Penetration of substances into tumor tissue: a methodological study with microelectrodes and cellular spheroids

Microtubular Assessment of C6 Rat Glioma Cell Spheroids Developed in Transparent Liquid Marbles or Hanging Drops

Glioblastoma is a brain tumour frequently used as an experimental model to exploit innovative therapeutic approaches due to its high lethality and refractoriness to therapies. Part of these innovative anticancer therapies address cytoskeletal microtubules (MTs) since specific tubulin post-translational modifications (PTMs) are considered markers of tumour plasticity. In vitro studies, which traditionally employ two-dimensional (2D) culture systems, are now being replaced by three-dimensional (3D) systems that more closely mimic in vivo physiological conditions and allow a better understanding of the signalling between cells. In this work, we compared 2 liquid base 3D methods for the generation of spheroids from C6 rat glioma cells (RGCs) using 30 µL of liquid marble (LM) or the hanging drops (HDs), which contained 2 different cell numbers (5000 or 15,000). After 24 or 48 h of in vitro culture (IVC), the morphology of the spheroids was observed and the behaviour of the two main tubulin PTMs, tyrosinated α-tubulin (Tyr-T) and acetylated α-tubulin (Ac-T), was evaluated by fluorescence and Western blot (WB). RGCs spontaneously formed spherical agglomerates more rapidly in the LM than in the HD system. Cell density influenced the size of the spheroids, which reached a larger size (> of 300 µm Ø), with 15,000 cells compared to 5000 cells (150 µm Ø). Moreover, an increase in Tyr-T and Ac-T was observed in both the HD and LM system from 24 to 48 h, with the highest values shown in the 48 h/LM spheroids of 5000 cells (p < 0.05). In conclusion, by comparing the morphology and microtubular architecture of spheroids from C6 rat glioma cells developed by LM or HD methodology, our findings demonstrate that the use of a fumed silica microbioreactor boosts the induction and maintenance of a high plasticity state in glioma cells. RGCs cultured in LM express levels of tubulin PTMs that can be used to evaluate the efficacy of new anticancer therapies.

Triazole-estradiol analogs: A potential cancer therapeutic targeting ovarian and colorectal cancer

1,2,3-triazoles have continuously shown effectiveness as biologically active systems towards various cancers, and when used in combination with steroid skeletons as a carrier, which can act as a drug delivery system, allows for a creation of a novel set of analogs that may be useful as a pharmacophore leading to a potential treatment option for cancer. A common molecular target for cancer inhibition is that of the Epidermal Growth Factor Receptor/Mitogen Activated Protein Kinase pathways, as inhibition of these proteins is associated with a decrease in cell viability. Estradiol-Triazole analogs were thus designed using a molecular modeling approach. Thirteen of the high scoring analogs were then synthesized and tested in-vitro on an ovarian cancer cell line (A2780) and colorectal cancer cell line (HT-29). The most active compound, Fz25, shows low micromolar activity in both the ovarian (15.29 ± 2.19 µM) and colorectal lines (15.98 ± 0.39 µM). Mechanism of action studies proved that Fz25 moderately arrests cells in the G1 phase of the cell cycle, specifically inhibiting STAT3 in both cell lines. Additionally, Fz57 shows activity in the colorectal line (24.19 ± 1.37 µM). Inhibition studies in both cell lines show inhibition against various proteins in the EGFR pathway, namely EGFR, STAT3, ERK, and mTOR. To further study their effects as therapeutics, Fz25 and Fz57 were studied against drug efflux proteins, which are associated with drug resistance, and were found to inhibit the ABC transporter P-glycoprotein. We can conclude that these estradiol-triazole analogs provide a key for future studies targeting protein inhibition and drug resistance in cancer.

