Sulforhodamine B colorimetric assay for cytotoxicity screening

pH-Sensitive, N-ethoxybenzylimidazole (NEBI) bifunctional crosslinkers enable triggered release of therapeutics from drug delivery carriers

This paper presents a pH-sensitive bifunctional crosslinker that enables facile conjugation of small molecule therapeutics to macromolecular carriers for use in drug delivery systems. This N-ethoxybenzylimidazole (NEBI) bifunctional crosslinker was designed to exploit mildly acidic, subcellular environments to trigger the release of therapeutics upon internalization in cells. We demonstrate that an analog of doxorubicin (a representative example of an anticancer therapeutic) conjugated to human serum albumin (HSA, a representative example of a macromolecular carrier) via this NEBI crosslinker can internalize and localize into acidic lysosomes of ovarian cancer cells. Fluorescence imaging and cell viability studies demonstrate that the HSA-NEBI-doxorubicin conjugate exhibited improved uptake and cytotoxic activity compared to the unconjugated doxorubicin analog. The pH-sensitive NEBI group was also shown to be relatively stable to biologically-relevant metal Lewis acids and to serum proteins, supporting that these bifunctional crosslinkers may be useful for constructing drug delivery systems that will be stable in biological fluids such as blood.

MiRNA profile associated with replicative senescence, extended cell culture, and ectopic telomerase expression in human foreskin fibroblasts

Senescence is a highly regulated process that limits cellular replication by enforcing a G1 arrest in response to various stimuli. Replicative senescence occurs in response to telomeric DNA erosion, and telomerase expression can offset replicative senescence leading to immortalization of many human cells. Limited data exists regarding changes of microRNA (miRNA) expression during senescence in human cells and no reports correlate telomerase expression with regulation of senescence-related miRNAs. We used miRNA microarrays to provide a detailed account of miRNA profiles for early passage and senescent human foreskin (BJ) fibroblasts as well as early and late passage immortalized fibroblasts (BJ-hTERT) that stably express the human telomerase reverse transcriptase subunit hTERT. Selected miRNAs that were differentially expressed in senescence were assayed for expression in quiescent cells to identify miRNAs that are specifically associated with senescence-associated growth arrest. From this group of senescence-associated miRNAs, we confirmed the ability of miR-143 to induce growth arrest after ectopic expression in young fibroblasts. Remarkably, miR-143 failed to induce growth arrest in BJ-hTERT cells. Importantly, the comparison of late passage immortalized fibroblasts to senescent wild type fibroblasts reveals that miR-146a, a miRNA with a validated role in regulating the senescence associated secretory pathway, is also regulated during extended cell culture independently of senescence. The discovery that miRNA expression is impacted by expression of ectopic hTERT as well as extended passaging in immortalized fibroblasts contributes to a comprehensive understanding of the connections between telomerase expression, senescence and processes of cellular aging.

Anti-inflammatory activities of red curry paste extract on lipopolysaccharide-activated murine macrophage cell line

OBJECTIVE

This study investigated anti-inflammatory and antioxidant activities of an ethanol extract from Thai red curry paste.

METHODS

The RAW264.7 murine macrophage cell line was incubated with the extract (65-260 μg/mL) with or without lipopolysaccharide. The anti-inflammatory activities of the extract were examined by measuring inducible nitric oxide synthase, cyclo-oxygenase-2, tumor necrosis factor-α, and interleukin-6 mRNA and protein level by reverse transcription-polymerase chain reaction, western blotting, and enzyme-linked immunosorbent assay, respectively. Nitric oxide production and intracellular reactive oxygen species generation were determined by the Griess method and fluorescence intensity. The activation of mitogen-activated protein kinases and inhibitor κB were determined by western blot.

RESULTS

Exposure of cells with the extract significantly suppressed lipopolysaccharide-induced nitric oxide production and inducible nitric oxide synthase, cyclo-oxygenase-2, tumor necrosis factor-α, and interleukin-6 expressions (P < 0.05) by dose-dependently without cytotoxic effect. Intracellular reactive oxygen species significantly decreased (P < 0.05) in lipopolysaccharide-induced RAW264.7 cells. The inhibitory effect was mediated partly by inhibiting activation of inhibitor κB-α and mitogen-activated protein kinases.

CONCLUSION

These results suggest that the anti-inflammatory and antioxidant properties of Thai red curry paste stem from bioactive compounds present in the spice and herb constituents. The health benefits of Thai red curry paste warrant further investigations in vivo.

5-Fluorouracil response in a large panel of colorectal cancer cell lines is associated with mismatch repair deficiency

Background:

Colorectal cancer is (CRC) one of the commonest cancers and its therapy is still based on few drugs. Currently, no biological criteria are used to choose the most effective of the established drugs for treatment.

Methods:

A panel of 77 CRC cell lines was tested for sensitivity to 5-fluorouracil (5FU) using the SRB assay. The responses were grouped into three categories and correlated with genetic changes in the cell lines.

Results:

The strongest and most clearcut correlation was between 5-fluorouracil response and replication error status (mismatch repair deficiency). All the other significant correlations (loss of heterozygosity for DCC and mutations in TGFbIIR) are secondary to the association with replication error status.

Interpretation and conclusion:

Our findings validate previous analyses based mainly on clinical data, and indicate that replication error status could be a useful guide to 5-fluorouracil-based CRC therapy. Essentially, all previously described correlations with 5FU response are secondary to the association with replication error status.

Regio- and stereospecific synthesis of mono-beta-d-glucuronic acid derivatives of combretastatin A-1

Synthetic routes have been established for the preparation of regio- and stereoisomerically pure samples of the mono-beta-d-glucuronic acid derivatives of combretastatin A-1, referred to as CA1G1 (5a) and CA1G2 (6a). Judicious choice of protecting groups for the catechol ring was required for the regiospecific introduction of the glucuronic acid moiety. The tosyl group proved advantageous in this regard. The two monoglucuronic acid analogues demonstrate low cytotoxicity (compared to CA1, 2) against selected human cancer cell lines, with CA1G1 being slightly more potent than CA1G2.

