Combretastatin A4-induced differential cytotoxicity and reduced metastatic ability by inhibition of AKT function in human gastric cancer cells

Latcripin-7A from Lentinula edodes C91-3 induces apoptosis, autophagy, and cell cycle arrest at G1 phase in human gastric cancer cells via inhibiting PI3K/Akt/mTOR signaling

Gastric cancer (G.C) is one of the most lethal cancer types worldwide. Current treatment requires surgery along with chemotherapy, which causes obstacles for speedy recovery. The discovery of novel drugs is needed for better treatment of G.C with minimum side effects. Latcripin-7A (LP-7A) is a newly discovered peptide extracted from Lentinula edodes. It is recently studied for its anti-cancer activity. In this study, LP-7A was modeled using a phyre2 server. Anti-proliferation effects of LP-7A on G.C cells were examined via CCK-8, colony formation, and morphology assay. Apoptosis of LP-7A treated G.C cells was evaluated via Hoechst Stain, western blot and flow cytometry. Autophagy was assessed via acridine orange staining and western blot. The cell cycle was assessed via flow cytometry assay and western blot. Pathway was studied via western blot and STRING database. Anti-migratory effects of LP-7A treated G.C cells were analyzed via wound healing, western blot, and migration and invasion assay. LP-7A effectively inhibited the growth of G.C cells by inhibiting the PI3K/Akt/mTOR pathway. G.C cells treated with LP-7A arrested the cell cycle at the G1 phase, contributing to the inhibition of migration and invasion. Furthermore, LP-7A induced apoptosis and autophagy in gastric cancer cells. These results indicated that LP-7A is a promising anti-cancer agent. It affected the proliferation and growth of G.C cells (SGC-7901 and BGC-823) by inducing apoptosis, autophagy, and inhibiting cell cycle at the G1 phase in G.C cells.

Self-assembling combretastatin A4 incorporated protamine/nanodiamond hybrids for combined anti-angiogenesis and mild photothermal therapy in liver cancer

Tumor angiogenesis has been identified as an important factor in the development and progression of tumors, and anti-angiogenesis therapy has been recognized as an effective tumor therapy pattern. The unique characteristics of nanodiamonds (NDs) have been explored for photothermal therapy (PTT) against cancer, while the efficiency of mild PTT mediated by bare NDs was limited. The combination of different therapies into a single nanoplatform has shown great potential for synergistic cancer treatment. In this investigation, we integrated hydrophobic antiangiogenesis agent combretastatin A4 (CA4) into the protamine sulfate (PS) functionalized NDs hybrids (NDs@PS) with a noncovalent self-assembling method (CA4-NDs@PS) for potential combined anti-angiogenesis and mild PTT in liver cancer. The resulted CA4-NDs@PS NDs exhibited high drug loading ability, good dispersibility and colloidal stability. The near-infrared (NIR) laser irradiation could trigger the release of CA4 from CA4-NDs@PS NDs and elevate the temperature of CA4-NDs@PS NDs aqueous solution.In vitroresults illustrated that CA4-NDs@PS coupled with laser irradiation could remarkably enhance HepG-2 cells killing efficiency, leading to an enhanced photocytotoxicity. Furthermore,in vivoexperiments revealed that CA4-NDs@PS exhibited a highly synergistic anticancer efficacy with NIR laser irradiation in HepG-2 tumor-bearing mice. Altogether, our present study fabricated a novel NDs@PS-based nanoplatform for combined anti-tumor angiogenesis and mild PTT against liver cancer.

The novel ALK inhibitor ZX-29 induces apoptosis through inhibiting ALK and inducing ROS-mediated endoplasmic reticulum stress in Karpas299 cells

It is a well-known fact that 60%-85% of anaplastic large cell lymphoma (ALCL) is mainly driven by the anaplastic lymphoma kinase (ALK) fusion protein. Although ALK-positive ALCL patients respond significantly to ALK inhibitors, the development of resistance is inevitable, which requires the development of new therapeutic strategies for ALK-positive ALCL. Here, we investigated the anticancer activities of N-(2((5-chloro-2-((2-methoxy-6-(4-methylpiperazin-1-yl)pyridin-3yl)amino)pyrimidin-4-yl)amino)phenyl)methanesulfonamide (ZX-29), a newly synthesized ALK inhibitor, against nucleophosmin-ALK-positive cell line Karpas299. We demonstrated that ZX-29 decreased Karpas299 cells growth and had better cytotoxicity than ceritinib, which was mediated through downregulating the expression of ALK and related proteins, inducing cell cycle arrest, and promoting cell apoptosis. Moreover, ZX-29-induced cell apoptosis by inducing endoplasmic reticulum stress (ERS). In addition, ZX-29 increased the generation of reactive oxygen species (ROS), and cells pretreatment with N-acetyl- l-cysteine could attenuate ZX-29-induced cell apoptosis and ERS. Taken together, ZX-29 inhibited Karpas299 cell proliferation and induced apoptosis through inhibiting ALK and its downstream protein expression and inducing ROS-mediated ERS. Therefore, our results provide evidence for a novel antitumor candidate for the further investigation.

