Cisplatin stops tubulin assembly into microtubules. A new insight into the mechanism of antitumor activity of platinum complexes

Cisplatin decreases voluntary wheel-running activity but does not impair food-motivated behavior in mice

Cisplatin is a chemotherapeutic agent that is still commonly used to treat solid tumors. However, it has several toxic side effects due in large part to the mitochondrial damage that it induces. As this mitochondrial damage is likely to result in a decrease in the amount of metabolic energy that is available for behavioral activities, it is not surprising that fatigue develops in cancer patients treated with cisplatin. The present preclinical study was initiated to determine whether the detrimental effects of cisplatin were more pronounced on physical effort requiring a lot of energy versus effort that not only requires less energy but also procures energy in the form of food. For this purpose, mice were either trained to run in a wheel or to work for food in various schedules of food reinforcement before being treated with cisplatin. The experiments were carried out only in male mice as we had already reported that sex differences in cisplatin-induced neurotoxicities are minimal. Cisplatin was administered daily for one cycle of five days, or two cycles separated by a five-day rest. As observed in previous experiments, cisplatin drastically reduced voluntary wheel running. In contrast, when cisplatin was administered to food-restricted mice trained to work for a food reward in a progressive ratio schedule or in a fixed-interval schedule, it tended to increase the number of responses emitted to obtain the food rewards. This increase was not associated with any change in the temporal distribution of responses during the interval between two reinforcements in mice submitted to the fixed interval schedule of food reinforcement. When cisplatin was administered to food-restricted mice trained in an effort-based decision-making task in which they had to choose between working for a grain pellet with little effort and working for a preferred chocolate pellet with more effort, it decreased the total number of responses emitted to obtain food rewards. However, this effect was much less marked than the decrease in wheel running induced by cisplatin. The decrease in the effort invested in the procurement of food rewards was not associated with any change in the relative distribution of effort between low reward and high reward during the time course of the test session. These findings show that cisplatin decreases energy-consuming activities but not energy-procuring activities unless they require a choice between options differing in their cost-benefit ratio. Furthermore, they indicate that the physical dimension of fatigue is more likely to develop in cisplatin-treated individuals than the motivational dimension of fatigue.

Simulation toolkits at the molecular scale for trans-scale thermal signaling

Thermogenesis is a physiological activity of releasing heat that originates from intracellular biochemical reactions. Recent experimental studies discovered that externally applied heat changes intracellular signaling locally, resulting in global changes in cell morphology and signaling. Therefore, we hypothesize an inevitable contribution of thermogenesis in modulating biological system functions throughout the spatial scales from molecules to individual organisms. One key issue examining the hypothesis, namely, the "trans-scale thermal signaling," resides at the molecular scale on the amount of heat released via individual reactions and by which mechanism the heat is employed for cellular function operations. This review introduces atomistic simulation tool kits for studying the mechanisms of thermal signaling processes at the molecular scale that even state-of-the-art experimental methodologies of today are hardly accessible. We consider biological processes and biomolecules as potential heat sources in cells, such as ATP/GTP hydrolysis and multiple biopolymer complex formation and disassembly. Microscopic heat release could be related to mesoscopic processes via thermal conductivity and thermal conductance. Additionally, theoretical simulations to estimate these thermal properties in biological membranes and proteins are introduced. Finally, we envisage the future direction of this research field.

Revisiting the Anti-Cancer Toxicity of Clinically Approved Platinating Derivatives

Cisplatin (CDDP), carboplatin (CP), and oxaliplatin (OXP) are three platinating agents clinically approved worldwide for use against a variety of cancers. They are canonically known as DNA damage inducers; however, that is only one of their mechanisms of cytotoxicity. CDDP mediates its effects through DNA damage-induced transcription inhibition and apoptotic signalling. In addition, CDDP targets the endoplasmic reticulum (ER) to induce ER stress, the mitochondria via mitochondrial DNA damage leading to ROS production, and the plasma membrane and cytoskeletal components. CP acts in a similar fashion to CDDP by inducing DNA damage, mitochondrial damage, and ER stress. Additionally, CP is also able to upregulate micro-RNA activity, enhancing intrinsic apoptosis. OXP, on the other hand, at first induces damage to all the same targets as CDDP and CP, yet it is also capable of inducing immunogenic cell death via ER stress and can decrease ribosome biogenesis through its nucleolar effects. In this comprehensive review, we provide detailed mechanisms of action for the three platinating agents, going beyond their nuclear effects to include their cytoplasmic impact within cancer cells. In addition, we cover their current clinical use and limitations, including side effects and mechanisms of resistance.

Alleviation of cisplatin-induced neuropathic pain, neuronal apoptosis, and systemic inflammation in mice by rapamycin

Platinum-based chemotherapeutic treatment of cancer patients is associated with debilitating adverse effects. Several adverse effects have been well investigated, and can be managed satisfactorily, but chemotherapy-induced peripheral neuropathy (CIPN) remains poorly treated. Our primary aim in this study was to investigate the neuroprotective effect of the immunomodulatory drug rapamycin in the mitigation of cisplatin-induced neurotoxicity. Pain assays were performed in vivo to determine whether rapamycin would prevent or significantly decrease cisplatin-induced neurotoxicity in adult male Balb/c mice. Neuropathic pain induced by both chronic and acute exposure to cisplatin was measured by hot plate assay, cold plate assay, tail-flick test, and plantar test. Rapamycin co-treatment resulted in significant reduction in cisplatin-induced nociceptive-like symptoms. To understand the underlying mechanisms behind rapamycin-mediated neuroprotection, we investigated its effect on certain inflammatory mediators implicated in the propagation of chemotherapy-induced neurotoxicity. Interestingly, cisplatin was found to significantly increase peripheral IL-17A expression and CD8- T cells, which were remarkably reversed by the pre-treatment of mice with rapamycin. In addition, rapamycin reduced the cisplatin-induced neuronal apoptosis marked by decreased neuronal caspase-3 activity. The rapamycin neuroprotective effect was also associated with reversal of the changes in protein expression of p21^Cip1, p53, and PUMA. Collectively, rapamycin alleviated some features of cisplatin-induced neurotoxicity in mice and can be further investigated for the treatment of cisplatin-induced peripheral neuropathy.

Prevention of anticancer therapy-induced neurotoxicity: putting DNA damage in perspective

Chemotherapy-induced peripheral neuropathy (CIPN) is a severe side effect of conventional cancer therapeutics (cAT) that significantly impacts the quality of life of tumor patients. The molecular mechanisms of CIPN are incompletely understood and there are no effective preventive or therapeutic measures available to date. Here, we present a brief overview of the current knowledge about mechanisms underlying CIPN and discuss DNA damage-related stress responses as feasible targets for the prevention of CIPN. In addition, we discuss that the nematode Caenorhabditis elegans is a useful 3R-conform model organism to further elucidate molecular mechanisms of CIPN and to identify novel lead compounds protecting from cAT-triggered neuropathy.

