3D breast cancer microtissue reveals the role of tumor microenvironment on the transport and efficacy of free-doxorubicin in vitro

Cytotoxic and molecular differences of anticancer agents on 2D and 3D cell culture

BACKGROUND

Cancer and multidrug resistance are regarded as concerns related to poor health outcomes. It was found that the monolayer of 2D cancer cell cultures lacks many important features compared to Multicellular Tumor Spheroids (MCTS) or 3D cell cultures which instead have the ability to mimic more closely the in vivo tumor microenvironment. This study aimed to produce 3D cell cultures from different cancer cell lines and to examine the cytotoxic activity of anticancer medications on both 2D and 3D systems, as well as to detect alterations in the expression of certain genes levels.

METHOD

3D cell culture was produced using 3D microtissue molds. The cytotoxic activities of colchicine, cisplatin, doxorubicin, and paclitaxel were tested on 2D and 3D cell culture systems obtained from different cell lines (A549, H1299, MCF-7, and DU-145). IC50 values were determined by MTT assay. In addition, gene expression levels of PIK3CA, AKT1, and PTEN were evaluated by qPCR.

RESULTS

Similar cytotoxic activities were observed on both 3D and 2D cell cultures, however, higher concentrations of anticancer medications were needed for the 3D system. For instance, paclitaxel showed an IC50 of 6.234 µM and of 13.87 µM on 2D and 3D H1299 cell cultures, respectively. Gene expression of PIK3CA in H1299 cells also showed a higher fold change in 3D cell culture compared to 2D system upon treatment with doxorubicin.

CONCLUSION

When compared to 2D cell cultures, the behavior of cells in the 3D system showed to be more resistant to anticancer treatments. Due to their shape, growth pattern, hypoxic core features, interaction between cells, biomarkers synthesis, and resistance to treatment penetration, the MCTS have the advantage of better simulating the in vivo tumor conditions. As a result, it is reasonable to conclude that 3D cell cultures may be a more promising model than the traditional 2D system, offering a better understanding of the in vivo molecular changes in response to different potential treatments and multidrug resistance development.

Synergistic Action of Benzyl Isothiocyanate and Sorafenib in a Nanoparticle Delivery System for Enhanced Triple-Negative Breast Cancer Treatment

Triple-negative breast cancer (TNBC) presents a therapeutic challenge due to its complex pathology and limited treatment options. Addressing this challenge, our study focuses on the effectiveness of combination therapy, which has recently become a critical strategy in cancer treatment, improving therapeutic outcomes and combating drug resistance and metastasis. We explored a novel combination therapy employing Benzyl isothiocyanate (BITC) and Sorafenib (SOR) and their nanoformulation, aiming to enhance therapeutic outcomes against TNBC. Through a series of in vitro assays, we assessed the cytotoxic effects of BITC and SOR, both free and encapsulated. The BITC-SOR-loaded nanoparticles (NPs) were synthesized using an amphiphilic copolymer, which demonstrated a uniform spherical morphology and favorable size distribution. The encapsulation efficiencies, as well as the sustained release profiles at varied pH levels, were quantified, revealing distinct kinetics that were well-modeled by the Korsmeyer-Peppas equation. The NP delivery system showed a marked dose-dependent cytotoxicity towards TNBC cells, with an IC50 of 7.8 μM for MDA-MB-231 cells, indicating improved efficacy over free drugs, while exhibiting minimal toxicity toward normal breast cells. Furthermore, the NPs significantly inhibited cell migration and invasion in TNBC models, surpassing the effects of free drugs. These findings underscore the potential of BITC-SOR-NPs as a promising therapeutic approach for TNBC, offering targeted delivery while minimizing systemic toxicity.

miRNAs Delivery for Cancer-associated Fibroblasts' Activation and Drug Resistance in Cancer Microenvironment

Cancer-associated fibroblasts (CAFs) as a major component of cancer stroma contribute to diverse procedures of most solid tumors and might be a targeted cancer therapy approach. Their specified features, related signaling pathways, distinct biomarkers, and sub-populations need to be deciphered. There is a need for CAF extraction or induction for in vitro investigations. Some miRNAs could activate CAF-like phenotype and they also interfere in CAF-mediated drug resistance, aggressiveness, and metastatic behaviors of several cancer cell types. Due to the complex relevance of miRNA and CAFs, these non-coding oligonucleotides may serve as attractive scope for anti-cancer targeted therapies, but the lack of an efficient delivery system is still a major hurdle. Here, we have summarized the investigated information on CAF features, isolation, and induction procedures, and highlighted the miRNA-CAF communications, providing special insight into nano-delivery systems.

Deciphering Common Traits of Breast and Ovarian Cancer Stem Cells and Possible Therapeutic Approaches

Breast cancer (BC) and ovarian cancer (OC) are among the most common and deadly cancers affecting women worldwide. Both are complex diseases with marked heterogeneity. Despite the induction of screening programs that increase the frequency of earlier diagnosis of BC, at a stage when the cancer is more likely to respond to therapy, which does not exist for OC, more than 50% of both cancers are diagnosed at an advanced stage. Initial therapy can put the cancer into remission. However, recurrences occur frequently in both BC and OC, which are highly cancer-subtype dependent. Therapy resistance is mainly attributed to a rare subpopulation of cells, named cancer stem cells (CSC) or tumor-initiating cells, as they are capable of self-renewal, tumor initiation, and regrowth of tumor bulk. In this review, we will discuss the distinctive markers and signaling pathways that characterize CSC, their interactions with the tumor microenvironment, and the strategies they employ to evade immune surveillance. Our focus will be on identifying the common features of breast cancer stem cells (BCSC) and ovarian cancer stem cells (OCSC) and suggesting potential therapeutic approaches.

Metal-Organic Framework Mediated Radio-Enhancement Assessed in High-Throughput-Compatible 3D Tumor Spheroid Co-Cultures

Inorganic nanomaterials have gained increasing attention in radiation oncology, owing to their radiation therapy enhancing properties. To accelerate candidate material selection and overcome the disconnect between conventional 2D cell culture and in vivo findings, screening platforms unifying high-throughput with physiologically relevant endpoint analysis based on 3D in vitro models are promising. Here, a 3D tumor spheroid co-culture model based on cancerous and healthy human cells is presented for the concurrent assessment of radio-enhancement efficacy, toxicity, and intratissural biodistribution with full ultrastructural context of radioenhancer candidate materials. Its potential for rapid candidate materials screening is showcased based on the example of nano-sized metal-organic frameworks (nMOFs) and direct benchmarking against gold nanoparticles (the current "gold standard"). Dose enhancement factors (DEFs) ranging between 1.4 and 1.8 are measured for Hf-, Ti-, TiZr-, and Au-based materials in 3D tissues and are overall lower than in 2D cell cultures, where DEF values exceeding 2 are found. In summary, the presented co-cultured tumor spheroid-healthy fibroblast model with tissue-like characteristics may serve as high-throughput platform enabling rapid, cell line-specific endpoint analysis for therapeutic efficacy and toxicity assessment, as well as accelerated radio-enhancer candidate screening.

