Inhibition of histone deacetylase for the treatment of biliary tract cancer: A new effective pharmacological approach

Panobinostat penetrates the blood-brain barrier and achieves effective brain concentrations in a murine model

PURPOSE

Panobinostat, an orally bioavailable pan-HDAC inhibitor, has demonstrated potent activity in multiple malignancies, including pediatric brain tumors such as DIPG, with increased activity against H3K27M mutant cell lines. Given limited evidence regarding the CNS penetration of panobinostat, we sought to characterize its BBB penetration in a murine model.

METHODS

Panobinostat 15 mg/kg was administered IV to 12 CD-1 female mice. At specified time points, mice were euthanized, blood samples were collected, and brains were removed. LC-MS was performed to quantify panobinostat concentrations. C_max and AUC were estimated and correlated with previously published pharmacokinetic analyses and reports of IC-50 values in DIPG cell lines.

RESULTS

Mean panobinostat plasma concentrations (ng/mL) were 27.3 ± 2.5 at 1 h, 7.56 ± 1.8 at 2 h, 1.48 ± 0.56 at 4 h, and 2.33 ± 1.18 at 7 h. Mean panobinostat brain concentrations (ng/g) were 60.5 ± 6.1 at 1 h, 42.9 ± 5.4 at 2 h, 33.2 ± 6.1 at 4 h, and 28.1 ± 4.3 at 7 h. Brain-to-plasma ratio at 1 h was 2.22 and the brain to plasma AUC ratio was 2.63. Based on the published human pharmacokinetic data, the anticipated C_max in humans is expected to be significantly higher than the IC-50 identified in DIPG models.

CONCLUSION

It is expected that panobinostat would be effective in CNS tumors where the IC-50 is in the low nanomolar range. Thus, our data demonstrate panobinostat crosses the BBB and achieves concentrations above the IC-50 for DIPG and other brain tumors and should be explored further for clinical efficacy.

The histone deacetylase inhibitor panobinostat is a potent antitumor agent in canine diffuse large B-cell lymphoma

Non-Hodgkin lymphoma (NHL) is one of the most common causes of cancer-related death in the United States and Europe. Although the outcome of NHL patients has improved over the last years with current therapies, the rate of mortality is still high. A plethora of new drugs is entering clinical development for NHL treatment; however, the approval of new treatments remains low due in part to the paucity of clinically relevant models for validation. Canine lymphoma shares remarkable similarities with its human counterpart, making the dog an excellent animal model to explore novel therapeutic molecules and approaches. Histone deacetylase inhibitors (HDACis) have emerged as a powerful new class of anti-cancer drugs for human therapy. To investigate HDACi antitumor properties on canine diffuse large B-cell lymphoma, a panel of seven HDACi compounds (CI-994, panobinostat, SBHA, SAHA, scriptaid, trichostatin A and tubacin) was screened on CLBL-1 canine B-cell lymphoma cell line. Our results demonstrated that all HDACis tested exhibited dose-dependent inhibitory effects on proliferation of CLBL-1 cells, while promoting increased H3 histone acetylation. Amongst all HDACis studied, panobinostat proved to be the most promising compound and was selected for further in vitro and in vivo evaluation. Panobinostat cytotoxicity was linked to H3 histone and α-tubulin acetylation, and to apoptosis induction. Importantly, panobinostat efficiently inhibited CLBL-1 xenograft tumor growth, and strongly induced acetylation of H3 histone and apoptosis in vivo. In conclusion, these results provide new data validating HDACis and, especially, panobinostat as a novel anti-cancer therapy for veterinary applications, while contributing to comparative oncology.