Chemotherapy-induced peripheral neuropathy and rehabilitation: A review

Chemotherapy-induced peripheral neuropathy (CIPN) is a common complication after chemotherapy that can damage the sensory, motor, autonomic, or cranial nerves in approximately 30%-60% of patients with cancer. CIPN can lead to detrimental dose modifications and/or premature chemotherapy discontinuation due to patient intolerance. The long-term impact of CIPN is particularly challenging and can have a profound impact on the quality of life (QoL) and survivorship. However, this condition is often underdiagnosed. No agents have been established to prevent CIPN. Pre-chemotherapy testing is recommended for high-risk patients. Duloxetine is considered a first-line treatment, whereas gabapentin, pregabalin, tricyclic antidepressants, and topical compounding creams may be used for neuropathic pain control. Home-based, low-to-moderate walking, and resistance exercise during chemotherapy can reduce the severity and prevalence of CIPN symptoms, especially in older patients. Pre-habilitation and rehabilitation should be recommended for all patients receiving cytotoxic chemotherapies. The purpose of this article is to review common chemotherapeutic drugs causing CIPN, risk factors, diagnosis and treatment of CIPN, and evidence of the benefits of rehabilitation.

Cisplatin Cytotoxicity in Human Testicular Germ Cell Tumor Cell Lines Is Enhanced by the CDK4/6 Inhibitor Palbociclib

BACKGROUND

Cisplatin-based chemotherapy is the mainstay of pharmacological treatment of testicular germ cell tumors (TGCTs) that, together with early diagnosis, surgery, and/or radiotherapy, has dramatically improved the prognosis. However, under the pressure of such pharmacological therapy (both classical cytotoxic drugs and targeted therapy), cancer cells may develop resistance. Thus, combination therapy that may include cytotoxic drugs and targeted therapy could offer an advantage to curing cancers. Here, we investigated the in vitro and in vivo antitumor activity of cisplatin, as a single-agent or in combination with palbociclib.

PATIENTS AND METHODS

The cell viability of Ntera-2/cl.D1 (NT2/D1) and 833K after exposure to palbociclib and/or cisplatin was evaluated by MTT dye reduction assay and by ATPLite Luminescence Assay. Gene and protein expression was evaluated by quantitative reverse transcription polymerase chain reaction and by western blot. Flow cytometric cell-cycle analysis was performed, as well. The in vivo experiments were conducted on NT2/D1 xenografts in AB zebrafish embryos exposed to the drugs.

RESULTS

Palbociclib and cisplatin decreased TGCT cell viability both in vitro and in vivo. This effect was additive when cells were exposed to the drug combination. In the NT2/D1 cell lines, the drug combination also exerted a positive effect with regard to delaying cell recovery after the toxic insult. In the combination experiments, cisplatin-induced cell accumulation in G2/M was predominant compared with the palbociclib effect.

CONCLUSIONS

These results could provide the rationale for developing further studies to improve the pharmacological treatment of TGCTs, but they must be demonstrated in a dedicated clinical trial.

4-Hydroxyhalcone effects on cisplatin-induced genotoxicity model

BACKGROUND

The genotoxicity of cisplatin (CP) as a platinum-based antineoplastic agent due to its oxidative stress induction was well known. In this research, we examined 4-hydroxychalcone (4-HCH) as a natural food that presents flavonoid effects on reactive oxygen species (ROS) production and CP-induced in vivo genotoxicity.

METHOD AND MATERIALS

Cytotoxicity of CP and 4-HCH was measured on human embryonic kidney 293 cells with MTT assay. Then, intracellular ROS content at IC50 concentration of CP was measured with 2',7'-dichlorofluorescein diacetate (DCFDA) dye. Finally, 4-HCH was administered intraperitoneally at 10 and 40 mg/kg/BW doses as a pre and post-treatment schedule in a mice model of CP genotoxicity (7 mg/kg). Acridine-orange-stained bone marrow cells were quantified for micronucleus presence examination.

RESULTS

The calculated IC50 of CP and 4-HCH were reported around 19.4 and 133.6 μM, respectively, on HEK293 cells. Also, it was observed that 4-HCH at 0.2, 2 and 10 μM concentrations did not show obvious cytotoxicity. The fluorimetry confirmed that pre-treatment with 10 μM and co-treatment with 2 μM of 4-HCH could attenuate the CP-induced ROS production (P < 0.05 and P < 0.01, respectively). Also, the lowest micronucleated cells were seen in 10 mg/kg 4-HCH-treated group after CP exposure (39 ± 7.9, P < 0.0001).

DISCUSSION

Our results demonstrated the antigenotoxic action of 4-HCH in CP-treated mice bone marrow cells for the first time in both concentrations of 10 and 40 mg/kg especially in the form of co-treatment. Further studies required clinical application of this compound in a combination of CP to attenuate the normal cells' genotoxicity side effects.

Targeting putative components of the mitochondrial permeability transition pore for novel therapeutics

Few discoveries have influenced drug discovery programs more than the finding that mitochondrial membranes undergo swings in permeability in response to cellular perturbations. The conductor of these permeability changes is the aptly named mitochondrial permeability transition pore which, although not yet precisely defined, is comprised of several integral proteins that differentially act to regulate the flux of ions, proteins and metabolic byproducts during the course of cellular physiological functions but also pathophysiological insults. Pursuit of the pore's exact identity remains a topic of keen interest, but decades of research have unearthed provocative functions for the integral proteins leading to their evaluation to develop novel therapeutics for a wide range of clinical indications. Chief amongst these targeted, integral proteins have been the Voltage Dependent Anion Channel (VDAC) and the F₁F_O ATP synthase. Research associated with the roles and ligands of VDAC has been extensive and we will expand upon 3 examples of ligand:VDAC interactions for consideration of drug discovery projects: Tubulin:VDAC1, Hexokinase I/II:VDAC1 and olesoxime:VDAC1. The discoveries that cyclosporine blocks mitochondrial permeability transition via binding to cyclophilin D, and that cyclophilin D is an important component of F₁F_O ATP synthase, has heightened interest in the F₁F_O ATP synthase as a focal point for drug discovery, and we will discuss 2 plausible campaigns associated with disease indications. To date no drug has emerged from prospective targeting these integral proteins; however, continued exploration such as the approaches suggested in this Commentary will increase the likelihood of providing important therapeutics for severely unmet medical needs.

