Formation of multicellular tumor spheroids induced by cyclic RGD-peptides and use for anticancer drug testing in vitro

Liquid Overlay and Collagen-Based Three-Dimensional Models for In Vitro Investigation of Multiple Myeloma

Multiple myeloma (MM) clones reside in the bone marrow (BM), which plays a role in its survival and development. The interactions between MM and their neighboring mesenchymal stromal cells (MSCs) have been shown to promote MM growth and drug resistance. However, those interactions are often missing or misrepresented in traditional two-dimensional (2D) culture models. Application of novel three-dimensional (3D) models might recapitulate the BM niche more precisely, which will offer new insights into MM progression and survival. Here, we aimed to establish two 3D models, based on MSC spheroids and collagen droplets incorporating both MM cells and MSCs with the goal of replicating the native myeloma context of the BM niche. This approach revealed that although MSCs can spontaneously assemble spheroids with altered metabolic traits, MSC spheroid culture does not support the integration of MM cells. On the contrary, collagen-droplet culture supported the growth of both cell types. In collagen, MSC proliferation was reduced, with the correlating decrease in ATP production and Ki-67 expression, which might resemble in vivo conditions, rather than 2D abundance of nutrients and space. MSCs and MMs were distributed homogenously throughout the collagen droplet, with an apparent CXCL12 expression in MSCs. In addition, the response of MM cells to bortezomib was substantially reduced in collagen, indicating the importance of 3D culture in the investigation of myeloma cell behavior, as drug resistance is one of the most pertinent issues in cancer therapy.

In Situ Spatial Analysis of Metabolic Heterogeneity in Single Living Tumor Spheroids Using Nanocapillary-Based Electrospray Ionization Mass Spectroscopy

Spatial metabolomic analysis of individual tumor spheroids can help investigate metabolic rearrangements in different cellular regions of a spheroid. In this work, a nanocapillary-based electrospray ionization mass spectroscopy (ESI-MS) method is established that could realize the spatial sampling of cellular components in different regions of a single living tumor spheroid and the subsequent MS analysis for a metabolic study. During the penetration of the nanocapillary into the spheroid for sampling, this "wound surface" at the outer layer of the spheroid takes only 0.1% of the whole area that maximally maintains the cellular activity inside the spheroid for the metabolic analysis. Using the ESI-MS analysis, different metabolic activities in the inner and outer (upper and lower) layers of a single spheroid are revealed, giving a full investigation of the metabolic heterogeneity inside one living tumor spheroid for the first time. In addition, the metabolic activities between the outer layer of the spheroid and two-dimensional (2D)-cultured cells show obvious differences, which suggests more frequent cell-cell and cell-extracellular environment interactions during the culture of the spheroid. This observation not only establishes a powerful tool for the in situ spatial analysis of the metabolic heterogeneity in single living tumor spheroids but also provides molecular information to elucidate the metabolic heterogeneity in this three-dimensional (3D)-cultured cell model.

Doxorubicin-Loaded Polyelectrolyte Multilayer Capsules Modified with Antitumor DR5-Specific TRAIL Variant for Targeted Drug Delivery to Tumor Cells

Recently, biodegradable polyelectrolyte multilayer capsules (PMC) have been proposed for anticancer drug delivery. In many cases, microencapsulation allows to concentrate the substance locally and prolong its flow to the cells. To reduce systemic toxicity when delivering highly toxic drugs, such as doxorubicin (DOX), the development of a combined delivery system is of paramount importance. Many efforts have been made to exploit the DR5-dependent apoptosis induction for cancer treatment. However, despite having a high antitumor efficacy of the targeted tumor-specific DR5-B ligand, a DR5-specific TRAIL variant, its fast elimination from a body limits its potential use in a clinic. A combination of an antitumor effect of the DR5-B protein with DOX loaded in the capsules could allow to design a novel targeted drug delivery system. The aim of the study was to fabricate PMC loaded with a subtoxic concentration of DOX and functionalized with the DR5-B ligand and to evaluate a combined antitumor effect of this targeted drug delivery system in vitro. In this study, the effects of PMC surface modification with the DR5-B ligand on cell uptake both in 2D (monolayer culture) and 3D (tumor spheroids) were studied by confocal microscopy, flow cytometry and fluorimetry. Cytotoxicity of the capsules was evaluated using an MTT test. The capsules loaded with DOX and modified with DR5-B demonstrated synergistically enhanced cytotoxicity in both in vitro models. Thus, the use of the DR5-B-modified capsules loaded with DOX at a subtoxic concentration could provide both targeted drug delivery and a synergistic antitumor effect.

A new triphenylphosphonium-conjugated amphipathic cationic peptide with improved cell-penetrating and ROS-targeting properties

We study for the first time whether triphenylphosphonium (TPP) moiety can improve cellular delivery and redox properties of amphipathic cationic peptides based on YRFK/YrFK cell-penetrating and cytoprotective motif. TPP moiety was found to increase reducing activity of both stereoisomeric peptides in solution and on electrode surface in association with TPP-mediated intramolecular interactions. Among TPP-conjugated peptides, newly synthesized TPP3-YrFK featured both increased antioxidant efficacy and proteolytic resistance. TPP-conjugated peptides preferably mitigated endogenic ROS in mitochondria and cytoplasm of model glioblastoma cells with increased oxidative status. This anti-ROS effect was accompanied by mild reversible decrease of reduced glutathione level in the cells with relatively weak change in glutathione redox forms ratio. Such low interference with cell redox status is in accordance with non-cytotoxic nature of the compounds. Intracellular concentrations of label-free peptides were analyzed by LC-MS/MS, which showed substantial TPP-promoted penetration of YrFK motif across cell plasma membrane. However, according to ΔΨ_m analysis, TPP moiety did not profoundly enhance peptide interaction with mitochondrial inner membrane. Our study clarifies the role of TPP moiety in cellular delivery of amphipathic cationic oligopeptides. The results suggest TPP moiety as a multi-functional modifier for the oligopeptides which is capable of improving cellular pharmacokinetics and antioxidant activity as well as targeting increased ROS levels. The results encourage further investigation of TPP3-YrFK as a peptide antioxidant with multiple benefits.