Electrospun scaffolds of a polyhydroxyalkanoate consisting of omega-hydroxylpentadecanoate repeat units: fabrication and in vitro biocompatibility studies

Electrospinning was used to fabricate fibrous scaffolds of lipase-catalyzed poly(omega-pentadecalactone) (PPDL). The slow resorbability of this biomaterial is expected to be valuable for tissue-engineering applications requiring long healing times. The effect of solvent systems and instrumental parameters on fiber morphology was investigated. PPDL electrospinning was optimized and defect-free fibers (diameter 410 +/- 150 nm) were obtained by using a mixed three-solvent system. Scaffolds were characterized by scanning electron microscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXS). TGA showed no residual solvent in the scaffolds. DSC and WAXS results indicated that electrospun PPDL is semicrystalline. Biocompatibility of PPDL scaffolds was evaluated through indirect cytotoxicity tests using embryonic rat cardiac H9c2 cells. The ability of PPDL electrospun mats to support cell growth was verified by culturing H9c2 cells onto the scaffold. Cell adhesion, proliferation and morphology were evaluated. The results indicated that PPDL mats are not cytotoxic and they support proliferation of H9c2 cells. The cumulative results of this study suggest further exploration of PPDL fibrous mats as scaffolds for tissue-engineered constructs.

Antiangiogenic activity of sterically stabilized liposomes containing paclitaxel (SSL-PTX): in vitro and in vivo

The purpose of this present study was to evaluate the antiangiogenic activity of sterically stabilized liposomes containing paclitaxel (SSL-PTX). The SSL-PTX was prepared by the thin-film method. The release of paclitaxel from SSL-PTX was analyzed using a dialysis method. The effect of SSL-PTX on endothelial cell proliferation and migration was investigated in vitro. The antitumor and antiangiogenic activity of SSL-PTX was evaluated in MDA-MB-231 tumor xenograft growth in BALB/c nude mice. The release of paclitaxel from SSL-PTX was 22% within 24 h. Our in vitro results indicated that SSL-PTX could effectively inhibit the endothelial cell proliferation and migration at a concentration-dependent manner. We also observed that metronomic SSL-PTX induced marked tumor growth inhibition in MDA-MB-231 xenograft model via the antiangiogenic mechanism, unlike that in paclitaxel injection (Taxol) formulated in Cremophor EL (CrEL). Overall, our results suggested that metronomic chemotherapy with low-dose, CrEL-free SSL-PTX should be feasible and effective.

The detection of dioxin- and estrogen-like pollutants in marine and freshwater fishes cultivated in Pearl River Delta, China

In this study we aimed to assess the dioxin- and estrogen-like activities of contaminants extracted from twenty species of freshwater and seawater fishes, using luciferase reporter assays. Transfected MCF7 cells were treated with sample extracts and luciferase activities were then measured at 24-h of post-treatment. The mean values of the detected dioxin- and estrogen-like activities in the freshwater fishes were 25.3 pg TEQ/g ww and 102.3 pM EEQ/g ww whereas in the seawater fishes, the values were 46.2 pg TEQ/g ww and 118.8 pM EEQ/g ww. Using sample-relevant dosage of estrogen, inductions of cell proliferation markers (i.e. retinoblastoma, cyclin D) and stimulations of cell growth were revealed by Western blotting, colony formation and BrdU uptake assays. A cotreatment with TCDD significantly reduced these effects. Using the sample extracts with different dioxin- and estrogen-like activities, similar observation was revealed. The data highlighted the mixture effect of food contaminants on human health.

Impact of system L amino acid transporter 1 (LAT1) on proliferation of human ovarian cancer cells: a possible target for combination therapy with anti-proliferative aminopeptidase inhibitors

Amino acids activate nutrient signaling via the mammalian target of rapamycin (mTOR), we therefore evaluated the relationship between amino acid transporter gene expression and proliferation in human ovarian cancer cell lines. Expression of three cancer-associated amino acid transporter genes, LAT1, ASCT2 and SN2, was measured by qRT-PCR and Western blot. The effects of silencing the LAT1 gene and its inhibitor BCH on cell growth were evaluated by means of cell proliferation and colony formation assays. The system L amino acid transporter LAT1 was up-regulated in human ovarian cancer SKOV3, IGROV1, A2780, and OVCAR3 cells, compared to normal ovarian epithelial IOSE397 cells, whereas ASCT2 and SN2 were not. BCH reduced phosphorylation of p70S6K, a down-stream effector of mTOR, in SKOV3 and IGROV1 cells, and decreased their proliferation by 30% and 28%, respectively. Although proliferation of SKOV3 (S1) or IGROV1 (I10) cells was unaffected by LAT1-knockdown, plating efficiency in colony formation assays was significantly reduced in SKOV3(S1) and IGROV1(I10) cells to 21% and 52% of the respective plasmid transfected control cells, SKOV3(SC) and IGROV(IC), suggesting that LAT1 affects anchorage-independent cell proliferation. Finally, BCH caused 10.5- and 4.3-fold decrease in the IC(50) value of bestatin, an anti-proliferative aminopeptidase inhibitor, in IGROV1 and A2780 cells, respectively, suggesting that the combined therapy is synergistic. Our findings indicate that LAT1 expression is increased in human ovarian cancer cell lines; LAT1 may be a target for combination therapy with anti-proliferative aminopeptidase inhibitors to combat ovarian cancer.

A novel compound modified from tanshinone inhibits tumor growth in vivo via activation of the intrinsic apoptotic pathway

A novel compound, acetyltanshinone IIA (ATA) was obtained from chemical modifications of tanshinone TIIA (TIIA) isolated from a medicinal plant, Salvia miltiorrhiza. ATA exhibited increased water solubility and stronger apoptotic activity on multiple cancer cell lines than TIIA. ATA displayed a higher growth inhibition ability on breast cancer especially HER2 positive cells than normal cells and it inhibited xenografted tumor growth in mice. Mechanistic studies showed that ATA could induce significant reactive oxygen species (ROS) generation, Bax translocation to mitochondria, resulting in mitochondria damage, cytochrome c release, caspase-3 activation and apoptotic cell death. ATA-mediated ROS production and its downstream apoptotic events could be blocked by an antioxidant agent, propyl gallate, indicating the prominent role of ROS in ATA-induced apoptosis. Overexpression of Bcl-2 protein reduced ATA-induced cell death. In conclusion, ATA is a novel anticancer agent with potent in vitro and in vivo anticancer ability. ROS-mediated Bax activation should be the mechanism by which ATA induces apoptosis and inhibits tumor growth.