Pathogenesis of platinum-induced peripheral neurotoxicity: Insights from preclinical studies

One of the most relevant dose-limiting adverse effects of platinum drugs is the development of a sensory peripheral neuropathy that highly impairs the patients' quality of life. Nowadays there are no available efficacy strategies for the treatment of platinum-induced peripheral neurotoxicity (PIPN), and the only way to prevent its development and progression is by reducing the dose of the cytostatic drug or even withdrawing the chemotherapy regimen. This clinical issue has been the main focus of hundreds of preclinical research works during recent decades. As a consequence, dozens of in vitro and in vivo models of PIPN have been developed to elucidate the molecular mechanisms involved in its development and to find neuroprotective targets. The apoptosis of peripheral neurons has been identified as the main mechanism involved in PIPN pathogenesis. This mechanism of DRG sensory neurons cell death is triggered by the nuclear and mitochondrial DNA platination together with the increase of the oxidative cellular status induced by the depletion of cytoplasmic antioxidant mechanisms. However, since there has been no successful transfer of preclinical results to clinical practise in terms of therapeutic approaches, some mechanisms of PIPN pathogenesis still remain to be elucidated. This review is focused on the pathogenic mechanisms underlying PIPN described up to now, provided by the critical analysis of in vitro and in vivo models.

DF2726A, a new IL-8 signalling inhibitor, is able to counteract chemotherapy-induced neuropathic pain

Chemotherapy-induced peripheral neuropathy (CIPN) is a common dose-limiting side effect of several anti-neoplastics and a main cause of sensory disturbances in cancer survivors, negatively impacting patients' quality of life. Peripheral nerve degeneration or small fibre neuropathy is generally accepted as the underlying mechanism in the development of CIPN. Recent evidence has contributed to clarify the determinant role of cytokines and chemokines in the process leading to neuronal hyperexcitability. Exposure to oxaliplatin triggers alterations in peripheral neuropathic pathways previously linked to IL-8 pathway. We investigated a novel selective inhibitor of IL-8 receptors, DF2726A, and showed its effects in counteracting CINP pathways, extending the relevance of the activation of IL-8 pathway to the class of platinum chemotherapeutics. Based on our results, we suggest that DF2726A might be a promising candidate for clinical treatment of CIPN conditions due to its efficacy and optimized pharmacokinetic/pharmacodynamic profile.

Fragmentation of kidney epithelial cell primary cilia occurs by cisplatin and these cilia fragments are excreted into the urine

The primary cilium, which protrudes from the cell surface, is associated with the pathogenesis of various diseases, including acute kidney injury (AKI). Primary cilium length dynamically changes during the progression of diseases. However, its relevance in disease and the underlying mechanism are largely unknown. In this study, we investigated the role of primary cilia in AKI induced by cisplatin, an effective anticancer drug, and the underlying mechanisms. In addition, we evaluated the usefulness of length alteration and deciliation of primary cilia into the urine for the diagnosis of AKI. Cisplatin induced shortening, elongation, and normalization of the primary cilia in kidney epithelial cells over time. During shortening, primary cilia fragments and ciliary proteins were excreted into the urine. During deciliation, cell proliferation and the expression of cyclin-dependent kinase inhibitor and proliferating cell nuclear antigen were not significantly changed. Shortening and deciliation of primary cilia were observed before significant increases in plasma creatinine and blood urea nitrogen concentration occurred. Pretreatment with Mito-Tempo, a mitochondria-targeted antioxidant, prevented cisplatin-induced primary cilium shortening and inhibited the increases in superoxide formation, lipid peroxidation, blood urea nitrogen, and tissue damage. In contrast, isocitrate dehydrogenase 2 (Idh2) gene deletion, which results in defect of the NADPH-associated mitochondrial antioxidant system, exacerbated cisplatin-induced changes in mice. Taken together, our findings demonstrate that cisplatin induces deciliation into the urine and antioxidant treatment prevents this deciliation, renal dysfunction, and tissue damage after cisplatin injection. These results suggest that cisplatin-induced AKI is associated with primary cilia and urine primary cilia proteins might be a non-invasive biomarker of kidney injury.

Quantitative Proteomic Profiling Reveals Key Pathways in the Anticancer Action of Methoxychalcone Derivatives in Triple Negative Breast Cancer

Triple negative breast cancer is an aggressive, heterogeneous disease with high recurrence and metastasis rates even with modern chemotherapy regimens and thus is in need of new therapeutics. Here, three novel synthetic analogues of chalcones, plant-based molecules that have demonstrated potency against a wide variety of cancers, were investigated as potential therapeutics for triple negative breast cancer. These compounds exhibit IC₅₀ values of ∼5 μM in triple negative breast cancer cell lines and are more potent against triple negative breast cancer cell lines than against nontumor breast cell lines according to viability experiments. Tandem mass tag-based quantitative proteomics followed by gene set enrichment analysis and validation experiments using flow cytometry, apoptosis, and Western blot assays revealed three different anticancer mechanisms for these compounds. First, the chalcone analogues induce the unfolded protein response followed by apoptosis. Second, increases in the abundances of MHC-I pathway proteins occurs, which would likely result in immune stimulation in an organism. And third, treatment with the chalcone analogues causes disruption of the cell cycle by interfering with microtubule structure and by inducing G1 phase arrest. These data demonstrate the potential of these novel chalcone derivatives as treatments for triple negative breast cancer, though further work evaluating their efficacy in vivo is needed.

Mitotic Exit Dysfunction through the Deregulation of APC/C Characterizes Cisplatin-Resistant State in Epithelial Ovarian Cancer

Purpose: Acquired resistance to cisplatin is a major barrier to success in treatment of various cancers, and understanding mitotic mechanisms unique to cisplatin-resistant cancer cells can provide the basis for developing novel mitotic targeted therapies aimed at eradicating these cells.Experimental Design: Using cisplatin-resistant models derived from primary patient epithelial ovarian cancer (EOC) cells, we have explored the status of mitotic exit mechanisms in cisplatin-resistant cells.Results: We have uncovered an unexpected role of long-term cisplatin treatment in inducing mitotic exit vulnerability characterized by increased spindle checkpoint activity and functional dependency on Polo-like kinase 1 (PLK1) for mitotic exit in the presence of anaphase promoting complex/cyclosome (APC/C) dysfunction in a cisplatin-resistant state. Accordingly, PLK1 inhibition decreased the survival of cisplatin-resistant cells in vitro and in vivo and exacerbated spindle checkpoint response in these cells. APC/CCDC20 inhibition increased sensitivity to pharmacologic PLK1 inhibition, further confirming the existence of APC/C dysfunction in cisplatin-resistant cells. In addition, we uncovered that resistance to volasertib, PLK1 inhibitor, is due to maintenance of cells with low PLK1 expression. Accordingly, stable PLK1 downregulation in cisplatin-resistant cells induced tolerance to volasertib.Conclusions: We provide the first evidence of APC/C dysfunction in cisplatin-resistant state, suggesting that understanding APC/C functions in cisplatin-resistant state could provide a basis for developing novel mitotic exit-based therapies to eradicate cisplatin-resistant cancer cells. Our results also show that PLK1 downregulation could underlie emergence of resistance to PLK1-targeted therapies in cancers. Clin Cancer Res; 24(18); 4588-601. ©2018 AACR.

