Proliferation, migration and invasion of human glioma cells exposed to paclitaxel (Taxol) in vitro

Adjuvant convection-enhanced delivery for the treatment of brain tumors

BACKGROUND

Malignant gliomas are a therapeutic challenge and remain nearly uniformly fatal. While new targeted chemotherapeutic agentsagainst malignant glioma have been developed in vitro, these putative therapeutics have not been translated into successful clinical treatments. The lack of clinical effectiveness can be the result of ineffective biologic strategies, heterogeneous tumor targets and/or the result of poortherapeutic distribution to malignant glioma cells using conventional nervous system delivery modalities (intravascular, cerebrospinal fluid and/orpolymer implantation), and/or ineffective biologic strategies.

METHODS

The authors performed a review of the literature for the terms "convection enhanced delivery", "glioblastoma", and "glioma". Selectclinical trials were summarized based on their various biological mechanisms and technological innovation, focusing on more recently publisheddata when possible.

RESULTS

We describe the properties, features and landmark clinical trials associated with convection-enhanced delivery for malignant gliomas.We also discuss future trends that will be vital to CED innovation and improvement.

CONCLUSION

Efficacy of CED for malignant glioma to date has been mixed, but improvements in technology and therapeutic agents arepromising.

Inference of glioblastoma migration and proliferation rates using single time-point images

Cancer cell migration is a driving mechanism of invasion in solid malignant tumors. Anti-migratory treatments provide an alternative approach for managing disease progression. However, we currently lack scalable screening methods for identifying novel anti-migratory drugs. To this end, we develop a method that can estimate cell motility from single end-point images in vitro by estimating differences in the spatial distribution of cells and inferring proliferation and diffusion parameters using agent-based modeling and approximate Bayesian computation. To test the power of our method, we use it to investigate drug responses in a collection of 41 patient-derived glioblastoma cell cultures, identifying migration-associated pathways and drugs with potent anti-migratory effects. We validate our method and result in both in silico and in vitro using time-lapse imaging. Our proposed method applies to standard drug screen experiments, with no change needed, and emerges as a scalable approach to screen for anti-migratory drugs.

Pediatric high-grade glioma: moving toward subtype-specific multimodal therapy

Pediatric high-grade gliomas (pHGG) comprise a deadly, heterogenous category of pediatric gliomas with a clear need for more effective treatment options. Advances in high-throughput molecular techniques have enhanced molecular understanding of these tumors, but outcomes are still poor, and treatments beyond resection and radiation have not yet been clearly established as standard of care. In this review, we first discuss the history of treatment approaches to pHGG to this point. We then review four distinct categories of pHGG, including histone 3-mutant, IDH-mutant, histone 3/IDH-wildtype, and radiation-induced pHGG. We discuss the molecular understanding of each subgroup and targeted treatment options in development. Finally, we look at the development and current status of two novel approaches to pHGG as a whole: localized convection-enhanced chemotherapy delivery and immunotherapy, including checkpoint inhibitors, vaccine therapy, and CAR-T cells. Through this review, we demonstrate the potential for rational, molecularly driven, subtype-specific therapy to be used with other novel approaches in combinations that could meaningfully improve the prognosis in pHGG.

ATP-binding cassette transporters restrict drug delivery and efficacy against brain tumors even when blood-brain barrier integrity is lost

The impact of a compromised blood-brain barrier (BBB) on the drug treatment of intracranial tumors remains controversial. We characterize the BBB integrity in several intracranial tumor models using magnetic resonance imaging, fluorescent dyes, and autoradiography and determine the distribution and efficacy of docetaxel in brain tumors grafted in Abcb1-proficient and Abcb1-deficient mice. Leakiness of the tumor vasculature varies from extensive to absent. Regardless of the extent of leakiness, tumor blood vessels express ATP-binding cassette transporters (Abcb1 and Abcg2). A leaky vasculature results in higher docetaxel tumor levels compared to normal brain. Nevertheless, Abcb1 can reduce drug distribution and efficacy even in leaky models. Thus, BBB leakiness does not ensure the unimpeded access of ATP-binding cassette transporter substrate drugs. Therapeutic responses may be observed, but the full potential of such therapeutics may still be attenuated. Consequently, BBB-penetrable drugs with little to no affinity for efflux transporters are preferred for the treatment of intracranial tumors.

Blood-brain barrier integrity in brain tumor models varies from intact to absent

Brain tumor vessels express drug efflux transporters

Drug transporters can impede drug entry and efficacy, even in leaky tumors

Low-affinity ABC transporter drugs are favored candidates for treating brain tumors

Trace of survivin in cancer

Survivin is one of the most cancer-specific proteins overexpressed in almost all malignancies, but is nearly undetectable in most normal tissues in adults. Functionally, as a member of the inhibitor of apoptosis family, survivin has been shown to inhibit apoptosis and increase proliferation. The antiapoptotic function of survivin seems to be related to its ability to inhibit caspases directly or indirectly. Furthermore, the role of survivin in cell cycle division control is related to its role in the chromosomal passenger complex. Consistent with its determining role in these processes, survivin plays a crucial role in cancer progression and cancer cell resistance to anticancer drugs and ionizing radiation. On the basis of these findings, recently survivin has been investigated intensively as an ideal tumor biomarker. Thus, multiple molecular approaches such as use of the RNA interfering technique, antisense oligonucleotides, ribozyme, and small molecule inhibitors have been used to downregulate survivin regulation and inhibit its biological function consequently. In this review, all these approaches are explained and other compounds that induced apoptosis in different cell lines through survivin inhibition are also reported.

The Role of C-X-C Chemokine Receptor Type 4 (CXCR4) in Cell Adherence and Spheroid Formation of Human Ewing's Sarcoma Cells under Simulated Microgravity

We studied the behavior of Ewing's Sarcoma cells of the line A673 under simulated microgravity (s-µg). These cells express two prominent markers-the oncogene EWS/FLI1 and the chemokine receptor CXCR4, which is used as a target of treatment in several types of cancer. The cells were exposed to s-µg in a random-positioning machine (RPM) for 24 h in the absence and presence of the CXCR4 inhibitor AMD3100. Then, their morphology and cytoskeleton were examined. The expression of selected mutually interacting genes was measured by qRT-PCR and protein accumulation was determined by western blotting. After 24 h incubation on the RPM, a splitting of the A673 cell population in adherent and spheroid cells was observed. Compared to 1 g control cells, EWS/FLI1 was significantly upregulated in the adherent cells and in the spheroids, while CXCR4 and CD44 expression were significantly enhanced in spheroids only. Transcription of CAV-1 was upregulated and DKK2 and VEGF-A were down-regulated in both, adherent in spheroid cells, respectively. Regarding, protein accumulation EWS/FLI1 was enhanced in adherent cells only, but CD44 decreased in spheroids and adherent cells. Inhibition of CXCR4 did not change spheroid count, or structure. Under s-µg, the tumor marker EWS/FLI1 is intensified, while targeting CXCR4, which influences adhesion proteins, did not affect spheroid formation.

Investigation of Effective Parameters on Size of Paclitaxel Loaded PLGA Nanoparticles

Purpose: The size of polymeric nanoparticles is considered as an effective factor in cancer therapy due to enterance into tumor tissue via the EPR effect. The purpose of this work was to investigate the effective parameters on poly(lactic-co-glycolic acid)-paclitaxel (PLGA –PTX) nanoparticles size.

Methods: We prepared PLGA-PTX nanoparticles via single emulsion and precipitation methods with variable paremeters including drug concentration, aqueous to organic phase volume ratio, polymer concentration, sonication time and PVA concentration.

Results: PLGA-PTX nanoparticles were characterized by dynamic light scattering (DLS) and scanning electron microscopy (SEM). The results exhibited that the diameter of nanoparticles enhanced with increasing drug, polymer and PVA concentrations whereas organic to aqueous phase volume ratio and sonication time required to the optimization for a given size.