Digestive stability and transport of norbixin, a 24-carbon carotenoid, across monolayers of Caco-2 cells

Annatto is a natural pigment widely used in the food industry to add yellow to red colors to dairy and cereal products. Here, the in vitro bioaccessibility and potential bioavailability of norbixin, the abundant 24-carbon carotenoid in annatto, were investigated. Norbixin added to milk was highly stable during simulated digestion, and bile salts enhanced partitioning of this carotenoid in the aqueous fraction during the small intestinal phase of digestion. Apical uptake of norbixin by Caco-2 cells was proportional to the concentration in apical medium, but cellular content increased only slightly after 60 min. Transport of norbixin to the basolateral compartment was maximum at 120 min. Both all-trans and cis isomers of norbixin were present in cells and basolateral medium. The results suggest that ingested norbixin is stable during gastric and small intestinal phases of digestion and that both cis and all-trans isomers are bioavailable.

Depletion of GSH in glial cells induces neurotoxicity: relevance to aging and degenerative neurological diseases

Oxidative stress induced by inhibition of glutathione (GSH) biosynthesis with D,L-buthionine-S,R-sulfoximine (BSO) causes human microglia, human astrocytes, THP-1 cells, and U373 cells to secrete materials toxic to human neuroblastoma SH-SY5Y cells and stimulates them to release TNF-alpha, IL-6, and nitrite ions. The effect is correlated with activation of the inflammatory pathways P38 MAP- kinase, Jun-N-terminal kinase, and NF-kappaB. The effect is reduced by adding to the medium GSH or clotrimazole (CTM), an inhibitor of Ca(2+)-influx through TRPM2 channels. It is also produced by inhibiting TRPM2 protein expression in microglia and astrocytes through introduction of its small inhibitory RNA (siRNA). TRPM2 mRNA is expressed by glial cells but not by SH-SY5Y cells. BSO in the culture medium causes an almost 3-fold increase in [Ca(2+)](i) in microglia and astrocytes over a 24-h period, which is reduced to half by the addition of CTM. The data strongly suggest that inhibiting intracellular GSH synthesis induces a neuroinflammatory response in human microglia and astrocytes, which is linked to Ca(2+) influx through TRPM2 channels. It represents a new model for inducing neuroinflammation and suggests that increasing GSH levels in glial cells may confer neuroprotection in neurodegenerative diseases, such as Alzheimer disease, which have a prominent neuroinflammatory component.

Cribrostatin 6 induces death in cancer cells through a reactive oxygen species (ROS)-mediated mechanism

Cribrostatin 6 is a quinone-containing natural product that induces the death of cancer cell lines in culture, and its mechanism of action and scope of activity are unknown. Here we show that cribrostatin 6 has broad anticancer activity, potently inducing apoptotic cell death that is not preceded by any defined cell cycle arrest. Consistent with this data, we find that cribrostatin 6 treated cells have large amounts of reactive oxygen species (ROS) and, based on transcript profiling experiments and other data, this ROS generation is likely the primary mechanism by which cribrostatin 6 induces apoptosis. Given the success of certain ROS producers as anticancer agents, cribrostatin 6 has potential as a novel chemotherapeutic agent.

Antitumor activity of a novel antisense oligonucleotide against Akt1

The AKT pathway is an important therapeutic target for cancer drug discovery as it functions as a main point for transducing extracellular and intracellular oncogenic signals. Moreover, alternations of the AKT pathway have been found in a wide range of cancers. In the present study, we found that an Akt1 antisense oligonucleotide (Akt1 AO) significantly downregulated the expression of AKT1 at both the mRNA and protein levels and inhibited cellular growth at nanomolar concentrations in various types of human cancer cells. Combined treatment of Akt1 AO with several cytotoxic drugs resulted in an additive growth inhibition of Caki-1 cells. The in vivo effectiveness of Akt1 AO was determined using two different xenograft nude mouse models. Akt1 AO (30 mg/kg, i.v. every 48 h) significantly inhibited the tumor growth of nude mouse subcutaneously implanted with U251 human glioblastoma cells after 27 days treatment. Akt1 AO (30 mg/kg, i.p continuously via osmotic pump) also significantly inhibited the tumor formation in nude mice implanted with luciferase-expressing MIA human pancreatic cancer cells (MIA-Luc) after 14 days of treatment. The luciferase signals from MIA-Luc cells were reduced or completely abolished after 2 weeks of treatment and the implanted tumors were barely detectable. Our findings suggest that Akt1 AO alone or in combination with other clinically approved anticancer agents should be further explored and progressed into clinical studies as a potential novel therapeutic agent.

ATP sensitizes H460 lung carcinoma cells to cisplatin-induced apoptosis

Platinum resistance of cancer cells may evolve due to a decrease in intracellular drug accumulation, decreased cell permeability or by an increased deactivation of the drug by glutathione (GSH). The aim of this study was (1) to investigate the effect of adenosine 5'-triphosphate (ATP) on the cytotoxicity of cisplatin in a large cell lung carcinoma cell line (H460), and (2) to examine the potential involvement of increased cisplatin uptake, GSH depletion and pyrimidine starvation by ATP in this effect. H460 cells were harvested and seeded (5% CO(2); 37 degrees C). Subsequently, cells were incubated with medium or ATP followed by an incubation with cisplatin. Cytotoxicity screening was analyzed by the sulforhodamine B (SRB) colorimetric assay, lactate dehydrogenase and caspase-3/7 activity. Pre-incubation for 72h with 0.3 and 3mM ATP strongly enhanced the anti-proliferative potency of cisplatin 2.9- and 7.6-fold, respectively. Moreover, after incubation of H460 cells with 0.3mM ATP the intracellular platinum concentration increased, indicating increased cisplatin uptake by ATP. ATP, despite lowering the LD(50) of cisplatin, did not modulate GSH levels in H460 cells. ATP itself showed a biphasic effect on H460 cell growth: 0.3mM inhibited H460 cell growth via the pyrimidine starvation effect, activation of caspase-3/7 and LDH leakage, while 3mM ATP showed no effect on cell growth. In conclusion, ATP sensitizes the H460 cells to cisplatin-induced apoptosis. The effect of 0.3mM ATP is not due to GSH depletion but involves increased cisplatin uptake and pyrimidine starvation due to ATP conversion to adenosine followed by cellular uptake.

