Cytotoxic effects of 27 anticancer drugs in HeLa and MDR1-overexpressing derivative cell lines

Involvement of everolimus‑induced ABCB1 downregulation in drug‑drug interactions

Everolimus is an oral mammalian target of rapamycin (mTOR) inhibitor used in cancer chemotherapy and transplantation. Due to its therapeutic properties, everolimus has been used long-term in clinical practice. Drug interactions with everolimus during gastrointestinal absorption can alter the oral bioavailability of everolimus and/or concomitant drugs. However, the effects of everolimus on gastrointestinal absorption remain unknown. The present study assessed the impact of continuous exposure to everolimus on expression and function of the ATP-binding cassette (ABC) transporter ABCB1 and ABCG2 using a Caco-2 intestinal cell model. Caco-2 subline, Caco/EV, was established by continuously exposing Caco-2 cells to 1 µM everolimus. Cell viability was evaluated using WST-1 assay. mRNA levels were measured by reverse transcription-quantitative PCR. Transport activity of ABCB1 was evaluated through the cellular accumulation of Rhodamin 123, a substrate for ABCB1. The half-maximal inhibitory concentration (IC50) values for everolimus in Caco-2 and Caco/EV cells were 0.31 and 4.33 µM, respectively, indicating 14-fold resistance in Caco/EV cells. Sensitivity to paclitaxel and 7-ethyl-10-hydroxycamptothecin, which are substrates for ABCB1 and ABCG2, respectively, was enhanced in Caco/EV, but not in Caco-2 cells. The IC50 values of cisplatin were comparable in both cell lines. Furthermore, mRNA expression levels of ABCB1 and ABCG2 were lower in Caco/EV cells than in Caco-2 cells, and the cellular accumulation of Rhodamine 123 was significantly higher in Caco/EV cells. These findings demonstrated that continuous exposure to everolimus suppressed the expression and function of ABCB1 and ABCG2, suggesting potential drug-drug interactions via the suppression of ABCB1 and ABCG2 in the intestinal tract.

Oral cytarabine ocfosfate pharmacokinetics and assessment of leukocyte biomarkers in normal dogs

BACKGROUND

Cytosine arabinoside (Ara-C) is a nucleoside analog prodrug utilized for immunomodulatory effects mediated by its active metabolite Ara-CTP. Optimal dosing protocols for immunomodulation in dogs have not been defined. Cytarabine ocfosfate (CO) is a lipophilic prodrug of Ara-C that can be administered PO and provides prolonged serum concentrations of Ara-C.

OBJECTIVES

Provide pharmacokinetic data for orally administered CO and determine accumulation and functional consequences of Ara-CTP within peripheral blood leukocytes.

ANIMALS

Three healthy female hound dogs and 1 healthy male Beagle.

METHODS

Prospective study. Dogs received 200 mg/m2 of CO PO q24h for 7 doses. Serum and cerebrospinal fluid (CSF) CO and Ara-C concentrations were measured by liquid chromatography-tandem mass spectroscopy (LC-MS/MS). Complete blood counts, flow cytometry, and leukocyte activation assays were done up to 21 days. Incorporation of Ara-CTP within leukocyte DNA was determined by LC-MS/MS.

RESULTS

Maximum serum concentration (Cmax ) for Ara-C was 456.1-724.0 ng/mL (1.88-2.98 μM) and terminal half-life was 23.3 to 29.4 hours. Cerebrospinal fluid: serum Ara-C ratios ranged from 0.54 to 1.2. Peripheral blood lymphocyte concentrations remained within the reference range, but proliferation rates poststimulation were decreased at 6 days. Incorporation of Ara-CTP was not saturated and remained >25% of peak concentration at 13 days.

CONCLUSIONS AND CLINICAL IMPORTANCE

Oral CO may produce prolonged serum Ara-C half-lives at concentrations sufficient to induce functional changes in peripheral leukocytes and is associated with prolonged retention of DNA-incorporated Ara-CTP. Application of functional and active metabolite assessment is feasible and may provide more relevant data to determine optimal dosing regimens for Ara-C-based treatments.

Vitamin D increases the efficacy of cisplatin on bladder cancer cell lines

BACKGROUND

1,25(OH)2D3(Calcitriol), which is a broad regulatory molecule, plays a role in changing the efficacy of chemotherapeutic drugs. Cisplatin is one of a current standard chemotherapy regimen for bladder cancer. Increasing the effectiveness of the treatment and reducing the side effects to chemotherapeutics are of great importance in bladder cancer. We aimed to investigate the effect of the combination of cisplatin and calcitriol in order to create a possible advantage in treatment of bladder cancer.

METHODS

T24, ECV-304 and HUVEC cell lines were treated with calcitriol and cisplatin individually and in combination. Dose determination and combination treatments of calcitriol and cisplatin were evaluated using the MTT assay for cytotoxicity analysis on the cells. Annexin V-PI staining method was used for apoptosis determination by flow cytometry. Also the P-gp expression levels were determined by flow cytometry.

RESULTS

The combination treatment increased the anti-proliferative efficacy compared to the efficacy in cisplatin alone in T24 cells and reduced the cytotoxicity in the HUVEC healthy cells compared to cisplatin alone. Combination treatment achieved significantly higher apoptosis rate in T24 cells compared with the rates in treatment of cisplatin alone. However apoptosis decreased in HUVEC cell line. P-gp ratios were increased in HUVEC and decreased in T24 cells with combination treatment compared to the numbers in the control cells. The rate of apoptosis and P-gp levels showed no significant change in ECV-304 cells.