The Variety of 3D Breast Cancer Models for the Study of Tumor Physiology and Drug Screening

Breast cancer is the most common cancer in women and responsible for multiple deaths worldwide. 3D cancer models enable a better representation of tumor physiology than the conventional 2D cultures. This review summarizes the important components of physiologically relevant 3D models and describes the spectrum of 3D breast cancer models, e.g., spheroids, organoids, breast cancer on a chip and bioprinted tissues. The generation of spheroids is relatively standardized and easy to perform. Microfluidic systems allow control over the environment and the inclusion of sensors and can be combined with spheroids or bioprinted models. The strength of bioprinting relies on the spatial control of the cells and the modulation of the extracellular matrix. Except for the predominant use of breast cancer cell lines, the models differ in stromal cell composition, matrices and fluid flow. Organoids are most appropriate for personalized treatment, but all technologies can mimic most aspects of breast cancer physiology. Fetal bovine serum as a culture supplement and Matrigel as a scaffold limit the reproducibility and standardization of the listed 3D models. The integration of adipocytes is needed because they possess an important role in breast cancer.

In vitro models of breast cancer bone metastasis: analyzing drug resistance through the lens of the microenvironment

Even though breast cancers usually have a good outcome compared to other tumors, the cancer can progress and create metastases in different parts of the organism, the bone being a predilection locus. These metastases are usually the cause of death, as they are mostly resistant to treatments. This resistance can be caused by intrinsic properties of the tumor, such as its heterogeneity, but it can also be due to the protective role of the microenvironment. By activating signaling pathways protecting cancer cells when exposed to chemotherapy, contributing to their ability to reach dormancy, or even reducing the amount of drug able to reach the metastases, among other mechanisms, the specificities of the bone tissue are being investigated as important players of drug resistance. To this date, most mechanisms of this resistance are yet to be discovered, and many researchers are implementing in vitro models to study the interaction between the tumor cells and their microenvironment. Here, we will review what is known about breast cancer drug resistance in bone metastasis due to the microenvironment and we will use those observations to highlight which features in vitro models should include to properly recapitulate these biological aspects in vitro. We will also detail which elements advanced in vitro models should implement in order to better recapitulate in vivo physiopathology and drug resistance.

Multi compartmental 3D breast cancer disease model–recapitulating tumor complexity in in-vitro

Breast cancer is the most common ailment among women. In 2020, it had the highest incidence of any type of cancer. Many Phase II and III anti-cancer drugs fail due to efficacy, durability, and side effects. Thus, accelerated drug screening models must be accurate. In-vivo models have been used for a long time, but delays, inconsistent results, and a greater sense of responsibility among scientists toward wildlife have led to the search for in-vitro alternatives. Stromal components support breast cancer growth and survival. Multi-compartment Transwell models may be handy instruments. Co-culturing breast cancer cells with endothelium and fibroblasts improves modelling. The extracellular matrix (ECM) supports native 3D hydrogels in natural and polymeric forms. 3D Transwell cultured tumor spheroids mimicked in-vivo pathological conditions. Tumor invasion, migration, Trans-endothelial migration, angiogenesis, and spread are studied using comprehensive models. Transwell models can create a cancer niche and conduct high-throughput drug screening, promising future applications. Our comprehensive shows how 3D in-vitro multi compartmental models may be useful in producing breast cancer stroma in Transwell culture.

Colorectal Cancer Bioengineered Microtissues as a Model to Replicate Tumor-ECM Crosstalk and Assess Drug Delivery Systems In Vitro

Current 3D cancer models (in vitro) fail to reproduce complex cancer cell extracellular matrices (ECMs) and the interrelationships occurring (in vivo) in the tumor microenvironment (TME). Herein, we propose 3D in vitro colorectal cancer microtissues (3D CRC μTs), which reproduce the TME more faithfully in vitro. Normal human fibroblasts were seeded onto porous biodegradable gelatin microbeads (GPMs) and were continuously induced to synthesize and assemble their own ECMs (3D Stroma μTs) in a spinner flask bioreactor. Then, human colon cancer cells were dynamically seeded onto the 3D Stroma μTs to achieve the 3D CRC μTs. Morphological characterization of the 3D CRC μTs was performed to assess the presence of different complex macromolecular components that feature in vivo in the ECM. The results showed the 3D CRC μTs recapitulated the TME in terms of ECM remodeling, cell growth, and the activation of normal fibroblasts toward an activated phenotype. Then, the microtissues were assessed as a drug screening platform by evaluating the effect of 5-Fluorouracil (5-FU), curcumin-loaded nanoemulsions (CT-NE-Curc), and the combination of the two. When taken together, the results showed that our microtissues are promising in that they can help clarify complex cancer–ECM interactions and evaluate the efficacy of therapies. Moreover, they may be combined with tissue-on-chip technologies aimed at addressing further studies in cancer progression and drug discovery.

Microfluidically-generated Encapsulated Spheroids (μ-GELS): An All-Aqueous Droplet Microfluidics Platform for Multicellular Spheroids Generation

Spheroids are three-dimensional clusters of cells that serve as in vitro tumor models to recapitulate in vivo morphology. A limitation of many existing on-chip platforms for spheroid formation is the use of cytotoxic organic solvents as the continuous phase in droplet generation processes. All-aqueous methods do not contain cytotoxic organic solvents but have so far been unable to achieve complete hydrogel gelation on chip. Here, we describe an enhanced droplet microfluidic platform that achieves on-chip gelation of all-aqueous hydrogel multicellular spheroids (MCSs). Specifically, we generate dextran-alginate droplets containing MCF-7 breast cancer cells, surrounded by polyethylene glycol, at a flow-focusing junction. Droplets then travel to a second flow-focusing junction where they interact with calcium chloride and gel on chip to form hydrogel MCSs. On-chip gelation of the MCSs is possible here because of an embedded capillary at the second junction that delays the droplet gelation, which prevents channel clogging problems that would otherwise exist. In drug-free experiments, we demonstrate that MCSs remain viable for 6 days. We also confirm the applicability of this system for cancer drug testing by observing that dose-dependent cell death is achievable using doxorubicin.

Capturing the spatial and temporal dynamics of tumor stroma for on-chip optimization of microenvironmental targeting nanomedicine

Malignant cells grow in a complex microenvironment that plays a key role in cancer progression. The "dynamic reciprocity" existing between cancer cells and their microenvironment is involved in cancer differentiation, proliferation, invasion, metastasis, and drug response. Therefore, understanding the molecular mechanisms underlying the crosstalk between cancer cells and their surrounding tissue (i.e., tumor stroma) and how this interplay affects the disease progression is fundamental to design and validate novel nanotherapeutic approaches. As an important regulator of tumor progression, metastasis and therapy resistance, the extracellular matrix of tumors, the acellular component of the tumor microenvironment, has been identified as very promising target of anticancer treatment, revolutionizing the traditional therapeutic paradigm that sees the neoplastic cells as the preferential objective to fight cancer. To design and to validate such a target therapy, advanced 3D preclinical models are necessary to correctly mimic the complex, dynamic and heterogeneous tumor microenvironment. In addition, the recent advancement in microfluidic technology allows fine-tuning and controlling microenvironmental parameters in tissue-on-chip devices in order to emulate the in vivo conditions. In this review, after a brief description of the origin of tumor microenvironment heterogeneity, some examples of nanomedicine approaches targeting the tumor microenvironment have been reported. Further, how advanced 3D bioengineered tumor models coupled with a microfluidic device can improve the design and testing of anti-cancer nanomedicine targeting the tumor microenvironment has been discussed. We highlight that the presence of a dynamic extracellular matrix, able to capture the spatiotemporal heterogeneity of tumor stroma, is an indispensable requisite for tumor-on-chip model and nanomedicine testing.

