A reliable tool to determine cell viability in complex 3-d culture: the acid phosphatase assay

High-throughput three-dimensional spheroid tumor model using a novel stamp-like tool

Spheroid culture is a widely used three-dimensional culture technology that simulates the three-dimensional structure of tumors in vivo and has been considered a good model for tumor research. However, current commercialized spheroid culture tools have the shortcomings of high cost or relatively poor spheroid-forming results for some special cells. To solve such problems, we designed a 3D printed, reusable, stamp-like resin mold that could shape microstructures for spheroid culture of tumor cells on the surface of agarose substrate in a 96-well plate. We applied this homemade three-dimensional culture tool in spheroid formation for hepatocellular carcinoma cells. The experimental data show that the effect of spheroid culture on four hepatocellular carcinoma cell lines in our homemade spheroid culture plate is better than that of the commercialized ultralow attachment spheroid culture plate, and compared to two-dimensional culture, three-dimensional culture improves cell functions. In addition, the drug-sensitive test based on patient-derived hepatocellular carcinoma cells showed a different pattern between spheroid and two-dimensional cultures. In conclusion, our spheroid culture tool is characterized by its low cost, reusability, low cell consumption, convenience in medium exchange, and good effect of spheroid formation, suggesting that this technique could be widely used in individual treatment and high-throughput drug screening.

6-Methoxyquinoline complexes as lung carcinoma agents: induction of oxidative damage on A549 monolayer and multicellular spheroid model

The aim of this work was to study the antitumor effects and the mechanisms of toxic action of a series of 6-methoxyquinoline (6MQ) complexes in vitro. The Cu(II) and Zn(II) complexes (Cu6MQ and Zn6MQ) are formulated as M(6MQ)₂Cl₂; the Co(II) and Ag(I) compounds (Co6MQ and Ag6MQ) are ionic with formulae [Ag(6MQ)₂]⁺NO₃^- and H(6MQ)⁺[Co(6MQ)Cl₃]^- (where H(6MQ)⁺ is the protonated ligand). We found that the copper complex, outperformed the Co(II), Zn(II) and Ag(I) complexes with a lower IC₅₀ (57.9 µM) in A549 cells exposed for 24 h. Cu6MQ decreased cell proliferation and induced oxidative stress detected with H₂DCFDA at 40 µM, which reduces GSH/GSSG ratio. This redox imbalance induced oxidative DNA damage revealed by the Micronucleus test and the Comet assay, which turned into a cell cycle arrest at G2/M phase and induced apoptosis. In multicellular spheroids, the IC₅₀ values tripled the monolayer model (187.3 µM for 24 h). At this concentration, the proportion of live/dead cells diminished, and the spheroids could not proliferate or invade. Although Zn6MQ also decreased GSH/GSSG ratio from 200 µM and the cytotoxicity is related to oxidative stress, the induction of the hydrogen peroxide levels only doubled the control value. Zn6MQ induced S phase arrest, which relates with the increased micronucleus frequency and with the induction of necrosis. Finally, our results reveal a synergistic activity with a 1:1 ratio of both complexes in the monolayer and multicellular spheroids.

Amphiphilic polymer coated nanodiamonds: a promising platform to deliver azonafide

An amphiphilic polymer is grafted on nanodiamonds to improve the colloidal stability and to deliver an anticancer drug azonafide.

Microneedle-Assisted Topical Delivery of Photodynamically Active Mesoporous Formulation for Combination Therapy of Deep-Seated Melanoma

Topical treatment using photodynamic therapy (PDT) for many types of skin cancers has largely been limited by the inability of existing photosensitizers to penetrate into the deep skin tissue. To overcome these problems, we developed a mesoporous nanovehicle with dual loading of photosensitizers and clinically relevant drugs for combination therapy, while utilizing microneedle technology to facilitate their penetration into deep skin tissue. Sub-50 nm photodynamically active mesoporous organosilica nanoparticles were synthesized with photosensitizers covalently bonded to the silica matrix, which dramatically increased the quantum yield and photostability of these photosensitizers. The mesopores of the nanoparticles were further loaded with small-molecule inhibitors, i. e., dabrafenib and trametinib, that target the hyperactive mitogen-activated protein kinase (MAPK) pathway for melanoma treatment. As-prepared empty nanovehicle was cytocompatible with normal skin cells in the dark, while NIR-irradiated drug-loaded nanovehicle showed a synergistic killing effect on skin cancer cells mainly through reactive oxygen species and caspase-activated apoptosis. The nanovehicle could significantly inhibit the proliferation of tumor cells in a 3D spheroid model in vitro. Porcine skin fluorescence imaging demonstrated that microneedles could facilitate the penetration of nanovehicle across the epidermis layer of skin to reach deep-seated melanoma sites. Tumor regression studies in a xenografted melanoma mouse model confirmed superior therapeutic efficacy of the nanovehicle through combinational PDT and targeted therapy.

Induction of apoptosis by essential oil from P. missionis in skin epidermoid cancer cells

BACKGROUND

The genus Pamburus (Rutaceae) comprises the only species, Pamburus missionis (Wight) Swingle. Pamburus missionis is traditionally used in the treatment of swellings, chronic rheumatism, paralysis and puerperal diseases.

PURPOSE

The present study investigates the cancer chemotherapeutic potential of essential oil (EO) from P. missionis.

METHODS

EO was isolated by steam distillation and chemical composition was determined by GC-MS. Cell viability was used to detect cytotoxic activity. Mechanism of cell death was studied using Annexin V-FITC/PI binding, cell cycle analysis, measurement of MMP and ROS generation by flow cytometry. Expression of apoptosis related proteins was investigated by western blot.

RESULTS

GC-MS analysis of the essential oil revealed the presence of 51 components. The major components were β-Caryophyllene, 4(14),11-Eudesmadiene, Aromadendrene oxide-(2) and Phytol. EO inhibited the growth and colony formation ability of A431 and HaCaT cells. EO treatment induced nuclear condensation and loss of membrane integrity, DNA fragmentation, increase in sub-G1 DNA content and increase in intracellular ROS level. Inhibition of intracellular ROS by ascorbic acid and N-acetyl cysteine treatment blocked EO induced apoptosis, revealing that apoptotic activity was by ROS accumulation. EO induced apoptosis was found to be due to the loss of mitochondrial membrane potential (ΔΨm), increase in Bax/Bcl-2 ratio, release of cytochrome c and activation of caspases (cleaved form of caspase-3, caspase-8, caspase-9) and by PARP cleavage.

CONCLUSION

The present study revealed cancer chemotherapeutic potential of EO from P. missionis. EO induces cell death through intrinsic (mitochondrial) and extrinsic apoptotic pathway in A431 and HaCaT cells. These results suggest that EO could be used as a potential therapeutic agent for the treatment of skin epidermoid cancer.