1-(4-((5-chloro-4-((2-(isopropylsulfonyl)phenyl)amino)pyrimidin-2-yl)amino)-3-methoxyphenyl)-3-(2-(dimethylamino)ethyl)imidazolidin-2-one (ZX-42), a novel ALK inhibitor, induces apoptosis and protective autophagy in H2228 cells

OBJECTIVES

To examine the antiproliferative effects of 1-(4-((5-chloro-4-((2-(isopropylsulfonyl)phenyl)amino)pyrimidin-2-yl)amino)-3-methoxyphenyl)-3-(2-(dimethylamino)ethyl)imidazolidin-2-one (ZX-42) on the echinoderm microtubule-associated protein-4/anaplastic lymphoma kinase fusion gene (EML4-ALK) positive lung cancer cell line H2228 and its underlying mechanism.

METHODS

The MTT assay was used to study the effect of ZX-42 on H2228 cell growth. Propidium iodide (PI) staining and Western blotting were used to investigate the cell cycle changes. ZX-42-induced cell apoptosis was determined using the Annexin V-FITC/PI (AV/PI) apoptotic assay kit, acridine orange/ethidium bromide (AO/EB) and Hoechst 33258 staining, Rhodamine 123 (Rh 123) fluorescence assay and Western blotting. ZX-42-induced reactive oxygen species (ROS) production was examined by ROS assay kit. Transmission electron microscope, monodansylcadaverine (MDC) staining and the AV/PI apoptotic assay kit were used to demonstrate the relationship between autophagy and apoptosis.

KEY FINDINGS

ZX-42 had good cell viability inhibitory effect on H2228 cells. ZX-42 dramatically inhibited ALK and its downstream pathways. ZX-42 also blocked H2228 cell cycle at G1 phase and then induced apoptosis by activating the mitochondrial pathway. Next, ZX-42 induced the production of ROS, and antioxidant N-acetylcysteine (NAC) reduced ROS production and also decreased apoptotic rates. We also found that ZX-42 induced protective autophagy in H2228 cells.

CONCLUSIONS

In summary, ZX-42 is a novel ALK inhibitor that significantly inhibits the cell viability of H2228 cells and ultimately induces apoptosis through the mitochondrial pathway, in which autophagy plays a protective role. Therefore, inhibition of autophagy might enhance the anti-cancer effect of ZX-42.

Combretastatin analogues in cancer biology: A prospective view

The stilbenoid combretastatin and its derivatives are potent inhibitors of angiogenesis and cell proliferation and induce apoptosis. They disrupt cytoskeletal dynamics and modulate cell morphology, motility, and invasion. Hence they have been viewed as potential as anticancer agents. The impediments of poor solubility and bioavailability and the spontaneous geometric isomerisation of combretastatin into an inactive form have led to intensive efforts towards evolving novel analogues to provide more efficacious biological outcome. Importantly, isomerically stable and biologically active cis-restricted analogues have been synthesised and tested. However, very few analogues have been tested in preclinical models to assess their effects on processes relevant to cancer development and progression. Hence the accent here is on the signalling systems operated by the new derivatives and their biological effects with reference to cancer progression. Combretastatins modulate an extensive network of signalling emphasising their varied versatility. Harnessing these systems and accentuating or counteracting aberrant signalling could open potential avenues of approach to the designing of novel derivatives with enhanced performance. The import of mammalian target of rapamycin pathway, which co-ordinates growth factor receptor signalling, epithelial-mesenchymal transition activation and angiogenic signalling, is emphasised. It may be viewed as a prime target for allosteric inhibition in combination with combretastatin analogues to ascertain their potential in cancer control.

The stilbene derivatives, nucleosides, and nucleosides modified by stilbene derivatives

In this short review, including 187 references, the issues of biological activity of stilbene derivatives and nucleosides and the biological and medicinal potential of fusion of these two classes are discussed. The stilbenes, especially the stilbenoids, and nucleosides are both biologically active. Hybrids formed from binding of these compounds have not yet been broadly studied. However, those that have been investigated exhibit desirable medicinal properties. The review is divided in such parts: I. Derivative of stilbene (biomedical investigations, biological activities in cells, enzymes and hazard), parts II. naturally occurred nucleoside and its derivatives: uridine, thymidine and 5-methyluridine, cytidine, adenosine, guanosine and part III. hybrid molecules- drugs and hybrid molecules- nucleoside - stilbene and its derivative.

