, as well as induction of apoptosis in lung and esophageal cancer cells. Cultured lung and esophageal cancer cells were treated with calphostin C and trichostatin A. Nuclear factor kappaB transcriptional activity was quantitated by using the nuclear factor kappaB-luciferase assay. Transcription of p21 gene and p21 protein levels was evaluated by using the p21 promoter-luciferase assay and the p21 enzyme-linked immunoassay, respectively. Apoptosis was evaluated by using the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-based ApoBrdU assay. Levels of expression of nuclear factor kappaB-dependent antiapoptotic and proapoptotic proteins were evaluated by means of Western blotting. Exposure of lung or esophageal cancer cells to trichostatin A resulted in a dose- and cell-dependent 2-fold to greater than 20-fold increase of nuclear factor kappaB and p21 transcriptional activity. Treatment with trichostatin A and calphostin C led to a 50% to 90% decrease of trichostatin A- mediated upregulation of nuclear factor kappaB and p21 activation. Inhibition of nuclear factor kappaB activity resulted in significant reduction (30% to >99%) of trichostatin A- mediated activation of not only nuclear factor kappaB transcription but also p21 promotor activity. Importantly, 90% to 96% of thoracic cancer cells under-went apoptosis after exposure to the combination of trichostatin A plus calphostin C. Inhibition of protein kinase C abrogates trichostatin A-mediated upregulation of nuclear factor kappaB transcriptional activity and p21 expression that is associated with profound induction of apoptosis in lung or esophageal cancer cells. Protein kinase C might be a novel target for enhancing the efficacy of histone deacetylase inhibitor in cancer therapy.