CONCLUSION

Our study revealed that the combination of calcitriol and cisplatin allows the use of cisplatin at lower doses in T24 bladder cancer cell line.

Cellular irinotecan resistance in colorectal cancer and overcoming irinotecan refractoriness through various combination trials including DNA methyltransferase inhibitors: a review

Treatment with pharmacological drugs for colorectal cancer (CRC) remains unsatisfactory. A major cause of failure in pharmacotherapy is the resistance of colon cancer cells to the drugs, creating an urgent issue. In this review, we summarize previous studies on the resistance of CRC cells to irinotecan and discuss possible reasons for refractoriness. Our review presents the following five major causes of irinotecan resistance in human CRC: (1) cellular irinotecan resistance is induced mainly through the increased expression of the drug efflux transporter, ABCG2; (2) cellular irinotecan resistance is also induced in association with a nuclear receptor, pregnane/steroid X receptor (PXR/SXR), which is enriched in the CYP3A4 gene enhancer region in CRC cells by exposing the cells to SN-38; (3) irinotecan-resistant cells possess either reduced DNA topoisomerase I (Top1) expression at both the mRNA and protein levels or Top1 missense mutations; (4) alterations in the tumor microenvironment lead to drug resistance through intercellular vesicle-mediated transmission of miRNAs; and (5) CRC stem cells are the most difficult targets to successfully treat CRC. In the clinical setting, CRC gradually develops resistance to initially effective irinotecan-based therapy. To solve this problem, several clinical trials, such as irinotecan plus cetuximab vs. cetuximab monotherapy, have been conducted. Another clinical trial on irinotecan plus guadecitabine, a DNA-methyltransferase inhibitor, has also been conducted.

Anticancer Effects of Propionic Acid Inducing Cell Death in Cervical Cancer Cells

Recent studies found that short-chain fatty acids (SCFAs), which are produced through bacterial fermentation in the gastrointestinal tract, have oncoprotective effects against cervical cancer. The most common SCFAs that are well known include acetic acid, butyric acid, and propionic acid, among which propionic acid (PA) has been reported to induce apoptosis in HeLa cells. However, the mechanism in which SCFAs suppress HeLa cell viability remain poorly understood. Our study aims to provide a more detailed look into the mechanism of PA in HeLa cells. Flow cytometry analysis revealed that PA induces reactive oxygen species (ROS), leading to the dysfunction of the mitochondrial membrane. Moreover, PA inhibits NF-κB and AKT/mTOR signaling pathways and induces LC3B protein levels, resulting in autophagy. PA also increased the sub-G1 cell population that is characteristic of cell death. Therefore, the results of this study propose that PA inhibits HeLa cell viability through a mechanism mediated by the induction of autophagy. The study also suggests a new approach for cervical cancer therapeutics.

Transport Characteristics of 6-Mercaptopurine in Brain Microvascular Endothelial Cells Derived From Human Induced Pluripotent Stem Cells

The likelihood of reoccurrence of acute lymphoblastic leukemia is influenced by the cerebral concentration of the therapeutic agent 6-mercaptopurine (6-MP) during treatment. Therefore, it is important to understand the blood-brain barrier (BBB) transport mechanism of 6-MP. The purpose of this study was to characterize this mechanism using human induced pluripotent stem cell-derived microvascular endothelial cells (hiPS-BMECs). The permeability coefficient of 6-MP across hiPS-BMECs monolayer in the basal-to-apical direction (B-to-A) was significantly greater than that in the opposite direction (A-to-B). The inhibition profiles of 6-MP transport in the A-to-B direction were different from those in the B-to-A direction. Transport in the A-to-B direction was mainly inhibited by adenine (an inhibitor of equilibrative nucleobase transporter 1; ENBT1), while transport in the B-to-A direction was significantly reduced by inhibitors of multidrug resistance-associated proteins (MRPs), especially zaprinast (an MRP5 inhibitor). Immunocytochemical analyses demonstrated the expression of ENBT1 and MRP5 proteins in hiPS-BMECs. We confirmed that the cellular uptake of 6-MP is decreased by ENBT1 inhibitors in hiPS-BMECs and by knockdown of ENBT1 in hCMEC/D3 cells. These results suggest that ENBT1 and MRP5 make substantial contributions to the transport of 6-MP in hiPS-BMECs and hCMEC/D3 cells.

Role for Drug Transporters in Chemotherapy-Induced Peripheral Neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is a common and dose-limiting toxicity to widely used chemotherapeutics. Although the exact molecular mechanism of chemotherapy-induced peripheral neuropathy remains elusive, there is consensus that it is caused by damage to the peripheral nervous system leading to sensory symptoms. Recently developed methodologies have provided evidence of expression of drug transporters in the peripheral nervous system. In this literature review, we explore the role for drug transporters in CIPN. First, we assessed the transport of chemotherapeutics that cause CIPN (taxanes, platins, vincristine, bortezomib, epothilones, and thalidomide). Second, we cross-referenced the transporters implicated in genetic or functional studies with CIPN with their expression in the peripheral nervous system. Several drug transporters are involved in the transport of chemotherapeutics that cause peripheral neuropathy and particularly efflux transporters, such as ABCB1 and ABCC1, are expressed in the peripheral nervous system. Previous literature has linked genetic variants in efflux transporters to higher risk of peripheral neuropathy with the taxanes paclitaxel and docetaxel and the vinca alkaloid vincristine. We propose that this might be due to accumulation of the chemotherapeutics in the peripheral nervous system due to reduced neuronal efflux capacity. Thus, concomitant administration of efflux transporter inhibitors may lead to higher risk of adverse events of drugs that cause CIPN. This might prove valuable in drug development where screening new drugs for neurotoxicity might also require drug transporter consideration. There are ongoing efforts targeting drug transporters in the peripheral nervous system to reduce intraneuronal concentrations of chemotherapeutics that cause CIPN, which might ultimately protect against this dose-limiting adverse event.