Antitubulin sulfonamides: The successful combination of an established drug class and a multifaceted target

Tubulin, the microtubules and their dynamic behavior are amongst the most successful antitumor, antifungal, antiparasitic, and herbicidal drug targets. Sulfonamides are exemplary drugs with applications in the clinic, in veterinary and in the agrochemical industry. This review summarizes the actual state and recent progress of both fields looking from the double point of view of the target and its drugs, with special focus onto the structural aspects. The article starts with a brief description of tubulin structure and its dynamic assembly and disassembly into microtubules and other polymers. Posttranslational modifications and the many cellular means of regulating and modulating tubulin's biology are briefly presented in the tubulin code. Next, the structurally characterized drug binding sites, their occupying drugs and the effects they induce are described, emphasizing on the structural requirements for high potency, selectivity, and low toxicity. The second part starts with a summary of the favorable and highly tunable combination of physical-chemical and biological properties that render sulfonamides a prototypical example of privileged scaffolds with representatives in many therapeutic areas. A complete description of tubulin-binding sulfonamides is provided, covering the different species and drug sites. Some of the antimitotic sulfonamides have met with very successful applications and others less so, thus illustrating the advances, limitations, and future perspectives of the field. All of them combine in a mechanism of action and a clinical outcome that conform efficient drugs.

LP1 from Lentinula edodes C91-3 Induces Autophagy, Apoptosis and Reduces Metastasis in Human Gastric Cancer Cell Line SGC-7901

Present study aimed to elucidate the anticancer effect and the possible molecular mechanism underlying the action of Latcripin 1 (LP1), from the mushroom Lentinula edodes strain C91-3 against gastric cancer cell lines SGC-7901 and BGC-823. Cell viability was measured by Cell Counting Kit-8 (CCK-8); morphological changes were observed by phase contrast microscope; autophagy was determined by transmission electron microscope and fluorescence microscope. Apoptosis and cell cycle were assessed by flow cytometer; wound-healing, transwell migration and invasion assays were performed to investigate the effect of LP1 on gastric cancer cell's migration and invasion. Herein, we found that LP1 resulted in the induction of autophagy by the formation of autophagosomes and conversion of light chain 3 (LC3I into LC3II. LP1 up-regulated the expression level of autophagy-related gene (Atg7, Atg5, Atg12, Atg14) and Beclin1; increased and decreased the expression level of pro-apoptotic (Bax) and anti-apoptotic (Bcl-2) proteins respectively, along with the activation of Caspase-3. At lower-doses, LP1 have shown to arrest cells in the S phase of the cell cycle and decreased the expression level of matrix metalloproteinase MMP-2 and MMP-9. In addition, it has also been shown to regulate the phosphorylation of one of the most hampered gastric cancer pathway, that is, protein kinase B/mammalian target of rapamycin (Akt/mTOR) channel and resulted in cell death. These findings suggested LP1 as a potential natural anti-cancer agent, for exploring the gastric cancer therapies and as a contender for further in vitro and in vivo investigations.

Covalent functionalization of SWCNT with combretastatin A4 for cancer therapy

Single walled carbon nanotubes (SWCNT) are currently under intensive investigation by many labs all over the world for being promising candidates for cancer chemotherapy delivery. On the other hand, combretastatin A4 (CA4) is an anticancer drug that induces cell apoptosis by inhibiting tubulin polymerization. However, it has the disadvantage of low water solubility and the non-selective targeting. Therefore, we aim to create nano-drug from the functionalization of SWCNT covalently with CA4 through click reaction in the presence of tetraethylene glycol linker in order to improve its dispersibility. Scanning electron microscopy and transmission electron microscopy showed good dispersibility of the functionalized SWCNT with diameters of 5-15 nm. Moreover, thermogravometric analysis showed that the efficiency of SWCNT functionalization was around 45%. The in vitro release profile of CA4 at physiological conditions showed that approximately 90% of the loaded drug was released over 50 h. After that MTS test was used to determine the suitable concentration range for the in vitro investigation of the SWCNT-CA4. After that the cytotoxic activity of the SWCNT-CA4 was evaluated by flow cytometry using annexin V/propidium iodide (PI) test. In comparison with free CA4, SWCNT-CA4 treatment demonstrated a significant increase in necrotic cells (around 50%) at the expense of the proportion of the apoptotic cells. Moreover, cell cycle PI test demonstrated that free CA4 and SWCNT-CA4 caused G2/M arrest. However with CA4 treatment higher proportion of cells were in the S-phase while with SWCNT-CA4 treatment greater proportion of cells appeared to be in the G1-phase. Taken together, the provided data suggest that the novel SWCNT-CA4 has a significant anticancer activity that might be superior to that of free CA4.