Enabling perfusion through multicellular tumor spheroids promoting lumenization in a vascularized cancer model

A tumor is composed of heterogeneous cell population, which is known as tumor stroma. In particular, blood vessels have an indispensable role in the tumor microenvironment acting as a key player in anti-cancer drug delivery. Recently, efforts have been made to accurately recapitulate the microenvironment by employing distinct cell types, however, the proper formation of perfusable tumor tissue is challenging. Here, perfusable tumor tissue is engineered by implanting multicellular tumor spheroids inside the microfluidic devices. Blood perfusion, spheroid growth, and vascular dynamics were monitored according to the spheroid composition and the contribution of internal and external vascular cells to spheroid perfusion was analyzed. Most notably, the increased penetration depth of fluorescence conjugated anti-cancer drug was observed in tri-culture spheroids. The implementation of tumor microenvironment reconstruction developed in this study not only creates a perfusable tumor vascular model but can also be utilized as a novel drug screening platform with patient-derived samples.

Three-Dimensional in Vitro Models: A Promising Tool To Scale-Up Breast Cancer Research

Common models used in breast cancer studies, including two-dimensional (2D) cultures and animal models, do not precisely model all aspects of breast tumors. These models do not well simulate the cell-cell and cell-stromal interactions required for normal tumor growth in the body and lake tumor like microenvironment. Three-dimensional (3D) cell culture models are novel approaches to studying breast cancer. They do not have the restrictions of these conventional models and are able to recapitulate the structural architecture, complexity, and specific function of breast tumors and provide similar in vivo responses to therapeutic regimens. These models can be a link between former traditional 2D culture and in vivo models and are necessary for further studies in cancer. This review attempts to summarize the most common 3D in vitro models used in breast cancer studies, including scaffold-free (spheroid and organoid), scaffold-based, and chip-based models, particularly focused on the basic and translational application of these 3D models in drug screening and the tumor microenvironment in breast cancer.

Bench to Bedside: New Therapeutic Approaches with Extracellular Vesicles and Engineered Biomaterials for Targeting Therapeutic Resistance of Cancer Stem Cells

Cancer has recently been the second leading cause of death worldwide, trailing only cardiovascular disease. Cancer stem cells (CSCs), represented as tumor-initiating cells (TICs), are mainly liable for chemoresistance and disease relapse due to their self-renewal capability and differentiating capacity into different types of tumor cells. The intricate molecular mechanism is necessary to elucidate CSC's chemoresistance properties and cancer recurrence. Establishing efficient strategies for CSC maintenance and enrichment is essential to elucidate the mechanisms and properties of CSCs and CSC-related therapeutic measures. Current approaches are insufficient to mimic the in vivo chemical and physical conditions for the maintenance and growth of CSC and yield unreliable research results. Biomaterials are now widely used for simulating the bone marrow microenvironment. Biomaterial-based three-dimensional (3D) approaches for the enrichment of CSC provide an excellent promise for future drug discovery and elucidation of molecular mechanisms. In the future, the biomaterial-based model will contribute to a more operative and predictive CSC model for cancer therapy. Design strategies for materials, physicochemical cues, and morphology will offer a new direction for future modification and new methods for studying the CSC microenvironment and its chemoresistance property. This review highlights the critical roles of the microenvironmental cues that regulate CSC function and endow them with drug resistance properties. This review also explores the latest advancement and challenges in biomaterial-based scaffold structure for therapeutic approaches against CSC chemoresistance. Since the recent entry of extracellular vesicles (EVs), cell-derived nanostructures, have opened new avenues of investigation into this field, which, together with other more conventionally studied signaling pathways, play an important role in cell-to-cell communication. Thus, this review further explores the subject of EVs in-depth. This review also discusses possible future biomaterial and biomaterial-EV-based models that could be used to study the tumor microenvironment (TME) and will provide possible therapeutic approaches. Finally, this review concludes with potential perspectives and conclusions in this area.

Extracellular matrix mechanobiology in cancer cell migration

The extracellular matrix (ECM) is pivotal in modulating tumor progression. Besides chemically stimulating tumor cells, it also offers physical support that orchestrates the sequence of events in the metastatic cascade upon dynamically modulating cell mechanosensation. Understanding this translation between matrix biophysical cues and intracellular signaling has led to rapid growth in the interdisciplinary field of cancer mechanobiology in the last decade. Substantial efforts have been made to develop novel in vitro tumor mimicking platforms to visualize and quantify the mechanical forces within the tissue that dictate tumor cell invasion and metastatic growth. This review highlights recent findings on tumor matrix biophysical cues such as fibrillar arrangement, crosslinking density, confinement, rigidity, topography, and non-linear mechanics and their implications on tumor cell behavior. We also emphasize how perturbations in these cues alter cellular mechanisms of mechanotransduction, consequently enhancing malignancy. Finally, we elucidate engineering techniques to individually emulate the mechanical properties of tumors that could help serve as toolkits for developing and testing ECM-targeted therapeutics on novel bioengineered tumor platforms. STATEMENT OF SIGNIFICANCE: Disrupted ECM mechanics is a driving force for transitioning incipient cells to life-threatening malignant variants. Understanding these ECM changes can be crucial as they may aid in developing several efficacious drugs that not only focus on inducing cytotoxic effects but also target specific matrix mechanical cues that support and enhance tumor invasiveness. Designing and implementing an optimal tumor mimic can allow us to predictively map biophysical cue-modulated cell behaviors and facilitate the design of improved lab-grown tumor models with accurately controlled structural features. This review focuses on the abnormal changes within the ECM during tumorigenesis and its implications on tumor cell-matrix mechanoreciprocity. Additionally, it accentuates engineering approaches to produce ECM features of varying levels of complexity which is critical for improving the efficiency of current engineered tumor tissue models.

Exploring Amodiaquine's Repurposing Potential in Breast Cancer Treatment-Assessment of In-Vitro Efficacy & Mechanism of Action

Due to the heterogeneity of breast cancer, current available treatment options are moderately effective at best. Hence, it is highly recommended to comprehend different subtypes, understand pathogenic mechanisms involved, and develop treatment modalities. The repurposing of an old FDA approved anti-malarial drug, amodiaquine (AQ) presents an outstanding opportunity to explore its efficacy in treating majority of breast cancer subtypes. Cytotoxicity, scratch assay, vasculogenic mimicry study, and clonogenic assay were employed to determine AQ's ability to inhibit cell viability, cell migration, vascular formation, and colony growth. 3D Spheroid cell culture studies were performed to identify tumor growth inhibition potential of AQ in MCF-7 and MDAMB-231 cell lines. Apoptosis assays, cell cycle analysis, RT-qPCR assays, and Western blot studies were performed to determine AQ's ability to induce apoptosis, cell cycle changes, gene expression changes, and induction of autophagy marker proteins. The results from in-vitro studies confirmed the potential of AQ as an anti-cancer drug. In different breast cancer cell lines tested, AQ significantly induces cytotoxicity, inhibit colony formation, inhibit cell migration, reduces 3D spheroid volume, induces apoptosis, blocks cell cycle progression, inhibit expression of cancer related genes, and induces LC3BII protein to inhibit autophagy. Our results demonstrate that amodiaquine is a promising drug to repurpose for breast cancer treatment, which needs numerous efforts from further studies.

3D Multicellular Tumor Spheroids in a Microfluidic Droplet System for Investigation of Drug Resistance

A three-dimensional (3D) tumor spheroid model plays a critical role in mimicking tumor microenvironments in vivo. However, the conventional culture methods lack the ability to manipulate the 3D tumor spheroids in a homogeneous manner. To address this limitation, we developed a microfluidic-based droplet system for drug screening applications. We used a tree-shaped gradient generator to control the cell density and encapsulate the cells within uniform-sized droplets to generate a 3D gradient-sized tumor spheroid. Using this microfluidic-based droplet system, we demonstrated the high-throughput generation of uniform 3D tumor spheroids containing various cellular ratios for the analysis of the anti-cancer drug cytotoxicity. Consequently, this microfluidic-based gradient droplet generator could be a potentially powerful tool for anti-cancer drug screening applications.