DR5-Selective TRAIL Variant DR5-B Functionalized with Tumor-Penetrating iRGD Peptide for Enhanced Antitumor Activity against Glioblastoma

TRAIL (TNF-related apoptosis-inducing ligand) and its derivatives are potentials for anticancer therapy due to the selective induction of apoptosis in tumor cells upon binding to death receptors DR4 or DR5. Previously, we generated a DR5-selective TRAIL mutant variant DR5-B overcoming receptor-dependent resistance of tumor cells to TRAIL. In the current study, we improved the antitumor activity of DR5-B by fusion with a tumor-homing iRGD peptide, which is known to enhance the drug penetration into tumor tissues. The obtained bispecific fusion protein DR5-B-iRGD exhibited dual affinity for DR5 and integrin αvβ3 receptors. DR5-B-iRGD penetrated into U-87 tumor spheroids faster than DR5-B and demonstrated an enhanced antitumor effect in human glioblastoma cell lines T98G and U-87, as well as in primary patient-derived glioblastoma neurospheres in vitro. Additionally, DR5-B-iRGD was highly effective in a xenograft mouse model of the U-87 human glioblastoma cell line in vivo. We suggest that DR5-B-iRGD may become a promising candidate for targeted therapy for glioblastoma.

New Born Calf Serum Can Induce Spheroid Formation in Breast Cancer KAIMRC1 Cell Line

Three-dimensional (3D) cell culture systems have become very popular in the field of drug screening and discovery. There is an immense demand for highly efficient and easy methods to produce 3D spheroids in any cell format. We have developed a novel and easy method to produce spheroids from the newly isolated KAIMRC1 cell line in vitro. It can be used as a 3D model to study proliferation, differentiation, cell death, and drug response of cancer cells. Our procedure requires growth media supplemented with 10% new born calf serum (NBCS) and regular cell culture plates to generate KAIMRC1 spheroids without the need for any specialized 3D cell culture system. This procedure generates multiple spheroids within a 12–24-h culture. KAIMRC1 spheroids are compact, homogeneous in size and morphology with a mean size of 55.8 µm (±3.5). High content imaging (HCI) of KAIMRC1 spheroids treated with a panel of 240 compounds resulted in the identification of several highly specific compounds towards spheroids. Immunophenotyping of KAIMRC1 spheroids revealed phosphorylation of FAK, cJUN, and E-cadherin, which suggests the involvement of JNK/JUN pathway in the KAIMRC1 spheroids formation. Gene expression analysis showed upregulation of cell junction genes, GJB3, DSC1, CLDN5, CLDN8, and PLAU. Furthermore, co-culture of KAIMRC1 cells with primary cancer-associated-fibroblasts (CAFs) showcased the potential of these cells in drug discovery application.

Amphiphilic Poly(N-vinylpyrrolidone) Nanoparticles Conjugated with DR5-Specific Antitumor Cytokine DR5-B for Targeted Delivery to Cancer Cells

Nanoparticles based on the biocompatible amphiphilic poly(N-vinylpyrrolidone) (Amph-PVP) derivatives are promising for drug delivery. Amph-PVPs self-aggregate in aqueous solutions with the formation of micellar nanoscaled structures. Amph-PVP nanoparticles are able to immobilize therapeutic molecules under mild conditions. As is well known, many efforts have been made to exploit the DR5-dependent apoptosis induction for cancer treatment. The aim of the study was to fabricate Amph-PVP-based nanoparticles covalently conjugated with antitumor DR5-specific TRAIL (Tumor necrosis factor-related apoptosis-inducing ligand) variant DR5-B and to evaluate their in vitro cytotoxicity in 3D tumor spheroids. The Amph-PVP nanoparticles were obtained from a 1:1 mixture of unmodified and maleimide-modified polymeric chains, while DR5-B protein was modified by cysteine residue at the N-end for covalent conjugation with Amph-PVP. The nanoparticles were found to enhance cytotoxicity effects compared to those of free DR5-B in both 2D (monolayer culture) and 3D (tumor spheroids) in vitro models. The cytotoxicity of the nanoparticles was investigated in human cell lines, namely breast adenocarcinoma MCF-7 and colorectal carcinomas HCT116 and HT29. Notably, DR5-B conjugation with Amph-PVP nanoparticles sensitized resistant multicellular tumor spheroids from MCF-7 and HT29 cells. Taking into account the nanoparticles loading ability with a wide range of low-molecular-weight antitumor chemotherapeutics into hydrophobic core and feasibility of conjugation with hydrophilic therapeutic molecules by click chemistry, we suggest further development to obtain a versatile system for targeted drug delivery into tumor cells.

Squaramide-Based Supramolecular Materials Drive HepG2 Spheroid Differentiation

A major challenge in the use of HepG2 cell culture models for drug toxicity screening is their lack of maturity in 2D culture. 3D culture in Matrigel promotes the formation of spheroids that express liver-relevant markers, yet they still lack various primary hepatocyte functions. Therefore, alternative matrices where chemical composition and materials properties are controlled to steer maturation of HepG2 spheroids remain desired. Herein, a modular approach is taken based on a fully synthetic and minimalistic supramolecular matrix based on squaramide synthons outfitted with a cell-adhesive peptide, RGD for 3D HepG2 spheroid culture. Co-assemblies of RGD-functionalized squaramide-based and native monomers resulted in soft and self-recovering supramolecular hydrogels with a tunable RGD concentration. HepG2 spheroids are self-assembled and grown (≈150 µm) within the supramolecular hydrogels with high cell viability and differentiation over 21 days of culture. Importantly, significantly higher mRNA and protein expression levels of phase I and II metabolic enzymes, drug transporters, and liver markers are found for the squaramide hydrogels in comparison to Matrigel. Overall, the fully synthetic squaramide hydrogels are proven to be synthetically accessible and effective for HepG2 differentiation showcasing the potential of this supramolecular matrix to rival and replace naturally-derived materials classically used in high-throughput toxicity screening.