Three Dimensional Mixed-Cell Spheroids Mimic Stroma-Mediated Chemoresistance and Invasive Migration in hepatocellular carcinoma

Interactions between cancer cells and cancer-associated fibroblasts (CAFs) within the tumor microenvironment (TME) play an important role in promoting the profibrotic microenvironment and epithelial-mesenchymal transition (EMT), resulting in tumor progression and drug resistance in hepatocellular carcinoma (HCC). In the present study, we developed a mixed-cell spheroid model using Huh-7 HCC cells and LX-2 stellate cells to simulate the in vivo tumor environment with respect to tumor-CAF interactions. Spheroids were cultured from cancer cells alone (monospheroids) or as a mixture (mixed-cell spheroids) in ultra-low-attachment plates. Compact, well-mixed, and stroma-rich mixed-cell spheroids were successfully established with heterotypic cell-cell contacts shown by the presence of gap junctions and desmosomes. Mixed-cell spheroids showed enhanced expression of collagen type-I (Col‐I) and pro‐fibrotic factors such as, transforming growth factor beta1 (TGF-β1), and connective tissue growth factor (CTGF) compared to the levels expressed in mono-spheroids. The EMT phenotype was evident in mixed-cell spheroids as shown by the altered expression of E-cadherin and vimentin. Differential drug sensitivity was observed in mixed-cell spheroids, and only sorafenib and oxaliplatin showed dose-dependent antiproliferative effects. Simultaneous treatment with TGF-β inhibitors further improved sorafenib efficacy in the mixed-cell spheroids, indicating the involvement of TGF-β in the mechanism of sorafenib resistance. In 3D matrix invasion assay, mixed-cell spheroids exhibited fibroblast-led collective cell movement. Overall, our results provide evidence that mixed-cell spheroids formed with Huh-7 and LX-2 cells well represent HCC tumors and their TME in vivo and hence are useful in studying tumor-stroma interactions as mechanisms associated with drug resistance and increased cell motility.

Spheroid culture enhances osteogenic potential of periodontal ligament mesenchymal stem cells

OBJECTIVE AND BACKGROUND

Human periodontal ligament mesenchymal stem cells (hPDLMSCs) are reported to be responsible for homeostasis and regeneration of periodontal tissue. Although hPDLMSCs are commonly cultured in monolayers, monolayer cultures have been reported as inferior to 3-dimensional cultures such as spheroids, which are spherical clusters of cells formed by self-assembly. The aim of this study was to examine the osteogenic phenotype of spheroids of hPDLMSCs, compared with monolayer cultures of hPDLMSC, in vitro and in vivo.

MATERIAL AND METHODS

Spheroids were formed using microwell chips that were tagged with polyethylene glycol. Mesenchymal stem cell (MSC) markers in hPDLMSC spheroids were examined by flow cytometer. Real-time polymerase chain reaction analysis was examined to measure the expressions of stemness markers and osteogenesis-related genes in monolayer and spheroid-cultured hPDLMSCs. Immunofluorescence analysis was performed to confirm protein expressions of stemness markers in PDLMSC spheroids. Nodule formation assay, alkaline phosphatase (ALP) activity assay and transplantation assay in a mouse calvarial defect model were performed to confirm the osteogenic potential of hPDLMSC spheroids. To elucidate the mechanism of spheroid culture enhanced osteogenesis in hPDLMSCs with osteoinductive medium (OIM), a small interfering RNA (siRNA) assay targeted with secreted frizzled-related protein 3 (SFRP3) was examined. The levels of SFRP3 expression in monolayer and spheroid-cultured hPDLMSCs with OIM were measured by real-time polymerase chain reaction and western blotting analysis. ALP gene expression and ALP activity were examined in SFRP3-deficient hPDLMSC spheroids.

RESULTS

The hPDLMSC spheroids expressed MSC markers, which were similar to hPDLMSCs grown in monolayer cultures. Intriguingly, the protein and mRNA expressions of transcription factors that regulate "stemness" were significantly increased in hPDLMSC spheroids, compared with hPDLMSCs in monolayer cultures. Nodule formation by hPDLMSCs was significantly increased in spheroid cultures grown with OIM, compared with monolayer-cultured hPDLMSCs. ALP activity and expression of osteogenesis-related genes were also significantly enhanced in hPDLMSC spheroids, compared with monolayer cultures. Treatment with hPDLMSC spheroids significantly enhanced new bone formation in a murine calvarial defect model, compared with hPDLMSCs in monolayer culture. Finally, to elucidate mechanisms by which spheroid culture enhances ALP activation in hPDLMSCs grown with OIM, an siRNA assay was used to manipulate expression of SFRP3, a Wnt signaling antagonist. Knockdown of SFRP3 suppressed ALP gene expression in hPDLMSCs grown in OIM; further, it suppressed ALP activity in spheroid culture. These data suggest that the enhancement of osteogenic potential in hPDLMSC spheroids is regulated through SFRP3-mediated ALP activation.

CONCLUSION

Spheroid cultures of hPDLMSCs may be a novel and useful tool in regenerative medicine.

Hemidesmus indicus induces immunogenic death in human colorectal cancer cells

The ability of anticancer treatments to promote the activation of tumor-reactive adaptive immune responses is emerging as a critical requirement underlying their clinical effectiveness. We investigated the ability of Hemidesmus indicus, a promising anticancer botanical drug, to stimulate immunogenic cell death in a human colorectal cancer cell line (DLD1). Here we show that Hemidesmus treatment induces tumor cell cytotoxicity characterized by surface expression of calreticulin, increased HSP70 expression and release of ATP and HMGB1. Remarkably, the exposure to released ICD-inducer factors from Hemidesmus-treated DLD1 cells caused a modest induction of CD14-derived dendritic cells maturation, as demonstrated by the increased expression of CD83. Moreover, at sub-toxic concentrations, H.i. treatment of monocytes and dendritic cells induced their mild activation, suggesting its additional direct immunostimulatory activity. These data indicate that Hemidesmus indicus induces immunogenic cell death in human tumor cells and suggest its potential relevance in innovative cancer immunotherapy protocols.