Probing CO Generation through Metal-Assisted Alcohol Dehydrogenation in Metal-2-(arylazo)phenol Complexes Using Isotopic Labeling (Metal = Ru, Ir): Synthesis, Characterization, and Cytotoxicity Studies

The reaction of 2-{2-(benzo[1,3]dioxol-5-yl)- diazo}-4-methylphenol (HL) with [Ru(PPh₃)₃Cl₂] in ethanol resulted in the carbonylated ruthenium complex [RuL(PPh₃)₂(CO)] (1), wherein metal-assisted decarbonylation via in situ ethanol dehydrogenation is observed. When the reaction was performed in acetonitrile, however, the complex [RuL(PPh₃)₂(CH₃CN)] (2) was obtained as the main product, probably by trapping of a common intermediate through coordination of CH₃CN to the Ru(II) center. The analogous reaction of HL with [Ir(PPh₃)₃Cl] in ethanol did not result in ethanol decarbonylation and instead gave the organoiridium hydride complex [IrL(PPh₃)₂(H)] (3). Unambiguous evidence for the generation of CO via ruthenium-assisted ethanol oxidation is provided by the synthesis of the ¹³C-labeled complex, [Ru(PPh₃)₂L(¹³CO)] (1A) using isotopically labeled ethanol, CH₃¹³CH₂OH. To summarize all the evidence, a ruthenium-assisted mechanistic pathway for the decarbonylation and generation of alkane via alcohol dehydrogenation is proposed. In addition, the in vitro antiproliferative activity of complexes 1-3 was tested against human cervical (HeLa) and human colorectal adenocarcinoma (HT-29) cell lines. Complexes 1-3 showed impressive cytotoxicity against both HeLa (half-maximal inhibitory concentration (IC₅₀) value of 3.84-4.22 μM) and HT-29 cancer cells (IC₅₀ values between 3.3 and 4.5 μM). Moreover, the complexes were comparatively less toxic to noncancerous NIH-3T3 cells.

Tuning the pharmacokinetics and efficacy of irinotecan (IRI) loaded gelatin nanoparticles through folate conjugation

Gelatin based nanocarriers have major limitation of shorter circulation half-life (t_1/2). Present study addressed this issue by conjugating gelatin with folate followed by nanoprecipitation in presence of polysorbate 80 to form folate attached gelatin nanoparticles (GNP-F). The folic acid was conjugated with gelatin through the formation of amide linkage with a maximum conjugation yield of ~69%. Cryo-SEM analysis indicated that unconjugated gelatin nanoparticles (GNP) and GNP-F were spherical of nearly identical size of ~200 nm. The irinotecan (IRI)-loading efficiency estimated for IRI-GNP and IRI-GNP-F was 6.6 ± 0.42% and 11.2 ± 0.73% respectively and both formulations showed faster release of IRI at acidic pH (~5) than at physiological pH (~7). Further IRI-GNP-F demonstrated significantly higher cytotoxicity in folate receptor (FR)-positive HeLa cells than the unconjugated IRI-GNP nanoparticles confirming active targeting. Subsequently the antitumor activity of above formulations in FR-positive fibrosarcoma (syngeneic) tumor-bearing mice followed the order of IRI-GNP-F > IRI-GNP > free IRI. The pharmacokinetic evaluation of IRI-GNP and IRI-GNP-F revealed that encapsulation of IRI within GNP without folate improved its plasma maximum concentration (C_max). However, folate conjugation of GNP remarkably improved the t_1/2 of IRI. Taken together, folate as a targeting ligand modulates the pharmacokinetic property of IRI loaded GNP to favor active verses passive targeting.

Synthesis, structure and characterization of new dithiocarbazate-based mixed ligand oxidovanadium(iv) complexes: DNA/HSA interaction, cytotoxic activity and DFT studies

The synthesis, structure and characterization of mixed ligand oxidovanadium(iv) complexes [V^IVOL^1–2(L^N–N)] (1–3) are reported. With a view to evaluating their biological activity, their DNA/HSA interaction and cytotoxicity activity have been explored.

In vitrocytotoxicity and catalytic evaluation of dioxidovanadium(v) complexes in an azohydrazone ligand environment

Synthesis, characterization,in vitrocytotoxicity and catalytic potential of the dioxidovanadium(v) complexes of azohydrazones.

Histone deacetylase inhibitors sensitize 5-fluorouracil-resistant MDA-MB-468 breast cancer cells to 5-fluorouracil

Resistance to 5-fluorouracil (5-FU) is a serious problem in cancer therapy and overcoming it is required in order to improve the efficacy of cancer chemotherapy. Histone deacetylase (HDAC) inhibitors are used in cancer treatments and, recently, it has been reported that HDAC inhibitors can overcome resistance to various anti-cancer drugs in vitro. In the present study, a 5-FU-resistant breast cancer cell line was established, and the effects of HDAC inhibitors in these cells were examined. The 5-FU-resistant cell line MDA-MB-468 (MDA468/FU) was established by continuous exposure of the parental cells to 5-FU. This subline was characterized by high resistance to 5-FU, higher mRNA expression levels of thymidylate synthetase and dihydropyrimidine dehydrogenase (DPD), and lower mRNA expression levels of uridine monophosphate synthetase (UMPS) than the parental cells. Gimeracil, a DPD inhibitor, did not affect the sensitivity of MDA468/FU cells to 5-FU. Oteracil, a UMPS inhibitor, decreased the cytotoxicity of 5-FU in MDA468 cells, but not in MDA468/FU cells. The HDAC inhibitors, valproic acid and suberanilohydroxamic acid sensitized the two cell lines to 5-FU in a concentration-dependent manner. In conclusion, the results of the present study revealed that HDAC inhibitors increase the sensitivity to 5-FU in 5-FU-sensitive and -resistant cells.

