Anti-tumour activity of two novel compounds in cisplatin-resistant testicular germ cell cancer

BACKGROUND

Resistance to cisplatin-based chemotherapy is associated with poor prognosis in testicular germ cell cancer, emphasising the need for new therapeutic approaches. In this respect, the therapeutic concept of anti-angiogenesis is of particular interest. In a previous study, we presented two novel anti-angiogenic compounds, HP-2 and HP-14, blocking the tyrosine kinase activity of angiogenic growth factor receptors, such as vascular endothelial growth factor receptor-2 (VEGFR-2), and related signalling pathways in testicular cancer. In this study, we investigated the efficacy of these new compounds in platinum-resistant testicular germ cell tumours (TGCTs), in vitro and in vivo.

METHODS AND RESULTS

Drug-induced changes in cell proliferation of the cisplatin-sensitive TGCT cell line 2102EP and its cisplatin-resistant counterpart 2102EP-R, both expressing the VEGFR-2, were evaluated by crystal violet staining. Both compounds inhibited the growth of cisplatin-resistant TGCT cells in a dose-dependent manner. In combination experiments with cisplatin, HP-14 revealed additive growth-inhibitory effects in TGCT cells, irrespective of the level of cisplatin resistance. Anti-angiogenic effects of HP compounds were confirmed by tube formation assays with freshly isolated human umbilical vein endothelial cells. Using TGCT cells inoculated onto the chorioallantoic membrane of fertilised chicken eggs (chicken chorioallantoic membrane assay), the anti-angiogenic and anti-proliferative potency of the novel compounds was also demonstrated in vivo. Gene expression profiling revealed changes in the expression pattern of genes related to DNA damage detection and repair, as well as in chaperone function after treatment with both cisplatin and HP-14, alone or in combination. This suggests that HP-14 can revert the lost effectiveness of cisplatin in the resistant cells by altering the expression of critical genes.

CONCLUSION

The novel compound HP-14 effectively inhibits the growth of cisplatin-resistant TGCT cells and suppresses tumour angiogenesis. Thus, HP-14 may be an interesting new agent that should be further explored for TGCT treatment, especially in TGCTs that are resistant to cisplatin.

A phase I trial of vorinostat and bortezomib in children with refractory or recurrent solid tumors: a Children's Oncology Group phase I consortium study (ADVL0916)

BACKGROUND

A pediatric Phase I trial was performed to determine the maximum-tolerated dose, dose-limiting toxicities (DLTs), and pharmacokinetics (PK) of vorinostat and bortezomib, in patients with solid tumors.

PROCEDURE

Oral vorinostat was administered on days 1-5 and 8-12 of a 21-day cycle (starting dose 180 mg/m(2) /day with dose escalations to 230 and 300 mg/m(2) /day). Bortezomib (1.3 mg/m(2) i.v.) was administered on days 1, 4, 8, and 11 of the same cycle. PK and correlative biology studies were performed during Cycle 1.

RESULTS

Twenty-three eligible patients [17 male, median age 12 years (range: 1-20)] were enrolled of whom 17 were fully evaluable for toxicity. Cycle 1 DLTs that occurred in 2/6 patients at dose level 3 (vorinostat 300 mg/m(2) /day) were Grade 2 sensory neuropathy that progressed to Grade 4 (n = 1) and Grade 3 nausea and anorexia (n = 1). No objective responses were observed. There was wide interpatient variability in vorinostat PK parameters. Bortezomib disposition was best described by a three-compartment model that demonstrated rapid distribution followed by prolonged elimination. We did not observe a decrease in nuclear factor-κB activity or Grp78 induction after bortezomib treatment in peripheral blood mononuclear cells from solid tumor patients.

CONCLUSION

The recommended Phase 2 dose and schedule is vorinostat (230 mg/m(2) /day PO on days 1-5 and 8-12) in combination with bortezomib (1.3 mg/m(2) /day i.v. on days 1, 4, 8, and 11 of a 21-day cycle) in children with recurrent or refractory solid tumors.

Anticancer effects of sodium butyrate on hepatocellular carcinoma cells in vitro

In the present study, we investigated the anticancer effects of sodium butyrate (NaBu) on hepatocellular carcinoma (HCC) cells in vitro. As a histone deacetylase (HDAC) inhibitor, NaBu upregulated Ac-H3 and inhibited HDAC4 protein expression in a time- and dose-dependent manner. MTT assays showed that treatment with NaBu at high concentrations significantly inhibited the growth of various HCC cells. Exposure to NaBu for 24 h induced cell cycle arrest in the SMMC-7721 and HepG2 cells. NaBu also induced the apoptosis of SMMC‑7721 cells. The expression levels of cell cycle- and apoptosis-related proteins were further investigated by western blot analysis using specific antibodies. The results provided a possible mechanism responsible for the inhibitory effects of NaBu on the growth of HCC cells. To further analyze the role of NaBu in cell migration, wound healing and Transwell assays were performed, indicating that NaBu significantly inhibits cell migration/invasion in HCC cells. Transforming growth factor-β1 (TGF-β1)-induced epithelial to mesenchymal transition (EMT) has been associated with tumor cell migration and invasion. The EMT markers, E-cadherin, vimentin and N-cadherin, were regulated by TGF-β1, while NaBu inhibited this process in which HDAC4 and matrix metalloproteinase (MMP)7 may be involved. Based on our findings, we propose that NaBu may be useful as an anticancer drug for HCC therapy.

Combination of a novel HDAC inhibitor OBP-801/YM753 and a PI3K inhibitor LY294002 synergistically induces apoptosis in human endometrial carcinoma cells due to increase of Bim with accumulation of ROS

OBJECTIVE

In most endometrial carcinoma, it has been observed that the PI3K/Akt pathway is abnormally accelerated in association with mutations in PIK3CA and PTEN. The present study aimed to examine the combined effect of a novel histone deacetylase (HDAC) inhibitor OBP-801/YM753 and a PI3K inhibitor LY294002 against human endometrial carcinoma cells.

METHODS

The effects of OBP-801/YM753 and LY294002 on the growth of human endometrial carcinoma HEC-1A cells were examined using WST-8 and colony formation assays. The distribution of the cell cycle or apoptosis was analyzed by flow cytometry. The accumulation of intracellular reactive oxygen species (ROS) was measured with a 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate, acetyl ester (CM-H2DCFDA) dye. The expression of apoptosis-related proteins was investigated by Western blotting. Mice engrafted with 1×10(8) HEC-1A cells were treated with OBP-801/YM753, LY294002 or the combination, and tumor volumes were measured.

RESULTS

The combination of OBP-801/YM753 and LY294002 significantly inhibited the cell growth on comparison with each agent alone and synergistically increased apoptosis with the induction of Bim, a well-known apoptosis inducer. Additionally, the apoptosis induced by the combination was shown to be dependent on intracellular ROS accumulation and Bim induction. Moreover, the apoptosis-inducing effect of OBP-801/YM753 with LY294002 was more potent than that of SAHA with LY294002. Combined treatment with OBP-801/YM753 and LY294002 significantly suppressed tumor growth compared to the control in vivo.

CONCLUSIONS

The combination of OBP-801/YM753 and LY294002 is effective on the inhibition of the growth of HEC-1A cells, and we suggest that this combination is promising a novel therapeutic strategy for endometrial carcinoma.

