Histone deacetylase inhibitors facilitate dihydroartemisinin-induced apoptosis in liver cancer in vitro and in vivo. PLoS One. 2012;7:e39870. [PMID: 22761917 PMCID: PMC3386188 DOI: 10.1371/journal.pone.0039870]

Anti-malarial drug: the emerging role of artemisinin and its derivatives in liver disease treatment

Artemisinin and its derivatives belong to a family of drugs approved for the treatment of malaria with known clinical safety and efficacy. In addition to its anti-malarial effect, artemisinin displays anti-viral, anti-inflammatory, and anti-cancer effects in vivo and in vitro. Recently, much attention has been paid to the therapeutic role of artemisinin in liver diseases. Several studies suggest that artemisinin and its derivatives can protect the liver through different mechanisms, such as those pertaining to inflammation, proliferation, invasion, metastasis, and induction of apoptosis and autophagy. In this review, we provide a comprehensive discussion of the underlying molecular mechanisms and signaling pathways of artemisinin and its derivatives in treating liver diseases. Further pharmacological research will aid in determining whether artemisinin and its derivatives may serve as promising medicines for the treatment of liver diseases in the future.

Dihydroartemisinin: A Potential Natural Anticancer Drug

Dihydroartemisinin (DHA) is an active metabolite of artemisinin and its derivatives (ARTs), and it is an effective clinical drug widely used to treat malaria. Recently, the anticancer activity of DHA has attracted increasing attention. Nevertheless, there is no systematic summary on the anticancer effects of DHA. Notably, studies have shown that DHA exerts anticancer effects through various molecular mechanisms, such as inhibiting proliferation, inducing apoptosis, inhibiting tumor metastasis and angiogenesis, promoting immune function, inducing autophagy and endoplasmic reticulum (ER) stress. In this review, we comprehensively summarized the latest progress regarding the anticancer activities of DHA in cancer. Importantly, the underlying anticancer molecular mechanisms and pharmacological effects of DHA in vitro and in vivo are the focus of our attention. Interestingly, new methods to improve the solubility and bioavailability of DHA are discussed, which greatly enhance its anticancer efficacy. Remarkably, DHA has synergistic anti-tumor effects with a variety of clinical drugs, and preclinical and clinical studies provide stronger evidence of its anticancer potential. Moreover, this article also gives suggestions for further research on the anticancer effects of DHA. Thus, we hope to provide a strong theoretical support for DHA as an anticancer drug.

Combination Therapies of Artemisinin and its Derivatives as a Viable Approach for Future Cancer Treatment

BACKGROUND

Many anticancer drugs have been developed for clinical usage till now, but the major problem is the development of drug-resistance over a period of time in the treatment of cancer. Anticancer drugs produce huge adverse effects, ultimately leading to death of the patient. Researchers have been focusing on the development of novel molecules with higher efficacy and lower toxicity; the anti-malarial drug artemisinin and its derivatives have exhibited cytotoxic effects.

METHODS

We have done extensive literature search for artemisinin for its new role as anti-cancer agent for future treatment. Last two decades papers were referred for deep understanding to strengthen its role.

RESULT

Literature shows changes at 9, 10 position in the artemisinin structure produces anticancer activity. Artemisinin shows anticancer activity in leukemia, hepatocellular carcinoma, colorectal and breast cancer cell lines. Artemisinin and its derivatives have been studied as combination therapy with several synthetic compounds, RNA interfaces, recombinant proteins and antibodies etc., for synergizing the effect of these drugs. They produce an anticancer effect by causing cell cycle arrest, regulating signaling in apoptosis, angiogenesis and cytotoxicity activity on the steroid receptors. Many novel formulations of artemisinin are being developed in the form of carbon nanotubes, polymer-coated drug particles, etc., for delivering artemisinin, since it has poor water/ oil solubility and is chemically unstable.