Augmentation of the cytotoxic effects of nitrogen-containing bisphosphonates in hypoxia

OBJECTIVES

Tumour hypoxia is a major obstacle in cancer therapy that leads to poor prognosis. Therefore, the development of cancer treatments that are effective in hypoxia is necessary. Nitrogen-containing bisphosphonates (N-BPs), which are used to treat bone disease, are cytotoxic to several cancer cells in normoxia. Therefore, we investigated the cytotoxicity of N-BPs in cancer cells in hypoxia.

METHODS

We studied the cytotoxicities of N-BPs, statins and anticancer drugs in human cancer cells under hypoxic conditions (1% O₂ ). The expression levels of enzymes in the mevalonate pathway in hypoxia were measured by real-time reverse transcription polymerase chain reaction and Western blotting.

KEY FINDINGS

In hypoxia, cell growth inhibition by 5-fluorouracil and cisplatin was not changed as compared to that in normoxia; however, cell growth inhibition by N-BPs and via zoledronate-induced apoptosis was higher in hypoxia than that in normoxia. Furthermore, geranylgeraniol completely inhibited the growth inhibitory effects of zoledronate. Additionally, the mRNA and protein levels of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase significantly decreased in hypoxia. Moreover, simvastatin potentiated the growth inhibitory effect of zoledronate.

CONCLUSIONS

The cytotoxicity of N-BPs, but not 5-fluorouracil and cisplatin, is potentiated in hypoxia, through the loss of HMG-CoA reductase function. N-BPs may be effective against cancer in normoxia and hypoxia.

Genetic determinants for chemo- and radiotherapy resistance in bladder cancer

Bladder cancer (BCa) is burdened by high rates of chemo- and radio-resistance. We reviewed and summarized the current evidence regarding the genetic determinants of resistance in patients treated with chemotherapy and/or radiotherapy (RT) for BCa. Genetic heterogeneity may preexist to treatment arising with tumorigenesis or increasing progressively during the treatment. Several biological pathways seem to be involved in the cellular response to treatment. These pathways comprehend mechanisms leading to modify the intracellular concentration of the drug, mechanisms leading to increase the repair of DNA damage caused by the treatment, mechanisms leading to increase cell survival, despite DNA damage, acting on the signaling pathways affecting apoptosis, mechanisms promoting autophagy. In the present review, we focused on the genetic determinants of resistance affecting the aforementioned mechanisms.

Effective Drug Delivery in Diffuse Intrinsic Pontine Glioma: A Theoretical Model to Identify Potential Candidates

Despite decades of clinical trials for diffuse intrinsic pontine glioma (DIPG), patient survival does not exceed 10% at two years post-diagnosis. Lack of benefit from systemic chemotherapy may be attributed to an intact bloodbrain barrier (BBB). We aim to develop a theoretical model including relevant physicochemical properties in order to review whether applied chemotherapeutics are suitable for passive diffusion through an intact BBB or whether local administration via convection-enhanced delivery (CED) may increase their therapeutic potential. Physicochemical properties (lipophilicity, molecular weight, and charge in physiological environment) of anticancer drugs historically and currently administered to DIPG patients, that affect passive diffusion over the BBB, were included in the model. Subsequently, the likelihood of BBB passage of these drugs was ascertained, as well as their potential for intratumoral administration via CED. As only non-molecularly charged, lipophilic, and relatively small sized drugs are likely to passively diffuse through the BBB, out of 51 drugs modeled, only 8 (15%)-carmustine, lomustine, erlotinib, vismodegib, lenalomide, thalidomide, vorinostat, and mebendazole-are theoretically qualified for systemic administration in DIPG. Local administration via CED might create more therapeutic options, excluding only positively charged drugs and drugs that are either prodrugs and/or only available as oral formulation. A wide variety of drugs have been administered systemically to DIPG patients. Our model shows that only few are likely to penetrate the BBB via passive diffusion, which may partly explain the lack of efficacy. Drug distribution via CED is less dependent on physicochemical properties and may increase the therapeutic options for DIPG.

Rational design of drug-like compounds targeting Mycobacterium marinum MelF protein