Bioactive three-dimensional silk composite in vitro tumoroid model for high throughput screening of anticancer drugs

HYPOTHESIS

Modeling three-dimensional (3D) in vitro culture systems recapitulating spatiotemporal characteristics of native tumor-mass has shown tremendous potential as a pre-clinical tool for drug screening. However, their applications in clinical settings are still limited due to inappropriate recapitulation of tumor topography, culture instability, and poor durability of niche support.

EXPERIMENTS

Here, we have fabricated a bio-active silk composite scaffold assimilating tunable silk from Bombyx mori and - arginine-glycine-aspartate (RGD) rich silk from Antheraea assama to provide a better 3D-matrix for breast (MCF 7) and liver (HepG2) tumoroids. Cellular mechanisms underlying physiological adaptations in 3D constructs and subsequent drug responses were compared with conventional monolayer and multicellular spheroid culture.

FINDINGS

Silk composite matrix assists prolonged growth and high metabolic activity (Cytochrome P450 reductase) in breast and liver 3D-tumoroids. Enhanced stemness expression (Cell surface adhesion receptor; CD44, Aldehyde dehydrogenase 1) and epithelial-mesenchymal-transition markers (E-cadherin, Vimentin) at transcript and protein levels demonstrate that bio-active matrix-assisted 3D environment augmenting metastatic potential in tumoroids. Together, enhanced secretion of Transforming growth factor β (TGFβ), anchorage-independency, and colony-forming potential of cells in the 3D-tumoroids further corroborates the aggressive behavior of cells. Moreover, the multilayered 3D-tumoroids exhibit decreased sensitivity to some known anticancer drugs (Doxorubicin and Paclitaxel). In conclusion, the bio-active silk composite matrix offers an advantage in developing robust and sustainable 3D tumoroids for a high-throughput drug screening platform.

Natural and Synthetic Biomaterials for Engineering Multicellular Tumor Spheroids

The lack of in vitro models that represent the native tumor microenvironment is a significant challenge for cancer research. Two-dimensional (2D) monolayer culture has long been the standard for in vitro cell-based studies. However, differences between 2D culture and the in vivo environment have led to poor translation of cancer research from in vitro to in vivo models, slowing the progress of the field. Recent advances in three-dimensional (3D) culture have improved the ability of in vitro culture to replicate in vivo conditions. Although 3D cultures still cannot achieve the complexity of the in vivo environment, they can still better replicate the cell-cell and cell-matrix interactions of solid tumors. Multicellular tumor spheroids (MCTS) are three-dimensional (3D) clusters of cells with tumor-like features such as oxygen gradients and drug resistance, and represent an important translational tool for cancer research. Accordingly, natural and synthetic polymers, including collagen, hyaluronic acid, Matrigel^®, polyethylene glycol (PEG), alginate and chitosan, have been used to form and study MCTS for improved clinical translatability. This review evaluates the current state of biomaterial-based MCTS formation, including advantages and disadvantages of the different biomaterials and their recent applications to the field of cancer research, with a focus on the past five years.

Fabrication and evaluation of nanocontainers for lipophilic anticancer drug delivery in 3D in vitro model

Presently, most of anticancer drugs are high toxic for normal cells and, and as a result, they have severe side effects. Moreover, most of the formulations are lipophilic and have poor selectivity. To overcome these limitations, various drug delivery systems could be proposed. The aim of the current study was to fabricate novel polysaccharide nanocontainers (NC) by one-step ultrasonication technique and to evaluate their accumulation efficacy and cytotoxicity in 2D (monolayer culture) and 3D (tumor spheroids) in vitro models. NC with mean sizes in a range of 340-420 nm with the core-shell structure are synthetized and characterized. The NC shell is composed from diethylaminoethyl dextran/xanthan gum polyelectrolyte complex, while the hydrophobic core was loaded with the lipophilic anticancer drug thymoquinone. To enhance NC accumulation in human breast adenocarcinoma MCF-7 cells, the NC surface was modified with poly-L-lysine (PLL) or polyethylene glycol. Cell uptake of the NC loaded with Nile Red into the tumor cells was investigated by laser scanning confocal microscopy, fluorescent flow cytometry and fluorimetry. Modification of the NC with PLL allowed to obtain the optimal drug delivery system with maximal cytotoxicity, which was tested by MTT-test. The developed NC are promising for lipophilic anticancer drug delivery.

Effect of RGD content in poly(ethylene glycol)-crosslinked poly(methyl vinyl ether-alt-maleic acid) hydrogels on the expansion of ovarian cancer stem-like cells

The extracellular matrix (ECM) affects cell behaviors, such as survival, proliferation, motility, invasion, and differentiation. The arginine-glycine-aspartic acid (RGD) sequence is present in several ECM proteins, such as fibronectin, collagen type I, fibrinogen, laminin, vitronectin, and osteopontin. It is very critical to develop ECM-like substrates with well-controlled features for the investigation of influence of RGD on the behavior of tumor cells. In this study, poly(ethylene glycol) (PEG)-crosslinked poly(methyl vinyl ether-alt-maleic acid) (P(MVE-alt-MA)) hydrogels (PEMM) with different RGD contents were synthesized, fully characterized, and established as in vitro culture platforms to investigate the effects of RGD content on cancer stem cell (CSC) enrichment. The morphology, proliferation, and viability of SK-OV-3 ovarian cancer cells cultured on hydrogels with different RGD contents, the expression of CSC markers and malignant signaling pathway-related genes, and drug resistance were systematically evaluated. The cell aggregates formed on the hydrogel surface with a lower RGD content acquired certain CSC-like properties, thus drug resistance was enhanced. In contrast, the drug sensitivity of cells on the higher RGD content surface increased because of less CSC-like properties. However, the presence of RGD in the stiff hydrogels (PEMM2) had less effect on the stemness expression than did its presence in the soft hydrogels (PEMM1). The results suggest that RGD content and matrix stiffness can lead to synergetic effects on the expression of cancer cell stemness and the epithelial-mesenchymal transition (EMT), interleukin-6 (IL-6), and Wnt pathways.