Facile Tumor Spheroids Formation in Large Quantity with Controllable Size and High Uniformity

A facile method for generation of tumor spheroids in large quantity with controllable size and high uniformity is presented. HCT-116 cells are used as a model cell line. Individual tumor cells are sparsely seeded onto petri-dishes. After a few days of growth, separated cellular islets are formed and then detached by dispase while maintaining their sheet shape. These detached cell sheets are transferred to dispase-doped media under orbital shaking conditions. Assisted by the shear flow under shaking and inhibition of cell-to-extracellular matrix junctions by dispase, the cell sheets curl up and eventually tumor spheroids are formed. The average size of the spheroids can be controlled by tuning the cell sheet culturing period and spheroid shaking period. The uniformity can be controlled by a set of sieves which were home-made using stainless steel meshes. Since this method is based on simple petri-dish cell culturing and shaking, it is rather facile for forming tumor spheroids with no theoretical quantity limit. This method has been used to form HeLa, A431 and U87 MG tumor spheroids and application of the formed tumor spheroids in drug screening is also demonstrated. The viability, 3D structure, and necrosis of the spheroids are characterized.

Macrophage-mediated delivery of light activated nitric oxide prodrugs with spatial, temporal and concentration control

Nitric oxide (NO) holds great promise as a treatment for cancer hypoxia, if its concentration and localization can be precisely controlled. Here, we report a "Trojan Horse" strategy to provide the necessary spatial, temporal, and dosage control of such drug-delivery therapies at targeted tissues. Described is a unique package consisting of (1) a manganese-nitrosyl complex, which is a photoactivated NO-releasing moiety (photoNORM), plus Nd3+-doped upconverting nanoparticles (Nd-UCNPs) incorporated into (2) biodegradable polymer microparticles that are taken up by (3) bone-marrow derived murine macrophages. Both the photoNORM [Mn(NO)dpaqNO2 ]BPh4(dpaqNO2 = 2-[N,N-bis(pyridin-2-yl-methyl)]-amino-N'-5-nitro-quinolin-8-yl-acetamido) and the Nd-UCNPs are activated by tissue-penetrating near-infrared (NIR) light at ∼800 nm. Thus, simultaneous therapeutic NO delivery and photoluminescence (PL) imaging can be achieved with a NIR diode laser source. The loaded microparticles are non-toxic to their macrophage hosts in the absence of light. The microparticle-carrying macrophages deeply penetrate into NIH-3T3/4T1 tumor spheroid models, and when the infiltrated spheroids are irradiated with NIR light, NO is released in quantifiable amounts while emission from the Nd-UCNPs provides images of microparticle location. Furthermore, varying the intensity of the NIR excitation allows photochemical control over NO release. Low doses reduce levels of hypoxia inducible factor 1 alpha (HIF-1α) in the tumor cells, while high doses are cytotoxic. The use of macrophages to carry microparticles with a NIR photo-activated theranostic payload into a tumor overcomes challenges often faced with therapeutic administration of NO and offers the potential of multiple treatment strategies with a single system.

Inhibition of sirtuins 1 and 2 impairs cell survival and migration and modulates the expression of P-glycoprotein and MRP3 in hepatocellular carcinoma cell lines

Sirtuins (SIRTs) 1 and 2 deacetylases are overexpressed in hepatocellular carcinoma (HCC) and are associated with tumoral progression and multidrug resistance (MDR). In this study we analyzed whether SIRTs 1 and 2 activities blockage was able to affect cellular survival and migration and to modulate p53 and FoxO1 acetylation in HepG2 and Huh7 cells. Moreover, we analyzed ABC transporters P-glycoprotein (P-gp) and multidrug resistance-associated protein 3 (MRP3) expression. We used cambinol and EX-527 as SIRTs inhibitors. Both drugs reduced cellular viability, number of colonies and cellular migration and augmented apoptosis. In 3D cultures, SIRTs inhibitors diminished spheroid growth and viability. 3D culture was less sensitive to drugs than 2D culture. The levels of acetylated p53 and FoxO1 increased after treatments. Drugs induced a decrease in ABC transporters mRNA and protein levels in HepG2 cells; however, only EX-527 was able to reduce MRP3 mRNA and protein levels in Huh7 cells. This is the first work demonstrating the regulation of MRP3 by SIRTs. In conclusion, both drugs decreased HCC cells survival and migration, suggesting SIRTs 1 and 2 activities blockage could be beneficial during HCC therapy. Downregulation of the expression of P-gp and MRP3 supports the potential application of SIRTs 1 and 2 inhibitions in combination with conventional chemotherapy.

Towards clinical translation of ligand-functionalized liposomes in targeted cancer therapy: Challenges and opportunities

The development of therapeutic resistance to targeted anticancer therapies remains a significant clinical problem, with intratumoral heterogeneity playing a key role. In this context, improving the therapeutic outcome through simultaneous targeting of multiple tumor cell subtypes within a heterogeneous tumor is a promising approach. Liposomes have emerged as useful drug carriers that can reduce systemic toxicity and increase drug delivery to the tumor site. While clinically used liposomal drug formulations show marked therapeutic advantages over free drug formulations, ligand-functionalized liposomes that can target multiple tumor cell subtypes may further improve the therapeutic efficacy by facilitating drug delivery to a broader population of tumor cells making up the heterogeneous tumor tissue. Ligand-directed liposomes enable the so-called active targeting of cell receptors via surface-attached ligands that direct drug uptake into tumor cells or tumor-associated stromal cells, and so can increase the selectivity of drug delivery. Despite promising preclinical results demonstrating improved targeting and anti-tumor effects of ligand-directed liposomes, there has been limited translation of this approach to the clinic. Key challenges for translation include the lack of established methods to scale up production and comprehensively characterize ligand-functionalized liposome formulations, as well as the inadequate recapitulation of in vivo tumors in the preclinical models currently used to evaluate their performance. Herein, we discuss the utility of recent ligand-directed liposome approaches, with a focus on dual-ligand liposomes, for the treatment of solid tumors and examine the drawbacks limiting their progression to clinical adoption.

Photosensitive Nanoparticles Combining Vascular-Independent Intratumor Distribution and On-Demand Oxygen-Depot Delivery for Enhanced Cancer Photodynamic Therapy

In drug delivery, the poor tumor perfusion results in disappointing therapeutic efficacy. Nanomedicines for photodynamic therapy (PDT) greatly need deep tumor penetration due to short lifespan and weak diffusion of the cytotoxic reactive oxygen species (ROS). The damage of only shallow cells can easily cause invasiveness and metastasis. Moreover, even if the nanomedicines enter into deeper lesion, the effectiveness of PDT is limited due to the hypoxic microenvironment. Here, a deep penetrating and oxygen self-sufficient PDT nanoparticle is developed for balanced ROS distribution within tumor and efficient cancer therapy. The designed nanoparticles (CNPs/IP) are doubly emulsified (W/O/W) from poly(ethylene glycol)-poly(ε-caprolactone) copolymers doped with photosensitizer IR780 in the O layer and oxygen depot perfluorooctyl bromide (PFOB) inside the core, and functionalized with the tumor penetrating peptide Cys-Arg-Gly-Asp-Lys (CRGDK). The CRGDK modification significantly improves penetration depth of CNPs/IP and makes the CNPs/IP arrive at both the periphery and hypoxic interior of tumors where the PFOB releases oxygen, effectively alleviating hypoxia and guaranteeing efficient PDT performance. The improved intratumoral distribution of photosensitizer and adequate oxygen supply augment the sensitivity of tumor cells to PDT and significantly improve PDT efficiency. Such a nanosystem provides a potential platform for improved therapeutic index in anticancer therapy.