6-(Het)aryl-7-deazapurine ribonucleosides as novel potent cytostatic agents

A series of novel 7-deazapurine ribonucleosides bearing an alkyl, aryl, or hetaryl group in position 6 and H, F, or Cl atom in position 7 has been prepared either by Pd-catalyzed cross-coupling reactions of the corresponding protected 6-chloro-(7-halogenated-)7-deazapurine ribonucleosides with alkyl- or (het)arylorganometallics followed by deprotection, or by single-step aqueous phase cross-coupling reactions of unprotected 6-chloro-(7-halogenated-)7-deazapurine ribonucleosides with (het)arylboronic acids. Significant cytostatic effect was detected with a substantial proportion of the prepared compounds. The most potent were 7-H or 7-F derivatives of 6-furyl- or 6-thienyl-7-deazapurines displaying cytostatic activity in multiple cancer cell lines with a geometric mean of 50% growth inhibition concentration ranging from 16 to 96 nM, a potency comparable to or better than that of the nucleoside analogue clofarabine. Intracellular phosphorylation to mono- and triphosphates and the inhibition of total RNA synthesis was demonstrated in preliminary study of metabolism and mechanism of action studies.

MicroRNAs reduce tumor growth and contribute to enhance cytotoxicity induced by gefitinib in non-small cell lung cancer

MicroRNAs (miRNAs) have emerged as key post-transcriptional regulators of gene expression, involved in diverse physiological and pathological processes. An oncogenic or tumor-suppressive miRNA may have potential as a therapeutic target to control cancers. Gefitinib is a tyrosine kinase inhibitor that targets epidermal growth factor receptor (EGFR). H460 and A549 cells with EGFR receptor-independent over-activation of protein kinase B (Akt) or extracellular signal-regulated kinases (ERK) are significantly resistant to gefitinib. The first aim of this study was to confirm a role for three miRNAs (let-7a, hsa-miR-126, and hsa-miR-145) in the inhibition of proliferation in non-small cell lung cancer (NSCLC) cells. A second aim was to evaluate three miRNAs for their abilities to overcome cellular resistance and enhance the gefitinib cytotoxicity. The expression of miRNAs was estimated by real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR). Cell proliferation was examined by sulforhodamine B assay and tumor xenografts were measured in SCID/beige mice. The activation of Akt and ERK was observed by Western blotting. Forced expression of individual miRNA suppressed the growth of two cell lines and xenografts. The effect varied among different miRNAs and cells. Restoration of hsa-miR-126 more obviously inhibited cell growth than did restoration of hsa-miR-145 in both cells, and the suppressive effect was more significant in H460 xenografts than in A549 xenografts. Western blotting revealed that the inhibition of cell proliferation resulted from the inhibition of the activation of Akt and ERK. Moreover, forced expression of miRNAs contributed to enhanced cytotoxicity induced by gefitinib in lung cancer cells; especially in hsa-miR-126, the highest value of half max inhibitory (IC50) was increased sixfold. These findings confirm that tumor-suppressive miRNAs can inhibit the growth of NSCLC cells and enhance the targeted agents cytotoxicity, suggesting novel potential approaches to an improvement in chemotherapy.

Shiga toxin A subunit mutant of Escherichia coli O157:H7 releases outer membrane vesicles containing the B-pentameric complex

Shiga toxins (STx) are secreted extracellularly through the outer membrane vesicles (OMVs) of Escherichia coli O157:H7. In an attempt to produce STxA-deficient OMVs from E. coli O157:H7, site-specific deletions of the stx1A and stx2A subunit genes were carried out. The STxA-deficient phenotype of the stx1A/stx2A mutant was confirmed by Vero cell cytotoxicity and VTEC-RPLA assay. Western blot analyses showed that the B (STxB) subunits were present without coupling to STxA in the OMVs of the STxA-deficient mutant. Furthermore, STxB was located in its homo-pentameric complexes, as revealed by immunoprecipitation and immunoblotting with anti-STxB antibodies. These results suggest that STxB alone can be oligomerized into the B pentamer in the periplasm, and subsequently entrapped into the OMVs. Determination of the median lethal dose concentration for the OMV preparations suggests that the STxA-deficient OMVs containing STxB complex could be safely used as vaccine delivery vehicles.

Feasibility Evaluation of 3 Automated Cellular Drug Screening Assays on a Robotic Workstation

This study presents the implementation and optimization of 3 cell-based assays on a TECAN Genesis workstation—the Caspase-Glo® 3/7 and sulforhodamine B (SRB) screening assays and the mechanistic Caco-2 permeability protocol—and evaluates their feasibility for automation. During implementation, the dispensing speed to add drug solutions and fixative trichloroacetic acid and the aspiration speed to remove the supernatant immediately after fixation were optimized. Decontamination steps for cleaning the tips and pipetting tubing were also added. The automated Caspase-Glo® 3/7 screen was successfully optimized with Caco-2 cells (Z′ 0.7, signal-to-base ratio [S/B] 1.7) but not with DU-145 cells. In contrast, the automated SRB screen was successfully optimized with the DU-145 cells (Z′ 0.8, S/B 2.4) but not with the Caco-2 cells (Z′ —0.8, S/B 1.4). The automated bidirectional Caco-2 permeability experiments separated successfully low- and high-permeability compounds (Z′ 0.8, S/B 84.2) and passive drug permeation from efflux-mediated transport (Z′ 0.5, S/B 8.6). Of the assays, the homogeneous Caspase-Glo® 3/7 assay benefits the most from automation, but also the heterogeneous SRB assay and Caco-2 permeability experiments gain advantages from automation.