Conclusion: The precipitation method provides smaller nanoparticles compared to emulsion one. Variable parameters including drug concentration, aqueous to organic phase volume ratio, polymer concentration, sonication time and PVA concentration affect diameter of nanoparticles.

Linking invasive motility to protein expression in single tumor cells

The invasion of malignant cells into tissue is a critical step in the progression of cancer. While it is increasingly appreciated that cells within a tumor differ in their invasive potential, it remains nearly unknown how these differences relate to cell-to-cell variations in protein expression. Here, we introduce a microfluidic platform that integrates measurements of invasive motility and protein expression for single cells, which we use to scrutinize human glioblastoma tumor-initiating cells (TICs). Our live-cell imaging microdevice is comprised of polyacrylamide microchannels that exhibit tissue-like stiffness and present chemokine gradients along each channel. Due to intrinsic differences in motility, cell subpopulations separate along the channel axis. The separated cells are then lysed in situ and each single-cell lysate is subjected to western blotting in the surrounding polyacrylamide matrix. We observe correlations between motility and Nestin and EphA2 expression. We identify protein-protein correlations within single TICs, which would be obscured with population-based assays. The integration of motility traits with single-cell protein analysis - on the same cell - offers a new means to identify druggable targets of invasive capacity.

Regulation of E-cadherin localization by microtubule targeting agents: rapid promotion of cortical E-cadherin through p130Cas/Src inhibition by eribulin

Microtubule targeting agents (MTAs) are some of the most effective anticancer drugs used to treat a wide variety of adult and pediatric cancers. Building evidence suggests that these drugs inhibit interphase signaling events and that this contributes to their anticancer actions. The effects of diverse MTAs were evaluated following a 2 hour incubation with clinically relevant concentrations to test the hypothesis that these drugs rapidly and differentially disrupt epithelial-to-mesenchymal transition (EMT)-related signaling. The MTAs rapidly promoted the cortical localization of internal pools of E-cadherin in HCC1937 breast cancer cells, with the most robust effects observed with the microtubule destabilizers eribulin and vinorelbine. Cortical E-cadherin localization was also promoted by the Src kinase inhibitor dasatinib or by siRNA-mediated depletion of the p130Cas scaffold. Mechanistic studies demonstrate that eribulin disrupts the interaction between p130Cas and Src, leading to decreased cortical Src phosphorylation that precedes the accumulation of cortical E-cadherin. These results suggest that microtubules can be actively co-opted by cancer cells to inhibit cortical E-cadherin localization, a hallmark of EMT, and provide a direct link between the initial disruption of the microtubule network and reversal of EMT phenotypes demonstrated by eribulin in long-term studies.

A confidence building exercise in data and identifiability: Modeling cancer chemotherapy as a case study

Mathematical modeling has a long history in the field of cancer therapeutics, and there is increasing recognition that it can help uncover the mechanisms that underlie tumor response to treatment. However, making quantitative predictions with such models often requires parameter estimation from data, raising questions of parameter identifiability and estimability. Even in the case of structural (theoretical) identifiability, imperfect data and the resulting practical unidentifiability of model parameters can make it difficult to infer the desired information, and in some cases, to yield biologically correct inferences and predictions. Here, we examine parameter identifiability and estimability using a case study of two compartmental, ordinary differential equation models of cancer treatment with drugs that are cell cycle-specific (taxol) as well as non-specific (oxaliplatin). We proceed through model building, structural identifiability analysis, parameter estimation, practical identifiability analysis and its biological implications, as well as alternative data collection protocols and experimental designs that render the model identifiable. We use the differential algebra/input-output relationship approach for structural identifiability, and primarily the profile likelihood approach for practical identifiability. Despite the models being structurally identifiable, we show that without consideration of practical identifiability, incorrect cell cycle distributions can be inferred, that would result in suboptimal therapeutic choices. We illustrate the usefulness of estimating practically identifiable combinations (in addition to the more typically considered structurally identifiable combinations) in generating biologically meaningful insights. We also use simulated data to evaluate how the practical identifiability of the model would change under alternative experimental designs. These results highlight the importance of understanding the underlying mechanisms rather than purely using parsimony or information criteria/goodness-of-fit to decide model selection questions. The overall roadmap for identifiability testing laid out here can be used to help provide mechanistic insight into complex biological phenomena, reduce experimental costs, and optimize model-driven experimentation.

Convection-Enhanced Delivery

Convection-enhanced delivery (CED) is a promising technique that generates a pressure gradient at the tip of an infusion catheter to deliver therapeutics directly through the interstitial spaces of the central nervous system. It addresses and offers solutions to many limitations of conventional techniques, allowing for delivery past the blood-brain barrier in a targeted and safe manner that can achieve therapeutic drug concentrations. CED is a broadly applicable technique that can be used to deliver a variety of therapeutic compounds for a diversity of diseases, including malignant gliomas, Parkinson's disease, and Alzheimer's disease. While a number of technological advances have been made since its development in the early 1990s, clinical trials with CED have been largely unsuccessful, and have illuminated a number of parameters that still need to be addressed for successful clinical application. This review addresses the physical principles behind CED, limitations in the technique, as well as means to overcome these limitations, clinical trials that have been performed, and future developments.

In vitro models of medulloblastoma: Choosing the right tool for the job

The recently-defined four molecular subgroups of medulloblastoma have required updating of our understanding of in vitro models to include molecular classification and risk stratification features from clinical practice. This review seeks to build a more comprehensive picture of the in vitro systems available for modelling medulloblastoma. The subtype classification and molecular characterisation for over 40 medulloblastoma cell-lines has been compiled, making it possible to identify the strengths and weaknesses in current model systems. Less than half (18/44) of established medulloblastoma cell-lines have been subgrouped. The majority of the subgrouped cell-lines (11/18) are Group 3 with MYC-amplification. SHH cell-lines are the next most common (4/18), half of which exhibit TP53 mutation. WNT and Group 4 subgroups, accounting for 50% of patients, remain underrepresented with 1 and 2 cell-lines respectively. In vitro modelling relies not only on incorporating appropriate tumour cells, but also on using systems with the relevant tissue architecture and phenotype as well as normal tissues. Novel ways of improving the clinical relevance of in vitro models are reviewed, focusing on 3D cell culture, extracellular matrix, co-cultures with normal cells and organotypic slices. This paper champions the establishment of a collaborative online-database and linked cell-bank to catalyse preclinical medulloblastoma research.

Convection-Enhanced and Local Delivery of Targeted Cytotoxins in the Treatment of Malignant Gliomas

Despite advances in our knowledge about the genesis, molecular biology, and natural history of malignant gliomas and the use of a multi-disciplinary approach to their treatment, patients harboring this diagnosis continue to face a grim prognosis. At the time of diagnosis, patients typically undergo surgery for the establishment of a histologic diagnosis, the reduction of tumor burden, and the relief of mass effect, with the maintenance of the patient's neurological function in mind. This is followed by the administration of adjuvant therapeutics, including radiation therapy and chemotherapy.

Many investigational agents with laboratory evidence of efficacy against malignant gliomas have not met their promise in the clinical setting, largely due to the barriers that they must overcome to reach the tumor at a therapeutically meaningful concentration for a durable period of time. The relevant aspects of the blood-brain barrier, blood-tumor barrier, and blood-cerebrospinal fluid barrier, as they pertain to the delivery of agents to the tumor, will be discussed along with the strategies devised to circumvent them. This discussion will be followed by a description of agents currently in preclinical and clinical development, many of which are the result of intense ongoing research into the molecular biology of gliomas.

