Engineering of biomaterials for tumor modeling

Three-dimensional in vitro model of bone metastases of neuroblastoma as a tool for pharmacological evaluations

In vitro metastatic models are foreseen to introduce a breakthrough in the field of preclinical screening of more functional small-molecule pharmaceuticals and biologics. To achieve this goal, the complexity of current in vitro systems requests an appropriate upgrade to approach the three-dimensional (3D) in vivo metastatic disease. Here, we explored the potential of our 3D β-tricalcium phosphate (β-TCP) model of neuroblastoma bone metastasis for drug toxicity assessment. Tailor-made scaffolds with interconnected channels were produced by combining 3D printing and slip casting method. The organization of neuroblastoma cells into a mesenchymal stromal cell (MSC) network, cultured under bioactive conditions provided by β-TCP, was monitored by two-photon microscopy. Deposition of extracellular matrix protein Collagen I by MSCs and persistent growth of tumor cells confirmed the cell-supportive performance of our 3D model. When different neuroblastoma cells were treated with conventional chemotherapeutics, the β-TCP model provided the necessary reproducibility and accuracy of experimental readouts. Drug efficacy evaluation was done for 3D and 2D cell cultures, highlighting the need for a higher dose of chemotherapeutics under 3D conditions to achieve the expected cytotoxicity in tumor cells. Our results confirm the importance of 3D geometry in driving native connectivity between nonmalignant and tumor cells and sustain β-TCP scaffolds as a reliable and affordable drug screening platform for use in the early stages of drug discovery.

Microphysiological systems as reliable drug discovery and evaluation tools: Evolution from innovation to maturity

Microphysiological systems (MPSs), also known as organ-on-chip or disease-on-chip, have recently emerged to reconstitute the in vivo cellular microenvironment of various organs and diseases on in vitro platforms. These microfluidics-based platforms are developed to provide reliable drug discovery and regulatory evaluation testbeds. Despite recent emergences and advances of various MPS platforms, their adoption of drug discovery and evaluation processes still lags. This delay is mainly due to a lack of rigorous standards with reproducibility and reliability, and practical difficulties to be adopted in pharmaceutical research and industry settings. This review discusses the current and potential use of MPS platforms in drug discovery processes while considering the context of several key steps during drug discovery processes, including target identification and validation, preclinical evaluation, and clinical trials. Opportunities and challenges are also discussed for the broader dissemination and adoption of MPSs in various drug discovery and regulatory evaluation steps. Addressing these challenges will transform long and expensive drug discovery and evaluation processes into more efficient discovery, screening, and approval of innovative drugs.

Exploring the promising potential of induced pluripotent stem cells in cancer research and therapy

The advent of iPSCs has brought about a significant transformation in stem cell research, opening up promising avenues for advancing cancer treatment. The formation of cancer is a multifaceted process influenced by genetic, epigenetic, and environmental factors. iPSCs offer a distinctive platform for investigating the origin of cancer, paving the way for novel approaches to cancer treatment, drug testing, and tailored medical interventions. This review article will provide an overview of the science behind iPSCs, the current limitations and challenges in iPSC-based cancer therapy, the ethical and social implications, and the comparative analysis with other stem cell types for cancer treatment. The article will also discuss the applications of iPSCs in tumorigenesis, the future of iPSCs in tumorigenesis research, and highlight successful case studies utilizing iPSCs in tumorigenesis research. The conclusion will summarize the advancements made in iPSC-based tumorigenesis research and the importance of continued investment in iPSC research to unlock the full potential of these cells.

Hypoxia-inducing cryogels uncover key cancer-immune cell interactions in an oxygen-deficient tumor microenvironment

Hypoxia is a major factor shaping the immune landscape, and several cancer models have been developed to emulate hypoxic tumors. However, to date, they still have several limitations, such as the lack of reproducibility, inadequate biophysical cues, limited immune cell infiltration, and poor oxygen (O2) control, leading to non-pathophysiological tumor responses. Therefore, it is essential to develop better cancer models that mimic key features of the tumor extracellular matrix and recreate tumor-associated hypoxia while allowing cell infiltration and cancer-immune cell interactions. Herein, hypoxia-inducing cryogels (HICs) have been engineered using hyaluronic acid (HA) to fabricate three-dimensional microtissues and model a hypoxic tumor microenvironment. Specifically, tumor cell-laden HICs have been designed to deplete O2 locally and induce long-standing hypoxia. HICs promoted changes in hypoxia-responsive gene expression and phenotype, a metabolic adaptation to anaerobic glycolysis, and chemotherapy resistance. Additionally, HIC-supported tumor models induced dendritic cell (DC) inhibition, revealing a phenotypic change in the plasmacytoid DC (pDC) subset and an impaired conventional DC (cDC) response in hypoxia. Lastly, our HIC-based melanoma model induced CD8+ T cell inhibition, a condition associated with the downregulation of pro-inflammatory cytokine secretion, increased expression of immunomodulatory factors, and decreased degranulation and cytotoxic capacity of T cells. Overall, these data suggest that HICs can be used as a tool to model solid-like tumor microenvironments and has great potential to deepen our understanding of cancer-immune cell relationship in low O2 conditions and may pave the way for developing more effective therapies.