Targeting Cellular Components of the Tumor Microenvironment in Solid Malignancies

Simple Summary

The tumor microenvironment comprises numerous different cellular players that engage transformed cancer cells and may exert pro- vs anti-tumor functions. Their crosstalk, functionality, as well as cell recruitment to cancer lesions, is chiefly dictated by cytokines/chemokines-receptor pairs and these axes can represent therapeutic vulnerabilities—as for immune checkpoint blockers. In this review, we recapitulate the main drivers of cellular TME dynamics, interactions, and functionality, mainly focusing on T lymphocytes, macrophages and cancer associated fibroblasts, also providing an outlook on state-of-the-art TME-targeting agents.

Abstract

Cancers are composed of transformed cells, characterized by aberrant growth and invasiveness, in close relationship with non-transformed healthy cells and stromal tissue. The latter two comprise the so-called tumor microenvironment (TME), which plays a key role in tumorigenesis, cancer progression, metastatic seeding, and therapy resistance. In these regards, cancer-TME interactions are complex and dynamic, with malignant cells actively imposing an immune-suppressive and tumor-promoting state on surrounding, non-transformed, cells. Immune cells (both lymphoid and myeloid) can be recruited from the circulation and/or bone marrow by means of chemotactic signals, and their functionality is hijacked upon arrival at tumor sites. Molecular characterization of tumor-TME interactions led to the introduction of novel anti-cancer therapies targeting specific components of the TME, such as immune checkpoint blockers (ICB) (i.e., anti-programmed death 1, anti-PD1; anti-Cytotoxic T-Lymphocyte Antigen 4, anti-CTLA4). However, ICB resistance often develops and, despite the introduction of newer technologies able to study the TME at the single-cell level, a detailed understanding of all tumor-TME connections is still largely lacking. In this work, we highlight the main cellular and extracellular components of the TME, discuss their dynamics and functionality, and provide an outlook on the most relevant clinical data obtained with novel TME-targeting agents, with a focus on T lymphocytes, macrophages, and cancer-associated fibroblasts.

Three-Dimensional 3D Culture Models in Gynecological and Breast Cancer Research

Traditional two-dimensional (2D) monolayer cell cultures have long been the gold standard for cancer biology research. However, their ability to accurately reflect the molecular mechanisms of tumors occurring in vivo is limited. Recent development of three-dimensional (3D) cell culture models facilitate the possibility to better recapitulate several of the biological and molecular characteristics of tumors in vivo, such as cancer cells heterogeneity, cell-extracellular matrix interactions, development of a hypoxic microenvironment, signaling pathway activities depending on contacts with extracellular matrix, differential growth kinetics, more accurate drugs response, and specific gene expression and epigenetic patterns. In this review, we discuss the utilization of different types of 3D culture models including spheroids, organotypic models and patient-derived organoids in gynecologic cancers research, as well as its potential applications in oncological research mainly for screening drugs with major physiological and clinical relevance. Moreover, microRNAs regulation of cancer hallmarks in 3D cell cultures from different types of cancers is discussed.

The Patient-Derived Cancer Organoids: Promises and Challenges as Platforms for Cancer Discovery

The cancer burden is rapidly increasing in most countries, and thus, new anticancer drugs for effective cancer therapy must be developed. Cancer model systems that recapitulate the biological processes of human cancers are one of the cores of the drug development process. PDCO has emerged as a unique model that preserves the genetic, physiological, and histologic characteristics of original cancer, including inter- and intratumoral heterogeneities. Due to these advantages, the PCDO model is increasingly investigated for anticancer drug screening and efficacy testing, preclinical patient stratification, and precision medicine for selecting the most effective anticancer therapy for patients. Here, we review the prospects and limitations of PDCO compared to the conventional cancer models. With advances in culture success rates, co-culture systems with the tumor microenvironment, organoid-on-a-chip technology, and automation technology, PDCO will become the most promising model to develop anticancer drugs and precision medicine.

In Vitro Cancer Models: A Closer Look at Limitations on Translation

In vitro cancer models are envisioned as high-throughput screening platforms for potential new therapeutic discovery and/or validation. They also serve as tools to achieve personalized treatment strategies or real-time monitoring of disease propagation, providing effective treatments to patients. To battle the fatality of metastatic cancers, the development and commercialization of predictive and robust preclinical in vitro cancer models are of urgent need. In the past decades, the translation of cancer research from 2D to 3D platforms and the development of diverse in vitro cancer models have been well elaborated in an enormous number of reviews. However, the meagre clinical success rate of cancer therapeutics urges the critical introspection of currently available preclinical platforms, including patents, to hasten the development of precision medicine and commercialization of in vitro cancer models. Hence, the present article critically reflects the difficulty of translating cancer therapeutics from discovery to adoption and commercialization in the light of in vitro cancer models as predictive tools. The state of the art of in vitro cancer models is discussed first, followed by identifying the limitations of bench-to-bedside transition. This review tries to establish compatibility between the current findings and obstacles and indicates future directions to accelerate the market penetration, considering the niche market.

Cancer-Associated Fibroblasts: Mechanisms of Tumor Progression and Novel Therapeutic Targets

Simple Summary

The tumor microenvironment plays an important role in determining the biological behavior of several of the more aggressive malignancies. Among the various cell types evident in the tumor “field”, cancer-associated fibroblasts (CAFs) are a heterogenous collection of activated fibroblasts secreting a wide repertoire of factors that regulate tumor development and progression, inflammation, drug resistance, metastasis and recurrence. Insensitivity to chemotherapeutics and metastatic spread are the major contributors to cancer patient mortality. This review discusses the complex interactions between CAFs and the various populations of normal and neoplastic cells that interact within the dynamic confines of the tumor microenvironment with a focus on the involved pathways and genes.

Abstract

Cancer-associated fibroblasts (CAFs) are a heterogenous population of stromal cells found in solid malignancies that coexist with the growing tumor mass and other immune/nonimmune cellular elements. In certain neoplasms (e.g., desmoplastic tumors), CAFs are the prominent mesenchymal cell type in the tumor microenvironment, where their presence and abundance signal a poor prognosis in multiple cancers. CAFs play a major role in the progression of various malignancies by remodeling the supporting stromal matrix into a dense, fibrotic structure while secreting factors that lead to the acquisition of cancer stem-like characteristics and promoting tumor cell survival, reduced sensitivity to chemotherapeutics, aggressive growth and metastasis. Tumors with high stromal fibrotic signatures are more likely to be associated with drug resistance and eventual relapse. Clarifying the molecular basis for such multidirectional crosstalk among the various normal and neoplastic cell types present in the tumor microenvironment may yield novel targets and new opportunities for therapeutic intervention. This review highlights the most recent concepts regarding the complexity of CAF biology including CAF heterogeneity, functionality in drug resistance, contribution to a progressively fibrotic tumor stroma, the involved signaling pathways and the participating genes.

Organ on Chip Technology to Model Cancer Growth and Metastasis

Organ on chip (OOC) has emerged as a major technological breakthrough and distinct model system revolutionizing biomedical research and drug discovery by recapitulating the crucial structural and functional complexity of human organs in vitro. OOC are rapidly emerging as powerful tools for oncology research. Indeed, Cancer on chip (COC) can ideally reproduce certain key aspects of the tumor microenvironment (TME), such as biochemical gradients and niche factors, dynamic cell-cell and cell-matrix interactions, and complex tissue structures composed of tumor and stromal cells. Here, we review the state of the art in COC models with a focus on the microphysiological systems that host multicellular 3D tissue engineering models and can help elucidate the complex biology of TME and cancer growth and progression. Finally, some examples of microengineered tumor models integrated with multi-organ microdevices to study disease progression in different tissues will be presented.