The mycobacterial mel2 locus (mycobacterial enhanced infection locus, Rv1936-1941) is Mycobacterium marinum and M. tuberculosis specific, which can withstand reactive oxygen species (ROS) and reactive nitrogen species (RNS) induced stress. A library of over a million compounds was screened using in silico virtual ligand screening (VLS) to identify inhibitors against the modeled structure of MelF protein expressed by melF of mel2 locus so that M. marinum’s ability to withstand ROS/RNS stress could be reduced. The top ranked 1000 compounds were further screened to identify 178 compounds to maximize the scaffold diversity by manually evaluating the interaction of each compound with the target site. M. marinum melF was cloned, expressed and purified as maltose binding protein (MBP)-tagged recombinant protein in Escherichia coli. After establishing the flavin dependent oxidoreductase activity of MelF (~ 84 kDa), the inhibitors were screened for the inhibition of enzyme activity of whole cell lysate (WCL) and the purified MelF. Amongst these, 16 compounds could significantly inhibit the enzyme activity of purified MelF. For the six best inhibitory compounds, the minimal inhibitory concentration (MIC) was determined to be 3.4–19.4 μM and 13.5–38.8 μM for M. marinum and M. tuberculosis, respectively. Similarly, the minimal bactericidal concentration (MBC) was determined to be 6.8–38.8 μM and 27–38.8 μM against M. marinum and M. tuberculosis, respectively. One compound each in combination with isoniazid (INH) also showed synergistic inhibitory effect against M. marinum and M. tuberculosis with no cytotoxicity in HeLa cells. Interestingly, these inhibitors did not display any non-specific protein-structure destabilizing effect. Such inhibitors targeting the anti-ROS/RNS machinery may facilitate the efficient killing of replicating and nonreplicating mycobacteria inside the host cells.

Synthesis and electronic properties of ester substituted 1,4-dicyanodibenzodioxins and evaluation of anti-proliferative activity of all isomeric 1,2-, 2,3- and 1,4-dicyanodibenzodioxins against HeLa cell line

1,4-Dicyanodibenzodioxins bearing carboxy methyl ester groups were synthesized using our established one-step SNAr coupling reaction between ortho- and meta-ester substituted catechols and perfluorinated terephthalonitrile. These are the first examples of 1,4-dicyanodibenzodioxins substituted at both the benzene moieties. Optical spectra were similar to the earlier examples reported, with a marginal blue shift for the ester dibenzodioxins. Theoretical analysis of the molecular orbitals reveals modest destabilization of the frontier molecular orbitals of one carboxy methyl ester isomer over the other and overall higher HOMO-LUMO gap for both isomers when compared to the earlier published 1,4-dicyanodibenzodioxins. In vitro cytotoxicity against human cervical cancer HeLa cell line was evaluated for these two compounds and all other previously published dibenzodioxins from our laboratory (1,4-dicyano, 1,2-dicyano and 2,3-dicyano variants). A number of derivatives showed anti-tumor activity in μM ranges and also exhibited no cytotoxicity against normal HEK 293 cell line. Mechanistic investigation of cell death pathways indicated high levels of reactive oxygen species (ROS) in the dibenzodioxin treated tumor cell lines along with cellular nuclear fragmentation, both of which are markers of the apoptotic cell death pathway.

Synthesis, structure and cytotoxicity of a series of Dioxidomolybdenum(VI) complexes featuring Salan ligands

Seven hexacoordinated cis-dioxidomolybdenum(VI) complexes [MoO₂L^1-7] (1-7) derived from various tetradentate diamino bis(phenolato) "salan" ligands, N,N'-dimethyl-N,N'-bis-(2-hydroxy-3-X-5-Y-6-Z-benzyl)-1,2-diaminoethane {(X=Br, Y=Me, Z=H (H₂L¹); X=Me, YCl, Z=H (H₂L²); X=ⁱPr, Y=Cl, Z=Me (H₂L³)} and N,N'-bis-(2-hydroxy-3-X-5-Y-6-Z-benzyl)-1,2-diaminopropane {(X=Y=^tBu, Z=H (H₂L⁴); X=Y=Me, Z=H (H₂L⁵); X=ⁱPr, YCl, Z=Me (H₂L⁶); X=Y=Br, Z=H (H₂L⁷)} containing O-N donor atoms, have been isolated and structurally characterized. The formation of cis-dioxidomolybdenum(VI) complexes was confirmed by elemental analysis, IR, UV-vis and NMR spectroscopy, ESI-MS and cyclic voltammetry. X-ray crystallography showed the O₂N₂ donor set to define an octahedral geometry in each case. The complexes (1-7) were tested for their in vitro antiproliferative activity against HT-29 and HeLa cancer cell line. IC₅₀ values of the complexes in HT-29 follow the order 6<7<<1<2<5<<3<4 while the order was 6<7<5<1<<3<4<2 in HeLa cells. Some of the complexes proved to be as active as the clinical referred drugs, and the greater potency of 6 and 7 (IC₅₀ values of 6 are 2.62 and 10.74μM and that of 7 is 11.79 and 30.48μM in HT-29 and HeLa cells, respectively) may be dependent on the substituents in the salan ligand environment coordinated to the metal.

Effects of bisphosphonates on human esophageal squamous cell carcinoma cell survival

Esophageal squamous cell carcinoma (ESCC) is one of the most malignant cancers in Japan. Anticancer chemotherapy has been useful for ESCC treatment. However, therapeutic options are limited. Recently, bisphosphonates (BPs), which are osteoporosis drugs, have shown anticancer effects in several cancer cell lines, but the effects against ESCC cell lines are unknown. In this study, we examined the cytotoxic effects of BPs and their mechanisms of cytotoxicity in human ESCC cell lines. A first-generation BP (etidronate), two second-generation BPs (alendronate and pamidronate), and two third-generation BPs (risedronate and zoledronate) were used in this study. All BPs, except etidronate, were cytotoxic, as indicated by increased caspase-3/7 activity and numbers of Annexin-fluorescein isothiocyanate positive cells in ESCC cell lines. From cell cycle analysis, G0/G1-phase arrest was observed upon treatment with second- and third-generation BPs. In addition, Cyclin D1 protein expression levels were decreased by second- and third-generation BP treatment. Although squalene and trans, trans-farnesol minimally affected BP cytotoxicity, treatment with geranylgeraniol inhibited BP cytotoxicity almost completely. We concluded that second- and third-generation BPs are cytotoxic to ESCC cell lines as they induce apoptosis and inhibit the cell cycle through mevalonate pathway inhibition. Therefore, BP treatment may be a beneficial therapy in ESCC patients.