Overexpression of the 14-3-3gamma protein in embryonic mice results in neuronal migration delay in the developing cerebral cortex

The 14-3-3 protein family is a group of multifunctional proteins that are highly expressed in the brain; however, their functions in brain development are largely unknown. Williams Syndrome is a neurodevelopmental disorder caused by a deletion in the 7q11.23 chromosome locus, including the gene encoding 14-3-3gamma, resulting in developmental delay, intellectual disabilities and epilepsy. We have previously shown that knocking down the 14-3-3gamma protein in utero in mice results in delays in neuronal migration of pyramidal neurons in the cortex. Importantly, there is a reciprocal duplication syndrome to Williams Syndrome where the 7q11.23 locus is duplicated, resulting in epilepsy and intellectual disabilities. Thus, the deletion or the duplication of the 7q11.23 chromosome locus results in epilepsy. Taken together with the fact that defects in neuronal migration are one of main causes for epilepsy, we analyzed if the overexpression of 14-3-3gamma causes neuronal migration defects. In this work, we found that the overexpression of 14-3-3gamma in utero in the developing mouse cortex results in delays in pyramidal neuron migration, similar to what was previously observed when 14-3-3gamma was knocked down. These results, in conjunction with our previous research, indicate that a balance of 14-3-3gamma expression is required during cortical development to prevent delays in neuronal migration. This work provides clear evidence as to the involvement of 14-3-3gamma in neurodevelopmental disorders and how a disruption in 14-3-3gamma expression may contribute to the neurodevelopmental disorders that manifest when the 7q11.23 locus is altered.

High-Throughput 3D Tumor Spheroid Screening Method for Cancer Drug Discovery Using Celigo Image Cytometry

Oncologists have investigated the effect of protein or chemical-based compounds on cancer cells to identify potential drug candidates. Traditionally, the growth inhibitory and cytotoxic effects of the drugs are first measured in 2D in vitro models, and then further tested in 3D xenograft in vivo models. Although the drug candidates can demonstrate promising inhibitory or cytotoxicity results in a 2D environment, similar effects may not be observed under a 3D environment. In this work, we developed an image-based high-throughput screening method for 3D tumor spheroids using the Celigo image cytometer. First, optimal seeding density for tumor spheroid formation was determined by investigating the cell seeding density of U87MG, a human glioblastoma cell line. Next, the dose-response effects of 17-AAG with respect to spheroid size and viability were measured to determine the IC₅₀ value. Finally, the developed high-throughput method was used to measure the dose response of four drugs (17-AAG, paclitaxel, TMZ, and doxorubicin) with respect to the spheroid size and viability. Each experiment was performed simultaneously in the 2D model for comparison. This detection method allowed for a more efficient process to identify highly qualified drug candidates, which may reduce the overall time required to bring a drug to clinical trial.

In vitro co-culture model of medulloblastoma and human neural stem cells for drug delivery assessment

Physiologically relevant in vitro models can serve as biological analytical platforms for testing novel treatments and drug delivery systems. We describe the first steps in the development of a 3D human brain tumour co-culture model that includes the interplay between normal and tumour tissue along with nutrient gradients, cell-cell and cell-matrix interactions. The human medulloblastoma cell line UW228-3 and human foetal brain tissue were marked with two supravital fluorescent dyes (CDCFDASE, Celltrace Violet) and cultured together in ultra-low attachment 96-well plates to form reproducible single co-culture spheroids (d = 600 μm, CV% = 10%). Spheroids were treated with model cytotoxic drug etoposide (0.3-100 μM) and the viability of normal and tumour tissue quantified separately using flow cytometry and multiphoton microscopy. Etoposide levels of 10 μM were found to maximise toxicity to tumours (6.5% viability) while stem cells maintained a surviving fraction of 40%. The flexible cell marking procedure and high-throughput compatible protocol make this platform highly transferable to other cell types, primary tissues and personalised screening programs. The model's key anticipated use is for screening and assessment of drug delivery strategies to target brain tumours, and is ready for further developments, e.g. differentiation of stem cells to a range of cell types and more extensive biological validation.

The Role of Chemotherapy in the Treatment of Malignant Astrocytomas

Malignant astrocytomas are aggressive neoplasms with a dismal prognosis despite optimal treatment. Maximal resective surgery is traditionally complemented by radiation therapy. Chemotherapy is now used on patients as initial therapy when their functional status is congruent with further treatment. The classic agents used are nitrosoureas, but temozolomide has taken the front seat recently, with recent data demonstrating increased survival when this agent is used concurrently with radiation therapy in newly diagnosed glioblastoma patients. A new class of agents, refered to as biological modifiers, are increasingly used in clinical trials in an effort to affect the intrinsic biologic aberrations harboured by tumor cells. These drugs comprise differentiation agents, anti-angiogenic agents, matrix-metalloproteinase inhibitors and signal transduction inhibitors, among others. This article reviews the standard cytotoxic agents that have been used to treat malignant astrocytomas, and the different combination regimens offering promise. In addition, recent advances with biological modifiers are also discussed.

Identifying new small molecule anti-invasive compounds for glioma treatment

Glioblastoma is a disease with poor survival rates after diagnosis. Treatment of the disease involves debulking of the tumor, which is limited by the degree of invasiveness of the disease. Therefore, a treatment to halt the invasion of glioma is desirable for clinical implementation. There have been several candidate compounds targeting specific aspects of invasion, including cell adhesions, matrix degradation, and cytoskeletal rearrangement, but they have failed clinically for a variety of reasons. New targets against glioma invasion include upstream mediators of these classical targets in an effort to better inhibit invasion with more specificity for cancer. Included in these treatments is a new class of compounds inhibiting the generation of reactive oxygen species by targeting the NADPH oxidases. These compounds stand to inhibit multiple pathways, including nuclear factor kappa B and Akt. By conducting a screen of compounds thought to inhibit these pathways, a new compound to halt invasion was found that may have a beneficial effect against glioma, based on recent publications. Further, there are still limitations to the treatment of glioblastoma regardless of the discovery of new targets and compounds that should be addressed to better the therapies against this deadly cancer.

Development of a high-throughput three-dimensional invasion assay for anti-cancer drug discovery

The lack of three-dimensional (3-D) high-throughput (HT) screening assays designed to identify anti-cancer invasion drugs is a major hurdle in reducing cancer-related mortality, with the key challenge being assay standardization. Presented is the development of a novel 3-D invasion assay with HT potential that involves surrounding cell-collagen spheres within collagen to create a 3-D environment through which cells can invade. Standardization was achieved by designing a tooled 96-well plate to create a precisely designated location for the cell-collagen spheres and by using dialdehyde dextran to inhibit collagen contraction, maintaining uniform size and shape. This permits automated readout for determination of the effect of inhibitory compounds on cancer cell invasion. Sensitivity was demonstrated by the ability to distinguish varying levels of invasiveness of cancer cell lines, and robustness was determined by calculating the Z-factor. A Z-factor of 0.65 was obtained by comparing the effects of DMSO and anti-β1-integrin antibody, an inhibitory reagent, on the invasion of Du145 cancer cells, suggesting this novel assay is suitable for large scale drug discovery. As proof of principle, the NCI Diversity Compound Library was screened against human invasive cancer cells. Nine compounds exhibiting high potency and low toxicity were identified, including DX-52-1, a compound previously reported to inhibit cell migration, a critical determinant of cancer invasion. The results indicate that this innovative HT platform is a simple, precise, and easy to replicate 3-D invasion assay for anti-cancer drug discovery.

Different regulatory pathways are involved in the proliferative inhibition of two types of leukemia cell lines induced by paclitaxel

Paclitaxel, one of the broadest-spectrum anticancer agents, is currently being used in the treatment of patients with solid tumors. In the present study, we compared the effect of paclitaxel on two types of leukemia cells. Our results showed that paclitaxel could inhibit the proliferation of MEL and K562 cells in a dose- and time-dependent manner. The mechanism of proliferative inhibition in K562 cells treated by paclitaxel was related to the cell cycle arrest in the G2/M phase, as well as the induction of apoptosis. By contrast, MEL cells treated by paclitaxel showed significant characteristics of necrosis, which indicated that the mode of cell death induced by paclitaxel in these two types of leukemia cells differed. Advances in research of the cell cycle, apoptosis and necrosis will extend our understanding of the mechanisms of paclitaxel-induced cell death, particularly in leukemia cells. Further elucidation of the mechanisms of necrosis in MEL cells may expedite the development of improved paclitaxel-based regimens for cancer therapy.