Strategies Using Gelatin Microparticles for Regenerative Therapy and Drug Screening Applications

Gelatin, a denatured form of collagen, is an attractive biomaterial for biotechnology. In particular, gelatin particles have been noted due to their attractive properties as drug carriers. The drug release from gelatin particles can be easily controlled by the crosslinking degree of gelatin molecule, responding to the purpose of the research. The gelatin particles capable of drug release are effective in wound healing, drug screening models. For example, a sustained release of growth factors for tissue regeneration at the injured sites can heal a wound. In the case of the drug screening model, a tissue-like model composed of cells with high activity by the sustained release of drug or growth factor provides reliable results of drug effects. Gelatin particles are effective in drug delivery and the culture of spheroids or cell sheets because the particles prevent hypoxia-derived cell death. This review introduces recent research on gelatin microparticles-based strategies for regenerative therapy and drug screening models.

Cancer-Associated Fibroblast Functions as a Road-Block in Cancer Therapy

Simple Summary

An overwhelming percentage of deaths in solid tumors are caused by treatment failure due to the disease’s unresponsiveness when tumor cells tolerate treatment. Aggressive cancer contains tumors cells that are surrounded by many other non-tumor cells, including fibroblasts cells. These fibroblasts near tumor cells are converted by the tumor cells into specialized fibroblasts called cancer-associated fibroblasts that favor the growth of tumors. This review examines how cancer-associated fibroblasts interact with tumor cells, immune cells, and endothelial cells in aiding and abetting the development of resistance to different types of cancer therapy. As cancer-associated fibroblasts’ function blocks the road to recovery, we need to neutralize their function for the clinical management of the disease to be successful. The knowledge about the role of cancer-associated fibroblasts in resisting therapy is fundamental to design an appropriate remedy to counteract drug resistance and improve the outcome of the disease.

Abstract

The journey of a normal resident fibroblast belonging to the tumor microenvironment (TME) from being a tumor pacifier to a tumor patron is fascinating. We introduce cancer-associated fibroblast (CAF) as a crucial component of the TME. Activated-CAF partners with tumor cells and all components of TME in an established solid tumor. We briefly overview the origin, activation, markers, and overall functions of CAF with a particular reference to how different functions of CAF in an established tumor are functionally connected to the development of resistance to cancer therapy in solid tumors. We interrogate the role of CAF in mediating resistance to different modes of therapies. Functional diversity of CAF in orchestrating treatment resistance in solid tumors portrays CAF as a common orchestrator of treatment resistance; a roadblock in cancer therapy

Bioengineering a humanized 3D tri-culture osteosarcoma model to assess tumor invasiveness and therapy response

To date, anticancer therapies with evidenced efficacy in preclinical models fail during clinical trials. The shortage of robust drug screening platforms that accurately predict patient's response underlie these misleading results. To provide a reliable platform for tumor drug discovery, we herein propose a relevant humanized 3D osteosarcoma (OS) model exploring the potential of methacryloyl platelet lysates (PLMA)-based hydrogels to sustain spheroid growth and invasion. The architecture and synergistic cell-microenvironment interaction of an invading tumor was recapitulated encapsulating spheroids in PLMA hydrogels, alone or co-cultured with osteoblasts and mesenchymal stem cells. The stem cells alignment toward OS spheroid suggested that tumor cells chemotactically attracted the surrounding stromal cells, which supported tumor growth and invasion into the hydrogels. The exposure of established models to doxorubicin revealed an improved drug resistance of PLMA-based models, comparing with scaffold-free spheroids. The proposed OS models highlighted the feasibility of PLMA hydrogels to support tumor invasion and recapitulate tumor-stromal cell crosstalk, demonstrating the potential of this 3D platform for complex tumor modelling. STATEMENT OF SIGNIFICANCE: Cell invasion mechanisms involved in tumor progression have been recapitulated in the field of 3D in vitro modeling, leveraging the great advance in biomimetic materials. In line with the growing interest in human-derived biomaterials, the aim of this study is to explore for the first time the potential of methacryloyl platelet lysates (PLMA)-based hydrogels to develop a humanized 3D osteosarcoma model to assess tumor invasiveness and drug sensitivity. By co-culturing tumor spheroids with human osteoblasts and human mesenchymal stem cells, this study demonstrated the importance of the synergistic tumor cell-microenvironment interaction in tumor growth, invasion and drug resistance. The established 3D osteosarcoma model highlighted the feasibility of PLMA hydrogels as a relevant 3D platform for complex tumor modelling.

Heterogeneous microenvironmental stiffness regulates pro-metastatic functions of breast cancer cells

Besides molecular and phenotypic variations observed in cancer cells, intratumoral heterogeneity also occurs in the tumor microenvironment. Correlative stiffness maps of different intratumor locations in breast tumor biopsies show that stiffness increases from core to periphery. However, how different local ECM stiffness regulates key functions of cancer cells in tumor progression remains unclear. Although increased tissue stiffness is an established driver of breast cancer progression, conclusions from 2D cultures do not correspond with newer data from cancer cells in 3D environments. Many past studies of breast cancer in 3D culture fail to recapitulate the stiffness of a real breast tumor or the various local stiffnesses present in a tumor microenvironment. In this study, we developed a series of collagen/alginate hybrid hydrogels with adjustable stiffness to match the core, middle, and peripheral zones of a breast tumor. We used this hydrogel system to investigate effects of different local stiffness on morphology, proliferation, and migration of breast cancer cells. RNA sequencing of cells in hydrogels with different stiffness revealed changes in multiple cellular processes underlying cancer progression, including angiogenesis and metabolism. We discovered that tumor cells in a soft environment enriched YAP1 and AP1 signaling related genes, whereas tumor cells in a stiff environment became more pro-angiogenic by upregulating fibronectin 1 (FN1) and matrix metalloproteinase 9 (MMP9) expression. This systematic study defines how the range of environmental stiffnesses present in a breast tumor regulates cancer cells, providing new insights into tumorigenesis and disease progression at the tumor-stroma interface. STATEMENT OF SIGNIFICANCE: Applied a well-defined hybrid hydrogel system to mimic the tumor microenvironment with heterogeneous local stiffness. Breast cancer cells tended to proliferate in soft core environment while migrate in stiff peripheral environment. Breast cancer cells shift from glycolysis to OXPHOS and fatty acid metabolism responding to stiff matrix microenvironment. The transcriptomic profile of breast cancer cells altered due to microenvironmental stiffness changes.

Breast Cancer Reconstruction: Design Criteria for a Humanized Microphysiological System

International regulatory agencies such as the Food and Drug Administration have mandated that the scientific community develop humanized microphysiological systems (MPS) as an in vitro alternative to animal models in the near future. While the breast cancer research community has long appreciated the importance of three-dimensional growth dynamics in their experimental models, there are remaining obstacles preventing a full conversion to humanized MPS for drug discovery and pathophysiological studies. This perspective evaluates the current status of human tissue-derived cells and scaffolds as building blocks for an "idealized" breast cancer MPS based on bioengineering design principles. It considers the utility of adipose tissue as a potential source of endothelial, lymphohematopoietic, and stromal cells for the support of breast cancer epithelial cells. The relative merits of potential MPS scaffolds derived from adipose tissue, blood components, and synthetic biomaterials is evaluated relative to the current "gold standard" material, Matrigel, a murine chondrosarcoma-derived basement membrane-enriched hydrogel. The advantages and limitations of a humanized breast cancer MPS are discussed in the context of in-process and destructive read-out assays. Impact statement Regulatory authorities have highlighted microphysiological systems as an emerging tool in breast cancer research. This has been led by calls for more predictive human models and reduced animal experimentation. This perspective describes how human-derived cells, extracellular matrices, and hydrogels will provide the building blocks to create breast cancer models that accurately reflect diversity at multiple levels, that is, patient ethnicity, pathophysiology, and metabolic status.

