Preclinical perspectives on platinum resistance

Carbohydrate-based heteronuclear complexes as topoisomerase Iα inhibitor: approach toward anticancer chemotherapeutics

Due to the critical role of cellular enzymes necessary for cell proliferation by deciphering topological hurdles in the process of DNA replication, topoisomerases have been one of the major targets in the anticancer drug development area. A need, therefore, arises for new metallodrugs that specifically recognizes DNA and inhibits the activity of topoisomerase enzymes, herein, we report the synthesis and characterization of new metal-based glycoconjugate entities containing heterobimetallic core Cu^II-Sn^IV (1) and Ni^II-Sn^IV (2) derived from N-glycoside ligand (L). The optimized structure of complex 1 and other significant vibrational modes have been explained using dispersion corrected B3LYP/DFT calculations. In vitro DNA binding profile of the L and both the complexes 1 and 2 were done by various biophysical studies. Complex 1 breaks pBR322 DNA via a hydrolytic means which was validated by T4 DNA enzymatic assay. To get a mechanistic insight of mode of action topoisomerase I (Topo I) inhibition assay was carried out. Also, we have taken the help of molecular modeling studies in accordance with experimental findings. In vitro cytotoxicity of the complex 1 was evaluated against a panel of cancer cells which exhibited remarkably good anticancer activity (GI₅₀ values <10 μg/ml). Moreover, intracellular localization of the complex 1 was visualized by confocal microscopy against HeLa cells.

Desferal regulates hCtr1 and transferrin receptor expression through Sp1 and exhibits synergistic cytotoxicity with platinum drugs in oxaliplatin-resistant human cervical cancer cells in vitro and in vivo

The development of resistance to platinum drugs in cancer cells severely reduces the efficacy of these drugs. Thus, the discovery of novel drugs or combined strategies to overcome drug resistance is imperative. In addition to our previous finding that combined D-penicillamine with platinum drugs exerts synergistic cytotoxicity, we recently identified a novel therapeutic strategy by combining an iron chelating agent desferal with platinum drugs to overcome platinum resistance in an oxaliplatin-resistant human cervical cancer cell line, S3. Further study demonstrated that the level of platinum–DNA adduct formation positively correlated with cell death in combination of desferal with platinums than that of each drug alone in S3 cells. Decrement of human copper transporter 1 (hCtr1) and transferrin receptor 1 (TfR1) expression involved in the development of platinum resistance in S3 cells. Moreover, desferal promoted the expression of hCtr1 through the upregulation of Sp1. The overexpression of Sp1 increased the expression of NF-κB and translocated it into the nucleus to bind to the TfR1 promoter region, which subsequently increased the expression of TfR1. Importantly, the cotreatment of oxaliplatin with desferal significantly potentiated the oxaliplatin-elicited antitumoral effect in the oxaliplatin-resistant xenograft animal model without any toxic effect observed. Taken together, these results demonstrated that the combination of desferal with oxaliplatin can overcome oxaliplatin resistance through the regulation of hCtr1 and TfR1, and may have beneficial effect for treatment of patient with oxaliplatin-refractory tumors.

Alkaloids from Stephania venosa as Chemo-Sensitizers in SKOV3 Ovarian Cancer Cells via Akt/NF-κB Signaling

Crebanine (CN), tetrahydropalmatine (THP), O-methylbulbocapnine (OMBC) and N-methyl tetrahydropalmatine (NMTHP) are isoquinoline derived natural alkaloids isolated from tubers of Stephania venosa. We investigated chemo-sensitizing effects of these alkaloids in ovarian cancer cells and evaluated underlying molecular mechanisms involved in chemo-sensitivity. Detection of cell apoptosis was evaluated by using flow cytometry. Cell viability was analyzed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Chou-Talalay median effect principle was used to evaluate potential drug interactions. Protein analyses were performed on ovarian carcinoma cells using Western blotting upon treatment with anticancer drug and alkaloids. Aporphine alkaloids, such as CN and OMBC, enhanced cisplatin sensitivity in intrinsic cisplatin resistant SKOV3 cells, but not in cisplatin sensitive A2780 cells. Protoberberine alkaloids, such as THP and NMTHP, had no synergistic effect on cisplatin sensitivity in either cell line. Chemo-sensitizing effects of CN and OMBC in SKOV3 cells were mediated via activating apoptosis-induced cell death through caspase-3, -8 and cleaved poly ADP-ribose polymerase (PARP) and via inhibiting anti-apopotic and survival protein expression, such as Bcl-xL, Baculoviral IAP repeat-containing protein 3 (cIAP-2), survivin and interleukin (IL) -6. Cisplatin stimulated protein kinase B (Akt) and nuclear factor-kappaB (NF-κB) signaling pathways, but not mitogen-activated protein kinase (MAPK), activator protein 1 (AP-1) and signal transducer and activator of transcription 3 (STAT3) in SKOV3 cells. Akt/NF-κB signaling was blocked by CN and OMBC leading to increased sensitization to cisplatin. These findings demonstrate that CN and OMBC sensitizes SKOV3 cells to cisplatin via inhibition of Akt/NF-κB signaling and the down regulation of NF-κB mediated gene products. Our results suggest that alkaloids obtained from S. venosa could be used as chemo-sensitizers in ovarian cancer to sensitize and minimize the dose related toxicity of platinum-based chemotherapeutic drugs.