Novel bexarotene derivatives: Synthesis and cytotoxicity evaluation for glioma cells in 2D and 3D in vitro models

Glioblastoma (GBM) is an aggressive and lethal form of brain cancer with a high invasion capacity and a lack of effective chemotherapeutics. Retinoid bexarotene (BXR) inhibits the neurospheroidal colony formation and migration of primary glioblastoma cells but has side effects. To enhance the BXR glioblastoma selectivity and cytotoxicity, we chemically modified it at the carboxyl group with either nitroethanolamine (NEA) bearing a NO-donating group (a well-known bioactivity enhancer; BXR-NEA) or with a dopamine (DA) moiety (to represent the highly toxic for various tumor cells N-acyldopamine family; BXR-DA). These two novel compounds were tested in the 2D (monolayer culture) and 3D (multicellular tumor spheroids) in vitro models. Both BXR-DA and BXR-NEA were found to be more toxic for rat C6 and human U-87MG glioma cells than the initial BXR. After 24 h incubation of the cells (monolayer culture) with the drugs, the IC₅₀ values were in the range of 28-42, and 122-152 μM for BXR derivatives and BXR, respectively. The cell death occurred via apoptosis according to the annexin staining and caspase activation. The tumor spheroids demonstrated higher resistance to the treatment compared to that one of the monolayer cultures. BXR-DA and BXR-NEA were more specific against tumor cells than the parental drug, in particular the selectivity index was 1.8-2.7 vs. 1.3-1.5, respectively. Moreover, they inhibited cell migration more effectively than parental BXR according to a scratch assay. Cell spreading from the tumor spheroids was also inhibited. Thus, the obtained BXR derivatives could be promising for glioblastoma treatment.

A Triple Combination of Metformin, Acetylsalicylic Acid, and Oseltamivir Phosphate Impacts Tumour Spheroid Viability and Upends Chemoresistance in Triple-Negative Breast Cancer

Introduction

Targeted multimodal approaches need to be strategically developed to control tumour growth and prevent metastatic burden successfully. Breast cancer presents a unique clinical problem because of the variety of cellular subtypes that arise. The tumour stage and cellular subtypes often dictate the appropriate clinical treatment regimen. Also, the development of chemoresistance is a common clinical challenge with breast cancer. Higher doses and additional drug agents can produce additional adverse effects leading to a more aggressive malignancy. Acetylsalicylic acid (ASA), metformin (Met), and oseltamivir phosphate (OP) were investigated for their efficacy to sensitize MDA-MB-231 triple-negative breast cancer and its tamoxifen (Tmx) resistant variant (MDA-MB-231-TmxR) together in combination with Tmx treatment.

Methods

Microscopic imaging, the formation of 3D multicellular tumour spheroids, immunocytochemistry, flow cytometry, Annexin V Assay, Caspase 3/7 Apoptosis Assay, tube formation assay and analysis, and WST-1 cell viability assay evaluated the formation of MCTS, morphologic changes, cell viability, apoptosis activity and the expression levels of ALDH1A1, CD44 and CD24 on the cell surface, MDA-MB231 triple-negative breast cancer, tamoxifen (Tmx) resistant variant (MDA-MB-231-TmxR).

Results

The results using a triple combination of ASA, Met and OP on MDA-MB-231 and MDA-MB-231-TmxR cells and their matrix-free 3D multicellular tumour spheroids (MCTS) formed by using the cyclic Arg-Gly-Asp-D-Phe-Lys peptide modified with 4-carboxybutyl-triphenylphosphonium bromide (cyclo-RGDfK(TPP)) peptide method demonstrate a consistent and significant decrease in cell and tumour spheroid viability and volume with increased apoptotic activity, and increased sensitivity to Tmx therapy. Tmx treatment of MDA-MB-231 cells in combination with ASA, Met and OP markedly reduced the CD44/CD24 ratio by 6.5-fold compared to the untreated control group. Tmx treatment of MDA-MB-231-TmxR cells in combination with ASA, Met and OP markedly reduced the ALDH1A1 by 134-fold compared to the same treatment for the parental cell line. Also, the triple combination treatment of ASA, Met, and OP inhibited vasculogenic endothelial cell tube formation and induced endothelial cell apoptosis.

Conclusion

For the first time, the findings demonstrate that repurposing ASA, Met, and OP provides a novel and promising targeted multimodal approach in the treatment of triple-negative breast cancer and its chemoresistant variant.

Comparison of the Effect of Platinum (IV) Complexes on Spheroids and Monolayer Culture of HeLa Cells

We performed a comparative study of the cytotoxicity of cisplatin, JM216 complex, and aminonitroxyl platinum(IV) complexes for HeLa cells grown in monolayer and 3D culture. The growth dynamics of spheroids was studied and optimal conditions for evaluation of cytotoxicity were determined. Spheroids were less sensitive to the test compounds than cells in a monolayer. The resistance index (RI) of spheroids was determined as the ratio of IC₅₀ for spheroids to IC₅₀ for monolayer culture. Resistance index was 5.0±1.5 for cisplatin and ranged from 1.8 to 2.3 for platinum(IV) complexes. The observed differences are related to different physicochemical properties of the complexes and different mechanisms of their penetration into cells.

