The Experts below are selected from a list of 1965 Experts worldwide ranked by ideXlab platform

Bolin Liu - One of the best experts on this subject based on the ideXlab platform.

  • cladribine in combination with Entinostat synergistically elicits anti proliferative anti survival effects on multiple myeloma cells
    Cell Cycle, 2018
    Co-Authors: Hui Lyu, Bolun Wang, Shanshan Pei, Deye Song, Bolin Liu
    Abstract:

    ABSTRACTCladribine (2CdA), a synthetic purine analog interfering with DNA synthesis, is a medication used to treat hairy cell leukemia (HCL) and B-cell chronic lymphocytic leukemia. Entinostat, a selective class I histone deacetylase (HDAC) inhibitor, shows antitumor activity in various human cancers, including hematological malignancies. The therapeutic potential of cladribine and Entinostat against multiple myeloma (MM) remains unclear. Here we investigate the combinatorial effects of cladribine and Entinostat within the range of their clinical achievable concentrations on MM cells. While either agent alone inhibited MM cell proliferation in a dose-dependent manner, their combinations synergistically induced anti-proliferative/anti-survival effects on all MM cell lines (RPMI8226, U266, and MM1.R) tested. Further studies showed that the combinations of cladribine and Entinostat as compared to either agent alone more potently induced mitotic catastrophe in the MM cells, and resulted in a marked increase o...

  • Cladribine in combination with Entinostat synergistically elicits anti-proliferative/anti-survival effects on multiple myeloma cells.
    Cell cycle (Georgetown Tex.), 2018
    Co-Authors: Bolun Wang, Hui Lyu, Shanshan Pei, Deye Song, Bolin Liu
    Abstract:

    ABSTRACTCladribine (2CdA), a synthetic purine analog interfering with DNA synthesis, is a medication used to treat hairy cell leukemia (HCL) and B-cell chronic lymphocytic leukemia. Entinostat, a selective class I histone deacetylase (HDAC) inhibitor, shows antitumor activity in various human cancers, including hematological malignancies. The therapeutic potential of cladribine and Entinostat against multiple myeloma (MM) remains unclear. Here we investigate the combinatorial effects of cladribine and Entinostat within the range of their clinical achievable concentrations on MM cells. While either agent alone inhibited MM cell proliferation in a dose-dependent manner, their combinations synergistically induced anti-proliferative/anti-survival effects on all MM cell lines (RPMI8226, U266, and MM1.R) tested. Further studies showed that the combinations of cladribine and Entinostat as compared to either agent alone more potently induced mitotic catastrophe in the MM cells, and resulted in a marked increase o...

  • Cladribine in combination with Entinostat synergistically elicits anti-proliferative/anti-survival effects on multiple myeloma cells
    2018
    Co-Authors: Bolun Wang, Hui Lyu, Shanshan Pei, Deye Song, Bolin Liu
    Abstract:

    Cladribine (2CdA), a synthetic purine analog interfering with DNA synthesis, is a medication used to treat hairy cell leukemia (HCL) and B-cell chronic lymphocytic leukemia. Entinostat, a selective class I histone deacetylase (HDAC) inhibitor, shows antitumor activity in various human cancers, including hematological malignancies. The therapeutic potential of cladribine and Entinostat against multiple myeloma (MM) remains unclear. Here we investigate the combinatorial effects of cladribine and Entinostat within the range of their clinical achievable concentrations on MM cells. While either agent alone inhibited MM cell proliferation in a dose-dependent manner, their combinations synergistically induced anti-proliferative/anti-survival effects on all MM cell lines (RPMI8226, U266, and MM1.R) tested. Further studies showed that the combinations of cladribine and Entinostat as compared to either agent alone more potently induced mitotic catastrophe in the MM cells, and resulted in a marked increase of the cells at G1 phase associated with decrease of Cyclin D1 and E2F-1 expression and upregulation of p21waf−1. Apoptotic ELISA and western blot analyses revealed that the combinations of cladribine and Entinostat exerted a much more profound activity to induce apoptosis and DNA damage response, evidenced by enhanced phosphorylation of histone H2A.X and the DNA repair enzymes Chk1 and Chk2. Collectively, our data demonstrate that the combinations of cladribine and Entinostat exhibit potent activity to induce anti-proliferative/anti-survival effects on MM cells via induction of cell cycle G1 arrest, apoptosis, and DNA damage response. Regimens consisting of cladribine and/or Entinostat may offer a new treatment option for patients with MM. Abbreviations: MM, multiple myeloma; HCL, hairy cell leukemia; HDAC, histone deacetylase; Ab, antibody; mAb, monoclonal Ab; FBS, fetal bovine serum; CI, combination index; PAGE, polyacrylamide gel electrophoresis; ELISA, enzyme-linked immunosorbent assay; PARP, poly(ADP-ribose) polymerase; MTS, 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium,inner salt

  • Functional cooperation of miR-125a, miR-125b, and miR-205 in Entinostat-induced downregulation of erbB2/erbB3 and apoptosis in breast cancer cells
    Cell death & disease, 2013
    Co-Authors: Shuiliang Wang, Jingcao Huang, Hui Lyu, Choon-kee Lee, Jieqiong Tan, Jinhan Wang, Bolin Liu
    Abstract:

    We reported that the class I HDAC inhibitor Entinostat induced apoptosis in erbB2-overexpressing breast cancer cells via downregulation of erbB2 and erbB3. Here, we study the molecular mechanism by which Entinostat dual-targets erbB2/erbB3. Treatment with Entinostat had no effect on erbB2/erbB3 mRNA, suggesting a transcription-independent mechanism. Entinostat decreased endogenous but not exogenous erbB2/erbB3, indicating it did not alter their protein stability. We hypothesized that Entinostat might inhibit erbB2/erbB3 protein translation via specific miRNAs. Indeed, Entinostat significantly upregulated miR-125a, miR-125b, and miR-205, that have been reported to target erbB2 and/or erbB3. Specific inhibitors were then used to determine whether these miRNAs had a causal role in Entinostat-induced downregulation of erbB2/erbB3 and apoptosis. Transfection with a single inhibitor dramatically abrogated Entinostat induction of miR-125a, miR-125b, or miR-205; however, none of the inhibitors blocked Entinostat action on erbB2/erbB3. In contrast, co-transfection with two inhibitors not only reduced their corresponding miRNAs, but also significantly abrogated Entinostat-mediated reduction of erbB2/erbB3. Moreover, simultaneous inhibition of two, but not one miRNA significantly attenuated Entinostat-induced apoptosis. Interestingly, although the other HDAC inhibitors, such as SAHA and panobinostat, exhibited activity as potent as Entinostat to induce growth inhibition and apoptosis in erbB2-overexpressing breast cancer cells, they had no significant effects on the three miRNAs. Instead, both SAHA- and panobinostat-decreased erbB2/erbB3 expression correlated with the reduction of their mRNA levels. Collectively, we demonstrate that Entinostat specifically induces expression of miR-125a, miR-125b, and miR-205, which act in concert to downregulate erbB2/erbB3 in breast cancer cells. Our data suggest that epigenetic regulation via miRNA-dependent or -independent mechanisms may represent a novel approach to treat breast cancer patients with erbB2-overexpressing tumors.