An Emerging Role for Tubulin Isotypes in Modulating Cancer Biology and Chemotherapy Resistance

Tubulin proteins, as components of the microtubule cytoskeleton perform critical cellular functions throughout all phases of the cell cycle. Altered tubulin isotype composition of microtubules is emerging as a feature of aggressive and treatment refractory cancers. Emerging evidence highlighting a role for tubulin isotypes in differentially influencing microtubule behaviour and broader functional networks within cells is illuminating a complex role for tubulin isotypes regulating cancer biology and chemotherapy resistance. This review focuses on the role of different tubulin isotypes in microtubule dynamics as well as in oncogenic changes that provide a survival or proliferative advantage to cancer cells within the tumour microenvironment and during metastatic processes. Consideration of the role of tubulin isotypes beyond their structural function will be essential to improving the current clinical use of tubulin-targeted chemotherapy agents and informing the development of more effective cancer therapies.

Cisplatin, Oxaliplatin, and Kiteplatin Subcellular Effects Compared in a Plant Model

The immediate visual comparison of platinum chemotherapeutics’ effects in eukaryotic cells using accessible plant models of transgenic Arabidopsis thaliana is reported. The leading anticancer drug cisplatin, a third generation drug used for colon cancer, oxaliplatin and kiteplatin, promising Pt-based anticancer drugs effective against resistant lines, were administered to transgenic A. thaliana plants monitoring their effects on cells from different tissues. The transgenic plants’ cell cytoskeletons were labelled by the green fluorescent protein (GFP)-tagged microtubule-protein TUA6 (TUA6-GFP), while the vacuolar organization was evidenced by two soluble chimerical GFPs (GFPChi and AleuGFP) and one transmembrane GFP-tagged tonoplast intrinsic protein 1-1 (TIP1.1-GFP). The three drugs showed easily recognizable effects on plant subcellular organization, thereby providing evidence for a differentiated drug targeting. Genetically modified A. thaliana are confirmed as a possible rapid and low-cost screening tool for better understanding the mechanism of action of human anticancer drugs.

Nanoscale characterization illustrates the cisplatin-mediated biomechanical changes of B16-F10 melanoma cells

Cells reorganize their membrane biomechanical dynamics in response to environmental stimuli or inhibitors associated with their physiological/pathological processes, and disease therapeutics. To validate the biophysical dynamics during cell exposure to anti-cancer drugs, we investigate the nanoscale biological characterization in melanoma cells undergoing cisplatin treatment. Using atomic force microscopy, we demonstrate that the cellular morphology and membrane ultrastructure are altered after exposure to cisplatin. In contrast to their normal spindle-like shape, cisplatin causes cell deformation rendering cells flat and enlarged, which increases the cell area by 3-4 fold. Additionally, cisplatin decreases the topography height values for both the cytoplasmic and nuclear regions (by 40-80% and 60%, respectively). Furthermore, cisplatin increases the cytoplasmic root mean square roughness by 110-240% in correlation with the drug concentration and attenuates the nuclear RMS by 60%. Moreover, the cellular adhesion force was enhanced, while the Young's modulus elasticity was attenuated by ∼2 and ∼2.3 fold, respectively. F-actin phalloidin staining revealed that cisplatin enlarges the cell size through enhanced stress fiber formation and promotes cytoskeletal reorganization. Immunoblot analyses further revealed that the activities of focal adhesion proteins, such as FAK and c-Src, are upregulated by cisplatin through phosphorylation at tyrosine 397 and 530, respectively. Collectively, these results show that cisplatin-treated melanoma cells not only exhibit the upregulation of FAK-mediated signaling to enhance the cytoskeleton mechanical stretch, but also promote the cytoskeletal rearrangement resulting in 43% decrease in the cell modulus. These mechanisms thus promote the malignancy and invasiveness of the melanoma cells.

Biomarkers predicting chemotherapy response in head and neck squamous cell carcinoma: a review

BACKGROUND

Biomarkers are increasingly being used in many cancers to select patients for oncological treatment paradigms based on their inherent genetic properties. However, in head and neck cancers, there are no personalised therapies available outside the context of a clinical trial. A number of studies suggest there are intrinsic tumour properties of head and neck cancers that affect their response to chemotherapeutic agents. This paper aimed to review their evidence base.

METHOD

A narrative review was conducted following a search of the PubMed database.

RESULTS AND CONCLUSION

The review identified a number of biomarkers predicting response to chemotherapy in head and neck cancers. The paper discusses these in detail, and explores where future research could be directed in order to deliver personalised therapies for patients with head and neck cancers.

Overexpression of stathmin 1 confers an independent prognostic indicator in nasopharyngeal carcinoma

Data mining on public domain identified that stathmin 1 (STMN1) transcript was significantly higher expressed in nasopharyngeal carcinoma (NPC). Also known as the oncoprotein 18, STMN1 performs an important function in regulating rapid microtubule remodeling of the cytoskeleton in response to the cellular conditions. Immunoexpression of STMN1 was retrospectively assessed in biopsies of 124 consecutive NPC patients without initial distant metastasis and treated with consistent guidelines. The outcome was correlated with clinicopathological features and patient survivals. Results indicated that high STMN1 expressions (50 %) were correlated with advanced age (p = 0.027), higher T stage (p = 0.003), and overall clinical stage (p = 0.006) by the 7th American Joint Committee of Cancer Staging. In multivariate analyses, high STMN1 expression emerged as an independent prognosticator for worse disease-specific survival (p = 0.001), distal metastasis-free survival (p = 0.003), and local recurrence-free survival (p = 0.006). Exogenous expression of E2F transcription factor 1 (E2F1) or/and its dimeric partner, transcription factor Dp-1 (TFDP1), notably induced the STMN1 protein level in a NPC-derived cell line, TW01. Accordingly, high STMN1 protein level is commonly associated with adverse prognosticators and confers tumor aggressiveness in patients with NPC, and its upregulation might be attributed to E2F1 and/or TFDP1 transactivation.

Novel mixed ligand di-n-butyltin(IV) complexes derived from acylpyrazolones and fluorinated benzoic acids: synthesis, characterization, cytotoxicity and the induction of apoptosis in Hela cancer cells

Twenty one novel mixed ligand di-n-butyltin(IV) complexes [(n)Bu2SnAL] (A = substituted 4-acyl-5-pyrazolone, and L = fluorinated benzoic acid) were prepared by condensation of di-n-butyltin(IV) oxide with HL and HA in 1:1:1 molar ratio in refluxing methanol. All of the complexes were characterized by elemental analyses, IR, NMR ((1)H, (13)C, (119)Sn) and in four cases by X-ray diffraction. Cytotoxicity of the compounds was studied against two human cancer cell lines (KB and Hela) by means of the MTT assay compared to cisplatin, featuring IC₅₀ values in the low micromolar range. Hela cancer cell apoptosis-induced by 2 was examined by flow cytometry analysis, and preliminary results showed that 2 at concentrations of more than 1.0 μM can induce apoptosis.