Beyond taxol: microtubule-based treatment of disease and injury of the nervous system

Contemporary research has revealed a great deal of information on the behaviours of microtubules that underlie critical events in the lives of neurons. Microtubules in the neuron undergo dynamic assembly and disassembly, bundling and splaying, severing, and rapid transport as well as integration with other cytoskeletal elements such as actin filaments. These various behaviours are regulated by signalling pathways that affect microtubule-related proteins such as molecular motor proteins and microtubule severing enzymes, as well as a variety of proteins that promote the assembly, stabilization and bundling of microtubules. In recent years, translational neuroscientists have earmarked microtubules as a promising target for therapy of injury and disease of the nervous system. Proof-of-principle has come mainly from studies using taxol and related drugs to pharmacologically stabilize microtubules in animal models of nerve injury and disease. However, concerns persist that the negative consequences of abnormal microtubule stabilization may outweigh the positive effects. Other potential approaches include microtubule-active drugs with somewhat different properties, but also expanding the therapeutic toolkit to include intervention at the level of microtubule regulatory proteins.

Integration of cancer gene co-expression network and metabolic network to uncover potential cancer drug targets

Cell metabolism is critical for cancer cell transformation and progression. In this study, we have developed a novel method, named Met-express, that integrates a cancer gene co-expression network with the metabolic network to predict key enzyme-coding genes and metabolites in cancer cell metabolism. Met-express successfully identified a group of key enzyme-coding genes and metabolites in lung, leukemia, and breast cancers. Literature reviews suggest that approximately 33-53% of the predicted genes are either known or suggested anti-cancer drug targets, while 22% of the predicted metabolites are known or high-potential drug compounds in therapeutic use. Furthermore, experimental validations prove that 90% of the selected genes and 70% of metabolites demonstrate the significant anti-cancer phenotypes in cancer cells, implying that they may play important roles in cancer metabolism. Therefore, Met-express is a powerful tool for uncovering novel therapeutic biomarkers.

A tubulin binding peptide targets glioma cells disrupting their microtubules, blocking migration, and inducing apoptosis

Despite aggressive treatment regimes, glioma remains a largely fatal disease. Current treatment limitations are attributed to the precarious locations within the brain where such tumors grow, their highly infiltrative nature precluding complete resection and lack of specificity among agents capable of attenuating their growth. Here, we show that in vitro, glioma cells of diverse origins internalize a peptide encompassing a tubulin-binding site (TBS) on the neurofilament light protein. The internalized peptide disrupts the microtubule network, inhibits migration and proliferation, and leads to apoptosis. Using an intracerebral transplant model, we show that most, if not all, of these responses to peptide exposure also occur in vivo. Notably, a single intratumor injection significantly attenuates tumor growth, while neither peptide uptake nor downstream consequences are observed elsewhere in the host nervous system. Such preferential uptake suggests that the peptide may have potential as a primary or supplementary glioblastoma treatment modality by exploiting its autonomous microtubule-disrupting activity or engaging its capacity to selectively target glioma cells with other cell-disrupting cargos.

Docetaxel suppresses invasiveness of head and neck cancer cells in vitro

The combination of docetaxel, cisplatin, and fluorouracil significantly enhances the survival of head and neck cancer patients compared to cisplatin and fluorouracil. We hypothesized that docetaxel may affect invasiveness of the head and neck cancer cells in addition to its tumor-killing effect. Two different head and neck cancer cell lines (HEp-2 and Ca9-22) were treated with docetaxel at IC(10) and IC(50) concentrations. Cell migration and invasive growth was evaluated by wound healing assay and three-dimensional (3D) culture of multicellular tumor spheroids, respectively. Expression levels of possible downstream effectors for cell migration/invasiveness were measured by immunoblotting in conditions with or without docetaxel. Docetaxel, but not cisplatin, suppressed filopodia formation compared with no treatment (control) condition. Consistent with this, docetaxel suppressed two-dimensional (2D) cell migration and 3D cell invasion compared with control or cisplatin. Only docetaxel treated cells exhibited thick tubulin bundle and had lower activity of Cdc42, a member of the Rho family of small GTPases. In conclusion, Docetaxel treatment suppressed migration and invasiveness of head and neck cancer cells in vitro, which is likely to be mediated by regulating Cdc42 activity.

Organotypic glioma spheroids for screening of experimental therapies: how many spheroids and sections are required?

Cancer spheroids are a valuable model for screening anticancer strategies. However, studies are published using various numbers of spheroids and sections per spheroid. Here, we establish the sample size requirements for valid screening strategies to treat glioma: how many spheroids per experimental group and how many sections per spheroid are required to detect one-third reduction in an endpoint measurement after treatment? From two glioblastoma patients, 32 untreated organotypic spheroids were cultured and sectioned entirely (14-100 sections per spheroid). The viable fraction was determined as endpoint by automated image analysis in sections and used to establish the minimally-detectable difference between a treatment and reference group. Variance was considerable with a coefficient of variance of 21%. The biological variation in viability in sections of spheroids produced 97% of variance when sample size was large. Variance increased when numbers of spheroids but not numbers of sections per spheroid were reduced. A minimum of 12 spheroids per group and one section per spheroid was required for a valid comparison of a treatment group and a control group. When 10 treatment groups and one control group were compared, 16 spheroids per group were required. Thus, the statistical power depended almost entirely on the number of organotypic glioma spheroids and hardly on the number of sections per spheroid. The organotypic glioma spheroid model does not appear to be suitable for high-throughput screening of anticancer strategies, because of the relatively large number of spheroids required. It is the model of choice for low-throughput screening, because this model is far more representative for the parental tumor than any other more efficient glioma model.

Anesthetic pentobarbital inhibits proliferation and migration of malignant glioma cells

Malignant gliomas are common and aggressive brain tumors in adults. The rapid proliferation and diffuse brain migration are main obstacles to successful treatment. Here we show that pentobarbital, a central depressant introduced clinically a century ago, is capable of suppressing proliferation and migration of C6 malignant glioma cells in a concentration-dependent manner. Pentobarbital also leads to a G1 phase cell cycle arrest accompanied by suppressed G1 cell cycle regulatory proteins Cyclin D1, Cyclin D3, CDK2 and phosphorylated Rb. In addition, noticeable morphological changes and interrupted alpha-tubulin microtubule assembly are induced by pentobarbital exposure. Intracellular signal pathways involved in the effect of pentobarbital is concerned with inactivation of ERK, c-Jun and Akt. Together, these findings suggest anti-proliferation and anti-migration effects of pentobarbital on malignant gliomas, most likely by arresting cell cycle and interfering microtubule. ERK, c-Jun MAPK and PI3K/Akt are possible signaling pathways involved.

Telomere 3' overhang-specific DNA oligonucleotides induce autophagy in malignant glioma cells

Telomere 3' overhang-specific DNA oligonucleotides (T-oligos) induce cell death in cancer cells, presumably by mimicking telomere loop disruption. Therefore, T-oligos are considered an exciting new therapeutic strategy. The purpose of this study was to elucidate how T-oligos exert antitumor effects on human malignant glioma cells in vitro and in vivo. We demonstrated that T-oligos inhibited the proliferation of malignant glioma cells through induction of nonapoptotic cell death and mitochondria hyperpolarization, whereas normal astrocytes were resistant to T-oligos. Tumor cells treated with T-oligos developed features compatible with autophagy, with development of autophagic vacuoles and conversion of an autophagy-related protein, microtubule-associated protein 1 light chain 3 from type I (cytoplasmic form) to type II (membrane form of autophagic vacuoles). A reverse-phase protein microarray analysis and Western blotting revealed that treatment with T-oligos inhibited the mammalian target of the rapamycin (mTOR) and the signal transducer and activator of transcription 3 (STAT3). Moreover, pretreatment with T-oligos significantly prolonged the survival time of mice inoculated intracranially with malignant glioma cells compared with that of untreated mice and those treated with control oligonucleotides (P=0.0065 and P=0.043, respectively). These results indicate that T-oligos stimulate the induction of nonapoptotic autophagic also known as type II programmed cell death and are thus promising in the treatment of malignant glioma.