Small, Smaller, Nano: New Applications for Potato Virus X in Nanotechnology

Nanotechnology is an expanding interdisciplinary field concerning the development and application of nanostructured materials derived from inorganic compounds or organic polymers and peptides. Among these latter materials, proteinaceous plant virus nanoparticles have emerged as a key platform for the introduction of tailored functionalities by genetic engineering and conjugation chemistry. Tobacco mosaic virus and Cowpea mosaic virus have already been developed for bioimaging, vaccination and electronics applications, but the flexible and filamentous Potato virus X (PVX) has received comparatively little attention. The filamentous structure of PVX particles allows them to carry large payloads, which are advantageous for applications such as biomedical imaging in which multi-functional scaffolds with a high aspect ratio are required. In this context, PVX achieves superior tumor homing and retention properties compared to spherical nanoparticles. Because PVX is a protein-based nanoparticle, its unique functional properties are combined with enhanced biocompatibility, making it much more suitable for biomedical applications than synthetic nanomaterials. Moreover, PVX nanoparticles have very low toxicity in vivo, and superior pharmacokinetic profiles. This review focuses on the production of PVX nanoparticles engineered using chemical and/or biological techniques, and describes current and future opportunities and challenges for the application of PVX nanoparticles in medicine, diagnostics, materials science, and biocatalysis.

Role of Microenvironment in Glioma Invasion: What We Learned from In Vitro Models

The invasion properties of glioblastoma hamper a radical surgery and are responsible for its recurrence. Understanding the invasion mechanisms is thus critical to devise new therapeutic strategies. Therefore, the creation of in vitro models that enable these mechanisms to be studied represents a crucial step. Since in vitro models represent an over-simplification of the in vivo system, in these years it has been attempted to increase the level of complexity of in vitro assays to create models that could better mimic the behaviour of the cells in vivo. These levels of complexity involved: 1. The dimension of the system, moving from two-dimensional to three-dimensional models; 2. The use of microfluidic systems; 3. The use of mixed cultures of tumour cells and cells of the tumour micro-environment in order to mimic the complex cross-talk between tumour cells and their micro-environment; 4. And the source of cells used in an attempt to move from commercial lines to patient-based models. In this review, we will summarize the evidence obtained exploring these different levels of complexity and highlighting advantages and limitations of each system used.

Comprehensive Two- and Three-Dimensional RNAi Screening Identifies PI3K Inhibition as a Complement to MEK Inhibitor AS703026 for Combination Treatment of Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is a major cause of death among breast cancer patients that results from intrinsic and acquired resistance to systemic chemotherapies. To identify novel targets for effective treatment of TNBC through combination strategies with MEK inhibitor (AS703026), we used a novel method of combining high-throughput two- and three-dimensional (2D and 3D) RNAi screening. TNBC cells were transfected with a kinome siRNA library comprising siRNA targeting 790 kinases under both 2D and 3D culture conditions with or without AS703026. Molecule activity predictor analysis revealed the PI3K pathway as the major target pathway in our RNAi combination studies in TNBC. We found that PI3K inhibitor SAR245409 (also called XL765) combined with AS703026 synergistically inhibited proliferation compared with either drug alone (P < 0.001). Reduced in vitro colony formation (P < 0.001) and migration and invasion ability were also observed with the combination treatment (P<0.01). Our data suggest that SAR245409 combined with AS703026 may be effective in patients with TNBC. We conclude that a novel powerful high-throughput RNAi assays were able to identify anti-cancer drugs as single or combinational agents. Integrated and multi-system RNAi screening methods can complement difference between in vitro and in vivo culture conditions, and enriches targets that are close to the in vivo condition.

Plasma and cellular pharmacokinetic considerations for the development and optimization of antitumor block copolymer micelles

INTRODUCTION

Clinical application of anticancer drugs is often limited by poor pharmacokinetic profile. The biocompatible and/or biodegradable block copolymer micelles (BCMs) can improve the pharmacokinetic behavior of drugs, thus enhancing antitumor effect. However, there are still many problems that needed to be solved before there is a wide clinical application of BCMs.