A new class of platinum(ii) complexes with the phosphine ligand pta which show potent anticancer activity

A series of 16 Pt(ii) complexes with 8-hydroxyquinolines and sulfoxide/phosphine ligands were synthetized, characterized and evaluated for cytotoxic and embryotoxic activity.

Copper(II) complexes based on tripodal pyrazolyl amines: Synthesis, structure, magnetic properties and anticancer activity

The Cu(II) complexes [Cu(bpdmpz)Cl]ClO₄ (1), [Cu(bdmpzp)Cl]ClO₄ (2-ClO₄), [Cu(bdmpzp)Cl]PF₆ (2-PF₆) and [Cu(tdmpza)Cl]ClO₄ (3), bpdmpzp=[bis[((2-pyridylmethyl)-di(3,5-dimethyl-1H-pyrazolyl)methyl)]amine, bdmpzp=[bis((di(3,5-dimethyl-1H-pyrazolyl)methyl)-(2-pyridylmethyl)]amine and tdmpza=tris[di(3,5-dimethyl-1H-pyrazolyl)-methyl)]amine were synthesized and characterized by elemental analysis, magnetic and conductivity measurements, electrospray-ionization mass spectrometry, infrared and electronic spectroscopy, and X-ray crystallography. The magnetic properties of the complexes, measured at variable temperature, revealed weak antiferromagnetic intermolecular interactions. The cytotoxicity of the complexes 1, 2-ClO₄, 3, and 4 ([Cu(bedmpzp)Cl]PF₆, where bedmpzp=[bis(3,5-dimethyl-1H-pyrazol-1-yl-1-ethyl)-(2-pyridylmethyl)]amine), was investigated against four human cancer cell lines: A2780 (ovarian), A2780R (cisplatin-resistant variant), HOS (aggressive bone tumors), CaCo2 (epithelial colorectal adenocarcinoma) and on healthy human hepatocytes. The complex 4 was the most cytotoxic one, with IC₅₀=1.4μM (A2780), 8.3μM (A2780R), 4.7μM (HOS) and 10.8μM (CaCo2). The mass spectrometry-based interaction studies, involving selected sulfur-containing biomolecules and small model proteins, revealed pro-oxidant effects of complexes 1 and 4 and differences in stability of both complexes in the mixtures containing the model protein cytochrome c after 24h incubation, complex 1 formed 1:1 adduct, the formation of which was accompanied by the loss of one dimethylpyrazole pendant arm from the bpdmpz ligand, while the complex 4 composition remained intact and the complex formed both 1:1 and 1:2 adducts (cytochrome c vs. Cu(II)-complex).

Drug Delivery Strategies for Platinum-Based Chemotherapy

Few chemotherapeutics have had such an impact on cancer management as cis-diamminedichloridoplatinum(II) (CDDP), also known as cisplatin. The first member of the platinum-based drug family, CDDP's potent toxicity in disrupting DNA replication has led to its widespread use in multidrug therapies, with particular benefit in patients with testicular cancers. However, CDDP also produces significant side effects that limit the maximum systemic dose. Various strategies have been developed to address this challenge including encapsulation within micro- or nanocarriers and the use of external stimuli such as ultrasound to promote uptake and release. The aim of this review is to look at these strategies and recent scientific and clinical developments.

Carbon nanotube capsules enhance the in vivo efficacy of cisplatin

Over the past few years, numerous nanotechnology-based drug delivery systems have been developed in an effort to maximize therapeutic effectiveness of conventional drug delivery, while limiting undesirable side effects. Among these, carbon nanotubes (CNTs) are of special interest as potential drug delivery agents due to their numerous unique and advantageous physical and chemical properties. Here, we show in vivo favorable biodistribution and enhanced therapeutic efficacy of cisplatin (CDDP) encapsulated within ultra-short single-walled carbon nanotube capsules (CDDP@US-tubes) using three different human breast cancer xenograft models. In general, the CDDP@US-tubes demonstrated greater efficacy in suppressing tumor growth than free CDDP in both MCF-7 cell line xenograft and BCM-4272 patient-derived xenograft (PDX) models. The CDDP@US-tubes also demonstrated a prolonged circulation time compared to free CDDP which enhanced permeability and retention (EPR) effects resulting in significantly more CDDP accumulation in tumors, as determined by platinum (Pt) analysis via inductively-coupled plasma mass spectrometry (ICP-MS).

STATEMENT OF SIGNIFICANCE

Over the past decade, drug-loaded nanocarriers have been widely fabricated and studied to enhance tumor specific delivery. Among the diverse classes of nanomaterials, carbon nanotubes (CNTs), or more specifically ultra-short single-walled carbon nanocapsules (US-tubes), have been shown to be a popular, new platform for the delivery of various medical agents for both imaging and therapeutic purposes. Here, for the first time, we have shown that US-tubes can be utilized as a drug delivery platform in vivo to deliver the chemotherapeutic drug, cisplatin (CDDP) as CDDP@US-tubes. The studies have demonstrated the ability of the US-tube platform to promote the delivery of encapsulated CDDP by increasing the accumulation of drug in breast cancer resistance cells, which reveals how CDDP@US-tubes help overcome CDDP resistance.