A quantitative microfluidic angiogenesis screen for studying anti-angiogenic therapeutic drugs

Anti-angiogenic therapy, which suppresses tumor growth by disrupting oxygen and nutrient supply from blood to the tumor, is now widely accepted as a treatment for cancer. To investigate the mechanisms of action of these anti-angiogenesis drugs, new three dimensional (3D) cell culture-based drug screening models are increasingly employed. However, there is no in vitro high-throughput screening (HTS) angiogenesis assay that can provide uniform culture conditions for the quantitative assessment of physiological responses to chemoattractant reagents under various concentrations of anti-angiogenesis drugs. Here we describe a method for screening and quantifying the vascular endothelial growth factor (VEGF)-induced chemotactic response on human umbilical vein endothelial cells (HUVECs) cultured with different concentrations of bortezomib, a selective 26S proteasome inhibitor. With this quantitative microfluidic angiogenesis screen (QMAS), we demonstrate that bortezomib-induced endothelial cell death is preceded by a series of morphological changes that develop over several days. We also explore the mechanisms by which bortezomib can inhibit angiogenesis.

Hydrogel-based diffusion chip with Electric Cell-substrate Impedance Sensing (ECIS) integration for cell viability assay and drug toxicity screening

In this study, we have provided a novel analytical integration between hydrogel-based cell chip and Electric Cell-substrate Impedance Sensing (ECIS) technique to apply to a high-throughput, real-time cell viability assay and drug screening. For simulating the drug diffusion model, we have developed a hydrogel-based tissue-mimicking structure with microfluidic channel, without unwanted flow, to generate a gradient concentration with long-term stability. Along the gradient line, four individual micro-electrodes were installed to record the impedance signal changes, which result from the cell viability under drug effects. By watching for cellular impedance changes, we successfully estimated the cytotoxicity of the treatment corresponding to the various concentration values of stimuli, generated by the diffusion process along the channel. Reliable IC50 values and time-dose relationships were also achieved. With the feature of real-time monitoring capability, the advantages of non-invasion, label-free detection, time saving and simple manipulation, our integrative device has become a promising high throughput cell-based on-chip platform for cell viability assay and drug screening.

On-chip anticancer drug test of regular tumor spheroids formed in microwells by a distributive microchannel network

This paper proposes a new cytotoxicity assay in a microfluidic device with microwells and a distributive microfluidic channel network for the formation of cancer cell spheroids. The assay can generate rapid and uniform cell clusters in microwells and test in situ cytotoxicity of anticancer drugs including sequential drug treatments, long term culture of spheroids and cell viability assays. Inlet ports are connected to the microwells by a hydraulic resistance network. This uniform distribution of cell suspensions results in regular spheroid dimensions. Injected cancer cells were trapped in microwells, and aggregated into tumor spheroids within 3 days. A cytotoxicity test of the spheroids in microwells was subsequently processed in the same device without the extraction of cells. The in situ cytotoxicity assay of tumor spheroids in microwells was comparable with the MTT assay on hanging drop spheroids using a conventional 96-well plate. It was observed that the inhibition rate of the spheroids was less than that in the 2D culture dish and the effect on tumor spheroids was different depending on the anticancer drug. This device could provide a convenient in situ assay tool to assess the cytotoxicity of anticancer drugs on tumor spheroids, offering more information than the conventional 2D culture plate.

Molecular mechanisms of cisplatin resistance in bladder cancer

Metastatic disease is the most common mechanism of death in patients with advanced bladder cancer. As for most solid tumors, chemotherapy remains the only realistic option for palliating or curing metastatic disease. However, bladder cancer is characterized by chemoresistance. Only modest response rates are obtained using multiagent regimens including cisplatin. These low response rates and the toxicity of these regimens limit their use to patients at highest risk. Here, we review the molecular mechanisms of cisplatin resistance. These include methods to reduce cisplatin bioavailability within a cell, and defects in the machinery that produces cell death following cisplatin-induced DNA damage. While overcoming these mechanisms is a potential therapeutic approach that can increase response rates, in the short term this knowledge could be used to predict response in individual tumors.

P-glycoprotein, multidrug-resistance associated protein 2, Cyp3a, and carboxylesterase affect the oral availability and metabolism of vinorelbine

We investigated the interactions of the anticancer drug vinorelbine with drug efflux transporters and cytochrome P450 3A drug-metabolizing enzymes. Vinorelbine was transported by human multidrug-resistance associated protein (MRP) 2, and Mrp2 knockout mice displayed increased vinorelbine plasma exposure after oral administration, suggesting that Mrp2 limits the intestinal uptake of vinorelbine. Using P-glycoprotein (P-gp), Cyp3a-, and P-gp/Cyp3a knockout mice, we found that the absence of P-gp or Cyp3a resulted in increased vinorelbine plasma exposure, both after oral and intravenous administration. Surprisingly, P-gp/Cyp3a knockout mice displayed markedly lower vinorelbine plasma concentrations than wild-type mice upon intravenous administration but higher concentrations upon oral administration. This could be explained by highly increased formation of 4'-O-deacetylvinorelbine, an active vinorelbine metabolite, especially in P-gp/Cyp3a knockout plasma. Using wild-type and Cyp3a knockout liver microsomes, we found that 4'-O-deacetylvinorelbine formation was 4-fold increased in Cyp3a knockout liver and was not mediated by Cyp3a or other cytochrome P450 enzymes. In vitro incubation of vinorelbine with plasma revealed that vinorelbine deacetylation in Cyp3a and especially in P-gp/Cyp3a knockout mice but not in P-gp-deficient mice was strongly up-regulated. Metabolite formation in microsomes and plasma could be completely inhibited with the nonspecific carboxylesterase (CES) inhibitor bis(4-nitrophenyl) phosphate and partly with the CES2-specific inhibitor loperamide, indicating that carboxylesterase Ces2a, which was appropriately up-regulated in Cyp3a and especially in P-gp/Cyp3a knockout liver was responsible for the 4'O-deacetylvinorelbine formation. Such compensatory up-regulation can complicate the interpretation of knockout mouse data. Nonetheless, P-gp, Mrp2, Cyp3a, and Ces2a clearly restricted vinorelbine availability in mice. Variation in activity of their human homologs may also affect vinorelbine pharmacokinetics in patients.