CONCLUSION

We have summarize the combination therapies of artemisinin and its derivatives with other anticancer drugs and also focussed on recent developments of different drug delivery systems in the last 10 years. Various reports and clinical trials of artemisinin type drugs indicated selective cytotoxicity along with minimal toxicity thus projecting them as promising anti-cancer agents in future cancer therapies.

Synergistic antitumor activity of artesunate and HDAC inhibitors through elevating heme synthesis via synergistic upregulation of ALAS1 expression

Artemisinin and its derivatives (ARTs) were reported to display heme-dependent antitumor activity. On the other hand, histone deacetylase inhibitors (HDACi) were known to be able to promote heme synthesis in erythroid cells. Nevertheless, the effect of HDACi on heme homeostasis in non-erythrocytes remains unknown. We envisioned that the combination of HDACi and artesunate (ARS) might have synergistic antitumor activity through modulating heme synthesis. In vitro studies revealed that combination of ARS and HDACi exerted synergistic tumor inhibition by inducing cell death. Moreover, this combination exhibited more effective antitumor activity than either ARS or HDACi monotherapy in xenograft models without apparent toxicity. Importantly, mechanistic studies revealed that HDACi coordinated with ARS to increase 5-aminolevulinate synthase (ALAS1) expression, and subsequent heme production, leading to enhanced cytotoxicity of ARS. Notably, knocking down ALAS1 significantly blunted the synergistic effect of ARS and HDACi on tumor inhibition, indicating a critical role of ALAS1 upregulation in mediating ARS cytotoxicity. Collectively, our study revealed the mechanism of synergistic antitumor action of ARS and HDACi. This finding indicates that modulation of heme synthesis pathway by the combination based on ARTs and other heme synthesis modulators represents a promising therapeutic approach to solid tumors.

C3HeB/FeJ Mice mimic many aspects of gene expression and pathobiological features of human hepatocellular carcinoma

Hepatocellular carcinoma (HCC) remains a deadly cancer, underscoring the need for relevant preclinical models. Male C3HeB/FeJ mice model spontaneous HCC with some hepatocarcinogenesis susceptibility loci corresponding to syntenic regions of human chromosomes altered in HCC. We tested other properties of C3HeB/FeJ tumors for similarity to human HCC. C3HeB/FeJ tumors were grossly visible at 4 months of age, with prevalence and size increasing until about 11 months of age. Histologic features shared with human HCC include hepatosteatosis, tumor progression from dysplasia to poorly differentiated, vascular invasion, and trabecular, oncocytic, vacuolar, and clear cell variants. More tumor cells displayed cytoplasmic APE1 staining versus normal liver. Ultrasound effectively detected and monitored tumors, with 85.7% sensitivity. Over 5000 genes were differentially expressed based on the GSE62232 and GSE63898 human HCC datasets. Of these, 158 and 198 genes, respectively, were also differentially expressed in C3HeB/FeJ. Common cancer pathways, cell cycle, p53 signaling and other molecular aspects, were shared between human and mouse differentially expressed genes. We established eigengenes that distinguish HCC from normal liver in the C3HeB/FeJ model and a subset of human HCC. These features extend the relevance and improve the utility of the C3HeB/FeJ line for HCC studies.

Antitumor Research on Artemisinin and Its Bioactive Derivatives

Cancer is the leading cause of human death which seriously threatens human life. The antimalarial drug artemisinin and its derivatives have been discovered with considerable anticancer properties. Simultaneously, a variety of target-selective artemisinin-related compounds with high efficiency have been discovered. Many researches indicated that artemisinin-related compounds have cytotoxic effects against a variety of cancer cells through pleiotropic effects, including inhibiting the proliferation of tumor cells, promoting apoptosis, inducing cell cycle arrest, disrupting cancer invasion and metastasis, preventing angiogenesis, mediating the tumor-related signaling pathways, and regulating tumor microenvironment. More importantly, artemisinins demonstrated minor side effects to normal cells and manifested the ability to overcome multidrug-resistance which is widely observed in cancer patients. Therefore, we concentrated on the new advances and development of artemisinin and its derivatives as potential antitumor agents in recent 5 years. It is our hope that this review could be helpful for further exploration of novel artemisinin-related antitumor agents.