Spheroid-based 3D cell cultures identify salinomycin as a promising drug for the treatment of chondrosarcoma

Chondrosarcoma (CS) is a cartilage malignancy of adulthood that is treated by surgery alone, since chemotherapy is considered ineffective. Unfortunately, a large proportion of patients with CS develop lung metastases, and several die of the disease. In this study, we compared 3D-spheroid cultures and conventional cell monolayer models in order to identify the best way to select anticancer agents that could be effective for the systemic control of CS. Using SW1353 cells, we developed a three-dimensional (3D) in vitro culture model to mimic in vivo features of CS microenvironment and evaluated the efficacy of different drugs to modulate CS cell proliferation and survival in 2D versus 3D-cultures. Doxorubicin (DXR) and cisplatin, that are widely employed in sarcomas, were less effective on 3D-CS spheroids when compared to standard monolayer models, whereas treatment with the ionophore salinomycin (SAL) had a strong cytotoxic effect both on 2D and 3D-cultures. Furthermore, as demonstrated by the reduced viability and the enhanced DXR nuclear localization, SAL enhanced DXR cytotoxicity in 3D-CS spheroids also at sub-lethal doses. SAL activity on 3D-CS spheroids was mediated by a significant induction of apoptosis via caspase activation. This study demonstrates that preclinical tests significantly differ in monolayer and 3D cultures of CS cells. Using this approach, SAL, alone or, at sub-lethal concentrations, in combination with DXR, represents a promising agent for the systemic treatment of CS. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Synthesis, characterization and in vitro and in vivo anticancer activity of Pt(iv) derivatives of [Pt(1S,2S-DACH)(5,6-dimethyl-1,10-phenanthroline)]

This report describes the synthesis, characterization and biological activity of a series of platinum(iv) derivatives of [Pt(1S,2S-DACH)(5,6-dimethyl-1,10-phenanthroline)] (Pt56MeSS) with non-bioactive, lipophilic and bioactive axial ligands. In an attempt to explore the anticancer activity potential of the Pt(iv) derivatives, 2D and 3D cytotoxic screening and a preliminary in vivo study were performed. The average IC₅₀ values of the platinum(iv) derivatives ranged from 1.26 to 5.39 μM, compared with 1.24 μM for Pt56MeSS, suggesting that the axial ligands have a relatively minor effect on the potency of the compounds. Preliminary in vivo studies indicate that the platinum(iv) derivatives of Pt56MeSS are active in vivo and can reduce the tumor to a similar extent to cisplatin.

Induction of hypoxia and necrosis in multicellular tumor spheroids is associated with resistance to chemotherapy treatment

Culture of cancerous cells in standard monolayer conditions poorly mirrors growth in three-dimensional architectures typically observed in a wide majority of cancers of different histological origin. Multicellular tumor spheroid (MCTS) culture models were developed to mimic these features. However, in vivo tumor growth is also characterized by the presence of ischemic and necrotic areas generated by oxygenation gradients and differential access to nutrients. Hypoxia and necrosis play key roles in tumor progression and resistance to treatment. To provide in vitro models recapitulating these events in highly controlled and standardized conditions, we have generated colorectal cancer (CRC) cell spheroids of different sizes and analyzed their gene expression profiles and sensitivity to treatment with 5FU, currently used in therapeutic protocols. Here we identify three MCTS stages, corresponding to defined spheroid sizes, characterized by normoxia, hypoxia, and hypoxia plus necrosis, respectively. Importantly, we show that MCTS including both hypoxic and necrotic areas most closely mimic gene expression profiles of in vivo-developing tumors and display the highest resistance to 5FU. Taken together, our data indicate that MCTS may mimic in vitro generation of ischemic and necrotic areas in highly standardized and controlled conditions, thereby qualifying as relevant models for drug screening purposes.

Automated contour analysis of multi-cellular spheroids spreading through high content imaging

The morphology of 2D cell colonies has been studied to understand tumor metastasis in the past decades. However, 2D cell cultures are lacking many features of 3D tissues, and their physiological behaviors are quite different from solid tumors in vivo. In this work, we studied the multi-cellular tumor spheroid (MCTS) spreading on the substrate, which keeps parts of 3D tissue characteristics and facilitates cell tracking through 2D imaging. By using a high content imaging system (HCS), we tracked multiple spheroids in one single 96-well plate for 36 h. An automated algorithm based on Otsu's method was developed to investigate the morphological details of spheroids through the quantification of radius length and its coefficients of variation. Spheroid spreading is altered by the PIP-platin, which was a novel platinum based drug previously reported by us with an inhibitory effect on cell migration. All parameters showed dose dependent decreases when PIP-platin concentration increased, indicating the inhibition of spheroid expansion by this compound. To investigate the surface roughness of spheroids affected by the drug, we applied the Fourier parameter β and the normalized standard deviation of the radius STD _r / [Formula: see text], which were found inversely proportional to the concentrations of PIP-platin. Particularly at the low drug concentrations, the indices of contour roughness appeared to be more sensitive than spheroid sizes, which could be the potential morphological markers for high content screening of drugs.

Tumor acidosis enhances cytotoxic effects and autophagy inhibition by salinomycin on cancer cell lines and cancer stem cells

Sustained autophagy contributes to the metabolic adaptation of cancer cells to hypoxic and acidic microenvironments. Since cells in such environments are resistant to conventional cytotoxic drugs, inhibition of autophagy represents a promising therapeutic strategy in clinical oncology. We previously reported that the efficacy of hydroxychloroquine (HCQ), an autophagy inhibitor under clinical investigation is strongly impaired in acidic tumor environments, due to poor uptake of the drug, a phenomenon widely associated with drug resistance towards many weak bases. In this study we identified salinomycin (SAL) as a potent inhibitor of autophagy and cytotoxic agent effective on several cancer cell lines under conditions of transient and chronic acidosis. Since SAL has been reported to specifically target cancer-stem cells (CSC), we used an established model of breast CSC and CSC derived from breast cancer patients to examine whether this specificity may be associated with autophagy inhibition. We indeed found that CSC-like cells are more sensitive to autophagy inhibition compared to cells not expressing CSC markers. We also report that the ability of SAL to inhibit mammosphere formation from CSC-like cells was dramatically enhanced in acidic conditions. We propose that the development and use of clinically suitable SAL derivatives may result in improved autophagy inhibition in cancer cells and CSC in the acidic tumor microenvironment and lead to clinical benefits.