  • functional cooperation of mir 125a mir 125b and mir 205 in Entinostat induced downregulation of erbb2 erbb3 and apoptosis in breast cancer cells
    Cell Death and Disease, 2013
    Co-Authors: Shuiliang Wang, Jingcao Huang, Hui Lyu, Choon-kee Lee, Jieqiong Tan, Jinhan Wang, Bolin Liu
    Abstract:

    We reported that the class I HDAC inhibitor Entinostat induced apoptosis in erbB2-overexpressing breast cancer cells via downregulation of erbB2 and erbB3. Here, we study the molecular mechanism by which Entinostat dual-targets erbB2/erbB3. Treatment with Entinostat had no effect on erbB2/erbB3 mRNA, suggesting a transcription-independent mechanism. Entinostat decreased endogenous but not exogenous erbB2/erbB3, indicating it did not alter their protein stability. We hypothesized that Entinostat might inhibit erbB2/erbB3 protein translation via specific miRNAs. Indeed, Entinostat significantly upregulated miR-125a, miR-125b, and miR-205, that have been reported to target erbB2 and/or erbB3. Specific inhibitors were then used to determine whether these miRNAs had a causal role in Entinostat-induced downregulation of erbB2/erbB3 and apoptosis. Transfection with a single inhibitor dramatically abrogated Entinostat induction of miR-125a, miR-125b, or miR-205; however, none of the inhibitors blocked Entinostat action on erbB2/erbB3. In contrast, co-transfection with two inhibitors not only reduced their corresponding miRNAs, but also significantly abrogated Entinostat-mediated reduction of erbB2/erbB3. Moreover, simultaneous inhibition of two, but not one miRNA significantly attenuated Entinostat-induced apoptosis. Interestingly, although the other HDAC inhibitors, such as SAHA and panobinostat, exhibited activity as potent as Entinostat to induce growth inhibition and apoptosis in erbB2-overexpressing breast cancer cells, they had no significant effects on the three miRNAs. Instead, both SAHA- and panobinostat-decreased erbB2/erbB3 expression correlated with the reduction of their mRNA levels. Collectively, we demonstrate that Entinostat specifically induces expression of miR-125a, miR-125b, and miR-205, which act in concert to downregulate erbB2/erbB3 in breast cancer cells. Our data suggest that epigenetic regulation via miRNA-dependent or -independent mechanisms may represent a novel approach to treat breast cancer patients with erbB2-overexpressing tumors.

Roberto Pili - One of the best experts on this subject based on the ideXlab platform.

  • immunomodulation by Entinostat in renal cell carcinoma patients receiving high dose interleukin 2 a multicenter single arm phase i ii trial nci ctep 7870
    Clinical Cancer Research, 2017
    Co-Authors: Roberto Pili, Li Shen, Ashley Orillion, David I Quinn, Hans J Hammers, Paul J Monk, Saby George, Tanya B Dorff, Thomas Olencki, Dominick Lamonica
    Abstract:

    Purpose: Based on preclinical data suggesting that the class I selective HDAC inhibitor Entinostat exerts a synergistic antitumor effect in combination with high dose interleukin 2 (IL-2) in a renal cell carcinoma model by down-regulating Foxp3 expression and function of regulatory T cells (Treg), we conducted a phase I/II clinical study with Entinostat and high dose IL-2 in patients with metastatic clear cell renal cell carcinoma (ccRCC). Experimental Design: Clear cell histology, no prior treatments, and being sufficiently fit to receive high dose IL-2 were the main eligibility criteria. The phase I portion consisted of two dose levels of Entinostat (3 and 5 mg, PO every14 days) and a fixed standard dose of IL-2 (600,000 units/kg IV). Each course was 85 days. The primary end point was objective response rate and toxicity. Secondary end points included progression-free survival and overall survival. Results: 47 patients were enrolled. At a median follow-up of 21.9 months, the objective response rate was 37% (95% CI 22%-53%), the median progression-free survival was 13.8 months (95% CI 6.0-18.8), and the median overall survival was 65.3 months (95% CI 52.6.-65.3). The most common grade 3/4 toxicities were hypophosphatemia (16%), lymphopenia (15%), and hypocalcemia (7%), and all were transient. Decreased Treg were observed following treatment with Entinostat, and lower numbers were associated with response (p=0.03). Conclusions: This trial suggests a promising clinical activity for Entinostat in combination with high dose Il-2 in ccRCC patients, and provides the first example of an epigenetic agent being rationally combined with immunotherapy.

  • Abstract 4906: The selective class I HDAC inhibitor Entinostat enhances the antitumor effect of PD-1 inhibition in a syngeneic orthotopic murine model of renal cell carcinoma
    Immunology, 2016
    Co-Authors: Ashley Orillion, Li Shen, Sreevani Arisa, Sreenivasulu Chintala, Remi Adelaiye-ogala, May Elbanna, Roberto Pili
    Abstract:

    Background: Recent advances in immunotherapy have highlighted the antitumor effects of immune checkpoint inhibition. Novel anti-PD-1/PD-L1 immunotherapies have been shown to effectively overcome tumor avoidance of immune surveillance in several tumor types including renal cell carcinoma. Our group has recently shown that the selective class I HDAC inhibitor Entinostat is effective in suppressing regulatory T cells and enhancing immunotherapies in murine renal and prostate models, RENCA and Myc-Cap respectively. In this study we have evaluated the combination of Entinostat with an anti-PD-1 antibody in the RENCA renal cell carcinoma model. Methods: 32 BALB/c female mice were implanted with the syngenic, orthotopic, renal cell carcinoma mouse model, RENCA - luciferase tagged - at day -8. Treatment (8 mice /group) with anti-mouse-PD-1 (aPD-1; 10mg/kg twice a week, I.P.), Entinostat (5mg/kg 5 days a week), or combination of the two was begun at day 1. Bioluminescence imaging was performed at days -1, 9 and 19 to assess the orthotopic tumor growth. End point tumor weights were taken to assess the effect of combination treatment. Results: Analysis of tumor growth showed a reduction of bioluminescence across the three time points in the combination group as compared to the vehicle and single agent treatments. Additionally, end point analysis of tumor weights revealed an overall reduction in the size of the tumors in the Entinostat/anti-mPD-1 combination group (88% inhibition) as compared to the vehicle (p = 0.0002), aPD-1 alone (25% inhibition)(p = 0.0181), and Entinostat alone (63% inhibition)(p = 0.0481) groups. Examination of the status of the infiltrating immune cells of the tumor microenvironment via flow cytometry, qRT-PCR, immunohistochemistry, and/or immunofluorescence analysis is ongoing. Conclusions: Our preliminary results suggest that the immunomodulatory activity of the selective class I HDAC inhibitor Entinostat may enhance the antitumor effect of PD-1/PD-L1 inhibition and provide the rationale for the clinical testing of this novel combination in patients with RCC. Citation Format: Ashley R. Orillion, Li Shen, Remi Adelaiye-Ogala, May Elbanna, Sreenivasulu Chintala, Sreevani Arisa, Roberto Pili. The selective class I HDAC inhibitor Entinostat enhances the antitumor effect of PD-1 inhibition in a syngeneic orthotopic murine model of renal cell carcinoma. [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 4906.