A452, an HDAC6-selective inhibitor, synergistically enhances the anticancer activity of chemotherapeutic agents in colorectal cancer cells

Although histone deacetylase inhibitors (HDACi) alone could be clinically useful, these are most recently used in combination with other anticancer agents in clinical trials for cancer treatment. Recently, we reported the anticancer activity of an HDAC6-selective inhibitor A452 toward various cancer cell types. This study aims to present a potent synergistic antiproliferative effect of A452/anticancer agent treatment in colorectal cancer cells (CRC) cells, independently of the p53 status. A452 in combination with irinotecan, or SAHA is more potent than either drug alone in the apoptotic pathway as evidenced by activated caspase-3 and PARP, increased Bak and pp38, decreased Bcl-xL, pERK, and pAKT, and induced apoptotic cells. Furthermore, A452 enhances DNA damage induced by anticancer agents as indicated by the increased accumulation of γH2AX and the activation of the checkpoint kinase Chk2. The silencing of HDAC6 enhances the cell growth inhibition and cell death caused by anticancer agents. In addition, A452 induces the synergistic suppression of cell migration and invasion. This study suggests a mechanism by which HDAC6-selective inhibition can enhance the efficacy of specific anticancer agents in CRC cells.

Effect of dihydroarteminin combined with siRNA targeting Notch1 on Notch1/c-Myc signaling in T-cell lymphoma cells

The effectiveness of therapy combining dihydroartemisinin (DHA) and small interfering RNA targeting Notch1 (siNotch1) in T-cell lymphoma remains unknown. The present study explored the potential and possible mechanisms of combined dihydroarteminin, and siNotch1 therapy for T-cell lymphoma. It was demonstrated that the viability rates of siRNA-DHA-treated cells was significantly suppressed in comparison with those in control cells, control siRNA cells, siRNA-treated cells and DHA-treated cells (P<0.01). Additionally, there was a significant increase in cell apoptosis of siRNA-DHA-treated cells in comparison with those of control cells, control siRNA cells, siRNA-treated cells, DHA-treated cells (P<0.05). Furthermore, Notch1 and c-Myc mRNA and protein expression were decreased in siRNA-DHA-treated cells (P<0.05). The present study demonstrated that DHA combined with siNotch1 is able to suppress proliferation and promote apoptosis, and downregulate the expression of Notch1 and c-Myc mRNA and protein in T-cell lymphoma cells. Targeting Notch1/c-Myc signaling with siRNA and DHA may represent a novel strategy for treating human T-cell lymphoma.

HDAC inhibitor PAC-320 induces G2/M cell cycle arrest and apoptosis in human prostate cancer

HDAC inhibitors (HDACis) have been demonstrated with profound antiproliferative activities in various tumor types. Previously, we screened several polyoxometalate HDACis based on our p21 luciferase promoter system and demonstrated that such HDACis have antitumor activity. Here, we further investigate the antitumor mechanism of PAC-320, a compound among the polyoxometalates, in human prostate cancer. We demonstrate that PAC-320 is a broad-spectrum HDACi and could inhibit growth of prostate cancer cells in vitro and in vivo. Furthermore, we find that PAC-320 induces cell cycle arrest at G2/M phase and apoptosis. Mechanically, PAC-320 induced cell cycle arrest is associated with an increase of p21 and decrease of cyclin A and cyclin B1, while PAC-320 induced apoptosis is mediated through mitochondria apoptotic pathway and is closely associated with increase of BH3-only proteins Noxa and Hrk. Meanwhile, we demonstrate that p38 MAPK pathway is involved in PAC-320 induced antiproliferative activities in prostate cancer. Taken together, our data indicates that PAC-320 has potent prostate cancer inhibitory activity in vitro and in vivo, which is mediated by G2/M cell cycle arrest and apoptosis.