Synthesis and investigation of new cyclic molecules using the stilbene scaffold

A new approach to the synthesis of asymmetrical cyclic compounds using a stilbene scaffold has been developed. The use of boron trifluoride diethyl etherate as the catalyst, both with and without paraformaldehyde, allows us to obtain new substituted dioxanes, oxanes, cyclic compounds or dimer. The analysis of products was run using experimental and theoretical methods.

A new approach to the synthesis of asymmetrical cyclic compounds using a stilbene scaffold has been developed.

Combretastatin A4 Regulates Proliferation, Migration, Invasion, and Apoptosis of Thyroid Cancer Cells via PI3K/Akt Signaling Pathway

Background

Combretastatin A4 (CA4) is a potential therapeutic candidate for a variety of human cancer treatments. However, the inhibitive effects of CA4 on thyroid cancer cells are still not well-clarified. This study aimed to investigate the potential effect of CA4 on thyroid cancer cells, as well as underlying mechanism.

Material/Methods

Human thyroid papillary carcinoma cell line TPC1 was pre-treated with 5 concentrations of CA4 (0, 1, 2, 5, or 10 μM) for 2 h. Cell proliferation was determined by 3-(4, 5-dimethyl-2- thiazolyl)-2, 5-diphenyl -2-H-tetrazolium bromide (MTT) assay. Cell migration and invasion were detected by a modified Boyden chamber assay. Moreover, cell apoptosis was detected by terminal deoxynucleotidyl (TUNEL) staining assay and flow cytometry method. Western blot analysis was performed to determine the expression changes of epithelial-mesenchymal transition (EMT)-related proteins and phosphatidylinositol-3-kinase/serine/threonine kinase (PI3K/Akt) signaling pathway proteins.

Results

CA4 significantly inhibited the cell proliferation, migration, and invasion, and significantly promoted cell apoptosis in a dose-dependent manner compared with the control group. The EMT-related protein levels of N-Cadherin, Vimentin, Snail1, Slug, Twist1, and ZEB1 were significantly decreased by CA4, while E-cadherin had no significant difference compared with the control group. Moreover, PI3K/Akt signaling pathway protein levels of p-PI3K and p-Akt were significantly decreased, whereas PI3K and Akt had no significant differences compared with the control group.

Conclusions

CA4 can inhibit proliferation, migration, and invasion and promote apoptosis of TPC1 cells. These effects might be through the PI3K/Akt signaling pathway. CA4 may be a potential therapeutic target for the treatment of thyroid cancer.

Combretastatins: In vitro structure-activity relationship, mode of action and current clinical status

For the first time combretastatins were isolated from African willow tree Combretum Caffrum. Subsequent studies have shown the impact of combretastatin A4 phosphate, a water-soluble prodrug, on endothelial cells in tumor vascular system. The same effect was not observed in the vascular system. This selectivity is associated with combretastatins mechanism of action: binding to colchicine domain of microtubules, which affects the cytoskeleton functionality of immature endothelial cells. At the same time, combretastatins directly induce cell death via apoptosis and/or mitotic catastrophe pathways. The combination of both elements makes combretastatin an anticancer compound of high efficiency. The cis-configuration is crucial for its biological activity. To date, many derivatives were synthesized. The attempts to resolve spontaneous isomerization to less active trans-stilbene derivative are still in progress. This issue seems to be overcome by incorporation of the ethene bridge with heterocyclic moiety in combretastatins structure. This modification retains the cis-configuration and prevents isomerization. Nevertheless, combretastatin A4 phosphate disodium is still the most potent compound of this group. The combination therapy, which is the most effective treatment, includes combretastatin A4 phosphate (CA4P) and conventional chemotherapeutics and/or radiotherapy. CA4P is relatively well tolerated giving adverse events of moderate severity, which includes: nausea, vomiting, headache, and tumor pain. The aforementioned effects subside on the day of drug administration or on the following day.

Combretastatins: more than just vascular targeting agents?