Effects of α-Mangostin on Viability, Growth and Cohesion of Multicellular Spheroids Derived from Human Breast Cancer Cell Lines

Background: α-Mangostin (αMG) is extracted from Garcinia mangostana Linn and exerts antiproliferative activities. Although several researches on αMG were performed using cell monolayers, the in vitro pharmacological effects on 3D cancer models have never been investigated. Aim of the present study was to find new anticancer properties of αMG by evaluating the changes that this compound provokes in multicellular tumour spheroids (MCTSs). Methods: MCTSs were generated from MDA-MB-231 and MCF-7 breast tumour cell lines and then treated with 0.1÷30 μg/ml αMG for 24 and 48 h. MCTS size, density, and cell migration were determined by software elaboration of phase contrast images captured by a digital camera. Cell viability was evaluated by resazurin and acid phosphatase assays, while cell apoptosis was assessed by a fluorescent assay of caspase activity. The distribution of living cells inside MCTSs was shown by live/dead fluorescence staining. Results: A dose-dependent decrease in cell viability was obtained by treating MDA-MB-231 spheroids with αMG for 48 h (IC₅₀ = 0.70-1.25 μg/ml). A significant reduction in spheroid volume, paralleled by its increased compactness, was observed only at concentration of 30 μg/ml, but not with lower doses of αMG. By contrast, αMG in the range of 5-15 μg/ml increased the size of MCTSs due to a parallel reduction in cell aggregation. The same window of concentrations was also able to stimulate cell apoptosis in a dose-dependent manner. Bimodal volumetric effects were also obtained by treating the spheroids generated from the MCF-7 cells with 0.1÷30 μg/ml αMG for 48 h. Finally, doses higher than 5 μg/ml caused a progressive impairment in cell migration from the edge of MDA-MB-231 MCTSs. Conclusion: After exposure at doses of αMG just above IC₅₀, MDA-MB-231 spheroids showed a significant reduction in cell adhesion that did not stimulate cell migration but, on the contrary, blunted cell motility. These findings suggest a novel anticancer feature of αMG that could be taken into consideration to improve conventional drug penetration into the tumour bulk.

Particle Targeting in Complex Biological Media

Over the past few decades, nanoengineered particles have gained increasing interest for applications in the biomedical realm, including diagnosis, imaging, and therapy. When functionalized with targeting ligands, these particles have the potential to interact with specific cells and tissues, and accumulate at desired target sites, reducing side effects and improve overall efficacy in applications such as vaccination and drug delivery. However, when targeted particles enter a complex biological environment, the adsorption of biomolecules and the formation of a surface coating (e.g., a protein corona) changes the properties of the carriers and can render their behavior unpredictable. For this reason, it is of importance to consider the potential challenges imposed by the biological environment at the early stages of particle design. This review describes parameters that affect the targeting ability of particulate drug carriers, with an emphasis on the effect of the protein corona. We highlight strategies for exploiting the protein corona to improve the targeting ability of particles. Finally, we provide suggestions for complementing current in vitro assays used for the evaluation of targeting and carrier efficacy with new and emerging techniques (e.g., 3D models and flow-based technologies) to advance fundamental understanding in bio-nano science and to accelerate the development of targeted particles for biomedical applications.

High-Content Monitoring of Drug Effects in a 3D Spheroid Model

A recent decline in the discovery of novel medications challenges the widespread use of 2D monolayer cell assays in the drug discovery process. As a result, the need for more appropriate cellular models of human physiology and disease has renewed the interest in spheroid 3D culture as a pertinent model for drug screening. However, despite technological progress that has significantly simplified spheroid production and analysis, the seeming complexity of the 3D approach has delayed its adoption in many laboratories. The present report demonstrates that the use of a spheroid model may be straightforward and can provide information that is not directly available with a standard 2D approach. We describe a cost-efficient method that allows for the production of an array of uniform spheroids, their staining with vital dyes, real-time monitoring of drug effects, and an ATP-endpoint assay, all in the same 96-well U-bottom plate. To demonstrate the method performance, we analyzed the effect of the preclinical anticancer drug MLN4924 on spheroids formed by VCaP and LNCaP prostate cancer cells. The drug has different outcomes in these cell lines, varying from cell cycle arrest and protective dormancy to senescence and apoptosis. We demonstrate that by using high-content analysis of spheroid arrays, the effect of the drug can be described as a series of EC50 values that clearly dissect the cytostatic and cytotoxic drug actions. The method was further evaluated using four standard cancer chemotherapeutics with different mechanisms of action, and the effect of each drug is described as a unique multi-EC50 diagram. Once fully validated in a wider range of conditions, this method could be particularly valuable for phenotype-based drug discovery.

Organotypic three-dimensional cancer cell cultures mirror drug responses in vivo: lessons learned from the inhibition of EGFR signaling

Complex three-dimensional (3D) in vitro models that recapitulate human tumor biology are essential to understand the pathophysiology of the disease and to aid in the discovery of novel anti-cancer therapies. 3D organotypic cultures exhibit intercellular communication, nutrient and oxygen gradients, and cell polarity that is lacking in two-dimensional (2D) monolayer cultures. In the present study, we demonstrate that 2D and 3D cancer models exhibit different drug sensitivities towards both targeted inhibitors of EGFR signaling and broad acting cytotoxic agents. Changes in the kinase activities of ErbB family members and differential expression of apoptosis- and survival-associated genes before and after drug treatment may account for the differential drug sensitivities. Importantly, EGFR oncoprotein addiction was evident only in the 3D cultures mirroring the effect of EGFR inhibition in the clinic. Furthermore, targeted drug efficacy was strongly increased when incorporating cancer-associated fibroblasts into the 3D cultures. Taken together, we provide conclusive evidence that complex 3D cultures are more predictive of the clinical outcome than their 2D counterparts. In the future, 3D cultures will be instrumental for understanding the mode of action of drugs, identifying genotype-drug response relationships and developing patient-specific and personalized cancer treatments.