  • immunomodulation by hdac inhibition results from a phase ii study with Entinostat and high dose interleukin 2 in renal cell carcinoma patients ctep 7870
    Journal of Clinical Oncology, 2016
    Co-Authors: Roberto Pili, Li Shen, David I Quinn, Hans J Hammers, Saby George, Tanya B Dorff, Thomas Olencki, Paul Monk, Alan D Hutson, Richard Piekarz
    Abstract:

    500 Background: Immunosuppressive factors such as regulatory T cells (Tregs) and myeloid-derived suppressive cells (MDSCs) limit the efficacy of immunotherapies. Histone deacetylase (HDAC) inhibitors have been shown to have immunomodulatory effects. We have previously reported that the class I HDAC inhibitor Entinostat has synergistic antitumor effects in combination with high dose interleukin-2 (IL-2) in a renal cell carcinoma model by down-regulating Foxp3 expression and function of Tregs. Thus, we have conducted a Phase I/II clinical study with Entinostat and high dose IL-2 in patients (pts) with metastatic clear cell renal cell carcinoma. Methods: The primary objectives were to evaluate the safety, tolerability and efficacy of this combination strategy. The main eligibility criteria were clear cell histology and being fit to receive high dose IL-2. The phase I portion consisted of two dose levels of Entinostat (3 and 5 mg, PO every14 days) and a fixed dose of IL-2 (600,000 units/kg every 8 hrs). To te...

  • Phase I study of high-dose interleukin 2, aldesleukin, in combination with the histone deacetylase inhibitor, Entinostat, in patients with metastatic renal cell carcinoma: Safety and tolerability results.
    Journal of Clinical Oncology, 2013
    Co-Authors: Roberto Pili, Li Shen, Hans J Hammers, Saby George, Anita Sandecki, Connie Collins, Michael A. Carducci
    Abstract:

    369 Background: Immunosuppressive factors such as regulatory T cells (Tregs) limit the efficacy of immunotherapies. Histone deacetylase (HDAC) inhibitors have been shown to have anti-tumor activity in different malignancies and to induce immuno-modulatory effects. We have previously reported that a class I selective HDAC inhibitor, Entinostat, has synergistic anti-tumor effects in combination with high dose interleukin-2 (IL-2) in a renal cell carcinoma model (Kato Y, et al. Clinical Cancer Res 2007). Our group has also recently shown that low dose Entinostat induces STAT3 acetylation, down-regulates Foxp3 expression in Tregs, and blocks Tregs suppressive function without affecting T effector cells (Shen Li, et al. PLoSONE 2012). Methods: Based on these preclinical evidences, we have initiated a Phase I/II clinical study with Entinostat and high dose IL-2 in patients (pts) with metastatic renal cell carcinoma. The primary objective of the phase I portion was to evaluate the safety and tolerability of this...

  • Phase I/II study of high-dose interleukin 2, aldesleukin, in combination with the histone deacetylase inhibitor Entinostat in patients with metastatic renal cell carcinoma.
    Journal of Clinical Oncology, 2012
    Co-Authors: Roberto Pili, Li Shen, Hans J Hammers, Saby George, Anita Sandecki, Connie Collins, Igor Espinoza-delgado, Michael A. Carducci
    Abstract:

    TPS4687 Background: Immunosuppressive factors such as regulatory T cells (Tregs) limit the efficacy of immunotherapies. Histone deacetylase (HDAC) inhibitors have been shown to have anti-tumor activity in different malignancies and to induce immuno-modulatory effects. We have previously reported that a class I specific HDAC inhibitor, Entinostat, has synergistic anti-tumor effect in combination with high dose interleukin-2 (IL-2) in a renal cell carcinoma model (Kato Y et al Clinical Cancer Res 2007). Our group has also recently showed that low dose Entinostat induces STAT3 acetylation, down-regulates Foxp3 expression in Tregs, and blocks Tregs suppressive function without affecting T effector cells (Shen Li et al PLoSONE 2012). Methods: Based on these preclinical evidences we have initiated a Phase I/II clinical study with Entinostat and high dose IL-2 in patients with metastatic renal cell carcinoma. The primary objective of the study is to evaluate the safety, tolerability and efficacy of this combinat...

Peter Ordentlich - One of the best experts on this subject based on the ideXlab platform.

  • Abstract 2146: Activity of Entinostat alone and in combination with cisplatin in a panel of low passage adenoid cystic carcinoma patient-derived xenograft (PDX) models
    Tumor Biology, 2018
    Co-Authors: Amanda Mangold, Peter Ordentlich, Rogerio M. Castilho, Melissa Rundle, Nicole Spardy Burr, Alyssa Moriarty, Priscila H. Goncalves, Jeffrey Kaufman, Kyriakos P. Papadopoulos, Michael J. Wick
    Abstract:

