Rhenium Complexes with Red-Light-Induced Anticancer Activity

Rhenium(I) pyridocarbazole complexes with photoinduced antiproliferative activity are reported. The substitutionally inert complexes induce cell death by singlet oxygen generation upon irradiation with red light (λ ≥ 620 nm), while only weak background cytotoxicity is observed in the dark. Due to their ability to inhibit protein kinases (nanomolar IC₅₀ values against Pim1 at 10 μM ATP), this class of rhenium complexes point into the direction of dual function antiproliferative therapy with a single drug in which photodynamic therapy is combined with the inhibition of cancer related protein kinases.

Mechanism of cellular accumulation of an iridium(III) pentamethylcyclopentadienyl anticancer complex containing a C,N-chelating ligand

The effect of replacement of the N,N-chelating ligand 1,10-phenanthroline (phen) in the Ir(III) pentamethylcyclopentadienyl (Cp*) complex [(η(5)-Cp*)(Ir)(phen)Cl](+) (2) with the C,N-chelating ligand 7,8-benzoquinoline (bq) to give [(η(5)-Cp*)(Ir)(bq)Cl] (1) on the cytotoxicity of these Cp*Ir(III) complexes toward cancer cell lines was investigated. Complex 2 is inactive, similar to other Cp*Ir(III) complexes containing the N,N-chelating ligands. In contrast, a single atom change (C(-) for N) in the chelating N,N ligand resulted in potency in human ovarian carcinoma cisplatin-sensitive A2780 cells, and, strikingly, 1 is active in the cisplatin-resistant human breast cancer MCF-7 and A2780/cisR cells. Replacement of the N,N-chelating ligand with the C,N-chelating ligand gives rise to increased hydrophobicity, leading to higher cellular accumulation, higher DNA-bound iridium in cells and higher cytotoxicity. The pathways involved in cellular accumulation of 1 have been further explored and compared with conventional cisplatin. The results show that both energy-independent passive diffusion and energy-dependent transport play a role in accumulation of 1. Further results were consistent with involvement of p-glycoprotein, multidrug resistance-associated protein 1 and glutathione metabolism in the efflux of 1. In contrast, the internalization of 1 mediated by the endocytotic uptake pathway(s) seems less likely. Understanding the factors which contribute to the mechanism of cellular accumulation of this Ir(III) complex can now lead to the design of structurally similar metal complexes for antitumor chemotherapy.

Epigenetics in hepatocellular carcinoma: An update and future therapy perspectives

Hepatocellular carcinoma (HCC), the predominant form of adult liver malignancies, is a global health concern. Its dismal prognosis has prompted recent significant advances in the understanding of its etiology and pathogenesis. The deregulation of epigenetic mechanisms, which maintain heritable gene expression changes and chromatin organization, is implicated in the development of multiple cancers, including HCC. This review summarizes the current knowledge of epigenetic mechanisms in the pathogenesis of HCC, with an emphasis on HCC mediated by chronic hepatitis B virus infection. This review also discusses the encouraging outcomes and lessons learnt from epigenetic therapies for hematological and other solid cancers, and highlights the future potential of similar therapies in the treatment of HCC.

Self-consumption: the interplay of autophagy and apoptosis

Autophagy and apoptosis control the turnover of organelles and proteins within cells, and of cells within organisms, respectively, and many stress pathways sequentially elicit autophagy, and apoptosis within the same cell. Generally autophagy blocks the induction of apoptosis, and apoptosis-associated caspase activation shuts off the autophagic process. However, in special cases, autophagy or autophagy-relevant proteins may help to induce apoptosis or necrosis, and autophagy has been shown to degrade the cytoplasm excessively, leading to 'autophagic cell death'. The dialogue between autophagy and cell death pathways influences the normal clearance of dying cells, as well as immune recognition of dead cell antigens. Therefore, the disruption of the relationship between autophagy and apoptosis has important pathophysiological consequences.

Synthesis and characterization of two novel dicyanidoargentate(i) complexes containing N-(2-hydroxyethyl)ethylenediamine exhibiting significant biological activity

Two novel cyanido-complexes having very significant antibacterial, antifungal and anticancer activities in vitro were synthesized and characterized using various techniques.

A dual-targeting, apoptosis-inducing organometallic half-sandwich iridium anticancer complex

An iridium(iii) complex [(η⁵-C₅Me₄C₆H₄C₆H₅)Ir(phen)Cl]PF₆(phen = phenanthroline) exhibits dual effects in killing cancer cells causing nuclear DNA damage and mitochondrial dysfunction simultaneously.

Histone deacetylases in cardiac fibrosis: current perspectives for therapy

Cardiac fibrosis is an important pathological feature of cardiac remodeling in heart diseases. The molecular mechanisms of cardiac fibrosis are unknown. Histone deacetylases (HDACs) are enzymes that balance the acetylation activities of histone acetyltransferases on chromatin remodeling and play essential roles in regulating gene transcription. In recent years, the role of HDACs in cardiac fibrosis initiation and progression, as well as the therapeutic effects of HDAC inhibitors, has been well studied. Moreover, numerous studies indicated that HDAC activity is associated with the development and progression of cardiac fibrosis. In this review, the innovative aspects of HDACs are discussed, with respect to biogenesis, their role in cardiac fibrosis. Furthermore, the potential applications of HDAC inhibitors in the treatment of cardiac fibrosis associated with fibroblast activation and proliferation.

Sodium valproate induces cell senescence in human hepatocarcinoma cells

Hepatocarcinogenesis is associated with epigenetic changes, including histone deacetylases (HDACs). Epigenetic modulation by HDAC inhibition is a potentially valuable approach for hepatocellular carcinoma treatment. In present study, we evaluated the anticancer effects of sodium valproate (SVP), a known HDAC inhibitor, in human hepatocarcinoma cells. The results showed SVP inhibited the proliferation of Bel-7402 cells in a dose-dependent manner. Low dose SVP treatment caused a large and flat morphology change, positive SA-β-gal staining, and G0/G1 phase cell cycle arrest in human hepatocarcinoma cells. Low dose SVP treatment also increased acetylation of histone H3 and H4 on p21 promoter, accompanied by up-regulation of p21 and down-regulation of RB phosphorylation. These observations suggested that a low dose of SVP could induce cell senescence in hepatocarcinoma cells, which might correlate with hyperacetylation of histone H3 and H4, up-regulation of p21, and inhibition of RB phosphorylation. Since the effective concentration inducing cell senescence in hepatocarcinoma cells is clinically available, whether a clinical dose of SVP could induce cell senescence in clinical hepatocarcinoma is worthy of further study.