In-depth phenotypic characterization of multicellular tumor spheroids: Effects of 5-Fluorouracil

MultiCellular Tumor Spheroids (MCTS), which mimic the 3-Dimensional (3D) organization of a tumor, are considered as better models than conventional cultures in 2-Dimensions (2D) to study cancer cell biology and to evaluate the response to chemotherapeutic drugs. A real time and quantitative follow-up of MCTS with simple and robust readouts to evaluate drug efficacy is still missing. Here, we evaluate the chemotherapeutic drug 5-Fluorouracil (5-FU) response on the growth and integrity of MCTS two days after treatment of MCTS and for three colorectal carcinoma cell lines with different cohesive properties (HT29, HCT116 and SW480). We found different sensitivity to 5-FU for the three CRC cell lines, ranging from high (SW480), intermediate (HCT116) and low (HT29) and the same hierarchy of CRC cell lines sensitivity is conserved in 2D. We also evidence that 5-FU has a strong impact on spheroid cohesion, with the apparition of a number of single detaching cells from the spheroid in a 5-FU dose- and cell line-dependent manner. We propose an innovative methodology for the chemosensitivity evaluation in 3D MCTS that recapitulates and regionalizes the 5-FU-induced changes within MCTS over time. These robust phenotypic read-outs could be easily scalable for high-throughput drug screening that may include different types of cancer cells to take into account tumor heterogeneity and resistance to treatment.

Therapeutic potential of the phosphino Cu(I) complex (HydroCuP) in the treatment of solid tumors

[Cu(thp)₄][PF₆] (HydroCuP) is a phosphino copper(I) complex highly soluble and stable in physiological media that has been developed as a possible viable alternative to platinum-based drugs for anticancer therapy. HydroCuP potently inhibited the growth of human cancer cells derived from solid tumors by inducing endoplasmatic reticulum (ER) stress thus leading to cell death through paraptosis with a preferential efficacy against cancer rather than non-cancer cells. Aim of the present study was to assess the therapeutic potential of HydroCuP in vivo, in syngenic and xenograft murine models of solid tumors by triggering the Unfolded Protein Response (UPR) pathway. With respect to platinum drugs, HydroCuP induced a markedly higher reduction of tumor growth associated with minimal animal toxicity. In human colorectal cancer xenografts, chemotherapy with HydroCuP was extremely effective in both oxaliplatin-sensitive and resistant models. The favorable in vivo tolerability of HydroCuP was also correlated to an encouraging biodistribution profile. Additionally, no signs of drug-related neurotoxicity and nephrotoxicity were observed. Altogether, these results demonstrate that HydroCuP appears worth of further investigation to evaluate its therapeutic activity towards a broad spectrum of solid malignancies.

Application of the rainbow trout derived intestinal cell line (RTgutGC) for ecotoxicological studies: molecular and cellular responses following exposure to copper

There is an acknowledged need for in vitro fish intestinal model to help understand dietary exposure to chemicals in the aquatic environment. The presence and use of such models is however largely restrictive due to technical difficulties in the culturing of enterocytes in general and the availability of appropriate established cell lines in particular. In this study, the rainbow trout (Oncorhynchus mykiss) intestinal derived cell line (RTgutGC) was used as a surrogate for the "gut sac" method. To facilitate comparison, RTgutGC cells were grown as monolayers (double-seeded) on permeable Transwell supports leading to a two-compartment intestinal model consisting of polarised epithelium. This two-compartment model divides the system into an upper apical (lumen) and a lower basolateral (portal blood) compartment. In our studies, these cells stained weakly for mucosubstances, expressed the tight junction protein ZO-1 in addition to E-cadherin and revealed the presence of polarised epithelium in addition to microvilli protrusions. The cells also revealed a comparable transepithelial electrical resistance (TEER) to the in vivo situation. Importantly, the cell line tolerated apical saline (1:1 ratio) thus mimicking the intact organ to allow assessment of uptake of compounds across the intestine. Following an exposure over 72 h, our study demonstrated that the RTgutGC cell line under sub-lethal concentrations of copper sulphate (Cu) and modified saline solutions demonstrated uptake of the metal with saturation levels comparable to short term ex situ gut sac preparations. Gene expression analysis revealed no significant influence of pH or time on mRNA expression levels of key stress related genes (i.e. CYP3A, GST, mtA, Pgp and SOD) in the Transwell model. However, significant positive correlations were found between all genes investigated suggesting a co-operative relationship amongst the genes studied. When the outlined characteristics of the cell line are combined with the division of compartments, the RTgutGC double seeded model represents a potential animal replacement model for ecotoxicological studies. Overall, this model could be used to study the effects and predict aquatic gastrointestinal permeability of metals and other environmentally relevant contaminants in a cost effective and high throughput manner.

Inhibition of bioenergetic metabolism by the combination of metformin and 2-deoxyglucose highly decreases viability of feline mammary carcinoma cells

Feline mammary carcinoma (FMC) is a highly aggressive pathology that has been proposed as an interesting model of breast cancer disease, especially for the hormone refractory subgroup. Recently, cancer cell metabolism has been described as a hallmark of cancer cells. Here, we investigate the effects and mechanism of metabolic modulation by metformin (MET, anti-diabetic drug), 2-deoxyglucose (2DG, hexokinase inhibitor) or a combination of both drugs, MET/2DG on two established FMC cells lines: AlRB (HER2 (3+) and Ki67<5%) and AlRATN (HER2 (-) and Ki67>15%). We found that treatments significantly decreased both FMC cells viability by up to 80%. AlRB resulted more sensitive to 2DG than AlRATN (IC50: 3.15 vs 6.32mM, respectively). The combination of MET/2DG potentiated the effects of the individually added drugs on FMC cells. In addition, MET/2DG caused an increased in intracellular oxidants, autophagic vesicles and completely inhibited colony formation. Conversely, only MET significantly altered plasma membrane integrity, presented late apoptotic/necrotic cells and increased both glucose consumption and lactate concentration. Our results support further studies to investigate the potential use of this metabolic modulation approach in a clinical veterinary setting.

A novel individual-cell-based mathematical model based on multicellular tumour spheroids for evaluating doxorubicin-related delivery in avascular regions

BACKGROUND AND PURPOSE

Effective drug delivery in the avascular regions of tumours, which is crucial for the promising antitumour activity of doxorubicin-related therapy, is governed by two inseparable processes: intercellular diffusion and intracellular retention. To accurately evaluate doxorubicin-related delivery in the avascular regions, these two processes should be assessed together. Here we describe a new approach to such an assessment.

EXPERIMENTAL APPROACH

An individual-cell-based mathematical model based on multicellular tumour spheroids was developed that describes the different intercellular diffusion and intracellular retention kinetics of doxorubicin in each cell layer. The different effects of a P-glycoprotein inhibitor (LY335979) and a hypoxia inhibitor (YC-1) were quantitatively evaluated and compared, in vitro (tumour spheroids) and in vivo (HepG2 tumours in mice). This approach was further tested by evaluating in these models, an experimental doxorubicin derivative, INNO 206, which is in Phase II clinical trials.