Effects of α-adrenoceptor antagonists on ABCG2/BCRP-mediated resistance and transport

Acquired resistance of cancer cells to various chemotherapeutic agents is known as multidrug resistance, and remains a critical factor in the success of cancer treatment. It is necessary to develop the inhibitors for multidrug resistance. The aim of this study was to examine the effects of eight α-adrenoceptor antagonists on ABCG2/BCRP-mediated resistance and transport. Previously established HeLa/SN100 cells, which overexpress ABCG2/BCRP but not ABCB1/MDR1, were used. The effects of the antagonists on sensitivity to mitoxantrone and the transport activity of Hoehst33342, both substrates for ABCG2/BCRP, were evaluated using the WST-1 assay and cellular kinetics, respectively. ABCG2/BCRP mRNA expression and the cell cycle were also examined by real-time RT-PCR and flow cytometry, respectively. Sensitivity to mitoxantrone was reversed by the α-adrenoceptor antagonists in a concentration-dependent manner, although such effects were also found in the parental HeLa cells. Levels of ABCG2/BCRP mRNA expression were not influenced by the antagonists. The transport activity of Hoechst33342 was decreased by doxazosin and prazosin, but unaffected by the other antagonists. In addition, doxazosin and prazosin increased the proportion of S phase cells in the cultures treated with mitoxantrone, whereas the other α-adrenoceptor antagonists increased the percentage of cells in G₂/M phase. These findings suggested that doxazosin and prazosin reversed resistance mainly by inhibiting ABCG2/BCRP-mediated transport, but the others affected sensitivity to mitoxantrone via a different mechanism.

Engineering of targeted nanoparticles for cancer therapy using internalizing aptamers isolated by cell-uptake selection

One of the major challenges in the development of targeted nanoparticles (NPs) for cancer therapy is to discover targeting ligands that allow for differential binding and uptake by the target cancer cells. Using prostate cancer (PCa) as a model disease, we developed a cell-uptake selection strategy to isolate PCa-specific internalizing 2'-O-methyl RNA aptamers (Apts) for NP incorporation. Twelve cycles of selection and counter-selection were done to obtain a panel of internalizing Apts, which can distinguish PCa cells from nonprostate and normal prostate cells. After Apt characterization, size minimization, and conjugation of the Apts with fluorescently labeled polymeric NPs, the NP-Apt conjugates exhibit PCa specificity and enhancement in cellular uptake when compared to nontargeted NPs lacking the internalizing Apts. Furthermore, when docetaxel, a chemotherapeutic agent used for the treatment of PCa, was encapsulated within the NP-Apt, a significant improvement in cytotoxicity was achieved in targeted PCa cells. Rather than isolating high-affinity Apts as reported in previous selection processes, our selection strategy was designed to enrich cancer cell-specific internalizing Apts. A similar cell-uptake selection strategy may be used to develop specific internalizing ligands for a myriad of other diseases and can potentially facilitate delivering various molecules, including drugs and siRNAs, into target cells.

Controlling mass transport in microfluidic devices

Microfluidic platforms offer exquisite capabilities in controlling mass transport for biological studies. In this review, we focus on recent developments in manipulating chemical concentrations at the microscale. Some techniques prevent or accelerate mixing, whereas others shape the concentration gradients of chemical and biological molecules. We also highlight several in vitro biological studies in the areas of organ engineering, cancer, and blood coagulation that have benefited from accurate control of mass transfer.

Ascorbate exerts anti-proliferative effects through cell cycle inhibition and sensitizes tumor cells towards cytostatic drugs

Purpose

While the benefits of ascorbic acid (vitamin C, ascorbate) as an essential nutrient are well established, its effects on tumor cells and in tumor treatment are controversial. In particular, conflicting data exist whether ascorbate may increase the cytotoxic effects of antineoplastic drugs or may rather exert adverse effects on drug sensitivity during cancer treatment. Findings are further obscured regarding the distinction between ascorbate and dehydroascorbate (DHA). Thus, the purpose of this study was to evaluate and directly compare the cytotoxic efficacy of ascorbate compared to DHA, and to analyse if ascorbate at pharmacological concentrations affects the efficacy of antineoplastic agents in prostate carcinoma cells.

Methods

We directly compare the effects of ascorbate (supplied as ‘Pascorbin^® solution for injection’) and DHA on tumor cell viability, and determine IC₅₀ values for various cell lines. At concentrations well below the IC₅₀, ascorbate effects on cell proliferation and cell cycle are analysed. We furthermore determine changes in cellular sensitivity towards various cytostatic drugs upon pre-treatment of cells with ascorbate.