Breast tumor-on-chip models: From disease modeling to personalized drug screening

Breast cancer is one of the leading causes of mortality worldwide being the most common cancer among women. Despite the significant progress obtained during the past years in the understanding of breast cancer pathophysiology, women continue to die from it. Novel tools and technologies are needed to develop better diagnostic and therapeutic approaches, and to better understand the molecular and cellular players involved in the progression of this disease. Typical methods employed by the pharmaceutical industry and laboratories to investigate breast cancer etiology and evaluate the efficiency of new therapeutic compounds are still based on traditional tissue culture flasks and animal models, which have certain limitations. Recently, tumor-on-chip technology emerged as a new generation of in vitro disease model to investigate the physiopathology of tumors and predict the efficiency of drugs in a native-like microenvironment. These microfluidic systems reproduce the functional units and composition of human organs and tissues, and importantly, the rheological properties of the native scenario, enabling precise control over fluid flow or local gradients. Herein, we review the most recent works related to breast tumor-on-chip for disease modeling and drug screening applications. Finally, we critically discuss the future applications of this emerging technology in breast cancer therapeutics and drug development.

Employing hydrogels in tissue engineering approaches to boost conventional cancer-based research and therapies

Cancer is a complicated disease that involves the efforts of researchers to introduce and investigate novel successful treatments. Traditional cancer therapy approaches, especially chemotherapy, are prone to possible systemic side effects, such as the dysfunction of liver or kidney, neurological side effects and a decrease of bone marrow activity. Hydrogels, along with tissue engineering techniques, provide tremendous potential for scientists to overcome these issues through the release of drugs at the site of tumor. Hydrogels demonstrated competency as potent and stimulus-sensitive drug delivery systems for tumor removal, which is attributed to their unique features, including high water content, biocompatibility, and biodegradability. In addition, hydrogels have gained more attention as 3D models for easier and faster screening of cancer and tumors due to their potential in mimicking the extracellular matrix. Hydrogels as a reservoir can be loaded by an effective dosage of chemotherapeutic agents, and then deliver them to targets. In comparison to conventional procedures, hydrogels considerably decreased the total cost, duration of research, and treatment time. This study provides a general look into the potential role of hydrogels as a powerful tool to augment cancer studies for better analysis of cancerous cell functions, cell survival, angiogenesis, metastasis, and drug screening. Moreover, the upstanding application of drug delivery systems related to the hydrogel in order to sustain the release of desired drugs in the tumor cell-site were explored.

Perfusion Flow Enhances Viability and Migratory Phenotype in 3D-Cultured Breast Cancer Cells

Conventional 2D cell culture, a traditional tool in pre-clinical studies, can hardly be regarded as a representation of a natural cell microenvironment. In this respect, it might result in altered cellular behaviors. To overcome such a limitation, different approaches have been tested to conduct more representative in vitro studies. In particular, the use of 3D cell culture introduces variables, such as cell-cell and cell-extracellular matrix interactions; cell features such as survival, proliferation and migration are consequently influenced. For an example, an enhanced drug resistance and increased invasiveness are shown by cancer cells when cultured in 3D versus 2D conventional culture models. In this setting however, non-uniform cell distribution and biological behaviors appear throughout the scaffold, due to reduced diffusion of oxygen and nutrients. Perfusion in bioreactor systems can be used to improve medium transport. In this line of reasoning, this study proposes a breast cancer cell culture model sustained by an integrated approach that couples a 3D environment and a fluid perfusion. This model improves viability and uniformness of cell distribution, while inducing morphological, functional and molecular cancer cell remodeling.

Proteinaceous Hydrogels for Bioengineering Advanced 3D Tumor Models

The establishment of tumor microenvironment using biomimetic in vitro models that recapitulate key tumor hallmarks including the tumor supporting extracellular matrix (ECM) is in high demand for accelerating the discovery and preclinical validation of more effective anticancer therapeutics. To date, ECM-mimetic hydrogels have been widely explored for 3D in vitro disease modeling owing to their bioactive properties that can be further adapted to the biochemical and biophysical properties of native tumors. Gathering on this momentum, herein the current landscape of intrinsically bioactive protein and peptide hydrogels that have been employed for 3D tumor modeling are discussed. Initially, the importance of recreating such microenvironment and the main considerations for generating ECM-mimetic 3D hydrogel in vitro tumor models are showcased. A comprehensive discussion focusing protein, peptide, or hybrid ECM-mimetic platforms employed for modeling cancer cells/stroma cross-talk and for the preclinical evaluation of candidate anticancer therapies is also provided. Further development of tumor-tunable, proteinaceous or peptide 3D microtesting platforms with microenvironment-specific biophysical and biomolecular cues will contribute to better mimic the in vivo scenario, and improve the predictability of preclinical screening of generalized or personalized therapeutics.

Recent Advances in Three-Dimensional Multicellular Spheroid Culture and Future Development

Three-dimensional multicellular spheroids (MCSs) have received extensive attention in the field of biomedicine due to their ability to simulate the structure and function of tissues in vivo more accurately than traditional in vitro two-dimensional models and to simulate cell-cell and cell extracellular matrix (ECM) interactions. It has become an important in vitro three-dimensional model for tumor research, high-throughput drug screening, tissue engineering, and basic biology research. In the review, we first summarize methods for MCSs generation and their respective advantages and disadvantages and highlight the advances of hydrogel and microfluidic systems in the generation of spheroids. Then, we look at the application of MCSs in cancer research and other aspects. Finally, we discuss the development direction and prospects of MCSs.

Environmental control of mammary carcinoma cell expansion by acidification and spheroid formation in vitro

Breast cancer is the leading cause of cancer death among women worldwide. Like other cancers, mammary carcinoma progression involves acidification of the tumor microenvironment, which is an important factor for cancer detection and treatment strategies. However, the effects of acidity on mammary carcinoma cell morphology and phenotype have not been thoroughly characterized. Here, we evaluated fundamental effects of environmental acidification on mammary carcinoma cells in standard two-dimensional cultures and three-dimensional spheroids. Acidification decreased overall mammary carcinoma cell viability, while increasing their resistance to the anthracycline doxorubicin. Environmental acidification also increased extracellular vesicle production by mammary carcinoma cells. Conditioned media containing these vesicles appeared to increase fibroblast motility. Acidification also increased mammary carcinoma cell motility when cultured with fibroblasts in spheroids. Taken together, results from this study suggest that environmental acidification induces drug resistance and extracellular vesicle production by mammary carcinoma cells that promote tumor expansion.