Dihydroartemisinin inhibits the viability of cervical cancer cells by upregulating caveolin 1 and mitochondrial carrier homolog 2: Involvement of p53 activation and NAD(P)H:quinone oxidoreductase 1 downregulation

Dihydroartemisinin (DHA) has been shown to inhibit the viability of various cancer cells. Previous studies have revealed that the mechanisms involved in the inhibitory effects of DHA are based on theactivation of p53 and the mitochondrial-related cell death pathway. However, the exact association between upstream signaling and the activation of cell death pathway remains unclear. In this study, we found that DHA treatment induced the upregulation of caveolin 1 (Cav1) and mitochondrial carrier homolog 2 (MTCH2) in HeLa cells, and this was associated with the DHA-induced inhibition of cell viability and DHA-induced apoptosis. Additionally, the overexpression of Cav1 and MTCH2 in HeLa cells enhanced the inhibitory effects of DHA on cell viability. Moreover, we also found that the upregulation of Cav1 contributed to the DHA-mediated p53 activation and the downregulation of the redox enzyme, NAD(P)H:quinone oxidoreductase 1 (NQO1), which have been reported to contribute to the activation of the cell death pathway. Of note, we also found that DHA induced the nuclear translocation and accumulation of both Cav1 and p53, indicating a novel potential mechanism, namely the regulation of p53 activation by Cav1. On the whole, our study identified Cav1 and MTCH2 as the molecular targets of DHA and revealed a new link between the upstream Cav1/MTCH2 upregulation and the downstream activation of the cell death pathway involved in the DHA-mediated inhibition of cell viability.

Epigenetic targets in hepatocellular carcinoma cells: identification of chaperone protein complexes with histone deacetylases

AIMS

The study was designed to find out the protein complex(s) associated with HDAC3 in liver cancer using a modified form of affinity purification coupled with a mass spectrometry technique in HepG2 cells. The organ-specific requirement for HDAC1 and HDAC3 during liver formation in zebrafish and their altered expression in liver cancer tissues indicates they are indispensible for hepato-organogenesis and hepatocarcinogenesis. However, how they exert their function is unknown.

MATERIAL & METHODS

HepG2 cells were transfected with either mock or construct-containing HDAC3 using a C-terminal strepIII-HA tag as bait. The bait proteins were purified by double affinity columns and were analyzed on a Thermo LTQ Orbitrap™ (Thermo Scientific, MA, USA) chromatography system.

RESULTS

Affinity purification coupled with mass spectrometry resulted in the identification of 24 putative binders of HDAC3 in HepG2 cells. The majority (83%) of these are novel interactions are reported for the first time in this study.

CONCLUSION

This is the first study reporting the affinity purification and identification of protein complexes with two closely related proteins in one cell line. The novel HDAC1 and HDAC3 complexes identified in HepG2 cells could serve as a platform for the design of future therapeutic medicine for the treatment of liver cancer.

Dihydroartemisinin induces apoptosis preferentially via a Bim-mediated intrinsic pathway in hepatocarcinoma cells

This report is designed to dissect the detail molecular mechanism by which dihydroartemisinin (DHA), a derivative of artemisinin, induces apoptosis in human hepatocellular carcinoma (HCC) cells. DHA induced a loss of the mitochondrial transmemberane potential (ΔΨm), release of cytochrome c, activation of caspases, and externalization of phosphatidylserine indicative of apoptosis induction. Compared with the modest inhibitory effects of silencing Bax, silencing Bak largely prevented DHA-induced ΔΨm collapse and apoptosis though DHA induced a commensurable activation of Bax and Bak, demonstrating a key role of the Bak-mediated intrinsic apoptosis pathway. DHA did not induce Bid cleavage and translocation from cytoplasm to mitochondria and had little effects on the expressions of Puma and Noxa, but did increase Bim and Bak expressions and decrease Mcl-1 expression. Furthermore, the cytotoxicity of DHA was remarkably reduced by silencing Bim, and modestly but significantly reduced by silencing Puma or Noxa. Silencing Bim or Noxa preferentially reduced DHA-induced Bak activation, while silencing Puma preferentially reduced DHA-induced Bax activation, demonstrating that Bim and to a lesser extent Noxa act as upstream mediators to trigger the Bak-mediated intrinsic apoptosis pathway. In addition, silencing Mcl-1 enhanced DHA-induced Bak activation and apoptosis. Taken together, our data demonstrate a crucial role of Bim in preferentially regulating the Bak/Mcl-1 rheostat to mediate DHA-induced apoptosis in HCC cells.