Chitosan nanoparticle-delivered siRNA reduces CXCR4 expression and sensitizes breast cancer cells to cisplatin

Chemokine (C-X-C motif) receptor 4 (CXCR4) has been reported as a poor prognostic biomarker in human breast cancers, and has been suggested as a promising therapeutic target of breast cancer treatment. The present study aims to investigate the delivery efficiency of siRNA by chitosan into breast cancer cells, and then to examine the regulatory role by chitosan nanoparticle-delivered siRNA on CXCR4 expression and on the chemosensitivity of breast cancer cells. Our results demonstrated that the siRNA could be capsuled by chitosan into nanoparticles with a diameter of 80-110 nm, and with a zeta potential of 20-50 mV. The chitosan nanoparticle delivered siRNA efficiently into breast cancer MCF-7 cells significantly reduced the expression of CXCR4 in both mRNA and protein levels. Moreover, the reduced CXCR4 by chitosan nanoparticle-delivered siRNA was associated with increased sensitivity of breast cancer cells to cisplatin. Reduced growth and increased apoptosis of MCF-7 cells were observed in the CXCR4 siRNA group than in the control siRNA group. Taken together, our results present the treatment potential of chitosan nanoparticle-delivered siRNA targeting CXCR4 in breast cancers.

New Acridine Thiourea Gold(I) Anticancer Agents: Targeting the Nucleus and Inhibiting Vasculogenic Mimicry

Two new 1-acridin-9-yl-3-methylthiourea Au(I) DNA intercalators [Au(ACRTU)₂]Cl (2) and [Au(ACRTU) (PPh₃)]PF₆ (3) have been prepared. Both complexes were highly active in the human ovarian carcinoma cisplatin-sensitive A2780 cell line, exhibiting IC₅₀ values in the submicromolar range. Compounds 2 and 3 are also cytotoxic toward different phenotypes of breast cancer cell lines MDA-MB-231 (triple negative), SK-BR-3 (HER2+, ERα-, and ERβ-), and MCF-7 (ER+). Both complexes induce apoptosis through activation of caspase-3 in vitro. While inhibition of some proteins (thiol-containing enzymes) seems to be the main mechanism of action for cytotoxic gold complexes, 2 and 3 present a DNA-dependent mechanism of action. They locate in the cell nucleus according to confocal microscopy and transmission electronic microscopy. The binding to DNA resulted to be via intercalation as shown by spectroscopic methods and viscometry, exhibiting a dose-dependent response on topoisomerase I mediated DNA unwinding. In addition, 2 and 3 exhibit potent antiangiogenic effects and are also able to inhibit vasculogenic mimicry of highly invasive MDA-MB-231 cells.

Ex Vivo Explant Cultures of Non-Small Cell Lung Carcinoma Enable Evaluation of Primary Tumor Responses to Anticancer Therapy

To improve treatment outcomes in non-small cell lung cancer (NSCLC), preclinical models that can better predict individual patient response to novel therapies are urgently needed. Using freshly resected tumor tissue, we describe an optimized ex vivo explant culture model that enables concurrent evaluation of NSCLC response to therapy while maintaining the tumor microenvironment. We found that approximately 70% of primary NSCLC specimens were amenable to explant culture with tissue integrity intact for up to 72 hours. Variations in cisplatin sensitivity were noted with approximately 50% of cases responding ex vivo Notably, explant responses to cisplatin correlated significantly with patient survival (P = 0.006) irrespective of tumor stage. In explant tissue, cisplatin-resistant tumors excluded platinum ions from tumor areas in contrast to cisplatin-sensitive tumors. Intact TP53 did not predict cisplatin sensitivity, but a positive correlation was observed between cisplatin sensitivity and TP53 mutation status (P = 0.003). Treatment of NSCLC explants with the targeted agent TRAIL revealed differential sensitivity with the majority of tumors resistant to single-agent or cisplatin combination therapy. Overall, our results validated a rapid, reproducible, and low-cost platform for assessing drug responses in patient tumors ex vivo, thereby enabling preclinical testing of novel drugs and helping stratify patients using biomarker evaluation. Cancer Res; 77(8); 2029-39. ©2017 AACR.

In Vitro DNA-Binding, Anti-Oxidant and Anticancer Activity of Indole-2-Carboxylic Acid Dinuclear Copper(II) Complexes

Indole-2-carboxylic acid copper complex (ICA-Cu) was successfully prepared and characterized through elemental analysis, IR, UV-Vis, ¹H-NMR, TG analysis, and molar conductance, and its molecular formula was [Cu₂(C₉H₆O₂N)₄(H₂O)₂]·2H₂O. The binding ability of ICA-Cu to calf thymus DNA (CT-DNA) was examined by fluorescence spectrometry and the viscosity method. The results indicated that, upon the addition of increasing amounts of CT-DNA, the excitation and emission intensity of ICA-Cu decreased obviously and the excitation spectra shifted towards a long wavelength. ICA-Cu could displace ethidium bromide (EB) from the EB-DNA system, making the fluorescence intensity of the EB-DNA system decrease sharply; the quenching constant KSV value was 3.99 × 10⁴ M-1. The emission intensity of the ICA-Cu-DNA system was nearly constant, along with the addition of Na⁺ in a series of concentrations. The fluorescence of the complex could be protected after the complex interacted with DNA. A viscosity measurement further supported the result that the ICA-Cu complex may interact with DNA in an intercalative binding mode. The antioxidant activities of ICA-Cu were evaluated by a 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, a hydroxyl radical (OH) scavenging assay, and a 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) assay. The ICA-Cu exhibited the highest inhibitory effects on the ABTS radical (94% inhibition at 60 µM), followed by OH and DPPH radicals (the degrees of inhibition being 71% and 56%, respectively). The in vitro cytotoxicity activity of ICA-Cu against two human breast cancer cell lines, MDA-MB-231 and MCF-7, was investigated by 3-[4,5-dimethyltiazol2-yl]-2.5-diphenyl-tetrazolium bromide (MTT) assay and cellular morphological analysis. The results showed that, upon increasing the concentration of ICA-Cu, an increase was observed in growth-inhibitory activity and the inhibition percentage were greater than 90% at 20 µM in both cell lines. Also, cellular morphological changes in the two cell lines agreed with the cytotoxicity results.