AREAS COVERED

Micelles have been quickly developed recently to deliver hydrophobic antitumor drugs specifically. However, the final therapeutic effect of BCMs is often challenged by many factors in vivo from both plasma and cellular pharmacokinetic view: i) inefficient transport from administration site to tumor tissue; ii) poor penetration into tumor mass; iii) inadequate accumulation in tumor cell; and iv) insufficient intracellular/subcellular release in cells. This review emphasized on the newest methods and solutions based on the main challenges of BCMs application in vivo, and the new problems caused by these methods are also discussed.

EXPERT OPINION

Different strategies and designs of BCMs can help solve problems in each key step respectively. However, overemphasis on one aspect will result in problems on others. Therefore, a comprehensive consideration is urgently needed to integrate the advantages of each strategy and overcome the disadvantages. Only with thorough understanding and scientific assessments, the desired BCMs are expected to be applied in clinical treatments.

Surface modification of SU-8 for enhanced cell attachment and proliferation within microfluidic chips

Advances in micro-electro-mechanical systems (MEMS) have led to an increased fabrication of micro-channels. Microfabrication techniques are utilized to develop microfluidic channels for continuous nutrition supply to cells inside a micro-environment. The ability of cells to build tissues and maintain tissue-specific functions depends on the interaction between cells and the extracellular matrix (ECM). SU-8 is a popular photosensitive epoxy-based polymer in MEMS. The patterning of bare SU-8 alone does not provide the appropriate ECM necessary to develop microsystems for biological applications. Manipulating the chemical composition of SU-8 will enhance the biological compatibility, giving the fabricated constructs the appropriate ECM needed to promote a functional tissue array. This article investigates three frequently used surface treatment techniques: (1) plasma treatment, (2) chemical reaction, and (3) deposition treatment to determine which surface treatment is the most beneficial for enhancing the biological properties of SU-8. The investigations presented in this article demonstrated that the plasma, gelatin, and sulfuric acid treatments have a potential to enhance SU-8's surface for biological application. Of course each treatment has their advantages and disadvantages (application dependent). Cell proliferation was studied with the use of the dye Almar Blue, and a micro-plate reader. After 14 days, cell proliferation to plasma treated surfaces was statistically significantly enhanced (p < 0.00001), compared to untreated surfaces. The plasma treated surface is suggested to be the better of the three treatments for biological enhancement followed by gelatin and sulfuric acid treatments, respectively.

A three-dimensional cell-laden microfluidic chip for in vitro drug metabolism detection

Three-dimensional tissue platforms are rapidly becoming the method of choice for quantification of the heterogeneity of cell populations for many diagnostic and drug therapy applications. Microfluidic sensors and the integration of sensors with microfluidic systems are often described as miniature versions of their macro-scale counterparts. This technology presents unique advantages for handling costly and difficult-to-obtain samples and reagents as a typical system requires between 100 nL to 10 µL of working fluid. The fabrication of a fully functional cell-based biosensor utilizes both biological patterning and microfabrication techniques. A digital micro-mirror (photolithographic) system is initiated to construct the tissue platform while a cell printer is used to precisely embed the cells within the construct. Tissue construct developed with these technologies will provide an early diagnostic of a drug's potential use. A three-dimensional interconnected microfluidic environment has the potential to eliminate the limitations of the traditional mainstays of two-dimensional investigations. This paper illustrates an economical and an innovative approach of fabricating a three-dimensional cell-laden microfluidic chip for detecting drug metabolism.

In vitro irradiation system for radiobiological experiments

BACKGROUND

Although two-dimensional (2-D) monolayer cell cultures provide important information on basic tumor biology and radiobiology, they are not representative of the complexity of three-dimensional (3-D) solid tumors. In particular, new models reproducing clinical conditions as closely as possible are needed for radiobiological studies to provide information that can be translated from bench to bedside.