Results

We demonstrate higher therapeutic efficacy of ascorbate over DHA in various cell lines, independent of cell line-specific differences in ascorbate sensitivity, and identify the extracellular generation of H₂O₂ as critical mechanism of ascorbate action. We furthermore show that, in addition to pro-apoptotic effects described previously, ascorbate treatment already at concentrations well below the IC₅₀ exerts anti-proliferative effects on tumor cells. Those are based on interference with the cell cycle, namely by inducing a G₀/G₁ arrest. Pre-treatment of tumor cells with ascorbate leads to increased cellular sensitivity towards Docetaxel, Epirubicin, Irinotecan and 5-FU, but not towards Oxaliplatin and Vinorelbin. For Docetaxel and 5-FU, a linear correlation between this sensitizing effect and the ascorbate dosage is observed.

Conclusions

The redox-active form of vitamin C, ascorbate, shows therapeutic efficacy in tumor cells. These antitumor effects of ascorbate are mainly based on its extracellular action and, in addition to the induction of apoptosis, also include an anti-proliferative effect by inducing cell cycle arrest. Furthermore, ascorbate treatment specifically enhances the cytostatic potency of certain chemotherapeutics, which implicates therapeutic benefit during tumor treatment.

Electronic supplementary material

The online version of this article (doi:10.1007/s00280-010-1418-6) contains supplementary material, which is available to authorized users.

Generation of arbitrary monotonic concentration profiles by a serial dilution microfluidic network composed of microchannels with a high fluidic-resistance ratio

This paper reports a serial dilution microfluidic network composed of microchannels with a high fluidic-resistance ratio for generating linear concentration profiles as well as logarithmic concentration profiles spanning 3 and 6 orders of magnitude. The microfluidic networks were composed of thin fluidic-resistance microchannels with 160 to 730 microm(2) cross-sectional areas and thick diffusion-mixing microchannels with 3,600 to 17,000 microm(2) cross-sectional areas, and were fabricated from polydimethylsiloxane by multilayer photolithography and replica molding. We proposed a design algorithm of the microfluidic network for an arbitrary monotonic concentration profile by means of a hydrodynamic calculation. Because of the high fluidic-resistance ratio of the fluidic-resistance microchannels to the diffusion-mixing microchannels, appropriate geometry and dimensions of the fluidic-resistance microchannels allowed us to obtain desired concentration profiles. The fabricated microfluidic network was compact, occupying a 8 x 18 to 21.0 x 13.5 mm(2) area on the microchip. Both the linear and the logarithmic concentration profiles were successfully generated with the error less than 15% for the linear concentration profile, 22% and 35% for the logarithmic concentration profiles of 3 and 6 orders of magnitude, respectively. The generated linear concentration profiles of the small molecule, calcein, were independent of the flow rate within the range of 0.009 to 0.23 microL/min. The concentration profiles of the large molecules, dextrans, depended on the flow rate and molecular weight. The required residence time of large molecules in the diffusion-mixing microchannel was correlated with dimensionless diffusion time, Fick number, and was discussed based on the scaling law. These compact, stable serial dilution microfluidic networks are expected to be applied to various integrated on-chip analyses.

Actinomycin D identified as an inhibitor of discoidin domain receptor 2 interaction with collagen through an insect cell based screening of a drug compound library

Discoidin domain receptors belong to the cell surface receptor tyrosine kinase family and recognize collagens for their activating ligands. They have been implicated for cell growth and migration and their elevated expressions were observed in various human cancers. When we expressed human Discoidin domain receptor 2 (DDR2) in insect cells, the protein was targeted properly into the cell membrane and this could enforce the cells to adhere on culture plate coated with type I collagen. By taking advantage of this, we established a novel insect cell based screening protocol to identify chemicals which inhibit the interaction between DDR2 and collagen. We screened a drug-compound library to select an anti-cancer drug, actinomycin D, as the inhibitory compound. Actinomycin D prevented the activation of DDR2 by type I collagen in human embryonic kidney 293 cells with an IC(50) value of 9 microM, while it did not interfere with the activation of other receptor tyrosine kinases by their ligands. In conclusion we identified a new biological function of actinomycin D and the insect cell based method provides a useful protocol for screening inhibitors against the association of DDR2 with collagen.

Malaria-infected mice are cured by a single oral dose of new dimeric trioxane sulfones which are also selectively and powerfully cytotoxic to cancer cells

A new series of 6 dimeric trioxane sulfones has been prepared from the natural trioxane artemisinin in five or six chemical steps. One of these thermally and hydrolytically stable new chemical entities (4c) completely cured malaria-infected mice via a single oral dose of 144 mg/kg. At a much lower single oral dose of only 54 mg/kg combined with 13 mg/kg of mefloquine hydrochloride, this trioxane dimer 4c as well as its parent trioxane dimer 4b also completely cured malaria-infected mice. Both dimers 4c and 4b were potently and selectively cytotoxic toward five cancer cell lines.

Next-generation anthracycline for the management of small cell lung cancer: focus on amrubicin

Amrubicin is a totally synthetic anthracycline anticancer agent that acts as a potent topoisomerase II inhibitor. Amrubicin has been approved in Japan for the treatment of lung cancer, and the results from clinical studies of amrubicin as a single agent or as part of combination regimens for lung cancer, particularly for small cell lung cancer, conducted in Japan and overseas have been promising. Amrubicin should be included among new treatment strategies especially for chemoresistant patients. Here, preclinical, pharmacological, and clinical data on the use of amrubicin for the treatment of small cell lung cancer are reviewed.