Inhibition of glucose-6-phosphate dehydrogenase sensitizes cisplatin-resistant cells to death

The mechanisms of cisplatin resistance, one of the major limitations of current chemotherapy, has only partially been described. We previously demonstrated that cisplatin-resistant ovarian cancer cells (C13), are characterized by reduced mitochondrial activity and higher glucose-dependency when compared to the cisplatin-sensitive counterpart (2008). In this work we further characterized the role of metabolic transformation in cisplatin resistance. By using transmitochondrial hybrids we show that metabolic reprogramming of cisplatin-resistant cell is not caused by inherent mtDNA mutations. We also found that C13 cells not only present an increased glucose-uptake and consumption, but also exhibit increased expression and enzymatic activity of the Pentose Phosphate pathway (PPP) enzyme Glucose-6-Phosphate Dehydrogenase (G6PDH). Moreover, we show that cisplatin-resistant cells are more sensitive to G6PDH inhibition. Even if the metabolomic fingerprint of ovarian cancer cells remains to be further elucidated, these findings indicate that PPP offers innovative potential targets to overcome cisplatin resistance.

Anticancer activity of a chelating nitrogen mustard bearing tetrachloridoplatinum(iv) complex: better stability yet equipotent to the Pt(ii) analogue

Two Pt(iv) complexes cis,cis,trans-[Pt(IV)(L1)Cl4] (1a) & cis,cis,trans-[Pt(IV)(L2)Cl4] (2a) containing the nitrogen mustard moieties -N(CH2CH2Cl)2 & -NHCH2CH2Cl, were prepared in a single step from the Pt(ii) complexes containing -N(CH2CH2OH)2 (1) & -NHCH2CH2OH (2) moieties respectively using only thionyl chloride. The characterization of both the Pt(iv) complexes was performed by NMR, IR, UV and elemental analysis. Complex 1a was also characterized by single crystal X-ray diffraction. 1a crystallized in the I2/a space group. 1a exhibited much higher solution stability than 2a in kinetic studies by (1)H NMR. 1a shows a prodrug like activity as it converts to its Pt(ii) congener, [Pt(II)(L1)Cl2] (3) after 2 days in buffered solution. The binding experiment of 1a with model nucleobase 9-ethylguanine (9-EtG), showed that 1a converts to 3 and forms mono-adducts with 9-EtG. In the presence of reduced glutathione (GSH), the formation of 3 from 1a is quicker and upon the formation of 3 it binds almost instantaneously to GSH to form cis-[PtCl(L1)SG] (3c). Complex 3c transformed within a day to give a free aziridinium ion of L1 (3b) by dissociation. The in vitro cytotoxicity of the complexes and the clinical anticancer drug cisplatin show that 1a is potent against MCF-7, A549, HepG2 and MIA PaCa-2. The potency is highest against MIA PaCa-2 exhibiting an IC50 value of 4.4 ± 0.5 μM. The in vitro cytotoxicity data also showed that between the two complexes only 1a is active against MCF-7, A549 and MIA PaCa-2 in normoxia and hypoxia, both in the presence and absence of added GSH. Even in the presence of excess GSH in hypoxia, 1a exhibits significant cytotoxicity against MIA PaCa-2 and MCF-7 with IC50 values of 4.5 ± 0.3 and 11.2 ± 1.8 μM respectively. Platinum accumulation studies by ICP-MS display greater internalization of 1a, than 2a, 3 and cisplatin inside MCF-7 cells. 1a arrests cell cycle at the G2/M phase in MCF-7, exhibits capability to inhibit metastasis, induces apoptotic cell death and displays blood compatibility with human blood.

Platinum-based chemotherapy in advanced non-small-cell lung cancer: optimal number of treatment cycles

Platinum-based chemotherapy remains the standard-of-care for most patients affected by advanced non-small cell lung cancer (NSCLC). The platinum compounds currently used in NSCLC are cisplatin and carboplatin. The availability of new generation drugs has led to the adoption of schedules with lower doses of platinum compounds leading to increased tolerability. Several data suggest that third generation cisplatin-based regimens are slightly superior to carboplatin-based chemotherapy, with a different safety profile, and so cisplatin should remain the standard reference for the treatment of selected patients with advanced NSCLC. Recent evidence emphasized that the optimal number of first-line platinum cycles should be four for any NSCLC histology. New platinum compounds and the use of functional genomics to deliver platinum drugs as personalised medicine, are being investigated. Here we review the current status of cisplatin and carboplatin regimens looking to the future role of platinum compounds in advanced NSCLC patients.

miR-302b enhances breast cancer cell sensitivity to cisplatin by regulating E2F1 and the cellular DNA damage response