Panobinostat induces apoptosis via production of reactive oxygen species and synergizes with topoisomerase inhibitors in cervical cancer cells

Cervical cancer is the fourth major cause of cancer-related deaths in women worldwide and is the most common cancer in developing countries. Therefore, a search for novel treatment modalities is warranted. The present study is designed to investigate the effect of pan histone deacetylase inhibitor, 'panobinostat', on cervical cancer cells alone and in combination with topoisomerase inhibitors. We assessed the effect of panobinostat on two cervical cancer cell lines, HeLa and SiHa, for cell viability, apoptosis, oxidative stress and mitochondrial function using various assays. The results indicate that panobinostat reduces the viability of cervical cancer cells in a dose- and time-dependent manner; it arrests HeLa cells in G0/G1 and SiHa cells in G2/M phase of the cell cycle. Panobinostat induced apoptosis through an increase in the ROS production and the disruption of mitochondrial membrane potential. Concomitantly the expression of anti-apoptotic gene Bcl-xL was reduced, while levels of CDK inhibitor p21 and caspase-9 were increased. Panobinostat increased the acetylation of histone H3 indicating HDAC inhibition. In addition, panobinostat also showed synergistic effect with topoisomerase inhibitors mediated by increased activation of caspase-3/7 activity compared to that in cells treated with panobinostat alone. These results suggest a combination therapy using inhibitors of histone deacetylase and topoisomerase together could hold the promise for an effective targeted therapeutic strategy.

Next-generation sequencing survey of biliary tract cancer reveals the association between tumor somatic variants and chemotherapy resistance

BACKGROUND

Biliary tract cancers (BTCs) are uncommon and are associated with a dismal prognosis. Combinations of gemcitabine and platinum chemotherapy (gemcitabine and platinum-based therapy [GP]) form the standard approach for treating advanced BTC. To characterize the spectrum of mutations and to identify potential biomarkers for a GP response in BTC, this study evaluated the genomic landscape and assessed whether mutations affecting DNA repair were associated with GP resistance.

METHODS

Pretreatment, formalin-fixed, paraffin-embedded samples from 183 BTC patients treated with GP were analyzed. Cox regression models were used to determine the association between mutations, progression-free survival (PFS), and overall survival (OS).

RESULTS

When genes with an incidence > 10% were considered, no individual gene was independently predictive of a GP response. In patients with unresectable BTC who received GP as their first-line therapy, the joint status of cyclin-dependent kinase inhibitor 2A (CDKN2A), tumor protein 53 (TP53), and AT-rich interaction domain 1A (ARID1A) was associated with PFS (P = .0004) and OS (P ≤ .0001). Patients with mutations in CDKN2A and TP53 were identified as a poor-prognosis cohort with a median PFS of 2.63 months and a median OS of 5.22 months. Patients with mutant ARID1A, regardless of the single-mutation status of TP53 or CDKN2A, had similar outcomes. A patient who exhibited mutations in all 3 genes had a median PFS of 20.37 months, and OS was not reached.

CONCLUSIONS

In the largest exploratory analysis of this kind for BTC, 3 prevalent, mutually exclusive mutations represent distinct patient cohorts. These mutations are prognostic and may represent a predictive biomarker for a GP response. Prospective studies to validate these findings are needed, and they should include the incorporation of therapies that exploit the genomic instability observed with these mutations in BTC. Cancer 2016;122:3657-66. © 2016 American Cancer Society.

Significance of expression of HDAC1 protein in gastric cancer

AIM: To investigate the expression of histone deacetylase 1 (HDAC1) protein in gastric cancer (GC) and to analyze its clinical significance.

METHODS: Immunohistochemistry was used to detect the expression of HDAC1 in 80 gastric cancer (GC) tissues and matched tumor adjacent tissues. The correlation between HDAC1 expression and clinicopathological features of GC was then analyzed.

RESULTS: The expression of HDAC1 was significantly higher in GC tissues than in tumor adjacent tissues (P < 0.05). The expression of HDAC1 was correlated with tumor differentiation, tumor lymph metastasis and survival in GC (P < 0.05).