Synergistic effects of cisplatin chemotherapy and gold nanorod-mediated hyperthermia on ovarian cancer cells and tumors

AIM

The synergistic effects of gold nanorod (GNR)-mediated mild hyperthermia (MHT; 42-43°C) and cisplatin (CP) activity was evaluated against chemoresistant SKOV3 cells in vitro and with a tumor xenograft model.

MATERIALS & METHODS

In vitro studies were performed using CP at cytostatic concentrations (5 µM) and polyethylene glycol-stabilized GNRs, using near-infrared laser excitation for MHT.

RESULTS

The amount of polyethylene glycol-GNRs used for environmental MHT was 1 µg/ml, several times lower than the loadings used in tumor tissue ablation. GNR-mediated MHT increased CP-mediated cytotoxicity by 80%, relative to the projected additive effect, and flow cytometry analysis suggested MHT also enhanced CP-induced apoptosis. In a pilot in vivo study, systemically administered polyethylene glycol-GNRs generated sufficient levels of MHT to enhance CP-induced reductions in tumor volume, despite their heterogeneous distribution in tumor tissue.

CONCLUSION

These studies imply that effective chemotherapies can be developed in combination with low loadings of nanoparticles for localized MHT. Original submitted 6 July 2013; Revised submitted 20 October 2013.

Comparative study of hematological responses to platinum group metals, antimony and silver nanoparticles in animal models

Research was conducted to examine the hematological effects of heavy metals (platinum (Pt ((IV))), palladium (Pd ((II))), rhodium (Rh ((III))), antimony (Sb ((III)) and Sb ((V))), and silver nanoparticles (AgNPs)) on white blood cells in mammalian (rat) and avian (chick embryo) models. These metals are used in many everyday products and are accumulating in our environment. Six-week old Sprague-Dawley female rats were treated daily by gavage and six-day old, fertile, specific pathogen-free white leghorn strain chick embryos' eggs were injected on days 7 and 14 of incubation with 0.0, 1.0, 5.0 or 10.0 ppm concentrations of Pt ((IV)) and a platinum group metal (PGM) mix of Pt ((IV)), Pd ((II)) and Rh ((III)). Chick embryos were also tested with 1.0 or 5.0 ppm of antimony compounds (Sb ((III)) and Sb ((V))) and 0.0, 15.0, 30.0, 60.0, or 100.0 ppm of silver nanoparticles (AgNPs). After 8 weeks of treatment, blood was obtained from the rats by jugular cut down and from chick embryos on day 20 of incubation by heart puncture. Blood smears were made and stained and a differential white cell count was performed on each. Examination of the smears revealed unconventional dose responses, stimulation of the immune response, and decreases in leukocyte production with various metals and concentrations. Chick embryos responded differently than rats to Pt and the PGM mix; suggesting that species differences and/or stage of development are important components of response to heavy metals. Route of administration of the metals might also influence the response. All of the heavy metals tested affected the immune responses of the tested animals as demonstrated by changes in the types and numbers of leukocytes. Our findings warrant further research to determine the mechanism of these effects and to understand and prevent toxicological effects in humans and other living organisms.

Evaluation of tubulin polymerization and chronic inhibition of proteasome as citotoxicity mechanisms in bortezomib-induced peripheral neuropathy

Bortezomib (BTZ) is the first proteasome inhibitor entered in clinical practice. Peripheral neuropathy is likely to be a class side effect of these drugs, although its severity is largely variable, and it deserves to be further investigated, since the mechanisms of BTZ-induced peripheral neurotoxicity (BiPN) are still unknown.   In our study, we investigated in vivo and in vitro possible pathogenic events relevant to BiPN using a well-established rat model, with particular reference to the extent of proteasome inhibition and the effects on α-tubulin polymerization in sciatic nerves and dorsal root ganglia specimens obtained from animals treated with chronic regimens at a dose of 0.2 mg/kg intravenously. The same assessments were also performed after a single injection. Moreover, these studies were replicated in vitro using embryonic DRG neurons exposed to 100 nM BTZ and adult DRG neurons exposed to 10-50 nM BTZ for 24 h and 48 h. A significant increase in the polymerized fraction of α-tubulin and prolonged proteasome inhibition were observed after the chronic BTZ treatment in vivo. Recovery to physiological levels was observed after a 4-week follow-up post-treatment period. Proteasome inhibition and increased α-tubulin polymerization were also observed following BTZ treatment of both embryonic and adult DRG neurons in vitro. Our in vivo results suggest that proteasome inhibition and alteration of tubulin dynamics contribute to BiPN. The in vitro systems here described reliably replicate the in vivo results, and might therefore be used for further mechanistic studies on the effects of proteasome inhibitors on neurons.

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.

A case of gastric adenocarcinoma with conspicuous binuclear cytologic features

Binuclear cells have been occasionally observed in nonneoplastic and carcinoma cells. However, in clinical cases, few reports have analyzed and discussed the origins and features, including the proliferative capacity, of binuclear cells. We describe the case of a 75-year-old man with gastric cancer with microscopically prominent binuclear cells in the resected tissue and ascitic fluid. Image cytometry and chromosomal analysis were performed on cells isolated from the ascitic fluid. The DNA histogram pattern showed aneuploidy and the fluorescence in situ hybridization pattern of centromeres 7 and 11 was similar to that of most other mononuclear cancer cells. Furthermore, the binuclear cells showed low proliferative capability based on 5-bromo-2'-deoxyuridine incorporation. Our results demonstrated that the binuclear cells were derived from mononuclear aneuploid cells through incomplete cell division, and, in this case, may have impaired proliferative capacity.