The identification of the molecular mechanisms involved in the establishment of the resistant phenotype represents a critical need for the development of new strategies to prevent or overcome cancer resistance to anti-neoplastic treatments.Breast cancer is the leading cause of cancer-related deaths in women, and resistance to chemotherapy negatively affects patient outcomes. Here, we investigated the potential role of miR-302b in the modulation of breast cancer cell resistance to cisplatin.miR-302b overexpression enhances sensitivity to cisplatin in breast cancer cell lines, reducing cell viability and proliferation in response to the treatment. We also identified E2F1, a master regulator of the G1/S transition, as a direct target gene of miR-302b. E2F1 transcriptionally activates ATM, the main cellular sensor of DNA damage. Through the negative regulation of E2F1, miR-302b indirectly affects ATM expression, abrogating cell-cycle progression upon cisplatin treatment. Moreover miR-302b, impairs the ability of breast cancer cells to repair damaged DNA, enhancing apoptosis activation following cisplatin treatment.These findings indicate that miR-302b plays a relevant role in breast cancer cell response to cisplatin through the modulation of the E2F1/ATM axis, representing a valid candidate as therapeutic tool to overcome chemotherapy resistance.

Highly potent extranuclear-targeted luminescent iridium(iii) antitumor agents containing benzimidazole-based ligands with a handle for functionalization

This discovery could open the door to a new large family of multifunctional bioconjugated drugs.

HNF1β drives glutathione (GSH) synthesis underlying intrinsic carboplatin resistance of ovarian clear cell carcinoma (OCCC)

Chemoresistance to platinum-based antineoplastic agents is a consistent feature among ovarian carcinomas; however, whereas high-grade serous carcinoma (OSC) acquires resistance during chemotherapy, ovarian clear cell carcinoma (OCCC) is intrinsically resistant. The main objective of this study was to explore, in vitro and in vivo, if hepatocyte nuclear factor 1β (HNF1β) and glutaminolysis contribute for the resistance of OCCC to carboplatin through the intrinsically increased GSH bioavailability. To disclose the role of HNF1β, experiments were also performed in an OSC cell line, which does not express HNF1β. Metabolic profiles, GSH quantification, HNF1β, and γ-glutamylcysteine ligase catalytic subunit (GCLC) and modifier subunit (GCLM) expression, cell cycle, and death were assessed in ES2 cell line (OCCC) and OVCAR3 cell line (OSC); HNF1β knockdown was performed in ES2 and murine model of subcutaneous and peritoneal OCCC tumors was established to test buthionine sulphoxamine (BSO), as a sensitizer to carboplatin. Glutaminolysis is activated in ES2 and OVCAR3, though ES2 exclusively synthesizes amino acids and GSH. ES2 cells are more resistant to carboplatin than OVCAR3 and the abrogation of GSH production by BSO sensitizes ES2 to carboplatin. HNF1β regulates the expression of GCLC, but not GCLM, and consequently GSH production in ES2. In vivo, BSO prior to carboplatin reduces dramatically subcutaneous tumor size and GSH levels, as well as peritoneal dissemination. Our study discloses HNF1β as the mediator of intrinsic OCCC chemoresistance and sheds a light to re-explore a cancer adjuvant therapeutic approach using BSO to overcome the lack of efficient therapy in OCCC.

Antitumor properties of platinum(iv) prodrug-loaded silk fibroin nanoparticles

Platinum(iv) complexes take advantage of the exclusive conditions that occur within the tumor to carry out their cytotoxic activity. On the other hand, silk fibroin has natural properties which make it very interesting as a biomaterial: high biocompatibility, biodegradability, low immunogenicity, high cellular penetration capacity and high reactive surface. Herein we report the preparation of silk fibroin nanoparticles (SFNs) loaded with the hydrophobic Pt(iv) complex cis,cis,trans-[Pt(NH(3))(2)Cl(2)(O(2)CC(6)H(5))(2)] (PtBz). Only a small fraction of the loaded PtBz is released (less than 10% after 48 h). PtBz-SFNs trigger strong cytotoxic effects against human ovarian carcinoma A2780 cells and their cisplatin-resistant variant A2780cisR cells. Interestingly, PtBz-SFNs are very cytotoxic (nanomolar IC(50) values) toward the triple negative breast tumor cell line MDA-MB-231, and also toward SK-BR-3 and MCF-7, while maintaining an excellent selectivity index.

Annexin A4 induces platinum resistance in a chloride-and calcium-dependent manner

Platinum resistance has long been a major issue in the treatment of various cancers. We previously reported that enhanced annexin A4 (ANXA4) expression, a Ca²⁺-regulated phospholipid-binding protein, induces chemoresistance to platinum-based drugs. In this study, we investigated the role of annexin repeats, a conserved structure of all the annexin family, responsible for platinum-resistance as well as the effect of knockdown of ANXA4. ANXA4 knockdown increased sensitivity to platinum-based drugs both in vitro and in vivo. To identify the domain responsible for chemoresistance, ANXA4 deletion mutants were constructed by deleting annexin repeats one by one from the C terminus. Platinum resistance was induced both in vitro and in vivo in cells expressing either full-length ANXA4 or the deletion mutants, containing at least one intact annexin repeat. However, cells expressing the mutant without any calcium-binding sites in the annexin repeated sequence, which is essential for ANXA4 translocation from the cytosol to plasma membrane, failed to acquire platinum resistance. After cisplatin treatment, the intracellular chloride ion concentration, whose channel is partly regulated by ANXA4, significantly increased in the platinum-resistant cells. These findings indicate that the calcium-binding site in the annexin repeat induces chemoresistance to the platinum-based drug by elevating the intracellular chloride concentration.