Hypoxia-inducing cryogels uncover key cancer-immune cell interactions in an oxygen-deficient tumor microenvironment

Hypoxia, an important feature of solid tumors, is a major factor shaping the immune landscape, and several cancer models have been developed to emulate hypoxic tumors. However, to date, they still have several limitations, such as the lack of reproducibility, inadequate biophysical cues, limited immune cell infiltration, and poor oxygen (O 2 ) control, leading to non-pathophysiological tumor responses. As a result, it is essential to develop new and improved cancer models that mimic key features of the tumor extracellular matrix and recreate tumor-associated hypoxia while allowing cell infiltration and cancer-immune cell interactions. Herein, hypoxia-inducing cryogels (HICs) have been engineered using hyaluronic acid (HA) as macroporous scaffolds to fabricate three-dimensional microtissues and model a hypoxic tumor microenvironment. Specifically, tumor cell-laden HICs have been designed to deplete O 2 locally and induce long-standing hypoxia. This state of low oxygen tension, leading to HIF-1α stabilization in tumor cells, resulted in changes in hypoxia-responsive gene expression and phenotype, a metabolic adaptation to anaerobic glycolysis, and chemotherapy resistance. Additionally, HIC-supported tumor models induced dendritic cell (DC) inhibition, revealing a phenotypic change in plasmacytoid B220 + DC (pDC) subset and an impaired conventional B220 - DC (cDC) response in hypoxia. Lastly, our HIC-based melanoma model induced CD8+ T cell inhibition, a condition associated with the downregulation of pro-inflammatory cytokine secretion, increased expression of immunomodulatory factors, and decreased degranulation and cytotoxic capacity of T cells. Overall, these data suggest that HICs can be used as a tool to model solid-like tumor microenvironments and identify a phenotypic transition from cDC to pDC in hypoxia and the key contribution of HA in retaining cDC phenotype and inducing their hypoxia-mediated immunosuppression. This technology has great potential to deepen our understanding of the complex relationships between cancer and immune cells in low O 2 conditions and may pave the way for developing more effective therapies.

Combinational Treatment Involving Decellularized Extracellular Matrix Hydrogels With Mesenchymal Stem Cells Increased the Efficacy of Cell Therapy in Pancreatitis

Cell transplantation using mesenchymal stem cells (MSCs) has emerged as a promising approach to repairing and regenerating injured or impaired organs. However, the survival and retention of MSCs following transplantation remain a challenge. Therefore, we investigated the efficacy of co-transplantation of MSCs and decellularized extracellular matrix (dECM) hydrogels, which have high cytocompatibility and biocompatibility. The dECM solution was prepared by enzymatic digestion of an acellular porcine liver scaffold. It could be gelled and formed into porous fibrillar microstructures at physiological temperatures. MSCs expanded three-dimensionally in the hydrogel without cell death. Compared to the 2-dimensional cell culture, MSCs cultured in the hydrogel showed increased secretion of hepatocyte growth factor (HGF) and tumor necrosis factor-inducible gene 6 protein (TSG-6), both of which are major anti-inflammatory and anti-fibrotic paracrine factors of MSCs, under TNFα stimulation. In vivo experiments showed that the co-transplantation of MSCs with dECM hydrogel improved the survival rate of engrafted cells compared to those administered without the hydrogel. MSCs also demonstrated therapeutic effects in improving inflammation and fibrosis of pancreatic tissue in a dibutyltin dichloride (DBTC)-induced rat pancreatitis model. Combinational use of dECM hydrogel with MSCs is a new strategy to overcome the challenges of cell therapy using MSCs and can be used for treating chronic inflammatory diseases in clinical settings.

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.

Folic Acid-Functionalized Carbon Dot-Enabled Starvation Therapy in Synergism with Paclitaxel against Breast Cancer

Glucose oxidase (GOx)-induced cancer starvation has recently emerged for halting the abnormal proliferation of triple-negative breast cancer (TNBC). However, monotherapy with GOx or a conventional chemotherapeutic displays suboptimal efficacy in eliminating tumors and poses impending risks to healthy tissues. To augment therapeutic efficacy and tumor selectivity, folic acid (FA)-functionalized carbon dots (CDs) embedded with GOx and paclitaxel (PTX) [FA-CD-(PTX-GOx)] was developed that showed the efficient killing of TNBC, MDA-MB-468 cells over noncancerous HEK 293 cells through synergistic effects of cancer starvation-induced oxidative stress and chemotherapy. The cargo-laden FA-CD complex resulted in a 4-8 fold increase in cancer cell death at 60 μg/mL when compared to standalone therapy with the native compounds and individually loaded cargo on FA-CD. This improved cancer cell killing efficacy of the FA-CD-(PTX-GOx) complex could be endorsed by folate receptor (FR)-mediated target-specific cellular internalization of the FA-CD complex. The antitumorigenic efficacy of the FA-CD-(PTX-GOx) complex was further validated in a three-dimensional (3D) breast tumor spheroid model. A significant 4.5-fold reduction in spheroid dimension along with antiproliferation was observed with time up to 72 h following exposure to the FA-CD-(PTX-GOx) complex. This antitumorigenic potential of FA-CD-(PTX-GOx) could be attributed to the enhanced intratumoral reactive oxygen species generation following glucose depletion by GOx that has been facilitated by the chemotherapeutic efficacy of PTX resulting in the efficient killing of cancer cells. The present study provides a novel strategy of FR-mediated fluorescent CD-enabled combined formulation of GOx and PTX for the target-specific superior killing of TNBC cells in the synergism of glucose starvation with chemotherapy.