A new drug testing platform based on 3D tri-culture in lab-on-a-chip devices

Drug discovery has a 90% rate of failure because preclinical platforms for drug testing do not mimic the in vivo conditions. Doxorubicin (DOX) is a commonly used drug to treat breast cancer patients even though it has side effects. Lab-on-a-chip (LOC) devices provide spatial control at the micrometer scale and can thus emulate the cancer microenvironment. Here, using a multidisciplinary approach, a new drug testing platform based on 3D tri-culture in LOC devices was developed. Breast cancer cells alone or with normal mammary epithelial cells and macrophages were cultured in matrigel in LOC devices. The platform was used to test DOX and (R)-4'-methylklavuzon (KLA), which is a new anti-cancer drug candidate. Results showed that DOX and KLA were equally effective on breast cancer cells in 3D monoculture. KLA produced 26% less death for breast cancer cells than DOX in 3D tri-culture. More importantly, DOX was not selective between breast cancer cells and normal mammary epithelial cells in 3D tri- culture whereas KLA caused 56% less cell death than DOX for normal mammary epithelial cells. Results strongly recommend that 3D tri-culture in LOC devices be used for assessment of drug toxicity at the preclinical stage.

Organotypic Modeling of the Tumor Landscape

Cancer is a complex disease and it is now clear that not only epithelial tumor cells play a role in carcinogenesis. The tumor microenvironment is composed of non-stromal cells, including endothelial cells, adipocytes, immune and nerve cells, and a stromal compartment composed of extracellular matrix, cancer-associated fibroblasts and mesenchymal cells. Tumorigenesis is a dynamic process with constant interactions occurring between the tumor cells and their surroundings. Even though all connections have not yet been discovered, it is now known that crosstalk between actors of the microenvironment drives cancer progression. Taking into account this complexity, it is important to develop relevant models to study carcinogenesis. Conventional 2D culture models fail to represent the entire tumor microenvironment properly and the use of animal models should be decreased with respect to the 3Rs rule. To this aim, in vitro organotypic models have been significantly developed these past few years. These models have different levels of complexity and allow the study of tumor cells alone or in interaction with the microenvironment actors during the multiple stages of carcinogenesis. This review depicts recent insights into organotypic modeling of the tumor and its microenvironment all throughout cancer progression. It offers an overview of the crosstalk between epithelial cancer cells and their microenvironment during the different phases of carcinogenesis, from the early cell autonomous events to the late metastatic stages. The advantages of 3D over classical 2D or in vivo models are presented as well as the most promising organotypic models. A particular focus is made on organotypic models used for studying cancer progression, from the less complex spheroids to the more sophisticated body-on-a-chip. Last but not least, we address the potential benefits of these models in personalized medicine which is undoubtedly a domain paving the path to new hopes in terms of cancer care and cure.

Three-Dimensional Culture System of Cancer Cells Combined with Biomaterials for Drug Screening

Simple Summary

For the research and development of drug discovery, it is of prime importance to construct the three-dimensional (3D) tissue models in vitro. To this end, the enhancement design of cell function and activity by making use of biomaterials is essential. In this review, 3D culture systems of cancer cells combined with several biomaterials for anticancer drug screening are introduced.

Abstract

Anticancer drug screening is one of the most important research and development processes to develop new drugs for cancer treatment. However, there is a problem resulting in gaps between the in vitro drug screening and preclinical or clinical study. This is mainly because the condition of cancer cell culture is quite different from that in vivo. As a trial to mimic the in vivo cancer environment, there has been some research on a three-dimensional (3D) culture system by making use of biomaterials. The 3D culture technologies enable us to give cancer cells an in vitro environment close to the in vivo condition. Cancer cells modified to replicate the in vivo cancer environment will promote the biological research or drug discovery of cancers. This review introduces the in vitro research of 3D cell culture systems with biomaterials in addition to a brief summary of the cancer environment.

Uptake, distribution and radio-enhancement effects of gold nanoparticles in tumor microtissues

Radiotherapy is an integral and highly effective part of cancer therapy, applicable in over 50% of patients affected by cancer. Due to the low specificity of the X-ray irradiation, the maximal radiation dose is greatly limited in order to avoid damage to surrounding healthy tissue. The limitations in applicable dose oftentimes result in the survival of a subpopulation of radio-resistant cells that then cause cancer reoccurence. Approaches based on tumor-targeted high atomic number inorganic nanoparticles have been proposed to locally increase the photoelectric absorption cross-section of tumors relative to healthy tissue. However, the complex interplay between the nanoparticle radio-enhancers and the tumor tissue has led to poor translation of in vitro findings to (pre)clinics. Here, we report the development of a tumor microtissue model along with analytical imaging for the quantitative assessment of nanoparticle-based radio-enhancement as a function of nanoparticle size, uptake and intratissural distribution. The advanced in vitro model exhibits key features of cancerous tissues, including diminished susceptibility to drugs and attenuated response to nanoparticle treatment compared to corresponding conventional 2D cell cultures. Whereas radio-enhancement effects between 2D and 3D cell cultures were comparable for 5 nm gold particles, the limited penetration of 50 nm gold nanoparticles into 3D microtissues led to a significantly reduced radio-enhancement effect in 3D compared to 2D. Taken together, tumor microtissues, which in stark contrast to 2D cell culture exhibit tissue-like features, may provide a valuable high-throughput intermediate pre-selection step in the preclinical translation of nanoparticle-based radio-enhancement therapy designs.

Alzheimer's Disease, and Breast and Prostate Cancer Research: Translational Failures and the Importance to Monitor Outputs and Impact of Funded Research

Dementia and cancer are becoming increasingly prevalent in Western countries. In the last two decades, research focused on Alzheimer's disease (AD) and cancer, in particular, breast cancer (BC) and prostate cancer (PC), has been substantially funded both in Europe and worldwide. While scientific research outcomes have contributed to increase our understanding of the disease etiopathology, still the prevalence of these chronic degenerative conditions remains very high across the globe. By definition, no model is perfect. In particular, animal models of AD, BC, and PC have been and still are traditionally used in basic/fundamental, translational, and preclinical research to study human disease mechanisms, identify new therapeutic targets, and develop new drugs. However, animals do not adequately model some essential features of human disease; therefore, they are often unable to pave the way to the development of drugs effective in human patients. The rise of new technological tools and models in life science, and the increasing need for multidisciplinary approaches have encouraged many interdisciplinary research initiatives. With considerable funds being invested in biomedical research, it is becoming pivotal to define and apply indicators to monitor the contribution to innovation and impact of funded research. Here, we discuss some of the issues underlying translational failure in AD, BC, and PC research, and describe how indicators could be applied to retrospectively measure outputs and impact of funded biomedical research.

Characterization of Triple-Negative Breast Cancer MDA-MB-231 Cell Spheroid Model

Background

The tumor three-dimensional (3D) spheroid model in vitro is effective on detecting malignant cells and tumorigenesis, and assessing drug resistance. Compared with two-dimensional (2D) monolayer culture, breast cancer (BC) spheroids more accurately reflect the complex microenvironment in vivo, which have been extensively reported in BC research. MDA-MB-231 cells, the triple-negative breast cancer (TNBC) cell line, display representative epithelial to mesenchymal transition (EMT) associated with BC metastasis. However, the characterization of MDA-MB-231 spheroids has been largely unknown at present, which requires further attention.

Materials and Methods

Microwell array was conducted for the formation of MDA-MB-231 spheroids. In addition, H&E staining, immunohistochemistry (IHC), CellTiter-Glo^® 3D cell viability assay, and flow cytometry were performed to investigate the structure and growth characteristics. Besides, Transwell and scratch healing assays were carried out to detect the migratory capacities compared with 2D culture. Western blotting and confocal fluorescence were selected to detect the expression of EMT-associated proteins. Additionally, the half maximal inhibitory concentration (IC₅₀) values of antitumor compounds Carboplatin and Doxorubicin were measured to assess drug resistance.