Mechanistic basis of a combination D-penicillamine and platinum drugs synergistically inhibits tumor growth in oxaliplatin-resistant human cervical cancer cells in vitro and in vivo

The platinum-based regimen is the front-line treatment of chemotherapy. However, development of platinum resistance often causes therapeutic failure in this disease. We previously have generated an oxaliplatin-resistant subline, named S3, from human cervical carcinoma SiHa cells, and its resistant phenotype was well-characterized. In the present study, we aimed to identify the novel therapeutic strategy by combining copper chelator D-penicillamine with oxaliplatin, and to elucidate the underlying mechanisms for overcoming oxaliplatin resistance. As the result, D-penicillamine exerted synergistic killing effects only in S3 cells when combined with oxaliplatin and cisplatin by using Chou-Talalay method. Further study showed that the amounts of platinum DNA adduct formed were positively correlated to the percentage of cell death in S3 cells when co-treated D-penicillamine with oxaliplatin and cisplatin. D-penicillamine promoted copper influx transporter hCtr1 expression through upregulation of Sp1. Sp1 overexpression induced p53 translocation from nucleus to cytosol and caused p53 degradation through ubiquitination, which subsequently suppressed the expression of the copper efflux transporter ATP7A. Importantly, co-treatment of cisplatin with D-penicillamine enhanced oxaliplatin-elicited antitumor effect in the oxalipatin-resistant S3 xenograft tumors, but not found in SiHa xenograft model. Notably, Mice received D-penicillamine alone or in combination of D-penicillamine ad oxalipatin, increased hCtrl protein level in S3 xenograft tumor, however, the protein level of ATP7A was decreased. Taken together, this study provides insight into that the co-manipulation of hCtrl and ATP7A by D-penicillamine could increase the therapeutic efficacy of platinum drugs in oxaliplatin resistant tumors, especially in resistant phenotype with downexpression of hCtrl and overexpression of ATP7A.

Silencing of CXCR4 sensitizes triple-negative breast cancer cells to cisplatin

Triple-negative breast cancer (TNBC) is an aggressive form of breast cancer for which there is no effective treatment. Previously, we and others demonstrated that CXCR4 surface expression is an independent prognostic factor for disease relapse and survival in breast cancer. In this study, we investigated the effects of CXCR4 gene silencing on cisplatin chemosensitivity in human triple-negative breast cancer cell lines. We found that CXCR4 silencing significantly inhibited cell growth, decreased colony formation, and enhanced cisplatin sensitivity while overexpression of CXCR4 rendered cells more resistant to cisplatin. Moreover, the percentage of apoptosis and cell cycle arrest at the G2/M phase of cisplatin-treated CXCR4 knockdown cells was significantly higher than control cells. Furthermore, we demonstrated CXCR4 knockdown cells showed lower levels of mutant p53 and Bcl-2 protein than the control group, while also having higher levels of caspase-3 and Bax. However overexpression of CXCR4 had the reverse effect. In vivo experiments confirmed that downregulation of CXCR4 enhanced cisplatin anticancer activity in tumor-bearing mice, and that this enhanced anticancer activity is attributable to tumor cell apoptosis. Thus, this study indicates that CXCR4 can modulate cisplatin sensitivity in TNBC cells and suggests that CXCR4 may be a therapeutic target for TNBC.

A mononuclear diketone-based oxido-vanadium(iv) complex: structure, DNA and BSA binding, molecular docking and anticancer activities against MCF-7, HPG-2, and HT-29 cell lines

A mononuclear oxido-vanadium(iv) complex, [VO(L)₂], has been synthesized and its interactions with DNA and BSA have been investigated experimentally and theoretically.

On the antitumor properties of novel cyclometalated benzimidazole Ru(II), Ir(III) and Rh(III) complexes

Smart design and efficient synthesis of benzimidazole Ru, Ir and Rh cyclometalated complexes are reported with promising cytotoxic activity against HT29, T47D, A2780 and A2780cisR cancer cell lines. Their apoptosis, accumulation, cell cycle arrest, protein binding and DNA binding effects are also discussed.

Systems biology of cisplatin resistance: past, present and future

The platinum derivative cis-diamminedichloroplatinum(II), best known as cisplatin, is currently employed for the clinical management of patients affected by testicular, ovarian, head and neck, colorectal, bladder and lung cancers. For a long time, the antineoplastic effects of cisplatin have been fully ascribed to its ability to generate unrepairable DNA lesions, hence inducing either a permanent proliferative arrest known as cellular senescence or the mitochondrial pathway of apoptosis. Accumulating evidence now suggests that the cytostatic and cytotoxic activity of cisplatin involves both a nuclear and a cytoplasmic component. Despite the unresolved issues regarding its mechanism of action, the administration of cisplatin is generally associated with high rates of clinical responses. However, in the vast majority of cases, malignant cells exposed to cisplatin activate a multipronged adaptive response that renders them less susceptible to the antiproliferative and cytotoxic effects of the drug, and eventually resume proliferation. Thus, a large fraction of cisplatin-treated patients is destined to experience therapeutic failure and tumor recurrence. Throughout the last four decades great efforts have been devoted to the characterization of the molecular mechanisms whereby neoplastic cells progressively lose their sensitivity to cisplatin. The advent of high-content and high-throughput screening technologies has accelerated the discovery of cell-intrinsic and cell-extrinsic pathways that may be targeted to prevent or reverse cisplatin resistance in cancer patients. Still, the multifactorial and redundant nature of this phenomenon poses a significant barrier against the identification of effective chemosensitization strategies. Here, we discuss recent systems biology studies aimed at deconvoluting the complex circuitries that underpin cisplatin resistance, and how their findings might drive the development of rational approaches to tackle this clinically relevant problem.