CONCLUSION: HDAC1 is highly expressed in gastric cancer. Detection of HDAC1 expression may be helpful in early diagnosis and prognosis prediction in GC.

Strategy for enhancing the therapeutic efficacy of histone deacetylase inhibitor dacinostat: the novel paradigm to tackle monotonous cancer chemoresistance

Histone deacetylases (HDACs) regulate gene expression by creating the closed state of chromatin via histone hypoacetylation. Histone acetylation deregulation caused by aberrant expression of classical HDACs leads to imprecise gene regulation culminating in various diseases including cancer. Histone deacetylase inhibitors (HDACi), the small-molecules modulating the biological function of HDACs have shown promising results in inducing cell cycle arrest, differentiation and apoptosis in tumour models. HDACi do not show desired cytotoxic effect when used in monotherapy due to triggering of various resistance mechanisms in cancer cells emphasizing the desperate need of novel strategies that can be used to overcome such challenges. The present article provides intricate details about the novel HDACi dacinostat (LAQ-824) against multiple myeloma and acute myeloid leukaemia. The distinct molecular mechanisms modulated by dacinostat in exerting cytotoxic effect against the defined malignancies have also been detailed. The article also explains the strategy that can be used to circumvent the conventional therapy resistant cases and for enhancing the therapeutic efficacy of dacinostat for effective anticancer therapy.

TGF-β1 Reduces miR-29a Expression to Promote Tumorigenicity and Metastasis of Cholangiocarcinoma by Targeting HDAC4

Transforming growth factor β1 (TGF-β1) and miRNAs play important roles in cholangiocarcinoma progression. In this study, miR-29a level was found significantly decreased in both cholangiocarcinoma tissues and tumor cell lines. TGF-β1 reduced miR-29a expression in tumor cell lines. Furthermore, anti-miR-29a reduced the proliferation and metastasis capacity of cholangiocarcinoma cell lines in vitro, overexpression of miR-29a counteracted TGF-β1-mediated cell growth and metastasis. Subsequent investigation identified HDAC4 is a direct target of miR-29a. In addition, restoration of HDAC4 attenuated miR-29a-mediated inhibition of cell proliferation and metastasis. Conclusions: TGF-β1/miR-29a/HDAC4 pathway contributes to the pathogenesis of cholangiocarcinoma and our data provide new therapeutic targets for cholangiocarcinoma.

The significance of genetics for cholangiocarcinoma development

Cholangiocarcinoma (CCA) is a rare malignancy of the liver, arising from bile ducts. The incidence is increasing worldwide, but the prognosis has remained dismal and virtually unchanged in the past 30 years. Although several risk factors have been associated with the development of this cancer, none of them are normally identified in most patients. Diagnosis in advanced stages of the disease and limited therapeutic options contribute to poor survival rates. The recent analysis of genetic and epigenetic alterations occurring in CCA has shed new light in the understanding of the molecular mechanisms leading to the malignant transformation of biliary cells. Further studies in this direction may foster new diagnostic, prognostic and therapeutic approaches. This review provides a global overview of recent advances in CCA and describes the most important genetic mutations and epigenetic alterations so far reported in CCA.

Potential biomarkers for sensitivity of gallbladder cancer cells to gemcitabine

Gemcitabine (Gem)-based chemotherapies are the main therapeutic regimens for patients with unresectable advanced or metastatic gallbladder cancer (GBC). However, the modest ORR and mild benefit on survival demonstrates the need for finding biomarkers for sensitivity to Gem and hence improving the therapy. In present work, two GBC cell lines with vast difference in sensitivity to Gem were subjected to DNA microarray analysis. Dramatic expression difference was found in protein kinase A signaling, P2Y purigenic receptor signaling, ErbB signaling and p70S6K signaling. Predicted low expression of KRAS and inactivation of AKT/ERK signaling in Gem-resistant GBC cells was validated by quantitative PCR and immunoblotting, respectively. However, p70S6K, p38MAPK and NF-κB signaling was probably activated in Gem-resistant GBC cells, which deserves further investigation in more GBC cell lines and tissues. Our work provides potential pathway signatures for Gem sensitivity of GBC patients.