Impact of Fucosylation on Self-Assembly of Prostate and Breast Tumor Spheroids by Using Cyclo-RGDfK(TPP) Peptide and Image Object Detection

Introduction

Core fucosylation of N-glycans on the integrin β1 subunit is essential for the functional activity of the integrin. The binding of α5β1 integrin with the tripeptide Arg-Gly-Asp (RGD) motif within the extracellular matrix protein fibronectin may be influenced by the α-1,6-fucose core or α-1,2-fucose and α-1,3/4-fucose peripheral N-glycan profiles. Here, we investigated whether fucosylation impacts the formation of matrix-free 3D multicellular tumor spheroids (MCTS) from human triple negative breast MDA-MB231 cell line, prostate PC3 and DU145 cell lines and DU145 gemcitabine resistant (GemR) variant by using the cyclic Arg-Gly-Asp-D-Phe-Lys peptide modified with 4-carboxybutyl-triphenylphosphonium bromide (cyclo-RGDfK(TPP)) peptide method.

Methods

Microscopic imaging, lectin histochemistry, flow cytometry, WST-1 cell viability assay and You Only Look Once version 2 (YOLOv2) training object detection using cyclic learning rates were used to evaluate the formation of MCTS, morphologic changes, and the expression levels of α-1,6-fucose and α-1,2-fucose linkages on the cell surface.

Results

DU145 prostate cancer cells expressed higher α-1,6-fucose than α-1,2-fucose linkages on their cell surface, as determined by lectin cytochemistry and flow cytometry. Blockage of the α-1,6- and α-1,2-fucose linkages with Aspergillus oryzae lectin (AOL) and Ulex Europaeus agglutinin I (UEA I) one hour before the addition of cyclic-RGDfK(TPP) peptide to the monolayer of the cancer cells resulted in a statistically significant dose-dependent reduction in spheroid volumes using threshold diameters of 40 and 60 µm. Application of a 40 µm threshold diameter measurements of spheroids resulted in fewer false-positive ones compared to the 60 µm diameter threshold previously used in our studies. A state-of-the-art, image object detection system YOLOv2 was used to automate the analysis of spheroid measurements and volumes. The results showed that YOLOv2 corroborated manual spheroid detection and volume measurements with high precision and accuracy.

Conclusion

For the first time, the findings demonstrate that α-1,6- and α-1,2-fucose linkages of N-glycans on the cell surface receptors facilitate cyclo-RGDfK(TPP)-mediated self-assembly of cancer cells to form 3D multicellular tumor spheroids.

Characterization of the metastatic potential of the floating cell component of MIA PaCa-2, a human pancreatic cancer cell line

In pancreatic cancer, morphologically and functionally heterogeneous cancer cells reside within the same patient. The heterogeneity is believed to promote metastasis and resistance to chemoradiotherapy. MIA PaCa-2, an established human pancreatic ductal adenocarcinoma (PDAC) cell line, contains round and spindle-shaped adherent cells, as well as, round floating cells. In this study, we aimed to assess if the floating cells might have greater metastatic potential and/or be more resistant to drug-induced apoptosis compared to adherent cells. Time-lapse analysis revealed that the two types of adherent cells transformed bilaterally, and some of the adherent, round cells converted to floating cells. Flow cytometry and electron microscopy showed that approximately 90% of the floating cells were viable. qRT-PCR analysis revealed that floating cells expressed lower levels of integrins and ATP-binding cassette (ABC) transporters than adherent cells. In contrast, except for vimentin, floating cells expressed more epithelial to mesenchymal transition markers than adherent cells. Floating cells included a larger population of G2/M-phase cells, and migration assays revealed a decreased migration ability by floating cells relative to adherent cells. A cell aggregation assay showed that the aggregative properties of the floating cells were lower than those of the adherent cells. In 3D culture, spheres derived from floating cells were more sensitive to anti-cancer drugs, including gemcitabine, 5-FU, and abraxane, than those derived from adherent cells. Expression levels of stemness markers in the spheres derived from floating cells were lower than those derived from adherent cells. Morphological characterization of human PDAC cell lines may help to clarify the series of alterations cancer cells undergo during the metastatic process and may contribute to the development of new PDAC diagnostics and more patient-specific treatments for those with PDAC.

The study of establishment of an in vivo tumor model by three-dimensional cells culture systems methods and evaluation of antitumor effect of biotin-conjugated pullulan acetate nanoparticles

In this study, three-dimensional (3D) hydrogels were used for human hepatocellular carcinoma (HepG2) cells culture systems in vitro and establishment of an in vivo xenografted tumor model. Based on our previous work on the biotin-conjugated pullulan acetate nanoparticles (Bio-PA NPs) as anticancer drug carriers, we further studied the anti-tumor effect of the NPs in two-dimensional (2D) and 3D cell culture system. When embedded in 3D hydrogels, HepG2 cells formed tumor spheroids and the cytoplasmic actin microfilamentrates were rearranged over a period of 7 days. In vitro cytotoxicity results indicated that HepG2 cells in 3D hydrogels were more resistant to Bio-PA NPs treatments compared to the 2D system. The tumor formation rate of in vivo xenografted tumor model using 3D culture systems method was 98.2%, which was significantly higher than that using of 2D cultured cells (76.4%). Then we injected the 3D HepG2 cells systems in the right anterior axillary of female Balb/c nude mice, and evaluate the in vivo anti-tumor efficacy of Bio-PA NPs. In summary, these results suggested that HepG2 cells in 3D hydrogel system has shown the potential to provide an in vitro and in vivo model and for the evaluation of Bio-PA NPs.