Cannabinoid type-1 receptor reduces pain and neurotoxicity produced by chemotherapy

Painful peripheral neuropathy is a dose-limiting complication of chemotherapy. Cisplatin produces a cumulative toxic effect on peripheral nerves, and 30-40% of cancer patients receiving this agent experience pain. By modeling cisplatin-induced hyperalgesia in mice with daily injections of cisplatin (1 mg/kg, i.p.) for 7 d, we investigated the anti-hyperalgesic effects of anandamide (AEA) and cyclohexylcarbamic acid 3'-carbamoyl-biphenyl-3-yl ester (URB597), an inhibitor of AEA hydrolysis. Cisplatin-induced mechanical and heat hyperalgesia were accompanied by a decrease in the level of AEA in plantar paw skin. No changes in motor activity were observed after seven injections of cisplatin. Intraplantar injection of AEA (10 μg/10 μl) or URB597 (9 μg/10 μl) transiently attenuated hyperalgesia through activation of peripheral CB₁ receptors. Co-injections of URB597 (0.3 mg/kg daily, i.p.) with cisplatin decreased and delayed the development of mechanical and heat hyperalgesia. The effect of URB597 was mediated by CB₁ receptors since AM281 (0.33 mg/kg daily, i.p.) blocked the effect of URB597. Co-injection of URB597 also normalized the cisplatin-induced decrease in conduction velocity of Aα/Aβ-fibers and reduced the increase of ATF-3 and TRPV1 immunoreactivity in dorsal root ganglion (DRG) neurons. Since DRGs are a primary site of toxicity by cisplatin, effects of cisplatin were studied on cultured DRG neurons. Incubation of DRG neurons with cisplatin (4 μg/ml) for 24 h decreased the total length of neurites. URB597 (100 nM) attenuated these changes through activation of CB₁ receptors. Collectively, these results suggest that pharmacological facilitation of AEA signaling is a promising strategy for attenuating cisplatin-associated sensory neuropathy.

Identification of cervical cancer proteins associated with treatment with paclitaxel and cisplatin in patients

OBJECTIVE

Neoadjuvant chemotherapy (NAC) with paclitaxel (T) and cisplatin (P) was commonly used for the treatment of cervical cancer. However, little is known about the antineoplastic mechanism of NAC with TP in patient tissues in situ. In this study, we compared the proteomic profiles of cervical cancer in patients before and after NAC with TP to identify proteins that may shed light on the mechanism of TP action.

METHODS

We collected cervical cancer tissues pre- and post-NAC with TP from 6 patients with local advanced cervical cancer and stored them at -80°C. Proteomes of 2 groups of cervical cancer tissues were analyzed by 2-dimensional gel electrophoresis and the differentially expressed proteins were identified by matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry. Some proteins that are differentially expressed were confirmed by Western blot.

RESULTS

There were 13 proteins whose levels were significantly altered after NAC with TP. Compared with pre-NAC, 11 proteins were down-regulated, and 2 proteins were up-regulated in the post-NAC group. The down-regulated proteins were aldolase A, pyruvate kinase, enolase 1, heat shock protein 27 (HSP27), HSP70, actinin α1, lamin B1, eukaryotic translation elongation factor 1γ, annexin 1, epithelial cell marker protein1, keratin II-type. In contrast, apolipoprotein A1 and annexin V were up-regulated. The down-regulation of HSP27, HSP70, enolase 1, and aldolase A was verified by Western blot.

CONCLUSIONS

Differentially expressed proteins between cervical cancer tissues pre- and post-NAC with TP were identified by comparative proteomic approach. The NAC therapy with TP down-regulated proteins involved in energy production (glycolytic enzymes) and chaperones but up-regulated proteins involved in apoptosis. These findings shed new light on biomarkers associated with effect of chemotherapy.

Multinuclear solid-state NMR of square-planar platinum complexes — Cisplatin and related systems

Multinuclear solid-state nuclear magnetic resonance (SSNMR) experiments have been performed on cisplatin and four related square-planar compounds. The wideband uniform rate smooth truncation – Carr–Purcell–Meiboom–Gill (WURST–CPMG) pulse sequence was utilized in NMR experiments to acquire 195Pt, 14N, and 35Cl ultra-wideline NMR spectra of high quality. Standard Hahn-echo and magic-angle spinning 195Pt NMR experiments are also performed to refine extracted chemical shielding (CS) tensor parameters. Platinum magnetic shielding (MS) tensor orientations are calculated using both plane-wave density functional theory (DFT) and standard DFT methods. The tensor orientations are shown to be highly constrained by molecular symmetry elements, but also influenced to some degree by intermolecular interactions. 14N WURST–CPMG experiments were performed on three compounds and electric field gradient (EFG) parameters (the quadrupolar coupling constant, CQ, and the asymmetry parameter, ηQ) are reported. First principles calculations of the 14N EFG tensor parameters and orientations and affirm their dependence on the local hydrogen bonding environment. 35Cl WURST–CPMG experiments on cisplatin and transplatin are reported, using two different static magnetic fields to extract EFG and CS tensor parameters, and 35Cl EFG tensor magnitudes and orientations are predicted using first principles calculations. Transverse (T2) relaxation data for all nuclei are used to investigate heteronuclear dipolar relaxation mechanisms, as well as the nature of the local hydrogen bonding environments.

Biologic activity of a dinuclear Pd(II)-spermine complex toward human breast cancer

A dinuclear palladium-based complex (Pd(2) -Spm) was synthesized and compared with cisplatin (cDDP) on two different human breast cancer cell lines (MCF-7 and MDA-MB-231) as well as toward an untransformed cell line (BJ fibroblasts). The results obtained show that Pd(2) -Spm is more effective against the estrogen receptors [ER(-)] cell line MDA-MB-231, while cDDP displayed better results for the ER(+) MCF-7 cell line. It was shown that, like cDDP, Pd(2) -Spm triggers phosphorylation of H2AX, indicating that this compound damages DNA. Apart from DNA, Pd(2) -Spm also targets the cytoskeleton having a greater impact on cell morphology than cDDP. Pd(2) -Spm and cDDP have opposite antiproliferative activities in the presence of the PI3K inhibitor wortmannin. Furthermore, Pd(2) -Spm at an optimized concentration displays a rapid antiproliferative effect as opposed to cDDP, which seems to have a slower kinetics. The results point to a distinct mechanism of action for each of these complexes, which may explain their synergistic action when coadministrated.

BNP7787-mediated modulation of paclitaxel- and cisplatin-induced aberrant microtubule protein polymerization in vitro

Taxane and platinum drugs are important agents in the treatment of cancer and have shown activity against a variety of tumors, including ovarian, breast, and lung cancer, either as single agents or in combination with other chemotherapy drugs. However, a serious and prevalent side effect of taxane (docetaxel and all formulations/derivatives of paclitaxel) and platinum (cisplatin, carboplatin, and oxaliplatin) agents is dose-limiting chemotherapy-induced peripheral neuropathy (CIPN). CIPN can result in treatment delays, dose modifications, and, in severe cases, discontinuation of chemotherapy. Consequently, effective treatments for CIPN are needed. Dimesna (BNP7787; Tavocept; disodium 2,2'-dithio-bis-ethanesulfonate) is an investigational drug that is undergoing international clinical development as a treatment that is coadministered with first-line taxane and platinum combination chemotherapy in patients with inoperable advanced primary adenocarcinoma of the lung. BNP7787 is currently being developed with the objective of increasing the survival of cancer patients receiving taxane- and/or cisplatin-based chemotherapy. Additional data indicate that BNP7787 may also protect against common and serious chemotherapy-induced toxicities, including chemotherapy-induced anemia, nausea, emesis, nephrotoxicity, and neuropathy, without interfering with antitumor activity of the chemotherapeutic agent(s). Studies herein show that BNP7787 prevents aberrant microtubule protein (MTP) polymerization that is caused by exposure of MTP to paclitaxel or cisplatin. BNP7787 modulates paclitaxel-induced hyperpolymerization of MTP in a dose-dependent manner, and mesna, an in vivo metabolite of BNP7787, protects against time-dependent cisplatin-induced inactivation of MTP. We propose that interactions between BNP7787 and MTP may play a role in BNP7787-mediated protection against CIPN.