Convection enhanced delivery for treating brain tumors and selected neurological disorders: symposium review

In 2003 the Cleveland Clinic Brain Tumor Institute sponsored a symposium to mark the progress being made in what was then a new approach to treating brain tumors - convection enhanced delivery (CED) [Vogelbaum MA (2005) J NeuroOncol 73(1):57-69]. A second symposium was held in February, 2006, to review new accomplishments and identify promising avenues of research in this evolving but still novel therapy. Among the general subjects covered by a host of international experts in their respective fields were advances in CED technology, new clinical applications of the technology, advances in CED-related imaging procedures, reviews of current or proposed trials, new drugs and the status of projects moving from lab to clinical practice. Specific subjects included the design of new catheters, the development of mathematic models for planning, novel therapeutics for CED treatment of stroke, spinal cord degenerative disease and epilepsy, liposome-based agents administered via CED, ultra-sound driven CED, monitoring the in vivo effects of intratumoral paclitaxel and other topics. Each speaker's presentation has been abstracted along with relevant references.

Randomized Study of Paclitaxel and Tamoxifen Deposition into Human Brain Tumors: Implications for the Treatment of Metastatic Brain Tumors

PURPOSE

Drug resistance in brain tumors is partially mediated by the blood-brain barrier of which a key component is P-glycoprotein, which is highly expressed in cerebral capillaries. Tamoxifen is a nontoxic inhibitor of P-glycoprotein. This trial assessed, in primary and metastatic brain tumors, the differential deposition of paclitaxel and whether tamoxifen could increase paclitaxel deposition.

EXPERIMENTAL DESIGN

Patients for surgical resection of their primary or metastatic brain tumors were prospectively randomized to prior paclitaxel alone (175 mg/m(2)/i.v.) or tamoxifen for 5 days followed by paclitaxel. Central and peripheral tumor, surrounding normal brain and plasma, were analyzed for paclitaxel and tamoxifen.

RESULTS

Twenty-seven patients completed the study. Based on a multivariate linear regression model, no significant differences in paclitaxel concentrations between the two study arms were found after adjusting for treatment group (tamoxifen versus control). However, in analysis for tumor type, metastatic brain tumors had higher paclitaxel concentrations in the tumor center (1.93-fold, P = 0.10) and in the tumor periphery (2.46-fold, P = 0.039) compared with primary brain tumors. Pharmacokinetic analyses showed comparable paclitaxel areas under the serum concentration between treatment arms.

CONCLUSIONS

Paclitaxel deposition was not increased with this tamoxifen schedule as the low plasma concentrations were likely secondary to concurrent use of P-450-inducing medications. However, the statistically higher paclitaxel deposition in the periphery of metastatic brain tumors provides functional evidence corroborating reports of decreased P-glycoprotein expression in metastatic versus primary brain tumors. This suggests that metastatic brain tumors may respond to paclitaxel if it has proven clinical efficacy for the primary tumor's histopathology.

Pharmacokinetics and Metabolism in Mice of IDN 5390 (13-(N-Boc-3-i-butylisoserinoyl)-C-7,8-seco-10-deacetylbaccatin III), a New Oral C-seco-Taxane Derivative with Antiangiogenic Property Effective on Paclitaxel-Resistant Tumors

IDN 5390 (13-(N-Boc-3-i-butylisoserinoyl)-C-7,8-seco-10-deacetylbaccatin III) is a new taxane, derived from 7,8-C-seco-10-deacetylbaccatin, selected for its ability to inhibit angiogenesis, mainly by acting on endothelial cell motility, and for its selective activity on class III beta-tubulin. In vivo, IDN 5390 shows activity against paclitaxel-sensitive and -resistant tumors when administered on a prolonged, continuous dosage schedule. We studied the pharmacokinetics and bioavailabilty of the drug in mice after single and repeated oral treatment. IDN 5390 was rapidly absorbed after oral administration, with good bioavailability (43%). After intravenous injection, it was extensively distributed in tissue, mainly the liver, kidney, and heart, with low but persistent levels in brain. The kinetics appear dose-dependent with a clearance of 2.6, 1.4, and 0.9 l/kg at, respectively, 60, 90, and 120 mg/kg, and a half-life 24, 36, and 54 min. After prolonged daily oral doses given for 2 weeks, we found that there was a decrease in drug availability; i.e., the area under the concentration-time curve value after p.o. daily administration on day 14 was 2-fold lower than that on day 1. Metabolism plays a major role in elimination of the drug, and at least 12 metabolites were identified in feces and urine. The percentage excreted as metabolites after an oral dose (42%) was higher than that after the i.v. dose (33%), suggesting a first-pass effect. Four metabolites were found in plasma at detectable levels; one of them, with restored taxane scaffold, is a species 3 times more potent than IDN 5390, possibly contributing to the observed anti-tumor activity.

Lymphocyte chemotaxis is regulated by histone deacetylase 6, independently of its deacetylase activity

In this work, the role of HDAC6, a type II histone deacetylase with tubulin deacetylase activity, in lymphocyte polarity, motility, and transmigration was explored. HDAC6 was localized at dynamic subcellular structures as leading lamellipodia and the uropod in migrating T-cells. However, HDAC6 activity did not appear to be involved in the polarity of migrating lymphocytes. Overexpression of HDAC6 in freshly isolated lymphocytes and T-cell lines increased the lymphocyte migration mediated by chemokines and their transendothelial migration under shear flow. Accordingly, the knockdown of HDAC6 expression in T-cells diminished their chemotactic capability. Additional experiments with HDAC6 inhibitors (trichostatin, tubacin), other structural related molecules (niltubacin, MAZ-1391), and HDAC6 dead mutants showed that the deacetylase activity of HDAC6 was not involved in the modulatory effect of this molecule on cell migration. Our results indicate that HDAC6 has an important role in the chemotaxis of T-lymphocytes, which is independent of its tubulin deacetylase activity.

Correction of malignant behavior of tumor cells by traditional Chinese herb medicine through a restoration of p53

We have previously demonstrated that a UVC-induced tumorigenic HeLa x skin fibroblast cell line could be induced to form a more normal phenotypic state ('reversion'), including loss of IAP expression. We have now used the loss of IAP expression to monitor the enhancement of this reversion in the cervical cancer cell line, HeLa, by a traditional Chinese herb medicine (TCM), Yigan Kang (YGK). IAP level decreased, and the reversion frequency increased, in a dose-dependent manner at concentrations of YGK of more than 10 mg. YGK significantly repressed E6/E7 oncogenes at the transcriptional level, with subsequent reactivation of p53 and p21 expression (P<0.01). YGK had little effect on the cell cycle of HeLa cells and slightly increased the apoptotic cell death between 20 and 40 mg. In vivo, tumorigenicity studies were performed using six different animal experimental protocols, which demonstrated that YGK was effective at inducing reversion of the tumorigenic phenotype, with YGK-treated HeLa cells showing much less aggressive tumor growth than untreated cells. YGK may raise the possibility of the continuing management of some cancers as a chronic condition in which the malignant behavior of the tumor cells is constrained.