Conformation and recognition of DNA damaged by antitumor cis-dichlorido platinum(II) complex of CDK inhibitor bohemine

A substitution of the ammine ligands of cisplatin, cis-[Pt(NH3)2Cl2], for cyclin dependent kinase (CDK) inhibitor bohemine (boh), [2-(3-hydroxypropylamino)-6-benzylamino-9-isopropylpurine], results in a compound, cis-[Pt(boh)2Cl2] (C1), with the unique anticancer profile which may be associated with some features of the damaged DNA and/or its cellular processing (Travnicek Z et al. (2003) J Inorg Biochem94, 307-316; Liskova B (2012) Chem Res Toxicol25, 500-509). A combination of biochemical and molecular biology techniques was used to establish mechanistic differences between cisplatin and C1 with respect to the DNA damage they produce and their interactions with critical DNA-binding proteins, DNA-processing enzymes and glutathione. The results show that replacement of the NH3 groups in cisplatin by bohemine modulates some aspects of the mechanism of action of C1. More specifically, the results of the present work are consistent with the thesis that, in comparison with cisplatin, effects of other factors, such as: (i) slower rate of initial binding of C1 to DNA; (ii) the lower efficiency of C1 to form bifunctional adducts; (iii) the reduced bend of longitudinal DNA axis induced by the major 1,2-GG intrastrand cross-link of C1; (iv) the reduced affinity of HMG domain proteins to the major adduct of C1; (v) the enhanced efficiency of the DNA adducts of C1 to block DNA polymerization and to inhibit transcription activity of human RNA pol II and RNA transcription; (vi) slower rate of the reaction of C1 with glutathione, may partially contribute to the unique activity of C1.

Rational design of polyion complex nanoparticles to overcome cisplatin resistance in cancer therapy

Rationally designed PIC nanoparticles as next-generation delivery system: we have developed a core-shell-corona PIC nanoparticle (⊕) NP/Pt@PPC-DA as a next-generation delivery system. (⊕) NP/Pt@PPC-DA exhibits prolonged circulation and enhanced drug accumulation in tumors. Subsequently, tumor pH leads to the release of (⊕) NP/Pt, which facilitates cellular uptake followed by rapid intracellular cisplatin release. Using this delivery strategy cisplatin-resistant tumor growth in a murine xenograft model has been successfully suppressed.

Highly cytotoxic DNA-interacting copper(ii) coordination compounds

Copper complexes from Schiff-base ligands show high cytotoxicity against diverse cancer cell lines, with IC₅₀ values down to 0.23 μM.

XPG is a novel biomarker of clinical outcome in advanced non-small-cell lung cancer

Objective: Polymorphisms in XPG were considered to contribute to the clinical outcome of patients receiving platinum drug chemotherapy. We investigated the impact of several potential SNPs of XPG on the efficacy of platinum-based chemotherapy in NSCLC patients.

Methods: A total of 433 patients were consecutively selected between Nov. 2006 and Dec. 2007, and were followed-up up to Nov. 2011. The genotyping of six SNPs (rs2296147, rs751402, rs873601, rs4150375, rs17655 and rs2094258) were genotyped using the Taqman real-time PCR method with a 7900 HT sequence detector system.

Results: Patients carrying CT+TT genotype of rs2296147 had a significantly longer median PFS (17.5 months) and OS (26.8 months) than CC genotype. Hazard ratio (HR) for PFS and OS in patients with CT+TT genotype of rs2296147 was respectively 0.73(0.51-0.97) and 0.66(0.48-0.99) when compare CC genotype, respectively. Similarly, patients with rs2094258 AG+GG genotype had a longer median progression time (18.4 months) and overall survival time (27.3 months) when compared with those with AA genotype, and HRs(95% CI) for PFS and OS were 0.44(0.34-0.78) and 0.51(0.39-0.82), respectively.

Conclusions: Our study suggests rs2296147 CT+TT and rs2094258 AG+GG genotypes contribute to the better survival of NSCLC. Our study provides significant information on role of prognostic value of XPG SNPs, and detecting of XPG could be used as predictive markers toward individualizing NSCLC treatment strategies.

Nanocarriers for delivery of platinum anticancer drugs

Platinum based anticancer drugs have revolutionized cancer chemotherapy, and continue to be in widespread clinical use especially for management of tumors of the ovary, testes, and the head and neck. However, several dose limiting toxicities associated with platinum drug use, partial anti-tumor response in most patients, development of drug resistance, tumor relapse, and many other challenges have severely limited the patient quality of life. These limitations have motivated an extensive research effort towards development of new strategies for improving platinum therapy. Nanocarrier-based delivery of platinum compounds is one such area of intense research effort beginning to provide encouraging preclinical and clinical results and may allow the development of the next generation of platinum chemotherapy. This review highlights current understanding on the pharmacology and limitations of platinum compounds in clinical use, and provides a comprehensive analysis of various platinum-polymer complexes, micelles, dendrimers, liposomes and other nanoparticles currently under investigation for delivery of platinum drugs.