Histone acetylation and arachidonic acid cytotoxicity in HepG2 cells overexpressing CYP2E1

The aim of this work was to assess the role of ethanol-derived acetate and acetate-mediated histone acetylation in arachidonic acid-induced stress in HepG2 cells and cells overexpressing CYP2E1. Cells were grown for 7 days with 1 mM sodium acetate or 100 mM ethanol; their acetylated histone proteins and histone deacetylase 2 expression was quantified using Western blot. Ethanol- or acetate-pretreated cells were also treated for 24 h with 60 μM arachidonic acid to induce oxidative stress. Cytotoxicity was estimated by lactate dehydrogenase release, 3-[4,5-dimethylthiazolyl-2] 2,5-diphenyltetrazolium bromide test, and by DNA damage, while oxidative stress was quantified using dichlorofluorescein diacetate. Cells grown with ethanol or acetate had increased acetylated histone H3 levels in both cell types and elevated acetylated histone H4 levels in cells overexpressing CYP2E1 but not in naïve cells. In cells overexpressing CYP2E1 grown with ethanol, expression of histone deacetylase 2 was reduced by about 40 %. Arachidonic acid altered cell proliferation and was cytotoxic mostly to cells engineered to overexpress CYP2E1 but both effects were significantly lower in cells pretreated with ethanol or acetate. Cytotoxicity was also significantly decreased by 4-methylpyrazole—a CYP2E1 inhibitor and by trichostatin—an inhibitor of histone deacetylases. In cells pretreated with acetate or ethanol, the oxidative stress induced by arachidonic acid was also significantly lower. Our data indicate that histone hyperacetylation may in some extent protect the cells against oxidative stress. It is possible that acetate may act as an antioxidant at histone level. This mechanism may be relevant to alcohol-induced liver injury.

Profile of panobinostat and its potential for treatment in solid tumors: an update

The histone deacetylase (HDAC) inhibitors have emerged as novel therapies for cancer. Panobinostat (LBH 589, Novartis Pharmaceuticals) is a pan-deacetylase inhibitor that is being evaluated in both intravenous and oral formulations across multiple tumor types. Comparable to the other HDACs, panobinostat leads to hyperacetylation of histones and other intracellular proteins, allowing for the expression of otherwise repressed genes, leading to inhibition of cellular proliferation and induction of apoptosis in malignant cells. Panobinostat, analogous to other HDAC inhibitors, also induces apoptosis by directly activating cellular death receptor pathways. Preclinical data suggests that panobinostat has inhibitory activity at nanomolar concentrations and appears to be the most potent clinically available HDAC inhibitor. Here we review the current status of panobinostat and discuss its role in the treatment of solid tumors.

The anti-tumor effects and molecular mechanisms of suberoylanilide hydroxamic acid (SAHA) on the aggressive phenotypes of ovarian carcinoma cells

Histone deacetylase inhibitors (HDACi), such as suberoylanilide hydroxamic acid (SAHA), have been shown to act selectively on gene expression, and are potent inducers of growth arrest, differentiation and apoptosis in various types of cancers in vitro and in vivo. This study aimed to elucidate the anti-tumor effects and molecular mechanisms of SAHA on the aggressive phenotypes of ovarian carcinoma. Two pairs of cell lines (SKOV3 and SKOV3/DDP; HO8910 and HO8910-PM) were exposed to SAHA treatment, and the effects on acetyl-Histone H3 and H4 expression levels were analyzed and compared against the aggressive behaviors of ovarian carcinoma. Our results showed that SAHA suppressed proliferation in both a concentration- and time-dependent manner in all four cell lines; induced S/G₂ arrest in SKOV3 and SKOV3/DDP cells; and conversely, induced G₁ arrest in HO8910 and HO8910-PM cells. SAHA treatment induced apoptosis and reduced migration, invasion and lamellipodia formation in the ovarian carcinoma cells; furthermore, SAHA decreased expression of Cyclin B1 and CDC2P34 mRNA, and downregulated CDC2P34, Erk1/2, CyclinB1 and MMP-9 proteins. In contrast, SAHA increased expression of Caspase-3, p21 and p53 mRNA, and upregulated acetyl-Histones H3 and H4, Caspase-8, and p53 proteins. Basal acetylation of histone H3 and H4 was higher in ovarian carcinoma compared to normal ovarian tissues and benign ovarian tumors, and in borderline tumor than in normal ovarian tissues, and was positively correlated with differentiation and expression of the proliferative marker, Ki-67 (P < 0.05). We suggest that SAHA may suppress growth, migration and invasion in ovarian carcinoma cells, including cisplatin-resistant or highly-invasive ovarian cells, by promoting histone acetylation and modulating their phenotype-related molecules. As such, aberrant acetylation of histone H3 and H4 may play an important role in the carcinogenesis and differentiation of ovarian carcinoma.

An update in the use of antibodies to treat glioblastoma multiforme

Glioblastoma is a deadly brain disease and modest improvement in survival has been made. At initial diagnosis, treatment consists of maximum safe surgical resection, followed by temozolomide and chemoirradiation or adjuvant temozolomide alone. However, these treatments do not improve the prognosis and survival of patients. New treatment strategies are being sought according to the biology of tumors. The epidermal growth factor receptor has been considered as the hallmark in glioma tumors; thereby, some antibodies have been designed to bind to this receptor and block the downstream signaling pathways. Also, it is known that vascularization plays an important role in supplying new vessels to the tumor; therefore, new therapy has been guided to inhibit angiogenic growth factors in order to limit tumor growth. An innovative strategy in the treatment of glial tumors is the use of toxins produced by bacteria, which may be coupled to specific carrier-ligands and used for tumoral targeting. These carrier-ligands provide tumor-selective properties by the recognition of a cell-surface receptor on the tumor cells and promote their binding of the toxin-carrier complex prior to entry into the cell. Here, we reviewed some strategies to improve the management and treatment of glioblastoma and focused on the use of antibodies.

Valproic acid, but not levetiracetam, selectively decreases HDAC7 and HDAC2 expression in human ovarian cancer cells

Histone deacetylases (HDACs) are often overexpressed in cancer cells, leading to altered expression and activity of numerous proteins involved in carcinogenesis. Recent evidence suggests that expression of class I HDACs is increased in ovarian carcinomas and plays a significant role in carcinogenesis and resistance to chemotherapeutic agents. Two compounds, valproic acid (VPA) and levetiracetam (LEV), exhibit HDAC inhibitor (HDACI) activity in various cell types, but data concerning their activity in ovarian cancer are lacking. Here we compared the effects of VPA and LEV as HDACIs, using a human ovarian cancer cell line, OVCAR-3. Cells were cultured with VPA or LEV at concentrations between 1 and 10 mM for 1-24h. HDAC activity was determined by fluorometric assay and confirmed by western blotting. Expression of HDAC genes was determined by real-time PCR and HDAC proteins expression was evaluated by western blotting. Additionally, we used high-performance liquid chromatography to determine whether OVCAR-3 cells can metabolize LEV to its major metabolite, 2-pyrrolidinone-n-butyric acid (PBA), which might exert HDACI activity. LEV, however, had no apparent effect on HDAC activity, or gene and protein expression. The OVCAR-3 cell line was able to metabolize LEV to PBA, but the effect was small. Our observations suggest that VPA should be considered as a possible adjunctive drug in ovarian cancer treatment.