Comprehensive analysis of alterations in the miRNome in response to photodynamic treatment

Photodynamic therapy (PDT) is a local tumour treatment accepted for a number of indications. PDT operates via the cellular stress response through the production of reactive oxygen species and subsequent cellular damage, resulting in cell death. Although PDT-induced signalling and cytotoxicity mechanisms have been investigated, the effect of PDT on microRNA (miRNA) expression is largely unknown. Therefore, we conducted a comprehensive microarray-based analysis of the miRNome of human epidermoid carcinoma cells (A431) following in vitro photodynamic treatment using polyvinylpyrrolidone hypericin (PVPH) as a photosensitiser and nearly homogeneous apoptosis-inducing conditions. Using microarray analysis we found eight miRNAs to be significantly differentially expressed 5h post treatment compared with the baseline levels and three miRNAs with more than 2-fold differential expression that could be detected in 1 or 2 biological replicates. The verification of these results by quantitative RT-PCR including a detailed time-course revealed an up to 15-fold transient over-expression of miR-634, miR-1246, miR-1290 and miR-487b compared with the basal level. For these miRNAs, in silico mRNA target prediction yielded numerous target transcripts involved in the regulation of cell stress, apoptosis, cell adherence and proliferation. This study provides the first comprehensive miRNome analysis after PDT treatment and may help to develop novel miRNA-based therapeutic approaches to further increase the efficiency of PDT.

MicroRNAs in hepatocellular carcinoma: regulation, function, and clinical implications

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide and the third cause of cancer-related death. Poor understanding of the mechanisms underlying the pathogenesis of HCC makes it difficult to be diagnosed and treated at early stage. MicroRNAs (miRNAs), a class of noncoding single-stranded RNAs of ~22 nucleotides in length, posttranscriptionally regulate gene expression by base pairing with the 3' untranslated regions (3'UTRs) of target messenger RNAs (mRNAs). Aberrant expression of miRNAs is found in many if not all cancers, and many deregulated miRNAs have been proved to play crucial roles in the initiation and progression of cancers by regulating the expression of various oncogenes or tumor suppressor genes. In this Paper, we will summarize the regulations and functions of miRNAs aberrantly expressed in HCC and discuss the potential application of miRNAs as diagnostic and prognostic biomarkers of HCC and their potential roles in the intervention of HCC.

The pan-deacetylase inhibitor panobinostat modulates the expression of epithelial-mesenchymal transition markers in hepatocellular carcinoma models

Deacetylase inhibitors (DACis) represent a novel therapeutic option for human cancers by classically affecting proliferation or apoptosis. Since transdifferentiation and dedifferentiation play a key role in carcinogenesis, we investigated the epigenetic influence on the molecular differentiation status in human hepatocellular carcinoma (HCC) models. Markers of differentiation, including cytokeratin (Ck) 7, Ck8, Ck18, Ck19, Ck20, vimentin, sonic hedgehog homolog (SHH), smoothened (Smo), patched (Ptc), glioma-associated oncogene homolog 1 (Gli1), CD133, octamer-binding transcription factor 4 (Oct4) and β-catenin, were examined in the human HCC cell lines HepG2 and Hep3B in vitro and in vivo (xenograft model) using quantitative real-time PCR and immunohistochemistry following treatment with the pan-DACi panobinostat (LBH589). Compared to untreated controls, treated HepG2 xenografts, and to a lesser extent cell lines, demonstrated a significant increase of differentiation markers Ck7 and Ck19 (classical cholangiocellular type) and Ck8 and Ck18 (classical HCC type), and a decreased level of dedifferentiation markers vimentin (mesenchymal) and SHH/Ptc (embryonic), paralleled with a more membranous expression of β-catenin. These findings were dose-dependently correlated with tumor size, necrosis rate, microvessel density and mitosis/Ki-67-associated proliferation rate. Our results demonstrate that the differentiation status of human HCC cells is influenced by the pan-DACi panobinostat, indicating that this treatment may influence the epithelial-mesenchymal transition (EMT) status related to metastasis and aggressiveness.

Overexpression of histone deacetylase 2 predicts unfavorable prognosis in human gallbladder carcinoma

As important regulators of chromatin, histone deacetylases (HDACs) are involved in silencing tumor suppressor genes. HDAC2, a member of HDACs, has been demonstrated to be implicated in the development and progression of various human malignancies; however, its expression and role in human primary gallbladder carcinoma (PGC) are not fully understood. Therefore, we conducted this study to address this problem. The subjects were 136 patients underwent resection for PGC. Immunostainings for HDAC2 were performed on these archival tissues. The correlation of HDAC2 expression with clinicopathological characteristics including survival was analyzed. HDAC2 was positively expressed in the nucleus of tumor cells in 86.0 % (117/136) of PGC but not in the normal epithelium of the gallbladder. Additionally, there was a significant difference in the incidence of positive nodal metastasis between high and low HDAC2 expression groups (P = 0.001). The incidences of advanced clinical stage (P = 0.005) and pathologic T stage (P < 0.001), and higher histologic grade (P < 0.001) were respectively higher in the high HDAC2 expression group than in the low group. Moreover, univariate and multivariate analyses revealed the high HDAC2 expression to be an independent prognostic factor for both overall and disease-free survival of patients with PGC. High HDAC2 expression was correlated with a high incidence of lymph node metastasis and aggressive tumor progression of PGC. It also was an independent prognostic factor for poorer overall and disease-free survival in patients. Therefore, detection of HDAC2 expression may help us screen patients at increased risk of malignant behavior for PGC.

Prognostic and therapeutic relevance of c-FLIP in acute myeloid leukaemia

Chemoresistance is a major contributor to the aggressiveness of AML and is often due to insufficient apoptosis. The CFLAR gene is expressed as long and short splice forms encoding the anti-apoptotic proteins c-FLIP(L) and c-FLIP(S) (CFLAR(L) and CFLAR(S) , respectively) that play important roles in drug resistance. In univariate analyses of CFLAR mRNA expression in adult AML patients, those individuals with higher than median mRNA expression of the long splice form CFLAR(L) (but not the short splice form) had significantly lower 3 year overall survival (P = 0·04) compared to those with low expression. In cell line studies, simultaneous down-regulation of c-FLIP(L) and c-FLIP(S) proteins using siRNA induced apoptosis in U937 and NB-4 AML cells, but not K562 or OCI-AML3 cells. However, dual c-FLIP(L/S) downregulation sensitized all four cell lines to apoptosis induced by recombinant tumour necrosis factor-related apoptosis-inducing ligand (rTRAIL). Moreover, specific downregulation of c-FLIP(L) was found to recapitulate the phenotypic effects of dual c-FLIP(L/S) downregulation. The histone deacetylase (HDAC)1/2/3/6 inhibitor Vorinostat was found to potently down-regulate c-FLIP(L) expression by transcriptional and post-transcriptional mechanisms and to sensitize AML cells to rTRAIL. Further analyses using more selective HDAC inhibitors revealed that HDAC6 inhibition was not required for c-FLIP(L) down-regulation. These results suggest that c-FLIP(L) may have clinical relevance both as a prognostic biomarker and potential therapeutic target for HDAC inhibitors in AML although this requires further study.