A 4-aminoquinoline derivative that markedly sensitizes tumor cell killing by Akt inhibitors with a minimum cytotoxicity to non-cancer cells

The purpose of this study was to evaluate the enhancement value of chloroquine analogs when used in combination with Akt inhibitors on the MDA-MB468, MDA-MB231 and MCF7 human breast cancer cell lines. The result showed that the combination of certain chloroquine analogs and Akt inhibitors are highly effective. In particular, the chloroquine analog N′-(7-fluoro-quinolin-4-yl)-N,N-dimethyl-ethane-1,2-diamine (compound 5) was highly effective in sensitizing cancer cell killing when combined with either Akt inhibitor 8 (1-{1-[4-(7-phenyl-1H-imidazo[4,5-g]quinoxalin-6-yl)-benzyl]-piperidin-4-yl}-1,3-dihydro-benzoimidazol-2-one) or 9 ([4-(2-chloro-4a,10a-dihydro-phenoxazin-10-yl)-butyl]-diethyl-amine hydrochloride). Importantly, the enhancement of chloroquine analogs 5 on cell killing by Akt inhibitors 8 and 9 was cancer-specific. Thus, this combinational approach is highly promising in controlling tumors with a minimum side effect. Structural analysis of effective and ineffective chloroquine analogs suggests that the 4-aminoquinoline scaffold and lateral side chain of dimethylamino functionality play an important role for the enhancement of cell killing by Akt inhibitors.

A small molecule inhibitor of XIAP induces apoptosis and synergises with vinorelbine and cisplatin in NSCLC

Background:

Evasion of apoptosis contributes to the pathogenesis of solid tumours including non-small cell lung cancer (NSCLC). Malignant cells resist apoptosis through over-expression of inhibitor of apoptosis proteins (IAPs), such as X-linked IAP (XIAP).

Methods:

A phenylurea-based small molecule inhibitor of XIAP, XIAP antagonist compound (XAC) 1396-11, was investigated preclincally to determine its ability to sensitise to clinically relevant cytotoxics, potentially allowing dose reduction while maintaining therapeutic efficacy.

Results:

XIAP protein expression was detected in six NSCLC cell lines examined. The cytotoxicity of XAC 1396-11 against cultured NSCLC cell lines in vitro was concentration- and time-dependent in both short-term and clonogenic assays. XAC 1396-11-induced apoptosis was confirmed by PARP cleavage and characteristic nuclear morphology. XAC 1396-11 synergised with vinorelbine±cisplatin in H460 and A549 NSCLC cells. The mechanism of synergy was enhanced apoptosis, shown by increased cleavage of caspase-3 and PARP and by the reversal of synergy by a pan-caspase inhibitor. Synergy between XAC 1396-11 and vinorelbine was augmented by optimising drug scheduling with superior effects when XAC 1396-11 was administered before vinorelbine.

Conclusion:

These preclinical data suggest that XIAP inhibition in combination with vinorelbine holds potential as a therapeutic strategy in NSCLC.

Antiprotozoal, anticancer and antimicrobial activities of dihydroartemisinin acetal dimers and monomers

Nine dihydroartemisinin acetal dimers (6-14) with diversely functionalized linker units were synthesized and tested for in vitro antiprotozoal, anticancer and antimicrobial activity. Compounds 6, 7 and 11 [IC(50): 3.0-6.7 nM (D6) and 4.2-5.9 nM (W2)] were appreciably more active than artemisinin (1) [IC(50): 32.9 nM (D6) and 42.5 nM (W2)] against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of the malaria parasite, Plasmodium falciparum. Compounds 10, 13 and 14 displayed enhanced anticancer activity in a number of cell lines compared to the control drug, doxorubicin. The antifungal activity of 7 and 12 against Cryptococcus neoformans (IC(50): 0.16 and 0.55 microM, respectively) was also higher compared to the control drug, amphotericin B. The antileishmanial and antibacterial activities were marginal. A number of dihydroartemisinin acetal monomers (15-17) and a trimer (18) were isolated as byproducts from the dimer synthesis and were also tested for biological activity.

EM011 activates a survivin-dependent apoptotic program in human non-small cell lung cancer cells

Background

Lung cancer remains a leading cause of cancer death among both men and women in the United States. Treatment modalities available for this malignancy are inadequate and thus new drugs with improved pharmacological profiles and superior therapeutic indices are being continually explored. Noscapinoids constitute an emerging class of anticancer agents that bind tubulin but do not significantly alter the monomer/polymer ratio of tubulin. EM011, a rationally-designed member of this class of non-toxic agents, is more potent than the lead molecule, noscapine.

Results

Here we report that EM011 inhibited proliferation of a comprehensive panel of lung cancer cells with IC₅₀'s ranging from 4-50 μM. In A549 human non-small cell lung cancer cells, the antiproliferative activity was mediated through blockage of cell-cycle progression by induction of a transient but robust mitotic arrest accompanied by activation of the spindle assembly checkpoint. The mitotically-arrested A549 cells then override the activated mitotic checkpoint and aberrantly exit mitosis without cytokinesis resulting in pseudo G1-like multinucleated cells that either succumb directly to apoptosis or continue another round of the cell-cycle. The accumulated enormous DNA perhaps acts as genotoxic stress to trigger cell death. EM011-induced apoptotic cell death in A549 cells was associated with a decrease of the Bcl2/BAX ratio, activation of caspase-3 and cleavage of PARP. Furthermore, EM011 induced downregulation of survivin expression over time of treatment. Abrogation of survivin led to an increase of cell death whereas, overexpression caused decreased apoptosis.

Conclusion

These in vitro data suggest that EM011 mediates antiproliferative and proapoptotic activity in non-small cell A549 lung cancer cells by impeding cell-cycle progression and attenuating antiapoptotic signaling circuitries (viz. Bcl2, survivin). The study provides evidence for the potential usefulness of EM011 in chemotherapy of lung cancer.

Procaspase-3 activation as an anti-cancer strategy: structure-activity relationship of procaspase-activating compound 1 (PAC-1) and its cellular co-localization with caspase-3

A goal of personalized medicine as applied to oncology is to identify compounds that exploit a defined molecular defect in a cancerous cell. A compound called procaspase-activating compound 1 (PAC-1) was reported that enhances the activity of procaspase-3 in vitro and induces apoptotic death in cancer cells in culture and in mouse xenograft models. Experimental evidence indicates that PAC-1 activates procaspase-3 in vitro through chelation of inhibitory zinc ions. Described herein is the synthesis and biological activity of a family of PAC-1 derivatives where key functional groups have been systematically altered. Analysis of these compounds reveals a strong correlation between the in vitro procaspase-3 activating effect and their ability to induce death in cancer cells in culture. Importantly, we also show that a fluorescently labeled version of PAC-1 co-localizes with sites of caspase-3 activity in cancer cells. The data presented herein further bolster the hypothesis that PAC-1 induces apoptosis in cancer cells through the direct activation of procaspase-3, has implications for the design and discovery of next-generation procaspase-3 activating compounds, and sheds light on the anti-apoptotic role of cellular zinc.