Hepatitis B virus x protein induces autophagy via activating death-associated protein kinase

Hepatitis B virus x protein (HBX), a product of hepatitis B virus (HBV), is a multifunctional protein that regulates viral replication and various cellular functions. Recently, HBX has been shown to induce autophagy; however, the responsible mechanism is not fully known. In this study, we established stable HBX-expressing epithelial Chang cells as the platform to study how HBX induced autophagy. The results showed that the overexpression of HBX resulted in starvation-induced autophagy. HBX-induced autophagy was related to its ability to dephosphorylate/activate death-associated protein kinase (DAPK). The block of DAPK by its siRNA significantly counteracted HBX-mediated autophagy, confirming the positive role of DAPK in this process. HBX also induced Beclin 1, which functions at the downstream of the DAPK-mediated autophagy pathway. Although HBX could activate JNK, a kinase known to participate in autophagy in certain conditions, the change in JNK failed to influence HBX-induced autophagy. In conclusion, HBX induces autophagy via activating DAPK in a pathway related to Beclin 1, but not JNK. This new finding should help us to understand the role of autophagy in HBX-mediated pathogenesis and thus may provide targets for intervening HBX-related disorders.

Role of endoplasmic reticulum stress induction by the plant toxin, persin, in overcoming resistance to the apoptotic effects of tamoxifen in human breast cancer cells

Background:

Persin is a plant toxin that displays synergistic cytotoxicity with tamoxifen in human breast cancer cell lines. Here, we examined the ability of persin to circumvent tamoxifen resistance and delineated the intracellular signalling pathways involved.

Methods:

The induction of apoptosis in tamoxifen-resistant and -sensitive breast cancer cells was measured by flow cytometry following treatment with persin±tamoxifen. Markers of endoplasmic reticulum stress (ERS) were analysed following treatment, and their causal role in mediating persin-induced apoptosis was determined using chemical inhibitors and RNA interference.

Results:

Cells that were resistant to an apoptotic concentration of tamoxifen maintained an apoptotic response to persin. Persin-induced apoptosis was associated with an increase in markers of ERS, that is, CHOP expression and XBP-1 splicing and was decreased by CHOP siRNA. The CASP-4 inhibitor Z-YVAD-FMK markedly inhibited persin-induced apoptosis in both tamoxifen-sensitive and -resistant cells.

Conclusion:

The cytotoxic effects of persin are CASP-4 dependent and mediated by CHOP-dependent and -independent ERS signalling cascades. Increased ERS signalling contributes to persin-induced reversal of tamoxifen resistance.

A phase I study of vorinostat in combination with bortezomib in patients with advanced malignancies

BACKGROUND

A phase I study to assess the maximum-tolerated dose (MTD), dose-limiting toxicity (DLT), pharmacokinetics (PK) and antitumor activity of vorinostat in combination with bortezomib in patients with advanced solid tumors.

METHODS

Patients received vorinostat orally once daily on days 1-14 and bortezomib intravenously on days 1, 4, 8 and 11 of a 21-day cycle. Starting dose (level 1) was vorinostat (400 mg) and bortezomib (0.7 mg/m(2)). Bortezomib dosing was increased using a standard phase I dose-escalation schema. PKs were evaluated during cycle 1.

RESULTS

Twenty-three patients received 57 cycles of treatment on four dose levels ranging from bortezomib 0.7 mg/m(2) to 1.5 mg/m(2). The MTD was established at vorinostat 400 mg daily and bortezomib 1.3 mg/m(2). DLTs consisted of grade 3 fatigue in three patients (1 mg/m(2),1.3 mg/m(2) and 1.5 mg/m(2)) and grade 3 hyponatremia in one patient (1.5 mg/m(2)). The most common grade 1/2 toxicities included nausea (60.9%), fatigue (34.8%), diaphoresis (34.8%), anorexia (30.4%) and constipation (26.1%). Objective partial responses were observed in one patient with NSCLC and in one patient with treatment-refractory soft tissue sarcoma. Bortezomib did not affect the PKs of vorinostat; however, the Cmax and AUC of the acid metabolite were significantly increased on day 2 compared with day 1.

CONCLUSIONS

This combination was generally well-tolerated at doses that achieved clinical benefit. The MTD was established at vorinostat 400 mg daily × 14 days and bortezomib 1.3 mg/m(2) on days 1, 4, 8 and 11 of a 21-day cycle.

LBH589 Inhibits proliferation and metastasis of hepatocellular carcinoma via inhibition of gankyrin/STAT3/Akt pathway

Background

Gankyrin has shown to be overexpressed in human liver cancers and plays a complex role in hepatocarcinogenesis. Panobinostat (LBH589), a new hydroxamic acid-derived histone deacetylase inhibitor has shown promising anticancer effects recently. Here, we investigated the potential of LBH589 as a form of treatment for hepatocellular carcinoma (HCC).

Methods

Gankyrin plasmid was transfected into HCC cells, and the cells were selected for more than 4 weeks by incubation with G418 for overexpression clones. The therapeutic effects of LBH589 were evaluated in vitro and in vivo. Cell proliferation, apoptosis, cell cycle, invasive potential, and epithelial-mesenchy-mal transition (EMT) were examined.

Results

LBH589 significantly inhibited HCC growth and metastasis in vitro and in vivo. Western blotting analysis indicated that LBH589 could decrease the expression of gankyrin and subsequently reduced serine-phosphorylated Akt and tyrosine-phosphorylated STAT3 expression although the total Akt and STAT3 were unaffected. LBH589 inhibited metastasis in vitro via down-regulation of N-cadherin, vimentin, TWIST1, VEGF and up-regulation of E-cadherin. LBH589 also induced apoptosis and G1 phase arrest in HCC cell lines. Ectopic expression of gankyrin attenuated the effects of LBH589, which indicates that gankyrin might play an important role in LBH589 mediated anticancer effects. Lastly, in vivo study indicated that LBH589 inhibited tumor growth and metastasis, without discernable adverse effects comparing to control group, with abrogating gankyrin/STAT3/Akt pathway.