A metal-based inhibitor of NEDD8-activating enzyme

A cyclometallated rhodium(III) complex [Rh(ppy)₂(dppz)]⁺ (1) (where ppy = 2-phenylpyridine and dppz = dipyrido[3,2-a:2′,3′-c]phenazine dipyridophenazine) has been prepared and identified as an inhibitor of NEDD8-activating enzyme (NAE). The complex inhibited NAE activity in cell-free and cell-based assays, and suppressed the CRL-regulated substrate degradation and NF-κB activation in human cancer cells with potency comparable to known NAE inhibitor MLN4924. Molecular modeling analysis suggested that the overall binding mode of 1 within the binding pocket of the APPBP1/UBA3 heterodimer resembled that for MLN4924. Complex 1 is the first metal complex reported to suppress the NEDDylation pathway via inhibition of the NEDD8-activating enzyme.

Impact of Salinomycin on human cholangiocarcinoma: induction of apoptosis and impairment of tumor cell proliferation in vitro

Background

Cholangiocarcinoma (CC) is a primary liver cancer with increasing incidence worldwide. Despite all efforts made in past years, prognosis remains to be poor. At least in part, this might be explained by a pronounced resistance of CC cells to undergo apoptosis. Thus, new therapeutic strategies are imperatively required. In this study we investigated the effect of Salinomycin, a polyether ionophore antibiotic, on CC cells as an appropriate agent to treat CC. Salinomycin was quite recently identified to induce apoptosis in cancer stem cells and to overcome apoptosis-resistance in several leukemia-cells and other cancer cell lines of different origin.

Methods

To delineate the effects of Salinomycin on CC, we established an in vitro cell culture model using three different human CC cell lines. After treatment apoptosis as well as migration and proliferation behavior was assessed and additional cell cycle analyses were performed by flowcytometry.

Results

By demonstrating Annexin V and TUNEL positivity of human CC cells, we provide evidence that Salinomycin reveals the capacity to break apoptosis-resistance in CC cells. Furthermore, we are able to demonstrate that the non-apoptotic cell fraction is characterized by sustainable impaired migration and proliferation. Cell cycle analyses revealed G2-phase accumulation of human CC cells after treatment with Salinomycin. Even though apoptosis is induced in two of three cell lines of CC cells, one cell line remained unaffected in regard of apoptosis but revealed as the other CC cells decreased proliferation and migration.

Conclusion

In this study, we are able to demonstrate that Salinomycin is an effective agent against previously resistant CC cells and might be a potential candidate for the treatment of CC in the future.

Epigenetic control of epithelial-mesenchymal-transition in human cancer

Development and tissue homeostasis as well as carcinogenesis share the evolutionary conserved process of epithelial-mesenchymal transition (EMT). EMT enables differentiated epithelial cells to trans-differentiate to a mesenchymal phenotype which is associated with diverse cellular properties including altered morphology, migration and invasion and stemness. In physiological development and tissue homeostasis, EMT exerts beneficial functions for structured tissue formation and maintenance. Under pathological conditions, EMT causes uncontrolled tissue repair and organ fibrosis, as well as the induction of tumor growth, angiogenesis and metastasis in the context of cancer progression. Particularly, the metastatic process is essentially linked to diverse EMT-driven functions which give the mesenchymal differentiated tumor cells the capacity to migrate and form micrometastases in distant organs. Recent analyses of the mechanisms controlling EMT revealed a significant epigenetic regulatory impact reflecting the reversible nature of EMTs. As several approaches of epigenetic therapy are already under clinical evaluation, including inhibitors of DNA methyl transferase and histone deacetylase, targeting the epigenetic regulation of EMT may represent a promising therapeutic option in the future. Therefore, we undertook this review to reassess the current knowledge on the roles of epigenetic control in the regulation of EMT in human cancer. These recent findings are discussed in view of their implications on future diagnostic and therapeutic strategies.

Inhibition of DNA methyltransferase activity and expression by treatment with the pan-deacetylase inhibitor panobinostat in hepatocellular carcinoma cell lines

BACKGROUND

Hepatocellular carcinoma (HCC) still represents an unmet medical need. Epigenetic inactivation of tumor suppressor genes like RASSF1A or APC by overexpression of DNA methyltransferases (DNMTs) has been shown to be common in HCC and to be linked to the overall prognosis of patients. Inhibitors of protein and histone deacetylases (DACi) have been demonstrated to possess strong anti-tumor effects in HCC models.

METHODS

We therefore investigated whether DACi also has any influence on the expression and activity of DNMTs and methylated target genes in HepG2 and Hep3B cell culture systems and in a xenograft model by immunohistochemistry, westernblotting, RT-qPCR and methylation-specific PCR.

RESULTS

Our findings demonstrate a rapid inhibition of DNMT activity 6 h after treatment with 0.1 μM of the pan-DACi panobinostat. A downregulation of DNMT mRNAs and protein were also observed at later points in time. This loss of DNMT activity and expression was paralleled by a diminished methylation of the target genes RASSF1A and APC and a concomitant re-expression of APC mRNA and protein. Analysis of HepG2 xenograft specimens confirmed these results in vivo.

CONCLUSION

We suggest a dual mode of action of DACi on DNA methylation status: a rapid inhibition of enzyme activity due to interference with posttranslational acetylation and a delayed effect on transcriptional control of DNMT genes by HDAC or miRNA mechanisms.

Emerging signaling pathways in hepatocellular carcinoma

Signaling pathways have become a major source of targets for novel therapies in hepatocellular carcinoma (HCC). Survival benefits achieved with sorafenib, a multikinase inhibitor, are unprecedented and underscore the importance of improving our understanding of how signaling networks interact in transformed cells. Numerous signaling modules are de-regulated in HCC, including some related to growth factor signaling (e.g., IGF, EGF, PDGF, FGF, HGF), cell differentiation (WNT, Hedgehog, Notch), and angiogenesis (VEGF). Intracellular mediators such as RAS and AKT/MTOR may also play a role in HCC development and progression. Different molecular mechanisms have been shown to induce aberrant pathway activation. These include point mutations, chromosomal aberrations, and epigenetically driven down-regulation. The use of novel molecular technologies such as next-generation sequencing in HCC research has enabled the identification of novel pathways previously underexplored in the HCC field, such as chromatin remodeling and autophagy. Considering recent failures of molecular therapies in advanced clinical trials (e.g., sunitinib, brivanib), survey of these and other new pathways may provide alternative therapeutic targets.

Histone deacetylases activate hepatocyte growth factor signaling by repressing microRNA-449 in hepatocellular carcinoma cells

BACKGROUND & AIMS

Histone deacetylation regulates chromatin remodeling and transcriptional down-regulation of specific genomic regions; it is altered in many types of cancer cells. We searched for microRNAs (miRs) that are affected by histone deacetylation and investigated the effects in hepatocellular carcinoma (HCC) cells.

METHODS

HCC cell lines (HepG2, HLE, HLF, and Huh7) and immortalized liver cell lines (THLE-2 and THLE-3) were incubated with the histone deacetylase inhibitor trichostatin A. Differentially expressed messenger RNAs (mRNAs) and miRs were identified by expression profiling. Small interfering RNAs were used to reduce levels of histone deacetylases (HDAC)1-3, and HCC cell lines were transfected with miR-449. We evaluated growth of xenograft tumors from modified cells in nude mice. Cells were analyzed by immunoblot and luciferase reporter assays. We analyzed HCC samples from 23 patients.