Lipoamino acid-based cerasomes for doxorubicin delivery: Preparation and in vitro evaluation

Cerasomes are hybrid organic-inorganic nanoparticles (NPs) that could be considered as liposomes with rather durable silicon shell. In this study, several cerasome-forming lipoamino acids (CFLA) were synthesized and used as structural blocks for cerasome preparation. Pure cerasomes which contained only CFLA, and mixed cerasomes based on a mixture of CFLA with a disintegrating dipalmitoylphosphatidylcholine (DPPC) lipid were fabricated and characterized in terms of morphology, mean size, ζ-potential, stability at storage. All obtained cerasome samples were found to be much more stable at storage than conventional liposomes (120 and 10 days, respectively). The cerasomes were loaded with doxorubicin (DOX) and tested in vitro using human breast adenocarcinoma MCF-7. Effects of the lipid composition on the physical-chemical properties and cellular uptake of the cerasomes both in 2D (monolayer culture) and 3D (multicellular tumor spheroids) were studied. The biggest accumulation efficiencies as well as the highest cytotoxicity level were found for the mixed cationic cerasomes. These cerasomes could be proposed as promising drug delivery system for cancer treatment.

Metformin increases antitumor activity of MEK inhibitor binimetinib in 2D and 3D models of human metastatic melanoma cells

Melanoma is one of the most aggressive and treatment-resistant tumors that responsible for majority of skin-cancer related deaths. Here we propose a combination of MEK inhibitor binimetinib with metformin as a promising therapy against human melanoma cells in vitro, including BRAF -mutated A375, Mel Z, and Mel IL cells, and NRAS-mutated Mel MTP and Mel Me cells. Additionally, we obtained two close to clinical practice models of melanoma progression. The first one was vemurafenib-resistant Mel IL/R melanoma cells with acquired resistance to BRAF inhibition-targeted therapy, and the second one was tumor spheroids, which are 3D in vitro model of small-size solid tumors in vivo. The cytotoxicity of binimetinib and metformin was synergistic in both 2D and 3D melanoma culture and mediated through apoptotic pathway. The combination reduced the number of melanoma-formed colonies, inhibited cell invasion and migration, and led to G0/G1 cell cycle arrest through cyclin D/CDK4/CDK6 pathway. The mechanism of metformin and binimetinib synergy in melanoma cells was associated with increased activation of p-AMPKα and decreased p-ERK, but not with alterations in p-mTOR. In summary, the combination of metformin and binimetinib resulted in stronger anti-proliferative effects on melanoma cells compared to binimetinib alone, and therefore could be promising for clinical applications.

Adaptive Multifunctional Supramolecular Assemblies of Glycopeptides Rapidly Enable Morphogenesis

Despite the well-established biophysical principle of adhesion-guided in vitro morphogenesis, there are few single synthetic molecular species that can rapidly enable morphogenesis (e.g., a cell monolayer to cell spheroids) in a cell culture because adhesion inherently involves many signals. Here we show the use of adaptive multifunctional supramolecular assemblies of glycopeptides, consisting of cell adhesion sequence and saccharide, to induce cell spheroids rapidly from a monolayer of cells. Having a general architecture of N-terminal capping, glycosylation, and an integrin-binding sequence, the glycopeptides self-assemble to form a dynamic continuum of nanostructures (i.e., from nanoparticles to nanofibers) to affect the interactions of integrins, E-selectin, and cadherins with their natural ligands and to act adaptively according to the cellular environment. Such adaptive (i.e., context-dependent) interactions weaken cell-substratum adhesion and enhance intercellular interactions, which rapidly and transiently induce cell spheroids. This work illustrates the use of supramolecular assemblies of simple glycopeptides to modulate biophysical conditions for regulating cell functions, which is a new approach for developing biomaterials.

Functionalized Folic Acid-Conjugated Amphiphilic Alternating Copolymer Actively Targets 3D Multicellular Tumour Spheroids and Delivers the Hydrophobic Drug to the Inner Core

Engineering of a “smart” drug delivery system to specifically target tumour cells has been at the forefront of cancer research, having been engineered for safer, more efficient and effective use of chemotherapy for the treatment of cancer. However, selective targeting and choosing the right cancer surface biomarker are critical for a targeted treatment to work. Currently, the available delivery systems use a two-dimensional monolayer of cancer cells to test the efficacy of the drug delivery system, but designing a “smart” drug delivery system to be specific for a tumour in vivo and to penetrate the inner core remains a major design challenge. These challenges can be overcome by using a study model that integrates the three-dimensional aspect of a tumour in a culture system. Here, we tested the efficacy of a functionalized folic acid-conjugated amphiphilic alternating copolymer poly(styrene-alt-maleic anhydride) (FA-DABA-SMA) via a biodegradable linker 2,4-diaminobutyric acid (DABA) to specifically target and penetrate the inner core of three-dimensional avascular human pancreatic and breast tumour spheroids in culture. The copolymer was quantitatively analyzed for its hydrophobic drug encapsulation efficiency using three different chemical drug structures with different molecular weights. Their release profiles and tumour targeting properties at various concentrations and pH environments were also characterized. Using the anticancer drug curcumin and two standard clinical chemotherapeutic hydrophobic drugs, paclitaxel and 5-fluorouracil, we tested the ability of FA-DABA-SMA nanoparticles to encapsulate the differently sized drugs and deliver them to kill monolayer pancreatic cancer cells using the WST-1 cell proliferation assay. The findings of this study revealed that the functionalized folic acid-conjugated amphiphilic alternating copolymer shows unique properties as an active “smart” tumor-targeting drug delivery system with the ability to internalize hydrophobic drugs and release the chemotherapeutics for effective killing of cancer cells. The novelty of the study is the first to demonstrate a functionalized “smart” drug delivery system encapsulated with a hydrophobic drug effectively targeting and penetrating the inner core of pancreatic and breast cancer spheroids and reducing their volumes in a dose- and time-dependent manner.