The brain slice chamber, a novel variation of the Boyden Chamber Assay, allows time-dependent quantification of glioma invasion into mammalian brain in vitro

Glioma cell invasion occurs in a complex micromilieu consisting of neural and glial cells, myelinated fiber tracts, blood vessels and extracellular matrix proteins. The present work describes the brain slice chamber (BSC) as a novel experimental model for assessing invasion of glioma cells into adult mammalian white and gray matter on the basis of the well known Boyden chamber system. As a matrix for invasive tumor cells we used freshly prepared brain tissue from adult pigs. The tissue was sectioned into 40 mum slices that were mechanically fixed to a millipore filter. The neural structures and the three-dimensional architecture of the slice was preserved as verified by immunohistochemistry, light- and electron microscopy. Human U-373 and U87 astrocytoma cells stably transfected with green fluorescent protein (GFP) were assessed for their invasiveness into the brain-slices during a 24 h period. Invasion of U-87 GFP cells was quantified at different time intervals by confocal laser scanning microscopy showing more intense invasion into white compared to gray matter. Two cytostatics (vincristin and paclitaxel) which both are known to affect the cytoskeleton, inhibited glioma cell invasion in a dose dependent manner, which makes the presented model system suitable for functional experiments. In conclusion, the BSC represents a valid and rapid experimental model that may be used to describe the invasive behavior of glioma cells within the preserved three-dimensional structure of mammalian brain tissue in vitro.

Combined effects of zoledronic acid and doxorubicin on breast cancer cell invasion in vitro

The bisphosphonate zoledronic acid and the cytotoxic drug doxorubicin induce synergistic levels of apoptosis in breast cancer cells. As zoledronic acid and doxorubicin have been shown to reduce cell invasion and migration, we have investigated if these drugs also act synergistically on breast cancer invasion in vitro. MCF7 cells were treated with 0.05 microM doxorubicin/4 h followed by 1 or 10 microM zoledronic acid/24 h (or the reverse sequence). To study invasion, MCF7 cells were either grown on Transwell membranes coated with Matrigel or in a 24-well plate. Cells were treated sequentially using the above drug combinations, prior to starting the invasion assays for 48 h. Cell growth and death were also assessed under the same conditions. We found that invasion of MCF7 cells treated with zoledronic acid and doxorubicin was significantly reduced when compared with control, but the effect was dependent on drug sequence. At 1 microM, zoledronic acid significantly reduced invasion only if cells were pre-treated with doxorubicin, but cell growth was unaffected. For 10 microM zoledronic acid, invasion was reduced when administered before or after the doxorubicin, but this dose of zoledronic acid caused a significant reduction in MCF7 growth. Apoptosis was not induced by any of the drug doses and combinations. We conclude that pre-treatment with 0.05 microM doxorubicin followed by 1 microM zoledronic acid reduces invasion when cells were grown on Matrigel. For 10 microM zoledronic acid, pre- or post-doxorubicin also reduces invasion, but for this combination inhibition of cell growth may contribute to the reduction in invasion observed.

O-(2-[18F]fluoroethyl)-L-tyrosine PET for monitoring the effects of convection-enhanced delivery of paclitaxel in patients with recurrent glioblastoma

PURPOSE

Convection-enhanced delivery (CED) of paclitaxel is a new locoregional approach for patients with recurrent glioblastoma. The aim of this study was to evaluate O-(2-[(18)F]fluoroethyl)-L-tyrosine (FET) positron emission tomography (PET) in monitoring the effects of this type of direct drug delivery.

METHODS

Eight patients with recurrent glioblastoma underwent CED of paclitaxel, which was infused over stereotactically placed catheters into the tumour. FET PET and MRI were performed before and 4 weeks after therapy and then at 3-month intervals to document follow-up. For quantitative evaluation, SUV(max)(tumour)/SUV(mean)(background) ratios were calculated.

RESULTS

At baseline all tumours showed gadolinium enhancement and high FET uptake (SUV(max)/BG 3.2+/-0.8). Four weeks after CED, a statistically significant decrease in FET uptake was seen (SUV(max)/BG-17%; p<0.01). During follow-up, no recurrence was observed within the CED area. Two out of eight patients with extended tumours died 4 and 5 months after treatment, most probably from local complications. Temporarily stable disease with stable FET uptake was observed in six of eight patients; this was followed by progression and increasing FET uptake ratios (+46%) distant from the CED area in five of the six patients 3-13 months after CED. One patient still presents stable FET uptake 10 months after CED. MRI showed unchanged/increasing contrast enhancement and oedema without ability to reliably assess disease progression.

CONCLUSION

FET PET is a valuable tool in monitoring the effects of CED of paclitaxel. In long-term follow-up, stable or decreasing FET uptake, even in contrast-enhancing lesions, is suggestive of reactive changes, whereas increasing ratios appear always to be indicative of recurrence. Therefore, FET PET is more reliable than MRI in differentiating stable disease from tumour regrowth.

Effects of docetaxel on antigen presentation-related functions of human monocyte-derived dendritic cells

PURPOSE

Docetaxel (TXT) is a unique chemotherapeutic agent that has been approved for treating various types of malignancies. TXT stabilizes microtubule assembly in cells and causes various dysfunctions of microtubule-dependent cellular events. Patients with advanced malignancies are beginning to receive TXT in combination with immunotherapy; however, the influence of TXT at clinically achievable serum concentrations (less than 10(-6) M) on antigen presentation-related functions of human monocyte-derived dendritic cells (Mo-DCs) remains unclear.

METHODS

Immature Mo-DCs (imMo-DCs) were generated from peripheral blood monocytes with interleukin-4 and granulocyte-macrophage colony-stimulating factor in vitro. Mature Mo-DCs (mMo-DCs) were induced from imMo-DCs with tumor necrosis factor-alpha and prostaglandin E(2).

RESULTS

TXT at concentrations lower than 10(-7) M did not significantly affect cellular viability, phagocytosis, or expression of antigen presentation-related molecules of Mo-DCs. In contrast, TXT at concentrations lower than 10(-9) M significantly suppressed directional motility of imMo-DCs toward MIP-1alpha and of mMo-DCs toward MIP-3beta. However, TXT had no effect on either CCR1 expression by imMo-DCs or CCR7 expression by mMo-DCs. No gross changes in the microtubule skeleton were evident by immunofluorescence microscopy after treatment with TXT at less than 10(-8) M. However, reduced numbers of imMo-DCs with podosomes localized primarily in one cell region were observed.

CONCLUSIONS

The present results indicate that different concentrations of TXT influence antigen presentation-related functions differently. In particular, TXT at relatively low therapeutic doses disrupts chemotactic motility of Mo-DCs.

A new superinvasive in vitro phenotype induced by selection of human breast carcinoma cells with the chemotherapeutic drugs paclitaxel and doxorubicin

Doxorubicin- and paclitaxel-selected variants of an in vitro invasive clonal population of the human breast cancer cell line, MDA-MB-435S, were established by pulse selection, and exhibited a novel ‘superinvasive’ phenotype. This phenotype is characterised by an ability to relocate to another surface following invasion through matrigel and membrane pores, by decreased adhesion to extracellular matrix proteins and by increased motility. This may represent an in vitro model of a step in the metastatic process occurring subsequent to invasion. The paclitaxel-resistant variants, MDA-MB-435S-F/Taxol-10p and MDA-MB-435S-F/Taxol-10p4p were resistant to paclitaxel, vincristine and docetaxel, but not to doxorubicin, carboplatin, etoposide or 5-fluorouracil. The doxorubicin-selected variants MDA-MB-435S-F/Adr-10p and MDA-MB-435S-F/Adr-10p10p, in contrast, exhibited only small increases in resistance to doxorubicin, although they were slightly resistant to VP-16 and docetaxel, and exhibited increased sensitivity to paclitaxel, carboplatin and 5-fluorouracil.