Depression of MAD2 inhibits apoptosis and increases proliferation and multidrug resistance in gastric cancer cells by regulating the activation of phosphorylated survivin

Mitotic arrest-deficient 2 (MAD2) is one of the essential mitotic spindle checkpoint regulators, and it can protect cells from aberrant chromosome segregation. The Mad2 gene is very rarely mutated in many kinds of human cancer, but aberrantly reduced expression of MAD2 has been correlated with defective mitotic checkpoints in several human cancers. We have previously found that the MAD2 expression level is also shown to be associated with the multidrug resistance of tumour cells. In this study, we constructed a small interfering RNA (siRNA) eukaryotic expression vector of MAD2 and downregulated MAD2 expression in the gastric cancer cell line SGC7901 by transfection of MAD2-siRNA. SGC7901 cells stably transfected with the MAD2-siRNA exhibited significantly increased expression of phosphorylated survivin protein and enhanced drug resistance. Furthermore, MAD2-siRNA suppressed the proliferation of SGC7901 cells and inhibited tumour formation in athymic nude mice. This study clearly reveals that downregulation of MAD2 could regulate the cell cycle, increase proliferation, and improve the drug resistance of gastric cancer cells by regulating the activation of phosphorylated survivin. It also suggests both that MAD2 might play an important role in the development of human gastric cancer and that silencing the MAD2 gene may help to deal with the multidrug resistance of gastric cancer cells.

PACAP prevents toxicity induced by cisplatin in rat and primate neurons but not in proliferating ovary cells: involvement of the mitochondrial apoptotic pathway

Cisplatin is a chemotherapeutic agent whose use is limited by side effects including neuropathies. In proliferating cells, toxic action of cisplatin is based on DNA interactions, while, in quiescent cells, it can induce apoptosis by interacting with proteins. In the present study, we compared cytotoxic mechanisms activated by cisplatin in primate and rodent neurons and in ovary cells in order to determine whether the anti-apoptotic peptide PACAP could selectively reduce neurotoxicity. In quiescent neurons, JNK and sphingomyelinase inhibitors blocked cisplatin-induced cell death. Toxicity was associated with DNA laddering, caspase-3 and -9 activations and Bax induction. These effects were prevented by PACAP. In proliferating cells, cisplatin activated caspase-8 but had no effect on caspase-9. PACAP exerted no protective effect. These data indicate that cisplatin activates distinct apoptotic pathways in quiescent neurons and proliferating cells and that PACAP may reduce neurotoxicity of cisplatin without affecting its chemotherapeutic efficacy.

Effects of cell cycle inhibitors on tau phosphorylation in N2aTau3R cells

Neurofibrillary tangles are one of the pathologic hallmarks of Alzheimer's disease (AD). They are composed of paired helical filaments (PHF) containing hyperphosphorylated forms of tau. Hyperphosphorylation of certain tau sites favors its dissociation from the microtubules (MT), interfering with axonal transport and compromising the function and viability of neurons. Reappearance of cell cycle proteins have been reported in neurons exhibiting tau aggregation, suggesting that an aberrant cell cycle occurs before neurons die. Cell cycle suppression in neurons is crucial to survival, thus prevention of progression through the cell cycle may offer a therapeutic approach. Using a neuroblastoma cell line overexpressing 3-repeat (3R) tau, we investigated the effects of cell cycle inhibitors on tau phosphorylation. G2/M phase inhibitors did not alter phosphorylation of tau at Ser-202 and Ser-396/404 at the lower doses, but did at higher doses. Ser-202 and Ser-396/404 are phosphorylation sites of early and late neurofibrillary tangles, respectively, in AD. Cisplatin, a G1 phase inhibitor, did not phosphorylate tau. Cyclophosphamide and phosphoramide mustard, DNA cross-linking agents, decreased tau phosphorylation at Ser-396/404 site, but increased phosphorylation at Ser-202. These studies demonstrate that the G2/M blockers have a dose-dependent effect on tau phosphorylation. This seems to be a consequence of both the disruption of MT-organization and MT-dynamics when doses are higher, but only a disruption of MT-dynamics with lower doses. These results are also in agreement with the lack of phosphorylation seen for cisplatin, another inhibitor that produces disruption of the MT-dynamics.

Proteomic analysis of cisplatin-induced cochlear damage: Methods and early changes in protein expression

To identify early changes in protein expression associated with cisplatin ototoxicity, we used two dimensional-difference gel electrophoresis (2D-DIGE) and matrix-assisted laser desorption-time-of-flight (MALDI-TOF) mass spectrometry to analyze proteins from P3 rat cochleae that were cultured for 3h with or without 1mM cisplatin. Replicate analysis of fluorescent images from six gels revealed significant (p<0.01) cisplatin-induced changes (greater than 1.5-fold) in expression of 22 cochlear proteins. These include increases in the expression of five proteins, four of which were identified as nucleobindin 1, a nuclear calcium signaling and homeostasis protein (2.1-fold), heterogeneous nuclear ribonucleoprotein C, an RNA processing protein (1.8-fold), a 55 kDa protein that is either endothelial differentiation-related factor 1 or alpha-6 tubulin (1.7-fold), and calreticulin, a calcium binding chaperone of the endoplasmic reticulum (ER, 1.6-fold). The expression of 17 proteins was significantly (p<0.01) decreased by greater than 1.5-fold. These include ribonuclease/angiogenin inhibitor 1 (1.6-fold), RAS-like, family 12 (predicted), ras association (RalGDS/AF-6) domain family 5 (4.5-fold), homologous the RAS family of GTPase signaling proteins (2.4-fold), and Protein tyrosine phosphatase domain containing 1 (predicted, 6.1-fold). We identified seven cochlear proteins with either smaller (1.2-1.5-fold) or less significant (p<0.05) cisplatin-induced changes in expression. Notably, heat shock 70 kDa protein 5 (Hspa5, Grp78, and BiP), an ER chaperone protein involved in stress response, decreased 1.7-fold. We observed changes consistent with phosphorylation in the level of isoforms of another ER stress-induced protein, glucose-regulated protein Grp58. Changes in cisplatin-induced protein expression are discussed with respect to known or hypothesized functions of the identified proteins.