    Background: Adenoid Cystic Carcinoma (ACC) is a rare cancer of secretory glands, most typically occurring in the salivary glands. No approved standard of care exists for systemic therapy. To identify potentially useful therapies, we screened Food and Drug Administration (FDA)-approved and investigational therapies using a well characterized panel of low passage ACC PDX models. Based on these results, combination treatments were evaluated for additive or super-additive effects. In line with the clinical chemo resistance observed in ACC patients, we previously reported that ACC tumor models are insensitive to platinum therapies. Interestingly, histone deacetylase (HDAC) inhibitors have been shown to sensitize cancer cells to anti-cancer agents in vitro. Entinostat is an oral class 1 selective HDAC inhibitor in Phase 3 testing for ER+ breast cancer in combination with hormone therapy. To better understand the potential effects of Entinostat in ACC, we evaluated this agent alone and in combination with cisplatin in ACC PDX tumor models. Methods: Low passage ACC models were established in immune-deficient mice from primary or metastatic patient tissue and confirmed by histologic comparative analysis. Drug sensitivity studies evaluating Entinostat, cisplatin and the combination were performed in three models, including ACCx5M1, ACCx6 and ACCx9. Study endpoints included tumor volume and time from treatment initiation with tumor growth inhibition, delay and regression reported at study completion. Results: Entinostat, cisplatin and the combination were all well tolerated with minimum cycle-based weight loss. Cisplatin tested alone (3 mg/kg weekly) was similar to control in all models, while single agent Entinostat (5 mg/kg daily) showed significant anti-tumor activity in the ACCx5M1 (p Conclusion: Our studies identify Entinostat as an agent of potential benefit in treating ACC and demonstrate that Entinostat can induce low-dose cisplatin activity in the ACCx9 model, which harbors a mutation in the NOTCH1 gene that has been linked with chemo resistance and worse prognosis. Genomic and other characterization methods are currently underway to correlate sensitivity and resistance between models. Citation Format: Amanda Mangold, Melissa Rundle, Nicole Spardy Burr, Alyssa Moriarty, Priscila Goncalves, Rogerio Castilho, Peter Ordentlich, Jeffrey Kaufman, Kyriakos Papadopoulos, Michael J. Wick. Activity of Entinostat alone and in combination with cisplatin in a panel of low passage adenoid cystic carcinoma patient-derived xenograft (PDX) models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2146.

  • Abstract 1740: Epigenetic reprogramming of the tumor microenvironment by Entinostat increases tumor sensitivity to multivalent immunotherapy combinations with an IL-15 superagonist plus vaccine or immune checkpoint blockade
    Immunology, 2018
    Co-Authors: Kristin C. Hicks, Peter Ordentlich, Karin M. Knudson, Frank R. Jones, Shahrooz Rabizadeh, Hing C. Wong, James W. Hodge, Jeffrey Schlom, Sofia R. Gameiro
    Abstract:

    The clinical promise of cancer immunotherapy relies on the immune system recognizing and eliminating tumor cells identified as non-self. However, the tumor microenvironment (TME) can greatly impede a tumor targeted immune response via increasing immunosuppressive cells or hampering T and NK cell maturation, recruitment, and function through numerous pathways, including upregulation of immune checkpoints such as PD-L1. Hence, there is an unmet clinical need to develop effective therapeutic strategies that can reprogram the TME to restore tumor immune recognition and reverse immune evasion. We recently demonstrated that Entinostat, a class I histone deacetylase (HDAC) inhibitor, reverses tumor immune escape to T cell-mediated lysis. We hypothesize that the immune-mediated tumor elimination promoted by the IL-15/IL-15Rα superagonist ALT803 in combination with PD-L1 checkpoint blockade or a therapeutic adenoviral vaccine targeting CEA (Ad-CEA) will be augmented by the epigenetic reprograming of the TME induced by Entinostat. In preclinical studies, ALT803 has been shown to exhibit potent antitumor activity in multiple murine models of cancer through the expansion of NK and CD8+ T cells with high effector function. Here, we demonstrate that Entinostat increased extracellular expression of immune-relevant proteins on murine colon and breast carcinoma cells in vitro. Additionally, the frequency of T cells with an activated phenotype were increased in non-tumor bearing mice. In the MC38-CEA murine model of colon carcinoma, the addition of Entinostat augmented the antitumor activity promoted by ALT803 plus Ad-CEA resulting in increased survival. Furthermore, in the 4T1 murine model of triple-negative breast cancer, the combination of Entinostat with ALT803 and a monoclonal antibody targeting PD-L1 significantly reduced primary tumor weight relative to ALT803 plus anti-PD-L1 therapy and resulted in a significant reduction of the number of 4T1 tumor-forming cells in the lung. The immune mechanism associated with antitumor efficacy of these multivalent therapies was examined in both the periphery and TME. Overall, these studies provide a rationale for combining Entinostat with multivalent immunotherapy combinations, including cytokines, antibodies targeting PD-L1, and therapeutic cancer vaccines. Citation Format: Kristin C. Hicks, Karin M. Knudson, Frank R. Jones, Peter Ordentlich, Shahrooz Rabizadeh, Hing C. Wong, James W. Hodge, Jeffrey Schlom, Sofia R. Gameiro. Epigenetic reprogramming of the tumor microenvironment by Entinostat increases tumor sensitivity to multivalent immunotherapy combinations with an IL-15 superagonist plus vaccine or immune checkpoint blockade [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1740.

  • Entinostat neutralizes myeloid derived suppressor cells and enhances the antitumor effect of pd 1 inhibition in murine models of lung and renal cell carcinoma
    Clinical Cancer Research, 2017
    Co-Authors: Ayumi Hashimoto, Li Shen, Ashley Orillion, Nur P Damayanti, Remi Adelaiyeogala, Sreevani Arisa, Sreenivasulu Chintala, Peter Ordentlich
    Abstract:

    Purpose: Recent advances in immunotherapy highlight the antitumor effects of immune- checkpoint inhibition despite a relatively limited subset of patients receiving clinical benefit. The selective class I histone deacetylase inhibitor (HDACi) Entinostat has been reported to have immunomodulatory activity including targeting of immune suppressor cells in the tumor microenvironment. Thus, we decided to assess whether Entinostat could enhance anti-PD-1 treatment and investigate those alterations in the immunosuppressive tumor microenvironment that contribute to the combined anti-tumor activity. Experimental design: We utilized syngeneic mouse models of lung (LLC) and renal cell (RENCA) carcinoma, and assessed immune correlates, tumor growth and survival following treatment with Entinostat (5 or 10 mg/kg, P.O.) and a PD-1 inhibitor (10 and 20 mg/kg, s.c.). Results: Entinostat enhanced the antitumor effect of PD-1 inhibition in two syngeneic mouse tumor models by reducing tumor growth and increasing survival. Entinostat inhibited the immunosuppressive function of both PMN- and M-MDSC populations. Analysis of MDSC response to Entinostat revealed significantly reduced arginase-1, iNOS and COX-2 levels, suggesting potential mechanisms for the altered function. We also observed significant alterations in cytokine/chemokine release in vivo with a shift towards a tumor suppressive microenvironment. Conclusions: Our results demonstrate that Entinostat enhances the antitumor effect of PD-1 targeting through functional inhibition of MDSCs, and a transition away from an immune suppressive tumor microenvironment. These data provide a mechanistic rationale for the clinical testing and potential markers of response of this novel combination in solid tumor patients.