Dihydroartemisinin inhibits glucose uptake and cooperates with glycolysis inhibitor to induce apoptosis in non-small cell lung carcinoma cells

Despite recent advances in the therapy of non-small cell lung cancer (NSCLC), the chemotherapy efficacy against NSCLC is still unsatisfactory. Previous studies show the herbal antimalarial drug dihydroartemisinin (DHA) displays cytotoxic to multiple human tumors. Here, we showed that DHA decreased cell viability and colony formation, induced apoptosis in A549 and PC-9 cells. Additionally, we first revealed DHA inhibited glucose uptake in NSCLC cells. Moreover, glycolytic metabolism was attenuated by DHA, including inhibition of ATP and lactate production. Consequently, we demonstrated that the phosphorylated forms of both S6 ribosomal protein and mechanistic target of rapamycin (mTOR), and GLUT1 levels were abrogated by DHA treatment in NSCLC cells. Furthermore, the upregulation of mTOR activation by high expressed Rheb increased the level of glycolytic metabolism and cell viability inhibited by DHA. These results suggested that DHA-suppressed glycolytic metabolism might be associated with mTOR activation and GLUT1 expression. Besides, we showed GLUT1 overexpression significantly attenuated DHA-triggered NSCLC cells apoptosis. Notably, DHA synergized with 2-Deoxy-D-glucose (2DG, a glycolysis inhibitor) to reduce cell viability and increase cell apoptosis in A549 and PC-9 cells. However, the combination of the two compounds displayed minimal toxicity to WI-38 cells, a normal lung fibroblast cell line. More importantly, 2DG synergistically potentiated DHA-induced activation of caspase-9, -8 and -3, as well as the levels of both cytochrome c and AIF of cytoplasm. However, 2DG failed to increase the reactive oxygen species (ROS) levels elicited by DHA. Overall, the data shown above indicated DHA plus 2DG induced apoptosis was involved in both extrinsic and intrinsic apoptosis pathways in NSCLC cells.

Synergistic induction of apoptosis in A549 cells by dihydroartemisinin and gemcitabine

This report is designed to study the ability of the combined treatment with gemcitabine (Gem) and dihydroartemisinin (DHA) to induce apoptosis in a non-small-cell lung cancer cell line (A549 cells). This combination treatment synergistically inhibited cell growth by inducing apoptosis, and this synergistic action was not associated with reactive oxygen species (ROS). Although either Gem or DHA induced a significant increase in ROS generation, the combination treatment did not further enhance ROS level. Compared with single drugs, the combination treatment significantly potentiated Bak activation, loss of mitochondrial membrane potential, caspase-9 and -3 activation, indicating the important role of the Bak-mediated intrinsic apoptosis pathway in the synergistic action, which was further verified by the significant prevention of the cytotoxicity of the combination treatment by inhibiting one of caspase-9, -3 and Bcl-xL or silencing Bak. In addition, the combination treatment also synergistically activated caspase-8, and inhibition of Fas and caspase-8 presented significant prevention on the cytotoxicity of the combination treatment, indicating that the Fas-caspase-8-mediated extrinsic apoptosis pathway partially participated in the synergistic action. Collectively, the present study demonstrates a strong synergistic action of the combined treatment with Gem and DHA in inducing apoptosis of A549 cells via both the Bak-mediated intrinsic pathway and the Fas-caspase-8-mediated extrinsic pathway.