METHODS

We developed a novel system for the irradiation, under sterile conditions, of 3-D tumor spheroids, the in vitro model considered as a bridge between the complex architectural organization of in vivo tumors and the very simple one of in vitro monolayer cell cultures. The system exploits the same equipment as that used for patient treatments, without the need for dedicated and highly expensive instruments. To mimic the passage of radiation beams through human tissues before they reach the target tumor mass, 96-multiwell plates containing the multicellular tumor spheroids (MCTS) are inserted into a custom-built phantom made of plexiglass, the material most similar to water, the main component of human tissue.

RESULTS

The system was used to irradiate CAEP- and A549-derived MCTS, pre-treated or not with 20 μM cisplatin, with a dose of 20 Gy delivered in one session. We also tested the same treatment schemes on monolayer CAEP and A549 cells. Our preliminary results indicated a significant increment in radiotoxicity 20 days after the end of irradiation in the CAEP spheroids pre-treated with cisplatin compared to those treated with cisplatin or irradiation alone. Conversely, the effect of the radio- chemotherapy combination in A549-derived MCTS was similar to that induced by cisplatin or irradiation alone. Finally, the 20 Gy dose did not affect cell survival in monolayer CAEP and A549 cells, whereas cisplatin or cisplatin plus radiation caused 100% cell death, regardless of the type of cell line used.

CONCLUSIONS

We set up a system for the irradiation, under sterile conditions, of tumor cells grown in 3-D which allows for the use of the same dose intensities and schedules utilized in clinical practice. This irradiation system, coupled with 3-D cell cultures, has the potential to generate information that could be used to individually tailor radiotherapy.

Increased tumor homing and tissue penetration of the filamentous plant viral nanoparticle Potato virus X

Nanomaterials with elongated architectures have been shown to possess differential tumor homing properties compared to their spherical counterparts. Here, we investigate whether this phenomenon is mirrored by plant viral nanoparticles that are filamentous (Potato virus X) or spherical (Cowpea mosaic virus). Our studies demonstrate that Potato virus X (PVX) and Cowpea mosaic virus (CPMV) show distinct biodistribution profiles and differ in their tumor homing and penetration efficiency. Analogous to what is seen with inorganic nanomaterials, PVX shows enhanced tumor homing and tissue penetration. Human tumor xenografts exhibit higher uptake of PEGylated filamentous PVX compared to CPMV, particularly in the core of the tumor. This is supported by immunohistochemical analysis of the tumor sections, which indicates greater penetration and accumulation of PVX within the tumor tissues. The enhanced tumor homing and retention properties of PVX along with its higher payload carrying capacity make it a potentially superior platform for applications in cancer drug delivery and imaging applications.

A review of three-dimensional in vitro tissue models for drug discovery and transport studies

The use of animal models in drug discovery studies presents issues with feasibility and ethical concerns. To address these limitations, in vitro tissue models have been developed to provide a means for systematic, repetitive, and quantitative investigation of drugs. By eliminating or reducing the need for animal subjects, these models can serve as platforms for more tightly controlled, high-throughput screening of drugs and for pharmacokinetic and pharmacodynamic analyses of drugs. The focus of this review is three-dimensional (3D) tissue models that can capture cell-cell and cell-matrix interactions. Compared to the 2D culture of cell monolayers, 3D models more closely mimic native tissues since the cellular microenvironment established in the 3D models often plays a significant role in disease progression and cellular responses to drugs. A growing body of research has been published in the literature, which highlights the benefits of the 3D in vitro models of various tissues. This review provides an overview of some successful 3D in vitro models that have been developed to mimic liver, breast, cardiac, muscle, bone, and corneal tissues as well as malignant tissues in solid tumors.

Etoposide (VP-16) uptake by tumour spheroids and activity in the presence of Brij 30, formulation additives and sodium salicylate

A number of additives typically used in the formulation of poorly soluble drugs can be shown to influence drug transport across various physiological barriers. Multicellular spheroids from a human neuroblastoma cell line (NB1-G) were used to investigate the effect of etoposide in solution, as its commercial formulation, Vepesid, in the presence of a nonionic surfactant, Brij 30, and a hydrotropic agent, sodium salicylate. Enhanced growth delay, apparently related to increased drug uptake, was observed both with the Vepesid and the sodium salicylate formulations. Brij 30, however, showed no enhancement of growth delay or drug uptake at a concentration at which it was not in itself cytotoxic. Significant morphological changes in the spheroid were observed at higher concentrations of additives, particularly with Brij 30, emphasizing the fact that many formulation additives cannot be used with impunity in tissue culture systems. The enhanced uptake of drug into tumour cells and potential synergy between additive and drug is worthy of further investigation.