Role of Hydroxamate-Based Histone Deacetylase Inhibitors (Hb-HDACIs) in the Treatment of Solid Malignancies

Hydroxamate-based histone deacetylase inhibitors (Hb-HDACIs), such as vorinostat, belinostat and panobinostat, have been previously shown to have a wide range of activity in hematologic malignancies such as cutaneous T-cell lymphoma and multiple myeloma. Recent data show that they synergize with a variety of cytotoxic and molecular targeted agents in many different solid tumors, including breast, prostate, pancreatic, lung and ovarian cancer. Hb-HDACIs have a quite good toxicity profile and are now being tested in phase I and II clinical trials in solid tumors with promising results in selected neoplasms, such as hepatocarcinoma. This review will focus on their clinical activity and safety in patients with advanced solid neoplasms.

Knockdown of MTDH sensitizes endometrial cancer cells to cell death induction by death receptor ligand TRAIL and HDAC inhibitor LBH589 co-treatment

Understanding the molecular underpinnings of chemoresistance is vital to design therapies to restore chemosensitivity. In particular, metadherin (MTDH) has been demonstrated to have a critical role in chemoresistance. Over-expression of MTDH correlates with poor clinical outcome in breast cancer, neuroblastoma, hepatocellular carcinoma and prostate cancer. MTDH is also highly expressed in advanced endometrial cancers, a disease for which new therapies are urgently needed. In this present study, we focused on the therapeutic benefit of MTDH depletion in endometrial cancer cells to restore sensitivity to cell death. Cells were treated with a combination of tumor necrosis factor-α-related apoptosis-inducing ligand (TRAIL), which promotes death of malignant cells of the human reproductive tract, and histone deacetylase (HDAC) inhibitors, which have been shown to increase the sensitivity of cancer cells to TRAIL-induced apoptosis. Our data indicate that depletion of MTDH in endometrial cancer cells resulted in sensitization of cells that were previously resistant in response to combinatorial treatment with TRAIL and the HDAC inhibitor LBH589. MTDH knockdown reduced the proportion of cells in S and increased cell arrest in G2/M in cells treated with LBH589 alone or LBH589 in combination with TRAIL, suggesting that MTDH functions at the cell cycle checkpoint to accomplish resistance. Using microarray technology, we identified 57 downstream target genes of MTDH, including calbindin 1 and galectin-1, which may contribute to MTDH-mediated therapeutic resistance. On the other hand, in MTDH depleted cells, inhibition of PDK1 and AKT phosphorylation along with increased Bim expression and XIAP degradation correlated with enhanced sensitivity to cell death in response to TRAIL and LBH589. These findings indicate that targeting or depleting MTDH is a potentially novel avenue for reversing therapeutic resistance in patients with endometrial cancer.

Activity of deacetylase inhibitor panobinostat (LBH589) in cutaneous T-cell lymphoma models: Defining molecular mechanisms of resistance