Application of the McMurry coupling reaction in the synthesis of tri- and tetra-arylethylene analogues as potential cancer chemotherapeutic agents

Structural redesign of selected non-steroidal estrogen receptor binding compounds has previously been successful in the discovery of new inhibitors of tubulin assembly. Accordingly, tetra-substituted alkene analogues (21-30) were designed based in part on combinations of the structural and electronic components of tamoxifen and combretastatin A-4 (CA4). The McMurry coupling reaction was used as the key synthetic step in the preparation of these tri- and tetra-arylethylene analogues. The structural assignment of E, Z isomers was determined on the basis of 2D-NOESY experiments. The ability of these compounds to inhibit tubulin polymerization and cell growth in selected human cancer cell lines was evaluated. Although the compounds were found to be less potent than CA4, these analogues significantly advance the known structure-activity relationship associated with the colchicine binding site on beta-tubulin.

Iron labeling and pre-clinical MRI visualization of therapeutic human neural stem cells in a murine glioma model

BACKGROUND

Treatment strategies for the highly invasive brain tumor, glioblastoma multiforme, require that cells which have invaded into the surrounding brain be specifically targeted. The inherent tumor-tropism of neural stem cells (NSCs) to primary and invasive tumor foci can be exploited to deliver therapeutics to invasive brain tumor cells in humans. Use of the strategy of converting prodrug to drug via therapeutic transgenes delivered by immortalized therapeutic NSC lines have shown efficacy in animal models. Thus therapeutic NSCs are being proposed for use in human brain tumor clinical trials. In the context of NSC-based therapies, MRI can be used both to non-invasively follow dynamic spatio-temporal patterns of the NSC tumor targeting allowing for the optimization of treatment strategies and to assess efficacy of the therapy. Iron-labeling of cells allows their presence to be visualized and tracked by MRI. Thus we aimed to iron-label therapeutic NSCs without affecting their cellular physiology using a method likely to gain United States Federal Drug Administration (FDA) approval.

METHODOLOGY

For human use, the characteristics of therapeutic Neural Stem Cells must be clearly defined with any pertubation to the cell including iron labeling requiring reanalysis of cellular physiology. Here, we studied the effect of iron-loading of the therapeutic NSCs, with ferumoxide-protamine sulfate complex (FE-Pro) on viability, proliferation, migratory properties and transgene expression, when compared to non-labeled cells. FE-Pro labeled NSCs were imaged by MRI at tumor sites, after intracranial administration into the hemisphere contralateral to the tumor, in an orthotopic human glioma xenograft mouse model.

CONCLUSION

FE-Pro labeled NSCs retain their proliferative status, tumor tropism, and maintain stem cell character, while allowing in vivo cellular MRI tracking at 7 Tesla, to monitor their real-time migration and distribution at brain tumor sites. Of significance, this work directly supports the use of FE-Pro-labeled NSCs for real-time tracking in the clinical trial under development: "A Pilot Feasibility Study of Oral 5-Fluorocytosine and Genetically modified Neural Stem Cells Expressing Escherichia coli Cytosine Deaminase for Treatment of Recurrent High-Grade Gliomas".

GDF5 and BMP2 inhibit apoptosis via activation of BMPR2 and subsequent stabilization of XIAP

GDF5 and BMP2, members of the TGF-beta superfamily of growth factors, are known to regulate apoptosis in different cell types either positively or negatively. We wanted to investigate the effects of GDF5 and BMP2 on vascular smooth muscle cells and mouse embryonic fibroblasts and disclose the mechanism by which GDF5 and BMP2 might exert anti-apoptotic effects. The effect of GDF5 and BMP2 on proliferation and/or programmed cells death was assessed in isolated human vascular smooth muscle cells and mouse embryonic fibroblasts. We demonstrate that GDF5 and BMP2 prevent apoptosis induced by serum starvation in mouse embryonic fibroblasts but not in smooth muscle cells via the BMP receptor 2 (BMPR2), which is often mutated in hereditary cases of primary pulmonary hypertension. GDF5 and BMP2 stimulate the interaction of BMPR-2 with XIAP thereby reducing the ubiquitination of XIAP, which results in enhanced protein stability. The increased concentration of XIAP counteracts apoptosis by binding and inactivating activated caspases. We conclude that the inhibition of apoptosis in mouse embryonic fibroblasts by BMP2 and GDF5 does not depend on more complex signal transduction pathways such as smad and MAPK signaling but on direct stabilization of XIAP by BMPR2.

Sphingosine kinase 1 localized to the plasma membrane lipid raft microdomain overcomes serum deprivation induced growth inhibition

Several studies have demonstrated that sphingosine kinase 1 (SphK1) translocates to the plasma membrane (PM) upon its activation and further suggested the plasma membrane lipid raft microdomain (PMLRM) as a target for SphK1 relocalization. To date, however, direct evidence of SphK1 localization to the PMLRM has been lacking. In this report, using multiple biochemical and subcellular fractionation techniques we demonstrate that endogenous SphK1 protein and its substrate, D-erythro-sphingosine, are present within the PMLRM. Additionally, we demonstrate that the PMA stimulation of SphK1 localized to the PMLRM results in production of sphingosine-1-phosphate as well as induction of cell growth under serum deprivation conditions. We further report that Ser225Ala and Thr54Cys mutations, reported to abrogate phosphatidylserine binding, block SphK1 targeting to the PMLRM and SphK1 induced cell growth. Together these findings provide direct evidence that the PMLRM is the major site of action for SphK1 to overcome serum-deprived cell growth inhibition.