Upregulated expression of FGF13/FHF2 mediates resistance to platinum drugs in cervical cancer cells

Cancer cells often develop drug resistance. In cisplatin-resistant HeLa cisR cells, fibroblast growth factor 13 (FGF13/FHF2) gene and protein expression was strongly upregulated, and intracellular platinum concentrations were kept low. When the FGF13 expression was suppressed, both the cells' resistance to platinum drugs and their ability to keep intracellular platinum low were abolished. Overexpression of FGF13 in parent cells led to greater resistance to cisplatin and reductions in the intracellular platinum concentration. These cisplatin-resistant cells also showed increased resistance to copper. In preoperative cervical cancer biopsy samples from poor prognoses patients after cisplatin chemoradiotherapy, FGF13-positive cells were detected more abundantly than in the biopsy samples from patients with good prognoses. These results suggest that FGF13 plays a pivotal role in mediating resistance to platinum drugs, possibly via a mechanism shared by platinum and copper. Our results point to FGF13 as a novel target and useful prognostic guide for cancer therapy.

THEORETICAL STUDY ON THE BINDING OF THE ANTICANCER DRUGS Cis/Trans-[PtCl52(NH3){HN = C(CH3)2}] AND Cis/Trans-[PtCl2{HN = C(CH3)2}2] TO PURINE BASES

The monofunctional (the first substitution reactions) and bifunctional (the second substitution reactions) binding of the title antitumor drugs to purine bases were studied computationally by using density functional theory and IEF-PCM solvation models. For the first substitutions with guanine and adenine, our calculations demonstrate that the trans monoaqua and diaqua reactant complexes (RCs) can generate trans- or cis-monoadducts via identical or very similar trigonal-bipyramidal transition-state structures, predicting that the cis-monoadducts generated by trans RCs can subsequently close by coordination to the adjacent purine bases to form 1,2-intrastrand Pt –DNA adducts and eventually distort DNA in the same way as cisplatin. Thus it is likely that the transplatin analogues have the same mechanism of anticancer activity of cisplatin. In general, the monoaqua and diaqua monofunctional substitutions prefer guanine over adenine. The calculated lowest activation free energy in aqueous solution is 15.2 kcal/mol in the monoaqua substitutions (substituted by guanine from trans- [Pt{HN = C(CH3)2}2Cl(H2O)]+ to trans/cis-monoadduct), and 11.4 kcal/mol in the diaqua substitutions (substituted by guanine from cis- [Pt{HN = C(CH3)2}2(H2O)2]2+ to cis-monoadduct). For the second substitutions, all the reactants are started from the diaqua product complexes of the first substitutions substituted by guanine. The data obtained for the complexation energy difference between guanine and adenine RCs suggest that a thermodynamic favors the formation of GG over GA adducts by ∼ 5 - 12 kcal/mol in aqueous solution. Moreover, there is a kinetic preference for the formation of GG over GA adduct for the cis-monoadduct to cis-diadduct paths, while for the trans-monoadduct to trans-diadduct paths there is no certain trend biased toward GG adduct. In addition, the second substitutions of the trans-monoadduct to trans-diadduct paths have lower activation barriers than the corresponding cis-monoadduct to cis-diadduct paths. The lowest activation energy in the bifunctional substitutions from cis-monoadduct to cis-diadduct is 20.5 kcal/mol in the Pt (acetonimine)2GG2+ head-to-head (HH) path, while it is 17.7 kcal/mol from trans-monoadduct to trans-diadduct in the Pt(NH3) (acetonimine)GA2+ head-to-tail (HT) path. For the first and second substitutions, hydrogen-bonds play an important role in stabilizing these species.

Generation and characterisation of cisplatin-resistant non-small cell lung cancer cell lines displaying a stem-like signature

Introduction

Inherent and acquired cisplatin resistance reduces the effectiveness of this agent in the management of non-small cell lung cancer (NSCLC). Understanding the molecular mechanisms underlying this process may result in the development of novel agents to enhance the sensitivity of cisplatin.

Methods

An isogenic model of cisplatin resistance was generated in a panel of NSCLC cell lines (A549, SKMES-1, MOR, H460). Over a period of twelve months, cisplatin resistant (CisR) cell lines were derived from original, age-matched parent cells (PT) and subsequently characterized. Proliferation (MTT) and clonogenic survival assays (crystal violet) were carried out between PT and CisR cells. Cellular response to cisplatin-induced apoptosis and cell cycle distribution were examined by FACS analysis. A panel of cancer stem cell and pluripotent markers was examined in addition to the EMT proteins, c-Met and β-catenin. Cisplatin-DNA adduct formation, DNA damage (γH2AX) and cellular platinum uptake (ICP-MS) was also assessed.

Results

Characterisation studies demonstrated a decreased proliferative capacity of lung tumour cells in response to cisplatin, increased resistance to cisplatin-induced cell death, accumulation of resistant cells in the G0/G1 phase of the cell cycle and enhanced clonogenic survival ability. Moreover, resistant cells displayed a putative stem-like signature with increased expression of CD133+/CD44+cells and increased ALDH activity relative to their corresponding parental cells. The stem cell markers, Nanog, Oct-4 and SOX-2, were significantly upregulated as were the EMT markers, c-Met and β-catenin. While resistant sublines demonstrated decreased uptake of cisplatin in response to treatment, reduced cisplatin-GpG DNA adduct formation and significantly decreased γH2AX foci were observed compared to parental cell lines.

Conclusion

Our results identified cisplatin resistant subpopulations of NSCLC cells with a putative stem-like signature, providing a further understanding of the cellular events associated with the cisplatin resistance phenotype in lung cancer.