Several prodrugs of the naturally occurring combretastatins have undergone extensive clinical evaluation as vascular targeting agents (VTAs). Their increased selectivity toward endothelial cells together with their innate ability to rapidly induce vascular shutdown and inhibit tumor growth at doses up to 10-fold less than the maximum tolerated dose led to the clinical evaluation of combretastatins as VTAs. Tubulin is well established as the molecular target of the combretastatins and the vast majority of its synthetic derivatives. Furthermore, tubulin is a highly validated molecular target of many direct anticancer agents routinely used as front-line chemotherapeutics. The unique vascular targeting properties of the combretastatins have somewhat overshadowed their development as direct anticancer agents and the delineation of the various cell death pathways and anticancer properties associated with such chemotherapeutics. Moreover, the ongoing clinical trial of OXi4503 (combretastatin-A1 diphosphate) together with preliminary preclinical evaluation for the treatment of refractory acute myelogenous leukemia has successfully highlighted both the indirect and direct anticancer properties of combretastatins. In this review, we discuss the development of the combretastatins from nature to the clinic. The various mechanisms underlying combretastatin-induced cell cycle arrest, mitotic catastrophe, cell death, and survival are also reviewed in an attempt to further enhance the clinical prospects of this unique class of VTAs.

Combretastatin A-4 derived imidazoles show cytotoxic, antivascular, and antimetastatic effects based on cytoskeletal reorganisation

INTRODUCTION

Combretastatin A-4 (CA-4) is a natural cis-stilbene which interferes with the cellular tubulin dynamics and which selectively destroys tumour blood vessels. Its pharmacological shortcomings such as insufficient chemical stability, water solubility, and cytotoxicity can be remedied by employing its imidazole derivatives.

METHODS

We studied 11 halogenated imidazole derivatives of CA-4 for their effects on the microtubule and actin cytoskeletons of cancer and endothelial cells and on the propensity of these cells to migrate across tissue barriers or to form blood vessel-like tubular structures.

RESULTS

A series of N-methyl-4-aryl-5-(4-ethoxyphenyl)-imidazoles proved far more efficacious than the lead CA-4 in growth inhibition assays against CA-4-resistant HT-29 colon carcinoma cells and generally more selective for cancer over nonmalignant cells. Et-brimamin (6), the most active compound, inhibited the growth of various cancer cell lines with IC50 (72 h) values in the low nanomolar range. Active imidazoles such as 6 reduced the motility and invasiveness of cancer cells by initiating the formation of actin stress fibres and focal adhesions as a response to the extensive microtubule disruption. The antimetastatic properties were ascertained in 3D-transwell migration assays which simulated the transgression of highly invasive melanoma cells through the extracellular matrix of solid tumours and through the endothelium of blood vessels. The studied imidazoles exhibited vascular-disrupting effects also against tumour xenografts that are refractory to CA-4. They were also less toxic and better tolerated by mice.

CONCLUSIONS

We deem the new imidazoles promising drug candidates for combination regimens with antiangiogenic VEGFR inhibitors.

Nedd4-1 is an exceptional prognostic biomarker for gastric cardia adenocarcinoma and functionally associated with metastasis

Background

Gastric cardia adenocarcinoma (GCA) is the most aggressive subtype of gastric carcinoma. New molecular markers and therapeutic targets are needed for diagnosis, prognosis and treatment of GCA. This study is to establish the E3 ubiquitin ligase Nedd4-1 as a prognostic biomarker to predict the survival and guide the treatment of GCA patients.

Methods

Expression of Nedd4-1 in 214 GCA tumor samples was detected by immunohistochemistry staining (IHC) using tissue microarray assay (TMA). Association of Nedd4-1 with cumulative survival of the TNM stages I-III patients and clinicopathological characteristics was statistically analyzed. The role of Nedd4-1 in gastric cancer cell migration and invasion were determined by transwell and wound healing assays.

Results

Nedd4-1 is overexpressed in 83% of the GCA tumors. The 5-year survival rate in Nedd4-1 negative GCA patients is as high as 96%. Log-rank analysis indicated that overexpression of Nedd4-1 is inversely correlated with cumulative survival (χ² = 21.885, p <0.001). Multivariate logistic regression analysis showed that overexpression of Nedd4-1 is associated with an extremely low GCA survival rate with a hazard ratio (HR) = 0.068 (p = 0.008) in TNM stages I-III patients. Statistical analysis of association of Nedd4-1 overexpression with clinicopathological characteristics revealed that overexpression of Nedd4-1 is tightly associated with TNM stage (p < 0.001). Knockdown of Nedd4-1 in gastric cancer cell lines AGS and N87 dramatically inhibited the gastric cancer cell migration and invasion.

Conclusions

Our results indicate that Nedd4-1 is an exceptional prognostic biomarker for GCA and suggest that Nedd4-1 may play an essential role in GCA metastasis.