Epigenetic therapy as a novel approach in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common type of liver malignancy and one with high fatality. Its 5-year survival rate remains low and thus, there is a need for improvement of current treatment strategies as well as development of novel targeted methodologies in order to optimize existing therapeutic protocols. To this end, only recently, it was discovered that its pathophysiology also involves epigenetic alterations in DNA methylation, histone modifications and/or non-coding microRNA patterns. Unlike genetic events, epigenetic alterations are reversible and thus potentially considered to be an alternative option in cancer treatment protocols. In this review, we describe the general characteristics and resulted major alterations of the epigenetic machinery as well as current state of progress of epigenetic therapy (via different single or combinatorial experimental approaches) in HCC.

Ellagic acid normalizes mitochondrial outer membrane permeabilization and attenuates inflammation-mediated cell proliferation in experimental liver cancer

Despite great advances in our understanding of the molecular causes of liver cancer, significant gaps still remain in our knowledge of the disease pathogenesis and development of effective strategies for early diagnosis and treatment. The present study was conducted to evaluate the chemopreventive activity of ellagic acid (EA) against experimental liver cancer in rats. This is the first report that implies a possible role of EA in controlling liver cancer through activation of mitochondrial outer membrane permeability via activating proteins such as Bax, bcl-2, cyt-C, and caspase-9, which play important roles in apoptosis. Downregulation of NF-κB, cyclin D1, cyclin E1, matrix metalloproteinases (MMP)-2, MMP-9, and proliferating cell nuclear antigen (PCNA) were noted in EA-treated experimental rats and controlled inflammation mediated liver cancer when compared to the diethylnitrosamine (DEN)-induced group. Transmission electron microscopy (TEM) analysis of the livers of experimental rats demonstrated that EA treatment renovated its internal architecture. Overall, these results demonstrate the value of molecular approaches in identifying the potential role of EA as an effective chemopreventive agent.

Role of the tissue microenvironment as a therapeutic target in hepatocellular carcinoma

Hepatocellular carcinoma is difficult to treat, primarily because the underlying molecular mechanisms driving clinical outcome are still poorly understood. Growing evidence suggests that the tissue microenvironment has a role in the biological behavior of the tumor. The main clinical issue is to identify the best target for therapeutic approaches. Here, we discuss the hypothesis that the entire tissue microenvironment might be considered as a biological target. However, the tissue microenvironment consists of several cellular and biochemical components, each of which displays a distinct biological activity. We discuss the major components of this environment and consider how they may interact to promote tumor/host crosstalk.

Inhibition of enhancer of zeste homolog 2 (EZH2) expression is associated with decreased tumor cell proliferation, migration, and invasion in endometrial cancer cell lines

OBJECTIVE

To investigate the impact of enhancer of zeste homolog 2 (EZH2) expression on endometrial cancer cell line behavior.

MATERIALS AND METHODS

Enhancer of zeste homolog 2 expression levels were compared between the nonmalignant endometrial cell line T-HESC and 3 endometrial cancer cell lines, ECC-1, RL95-2, and HEC1-A. Stable EZH2 knockdown cell lines were created, and the impact on cellular proliferation, migration, and invasion were determined. Fluorescent activated cell sorting was used to examine effects of EZH2 silencing on cell cycle progression. Enhancer of zeste homolog 2 expression in endometrial cancer tissue specimens was examined using immunohistochemistry. Comparison of differences between control and short-hairpin EZH2 cell lines was performed using the Student t test and the Fischer exact test.

RESULTS

Enhancer of zeste homolog 2 protein expression was increased in all 3 cancer cell lines and human endometrial cancer tissue specimens relative to control. RNA interference of EZH2 expression in ECC-1, RL95-2, and HEC1-A significantly decreased cell proliferation, migration, and invasion. Down-regulation of EZH2 expression resulted in a significant increase in the proportion of cells arrested in the G2/M phase. RNA interference of EZH2 expression was associated with an increase in the expression of Wnt pathway inhibitors sFRP1 and DKK3 and a concomitant decrease in β-catenin. Enhancer of zeste homolog 2 expression in human tissue samples was significantly associated with increased stage, grade, depth of invasion, and nodal metastasis.