  • histone deacetylase inhibitor enhances the efficacy of mek inhibitor through noxa mediated mcl1 degradation in triple negative and inflammatory breast cancer
    Clinical Cancer Research, 2017
    Co-Authors: Angie M Torresadorno, Peter Ordentlich, Bora Lim, J S Lee, Takahiro Kogawa, Debu Tripathy, Naoto T. Ueno
    Abstract:

    Purpose: Inflammatory breast cancer (IBC), diagnosed clinically, and triple-negative breast cancer (TNBC), diagnosed by molecular receptor status, are the two most aggressive forms of breast cancer, and both lack effective targeted therapies. We previously demonstrated involvement of histone deacetylase (HDAC) inhibitor Entinostat in regulating apoptosis in IBC and TNBC cells; here, we aimed to identify novel combination therapy candidates. Experimental Design: Potential therapeutic targets were identified by mRNA expression profiling of TNBC and IBC cells treated with Entinostat. Drug action and synergism were assessed by in vitro proliferation assays, tumor growth in vivo , and proteomic analyses. Gain/loss-of-expression studies were utilized to functionally validate the role of identified targets in sensitivity of TNBC and IBC cells to combination therapy. Results: Entinostat induced activity of the oncogenic ERK pathway and expression of proapoptotic NOXA. These are known to stabilize and degrade, respectively, MCL1, an antiapoptotic Bcl-2 protein. In breast cancer patients, high-MCL1/low-NOXA tumor expression correlated significantly with poor survival outcomes. Combination treatment of Entinostat with MEK inhibitor pimasertib reduced the growth of TNBC and IBC cells in vitro and inhibited tumor growth in vivo . The synergistic action of combination therapy was observed in TNBC and IBC cell lines in which NOXA expression was induced following Entinostat treatment. The therapeutic activity depended on induction of mitochondrial cell death pathways initiated by NOXA-mediated MCL1 degradation. Conclusions: Our preclinical findings provide a rationale for the clinical testing of combination HDAC and MEK pathway inhibition for TNBC and IBC that exhibit elevated baseline tumor MCL1 expression. Clin Cancer Res; 1–13. ©2017 AACR.

  • Abstract 5595: HDAC inhibitor Entinostat disrupts function of PMN-MDSC
    Immunology, 2017
    Co-Authors: Ayumi Hashimoto, Peter Ordentlich, Vinit Kumar, Dmitry I. Gabrilovich
    Abstract:

    Myeloid-derived suppressor cells (MDSCs), consisting of subpopulations of polymorphonuclear (PMN; CD11b+Ly6G+Ly6Clo) and monocytic (M; CD11b+Ly6G-Ly6Chi) MDSCs play a major role as immune suppressors in cancer. MDSC-targeted therapy has not been developed yet. Histone deacetylases (HDAC) are critically involved in epigenetic regulation of multiple genes and may regulate MDSC number and function. The purpose of this study was to evaluate the effect of the class I HDAC inhibitor, Entinostat on differentiation and function of MDSCs in mouse tumor models of lung cancer (Lewis Lung Carcinoma, LLC) and colon cancer (CT26). LLC and CT26 tumor-bearing mice were treated with Entinostat (10 mg/kg, p.o. daily for two weeks). Entinostat caused significant increase in the presence of CD45+ CD11b+ myeloid cells in bone marrow, spleen and tumors. This increase was largely due to accumulation of Ly6ClowLy6G+ PMN. Unexpectedly, this was associated with a small decrease in the presence of common myeloid progenitor (CMP) and granulocyte-macrophage progenitor (GMP) cells in bone marrow. This suggests that Entinostat affects differentiation of PMN downstream of GMP. Experiments in vitro demonstrated that Entinostat increased differentiation of enriched hematopoietic progenitor cells (HPC) to PMN in the presence of tumor explant supernatant (TES), which supported the in vivo result. To assess the effect of Entinostat on the function of PMN-MDSCs, Ly6G+ cells were purified from spleen and tumor of LLC tumor-bearing mice treated with Entinostat or vehicle alone and tested for their ability to suppress antigen-specific T cell. As expected Ly6G+ PMN-MDSC from tumor-bearing mice treated with vehicle alone had strong suppressive activity. In contrast, Ly6G+ cells from spleen and tumor of Entinostat-treated LLC tumor-bearing mice show significantly reduced suppressive activity. This result was confirmed in experiments with Ly6G+ cells differentiated from HPC culture with/without Entinostat treatment. To determine whether Entinostat inhibition of PMN-MDSC immunosuppressive function could enhance immune checkpoint activity, Entinostat combined with an anti-PD-1 antibody was evaluated using the LLC tumor-bearing mice. These mice were treated with Entinostat (10 mg/kg, p.o., daily) and anti-mouse PD-1 rat antibody (10 mg/kg, i.p., twice a week). Entinostat or PD-1 antibody alone did not significantly inhibit the tumor growth. In striking contrast, the combination treatment blocked tumor progression. Our data demonstrate that Entinostat increases a population of PMN-MDSCs that are no longer immunosuppressive leading to enhanced anti-tumor activity when combined with an immune checkpoint inhibitor. This novel phenomenon provides further rationale for combination therapy of Entinostat with anti-PD-1 antibody or other checkpoint inhibitors in clinical settings. Citation Format: Ayumi Hashimoto, Vinit Kumar, Peter Ordentlich, Dmitry I. Gabrilovich. HDAC inhibitor Entinostat disrupts function of PMN-MDSC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5595. doi:10.1158/1538-7445.AM2017-5595

Hui Lyu - One of the best experts on this subject based on the ideXlab platform.

  • cladribine in combination with Entinostat synergistically elicits anti proliferative anti survival effects on multiple myeloma cells
    Cell Cycle, 2018
    Co-Authors: Hui Lyu, Bolun Wang, Shanshan Pei, Deye Song, Bolin Liu
    Abstract:

    ABSTRACTCladribine (2CdA), a synthetic purine analog interfering with DNA synthesis, is a medication used to treat hairy cell leukemia (HCL) and B-cell chronic lymphocytic leukemia. Entinostat, a selective class I histone deacetylase (HDAC) inhibitor, shows antitumor activity in various human cancers, including hematological malignancies. The therapeutic potential of cladribine and Entinostat against multiple myeloma (MM) remains unclear. Here we investigate the combinatorial effects of cladribine and Entinostat within the range of their clinical achievable concentrations on MM cells. While either agent alone inhibited MM cell proliferation in a dose-dependent manner, their combinations synergistically induced anti-proliferative/anti-survival effects on all MM cell lines (RPMI8226, U266, and MM1.R) tested. Further studies showed that the combinations of cladribine and Entinostat as compared to either agent alone more potently induced mitotic catastrophe in the MM cells, and resulted in a marked increase o...