Conclusions

Our results suggested that LBH589 could inhibit HCC growth and metastasis through down-regulating gankyrin/STAT3/Akt pathway. LBH589 may present itself as a novel therapeutic strategy for HCC.

PEGylated liposomal Gemcitabine: insights into a potential breast cancer therapeutic

PURPOSE

Nanoencapsulation of chemotherapeutics is an established method to target breast tumors and has been shown to enhance the efficacy of therapy in various animal models. During the past two decades, the nucleoside analog Gemcitabine has been under investigation to treat both recalcitrant and localized breast cancer, often in combination with other chemotherapeutics. In this study, we investigated the chemotherapeutic efficacy of a novel Gemcitabine-encapsulated liposome previously formulated by our group, GemPo, on both sensitive (4T1) and recalcitrant (MDA-MB-231) breast cancer cell lines.

METHODS

Gemcitabine free drug and liposomal Gemcitabine were compared both in vitro and in vivo using breast cancer models.

RESULTS

We demonstrated that GemPo differently hindered the growth, survival and migration of breast cancer cells, according to their drug sensitivities. Specifically, whereas GemPo was a more potent cytotoxic and apoptotic agent in sensitive breast cancer cells, it more potently inhibited cell migration in the resistant cell line. However, GemPo still acted as a more potent inhibitor of migration, in comparison with free Gemcitabine, irrespective of cell sensitivity. Administration of GemPo in a 4T1-bearing mouse model inhibited tumor growth while increasing mice survival, as compared with free Gemcitabine and a vehicle control. Interestingly, the inclusion of a mitotic inhibitor, Paclitaxel, synergized only with free Gemcitabine in this model, yet was as effective as GemPo alone. However, inclusion of Paclitaxel with GemPo significantly improved mouse survival.

CONCLUSIONS

Our study is the first to demonstrate the pleiotropic effects of Gemcitabine and Gemcitabine-loaded nanoparticles in breast cancer, and opens the door for a novel treatment for breast cancer patients.

Valproic acid inhibits the growth of HeLa cervical cancer cells via caspase-dependent apoptosis

Valproic acid (VPA) as a histone deacetylase (HDAC) inhibitor has an anticancer effect. In the present study, we evaluated the effects of VPA on the growth and death of HeLa cervical cancer cells in relation to reactive oxygen species (ROS) and glutathione (GSH). Dose- and time-dependent growth inhibition was observed in HeLa cells with an IC50 of approximately 10 mM at 24 h. DNA flow cytometric analysis indicated that 10 mM VPA induced a G2/M phase arrest of the cell cycle. This agent also induced apoptosis, which was accompanied by the cleavage of PARP, the activation of caspase-3, -8 and -9, and the loss of mitochondrial membrane potential (MMP; ∆Ψm). All the tested caspase inhibitors significantly prevented HeLa apoptotic cell death induced by VPA, whereas TNF-α intensified the apoptotic cell death. With respect to ROS and GSH levels, VPA increased ROS levels and induced GSH depletion. However, N-acetyl cysteine (NAC; an antioxidant) and L-buthionine sulfoximine (BSO; a GSH synthesis inhibitor) did not significantly affect cell death in VPA-treated HeLa cells. In conclusion, VPA inhibits the growth of HeLa cervical cancer cells via caspase-dependent apoptosis and the growth inhibition is independent of ROS and GSH level changes.

Epigenetics of hepatocellular carcinoma: Role of microRNA

Hepatocellular carcinoma (HCC) represents a major form of primary liver cancer in adults. MicroRNAs (miRs), small non-coding single-stranded RNAs of 19-24 nucleotides in length, negatively regulate the expression of many target genes at the post-transcriptional and/or translational levels and play a critical role in the initiation and progression of HCC. In this review we have summarized the information of aberrantly expressed miRs in HCC, their mechanism of action and relationship to cancer. The recent advances in HCC research reveal that miRs regulate expression of various oncogenes and tumor suppressor genes, thereby contributing to the modulation of diverse biological processes including proliferation, apoptosis, epithelial to mesenchymal transition and metastasis. From a clinical viewpoint, polymorphisms within miR-binding sites are associated with the risk of HCC. Polymorphisms in miR related genes have been shown to correlate with survival or treatment outcome in patients. Furthermore, the review focuses on the potential role of miRs as novel biomarkers and their translational applications for diagnosis and therapy in HCC. With further insights into miR deregulation in HCC, it is expected that novel miR-based therapeutics will arise. Also, we orient the readers to other reviews that may provide better understanding of miR research in HCC.

Combining histone deacetylase inhibitors with MDA-7/IL-24 enhances killing of renal carcinoma cells

In the present study we show that histone deacetylase inhibitors (HDACIs) enhance the anti-tumor effects of melanoma differentiation associated gene-7/interleukin 24 (mda-7/IL-24) in human renal carcinoma cells. Similar data were obtained in other GU tumor cells. Combination of these two agents resulted in increased autophagy that was dependent on expression of ceramide synthase 6, with HDACIs enhancing MDA-7/IL-24 toxicity by increasing generation of ROS and Ca²⁺. Knock down of CD95 protected cells from HDACI and MDA-7/IL-24 lethality. Sorafenib treatment further enhanced (HDACI + MDA-7/IL-24) lethality. Anoikis resistant renal carcinoma cells were more sensitive to MDA-7/IL-24 that correlated with elevated SRC activity and tyrosine phosphorylation of CD95. We employed a recently constructed serotype 5/3 adenovirus, which is more effective than a serotype 5 virus in delivering mda-7/IL-24 to renal carcinoma cells and which conditionally replicates (CR) in tumor cells expressing MDA-7/IL-24 by virtue of placing the adenoviral E1A gene under the control of the cancer-specific promoter progression elevated gene-3 (Ad.5/3-PEG-E1A-mda-7; CRAd.5/3-mda-7, Ad.5/3-CTV), to define efficacy in renal carcinoma cells. Ad.5/3-CTV decreased the growth of renal carcinoma tumors to a significantly greater extent than did a non-replicative virus Ad.5/3-mda-7. In contralateral uninfected renal carcinoma tumors Ad.5/3-CTV also decreased the growth of tumors to a greater extent than did Ad.5/3-mda-7. In summation, our data demonstrates that HDACIs enhance MDA-7/IL-24-mediated toxicity and tumor specific adenoviral delivery and viral replication of mda-7/IL-24 is an effective pre-clinical renal carcinoma therapeutic.