Results

The MDA-MB-231 spheroids were viable, which maintained a compact structure with zonation features for up to 9 days. Moreover, those spheroids had a slower growth rate than those cultured as a monolayer and differential zones of proliferation. The migratory capacities were significantly enhanced by transferring the spheroids to 2D adherent culture. Compared with 2D culture, the levels of EMT-associated proteins were significantly up-regulated in spheroids. Furthermore, toxicity assessment showed that spheroids exhibited an increased resistance to the antitumor compounds.

Conclusion

This study develops the simple spheroids and demonstrates their structure, growth and proliferation characteristics. According to our results, the spheroids are associated with superior EMT and high resistance to toxicological response compared with the standard 2D monocultures.

Mitigation strategies for reducing air pollution

Today, it is increasingly recognized that air pollution hurts human health. Consequently, efficient mitigation strategies need to be implemented for substantial environmental and health co-benefits. A valid approach to reducing the air pollution effects on the environment and human health is proposed. Specific guidelines have been elucidated by differentiating them on the base of the final stakeholders (citizens, enterprises, and public authorities), of the emission sources (transport, household energy, industry, and energy generation sector, agriculture, and shipping area), and of the field of implementation (urban and extra-urban context). This paper can provide useful information for governments for the implementation of a strategic plan focused on emphasizing multi-pollutant emission reductions and overall air pollution-related risk.

Breast cancer models: Engineering the tumor microenvironment

The mechanisms behind cancer initiation and progression are not clear. Therefore, development of clinically relevant models to study cancer biology and drug response in tumors is essential. In vivo models are very valuable tools for studying cancer biology and for testing drugs; however, they often suffer from not accurately representing the clinical scenario because they lack either human cells or a functional immune system. On the other hand, two-dimensional (2D) in vitro models lack the three-dimensional (3D) network of cells and extracellular matrix (ECM) and thus do not represent the tumor microenvironment (TME). As an alternative approach, 3D models have started to gain more attention, as such models offer a platform with the ability to study cell-cell and cell-material interactions parametrically, and possibly include all the components present in the TME. Here, we first give an overview of the breast cancer TME, and then discuss the current state of the pre-clinical breast cancer models, with a focus on the engineered 3D tissue models. We also highlight two engineering approaches that we think are promising in constructing models representative of human tumors: 3D printing and microfluidics. In addition to giving basic information about the TME in the breast tissue, this review article presents the state-of-the-art tissue engineered breast cancer models. STATEMENT OF SIGNIFICANCE: Involvement of biomaterials and tissue engineering fields in cancer research enables realistic mimicry of the cell-cell and cell-extracellular matrix (ECM) interactions in the tumor microenvironment (TME), and thus creation of better models that reflect the tumor response against drugs. Engineering the 3D in vitro models also requires a good understanding of the TME. Here, an overview of the breast cancer TME is given, and the current state of the pre-clinical breast cancer models, with a focus on the engineered 3D tissue models is discussed. This review article is useful not only for biomaterials scientists aiming to engineer 3D in vitro TME models, but also for cancer researchers willing to use these models for studying cancer biology and drug testing.

Integrated Biophysical Characterization of Fibrillar Collagen-Based Hydrogels

This paper describes an experimental characterization scheme of the biophysical properties of reconstituted hydrogel matrices based on indentation testing, quantification of transport via microfluidics, and confocal reflectance microscopy analysis. While methods for characterizing hydrogels exist and are widely used, they often do not measure diffusive and convective transport concurrently, determine the relationship between microstructure and transport properties, and decouple matrix mechanics and transport properties. Our integrated approach enabled independent and quantitative measurements of the structural, mechanical, and transport properties of hydrogels in a single study. We used fibrillar type I collagen as the base matrix and investigated the effects of two different matrix modifications: (1) cross-linking with human recombinant tissue transglutaminase II (hrTGII) and (2) supplementation with the nonfibrillar matrix constituent hyaluronic acid (HA). hrTGII modified the matrix structure and transport but not mechanical parameters. Furthermore, changes in the matrix structure due to hrTGII were seen to be dependent on the concentration of collagen. In contrast, supplementation of HA at different collagen concentrations altered the matrix microstructure and mechanical indentation behavior but not transport parameters. These experimental observations reveal the important relationship between extracellular matrix (ECM) composition and biophysical properties. The integrated techniques are versatile, robust, and accessible; and as matrix-cell interactions are instrumental for many biological processes, the methods and findings described here should be broadly applicable for characterizing hydrogel materials used for three-dimensional (3-D) tissue-engineered culture models.

Current status and contemporary approaches to the discovery of antitumor agents from higher plants

Higher plant constituents have afforded clinically available anticancer drugs. These include both chemically unmodified small molecules and their synthetic derivatives currently used or those in clinical trials as antineoplastic agents, and an updated summary is provided. In addition, botanical dietary supplements, exemplified by mangosteen and noni constituents, are also covered as potential cancer chemotherapeutic agents. Approaches to metabolite purification, rapid dereplication, and biological evaluation including analytical hyphenated techniques, molecular networking, and advanced cellular and animal models are discussed. Further, enhanced and targeted drug delivery systems for phytochemicals, including micelles, nanoparticles and antibody drug conjugates (ADCs) are described herein.

2D- and 3D-cultures of human trabecular meshwork cells: A preliminary assessment of an in vitro model for glaucoma study

A physiologically relevant in vitro human-based model could be the ‘gold standard’ to clarify the pathological steps involved in glaucoma onset. In this regard, human 3D cultures may represent an excellent starting point to achieve this goal. Indeed, the 3D matrix allows to re-create the in vivo-like tissue architecture, maintaining its functionality and cellular behaviour, compared to the 2D model. Thus, we propose a comparison between the 2D and 3D in vitro models of human trabecular meshwork cells in terms of cellular responses after chronic stress exposure. Our results showed that 3D-cells are more sensitive to intracellular reactive oxidative specie production induced by hydrogen peroxide treatment, compared to 2D cultures. Additionally, in 3D cultures a more accurate regulation of the apoptosis trigger and cell adaptation mechanisms was detected than in 2D models. In line with these findings, the 3D-HTMC model shows the ability to better mimic the in vivo cell behaviour in adaptive responses to chronic oxidative stress than 2D.

PLLA scaffolds with controlled architecture as potential microenvironment for in vitro tumor model

The "microenvironment" where a tumor develops plays a fundamental role in determining its progression, the onset of metastasis and, eventually, its resistance to therapies. Tumor cells can be considered more or less invasive depending both on the nature of the cells and on the site where they are located. Commonly adopted laboratory culture protocols for the investigation of tumor cells take usually place on standard two-dimensional supports. However, such cultures do not allow for reproduction of the biophysical properties of the tumor's microenvironment, thus causing the cells to lose most of their relevant characteristics. In this work MDA-MB 231 breast cancer cells were cultivated within Poly-l-Lactic Acid (PLLA) scaffolds produced via Thermally Induced Phase Separation (TIPS). Starting from a ternary solution (polymer-solvent-nonsolvent) we produced scaffolds with different morphologies, porosities and pore architectures. The influence of porosity and average pore size upon cell adhesion and growth were investigated by using Cell Counting Kit-8 (CCK-8) as cell viability test, a fluorescence assay staining cell with DAPI and Scanning Electron Microscopy (SEM). Our study demonstrates that the average pore size of the polymeric scaffolds influences both the cell adhesion and resulting morphology of the growing breast cancer cells. In particular, the reported data corroborate the evidence that an average pore size ranging from 40 to 50 μm induces tumor cell aggregation and the formation of the irregular tumor masses typically observed in-vivo. In addition, TIPS proved to be a suitable manufacturing technique for finely tuning the scaffolds' architecture, relevant to developing the most effective microenvironment for an in-vitro tumor cells growth closely mimicking in-vivo conditions.