RESULTS

HDAC1-3 were up-regulated in HCC samples from patients. In cell lines, inhibition of HDAC significantly increased levels of hsa-miR-449a. c-MET mRNA, which encodes the receptor tyrosine kinase for hepatocyte growth factor, is a target of miR-449. Incubation of HCC cells with trichostatin A or transfection with miR-449 reduced expression of c-MET and phosphorylation of extracellular signal-regulated kinases 1 and 2 (downstream effectors of c-MET), increased apoptosis, and reduced proliferation. Huh-7 cells transfected with miR-449 formed tumors more slowly in mice than cells expressing control miRs. HCC samples from patients had lower levels of miR-449 and higher levels of c-MET than human reference.

CONCLUSIONS

In HCC cells, up-regulation of HDAC1-3 reduces expression of miR-449. miR-449 binds c-MET mRNA to reduce its levels, promoting apoptosis and reducing proliferation of liver cells. Expression of miR-449 slows growth of HCC xenograft tumors in mice; this miR might function as a tumor suppressor.

Organometallic Palladium Complexes with a Water-Soluble Iminophosphorane Ligand as Potential Anticancer Agents

The synthesis and characterization of a new water-soluble iminophosphorane ligand TPA=N-C(O)-2BrC(6)H(4) (C,N-IM; TPA = 1,3,5-triaza-7-phosphaadamantane) 1 is reported. Oxidative addition of 1 to Pd(2)(dba)(3) affords the orthopalladated dimer [Pd(μ-Br){C(6)H(4)(C(O)N=TPA-kC,N)-2}](2) (2) as a mixture of cis and trans isomers (1:1 molar ratio) where the iminophosphorane moeity behaves as a C,N-pincer ligand. By addition of different neutral or monoanionic ligands to 2, the bridging bromide can be cleaved and a variety of hydrophilic or water-soluble mononuclear organometallic palladium(II) complexes of the type [Pd{C(6)H(4)(C(O)N=TPA-kC,N)-2}(L-L)] (L-L = acac (3); S(2)CNMe(2) (4); 4,7-Diphenyl-1,10-phenanthrolinedisulfonic acid disodium salt C(12)H(6)N(2)(C(6)H(4)SO(3)Na)(2) (5)); [Pd{C(6)H(4)(C(O)N=TPA-kC,N)-2}(L)Br] (L = P(mC(6)H(4)SO(3)Na)(3) (6); P(3-Pyridyl)(3) (7)) and, [Pd(C(6)H(4)(C(O)N=TPA)-2}(TPA)(2)Br] (8) are obtained as single isomers. All new complexes were tested as potential anticancer agents and their cytotoxicity properties were evaluated in vitro against human Jurkat-T acute lymphoblastic leukemia cells, normal T-lymphocytes (PBMC) and DU-145 human prostate cancer cells. Compounds [Pd(μ-Br){C(6)H(4)(C(O)N=TPA-kC,N)-2}](2) (2) and [Pd{C(6)H(4)(C(O)N=TPA-kC,N)-2}(acac)] 3 (which has been crystallographically characterized) display the higher cytotoxicity against the above mentioned cancer cell lines while being less toxic to normal T-lymphocytes (peripheral blood mononuclear cells: PBMC). In addition, 3 is very toxic to cisplatin resistant Jurkat shBak indicating a cell death pathway that may be different to that of cisplatin. The interaction of 2 and 3 with plasmid (pBR322) DNA is much weaker than that of cisplatin pointing to an alternative biomolecular target for these cytotoxic compounds. All the compounds show an interaction with human serum albumin (HSA) faster than that of cisplatin.

Epigenetic therapy using belinostat for patients with unresectable hepatocellular carcinoma: a multicenter phase I/II study with biomarker and pharmacokinetic analysis of tumors from patients in the Mayo Phase II Consortium and the Cancer Therapeutics Research Group

PURPOSE

Epigenetic aberrations have been reported in hepatocellular carcinoma (HCC). In this study of patients with unresectable HCC and chronic liver disease, epigenetic therapy with the histone deacetylase inhibitor belinostat was assessed. The objectives were to determine dose-limiting toxicity and maximum-tolerated dose (MTD), to assess pharmacokinetics in phase I, and to assess activity of and explore potential biomarkers for response in phase II.

PATIENTS AND METHODS

Major eligibility criteria included histologically confirmed unresectable HCC, European Cooperative Oncology Group performance score ≤ 2, and adequate organ function. Phase I consisted of 18 patients; belinostat was given intravenously once per day on days 1 to 5 every 3 weeks; dose levels were 600 mg/m(2) per day (level 1), 900 mg/m(2) per day (level 2), 1,200 mg/m(2) per day (level 3), and 1,400 mg/m(2) per day (level 4). Phase II consisted of 42 patients. The primary end point was progression-free survival (PFS), and the main secondary end points were response according to Response Evaluation Criteria in Solid Tumors (RECIST) and overall survival (OS). Exploratory analysis was conducted on pretreatment tumor tissues to determine whether HR23B expression is a potential biomarker for response.

RESULTS

Belinostat pharmacokinetics were linear from 600 to 1,400 mg/m(2) without significant accumulation. The MTD was not reached at the maximum dose administered. Dose level 4 was used in phase II. The median number of cycles was two (range, one to 12). The partial response (PR) and stable disease (SD) rates were 2.4% and 45.2%, respectively. The median PFS and OS were 2.64 and 6.60 months, respectively. Exploratory analysis revealed that disease stabilization rate (complete response plus PR plus SD) in tumors having high and low HR23B histoscores were 58% and 14%, respectively (P = .036).

CONCLUSION

Epigenetic therapy with belinostat demonstrates tumor stabilization and is generally well-tolerated. HR23B expression was associated with disease stabilization.

Profiling mTOR pathway in neuroendocrine tumors

The serine/threonine kinase mammalian target of rapamycin (mTOR) plays a central role in regulating critical cellular processes such as growth, proliferation, and protein synthesis. The study of cancer predisposing syndromes within which neuroendocrine tumors (NETs) may arise has furnished clues on the involvement of mTOR pathway in sporadic diseases so far. Recent comprehensive analyses have definitely shown activation of mTOR pathway in both experimental and human sporadic NETs. Upstream regulators of mTOR (PTEN and TSC2) have been found mutated in sporadic pNETs. Activation of mTOR pathways in NETs is already demonstrated by expression profiles analysis that revealed downregulation of TSC2 gene and alterations of TSC2 and PTEN protein expression in the vast majority of well-differentiated tumors. Moreover, a global microRNA expression analysis revealed the overexpression, in highly aggressive tumors, of a microRNA (miR-21) that targets PTEN reducing its expression and therefore leading to mTOR activation as well. Overall, these clues have furnished the rationale for the use of mTOR inhibitors the treatment of pNETs. With the recent approval of Everolimus (mTOR-targeted drug) for the treatment of advanced pNETs, this paradigm has been effectively translated into the clinical setting. In this review, we discuss mTOR pathway involvement in NETs, the clinical evidence supporting the use of mTOR inhibitors in cancer treatment, and the current clinical issues that remain to be elucidated to improve patient management.