Panobinostat (LBH589) is a highly potent deacetylase inhibitor that has demonstrated clinical efficacy in patients with advanced cutaneous T-cell lymphoma (CTCL). To gain a better understanding of the compound activity in this tumor type, we investigated the cellular and molecular effects of panobinostat using both in vitro and in vivo models of CTCL. All 4 tested CTCL cell lines exhibited very high sensitivity to panobinostat-induced growth inhibition. However, only 2 of 4 lines exhibited significant response to the cytotoxic activity of panobinostat. In a CTCL xenograft mouse tumor model, panobinostat treatment resulted in complete tumor regression. The difference in cell sensitivity to panobinostat-induced death enabled us to further investigate potential mechanisms responsible for tumor sensitivity or resistance. In CTCL cell lines that were insensitive to panobinostat-induced apoptosis, constitutively activated NF-kappaB and high levels of Bcl-2 were observed. Inhibition of Bcl-2 sensitized cells to the cytotoxic activity of panobinostat. Conversely, knockdown of Bax diminished the CTCL cell sensitivity. Interestingly, panobinostat could induce cytotoxicity in vorinostat-resistant CTCL cells by downregulating phosphorylated STAT3 and STAT5 proteins. These studies suggest distinct mechanisms responsible for resistance to different deacetylase inhibitors. We show that the intrinsic apoptotic signaling plays an essential role in mediating panobinostat anticancer activity. Moreover, cancer cell sensitivity to panobinostat treatment may be further improved by combination with inhibition of anti-apoptotic factors. These data provide preclinical support that panobinostat, as a single agent or in combination with other anticancer agents, is a promising therapy for CTCL.

The histone deacetylase inhibitor LBH589 enhances the anti-myeloma effects of chemotherapy in vitro and in vivo

Panobinostat (LBH589) is a potent histone deacetylase inhibitor (HDACi) that has shown anti-tumor activity in preclinical studies in both solid and hematological malignancies. We evaluated the anti-multiple myeloma (MM) effects of LBH589 alone and with melphalan or doxorubicin using MM cell lines and our human MM xenograft model LAGλ-1. LBH589 treatment resulted in increased acetylation of histones, induction of caspase cleavage, inhibition of cell proliferation and synergistic anti-MM effects with melphalan or doxorubicin in vitro. LBH589 with melphalan or doxorubicin also showed significantly enhanced anti-myeloma activity in vivo. These findings provide the basis for clinical development of these combination therapies.

Development of the pan-DAC inhibitor panobinostat (LBH589): successes and challenges

The histone deacetylase (HDAC) inhibitors are emerging as a highly useful class of anticancer agents that inhibit the enzyme HDAC involved in the deacetylation of histone and non-histone cellular proteins. The HDAC inhibitor, panobinostat (LBH589, Novartis Pharmaceuticals), achieves potent inhibition of all HDAC enzymes implicated in cancer and has demonstrated potent anti-tumor activity in preclinical models and promising clinical efficacy in cancer patients. In this review we discuss the successes and challenges surrounding the development of panobinostat, focusing on its proposed mechanism of action, preclinical anti-tumor activity, and early clinical efficacy in hematologic and solid tumors.

Experimental treatment of pancreatic cancer with two novel histone deacetylase inhibitors

AIM: To investigate in vitro and in vivo treatment with histone deacetylase inhibitors NVP-LAQ824 and NVP-LBH589 in pancreatic cancer.

METHODS: Cell-growth inhibition by NVP-LAQ824 and NVP-LBH589 was studied in vitro in 8 human pancreatic cancer cell lines using the 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. In addition, the anti-tumoral effect of NVP-LBH589 was studied in a chimeric mouse model. Anti-tumoral activity of the drugs was assessed by immunoblotting for p21^WAF-1, acH4, cell cycle analysis, TUNEL assay, and immunohistochemistry for MIB-1.

RESULTS: In vitro treatment with both compounds significantly suppressed the growth of all cancer cell lines and was associated with hyperacetylation of nucleosomal histone H4, increased expression of p21^WAF-1, cell cycle arrest at G2/M-checkpoint, and increased apoptosis. In vivo, NVP-LBH589 alone significantly reduced tumor mass and potentiated the efficacy of gemcitabine. Further analysis of the tumor specimens revealed slightly increased apoptosis and no significant reduction of cell proliferation.

CONCLUSION: Our findings suggest that NVP-LBH589 and NVP-LAQ824 are active against human pancreatic cancer, although the precise mechanism of in vivo drug action is not yet completely understood. Therefore, further preclinical and clinical studies for the treatment of pancreatic cancer are recommended.

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

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

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

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

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