Homogeneous penetration but heterogeneous binding of antibodies to carcinoembryonic antigen in human colon carcinoma HT-29 spheroids

The monoclonal antibodies 38S1, directed against the carcinoembryonic antigen (CEA), were tested for penetration and binding in human colon carcinoma HT-29 spheroids. Penetration was studied with a method which has not previously been used in immunological investigations. The method, which allows unbound substances to be visualized, is based on freeze drying, vapour fixation, dry sectioning and dry autoradiography. The antibodies penetrated easily and all parts of the HT-29 spheroids seemed to be reached within 15 min. The penetration was even faster than in control glioma U-118MG spheroids that did not express CEA. Binding of the 38S1 antibodies was demonstrated after processing with conventional histology and autoradiography. The binding in the HT-29 spheroids was, after a 1-h incubation period, extremely heterogeneous and occurred mainly in the peripheral parts. More cells were binding the antibodies after 8-h and 32-h incubations and these cells were arranged in peripheral clusters. No binding at all was seen in the CEA-negative glioma spheroids. The distribution of CEA antigens in monolayers and in frozen sections of spheroids of HT-29 cells was analysed with immunohistochemical staining using polyclonal CEA antibodies. The CEA antigens were heterogeneously distributed in both spheroids and monolayers and were as heterogenous as the binding of the monoclonal antibodies in the living spheroids. Thus, the heterogeneous binding in the living spheroids was not due to penetration barriers, but instead to the heterogeneity in the CEA antigen expression.

Penetration of substances into tumour tissue. Model studies using saccharides, thymidine and thymidine-5'-triphosphate in cellular spheroids

In order to achieve a better understanding of factors involved in drug penetration into poorly vascularized tumour tissue, the penetration of some model substances was studied in vitro. Multicellular human tumour spheroids were used as model system. The test substances were [3H]thymidine and [14C]glucose, both of which are capable of passing easily through cell membranes, and [3H]thymidine-5'-triphosphate, [3H]sucrose and [3H]inulin, all of which are unable to pass directly through cell membranes. The penetration of these substances was studied using a dry histological and autoradiographical method preserving the distribution of water-soluble substances. The two thymidine compounds penetrated very efficiently into the spheroids, and their penetration patterns were rather similar. The saccharides differed somewhat in their penetration properties. Glucose had the fastest penetration and inulin the slowest. After 15 min, however, inulin was also found isotropically distributed within the spheroids. Thus, extracellular penetration seemed to be a possible way for a substance to reach the central parts of a spheroid. The differences between the saccharides could be due to some extent to differences in molecular weight and solubility.

Comparative measurements of potassium and chloride with ion-sensitive microelectrodes and x-ray microanalysis in cultured skeletal muscle fibers

Data of the intracellular electrolyte concentration of potassium and chloride in cultured muscle cells measured by x-ray analysis were compared by using the different activity coefficients with intracellular potassium and chloride activities measured with double-barrelled microelectrodes. By using an activity coefficient of 0.6, 95% of the potassium microelectrode measurements are in accordance with the x-ray analysis values, in spite of a scattering of the values. Membrane potential and intracellular potassium values are linearly related. x-ray analysis and ion-sensitive microelectrodes measured the cytoplasmic chloride in the same range. Taking into account known activity coefficients, an error of 25% must be assumed with the intracellular chloride measurements. However, x-ray analysis and ion-sensitive microelectrode investigations are reliable tools to study intracellular potassium and chloride changes, which play an important role in membrane characteristics.