Profiling mTOR pathway in neuroendocrine tumors

The serine/threonine kinase mammalian target of rapamycin (mTOR) plays a central role in regulating critical cellular processes such as growth, proliferation, and protein synthesis. The study of cancer predisposing syndromes within which neuroendocrine tumors (NETs) may arise has furnished clues on the involvement of mTOR pathway in sporadic diseases so far. Recent comprehensive analyses have definitely shown activation of mTOR pathway in both experimental and human sporadic NETs. Upstream regulators of mTOR (PTEN and TSC2) have been found mutated in sporadic pNETs. Activation of mTOR pathways in NETs is already demonstrated by expression profiles analysis that revealed downregulation of TSC2 gene and alterations of TSC2 and PTEN protein expression in the vast majority of well-differentiated tumors. Moreover, a global microRNA expression analysis revealed the overexpression, in highly aggressive tumors, of a microRNA (miR-21) that targets PTEN reducing its expression and therefore leading to mTOR activation as well. Overall, these clues have furnished the rationale for the use of mTOR inhibitors the treatment of pNETs. With the recent approval of Everolimus (mTOR-targeted drug) for the treatment of advanced pNETs, this paradigm has been effectively translated into the clinical setting. In this review, we discuss mTOR pathway involvement in NETs, the clinical evidence supporting the use of mTOR inhibitors in cancer treatment, and the current clinical issues that remain to be elucidated to improve patient management.

Management of hepatocellular carcinoma: beyond sorafenib

The positive results of sorafenib have unveiled a new direction of research in the management of hepatocellular carcinoma (HCC). Since then intensive efforts have been focused on development of novel management strategy to further improve the outcome for patients with HCC. Emerging data have suggested that tumor progression of HCC is driven by a number of deregulated signaling pathways and/or epigenetic mechanism. Thus much effort is dedicated to identification of novel agents targeting these dysregulated pathways. Combinations of targeted therapeutics and transarterial chemoembolization (TACE), or different systemic therapeutics also hold the promise to improve treatment outcome beyond sorafenib. This review aims to summarize the current status of clinical development of treatment in HCC. Perspectives on future direction of research will also be discussed.

Management of hepatocellular carcinoma: beyond sorafenib

The positive results of sorafenib have unveiled a new direction of research in the management of hepatocellular carcinoma (HCC). Since then intensive efforts have been focused on development of novel management strategy to further improve the outcome for patients with HCC. Emerging data have suggested that tumor progression of HCC is driven by a number of deregulated signaling pathways and/or epigenetic mechanism. Thus much effort is dedicated to identification of novel agents targeting these dysregulated pathways. Combinations of targeted therapeutics and transarterial chemoembolization (TACE), or different systemic therapeutics also hold the promise to improve treatment outcome beyond sorafenib. This review aims to summarize the current status of clinical development of treatment in HCC. Perspectives on future direction of research will also be discussed.

Preclinical cancer chemoprevention studies using animal model of inflammation-associated colorectal carcinogenesis

Inflammation is involved in all stages of carcinogenesis. Inflammatory bowel disease, such as ulcerative colitis and Crohn’s disease is a longstanding inflammatory disease of intestine with increased risk for colorectal cancer (CRC). Several molecular events involved in chronic inflammatory process are reported to contribute to multi-step carcinogenesis of CRC in the inflamed colon. They include over-production of free radicals, reactive oxygen and nitrogen species, up-regulation of inflammatory enzymes in arachidonic acid biosynthesis pathway, up-regulation of certain cytokines, and intestinal immune system dysfunction. In this article, firstly I briefly introduce our experimental animal models where colorectal neoplasms rapidly develop in the inflamed colorectum. Secondary, data on preclinical cancer chemoprevention studies of inflammation-associated colon carcinogenesis by morin, bezafibrate, and valproic acid, using this novel inflammation-related colorectal carcinogenesis model is described.

Functional genomic studies: insights into the pathogenesis of liver cancer

Liver cancer is the sixth-most-common cancer overall but the third-most-frequent cause of cancer death. Among primary liver cancers, hepatocellular carcinoma (HCC), the major histological subtype, is associated with multiple risk factors, including hepatitis B and C virus infection, alcohol consumption, obesity, and diet contamination. Although previous studies have revealed that certain genetic and epigenetic changes, such as TP53 and β-catenin mutations, occur in HCC cells, the pathogenesis of this cancer remains obscure. Functional genomic approaches-including genome-wide association studies, whole-genome and whole-exome sequencing, array-based comparative genomic hybridization, global DNA methylome mapping, and gene or noncoding RNA expression profiling-have recently been applied to HCC patients with different clinical features to uncover the genetic risk factors and underlying molecular mechanisms involved in this cancer's initiation and progression. The genome-wide analysis of germline and somatic genetic and epigenetic events facilitates understanding of the pathogenesis and molecular classification of liver cancer as well as the identification of novel diagnostic biomarkers and therapeutic targets for cancer.

Combination therapy for hepatocellular carcinoma: additive preclinical efficacy of the HDAC inhibitor panobinostat with sorafenib

BACKGROUND & AIMS

Hepatocellular carcinoma (HCC) is a heterogeneous cancer in which sorafenib is the only approved systemic therapy. Histone deacetylases (HDAC) are commonly dysregulated in cancer and therefore represent promising targets for therapies, however their role in HCC pathogenesis is still unknown. We analyzed the expression of 11 HDACs in human HCCs and assessed the efficacy of the pan-HDAC inhibitor panobinostat alone and in combination with sorafenib in preclinical models of liver cancer.

METHODS

Gene expression and copy number changes were analyzed in a cohort of 334 human HCCs, while the effects of panobinostat and sorafenib were evaluated in three liver cancer cell lines and a murine xenograft model.

RESULTS

Aberrant HDAC expression was identified and validated in 91 and 243 HCCs, respectively. Upregulation of HDAC3 and HDAC5 mRNAs was significantly correlated with DNA copy number gains. Inhibiting HDACs with panobinostat led to strong anti-tumoral effects in vitro and vivo, enhanced by the addition of sorafenib. Cell viability and proliferation declined, while apoptosis and autophagy increased. Panobinostat increased histone H3 and HSP90 acetylation, downregulated BIRC5 (survivin) and upregulated CDH1. Combination therapy with panobinostat and sorafenib significantly decreased vessel density, and most significantly decreased tumor volume and increased survival in HCC xenografts.

CONCLUSIONS

Aberrant expression of several HDACs and copy number gains of HDAC3 and HDAC5 occur in HCC. Treatment with panobinostat combined with sorafenib demonstrated the highest preclinical efficacy in HCC models, providing the rationale for clinical studies with this novel combination.

Targeting triple-negative breast cancer cells with the histone deacetylase inhibitor panobinostat

INTRODUCTION

Of the more than one million global cases of breast cancer diagnosed each year, approximately fifteen percent are characterized as triple-negative, lacking the estrogen, progesterone, and Her2/neu receptors. Lack of effective therapies, younger age at onset, and early metastatic spread have contributed to the poor prognoses and outcomes associated with these malignancies. Here, we investigate the ability of the histone deacetylase inhibitor panobinostat (LBH589) to selectively target triple-negative breast cancer (TNBC) cell proliferation and survival in vitro and tumorigenesis in vivo.

METHODS

TNBC cell lines MDA-MB-157, MDA-MB-231, MDA-MB-468, and BT-549 were treated with nanomolar (nM) quantities of panobinostat. Relevant histone acetylation was verified by flow cytometry and immunofluorescent imaging. Assays for trypan blue viability, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) proliferation, and DNA fragmentation were used to evaluate overall cellular toxicity. Changes in cell cycle progression were assessed with propidium iodide flow cytometry. Additionally, qPCR arrays were used to probe MDA-MB-231 cells for panobinostat-induced changes in cancer biomarkers and signaling pathways. Orthotopic MDA-MB-231 and BT-549 mouse xenograft models were used to assess the effects of panobinostat on tumorigenesis. Lastly, flow cytometry, ELISA, and immunohistochemical staining were applied to detect changes in cadherin-1, E-cadherin (CDH1) protein expression and the results paired with confocal microscopy in order to examine changes in cell morphology.