Contribution of HIF-1 and drug penetrance to oxaliplatin resistance in hypoxic colorectal cancer cells

BACKGROUND

Hypoxia is as an indicator of poor treatment outcome. Consistently, hypoxic HCT116 colorectal cancer cells are resistant to oxaliplatin, although the mechanistic basis is unclear. This study sought to investigate the relative contribution of HIF-1 (hypoxia-inducible factor-1)-mediated gene expression and drug penetrance to oxaliplatin resistance using three-dimensional spheroids.

METHODS

Hypoxia-inducible factor-1alpha function was suppressed by the stable expression of a dominant-negative form in HCT116 cells (DN). Cells were drug exposed as monolayer or multicellular spheroid cultures. Cells residing at differing oxygenation status were isolated from Hoechst 33342-treated spheroids using flow cytometry. Sub-populations were subjected to clonogenic survival assays and to Inductively-Coupled Plasma Mass Spectroscopy to determine oxaliplatin uptake.

RESULTS

In spheroids, a sensitivity gradient (hypoxic<aerobic) was revealed by survival assays and this correlated with levels of platinum-bound DNA. The resistance of hypoxic sub-populations exceeded relative changes in adduct levels, implicating factors other than drug penetrance in cell response. Dominant-negative monolayer cells showed no resistance to oxaliplatin in hypoxia and spheroids; the relative resistance of hypoxic compared with aerobic sub-populations was reduced compared with those from controls.

CONCLUSION

Overall, data show that drug penetration, DNA damage levels and HIF-1-dependent processes, all contribute to the resistance of hypoxic cells to oxaliplatin.

Protein transport in human cells mediated by covalently and noncovalently conjugated arginine-rich intracellular delivery peptides

Generally, biomacromolecules, such as DNA, RNA, and proteins, cannot freely permeate into cells from outside the membrane. Protein transduction domains (PTDs) are peptides containing a large number of basic amino acids that can deliver macromolecules into living cells. Arginine-rich intracellular delivery (AID) peptides are more effective than other PTD peptides at carrying large molecules across cellular membranes. In the present study, we demonstrated that AID peptides are able to deliver cargo proteins into living cells in both covalent and noncovalent protein transductions (CNPT) synchronously. Human A549 cells were treated with a fluorescent protein (FP) that was noncovalently premixed with another AID-conjugated FP, which emitted a different color. After the delivery of carrier AID-FP and cargo FP into cells, the emission and merge of fluorescence were observed and recorded with a confocal microscope, while the internalization efficiency was quantitatively analyzed with a flow cytometer. The optimal molecular ratio between carrier AID-FP and cargo FP for CNPT is about 1:1/3. Fluorescence resonance energy transfer (FRET) assay further confirmed AID-conjugates can physically interact with its cargo FPs in CNPT in cells. Potential uptake mechanisms of CNPT may involve a combination of multiple internalization pathways. After delivery, intracellular distributions of AID-conjugates and FPs may possibly colocalize with lysosomes. These results will facilitate the understanding of multiple mechanisms of PTDs, and provide a powerful tool for simultaneously delivering several proteins or compounds in protein internalization.

Selective cytostatic and cytotoxic anticancer effects of bisfunctional agents: A strategy for the design of DNA binding agents

Various agents have been synthesized and proved useful for the National Cancer Institute's anticancer testing as potential new drugs, but most agents suffer side effects from their limited selectivity against cancer cells over healthy ones. Therefore, this paper attempts to describe drugs in terms of the level of tumor cell selectivity which they possess to define the features of molecules that are essential for useful cytotoxicity. Selected cyclic amidinothymine analogues (NSC 697864, NSC 697865, and NSC 697869) have nanomolar inhibitory activities against leukemia cell lines: CCRF-CEM, HL-60(TB), while bisfunctional cancer fighters NSC 702408 and NSC 702409, showing larger numbers of cytostatic and cytotoxic effects, in an extended conformation would probably adopt a similar to NSC 715653 conformation leaving both opposite H-bond donor groups at the same distance to interact with DNA in a similar way. Such specific interactions (cell line selectivity to unique mutated patterns) lower considerably the observed dose-response concentrations. This in vitro selectivity is shown to translate into in vivo efficacy indicated by the inflection in the cumulative testing curve.

Fluorophore binding aptamers as a tool for RNA visualization

Fluorescence correlation spectroscopy (FCS) is suitable for the detection of fluorescent molecules in living cells. For the visualization of mRNA, we genetically fused a fluorophore-specific RNA aptamer to the coding mRNA of the green fluorescent protein, as well as to noncoding sequences. Using these constructs, we showed that the aptamer portion of the mRNA still binds the fluorophore in the nanomolar range as determined via FCS. Furthermore, the binding took place in the context of total RNA extract. A tandem construct of the RNA aptamer even exhibited a lower K(d) than the monomer. This FCS-based method establishes a tool for minimal invasive detection of RNA at the single molecule level in individual living cells.

Inhibition of gamma-secretase induces G2/M arrest and triggers apoptosis in breast cancer cells

γ-Secretase activity is vital for the transmembrane cleavage of Notch receptors and the subsequent migration of their intracellular domains to the nucleus. Notch overexpression has been associated with breast, colon, cervical and prostate cancers. We tested the effect of three different γ-secretase inhibitors (GSIs) in breast cancer cells. One inhibitor (GSI1) was lethal to breast cancer cell lines at concentrations of 2 μM and above but had a minimal effect on the non-malignant breast lines. GSI1 was also cytotoxic for a wide variety of cancer cell lines in the NCI60 cell screen. GSI1 treatment resulted in a marked decrease in γ-secretase activity and downregulation of the Notch signalling pathway with no effects on expression of the γ-secretase components or ligands. Flow cytometric and western blot analyses indicated that GSI1 induces a G2/M arrest leading to apoptosis, through downregulation of Bcl-2, Bax and Bcl-XL. GSI1 also inhibited proteasome activity. Thus, the γ-secretase inhibitor GSI1 has a complex mode of action to inhibit breast cancer cell survival and may represent a novel therapy in breast cancer.