Arsenic trioxide induces autophagic cell death in malignant glioma cells by upregulation of mitochondrial cell death protein BNIP3

Arsenic trioxide (As(2)O(3)) has shown considerable efficacy in treating hematological malignancies with induction of programmed cell death (PCD) type I, apoptosis. However, the mechanisms underlying the antitumor effect of As(2)O(3) on solid tumors are poorly defined. Previously, we reported that As(2)O(3) induced autophagic cell death (PCD type II) but not apoptosis in human malignant glioma cell lines. The purpose of this study was to elucidate the molecular pathway leading to autophagic cell death. In this study, we demonstrated that the cell death was accompanied by involvement of autophagy-specific marker, microtubule-associated protein light chain 3 (LC3), and damage of mitochondrial membrane integrity, but not by caspase activation. Analysis by cDNA microarray, RT-PCR, and Western blot showed that cell death members of Bcl-2 family, Bcl-2/adenovirus E1B 19-kDa-interacting protein 3 (BNIP3) and its homologue BNIP3-like (BNIP3L), were upregulated in As(2)O(3)-induced autophagic cell death. Exogenous expression of BNIP3, but not BNIP3L, induced autophagic cell death in malignant glioma cells without As(2)O(3) treatment. When upregulation of BNIP3 induced by As(2)O(3) was suppressed by a dominant-negative effect of the transmembrane-deleted BNIP3 (BNIP3 Delta TM), autophagic cell death was inhibited. In contrast, BNIP3 transfection augmented As(2)O(3)-induced autophagic cell death. These results suggest that BNIP3 plays a central role in As(2)O(3)-induced autophagic cell death in malignant glioma cells. This study adds a new concept to characterize the pathways by which As(2)O(3) acts to induce autophagic cell death in malignant glioma cells.

Patupilone (epothilone B, EPO906) and imatinib (STI571, Glivec) in combination display enhanced antitumour activity in vivo against experimental rat C6 glioma

PURPOSE

The microtubule-stabilizing agent patupilone (epothilone B, EPO906) and the tyrosine kinase inhibitor imatinib (STI571, Glivec) which primarily inhibits Bcr-Abl, PDGF and c-Kit tyrosine kinase receptors, were combined in vivo to determine if any interaction would occur with respect to antitumour effect and tolerability using rat C6 glioma xenografted into nude mice.

METHODS

Patupilone and imatinib were administered alone or in combination at suboptimal doses. Imatinib treatment (orally once daily) was initiated 4 days after s.c. injection of rat C6 glioma cells into athymic nude mice and patupilone administration (i.v. once per week) was started 3 or 4 days after imatinib treatment.

RESULTS

As a single agent, imatinib was inactive in the regimens selected (100 mg/kg: T/C 86% and 116%; 200 mg/kg: T/C 68% and 84%; two independent experiments), but well tolerated (gain in body weight and no mortalities). Patupilone weekly monotherapy demonstrated dose-dependent antitumour effects (1 mg/kg: T/C 67% and 70%; 2 mg/kg: T/C 32% and 63%; 4 mg/kg: T/C 3% and 46%). As expected, dose-dependent body weight losses occurred (final body weight changes at 1 mg/kg were -7% and -3%; at 2 mg/kg were -23% and -13%; and at 4 mg/kg were -33% and -15%). Combining 2 mg/kg patupilone and 200 mg/kg per day imatinib in one experiment produced a non-statistically significant trend for an improved antitumour effect over patupilone alone (combination, T/C 9%), while in the second experiment, enhancement was seen with the combination and reached statistical significance versus patupilone alone (combination, T/C 22%; P=0.008). Reduction of the imatinib dose to 100 mg/kg per day resulted in no enhancement of antitumour activity in combination with 2 mg/kg patupilone. Reduction of the patupilone dose to 1 mg/kg resulted in a reduced antitumour effect, and only a trend for synergy with either imatinib dose (combination, T/C 46% and 40%). Pooling the data from the two experiments confirmed a significant synergy for the combination of 2 mg/kg patupilone and 200 mg/kg per day imatinib (P=0.032), and a trend for synergy at the 1 mg/kg patupilone dose. Reduction in the imatinib dose to 100 mg/kg per day resulted only in additivity with either dose of patupilone. Body weight losses were dominated by the effect of patupilone, since no greater body weight loss was observed in the combination groups.

CONCLUSION

Combining patupilone with high-dose imatinib produced an increased antitumour effect without affecting the tolerability of treatment in a relatively chemoresistant rat C6 glioma model. Such results indicate that further evaluation is warranted, in particular to elucidate possible mechanisms of combined action.

The Effects of Paclitaxel on the Three Phases of Restenosis

PURPOSE

We sought to evaluate the growth-modulating potential of paclitaxel on cultured human arterial smooth muscle cells depending on the administered dose.

MATERIAL AND METHODS

For all experiments human arterial smooth muscle cells (SMCs) were used. SMCs were either cultured for 5 days or for 20 days with paclitaxel (doses: 10(-7) M, 10(-8) M, 10(-9) M). For a total period of 20 days, proliferation kinetics of the SMC were analyzed. To assess the clonogenic activity of the SMC colony-forming assays were performed. Drug- and dose-dependent cell cycle changes were analyzed by flow cytometry. The effect on cell migration was examined in a 2-chamber migration system. The effects of paclitaxel on the synthesis of tenascin were examined via immunofluorescence.

RESULTS

Depending on the dose administered, paclitaxel proved to inhibit SMC proliferation effectively when administered during the total period of 20 days. When incubated for 5 days with doses of paclitaxel ranging between 10(-8) M and 10(-9) M, SMCs showed clear signs of regeneration. When being incubated with 10(-7) M of paclitaxel, however, SMCs reacted with a reduction in cell proliferation, a reduced clonogenic activity, and a drug-induced G2/M phase block. SMC migration was inhibited effectively as well as extracellular matrix formation.

CONCLUSION

Paclitaxel is a potent inhibitor of SMC proliferation, SMC migration, and extracellular matrix formation in vitro, with all three phases of the restenosis process inhibited effectively.

Bcl-2 and Bcl-xL are important for the induction of paclitaxel resistance in human hepatocellular carcinoma cells

In this study we have investigated the mechanism underlying resistance to the chemotherapeutic drug paclitaxel in tumors of hepatocellular carcinoma (HCC) patients. Treatment with paclitaxel led to potent inhibition of growth of Hep3B hepatoma cells, but did not affect the growth properties of SNU-368 and SNU-398 cell lines that were established from primary HCC tumors. The growth inhibitory effect induced by paclitaxel correlated with levels of intracellular p21 and resulted in cell cycle arrest at the G2/M phase. However, paclitaxel treatment did not alter intracellular p53 levels. Instead, SNU-398 cells express high levels of the anti-apoptotic Bcl-2 and Bcl-x(L) proteins and the level of Bcl-x(L) could be further induced upon paclitaxel treatment. In contrast, Hep3B cells express pro-apoptotic members of the Bcl family and fail to induce Bcl-x(L) upon paclitaxel treatment. Therefore, these results strongly suggest that Bcl-2 and Bcl-x(L) play an important role in mediating resistance to paclitaxel.

Expression of fascin, an actin-bundling protein, in astrocytomas of varying grades

Malignant astrocytomas are highly infiltrative neoplasms that invade readily into regions of normal brain. On a cellular basis, the motility and invasiveness of human cancers can be ascribed in part to complex rearrangements of the actin cytoskeleton that are governed by several actinbinding proteins. One such actin-binding protein that has been linked to the invasive behavior of carcinomas is fascin, which serves to aggregate F actin into bundles. In this study, we examined the expression of fascin in a series of human malignant astrocytomas (WHO grades I-IV). Five grade I, 5 grade II, 10 grade III, and 26 grade IV human astrocytomas were examined for fascin and glial fibrillary acidic protein (GFAP) expression by double immunofluorescence confocal microscopy. Expression of fascin and GFAP was also determined by Western blot analysis. Fascin expression increased with increasing WHO grade of astrocytoma. This is in marked contrast to GFAP expression, which decreased with increasing WHO grade. In grades I and II neoplasms, and within non-neoplastic brain, fascin and GFAP were expressed diffusely within regions examined. However, in the higher-grade astrocytomas (grades III and IV), fascin and GFAP were expressed regionally in distinctly separate tumor cell populations. This is the first study to demonstrate the expression of fascin in human astrocytic neoplasms. The role that fascin plays in contributing to the invasive phenotype of anaplastic astrocytomas awaits further study and investigation.