CONCLUSIONS

Enhancer of zeste homolog 2 expression is associated with tumor cell proliferation, migration, and invasion in 3 endometrial cancer cell lines as well as with increased stage, grade, depth of invasion, and nodal metastasis in human cancer tissue specimens. Further investigation into this potential therapeutic target is warranted.

Anticancer properties of distinct antimalarial drug classes

We have tested five distinct classes of established and experimental antimalarial drugs for their anticancer potential, using a panel of 91 human cancer lines. Three classes of drugs: artemisinins, synthetic peroxides and DHFR (dihydrofolate reductase) inhibitors effected potent inhibition of proliferation with IC50s in the nM- low µM range, whereas a DHODH (dihydroorotate dehydrogenase) and a putative kinase inhibitor displayed no activity. Furthermore, significant synergies were identified with erlotinib, imatinib, cisplatin, dasatinib and vincristine. Cluster analysis of the antimalarials based on their differential inhibition of the various cancer lines clearly segregated the synthetic peroxides OZ277 and OZ439 from the artemisinin cluster that included artesunate, dihydroartemisinin and artemisone, and from the DHFR inhibitors pyrimethamine and P218 (a parasite DHFR inhibitor), emphasizing their shared mode of action. In order to further understand the basis of the selectivity of these compounds against different cancers, microarray-based gene expression data for 85 of the used cell lines were generated. For each compound, distinct sets of genes were identified whose expression significantly correlated with compound sensitivity. Several of the antimalarials tested in this study have well-established and excellent safety profiles with a plasma exposure, when conservatively used in malaria, that is well above the IC50s that we identified in this study. Given their unique mode of action and potential for unique synergies with established anticancer drugs, our results provide a strong basis to further explore the potential application of these compounds in cancer in pre-clinical or and clinical settings.

Deacetylase-independent function of HDAC3 in transcription and metabolism requires nuclear receptor corepressor

Histone deacetylases (HDACs) are believed to regulate gene transcription by catalyzing deacetylation reactions. HDAC3 depletion in mouse liver upregulates lipogenic genes and results in severe hepatosteatosis. Here we show that pharmacologic HDAC inhibition in primary hepatocytes causes histone hyperacetylation but does not upregulate expression of HDAC3 target genes. Meanwhile, deacetylase-dead HDAC3 mutants can rescue hepatosteatosis and repress lipogenic genes expression in HDAC3-depleted mouse liver, demonstrating that histone acetylation is insufficient to activate gene transcription. Mutations abolishing interactions with the nuclear receptor corepressor (NCOR or SMRT) render HDAC3 nonfunctional in vivo. Additionally, liver-specific knockout of NCOR, but not SMRT, causes metabolic and transcriptomal alterations resembling those of mice without hepatic HDAC3, demonstrating that interaction with NCOR is essential for deacetylase-independent function of HDAC3. These findings highlight nonenzymatic roles of a major HDAC in transcriptional regulation in vivo and warrant reconsideration of the mechanism of action of HDAC inhibitors.

A248, a novel synthetic HDAC inhibitor, induces apoptosis through the inhibition of specificity protein 1 and its downstream proteins in human prostate cancer cells

Histone deacetylase (HDAC) inhibitors are emerging as potent anticancer agents due to their ability to induce apoptosis in various cancer cells, including prostate cancer cells. In the present study, we synthesized a novel HDAC inhibitor, A248, and investigated its apoptotic activity and molecular target in the DU145 and PC3 human prostate cancer cell lines. A248 inhibited the growth of DU145 and PC3 cells and induced apoptosis, as demonstrated by nuclear fragmentation and the accumulation of cells at subG1 phase of cell cycle. The treatment of DU145 and PC3 prostate cancer cells with A248 resulted in the downregulation of specificity protein 1 (Sp1) expression. Since the expression levels of survivin and Mcl-1 depend on Sp1, we also investigated the effects of A248 on survivin and Mcl-1 expression using western blot analysis and immunocytochemistry. The results showed that A248 markedly decreased the expression of survivin and Mcl-1. These data suggest that A248 has apoptotic activity in human prostate cancer cells and that Sp1 may be the molecular target of A248 treatment for inducing apoptosis in prostate cancer cells.