KEY RESULTS

Inhomogeneous, hypoxia-induced, P-glycoprotein expression compromised active transport of doxorubicin in the central area, that is, far from the vasculature. LY335979 inhibited efflux due to P-glycoprotein but limited levels of doxorubicin outside the inner cells, whereas YC-1 co-administration specifically increased doxorubicin accumulation in the inner cells without affecting the extracellular levels. INNO 206 exhibited a more effective distribution profile than doxorubicin.

CONCLUSIONS AND IMPLICATIONS

The individual-cell-based mathematical model accurately evaluated and predicted doxorubicin-related delivery and regulation in the avascular regions of tumours. The described framework provides a mechanistic basis for the proper development of doxorubicin-related drug co-administration profiles and nanoparticle development and could avoid unnecessary clinical trials.

Methods: Using Three-Dimensional Culture (Spheroids) as an In Vitro Model of Tumour Hypoxia

Regions of hypoxia in tumours can be modelled in vitro in 2D cell cultures with a hypoxic chamber or incubator in which oxygen levels can be regulated. Although this system is useful in many respects, it disregards the additional physiological gradients of the hypoxic microenvironment, which result in reduced nutrients and more acidic pH. Another approach to hypoxia modelling is to use three-dimensional spheroid cultures. In spheroids, the physiological gradients of the hypoxic tumour microenvironment can be inexpensively modelled and explored. In addition, spheroids offer the advantage of more representative modelling of tumour therapy responses compared with 2D culture. Here, we review the use of spheroids in hypoxia tumour biology research and highlight the different methodologies for spheroid formation and how to obtain uniformity. We explore the challenge of spheroid analyses and how to determine the effect on the hypoxic versus normoxic components of spheroids. We discuss the use of high-throughput analyses in hypoxia screening of spheroids. Furthermore, we examine the use of mathematical modelling of spheroids to understand more fully the hypoxic tumour microenvironment.

Cancer cell spheroids are a better screen for the photodynamic efficiency of glycosylated photosensitizers

Photodynamic Therapy (PDT) relies on the use of non-toxic photosensitizers that are locally and selectively activated by light to induce cell death or apoptosis through reactive oxygen species generation. The conjugation of porphyrinoids with sugars that target cancer is increasingly viewed as an effective way to increase the selectivity of PDT. To date, in vitro PDT efficacy is mostly screened using two-dimensional monolayer cultures. Compared to monolayer cultures, three-dimensional spheroid cultures have unique spatial distributions of nutrients, metabolites, oxygen and signalling molecules; therefore better mimic in vivo conditions. We obtained 0.05 mm3 spheroids with four different human tumor cell lines (HCT-116, MCF-7, UM-UC-3 and HeLa) with appropriate sizes for screening PDT agents. We observed that detachment from monolayer culture and growth as tumor spheroids was accompanied by changes in glucose metabolism, endogenous ROS levels, galectin-1 and glucose transporter GLUT1 protein levels. We compared the phototoxic responses of a porphyrin conjugated with four glucose molecules (PorGlu4) in monolayer and spheroid cultures. The uptake and phototoxicity of PorGlu4 is highly dependent on the monolayer versus spheroid model used and on the different levels of GLUT1 protein expressed by these in vitro platforms. This study demonstrates that HCT-116, MCF-7, UM-UC-3 and HeLa spheroids afford a more rational platform for the screening of new glycosylated-photosensitizers compared to monolayer cultures of these cancer cells.

Quantum Dot Nanotoxicity Investigations Using Human Lung Cells and TOXOR Electrochemical Enzyme Assay Methodology

Recent studies have suggested that certain nanomaterials can interfere with optically based cytotoxicity assays resulting in underestimations of nanomaterial toxicity. As a result there has been growing interest in the use of whole cell electrochemical biosensors for nanotoxicity applications. Herein we report application of an electrochemical cytotoxicity assay developed in house (TOXOR) in the evaluation of toxic effects of mercaptosuccinic acid capped cadmium telluride quantum dots (MSA capped CdTe QDs), toward mammalian cells. MSA capped CdTe QDs were synthesized, characterized, and their cytotoxicity toward A549 human lung epithelial cells investigated. The internalization of QDs within cells was scrutinized via confocal microscopy. The cytotoxicity assay is based on the measurement of changes in cellular enzyme acid phosphatase upon 24 h exposure to QDs. Acid phosphatase catalyzes dephosphorylation of 2-naphthyl phosphate to 2-naphthol (determined by chronocoulometry) and is indicative of metabolic activity in cells. The 24 h IC50 (concentration resulting in 50% reduction in acid phosphatase activity) value for MSA capped CdTe QDs was found to be 118 ± 49 μg/mL using the TOXOR assay and was in agreement with the MTT assay (157 ± 31 μg/mL). Potential uses of this electrochemical assay include the screening of nanomaterials, environmental toxins, in addition to applications in the pharmaceutical, food, and health sectors.

High-Throughput Spheroid Screens Using Volume, Resazurin Reduction, and Acid Phosphatase Activity

Mainstream adoption of physiologically relevant three-dimensional models has been slow in the last 50 years due to long, manual protocols with poor reproducibility, high price, and closed commercial platforms. This chapter describes high-throughput, low-cost, open methods for spheroid viability assessment which use readily available reagents and open-source software to analyze spheroid volume, metabolism, and enzymatic activity. We provide two ImageJ macros for automated spheroid size determination-for both single images and images in stacks. We also share an Excel template spreadsheet allowing users to rapidly process spheroid size data, analyze plate uniformity (such as edge effects and systematic seeding errors), detect outliers, and calculate dose-response. The methods would be useful to researchers in preclinical and translational research planning to move away from simplistic monolayer studies and explore 3D spheroid screens for drug safety and efficacy without substantial investment in money or time.

Multicellular tumor spheroids: a relevant 3D model for the in vitro preclinical investigation of polymer nanomedicines

Application of 3D multicellular tumor spheroids to the investigation of polymer nanomedicines.

MicroRNA-200c delivered by solid lipid nanoparticles enhances the effect of paclitaxel on breast cancer stem cell

Background

One of the major obstacles in the treatment of breast cancer is breast cancer stem cells (BCSC) which are resistant to standard chemotherapeutic drugs. It has been proven that microRNA-200c (miR-200c) can restore sensitivity to microtubule-targeting chemotherapeutic drugs by reducing the expression of class III β-tubulin. In this study, combination therapy with miR-200c and paclitaxel (PTX) mediated by lipid nanoparticles was investigated as an alternative strategy against BCSC.

Materials and methods

A cationic lipid 1,2-dioleoyl-3-trimethylammonium-propane was strategically selected to formulate solid lipid nanoparticles (SLN) for miR-200c delivery. Nanostructured lipid carriers (NLC) with 20 wt% oleic acid were prepared for PTX delivery. Mammospheres, which gained the characteristics of BCSC, were used as a cell model to evaluate the efficiency of combination therapy.