Convection-enhanced delivery of paclitaxel for the treatment of recurrent malignant glioma: a Phase I/II clinical study

Object. A minority of patients with recurrent glioblastomas multiforme (GBMs) responds to systemic chemotherapy. The authors investigated the safety and efficacy of intratumoral convection-enhanced delivery (CED) of paclitaxel in patients harboring histologically confirmed recurrent GBMs and anaplastic astrocytomas.

Methods. Fifteen patients received a total of 20 cycles of intratumoral CED of paclitaxel. The patients were observed daily by performing diffusion-weighted (DW) magnetic resonance (MR) imaging to assess the convective process and routine diagnostic MR imaging to identify the tumor response. Effective convection was determined by the progression of the hyperintense signal within the tumor on DW MR images, which corresponded to a subsequent lytic tumor response displayed on conventional MR images. Of the 15 patients, five complete responses and six partial responses were observed, giving a response rate of 73%. The antitumor effect was confirmed by one biopsy and three en bloc resections of tumors, which showed a complete response, and by one tumor resection, which demonstrated a partial response. Lack of convection and a poor tumor response was associated with leakage of the convected drug into the subarachnoid space, ventricles, and cavities formed by previous resections, and was seen in tumors containing widespread necrosis. Complications included transient chemical meningitis in six patients, infectious complications in three patients, and transient neurological deterioration in four patients (presumably due to increased peritumoral edema).

Conclusions. On the basis of our data we suggest that CED of paclitaxel in patients with recurrent malignant gliomas is associated with a high antitumor response rate, although it is associated with a significant incidence of treatment-associated complications. Diffusion-weighted MR images may be used to predict a response by demonstrating the extent of convection during treatment. Optimization of this therapeutic approach to enhance its efficacy and reduce its toxicity should be explored further.

Locoregional opening of the rodent blood-brain barrier for paclitaxel using Nd:YAG laser-induced thermo therapy: a new concept of adjuvant glioma therapy?

BACKGROUND AND OBJECTIVES

Nd:YAG laser-induced thermo therapy (LITT) of rat brains is associated with blood-brain barrier (BBB) permeability changes. We address the question of whether LITT-induced locoregional disruption of the BBB could possibly allow a locoregional passage of chemotherapeutic agents into brain tissue to treat malignant glioma.

STUDY DESIGN/MATERIALS AND METHODS

CD Fischer rats were subject to LITT of the left forebrain. Disruption of the BBB was analyzed using Evans blue and immunohistochemistry (IH). Animals were perfused with paclitaxel, and high-pressure liquid chromatography (HPLC) was employed to analyze the content of paclitaxel in brain and plasma samples.

RESULTS

LITT induces an opening of the BBB as demonstrated by locoregional extravasation of Evans blue, C3C, fibrinogen, and IgM. HPLC proved the passage of paclitaxel across the disrupted BBB.

CONCLUSIONS

LITT induces a locoregional passage of chemotherapeutic agents into the brain tissue. This is of potential interest for the treatment of brain tumors.

Proliferation, migration, and invasion of human glioma cells exposed to fractionated radiotherapy in vitro

Radiotherapy is a well established treatment for malignant gliomas. This study describes the migration, proliferation, and invasion behaviour of two human glioma cell lines (GaMg and U-87 Mg) grown as multicellular tumour spheroids after radiotherapy. Migration and proliferation studies were performed using conventional and accelerated fractionation up to 60 Gy and 59.4 Gy, respectively. A dose-dependent growth and migratory response to irradiation independent of the type of fractionation was observed. A coculture system in which tumour spheroids were confronted with foetal rat brain aggregates was used for invasion studies. Marked invasion of the glioma spheroids into the brain aggregates occurred with or without radiotherapy. For the GaMg cells, flow cytometric DNA histograms after treatment with 10 Gy and 40 Gy showed an accumulation of cells in the G2/M phase of the cell cycle. Radiotherapy inhibits tumour cell growth and migration, but the invasiveness of the remaining tumour cells seems to be unaffected.

Temozolomide induces apoptosis and senescence in glioma cells cultured as multicellular spheroids

Temozolomide is an alkylating cytostatic drug that finds increasing application in the treatment of melanoma, anaplastic astrocytoma and glioblastoma multiforme. The compound is a prodrug that decomposes spontaneously, independent of an enzymatic activation step. DNA methylation induces futile mismatch repair cycles and depletion of the DNA repair enzyme O(6)-methylguanine-DNA methyltransferase should then initiate programmed cell death. We show drug-dependent inhibition of tumour growth in a three-dimensional cell culture model of the glioma cell lines U87MG and GaMG. Migrational behaviour of the glioblastoma cells remained unaltered. However, coincubation of tumour spheroids with primary brain aggregates showed reduced tumour cell invasion into brain tissue in the presence of temozolomide. This was not achieved by slowing cellular migration, as temozolomide-treated cells displayed no reduced motility. By transferase-mediated dUTP nick-end labelling (TUNEL) of apoptotic nuclei, we found that the drug was able to induce apoptosis throughout the tumour cell spheroids. Apoptosis was highest in the core region of the spheroids. Repetitive application of sublethal doses of temozolomide to multicellular spheroids resulted in the development of drug resistance in GaMG cells. We suggest that temozolomide is a strong initiator of apoptosis in glioblastoma tumour cells in a spheroid cell culture system, when cells are already in a stressful environment.

Growth-inhibiting effects of intralesional docetaxel and paclitaxel on an experimental model of malignant neuroectodermal tumor

Taxoids are effective agents against a wide variety of tumors, but their effectiveness on neuroectodermal tumors is not well-known. For this reason we have carried out an experimental study on the effect of intratumoral administration of docetaxel (DC) and paclitaxel (PC) on tumor growth, using a murine model of malignant neuroectodermal tumor. The results showed a delay in tumor growth in animals treated with PC compared with controls (dose of 5 mg/kg, three times per week every other day, forming a cycle; three cycles were completed with a break of a week between each cycle). The total dose administered to each animal was 45 mg/kg. When DC was administered, the results showed distinct tumor growth inhibition and tumor regression in 80% of animals (intratumoral administration at a dose of 5 mg/kg, three times per week every other day forming a cycle; three cycles were completed with a break of a week between each cycle). The total dose administered to each animal was 20 mg/kg. These results suggest the utility of taxoids, mainly DC, by intralesional administration, on malignant tumors of the nervous system.

Tumor vasculature is targeted by the combination of combretastatin A-4 and hyperthermia

BACKGROUND AND PURPOSE

Combretastatin A-4 disodium phosphate (CA-4) enhances thermal damage in s.c. BT(4)An rat gliomas. We currently investigated how CA-4 and hyperthermia affect the tumor microenvironment and neovasculature to disclose how the two treatment modalities interact to produce tumor response.

METHODS

By confocal microscopy and immunostaining for von Willebrand factor, we examined the extent of vascular damage subsequent to CA-4 (50 mg/kg) and hyperthermia (waterbath 44 degrees C, 60 min). The influence on tumor oxygenation was assessed using interstitial pO(2)-probes (Licox system) and by immunostaining for pimonidazole. We examined the direct effect of CA-4 on the tumor cell population by flow cytometry (cell cycle distribution) and immunostaining for beta-tubulin (cytoskeletal damage).

RESULTS

Whereas slight vascular damage was produced by CA-4 in the BT(4)An tumors, local hyperthermia exhibited moderate anti-vascular activity. In tumors exposed to CA-4 3 h before hyperthermia, massive vascular damage ensued. CA-4 reduced the pO(2) from 36.1 to 17.6 mmHg (P=0.01) in the tumor base, and tumor hypoxia increased slightly in the tumor center (pimonidazole staining). Extensive tumor hypoxia developed subsequent to hyperthermia or combination therapy. Despite a profound influence on beta-tubulin organization in vitro, CA-4 had no significant effect on the cell cycle distribution in vivo.

CONCLUSION

Our results indicate that the anti-vascular activity exhibited by local hyperthermia can be augmented by previous exposure to CA-4.