Histone acetyltransferase PCAF up-regulated cell apoptosis in hepatocellular carcinoma via acetylating histone H4 and inactivating AKT signaling

BACKGROUND

PCAF is an important intrinsic histone acetyltransferases. This study tried to establish the effect of PCAF on HCC cell apoptosis.

METHOD

Both in vitro and in vivo experiments including IHC, DAPI staining, caspase 3/7 activity assay, BrdU assay, MTT assay, western immunoblotting and co-immunoprecipitation were used here.

RESULTS

PCAF was found to be expressed at the low level in most of HCC cell lines. PCAF overexpression induced cell apoptosis and growth arrest with increased Histone H4 acetylation and inactivation of AKT signaling in Huh7 and HepG2 cells. The opposite results were obtained by silencing PCAF in Hep3B cells. The co-immunoprecipitation assay confirmed that PCAF protein was bound with histone H4 protein in the nucleus of Hep3B cells. Finally, the in vivo experiment confirmed the findings mentioned-above.

CONCLUSION

These data identified PCAF promotes cell apoptosis and functions as a HCC repressor through acetylating histone H4 and inactivating AKT signaling.

Cetuximab enhances TRAIL-induced gastric cancer cell apoptosis by promoting DISC formation in lipid rafts

TRAIL is a member of the tumor necrosis factor family that selectively induces cancer cell apoptosis. However, gastric cancer cells are insensitive to TRAIL. Our and others studies showed that the inhibition of EGFR pathway activation could increase the sensitivity of TRAIL in cancer cells. But the detailed mechanism is not fully understood. In the present study, compared with TRAIL or cetuximab (an anti-EGFR monoclonal antibody) alone, treatment with the TRAIL/cetuximab combination significantly promoted death receptor 4 (DR4) clustering as well as the translocation of both DR4 and Fas-associated death domain-containing protein (FADD) into lipid rafts. This in turn resulted in caspase-8 cleavage and the formation of the death-inducing signaling complex (DISC) in these lipid rafts. Cholesterol-depletion with methyl-β-cyclodextrin partially prevented DR4 clustering and DISC formation, and thus partially reversed apoptosis induced by the TRAIL/cetuximab dual treatment. These results indicate that cetuximab increases TRAIL-induced gastric cancer cell apoptosis at least partially through the promotion of DISC formation in lipid rafts.

Low-dose paclitaxel inhibits the induction of epidermal-mesenchymal transition in the human cholangiocarcinoma CCKS-1 cell line

Epidermal-mesenchymal transition (EMT) confers an advantage to cancer cells by improving their invasive capacity and metastatic potential. This phenomenon by which epidermal cells change into mesenchymal cells and therefore acquire a higher ability to automaticity, is considered a key process in cancer development. Transforming growth factor-β (TGF-β) is a significant factor for accelerating EMT through the activation of proteins, including members of the Smad pathway. Furthermore, previous studies have shown that low-dose paclitaxel (PTX) inhibits EMT in certain cell lines, including those of cancer cells. The present study determined whether low-dose PTX was able to inhibit EMT in a human cholangiocarcinoma CCKS-1 cell line that had been treated with TGF-β1. First, the cytotoxic concentration of PTX for the CCKS-1 cells was identified to be ~5 nM by MTT assay and dead cell staining. Therefore, the concentrations of PTX were set as 1 nM, 2.5 nM and 5 nM for the subsequent experiments. In the morphological investigation, the CCKS-1 cells changed into a spindle morphology and became separated by the administration of TGF-β1. However, low-dose PTX inhibited these changes and the morphology resembled the control cells in a dose-dependent manner. Similarly, immunofluorescence and immunoblotting investigations revealed that the CCKS-1 cells expressed mesenchymal markers following the administration of TGF-β1. However, low-dose PTX inhibited the expression of the mesenchymal markers and the CCKS-1 cells expressed the epithelial marker, E-cadherin. In particular, a concentration-dependent effect was observed in the immunoblotting experiments. These results show that PTX may be able to inhibit EMT in cancer cells, depending on the dose concentration.

The HDAC inhibitor, panobinostat, induces apoptosis by suppressing the expresssion of specificity protein 1 in oral squamous cell carcinoma

Inhibitors of histone deacetylases (HDACs) represent a novel class of therapeutic anticancer agents. Panobinostat (LBH589) induces apoptosis through the regulation of specificity protein 1 (Sp1) in the oral squamous cell carcinoma (OSCC) cell lines, HN22 and HSC4. In this study, we analyzed the underlying signaling pathways and the mechanisms involved in this process by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay, 4',6-diamidino-2-phenylindole (DAPI) staining, immunocytochemistry and western blot analysis. LBH589 significantly reduced cell growth and the sub-G1 cell population and induced apoptosis. Sp1 protein expression was significantly reduced following treatment with LBH589 in a concentration-dependent manner. Furthermore, LBH589 upregulated the expression of p27 and p21 and downregulated the expression of cyclin D1, myeloid cell leukemia-1 (Mcl-1) and survivin; this led to the activation of apoptotic signaling pathways through the increase of Bax expression and the decrease of Bid and Bcl-xL expression. Treatment with LBH589 also induced the cleavage of caspase-3 and PARP in the HN22 and HSC4 cells. Taken together, our data demonstrate that LBH589 induces the apoptosis of OSCC cells by suppressing Sp1 expression, indicating that LBH589 may be a promising chemotherapeutic agent for the treatment of OSCC.

Current understanding of the molecular biology of pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors (PanNETs) are complicated and often deadly neoplasms. A recent increased understanding of their molecular biology has contributed to expanded treatment options. DNA sequencing of samples derived from patients with PanNETs and rare genetic syndromes such as multiple endocrine neoplasia type 1 (MEN1) and Von Hippel-Lindau (VHL) syndrome reveals the involvement of MEN1, DAXX/ATRX, and the mammalian target of rapamycin (mTOR) pathways in PanNET tumorigenesis. Gene knock-out/knock-in studies indicate that inactivation of factors including MEN1 and abnormal PI3K/mTOR signaling uncouples endocrine cell cycle progression from the control of environmental cues such as glucose, leading to islet cell overgrowth. In addition, accumulating evidence suggests that further impairment of endothelial-endocrine cell interactions contributes to tumor invasion and metastasis. Recent phase III clinical trials have shown that therapeutic interventions, such as sunitinib and everolimus, targeting those signal transduction pathways improve disease-free survival rates. Yet, cure in the setting of advanced disease remains elusive. Further advances in our understanding of the molecular mechanisms of PanNETs and improved preclinical models will assist in developing personalized therapy utilizing novel drugs to provide prolonged control or even cure the disease.