  • Cladribine in combination with Entinostat synergistically elicits anti-proliferative/anti-survival effects on multiple myeloma cells.
    Cell cycle (Georgetown Tex.), 2018
    Co-Authors: Bolun Wang, Hui Lyu, Shanshan Pei, Deye Song, Bolin Liu
    Abstract:

    ABSTRACTCladribine (2CdA), a synthetic purine analog interfering with DNA synthesis, is a medication used to treat hairy cell leukemia (HCL) and B-cell chronic lymphocytic leukemia. Entinostat, a selective class I histone deacetylase (HDAC) inhibitor, shows antitumor activity in various human cancers, including hematological malignancies. The therapeutic potential of cladribine and Entinostat against multiple myeloma (MM) remains unclear. Here we investigate the combinatorial effects of cladribine and Entinostat within the range of their clinical achievable concentrations on MM cells. While either agent alone inhibited MM cell proliferation in a dose-dependent manner, their combinations synergistically induced anti-proliferative/anti-survival effects on all MM cell lines (RPMI8226, U266, and MM1.R) tested. Further studies showed that the combinations of cladribine and Entinostat as compared to either agent alone more potently induced mitotic catastrophe in the MM cells, and resulted in a marked increase o...

  • Cladribine in combination with Entinostat synergistically elicits anti-proliferative/anti-survival effects on multiple myeloma cells
    2018
    Co-Authors: Bolun Wang, Hui Lyu, Shanshan Pei, Deye Song, Bolin Liu
    Abstract:

    Cladribine (2CdA), a synthetic purine analog interfering with DNA synthesis, is a medication used to treat hairy cell leukemia (HCL) and B-cell chronic lymphocytic leukemia. Entinostat, a selective class I histone deacetylase (HDAC) inhibitor, shows antitumor activity in various human cancers, including hematological malignancies. The therapeutic potential of cladribine and Entinostat against multiple myeloma (MM) remains unclear. Here we investigate the combinatorial effects of cladribine and Entinostat within the range of their clinical achievable concentrations on MM cells. While either agent alone inhibited MM cell proliferation in a dose-dependent manner, their combinations synergistically induced anti-proliferative/anti-survival effects on all MM cell lines (RPMI8226, U266, and MM1.R) tested. Further studies showed that the combinations of cladribine and Entinostat as compared to either agent alone more potently induced mitotic catastrophe in the MM cells, and resulted in a marked increase of the cells at G1 phase associated with decrease of Cyclin D1 and E2F-1 expression and upregulation of p21waf−1. Apoptotic ELISA and western blot analyses revealed that the combinations of cladribine and Entinostat exerted a much more profound activity to induce apoptosis and DNA damage response, evidenced by enhanced phosphorylation of histone H2A.X and the DNA repair enzymes Chk1 and Chk2. Collectively, our data demonstrate that the combinations of cladribine and Entinostat exhibit potent activity to induce anti-proliferative/anti-survival effects on MM cells via induction of cell cycle G1 arrest, apoptosis, and DNA damage response. Regimens consisting of cladribine and/or Entinostat may offer a new treatment option for patients with MM. Abbreviations: MM, multiple myeloma; HCL, hairy cell leukemia; HDAC, histone deacetylase; Ab, antibody; mAb, monoclonal Ab; FBS, fetal bovine serum; CI, combination index; PAGE, polyacrylamide gel electrophoresis; ELISA, enzyme-linked immunosorbent assay; PARP, poly(ADP-ribose) polymerase; MTS, 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium,inner salt

  • Functional cooperation of miR-125a, miR-125b, and miR-205 in Entinostat-induced downregulation of erbB2/erbB3 and apoptosis in breast cancer cells
    Cell death & disease, 2013
    Co-Authors: Shuiliang Wang, Jingcao Huang, Hui Lyu, Choon-kee Lee, Jieqiong Tan, Jinhan Wang, Bolin Liu
    Abstract:

    We reported that the class I HDAC inhibitor Entinostat induced apoptosis in erbB2-overexpressing breast cancer cells via downregulation of erbB2 and erbB3. Here, we study the molecular mechanism by which Entinostat dual-targets erbB2/erbB3. Treatment with Entinostat had no effect on erbB2/erbB3 mRNA, suggesting a transcription-independent mechanism. Entinostat decreased endogenous but not exogenous erbB2/erbB3, indicating it did not alter their protein stability. We hypothesized that Entinostat might inhibit erbB2/erbB3 protein translation via specific miRNAs. Indeed, Entinostat significantly upregulated miR-125a, miR-125b, and miR-205, that have been reported to target erbB2 and/or erbB3. Specific inhibitors were then used to determine whether these miRNAs had a causal role in Entinostat-induced downregulation of erbB2/erbB3 and apoptosis. Transfection with a single inhibitor dramatically abrogated Entinostat induction of miR-125a, miR-125b, or miR-205; however, none of the inhibitors blocked Entinostat action on erbB2/erbB3. In contrast, co-transfection with two inhibitors not only reduced their corresponding miRNAs, but also significantly abrogated Entinostat-mediated reduction of erbB2/erbB3. Moreover, simultaneous inhibition of two, but not one miRNA significantly attenuated Entinostat-induced apoptosis. Interestingly, although the other HDAC inhibitors, such as SAHA and panobinostat, exhibited activity as potent as Entinostat to induce growth inhibition and apoptosis in erbB2-overexpressing breast cancer cells, they had no significant effects on the three miRNAs. Instead, both SAHA- and panobinostat-decreased erbB2/erbB3 expression correlated with the reduction of their mRNA levels. Collectively, we demonstrate that Entinostat specifically induces expression of miR-125a, miR-125b, and miR-205, which act in concert to downregulate erbB2/erbB3 in breast cancer cells. Our data suggest that epigenetic regulation via miRNA-dependent or -independent mechanisms may represent a novel approach to treat breast cancer patients with erbB2-overexpressing tumors.

  • functional cooperation of mir 125a mir 125b and mir 205 in Entinostat induced downregulation of erbb2 erbb3 and apoptosis in breast cancer cells
    Cell Death and Disease, 2013
    Co-Authors: Shuiliang Wang, Jingcao Huang, Hui Lyu, Choon-kee Lee, Jieqiong Tan, Jinhan Wang, Bolin Liu
    Abstract:

    We reported that the class I HDAC inhibitor Entinostat induced apoptosis in erbB2-overexpressing breast cancer cells via downregulation of erbB2 and erbB3. Here, we study the molecular mechanism by which Entinostat dual-targets erbB2/erbB3. Treatment with Entinostat had no effect on erbB2/erbB3 mRNA, suggesting a transcription-independent mechanism. Entinostat decreased endogenous but not exogenous erbB2/erbB3, indicating it did not alter their protein stability. We hypothesized that Entinostat might inhibit erbB2/erbB3 protein translation via specific miRNAs. Indeed, Entinostat significantly upregulated miR-125a, miR-125b, and miR-205, that have been reported to target erbB2 and/or erbB3. Specific inhibitors were then used to determine whether these miRNAs had a causal role in Entinostat-induced downregulation of erbB2/erbB3 and apoptosis. Transfection with a single inhibitor dramatically abrogated Entinostat induction of miR-125a, miR-125b, or miR-205; however, none of the inhibitors blocked Entinostat action on erbB2/erbB3. In contrast, co-transfection with two inhibitors not only reduced their corresponding miRNAs, but also significantly abrogated Entinostat-mediated reduction of erbB2/erbB3. Moreover, simultaneous inhibition of two, but not one miRNA significantly attenuated Entinostat-induced apoptosis. Interestingly, although the other HDAC inhibitors, such as SAHA and panobinostat, exhibited activity as potent as Entinostat to induce growth inhibition and apoptosis in erbB2-overexpressing breast cancer cells, they had no significant effects on the three miRNAs. Instead, both SAHA- and panobinostat-decreased erbB2/erbB3 expression correlated with the reduction of their mRNA levels. Collectively, we demonstrate that Entinostat specifically induces expression of miR-125a, miR-125b, and miR-205, which act in concert to downregulate erbB2/erbB3 in breast cancer cells. Our data suggest that epigenetic regulation via miRNA-dependent or -independent mechanisms may represent a novel approach to treat breast cancer patients with erbB2-overexpressing tumors.

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  • Small Molecule Therapeutics Histone Deacetylase Inhibitor Entinostat Inhibits Tumor-Initiating Cells in Triple-Negative Breast Cancer Cells
    2016
    Co-Authors: A Schech, Preeti Shah, Armina Kazi, Gauri Sabnis
    Abstract:

    Mortality following breast cancer diagnosis ismainly due to the development of distant metastasis. To escape from the primary site, tumor cells undergo the epithelial-to-mesenchymal transi-tion (EMT), which helps them acquire amoremotile and invasive phenotype. In our previous study, we showed that class I selective HDAC inhibitor Entinostat reverses the EMT phenotype through reversal of epigenetic repression of E-cadherin. Recent evidence suggests that a subset of cells within a breast tumor may drive the metastatic outgrowth following escape from the primary site. These cells, termed tumor-initiating cells (TIC), represent a great threat to overall prognosis. They are critical in terms of drug resistance and tumor initiation at metastatic sites. Acquisition of EMT traits has also been shown to impart TIC phenotype to the cells, making EMT a "dual-threat " for prognosis. In the current study, we show that Entinostat treatment can reduce the per-centage of TIC cells from triple-negative breast cancer (TNBC) cells. Entinostat treatment was able to reduce the CD44high/ CD24low cell population, ALDH-1 activity, as well as protein and mRNA expression of known TIC markers such as Bmi-1, Nanog, and Oct-4. Next, we inoculated MDA-MB-231 cells transfected with firefly luciferase (231/Luc) in mammary fat pad of NSG mice. The mice were then treated with Entinostat (2.5 mg/kg/d), and tumor development and formation of metastasis were assessed by bioluminescence imaging. Treat-ment with Entinostat significantly reduced tumor formation at the primary site as well as lung metastasis. As such, Entinostat may help prevent development of distant metastasis. Mol Cancer Ther; 14(8); 1848–57. 2015 AACR

  • hdac inhibitor Entinostat restores responsiveness of letrozole resistant mcf 7ca xenografts to aromatase inhibitors through modulation of her 2
    Molecular Cancer Therapeutics, 2013
    Co-Authors: Gauri Sabnis, Olga Goloubeva, Armina A Kazi, Preeti Shah, Angela H Brodie
    Abstract:

    We previously showed that in innately resistant tumors, silencing of the estrogen receptor (ER) could be reversed by treatment with a histone deacetylase (HDAC) inhibitor, Entinostat. Tumors were then responsive to aromatase inhibitor (AI) letrozole. Here, we investigated whether ER in the acquired letrozole-resistant tumors could be restored with Entinostat. Ovariectomized athymic mice were inoculated with MCF-7Ca cells, supplemented with androstenedione (Δ(4)A), the aromatizable substrate. When the tumors reached about 300 mm(3), the mice were treated with letrozole. After initial response to letrozole, the tumors eventually became resistant (doubled their initial volume). The mice then were grouped to receive letrozole, exemestane (250 μg/d), Entinostat (50 μg/d), or the combination of Entinostat with letrozole or exemestane for 26 weeks. The growth rates of tumors of mice treated with the combination of Entinostat with letrozole or exemestane were significantly slower than with the single agent (P < 0.05). Analysis of the letrozole-resistant tumors showed Entinostat increased ERα expression and aromatase activity but downregulated Her-2, p-Her-2, p-MAPK, and p-Akt. However, the mechanism of action of Entinostat in reversing acquired resistance did not involve epigenetic silencing but rather included posttranslational as well as transcriptional modulation of Her-2. Entinostat treatment reduced the association of the Her-2 protein with HSP-90, possibly by reducing the stability of Her-2 protein. In addition, Entinostat also reduced Her-2 mRNA levels and its stability. Our results suggest that the HDAC inhibitor may reverse letrozole resistance in cells and tumors by modulating Her-2 expression and activity.

  • abstract 1314 hdac inhibitor Entinostat reverses letrozole resistance in mcf 7ca xenografts through modulation of her 2
    Cancer Research, 2013
    Co-Authors: Gauri Sabnis, Saranya Chumsri, Olga Goloubeva, Armina A Kazi, Angela Brodie
    Abstract:

    Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Development of aromatase inhibitors (AIs) has significantly improved the treatment outcome of hormone responsive post-menopausal breast cancer. However, not all tumors respond initially and others eventually acquire resistance. Using our hormone sensitive human aromatase expressing MCF-7Ca xenograft model, we also saw that although AI letrozole provides a longer control over tumor growth, tumors eventually began to grow. Furthermore, we observed that Her-2 protein levels within the tumors were upregulated as early as 4 weeks (as tumors were responding). Her-2 levels increased further as the tumors became resistant. A cell line was isolated from these Long-Term Letrozole Treated tumors (LTLT-Ca), which showed increased Her-2 and reduction in ERα and aromatase. The increase in Her-2 protein levels was not accompanied by gene amplification but we observed that Her-2 protein in LTLT-Ca cells was more stable and had a longer half-life than that in MCF-7Ca cells. In addition, when MCF-7Ca cells were deprived of estrogen (E2W) or treated with letrozole, stability of Her-2 protein was immediately increased, suggesting that lower estrogen levels stabilize Her-2. In order to identify novel approaches to restoring sensitivity to AIs, we treated letrozole resistant MCF-7Ca tumors with histone deacetylase (HDAC) inhibitor Entinostat (ENT). Addition of ENT to either letrozole or exemestane in letrozole resistant MCF-7Ca tumors led to increased ERα expression, aromatase activity and significantly inhibited further tumor growth, along with downregulation of Her-2, p-Her-2, p-MAPK and p-Akt. Based on the observations made in letrozole resistant tumors treated with Entinostat (with or without letrozole), we hypothesized that Entinostat reverses letrozole resistance due to modulation of Her-2. Entinostat reduced interaction between HSP-90 and Her-2 in Entinostat treated tumors, resulting in degradation of Her-2. Based on the findings that Her-2 is upregulated even when the tumors are responding, we evaluated the effect of adding Entinostat to letrozole from the start of treatment in the MCF-7Ca xenografts. Tumors of MCF-7Ca cells were allowed to form in the presence of androstenedione (Δ4A), aromatizable substrate for estrogen. When the tumors reached ∼300mm3, the mice were grouped to receive Δ4A 100μg/day (control), letrozole (1μg/day), Entinostat (50μg/day) or combination of Entinostat plus letrozole. Mice receiving letrozole treatment had significantly lower tumor growth rate than control (p=0.0001), so did mice treated with the combination of Entinostat plus letrozole (p<0.0001). The growth rate of tumors treated with Entinostat + letrozole was similar to the growth rate of letrozole alone suggesting that in the absence of acquired or de novo resistance pathways the addition of Entinostat did not provide benefit beyond the aromatase inhibitor alone. Citation Format: Gauri J. Sabnis, Armina Kazi, Olga Goloubeva, Saranya Chumsri, Angela Brodie. HDAC inhibitor Entinostat reverses letrozole resistance in MCF-7Ca xenografts through modulation of Her-2. [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 1314. doi:10.1158/1538-7445.AM2013-1314

  • Abstract 1314: HDAC inhibitor Entinostat reverses letrozole resistance in MCF-7Ca xenografts through modulation of Her-2.
    Endocrinology, 2013
    Co-Authors: Gauri Sabnis, Saranya Chumsri, Olga Goloubeva, Armina A Kazi, Angela Brodie
    Abstract:

    Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Development of aromatase inhibitors (AIs) has significantly improved the treatment outcome of hormone responsive post-menopausal breast cancer. However, not all tumors respond initially and others eventually acquire resistance. Using our hormone sensitive human aromatase expressing MCF-7Ca xenograft model, we also saw that although AI letrozole provides a longer control over tumor growth, tumors eventually began to grow. Furthermore, we observed that Her-2 protein levels within the tumors were upregulated as early as 4 weeks (as tumors were responding). Her-2 levels increased further as the tumors became resistant. A cell line was isolated from these Long-Term Letrozole Treated tumors (LTLT-Ca), which showed increased Her-2 and reduction in ERα and aromatase. The increase in Her-2 protein levels was not accompanied by gene amplification but we observed that Her-2 protein in LTLT-Ca cells was more stable and had a longer half-life than that in MCF-7Ca cells. In addition, when MCF-7Ca cells were deprived of estrogen (E2W) or treated with letrozole, stability of Her-2 protein was immediately increased, suggesting that lower estrogen levels stabilize Her-2. In order to identify novel approaches to restoring sensitivity to AIs, we treated letrozole resistant MCF-7Ca tumors with histone deacetylase (HDAC) inhibitor Entinostat (ENT). Addition of ENT to either letrozole or exemestane in letrozole resistant MCF-7Ca tumors led to increased ERα expression, aromatase activity and significantly inhibited further tumor growth, along with downregulation of Her-2, p-Her-2, p-MAPK and p-Akt. Based on the observations made in letrozole resistant tumors treated with Entinostat (with or without letrozole), we hypothesized that Entinostat reverses letrozole resistance due to modulation of Her-2. Entinostat reduced interaction between HSP-90 and Her-2 in Entinostat treated tumors, resulting in degradation of Her-2. Based on the findings that Her-2 is upregulated even when the tumors are responding, we evaluated the effect of adding Entinostat to letrozole from the start of treatment in the MCF-7Ca xenografts. Tumors of MCF-7Ca cells were allowed to form in the presence of androstenedione (Δ4A), aromatizable substrate for estrogen. When the tumors reached ∼300mm3, the mice were grouped to receive Δ4A 100μg/day (control), letrozole (1μg/day), Entinostat (50μg/day) or combination of Entinostat plus letrozole. Mice receiving letrozole treatment had significantly lower tumor growth rate than control (p=0.0001), so did mice treated with the combination of Entinostat plus letrozole (p

  • Expression of ERα and Aromatase in MDA-MB-231 Tumors by HDAC Inhibitor Entinostat Leads to Growth Inhibition by Aromatase Inhibitor Letrozole.
    Poster Discussion Abstracts, 2009
    Co-Authors: Gauri Sabnis, Saranya Chumsri, Olga Goloubeva, Luciana Macedo, Rabia A. Gilani, Nguyen Nguyen, Saraswati Sukumar, A Brodie
    Abstract:

    The treatment for hormone receptor-positive breast cancer has improved significantly since the development of aromatase inhibitors (AIs). Nevertheless, AIs are ineffective in estrogen receptor-negative (ER-) tumors, which comprise of approximately 25% of breast cancers and tend to be more aggressive. Studies have shown that repression of ER in these hormone receptor-negative tumors may be due to epigenetic modifications. The discovery of recruitment of histone deacetylase enzymes in gene silencing provides a rationale for inhibition of HDAC activity to release transcriptional repression as a potential therapeutic strategy. The objective of the present study was to express ERα and aromatase with HDACI treatment and thereby sensitize tumors to growth inhibition with aromatase inhibitors. In this study we used ER negative, hormone refractory MDA-MB-231 human breast cancer cells. Treatment with HDAC inhibitor Entinostat led to upregulation of ERα, aromatase and its activity in a dose dependent manner in cells and xenografts. MDA-MB-231 xenografts were grown in ovariectomized female nude mice. Mice were inoculated with 2.5 X 106 cells per site subcutaneously. When the tumors reached 150 mm3, the mice were grouped into 4 groups (n=10), so that the mean tumor volume was not statistically different across groups (p=0.88). Tumor volumes were measured twice weekly. The mice in the letrozole group had a mean tumor growth rate (β = 0.023 ± 0.014) that was not statistically different (p=0.76) from that of the control group (β = 0.038 ± 0.007). Also, the growth rate of Entinostat group (β = 0.034 ± 0.011) was not significantly lower than that of the control (p=0.33). However, the growth rate of Entinostat plus letrozole group ((β = -0.003 ± 0.013) was significantly lower than that of the control (p=0.01), Entinostat (p=0.03) and letrozole (p=0.049) groups. The combined treatment of Entinostat plus letrozole was significantly more effective than either agent alone. In addition, the ability of this combination to inhibit migration in vitro was examined by wound healing assay. The combination of Entinostat plus letrozole provides superior inhibition of migration (p Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 401.