Bioprintable Alginate/Gelatin Hydrogel 3D In Vitro Model Systems Induce Cell Spheroid Formation

The cellular, biochemical, and biophysical heterogeneity of the native tumor microenvironment is not recapitulated by growing immortalized cancer cell lines using conventional two-dimensional (2D) cell culture. These challenges can be overcome by using bioprinting techniques to build heterogeneous three-dimensional (3D) tumor models whereby different types of cells are embedded. Alginate and gelatin are two of the most common biomaterials employed in bioprinting due to their biocompatibility, biomimicry, and mechanical properties. By combining the two polymers, we achieved a bioprintable composite hydrogel with similarities to the microscopic architecture of a native tumor stroma. We studied the printability of the composite hydrogel via rheology and obtained the optimal printing window. Breast cancer cells and fibroblasts were embedded in the hydrogels and printed to form a 3D model mimicking the in vivo microenvironment. The bioprinted heterogeneous model achieves a high viability for long-term cell culture (> 30 days) and promotes the self-assembly of breast cancer cells into multicellular tumor spheroids (MCTS). We observed the migration and interaction of the cancer-associated fibroblast cells (CAFs) with the MCTS in this model. By using bioprinted cell culture platforms as co-culture systems, it offers a unique tool to study the dependence of tumorigenesis on the stroma composition. This technique features a high-throughput, low cost, and high reproducibility, and it can also provide an alternative model to conventional cell monolayer cultures and animal tumor models to study cancer biology.

Redox-Active Quinone Chelators: Properties, Mechanisms of Action, Cell Delivery, and Cell Toxicity

SIGNIFICANCE

Chemotherapy is currently the principal method for treating many malignancies. Thus, the development of improved antitumor drugs with enhanced efficacy and selectivity remains a high priority. Recent Advances: Anthracycline antibiotics (AAs), for example, doxorubicin, daunomycin, and mitomycin C, belong to an important family of antitumor agents widely used in chemotherapy. These compounds are all quinones. They are, thus, capable of being reduced by appropriate chemicals or reductases. One of their important properties is that under aerobic conditions their reduced forms undergo oxidation, with concomitant generation of reactive oxygen species (ROS), namely, superoxide anion radicals, hydrogen peroxide, and hydroxyl radicals. The presence of metal ions is essential for the generation of ROS by AAs in biological systems.

CRITICAL ISSUES

A fundamental shortcoming of the AAs is their high cardiotoxicity. We have proposed, and experimentally realized, a new type of quinones that is capable of coordinating metal ions. We have demonstrated in vitro that they can be reduced by electron transfer chains and glutathione with concomitant generation of ROS. They can also produce ROS under photo-excitation. The mechanisms of these reactions have been characterized by using nuclear magnetic resonance and electron paramagnetic resonance.

FUTURE DIRECTIONS

To enhance their therapeutic effectiveness, and decrease cardiotoxicity and other side effects, we intend to conjugate the quinone chelators with monoclonal antibodies and peptide hormones that are specifically targeted to receptors on the cancer cell surface. Some such candidates have already been synthesized. An alternative approach for delivery of our compounds involves the use of specific peptide-based nanoparticles. In addition, our novel approach for treating malignancies is also suitable for photodynamic therapy. Antioxid. Redox Signal. 28, 1394-1403.

Sialylation transmogrifies human breast and pancreatic cancer cells into 3D multicellular tumor spheroids using cyclic RGD-peptide induced self-assembly

Multicellular tumor spheroids (MTS) have been at the forefront of cancer research, designed to mimic tumor-like developmental patterns in vitro. Tumor growth in vivo is highly influenced by aberrant cell surface-specific sialoglycan structures on glycoproteins. Aberrant sialoglycan patterns that facilitate MTS formation are not well defined. Matrix-free spheroids from breast MCF-7 and pancreatic PANC1 cancer cell lines and their respective tamoxifen (TMX) and gemcitabine (Gem) resistant variants were generated using the RGD platform of cyclic Arg-Gly-Asp-D-Phe-Lys peptide modified with 4-carboxybutyl-triphenylphosphonium bromide (cyclo-RGDfK (TPP)). MCF-7 and MCF-7 TMX cells formed tight spheroids both in the classical agarose-and RGD-based platforms while all PANC1 cells formed loose aggregates. Using lectin histochemistry staining, sialidase assay, neuraminidase (Vibrio cholerae) and oseltamivir phosphate (OP) neuraminidase inhibitor treatments, MCF-7 and PANC1 cells and their drug-resistant variants expressed different sialic acid (SA) content on their cell surfaces. α-2,3- and α-2,6-sialic acid surface residues facilitated spheroid formation under cyclo-RGDfK(TPP)-induced self-assembly. Pretreatment with α-2,3- SA specific Maackia amurensis (MAL-II) lectin, α-2,6-SA specific Sambucus nigra (SNA) lectin, and exogenous α-2,6-SA specific neuraminidase (Vibrio cholerae) dose-dependently reduced spheroid volume. OP enhanced cell aggregation and compaction forming spheroids. PANC1 and MDA-MB231 xenograft tumors from untreated and OP-treated RAGxCγ double mutant mice expressed significantly higher levels of α-2,3- SA over α-2,6-SA. MCF-7 spheroids also expressed a high α-2,3-SA to α-2,6-SA ratio. These results suggest that the relative levels of specific sialoglycan structures on the cell surface correlate with the ability of cancer cells to form avascular multicellular tumor spheroids and in vivo xenograft tumors.

EGFR/EGFRvIII Dual-Targeting Peptide-Mediated Drug Delivery for Enhanced Glioma Therapy

Tumor-homing peptides have been widely used to mediate active targeted drug delivery. l-AE is a reported targeting peptide demonstrating high binding affinity to epidermal growth factor receptor (EGFR) and mutation variant III (EGFRvIII) overexpressed on neovasculature, vasculogenic mimicry, tumor cells, and tumor stem cells. To improve its proteolytic stability, a d-peptide ligand (termed d-AE, the enantiomer of l-AE) was developed. d-AE was confirmed to bind receptors EGFR and EGFRvIII with targeting capability comparable to l-AE. In vivo biodistribution demonstrated the superiority of d-AE in prolonged circulation and enhanced intratumoral accumulation. Furthermore, stabilized peptide modification endowed micelles higher transcytosis efficiency and penetrating capability on blood-brain tumor barrier/U87 tumor spheroids coculture model. When paclitaxel (PTX) was loaded, d-AE-micelle/PTX demonstrated excellent antitumor effect in comparison to Taxol, micelle/PTX, and l-AE-micelle/PTX. These findings indicated that the multitargeted drug delivery system enabled by d-AE ligand provides a promising way for glioma therapy.