Small interfering RNA targeting Rac1 sensitizes colon cancer to dihydroartemisinin-induced cell cycle arrest and inhibited cell migration by suppressing NFκB activity

Dihydroartemisinin (DHA) has recently shown antitumor activity in various cancer cells. The small GTPase Rac1 regulates many cellular processes, including cytoskeletal reorganization, cell migration, proliferation, and survival. In addition, Rac1 plays a major role in activating NFκB-mediated transcription. Both Rac1 and NFκB regulate many properties of the malignant phenotype, including anchorage-independent proliferation and survival, metastasis, and angiogenesis. In this study, for the first time, we demonstrated that Rac1 knockdown can enhance DHA-induced growth inhibition, cell cycle arrest, apoptosis, and migration in both HCT116 and RKO cell lines in vitro. The mechanism is due partially to DHA, and Rac1 siRNA deactivates NFκB activity, so as to decrease tremendously the expression of its target gene products, such as PCNA, cyclin D1, and CDK4; and increase the expression of p21, cleaved-caspase-3, and cleaved-PARP. In our in vivo studies, DHA also manifested remarkably enhanced antitumor effect when combined with Rac1 siRNA. We concluded that inhibition of NFκB activation is one of the mechanisms that Rac1 siRNA dramatically promotes DHAs antitumor effect on human colon cancer.

Cellular and molecular mechanisms underlie the anti-tumor activities exerted by Walterinnesia aegyptia venom combined with silica nanoparticles against multiple myeloma cancer cell types

Multiple myeloma (MM) is a clonal disease of plasma cells that remains incurable despite the advent of several novel therapeutics. In this study, we aimed to delineate the impact of snake venom extracted from Walterinnesia aegyptia (WEV) alone or in combination with silica nanoparticles (WEV+NP) on primary MM cells isolated from patients diagnosed with MM as well as on two MM cell lines, U266 and RPMI 8226. The IC₅₀ values of WEV and WEV+NP that significantly decreased MM cell viability without affecting the viability of normal peripheral mononuclear cells (PBMCs) were determined to be 25 ng/ml and 10 ng/ml, respectively. Although both WEV (25 ng/ml) and WEV+NP (10 ng/ml) decreased the CD54 surface expression without affecting the expression of CXCR4 (CXCL12 receptor) on MM cells, they significantly reduced the ability of CXC chemokine ligand 12 (CXCL12) to induce actin cytoskeleton rearrangement and the subsequent reduction in chemotaxis. It has been established that the binding of CXCL12 to its receptor CXCR4 activates multiple intracellular signal transduction pathways that regulate MM cell chemotaxis, adhesion, and proliferation. We found that WEV and WEV+NP clearly decreased the CXCL12/CXCR4-mediated activation of AKT, ERK, NFκB and Rho-A using western blot analysis; abrogated the CXCL12-mediated proliferation of MM cells using the CFSE assay; and induced apoptosis in MM cell as determined by PI/annexin V double staining followed by flow cytometry analysis. Monitoring the expression of B-cell CCL/Lymphoma 2 (Bcl-2) family members and their role in apoptosis induction after treatment with WEV or WEV+NP revealed that the combination of WEV with NP robustly decreased the expression of the anti-apoptotic effectors Bcl-2, Bcl_XL and Mcl-1; conversely increased the expression of the pro-apoptotic effectors Bak, Bax and Bim; and altered the mitochondrial membrane potential in MM cells. Taken together, our data reveal the biological effects of WEV and WEV+NP and the underlying mechanisms against myeloma cancer cells.