Polymorphisms in histone deacetylases improve the predictive value of IL-28B for chronic hepatitis C therapy

Histone deacetylases (HDACs) influence many cellular processes, including the modulation of signal transducer and activator of transcription activity (STAT) in response to interferon (IFN). To identify genetic markers that help optimize the IL-28B prediction of chronic hepatitis C (CHC) sustained virological response (SVR), we evaluated 27 single-nucleotide polymorphisms (SNPs) in HDAC1-11. Three SNPs, rs3778216, rs976552 and rs368328 in HDAC2, HDAC3 and HDAC5, respectively, were independently associated with SVR (P<0.05). The addition of these three HDAC's SNPs to the IL-28B predictive model (area under the curve (AUC)=0.630) rendered an important improvement of AUC-receiver operating characteristic value (AUC=0.747, P=0.021). Chi-squared Automatic Interaction Detector (CHAID) analysis denoted the significance of the rs3778216 C/C genotype in identifying a group of good responders despite carrying IL-28B T allele (79.2% of SVR), whereas HDAC5 G allele characterized a subgroup with poor response rate (25.5%). However, HDAC3 rs976552 did not display a relevant role for the hierarchical classification of patients. Variables related to SVR in hepatitis C virus genotype 1 (HCV-1) cohort were the same of those obtained for the overall population. Interestingly, in non-HCV-1 patients (n=56) the HDAC2 C/C genotype was the unique predictive variable related to SVR (AUC=0.733, P<0.007). Thus, these preliminary results suggest the potential usefulness of combined IL-28B and HDAC genotyping for the CHC patients' classification by likelihood of an SVR.

The emerging role of histone deacetylase (HDAC) inhibitors in urological cancers

WHAT'S KNOWN ON THE SUBJECT? AND WHAT DOES THE STUDY ADD?: A growing body of evidence supports the anti-cancer effect of histone deacetylase inhibitors (HDACi) in vitro, via multiple pathways, and many Phase I clinical trials have shown them to be well-tolerated in a range of malignancies. Combined therapies, including with radiation, present an exciting area of current and planned study. This review summarises the evidence to date, including pre-clinical data and clinical trials, of the anti-cancer effect of HDACi in urological cancers. It provides an overview of epigenetics and the mechanisms of action of HDACi. It suggests areas of future development, including the current challenges for the successful introduction of HDACi into clinical therapy. Epigenetic modifications are known to play a critical role in the development and progression of many cancers. The opposing actions of histone deacetylases (HDACs) and histone acetyltransferases (HATs) modify chromatin and lead to epigenetic gene regulation, in addition to wider effects on non-histone proteins. There is growing interest in the clinical application of HDAC inhibitors (HDACi) in cancer. HDACi have been shown to inhibit cancer cell growth both in vitro and in vivo and recent clinical trials have shown encouraging results in various urological cancers. In this review, we discuss the existing evidence and potential role for HDACi in urological malignancies, including in combined therapies.

The mutational landscape of adenoid cystic carcinoma

Adenoid cystic carcinomas (ACCs) are among the most enigmatic of human malignancies. These aggressive salivary cancers frequently recur and metastasize despite definitive treatment, with no known effective chemotherapy regimen. Here, we determined the ACC mutational landscape and report the exome or whole genome sequences of 60 ACC tumor/normal pairs. These analyses revealed a low exonic somatic mutation rate (0.31 non-silent events/megabase) and wide mutational diversity. Interestingly, mutations selectively involved chromatin state regulators, such as SMARCA2, CREBBP, and KDM6A, suggesting aberrant epigenetic regulation in ACC oncogenesis. Mutations in genes central to DNA damage and protein kinase A signaling also implicate these processes. We observed MYB-NFIB translocations and somatic mutations in MYB-associated genes, solidifying these aberrations as critical events. Lastly, we identified recurrent mutations in the FGF/IGF/PI3K pathway that may potentially offer new avenues for therapy (30%). Collectively, our observations establish a molecular foundation for understanding and exploring new treatments for ACC.

Histone deacetylase inhibitors interact with melanoma differentiation associated-7/interleukin-24 to kill primary human glioblastoma cells

We presently demonstrate that histone deacetylase inhibitors (HDACIs) enhance toxicity of melanoma differentiation-associated gene-7/interleukin 24 (mda-7/IL-24) in invasive primary human glioblastoma multiforme (GBM) cells. Additionally, a method is described to augment the efficacy of adenoviral delivery of mda-7/IL-24 in these cells. HDACIs synergized with melanoma differentiation-associated (MDA)-7/IL-24 killing GBM cells. Enhanced lethality correlated with increased autophagy that was dependent on the expression of ceramide synthase 6. HDACIs interacted with MDA-7/IL-24 prolonging generation of reactive oxygen species and Ca(2+). Quenching of reactive oxygen species and Ca(2+) blocked HDACI and MDA-7/IL-24 killing. In vivo MDA-7/IL-24 prolonged the survival of animals carrying orthotopic tumors, and HDACIs enhanced survival further. A serotype 5/3 adenovirus more effectively delivers mda-7/IL-24 to GBM tumors than a serotype 5 virus. Hence, we constructed a serotype 5/3 adenovirus that conditionally replicates in tumor cells expressing MDA-7/IL-24, in which the adenoviral early region 1A (E1A) gene was driven by the cancer-specific promoter progression elevated gene-3 [Ad.5/3 (INGN 241)-PEG-E1A-mda-7; also called Ad.5/3-CTV (cancer terminator virus)]. Ad.5/3-CTV increased the survival of mice carrying GBM tumors to a significantly greater extent than did a nonreplicative virus Ad.5/3-mda-7. Ad.5/3-CTV exhibited no toxicity in the brains of Syrian hamsters. Collectively our data demonstrate that HDACIs enhance MDA-7/IL-24 lethality, and adenoviral delivery of mda-7/IL-24 combined with tumor-specific viral replication is an effective preclinical GBM therapeutic.

RASSF1A-mediated regulation of AREG via the Hippo pathway in hepatocellular carcinoma

Ras association domain family 1 isoform A (RASSF1A) is a tumor suppressor that is methylated in many human cancers, including hepatocellular carcinoma (HCC). RASSF1A has been shown to suppress tumors via activation of the Hippo tumor suppressor pathway, including mammalian STE20-like kinase (MST). Amphiregulin (AREG), a target gene for Yes-associated protein (YAP), is a known oncogenic component of the Hippo pathway; however, the tumor-suppressive effect of RASSF1A on AREG in regard to regulation of the Hippo pathway remains unclear in HCC. Overexpression of RASSF1A in HCC cells, which lack functional RASSF1A, significantly inhibited cell proliferation and induced apoptosis by activating the Hippo pathway. Consequently, overexpression of RASSF1A inhibited the oncogenic functions of YAP, leading to a significant reduction in AREG secretion via regulation of the Hippo pathway. In human specimens, greater expression of RASSF1A was observed in chronic hepatitis/cirrhosis than in HCC, whereas expression of YAP and AREG was higher in 81% and 86% of HCC than in corresponding chronic hepatitis/cirrhosis, respectively. Furthermore, RASSF1A protein gradually decreased as multistep hepatocarcinogenesis progressed from chronic hepatitis/cirrhosis dysplastic nodules toward HCC, whereas the protein expression of YAP and AREG gradually increased. These findings provide mechanistic insight into the regulation of YAP and AREG by RASSF1A in human multistep hepatocarcinogenesis.