Electronic supplementary material

The online version of this article (doi:10.1186/1476-4598-13-248) contains supplementary material, which is available to authorized users.

Cytotoxicity studies of novel combretastatin and pterostilbene derivatives

We synthesised seven 2-aminestilbenes with methoxy substitents in reactions of dinitrostilbenes with sodium azide. In order to study the positioning of the nitro groups, the optimum structure of obtained stilbenes using the DFT B3LYP/6-311++G(2d,p) method was calculated. Very interesting aspect of this regioselectivity reaction is the fact that in all substrates and synthetized compounds the nitro groups in position 2 were not coplanar whereas the para-nitro groups were coplanar with respect to the benzene ring. Due to unique features of stilbene derivatives, such as antitumor agents, we undertook the studies on the biological properties of new stilbene derivatives. Using five cancer cell lines, we investigated the effects of 2-aminestilbenes with methoxy substitents on cell growth.

The Role of PI3K/Akt/mTOR Signaling in Gastric Carcinoma

The phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway is one of the key signaling pathways induced by various receptor-tyrosine kinases. Accumulating evidence shows that this pathway is an important promoter of cell growth, metabolism, survival, metastasis, and resistance to chemotherapy. Genetic alterations in the PI3K/Akt/mTOR pathway in gastric carcinoma have often been demonstrated. Many kinds of molecular targeting therapies are currently undergoing clinical testing in patients with solid tumors. However, with the exception of the ErbB2-targeting antibody, targeting agents, including PI3K/Akt/mTOR inhibitors, have not been approved for treatment of patients with gastric carcinoma. This review summarizes the current knowledge on PI3K/Akt/mTOR signaling in the pathogenesis of gastric carcinoma and the possible therapeutic targets for gastric carcinoma. Improved knowledge of the PI3K/Akt/mTOR pathway in gastric carcinoma will be useful in understanding the mechanisms of tumor development and for identifying ideal targets of anticancer therapy for gastric carcinoma.

Gold(I) biscarbene complexes derived from vascular-disrupting combretastatin A-4 address different targets and show antimetastatic potential

Gold N-heterocyclic carbene (NHC) complexes are an emerging class of anticancer drugs. We present a series of gold(I) biscarbene complexes with NHC ligands derived from the plant metabolite combretastatin A-4 (CA-4) that retain its vascular-disrupting effect, yet address different cellular and protein targets. Unlike CA-4, these complexes did not interfere with tubulin, but with the actin cytoskeleton of endothelial and cancer cells. For the highly metastatic 518A2 melanoma cell line this effect was accompanied by a marked accumulation of cells in the G1 phase of the cell cycle and a suppression of active prometastatic matrix metalloproteinase-2. Despite these mechanistic differences the complexes were as strongly antivascular as CA-4 both in vitro in tube formation assays with human umbilical vein endothelial cells, and in vivo as to blood vessel disruption in the chorioallantoic membrane of chicken eggs. The antiproliferative effect of the new gold biscarbene complexes in a panel of six human cancer cell lines was impressive, with low sub-micromolar IC50 values (72 h) even against CA-4-refractory HT-29 colon and multidrug-resistant MCF-7 breast carcinoma cells. In preliminary studies with a mouse melanoma xenograft model the complexes led to significant decreases in tumor volume while being very well tolerated.

Baicalein inhibits the migration and invasive properties of human hepatoma cells

Flavonoids have been demonstrated to exert health benefits in humans. We investigated whether the flavonoid baicalein would inhibit the adhesion, migration, invasion, and growth of human hepatoma cell lines, and we also investigated its mechanism of action. The separate effects of baicalein and baicalin on the viability of HA22T/VGH and SK-Hep1 cells were investigated for 24h. To evaluate their invasive properties, cells were incubated on matrigel-coated transwell membranes in the presence or absence of baicalein. We examined the effect of baicalein on the adhesion of cells, on the activation of matrix metalloproteinases (MMPs), protein kinase C (PKC), and p38 mitogen-activated protein kinase (MAPK), and on tumor growth in vivo. We observed that baicalein suppresses hepatoma cell growth by 55%, baicalein-treated cells showed lower levels of migration than untreated cells, and cell invasion was significantly reduced to 28%. Incubation of hepatoma cells with baicalein also significantly inhibited cell adhesion to matrigel, collagen I, and gelatin-coated substrate. Baicalein also decreased the gelatinolytic activities of the matrix metalloproteinases MMP-2, MMP-9, and uPA, decreased p50 and p65 nuclear translocation, and decreased phosphorylated I-kappa-B (IKB)-β. In addition, baicalein reduced the phosphorylation levels of PKCα and p38 proteins, which regulate invasion in poorly differentiated hepatoma cells. Finally, when SK-Hep1 cells were grown as xenografts in nude mice, intraperitoneal (i.p.) injection of baicalein induced a significant dose-dependent decrease in tumor growth. These results demonstrate the anticancer properties of baicalein, which include the inhibition of adhesion, invasion, migration, and proliferation of human hepatoma cells in vivo.