Benzene metabolite hydroquinone up-regulates chondromodulin-I and inhibits tube formation in human bone marrow endothelial cells

Bone marrow is a major target of benzene toxicity, and NAD-(P)H:quinone oxidoreductase (NQO1), an enzyme protective against benzene toxicity, is present in human bone marrow endothelial cells, which form the hematopoietic stem cell vascular niche. In this study, we have employed a transformed human bone marrow endothelial cell (TrHBMEC) line to study the adverse effects induced by the benzene metabolite hydroquinone. Hydroquinone inhibited TrHBMEC tube formation at concentrations that were not overtly toxic, as demonstrated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide or sulforhodamine B analysis. Hydroquinone was found to up-regulate chondromodulin-I (ChM-I), a protein that promotes chondrocyte growth and inhibits endothelial cell growth and tube formation. Recombinant human ChM-I protein inhibited tube formation in TrHBMECs, suggesting that up-regulation of ChM-I may explain the ability of hydroquinone to inhibit TrHB-MEC tube formation. To explore this possibility further, anti-ChM-I small interfering RNA (siRNA) was used to deplete ChM-I mRNA and protein. Pretreatment with anti-ChM-I siRNA markedly abrogated hydroquinone-induced inhibition of tube formation in TrHBMECs. Overexpression of the protective enzyme NQO1 in TrHBMECs inhibited the up-regulation of ChM-I and abrogated the inhibition of tube formation induced by hydroquinone. In summary, hydroquinone treatment up-regulated ChM-I and inhibited tube formation in TrHBMECs; NQO1 inhibited hydroquinone-induced up-regulation of ChM-I in TrHB-MECs and protected cells from hydroquinone-induced inhibition of tube formation. This study demonstrates that ChM-I up-regulation is one of the underlying mechanisms of inhibition of tube formation and provides a mechanism that may contribute to benzene-induced toxicity at the level of bone marrow endothelium.

Preclinical efficacy of the bioreductive alkylating agent RH1 against paediatric tumours

Background:

Despite substantial improvements in childhood cancer survival, drug resistance remains problematic for several paediatric tumour types. The urgent need to access novel agents to treat drug-resistant disease should be expedited by pre-clinical evaluation of paediatric tumour models during the early stages of drug development in adult cancer patients.

Methods/results:

The novel cytotoxic RH1 (2,5-diaziridinyl-3-[hydroxymethyl]-6-methyl-1,4-benzoquinone) is activated by the obligate two-electron reductase DT-diaphorase (DTD, widely expressed in adult tumour cells) to a potent DNA interstrand cross-linker. In acute viability assays against neuroblastoma, osteosarcoma, and Ewing′s sarcoma cell lines RH1 IC₅₀ values ranged from 1-200 nM and drug potency correlated both with DTD levels and drug-induced apoptosis. However, synergy between RH1 and cisplatin or doxorubicin was only seen in low DTD expressing cell lines. In clonogenic assays RH1 IC₅₀ values ranged from 1.5–7.5 nM and drug potency did not correlate with DTD level. In A673 Ewing's sarcoma and 791T osteosarcoma tumour xenografts in mice RH1 induced apoptosis 24 h after a single bolus injection (0.4 mg/kg) and daily dosing for 5 days delayed tumour growth relative to control.

Conclusion:

The demonstration of RH1 efficacy against paediatric tumour cell lines, which was performed concurrently with the adult Phase 1 Trial, suggests that this agent may have clinical usefulness in childhood cancer.

Tiling path genomic profiling of grade 3 invasive ductal breast cancers

PURPOSE

To characterize the molecular genetic profiles of grade 3 invasive ductal carcinomas of no special type using high-resolution microarray-based comparative genomic hybridization (aCGH) and to identify recurrent amplicons harboring putative therapeutic targets associated with luminal, HER-2, and basal-like tumor phenotypes.

EXPERIMENTAL DESIGN

Ninety-five grade 3 invasive ductal carcinomas of no special type were classified into luminal, HER-2, and basal-like subgroups using a previously validated immunohistochemical panel. Tumor samples were microdissected and subjected to aCGH using a tiling path 32K BAC array platform. Selected regions of recurrent amplification were validated by means of in situ hybridization. Expression of genes pertaining to selected amplicons was investigated using quantitative real-time PCR and gene silencing was done using previously validated short hairpin RNA constructs.

RESULTS

We show that basal-like and HER-2 tumors are characterized by "sawtooth" and "firestorm" genetic patterns, respectively, whereas luminal cancers were more heterogeneous. Apart from confirming known amplifications associated with basal-like (1q21, 10p, and 12p), luminal (8p12, 11q13, and 11q14), and HER-2 (17q12) cancers, we identified previously unreported recurrent amplifications associated with each molecular subgroup: 19q12 in basal-like, 1q32.1 in luminal, and 14q12 in HER-2 cancers. PPM1D gene amplification (17q23.2) was found in 20% and 8% of HER-2 and luminal cancers, respectively. Silencing of PPM1D by short hairpin RNA resulted in selective loss of viability in tumor cell lines harboring the 17q23.2 amplification.

CONCLUSIONS

Our results show the power of aCGH analysis in unraveling the genetic profiles of specific subgroups of cancer and for the identification of novel therapeutic targets.

High-dose fenretinide in oral leukoplakia

We previously showed that low-dose fenretinide (200 mg/d) had limited activity in retinoid-resistant oral leukoplakia (34% response rate) possibly because serum drug levels were insufficient to induce retinoid receptor-independent apoptosis. Therefore, we designed the single-arm phase II trial reported here to investigate whether higher-dose fenretinide would improve leukoplakia response over that of our previous study. Leukoplakia patients received fenretinide (900 mg/m(2) twice daily) in four 3-week cycles (1 week on drug followed by 2 weeks off). At week 12, clinical responses were determined and blood samples were collected for serum drug level assessments. A planned interim futility analysis led to early trial closure after the initial 15 (of 25 planned) patients because only 3 (20%) had a partial response (stopping rule: <or=4 responses in first 16 patients). Fenretinide was well tolerated--only one grade 3 adverse event (diarrhea) occurred. Serum fenretinide levels changed from 0 (baseline) to 0.122 +/- 0.093 micromol/L (week 12). In correlative in vitro studies, high-dose fenretinide inhibited the growth of head and neck cancer cells more and oral leukoplakia cells less than did lower doses of fenretinide. This result is consistent with our clinical finding that high-dose fenretinide did not improve on the historical response rate of lower-dose fenretinide in our previous oral leukoplakia trial.