The evolving landscape of therapeutic drug development for hepatocellular carcinoma

Currently, only one drug, sorafenib, is FDA approved for the treatment of advanced hepatocellular carcinoma (HCC), achieving modest objective response rates while still conferring an overall survival benefit. Unlike other solid tumors, no oncogenic addiction loops have been validated as clinically actionable targets in HCC. Outcomes of HCC could potentially be improved if critical molecular subclasses with distinct therapeutic vulnerabilities can be identified, biomarkers that predict recurrence or progression early can be determined and key epigenetic, genetic or microenvironment drivers that determine best response to a specific targeting treatment can be uncovered. Our group and others have examined the molecular heterogeneity of hepatocellular carcinoma. We have developed a panel of patient derived xenograft models to enable focused pre-clinical drug development of rationally designed therapies in specific molecular subgroups. We observed unique patterns, including synergies, of drug activity across our molecularly diverse HCC xenografts, pointing to specific therapeutic vulnerabilities for individual tumors. These efforts inform clinical trial designs and catalyze therapeutic development. It also argues for efficient strategic allocation of patients into appropriate enriched clinical trials. Here, we will discuss some of the recent important therapeutic studies in advanced HCC and also some of the potential strategies to optimize clinical therapeutic development moving forward.

The chemopreventive activity of the butyric acid prodrug tributyrin in experimental rat hepatocarcinogenesis is associated with p53 acetylation and activation of the p53 apoptotic signaling pathway

The reversibility of non-genotoxic phenotypic alterations has been explored in order to develop novel preventive and therapeutic approaches for cancer control. Previously, it has been demonstrated that histone deacetylase (HDAC) inhibitor tributyrin, a butyric acid prodrug, to have chemopreventive effects on rat hepatocarcinogenesis. The goal of this study was to determine molecular mechanisms associated with the chemopreventive activity of tributyrin. Male Wistar rats were allocated randomly to untreated control group and two experimental groups. Rats in the experimental group 1 were treated with maltodextrin (3g/kg body wt), and rats in experimental group 2 were treated with tributyrin (2g/kg body wt) daily for 8 weeks. Two weeks after treatment initiation, rats from experimental groups were subjected to a 'resistant hepatocyte' model of hepatocarcinogenesis. Treatment with tributyrin resulted in lower HDAC activity and Hdac3 and Hdac4 gene expression, and an increase of histone H3 lysine 9 and 18 and histone H4 lysine 16 acetylation as compared with the experimental group 1. In addition to the increase in histone acetylation, tributyrin caused an increase in the acetylation of the nuclear p53 protein. These changes were accompanied by a normalization of the p53-signaling network, particularly by the upregulation of pro-apoptotic genes, and a consequent increase of apoptosis and autophagy in the livers of tributyrin-treated rats. These results indicate that the chemopreventive activity of tributyrin may be related to an increase of histone and p53 acetylation, which could lead to the induction of the p53 apoptotic pathway.

Rhenium complexes with visible-light-induced anticancer activity

Shedding light on the matter: Rhenium(I) indolato complexes with highly potent visible-light-triggered antiproliferative activity (complex 1: EC50 light=0.1 μM vs EC50 dark=100 μM) in 2D- and 3D-organized cancer cells are reported and can be traced back to an efficient generation of singlet oxygen, causing rapid morphological changes and an induction of apoptosis.

Endoplasmic reticulum stress plays a pivotal role in cell death mediated by the pan-deacetylase inhibitor panobinostat in human hepatocellular cancer cells

Panobinostat, a pan-deacetylase inhibitor, represents a novel therapeutic option for cancer diseases. Besides its ability to block histone deacetylases (HDACs) by promoting histone hyperacetylation, panobinostat interferes with several cell death pathways providing a potential efficacy against tumors. We have previously demonstrated that panobinostat has a potent apoptotic activity in vitro and causes a significant growth delay of hepatocellular carcinoma (HCC) tumor xenografts in nude mice models. Here, we show that treatment with panobinostat is able to induce noncanonical apoptotic cell death in HepG2 and in Hep3B cells, involving the endoplasmic reticulum (ER) stress by up-regulation of the molecular chaperone binding immunoglobulin protein/glucose-regulated protein 78, activation of eukaryotic initiation factor 2α-activating transcription factor 4 (tax-responsive enhancer element B67) and inositol requiring 1α-X-box binding protein 1 factors, strong increase and nuclear translocation of the transcription factor C/EBP homologous protein/growth arrest and DNA damage-inducible gene 153, and involvement of c-Jun N-terminal kinase. These signaling cascades culminate into the activation of the ER-located caspase-4/12 and of executioner caspases, which finally lead to cell demise. Our results clearly show that panobinostat induces an alternative ER stress-mediated cell death pathway in HCC cells, independent of the p53 status.

Inactivation of the mTORC1-eukaryotic translation initiation factor 4E pathway alters stress granule formation

Stress granules (SG) are cytoplasmic multimeric RNA bodies that form under stress conditions known to inhibit cap-dependent translation. SG contain translation initiation factors, RNA binding proteins, and signaling molecules. SG are known to inhibit apoptotic pathways, thus contributing to chemo- and radioresistance in tumor cells. However, whether stress granule formation involves oncogenic signaling pathways is currently unknown. Here, we report a novel role of the mTORC1-eukaryotic translation initiation factor 4E (eIF4E) pathway, a key regulator of cap-dependent translation initiation of oncogenic factors, in SG formation. mTORC1 specifically drives the eIF4E-mediated formation of SG through the phosphorylation of 4E-BP1, a key factor known to inhibit formation of the mTORC1-dependent eIF4E-eIF4GI interactions. Disrupting formation of SG by inactivation of mTOR with its specific inhibitor pp242 or by depletion of eIF4E or eIF4GI blocks the SG-associated antiapoptotic p21 pathway. Finally, pp242 sensitizes cancer cells to death in vitro and inhibits the growth of chemoresistant tumors in vivo. This work therefore highlights a novel role of the oncogenic mTORC1-eIF4E pathway, namely, the promotion of formation of antiapoptotic SG.