RESULTS

Panobinostat treatment increased histone acetylation, decreased cell proliferation and survival, and blocked cell cycle progression at G2/M with a concurrent decrease in S phase in all TNBC cell lines. Treatment also resulted in apoptosis induction at 24 hours in all lines except the MDA-MB-468 cell line. MDA-MB-231 and BT-549 tumor formation was significantly inhibited by panobinostat (10 mg/kg/day) in mice. Additionally, panobinostat up-regulated CDH1 protein in vitro and in vivo and induced cell morphology changes in MDA-MB-231 cells consistent with reversal of the mesenchymal phenotype.

CONCLUSIONS

This study revealed that panobinostat is overtly toxic to TNBC cells in vitro and decreases tumorigenesis in vivo. Additionally, treatment up-regulated anti-proliferative, tumor suppressor, and epithelial marker genes in MDA-MB-231 cells and initiated a partial reversal of the epithelial-to-mesenchymal transition. Our results demonstrate a potential therapeutic role of panobinostat in targeting aggressive triple-negative breast cancer cell types.

Apoptosis induction by SAHA in cutaneous T-cell lymphoma cells is related to downregulation of c-FLIP and enhanced TRAIL signaling

Suberoylanilide hydroxamic acid (SAHA) has been approved for the treatment of cutaneous T-cell lymphoma (CTCL), but its mode of action remained largely elusive. As shown here in four CTCL cell lines, loss of cell viability correlated with significant time- and dose-dependent induction of apoptosis, whereas cytotoxicity was less pronounced. Both extrinsic and intrinsic apoptosis pathways were activated, as seen by processing of initiator caspases 8 and 9, loss of mitochondrial membrane potential, and cytochrome c release. Characteristically, antiapoptotic mediators such as Mcl-1, XIAP, survivin, and c-FLIP were downregulated. Consistent with its critical function, c-FLIP overexpression resulted in a significant decrease of SAHA-mediated apoptosis. Enhanced sensitivity to TRAIL (TNF-related apoptosis-inducing ligand) and enhanced TRAIL signaling was seen in CTCL cell lines with high sensitivity, whereas cell lines with moderate response were characterized by downregulation of TRAIL-R2 and weaker TRAIL expression. Comparable proapoptotic responses to SAHA and to the combination with TRAIL were seen in ex vivo tumor T cells of CTCL patients. Thus, activation of extrinsic apoptosis pathways, related to c-FLIP downregulation and enhanced TRAIL signaling, appeared as characteristic for CTCL cell responsiveness to SAHA. An improved understanding of the pathways may facilitate its targeted use and the selection of suitable combinations.

Targeted therapy of hepatocellular carcinoma: present and future

Following the encouraging results of sorafenib in advanced hepatocellular carcinoma (HCC), targeted therapy has become a new direction of research in the treatment of HCC. Emerging data provide evidence that the pathogenesis and progression of HCC are mediated by a number of molecular defects and dysregulated pathways. Novel targeted therapies are designed to inhibit the aberrant pathways at a molecular level with an aim to improve the clinical outcome. For the past few years, an increasing number of targeted agents have been tested in HCC in the clinical setting. This review aims to summarize the current status of clinical development of targeted therapy in HCC, with focus on novel agents targeting angiogenesis, signal transduction and epigenetic dysregulation of tumors. The review also discusses the lessons learned from outcomes of completed clinical trials and provides perspectives on future clinical trials in HCC.

Vorinostat approved in Japan for treatment of cutaneous T-cell lymphomas: status and prospects

Histone acetylation and deacetylation play important roles in the regulation of gene transcription and in the modulation of chromatin structure. The levels of histone acetylation are determined by the activities of histone acetyltransferases and histone deacetylases (HDACs). HDACs are associated with a number of oncogenes and tumor suppressor genes and can be aberrantly expressed and/or inappropriately activated in cancer cells. HDAC inhibitors have therefore recently emerged as a novel treatment modality against malignancies. They regulate gene expression by enhancing the acetylation of not only histones but also nonhistone proteins, including transcription factors, transcription regulators, signal transduction mediators, and DNA repair enzymes, and they inhibit cancer growth. Vorinostat (suberoylanilide hydroxamic acid) is one of the most potent HDAC inhibitors, and was approved in Japan in 2011 for the treatment of cutaneous T-cell lymphoma. Numerous clinical trials have shown it to be effective against cutaneous T-cell lymphoma but less so against other types of cancer. Because vorinostat can overcome resistance to or enhance the efficacy of other anticancer agents, such as 5-fluorouracil, carboplatin, paclitaxel, bortezomib, and tamoxifen, combination therapies using vorinostat and these agents have been investigated. This review introduces the background and mechanism of action of vorinostat and describes the results of clinical trials using vorinostat, both as a single agent and in combination with other anticancer agents, against cutaneous T-cell lymphoma and other malignancies.

CS055 (Chidamide/HBI-8000), a novel histone deacetylase inhibitor, induces G1 arrest, ROS-dependent apoptosis and differentiation in human leukaemia cells

CS055 (Chidamide/HBI-8000) is a novel benzamide-type HDACi (histone deacetylase inhibitor), which has entered Phase I clinical trials in the U.S. and Phase II/III in China. In the present study, we investigated the effects of CS055 on proliferation, differentiation and apoptosis in human leukaemia cell lines and primary myeloid leukaemia cells. The results showed that at low concentrations (<1 μM), CS055 induced G1 arrest. At moderate concentrations (0.5 μM–2 μM), CS055 induced differentiation, as determined by the increased expression of the myeloid differentiation marker CD11b. At relatively high concentrations (2 μM–4 μM), CS055 potently induced caspase-dependent apoptosis. Co-treatment with the ROS (reactive oxygen species) scavengers N-acetyl-L-cysteine or Tiron blocked CS055-induced cell differentiation and apoptosis, suggesting an essential role for ROS in these effects. Cytochrome c release and ROS-mediated mitochondrial dysfunction are involved in CS055-induced apoptosis of leukaemia. In addition to cell lines, CS055 also exhibits therapeutic effects in human primary leukaemia cells. Moreover, daily oral CS055 treatment of nude mice bearing HL60 cell xenografts suppressed tumour growth, induced tumour cell apoptosis and prolonged the survival of tumour-bearing mice. In conclusion, our findings demonstrate that CS055 is a novel HDACi with potential chemotherapeutic value in several haematological malignancies, especially leukaemia.

Structural approaches to obtain kinase selectivity

One of the grand challenges in kinase drug discovery is the design of small-molecule inhibitors with selectivity profiles that will ultimately be efficacious in the clinic. Current medicinal chemistry strategies make heavy use of structural, biophysical and computational approaches to achieve this multi-faceted goal. Here we review structure-based approaches underlying the development of several molecules that are currently in clinical trials, including the cMet inhibitor ARQ197 and the Bcr-Abl inhibitor ponatinib. We highlight the challenge posed by the emergence of resistance mutants and discuss promising lead generation strategies to obtain selective inhibitors of protein and lipid kinases such as targeting of specific sites, the use of fragment-based approaches and new chemical probes based on metal complexes.