Results

The cationic SLN could condense anionic miRNA to form SLN/miRNA complexes via charge interactions and could protect miRNA from degradation by ribonuclease. SLN/miR-200c complexes achieved 11.6-fold expression of miR-200c after incubation for 24 hours, compared with that of Lipofectamine™ 2000/miR-200c complexes (*P<0.05). Intracellular drug release assay proved that miRNA can be released from SLN/miRNA complexes efficiently in 12 hours after cellular uptake. After BCSC were transfected with SLN/miR-200c, the expression of class III β-tubulin was effectively downregulated and the cellular cytotoxicity of PTX-loaded NLC (NLC/PTX) against BCSC was enhanced significantly (**P<0.01).

Conclusion

The results indicated that the cationic SLN could serve as a promising carrier for miRNA delivery. In addition, the combination therapy of miR-200c and PTX revealed a novel therapeutic strategy for the treatment of BCSC.

3D tumor spheroids: an overview on the tools and techniques used for their analysis

In comparison with 2D cell culture models, 3D spheroids are able to accurately mimic some features of solid tumors, such as their spatial architecture, physiological responses, secretion of soluble mediators, gene expression patterns and drug resistance mechanisms. These unique characteristics highlight the potential of 3D cellular aggregates to be used as in vitro models for screening new anticancer therapeutics, both at a small and large scale. Nevertheless, few reports have focused on describing the tools and techniques currently available to extract significant biological data from these models. Such information will be fundamental to drug and therapeutic discovery process using 3D cell culture models. The present review provides an overview of the techniques that can be employed to characterize and evaluate the efficacy of anticancer therapeutics in 3D tumor spheroids.

The third dimension: new developments in cell culture models for colorectal research

Cellular models are important tools in various research areas related to colorectal biology and associated diseases. Herein, we review the most widely used cell lines and the different techniques to grow them, either as cell monolayer, polarized two-dimensional epithelia on membrane filters, or as three-dimensional spheres in scaffold-free or matrix-supported culture conditions. Moreover, recent developments, such as gut-on-chip devices or the ex vivo growth of biopsy-derived organoids, are also discussed. We provide an overview on the potential applications but also on the limitations for each of these techniques, while evaluating their contribution to provide more reliable cellular models for research, diagnostic testing, or pharmacological validation related to colon physiology and pathophysiology.

In vitro and in vivo antitumor effects of the VO-chrysin complex on a new three-dimensional osteosarcoma spheroids model and a xenograft tumor in mice

Osteosarcoma (OS) is the most common primary tumor of bone, occurring predominantly in the second decade of life. High-dose cytotoxic chemotherapy and surgical resection have improved prognosis, with long-term survival for patients with localized disease. Vanadium is an ultra-trace element that after being absorbed accumulates in bone. Besides, vanadium compounds have been studied during recent years to be considered as representative of a new class of non-platinum antitumor agents. Moreover, flavonoids are a wide family of polyphenolic compounds that display many interesting biological effects. Since coordination of ligands to metals can improve the pharmacological properties, we report herein, for the first time, the in vitro and in vivo effects of an oxidovanadium(IV) complex with the flavonoid chrysin on the new 3D human osteosarcoma and xenograft osteosarcoma mice models. The pharmacological results show that VOchrys inhibited the cell viability affecting the shape and volume of the spheroids and VOchrys suppressed MG-63 tumor growth in the nude mice without inducing toxicity and side effects. As a whole, the results presented herein demonstrate that the antitumor action of the complex was very promissory on human osteosarcoma models, whereby suggesting that VOchrys is a potentially good candidate for future use in alternative antitumor treatments.

Obatoclax kills anaplastic thyroid cancer cells by inducing lysosome neutralization and necrosis

Poorly differentiated and anaplastic thyroid carcinomas are very aggressive, almost invariably lethal neoplasms for which no effective treatment exists. These tumors are intrinsically resistant to cell death, even when their driver oncogenic signaling pathways are inhibited.We have undertaken a detailed analysis, in mouse and human thyroid cancer cells, of the mechanism through which Obatoclax, a pan-inhibitor of the anti-apoptotic proteins of the BCL2 family, effectively reduces tumor growth in vitro and in vivo.We demonstrate that Obatoclax does not induce apoptosis, but rather necrosis of thyroid cancer cells, and that non-transformed thyroid cells are significantly less affected by this compound. Surprisingly, we show that Obatoclax rapidly localizes to the lysosomes and induces loss of acidification, block of lysosomal fusion with autophagic vacuoles, and subsequent lysosomal permeabilization. Notably, prior lysosome neutralization using different V-ATPase inhibitors partially protects cancer cells from the toxic effects of Obatoclax. Although inhibition of autophagy does not affect Obatoclax-induced cell death, selective down-regulation of ATG7, but not of ATG5, partially impairs Obatoclax effects, suggesting the existence of autophagy-independent functions for ATG7. Strikingly, Obatoclax killing activity depends only on its accumulation in the lysosomes, and not on its interaction with BCL2 family members.Finally, we show that also other lysosome-targeting compounds, Mefloquine and LLOMe, readily induce necrosis in thyroid cancer cells, and that Mefloquine significantly impairs tumor growth in vivo, highlighting a clear vulnerability of these aggressive, apoptosis-resistant tumors that can be therapeutically exploited.

The proteasome deubiquitinase inhibitor VLX1570 shows selectivity for ubiquitin-specific protease-14 and induces apoptosis of multiple myeloma cells

Inhibition of deubiquitinase (DUB) activity is a promising strategy for cancer therapy. VLX1570 is an inhibitor of proteasome DUB activity currently in clinical trials for relapsed multiple myeloma. Here we show that VLX1570 binds to and inhibits the activity of ubiquitin-specific protease-14 (USP14) in vitro, with comparatively weaker inhibitory activity towards UCHL5 (ubiquitin-C-terminal hydrolase-5). Exposure of multiple myeloma cells to VLX1570 resulted in thermostabilization of USP14 at therapeutically relevant concentrations. Transient knockdown of USP14 or UCHL5 expression by electroporation of siRNA reduced the viability of multiple myeloma cells. Treatment of multiple myeloma cells with VLX1570 induced the accumulation of proteasome-bound high molecular weight polyubiquitin conjugates and an apoptotic response. Sensitivity to VLX1570 was moderately affected by altered drug uptake, but was unaffected by overexpression of BCL2-family proteins or inhibitors of caspase activity. Finally, treatment with VLX1570 was found to lead to extended survival in xenograft models of multiple myeloma. Our findings demonstrate promising antiproliferative activity of VLX1570 in multiple myeloma, primarily associated with inhibition of USP14 activity.