Combination of Vorinostat and caspase-8 inhibition exhibits high anti-tumoral activity on endometrial cancer cells

Histone deacetylase inhibitors such as Vorinostat display anti-neoplastic activity against a variety of solid tumors. Here, we have investigated the anti-tumoral activity of Vorinostat on endometrial cancer cells. We have found that Vorinostat caused cell growth arrest, loss of clonogenic growth and apoptosis of endometrial cancer cells. Vorinostat-induced the activation of caspase-8 and -9, the initiators caspases of the extrinsic and the intrinsic apoptotic pathways, respectively. Next, we investigated the role of the extrinsic pathway in apoptosis triggered by Vorinostat. We found that Vorinostat caused a dramatic decrease of FLIP mRNA and protein levels. However, overexpression of the long from of FLIP did not block Vorinostat-induced apoptosis. To further investigate the role of extrinsic apoptotic pathway in Vorinostat-induced apoptosis, we performed an shRNA-mediated knock-down of caspase-8. Surprisingly, downregulation of caspase-8 alone caused a marked decrease in clonogenic ability and reduced the growth of endometrial cancer xenografts in vivo, revealing that targeting caspase-8 may be an attractive target for anticancer therapy on endometrial tumors. Furthermore, combination of caspase-8 inhibition and Vorinostat treatment caused an enhancement of apoptotic cell death and a further decrease of clonogenic growth of endometrial cancer cells. More importantly, combination of Vorinostat and caspase-8 inhibition caused a nearly complete inhibition of tumor xenograft growth. Finally, we demonstrate that cell death triggered by Vorinostat alone or in combination with caspase-8 shRNAs was inhibited by the anti-apoptotic protein Bcl-XL. Our results suggest that combinatory therapies using Vorinostat treatment and caspase-8 inhibition can be an effective treatment for endometrial carcinomas.

Intrinsic and extrinsic apoptotic pathway signaling as determinants of histone deacetylase inhibitor antitumor activity

Histone deacetylase inhibitors (HDACi) can elicit a range of biological responses that impede the growth and/or survival of tumor cells. Depending on the physiological context, HDACi can induce apoptosis via two well-defined apoptotic pathways; the intrinsic/mitochondrial pathway and the death receptor (DR)/extrinsic pathway. A number of groups have demonstrated that overexpression of prosurvival Bcl-2 family members significantly reduces HDACi-mediated tumor cell death and therapeutic efficacy in preclinical models. In many cases, HDACi activate the intrinsic pathway via upregulation of a number of proapoptotic BH3-only Bcl-2 family genes including Bim, Bid, and Bmf. Additionally, HDACi can engage the extrinsic pathway through upregulation of DR expression, reductions in c-FLIP, and upregulation of ligands such as TRAIL. Overall, it appears that activation of the intrinsic apoptotic pathway is the predominant mechanism of HDACi-induced tumor cell death; however, the DR pathway may also be engaged, either to amplify the apoptotic signal through the intrinsic pathway or to directly induce cell death.

A novel submicron emulsion system loaded with vincristine-oleic acid ion-pair complex with improved anticancer effect: in vitro and in vivo studies

Background

Vincristine (VCR), which is a widely used antineoplastic drug, was integrated with a submicron-emulsion drug-delivery system to enhance the anticancer effect.

Methods

After the formation of a VCR-oleic acid ion-pair complex (VCR-OA), the VCR-OA-loaded submicron emulsion (VCR-OA-SME), prepared by classical high-pressure homogenization, was characterized and its in vitro anticancer effects were evaluated.

Results

The submicron-emulsion formulation exhibited a homogeneous round shape. The mean particle size, zeta potential, and encapsulation efficiency were 157.6 ± 12.6 nm, −26.5 ± 5.0 mV and 78.64% ± 3.44%, respectively. An in vitro release study of the VCR-OA-SME revealed that 12.4% of the VCR was released within the first 2 hours (initial burst-release phase) and the rest of the drug was detected in the subsequent sustained-release phase. Compared with VCR solution, the pharmacokinetic study of VCR-OA-SME showed relatively longer mean residence time (mean residence time [0–∞] increased from 187.19 to 227.56 minutes), higher maximum concentration (from 252.13 ng/mL to 533.34 ng/mL), and greater area under the curve (area under the curve [0–∞] from 11,417.77 μg/L/minute to 17,164.34 μg/L/minute. Moreover, the VCR-OA-SME exhibited higher cytotoxicity (P < 0.05) on tumor cells by inducing cell arrest in the G2/M phase or even apoptosis (P < 0.05).

Conclusion

The VCR-OA-SME formulation in our study displayed great potential for an anticancer effect for VCR.

Bortezomib and SAHA synergistically induce ROS-driven caspase-dependent apoptosis of nasopharyngeal carcinoma and block replication of Epstein-Barr virus

A novel drug combination of a proteasome inhibitor, bortezomib, and a histone deacetylase inhibitor, suberoylanilide hydroxamic acid (SAHA), was tested in nasopharyngeal carcinoma (NPC), both in vitro and in vivo. Dose-response of different concentrations of bortezomib and SAHA on inhibition of cell proliferation of NPC was determined. Mechanisms of apoptosis and effects on lytic cycle activation of Epstein-Barr virus (EBV) were investigated. Combination of bortezomib and SAHA (bortezomib/SAHA) synergistically induced killing of a panel of NPC cell lines. Pronounced increase in sub-G1, Annexin V-positive, and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive cell populations were detected after treatment with bortezomib/SAHA when compared with either drug alone. Concomitantly, markedly augmented proteolytic cleavage of PARP, caspase-3, -7, -8, and -9, reactive oxygen species (ROS) generation, and caspase-8-dependent histone acetylation were observed. ROS scavenger, N-acetyl cysteine, diminished the apoptotic effects of bortezomib/SAHA, whereas caspase inhibitor Z-VAD-FMK significantly suppressed the apoptosis without decreasing the generation of ROS. Bortezomib inhibited SAHA's induction of EBV replication and abrogated production of infectious viral particles in NPC cells. Furthermore, bortezomib/SAHA potently induced apoptosis and suppressed the growth of NPC xenografts in nude mice. In conclusion, the novel drug combination of bortezomib and SAHA is highly synergistic in the killing of NPC cells in vitro and in vivo. The major mechanism of cell death is ROS-driven caspase-dependent apoptosis. Bortezomib antagonizes SAHA's activation of EBV lytic cycle in NPC cells. This study provides a strong basis for clinical testing of the combination drug regimen in patients with NPC.