Combretastatin A-4 inhibits cell growth and metastasis in bladder cancer cells and retards tumour growth in a murine orthotopic bladder tumour model

BACKGROUND AND PURPOSE

Bladder cancer is a highly recurrent cancer after intravesical therapy, so new drugs are needed to treat this cancer. Hence, we investigated the anti-cancer activity of combretastatin A-4 (CA-4), an anti-tubulin agent, in human bladder cancer cells and in a murine orthotopic bladder tumour model.

EXPERIMENTAL APPROACH

Cytotoxicity of CA-4 was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, propidium iodide (PI) staining assay and clonogenic survival assay. In vivo microtubule assembly assay, cell cycle analyses, Western blot and cell migration assay were used to study the mechanism of CA-4. The effect of intravesical CA-4 therapy on the development of tumours was studied in the murine orthotopic bladder tumour model.

KEY RESULTS

CA-4 inhibited microtubule polymerization in vivo. Cytotoxic IC(50) values of CA-4 in human bladder cancer cells were below 4 nM. Analyses of cell-cycle distribution showed CA-4 obviously induced G(2)-M phase arrest with sub-G(1) formation. The analyses of apoptosis showed that CA-4 induced caspase-3 activation and decreased BubR1 and Bub3 in cancer cells. In addition to apoptosis, CA-4 was also found to induce the formation of multinucleated cells. CA-4 had a significantly reduced cell migration in vitro. Importantly, the in vivo study revealed that intravesical CA-4 therapy retarded the development of murine bladder tumours.

CONCLUSIONS AND IMPLICATIONS

These data demonstrate that CA-4 kills bladder cancer cells by inducing apoptosis and mitotic catastrophe. It inhibited cell migration in vitro and tumour growth in vivo. Hence, CA-4 intravesical therapy could provide another strategy for treating superficial bladder cancers.

Mammalian target of rapamycin pathway promotes tumor-induced angiogenesis in adenoid cystic carcinoma: its suppression by isoliquiritigenin through dual activation of c-Jun NH2-terminal kinase and inhibition of extracellular signal-regulated kinase

Tumor-induced angiogenesis is essential for invasive growth and hematogenous metastasis of adenoid cystic carcinoma (ACC), a highly aggressive neoplasm mostly occurring in salivary glands. Previous studies have indicated that strategies directed against angiogenesis will help develop new therapeutic agents for ACC. The Chinese folk medicine licorice has been used for years as a natural remedy for angiogenesis-related diseases. In this study, we examined the effects of isoliquiritigenin (ISL), a flavonoid isolated from licorice, on the growth and viability of ACC cells and observed a concentration-dependent (0-20 microM) inhibition of cell growth without cell death at 24 h. In a further mimic coculture study, ISL effectively suppressed the ability of ACC cells to induce in vitro proliferation, migration, and tube formation of human endothelial hybridoma (EAhy926) cells as well as ex vivo and in vivo angiogenesis, whereas it exerted no effect on EAhy926 cells when added directly or in the presence of vascular endothelial growth factor (VEGF). The data also showed that the specific suppression of tumor angiogenesis by ISL was caused by down-regulation of mammalian target of rapamycin (mTOR) pathway-dependent VEGF production by ACC cells, correlating with concurrent activation of c-Jun NH(2)-terminal kinase (JNK) and inhibition of extracellular signal-regulated kinase (ERK). Most importantly, ISL also significantly decreased microvessel density within xenograft tumors, associating with the reduction of VEGF production and suppression of the mTOR pathway coregulated by JNK and ERK, as revealed by immunohistochemical studies and clustering analysis. Taken together, our results highlight the fact that ISL is a novel inhibitor of tumor angiogenesis and possesses great therapeutic potential for ACC.

An efficient synthetic strategy for obtaining 4-methoxy carbon isotope labeled combretastatin A-4 phosphate and other Z-combretastatins

Human cancer and other clinical trials under development employing combretastatin A-4 phosphate (1b, CA4P) should benefit from the availability of a [(11)C]-labeled derivative for positron emission tomography (PET). In order to obtain a suitable precursor for addition of a [(11)C]methyl group at the penultimate step, several new synthetic pathways to CA4P were evaluated. Geometrical isomerization (Z to E) proved to be a challenge, but it was overcome by development of a new CA4P synthesis suitable for 4-methoxy isotope labeling.