Combination of the deacetylase inhibitor panobinostat and the multi-kinase inhibitor sorafenib for the treatment of metastatic hepatocellular carcinoma - review of the underlying molecular mechanisms and first case report

Advanced hepatocellular carcinoma still represents an unmet medical need that has only a limited overall survival despite the introduction of the multi-kinase inhibitor sorafenib. Recently, inhibitors of histone and other protein deacetylases have been established as novel therapeutic approaches to cancer diseases. We here review the molecular rationale for combining these two novel targeted therapies and report a patient with metastasized hepatocellular carcinoma who showed a partial remission of primary and metastatic lesions for five months after a combination therapy with sorafenib and the orally available pan-deacetylase inhibitor panobinostat.

A New Player in the Development of TRAIL Based Therapies for Hepatocarcinoma Treatment: ATM Kinase

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide. HCCs are genetically and phenotypically heterogeneous tumors characterized by very poor prognosis, mainly due to the lack, at present, of effective therapeutic options, as these tumors are rarely suitable for radiotherapy and often resistant to chemotherapy protocols. In the last years, agonists targeting the Tumor Necrosis Factor Related Apoptosis Inducing Ligand (TRAIL) death receptor, has been investigated as a valuable promise for cancer therapy, based on their selectivity for malignant cells and low toxicity for healthy cells. However, many cancer models display resistance to death receptor induced apoptosis, pointing to the requirement for the development of combined therapeutic approaches aimed to selectively sensitize cancer cells to TRAIL. Recently, we identified ATM kinase as a novel modulator of the ability of chemotherapeutic agents to enhance TRAIL sensitivity. Here, we review the biological determinants of HCC responsiveness to TRAIL and provide an exhaustive and updated analysis of the molecular mechanisms exploited for combined therapy in this context. The role of ATM kinase as potential novel predictive biomarker for combined therapeutic approaches based on TRAIL and chemotherapeutic drugs will be closely discussed.

Histone deacetylase inhibitor-mediated sensitization to TRAIL-induced apoptosis in childhood malignancies is not associated with upregulation of TRAIL receptor expression, but with potentiated caspase-8 activation

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has great potential for the treatment of cancer because it targets tumor cells while sparing normal cells. Several cancers, however, fail to respond to TRAIL's antineoplastic effects. These resistant tumors require cotreatment with sensitizing agents in order for TRAIL to exert anticancer activity. Histone deacetylase inhibitors (HDACi) have been recognized as potent TRAIL sensitizers. In searching for the determinants of TRAIL responsiveness, HDACi-mediated TRAIL sensitization has been predominantly attributed to TRAIL receptor upregulation. This explanation, however, has been challenged by a few studies. The aim of the present study was to explore the relevance of TRAIL receptor expression for HDACi-mediated TRAIL sensitization in childhood tumors, i.e., in medulloblastoma, Ewing's sarcoma and osteosarcoma. In previous studies, we had shown that TRAIL and HDACi were synergistic in inducing apoptosis in medulloblastoma and Ewing's sarcoma. In the present study, we demonstrate that HDACi cooperated with TRAIL in eliciting cell death in osteosarcoma. However, HDACi treatment did not alter or even reduced cell surface expression of TRAIL receptors in the three childhood tumors. In gaining insight into the apoptotic pathway involved in TRAIL sensitization, HDACi were found to potentiate TRAIL-induced caspase-8 activation. Taken together, our findings suggest that HDACi-mediated TRAIL sensitization is not the result of TRAIL receptor upregulation, but the result of a receptor-proximal event in childhood tumor cells.

shRNA-mediated silencing of Gli2 gene inhibits proliferation and sensitizes human hepatocellular carcinoma cells towards TRAIL-induced apoptosis

Aberrant activation of the Hedgehog (Hh) signaling pathway has been reported in various cancer types including hepatocellular carcinoma (HCC). As a key effector of this signaling, Gli2 plays a crucial role in carcinogenesis, including the activation of genes encoding apoptosis inhibitors and cell-cycle regulators. In this study, we examined the role of Gli2 proliferation and survival of HCC cells. First, the expression levels of Hh pathway components were detected in a subset of HCC cell lines. To establish the role of Gli2 in maintaining the tumorigenic properties of HCC cells, we developed small hairpin RNA (shRNA) targeting Gli2 and transfected it into SMMC-7721 cell, which was selected with high level of Hh signaling expression. Next, effects of Gli2 gene silencing, on cell proliferation and on the expression of cell cycle-related proteins were evaluated, then, whether down-regulation of Gli2 renders HCC cell susceptible to TRAIL was examined in vitro. Knockdown of Gli2 inhibited cell proliferation and induced G1 phase arrest of cell cycle in SMMC-7721 cell through down-regulation of cyclin D1, cyclinE2, and up-regulation of p21-WAF1. Also, Gli2 gene siliencing sensitized SMMC-7721 cell to tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis by reducing the expression of the long and short isoform of c-FLIP and Bcl-2, and then augmented the activation of initiator caspases-8/-9 and effector caspases-3, which induces PARP cleavage. In conclusion, our data suggest that Gli2 plays a predominant role in the proliferation and apoptosis resistance of HCC cells, and that knockdown of Gli2 may be a novel anticancer strategy for the treatment of HCC.

Histone deacetylase inhibitors sensitize glioblastoma cells to TRAIL-induced apoptosis by c-myc-mediated downregulation of cFLIP

Glioblastoma is the most common primary brain tumor with a very poor prognosis, calling for novel treatment strategies. Here, we provide first evidence that histone deacetylase inhibitors (HDACI) prime glioblastoma cells for tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) -induced apoptosis at least in part by c-myc-mediated downregulation of cellular FLICE-inhibitory protein (cFLIP). Pretreatment with distinct HDACI (MS275, suberoylanilide hydroxamic acid, valproic acid) significantly enhances TRAIL-induced apoptosis in several glioblastoma cell lines. Monitoring a panel of apoptosis-regulatory proteins revealed that MS275 reduces the expression of cFLIP(L) and cFLIP(S). This leads to decreased recruitment of cFLIP(L) and cFLIP(S) and increased activation of caspase-8 to the TRAIL death-inducing signaling complex, resulting in enhanced cleavage of caspase-8, -9 and -3 and caspase-dependent apoptosis. Also, MS275 promotes TRAIL-triggered processing of Bid, activation of Bax, loss of mitochondrial membrane potential and release of cytochrome c. MS275-mediated downregulation of cFLIP occurs at the mRNA level independent of proteasome- or caspase-mediated degradation, and is preceded by upregulation of nuclear levels of c-myc, a transcriptional repressor of cFLIP. Notably, MS275 causes increased binding of c-myc to the cFLIP promoter and reduces cFLIP promoter activity. Indeed, knockdown of c-myc partially rescues cFLIP(L) from MS275-inferred downregulation and significantly decreases TRAIL- and MS275-induced apoptosis. Also, overexpression of cFLIP(L) or cFLIP(S) significantly reduces MS275- and TRAIL-induced apoptosis. Importantly, MS275 sensitizes primary cultured glioblastoma cells towards TRAIL and cooperates with TRAIL to reduce long-term clonogenic survival of glioblastoma cells and to suppress glioblastoma growth in vivo underscoring the clinical relevance of this approach. Thus, these findings demonstrate that HDACI represent a promising strategy to prime glioblastoma for TRAIL-induced apoptosis by targeting cFLIP.