Directing the Self-assembly of Tumour Spheroids by Bioprinting Cellular Heterogeneous Models within Alginate/Gelatin Hydrogels

Human tumour progression is a dynamic process involving diverse biological and biochemical events such as genetic mutation and selection in addition to physical, chemical, and mechanical events occurring between cells and the tumour microenvironment. Using 3D bioprinting we have developed a method to embed MDA-MB-231 triple negative breast cancer cells, and IMR-90 fibroblast cells, within a cross-linked alginate/gelatin matrix at specific initial locations relative to each other. After 7 days of co-culture the MDA-MB-231 cells begin to form multicellular tumour spheroids (MCTS) that increase in size and frequency over time. After ~15 days the IMR-90 stromal fibroblast cells migrate through a non-cellularized region of the hydrogel matrix and infiltrate the MDA-MB-231 spheroids creating mixed MDA-MB-231/IMR-90 MCTS. This study provides a proof-of-concept that biomimetic in vitro tissue co-culture models bioprinted with both breast cancer cells and fibroblasts will result in MCTS that can be maintained for durations of several weeks.

Sialylation facilitates self-assembly of 3D multicellular prostaspheres by using cyclo-RGDfK(TPP) peptide

Background

Prostaspheres-based three dimensional (3D) culture models have provided insight into prostate cancer (PCa) biology, highlighting the importance of cell–cell interactions and the extracellular matrix (EMC) in the tumor microenvironment. Although these 3D classical spheroid platforms provide a significant advance over 2D models mimicking in vivo tumors, the limitations involve no control of assembly and structure with only limited spatial or glandular organization. Here, matrix-free prostaspheres from human metastatic prostate carcinoma PC3 and DU145 cell lines and their respective gemcitabine resistant (GemR) variants were generated by using cyclic Arg-Gly-Asp-D-Phe-Lys peptide modified with 4-carboxybutyl-triphenylphosphonium bromide (cyclo-RGDfK(TPP)).

Materials and methods

Microscopic imaging, immunocytochemistry (ICC), flow cytometry, sialidase, and WST-1 cell viability assays were used to evaluate the formation of multicellular tumor spheroid (MCTS), cell survival, morphologic changes, and expression levels of α2,6 and α2,3 sialic acid (SA) and E- and N-cadherin in DU145, PC3, and their GemR variants.

Results

By using the cyclo-RGDfK(TPP) peptide platform in a dose- and time-dependent manner, both DU145 and DU145GemR cells formed small MCTS. In contrast, PC3 and PC3GemR cells formed irregular multicellular aggregates at all concentrations of cyclo-RGDfK(TPP) peptide, even after 6 days of incubation. ICC and flow cytometry results revealed that DU145 cells expressed higher amounts of E-cadherin but lower N-cadherin compared with PC3 cells. By using Maackia amurensis (α2,3-SA-specific MAL-II) and Sambucus nigra (α2,6-SA specific SNA) lectin-based cytochemistry staining and flow cytometry, it was found that DU145 and DU145GemR cells expressed 5 times more α2,6-SA than α2,3-SA on the cell surface. PC3 cells expressed 4 times more α2,3-SA than α2,6-SA, and the PC3GemR cells showed 1.4 times higher α2,6-SA than α2,3-SA. MCTS volume was dose-dependently reduced following pretreatment with α2,6-SA-specific neuraminidase (Vibrio cholerae). Oseltamivir phosphate enhanced cell aggregation and compaction of 3D MCTS formed with PC3 cells.

Conclusion

The relative levels of specific sialoglycan structures on the cell surface correlate with the ability of PCa cells to form avascular multicellular prostaspheres.

Alternative therapies for metastatic breast cancer: multimodal approach targeting tumor cell heterogeneity

One of the primary challenges in developing effective therapies for malignant tumors is the specific targeting of a heterogeneous cancer cell population within the tumor. The cancerous tumor is made up of a variety of distinct cells with specialized receptors and proteins that could potentially be viable targets for drugs. In addition, the diverse signals from the local microenvironment may also contribute to the induction of tumor growth and metastasis. Collectively, these factors must be strategically studied and targeted in order to develop an effective treatment protocol. Targeted multimodal approaches need to be strategically studied in order to develop a treatment protocol that is successful in controlling tumor growth and preventing metastatic burden. Breast cancer, in particular, presents a unique problem because of the variety of subtypes of cancer that can arise and the multiple drug targets that could be exploited. For example, the tumor stage and subtypes often dictate the appropriate treatment regimen. Alternate multimodal therapies should consider the importance of time-dependent drug administration, as well as targeting the local and systemic tumor environment. Many reviews and papers have briefly touched on the clinical implications of this cellular heterogeneity; however, there has been very little discussion on the development of study models that reflect this diversity and on multimodal therapies that could target these subpopulations. Here, we summarize the current understanding of the origins of intratumoral heterogeneity in breast cancer subtypes, and its implications for tumor progression, metastatic potential, and treatment regimens. We also discuss the advantages and disadvantages of utilizing specific breast cancer models for research, including in vitro monolayer systems and three-dimensional mammospheres, as well as in vivo murine models that may have the capacity to encompass this heterogeneity. Lastly, we summarize some of the current advancements in the development of multitarget therapeutics that have shown promising results in clinical and preclinical studies when used alone or in combination with traditional regimens of surgery, chemotherapy, and/or radiation.