Synthesis and biological evaluation of combretastatin analogs as cell cycle inhibitors of the G1 to S transition in Saccharomyces cerevisiae

A series of Z and E combretastatin A-4 analogs bearing different substituents (OH, F, NO(2), NH(2), B(OH)(2)) in the 3' position were synthesized. These derivatives and Z and E combretastatin A-1 were analysed by monitoring their ability to inhibit cell growth in Saccharomyces cerevisiae. Combretastatin A-1 (2a), A-4 (2b) and compound 2c were found to inhibit yeast growth. Moreover, combretatstatin A-4 (2b) and compound 2c induced a G1 arrest by affecting the synthesis of Clb5 protein, the principal S-phase cyclin. The G1 arrest is coincident with the activation of the stress activated kinase Snf1.

Role of senescence and mitotic catastrophe in cancer therapy

Senescence and mitotic catastrophe (MC) are two distinct crucial non-apoptotic mechanisms, often triggered in cancer cells and tissues in response to anti-cancer drugs. Chemotherapeuticals and myriad other factors induce cell eradication via these routes. While senescence drives the cells to a state of quiescence, MC drives the cells towards death during the course of mitosis. The senescent phenotype distinguishes tumor cells that survived drug exposure but lost the ability to form colonies from those that recover and proliferate after treatment. Although senescent cells do not proliferate, they are metabolically active and may secrete proteins with potential tumor-promoting activities. The other anti-proliferative response of tumor cells is MC that is a form of cell death that results from abnormal mitosis and leads to the formation of interphase cells with multiple micronuclei. Different classes of cytotoxic agents induce MC, but the pathways of abnormal mitosis differ depending on the nature of the inducer and the status of cell-cycle checkpoints. In this review, we compare the two pathways and mention that they are activated to curb the growth of tumors. Altogether, we have highlighted the possibilities of the use of senescence targeting drugs, mitotic kinases and anti-mitotic agents in fabricating novel strategies in cancer control.

Antineoplastic agents. 579. Synthesis and cancer cell growth evaluation of E-stilstatin 3: a resveratrol structural modification

As an extension of our earlier structure/activity investigation of resveratrol (1a) cancer cell growth inhibitory activity compared to the structurally related stilbene combretastatin series (e.g., 2a), an efficient synthesis of E-stilstatin 3 (3a) and its phosphate prodrug 3b was completed. The trans-stilbene 3a was obtained using a convergent synthesis employing a Wittig reaction with phosphonium bromide 9 as the key reaction step. Deprotection of the Z-silyl ether 13 gave E-stilstatin 3 (3a) as the exclusive product. The structure and stereochemistry of 3a was confirmed by X-ray crystal structure determination.

1,4-Diamino-2,3-dicyano-1,4-bis(methylthio)butadiene (U0126) enhances the cytotoxicity of combretastatin A4 independently of mitogen-activated protein kinase kinase

Combretastatin A4 (CA4) is a novel vascular-disrupting agent that has shown promising anticancer effects through its inhibition of microtubule assembly and subsequent disruption of tumor blood flow. In this report, we demonstrate that 1,4-diamino-2,3-dicyano-1,4-bis(methylthio)butadiene (U0126), a selective inhibitor of mitogen-activated protein kinase kinase (MEK), significantly enhances the cytotoxicity of CA4 in BEL-7402 cells, independently of MEK inhibition. This independence is evidenced by the fact that another, more specific MEK inhibitor, PD0325901 [N-[(R)-2,3-dihydroxy-propoxy]-3,4-difluoro-2-[2-fluoro-4-iodo-phenylamino]-benzamide], does not have the same effect as U0126. The disassembled microtubules are able to reassemble in the later stages of CA4 treatment, because of the inactivating glucuronidation of CA4. U0126, but not PD0325901, inhibits CA4 glucuronidation, thereby blocking microtubule reassembly and enhancing CA4-induced G(2)/M cell-cycle arrest. Consistent with this, U0126 significantly enhances CA4-induced cytotoxicity for cells in which CA4 glucuronidation occurs, but not for cells in which such glucuronidation does not occur. These results suggest that great caution should be exercised when interpreting data obtained using U0126 or when CA4 is combined with inhibitors of glucuronidation in clinical practice. It is most important to note that these findings indicate that the combination of CA4 with inhibitors of glucuronidation may be a novel and rational strategy for cancer therapy.