195Pt NMR--theory and application

This critical review highlights the progress in (195)Pt NMR over the last 25 years. In particular, some of the recent applications of (195)Pt NMR in catalytic and mechanistic studies, intermetallics and drug binding studies are discussed. (195)Pt NMR chemical shifts obtained from both theoretical studies and experiments are presented for Pt(0), Pt(II), Pt(III) and Pt(IV) complexes. (195)Pt coupling with various nuclei (viz. coupling constants) have also been collected in addition to data on (195)Pt relaxation. The latest developments in the theoretical knowledge and experimental advances have made (195)Pt NMR into a rich source of information in many fields. (164 references.).

Activation of tubulin assembly into microtubules upon a series of repeated femtosecond laser impulses

Tubulin, a globular protein, mostly distributed in nature in the dimeric alpha, beta form, can polymerize in vivo and in vitro into microtubules-longitudinal dynamic assemblies, involved in numerous cellular functions, including cell division and signaling. Tubulin polymerization starts upon binding Mg(2+) with the tubulin guanosine triphosphate (GTP) site. In the current study we show that a series of repeated femtosecond laser impulses activate the same site without adding Mg(2+). GTP site activation (without GTP no polymerization occurs) produces hydrated electrons (they are detected by the UV spectra), which are trapped in the shell of biological water, surrounding the tubulin. These electrons generate an additional, nonlinear by nature, polarization effect, responsible for the second harmonic generation at lambda=365 nm (the first harmonic is centered at lambda=730 nm) and manyfold increase in strength of the initial electric field. The results are supported by model calculations, based on the assumption of positive (negative) feedback, appearing on interaction of charge transfer exciton dipoles with the applied electromagnetic field.

Role of MEK/ERK pathway in the MAD2-mediated cisplatin sensitivity in testicular germ cell tumour cells

Testicular germ cell tumour (TGCT) is the most common malignancy in young males. Although most TGCTs are sensitive to cisplatin-based chemotherapy, significant numbers of TGCT patients still relapse and die each year because of the development of resistance to cisplatin. Previously, we first reported that a key regulator of the mitotic checkpoint, mitotic arrest deficient-2 (MAD2), was a mediator of cisplatin sensitivity in human cancer cells. In this study, we investigated whether MAD2 played a role in cellular sensitivity to cisplatin in TGCT cells and the underlying molecular mechanisms responsible. Using 10 TGCT cell lines, we found that increased MAD2 expression was correlated with cellular sensitivity to cisplatin, which was associated with activation of the MEK pathway. Treatment of cells expressing high levels of MAD2 with an MEK inhibitor, U0126, led to cellular protection against cisplatin-induced apoptosis. Inactivation of MAD2 by transfecting a dominant-negative construct in TGCT cells with high levels of MAD2 resulted in the suppression of MEK pathway and resistance to cisplatin-induced cell death. These results support previous suggestion on the involvement of mitotic checkpoint in DNA damage response in human cancer cells and demonstrate a possible molecular mechanism responsible for the MAD2-mediated sensitivity to cisplatin in TGCT cells. Our results also suggest that downregulation of MAD2 may be an indicator for identification of TGCT cancer cells that are potentially resistant to cisplatin-based therapy.

Diagnosis, management, and evaluation of chemotherapy-induced peripheral neuropathy

Peripheral neuropathy induced by cancer chemotherapy represents a large unmet need for patients due to the absence of treatment that can prevent or mitigate this common clinical problem. Chemotherapy-induced peripheral neuropathy (CIPN) diagnosis and management is further compounded by the lack of reliable and standardized means to diagnose and monitor patients who are at risk for, or who are symptomatic from, this complication of treatment. The pathogenesis and pathophysiology of CIPN are not fully elucidated, but there is increasing evidence of damage or interference with tubulin function. The diagnosis of CIPN may present a diagnostic dilemma due to the large number of potential toxic etiologies and conditions, which may mimic some of the clinical features; the diagnosis must be approached with care in such patients. The incidence and severity of CIPN is commonly under-reported by physicians as compared with patients. The development of new and reliable methods for the assessment of CIPN as well as safe and effective treatments to prevent this complication of treatment would represent important medical advancements for cancer patients.

Endocytic recycling compartments altered in cisplatin-resistant cancer cells

The clinical utility of cisplatin to treat human malignancies is often limited by the development of drug resistance. We have previously shown that cisplatin-resistant human KB adenocarcinoma cells that are cross-resistant to methotrexate and heavy metals have altered endocytic recycling. In this work, we tracked lipids in the endocytic recycling compartment (ERC) and found that the distribution of the ERC is altered in KB-CP.5 cells compared with parental KB-3-1 cells. A tightly clustered ERC is located near the nucleus in parental KB-3-1 cells but it appears loosely arranged and widely dispersed throughout the cytoplasm in KB-CP.5 cells. The altered distribution of the ERC in KB-CP.5 cells is related to the amount and distribution of stable detyrosinated microtubules (Glu-alpha-tubulin), as previously shown in Chinese hamster ovary B104-5 cells that carry a temperature-sensitive Glu-alpha-tubulin allele. In addition, B104-5 cells with a dispersed ERC under nonpermissive conditions were more resistant to cisplatin compared with B104-5 cells with a clustered ERC under permissive conditions. We conclude that resistance to cisplatin might be due, in part, to reduced uptake of cisplatin resulting from an endocytic defect reflecting defective formation of the ERC, possibly related to a shift in the relative amounts and distributions of stable microtubules.

Mitotic Arrest Deficient 2 Expression Induces Chemosensitization to a DNA-Damaging Agent, Cisplatin, in Nasopharyngeal Carcinoma Cells

Recently, mitotic arrest deficient 2 (MAD2)-mediated spindle checkpoint is shown to induce mitotic arrest in response to DNA damage, indicating overlapping roles of the spindle checkpoint and DNA damage checkpoint. In this study, we investigated if MAD2 played a part in cellular sensitivity to DNA-damaging agents, especially cisplatin, and whether it was regulated through mitotic checkpoint. Using nine nasopharyngeal carcinoma (NPC) cell lines, we found that decreased MAD2 expression was correlated with cellular resistance to cisplatin compared with the cell lines with high levels of MAD2. Exogenous MAD2 expression in NPC cells also conferred sensitivity to DNA-damaging agents especially cisplatin but not other anticancer drugs with different mechanisms of action. The increased cisplatin sensitivity in MAD2 transfectants was associated with mitotic arrest and activation of apoptosis pathway evidenced by the increased mitotic index and apoptosis rate as well as decreased Bcl-2 and Bax ratio and expression of cleaved poly(ADP-ribose) polymerase and caspase 3. Our results indicate that the MAD2-induced chemosensitization to cisplatin in NPC cells is mediated through the induction of mitotic arrest, which in turn activates the apoptosis pathway. Our evidence further confirms the previous hypothesis that spindle checkpoint plays an important part in DNA damage-induced cell cycle arrest and suggests a novel role of MAD2 in cellular sensitivity to cisplatin.