Targeting the Fas/FasL signaling pathway in cancer therapy

INTRODUCTION

The Fas/FasL system plays a significant role in tumorigenesis. Research has shown that its impairment in cancer cells may lead to apoptosis resistance and contribute to tumor progression. Thus, the development of effective therapies targeting the Fas/FasL system may play an important role in the fight against cancer.

AREAS COVERED

In this review the recent literature on targeting the Fas/FasL system for therapeutic exploitation at different levels is reviewed. Promising pre-clinical approaches and various exceptions are highlighted. The potential of combined therapies is also explored, whereby tumor sensitivity to Fas-mediated apoptosis is restored, before an effective targeted therapy is employed.

EXPERT OPINION

The success of the Fas/FasL system targeting for therapeutics will require a better understanding of the alterations conferring resistance, in order to use the most appropriate sensitizing chemotherapeutic or radiotherapeutic agents in combination with effective targeted therapies.

Influence of five potential anticancer drugs on wnt pathway and cell survival in human biliary tract cancer cells

BACKGROUND

The role of Wnt signalling in carcinogenesis suggests compounds targeting this pathway as potential anti-cancer drugs. Several studies report activation of Wnt signalling in biliary tract cancer (BTC) thus rendering Wnt inhibitory drugs as potential candidates for targeted therapy of this highly chemoresistant disease.

METHODS

In this study we analysed five compounds with suggested inhibitory effects on Wnt signalling (DMAT, FH535, myricetin, quercetin, and TBB) for their cytotoxic efficiency, mode of cell death, time- and cell line-dependent characteristics as well as their effects on Wnt pathway activity in nine different BTC cell lines.

RESULTS

Exposure of cancer cells to different concentrations of the compounds results in a clear dose-dependent reduction of viability for all drugs in the order FH535 > DMAT > TBB > myricetin > quercetin. The first three substances show high cytotoxicity in all tested cell lines, cause a direct cytotoxic effect by induction of apoptosis and inhibit pathway-specific signal transduction in a Wnt transcription factor reporter activity assay. Selected target genes such as growth-promoting cyclin D1 and the cell cycle progression inhibitor p27 are down- and up-regulated after treatment, respectively.

CONCLUSIONS

Taken together, these data demonstrate that the small molecular weight inhibitors DMAT, F535 and TBB have a considerable cytotoxic and possibly Wnt-specific effect on BTC cell lines in vitro. Further in vivo investigation of these drugs as well as of new Wnt inhibitors may provide a promising approach for targeted therapy of this difficult-to-treat tumour.

Mechanisms of resistance to histone deacetylase inhibitors

Histone deacetylase (HDAC) inhibitors are a new class of anticancer agents. HDAC inhibitors induce acetylation of histones and nonhistone proteins which are involved in regulation of gene expression and in various cellular pathways including cell growth arrest, differentiation, DNA damage and repair, redox signaling, and apoptosis (Marks, 2010). The U.S. Food and Drug Administration has approved two HDAC inhibitors, vorinostat and romidepsin, for the treatment of cutaneous T-cell lymphoma (Duvic & Vu, 2007; Grant et al., 2010; Marks & Breslow, 2007). Over 20 chemically different HDAC inhibitors are in clinical trials for hematological malignancies and solid tumors. This review considers the mechanisms of resistance to HDAC inhibitors that have been identified which account for the selective effects of these agents in inducing cancer but not normal cell death. These mechanisms, such as functioning Chk1, high levels of thioredoxin, or the prosurvival BCL-2, may also contribute to resistance of cancer cells to HDAC inhibitors.

Dual targeting of mTORC1/C2 complexes enhances histone deacetylase inhibitor-mediated anti-tumor efficacy in primary HCC cancer in vitro and in vivo

BACKGROUND & AIMS

The mammalian target of rapamycin (mTOR) plays a pivotal role in hepatocellular carcinoma (HCC). Previous studies indicated that inhibition of mTORC1 enhanced histone deacetylase inhibitors (HDACis)-mediated anti-tumor activity, accompanied with feedback activation of AKT. Therefore, dual targeting of mTORC1/C2 should be more efficient in suppressing AKT activity and in enhancing the anti-tumor activity of HDACi in HCC.

METHODS

The interactions between mTOR kinase inhibitors (mTORKis) (i.e., Pp242, AZD8055, OSI027) and HDACis (i.e., SAHA, LBH589) were examined in vitro using HCC cell lines and in vivo using patient-derived primary HCC xenografts on SCID mice.

RESULTS

mTORKis significantly enhanced HDACi-induced apoptosis in HCC cells. The inhibition of both mTORC1/2 not only efficiently blocked mTORC1 signaling, but also abrogated AKT-feedback activation caused by selective mTORC1 inhibition. The co-treatment of mTORKi and HDACi further inhibited AKT signaling and upregulated Bim. Dysfunction of mTORC2 by shRNA significantly lowered the threshold of HDACi-induced cytotoxicity by abrogating AKT activation. Knockdown of AKT1 sensitized Pp242/HDACi-induced apoptosis and ectopic expression of constitutively active AKT1 abrogated the combination-induced cytotoxicity, indicating AKT plays a vital role in the combination-induced effects. Knockdown of Bim prevented Pp242/HDACis-induced cytotoxicity in HCC. Lastly, in vivo studies indicated that the combination of AZD8055 and SAHA almost completely inhibited tumor-growth, without obvious adverse effects, by abrogating AKT and upregulating Bim; while either agent alone shows only 30% inhibition in primary HCC xenografts.

CONCLUSIONS

Our findings suggest that a combining-regimen of mTORKi and HDACi may be an effective therapeutic strategy for HCC.

Vorinostat/SAHA-induced apoptosis in malignant mesothelioma is FLIP/caspase 8-dependent and HR23B-independent

INTRODUCTION

Malignant pleural mesothelioma (MPM) is a rapidly fatal malignancy that is increasing in incidence. The caspase 8 inhibitor FLIP is an anti-apoptotic protein over-expressed in several cancer types including MPM. The histone deacetylase (HDAC) inhibitor Vorinostat (SAHA) is currently being evaluated in relapsed mesothelioma. We examined the roles of FLIP and caspase 8 in regulating SAHA-induced apoptosis in MPM.

METHODS

The mechanism of SAHA-induced apoptosis was assessed in 7 MPM cell lines and in a multicellular spheroid model. SiRNA and overexpression approaches were used, and cell death was assessed by flow cytometry, Western blotting and clonogenic assays.

RESULTS

RNAi-mediated FLIP silencing resulted in caspase 8-dependent apoptosis in MPM cell line models. SAHA potently down-regulated FLIP protein expression in all 7 MPM cell lines and in a multicellular spheroid model of MPM. In 6/7 MPM cell lines, SAHA treatment resulted in significant levels of apoptosis induction. Moreover, this apoptosis was caspase 8-dependent in all six sensitive cell lines. SAHA-induced apoptosis was also inhibited by stable FLIP overexpression. In contrast, down-regulation of HR23B, a candidate predictive biomarker for HDAC inhibitors, significantly inhibited SAHA-induced apoptosis in only 1/6 SAHA-sensitive MPM cell lines. Analysis of MPM patient samples demonstrated significant inter-patient variations in FLIP and caspase 8 expressions. In addition, SAHA enhanced cisplatin-induced apoptosis in a FLIP-dependent manner.

CONCLUSIONS

These results indicate that FLIP is a major target for SAHA in MPM and identifies FLIP, caspase 8 and associated signalling molecules as candidate biomarkers for SAHA in this disease.