Aranzazu Villasante

Tissue-engineered models of human tumors for cancer research

Introduction: Drug toxicity often goes undetected until clinical trials, which are the most costly and dangerous phase of drug development. Both the cultures of human cells and animal studies have limitations that cannot be overcome by incremental improvements in drug-testing protocols. A new generation of bioengineered tumors is now emerging in response to these limitations, with potential to transform drug screening by providing predictive models of tumors within their tissue context, for studies of drug safety and efficacy. An area that could greatly benefit from these models is cancer research. Areas covered: In this review, the authors first describe the engineered tumor systems, using Ewing’s sarcoma as an example of human tumor that cannot be predictably studied in cell culture and animal models. Then, they discuss the importance of the tissue context for cancer progression and outline the biomimetic principles for engineering human tumors. Finally, they discuss the utility of bioengineered tumor models for cancer research and address the challenges in modeling human tumors for use in drug discovery and testing. Expert opinion: While tissue models are just emerging as a new tool for cancer drug discovery, they are already demonstrating potential for recapitulating, in vitro, the native behavior of human tumors. Still, numerous challenges need to be addressed before we can have platforms with a predictive power appropriate for the pharmaceutical industry. Some of the key needs include the incorporation of the vascular compartment, immune system components, and mechanical signals that regulate tumor development and function.

Bioengineered human tumor within a bone niche

Monolayer cultures of tumor cells and animal studies have tremendously advanced our understanding of cancer biology. However, we often lack animal models for human tumors, and cultured lines of human cells quickly lose their cancer signatures. In recent years, simple 3D models for cancer research have emerged, including cell culture in spheroids and on biomaterial scaffolds. Here we describe a bioengineered model of human Ewings sarcoma that mimics the native bone tumor niche with high biological fidelity. In this model, cancer cells that have lost their transcriptional profiles after monolayer culture re-express genes related to focal adhesion and cancer pathways. The bioengineered model recovers the original hypoxic and glycolytic tumor phenotype, and enables re-expression of angiogenic and vasculogenic mimicry features that favor tumor adaptation. We propose that differentially expressed genes between the monolayer cell culture and native tumor environment are potential therapeutic targets that can be explored using the bioengineered tumor model.

Biomimetic Tissue–Engineered Systems for Advancing Cancer Research: NCI Strategic Workshop Report

Advanced technologies and biomaterials developed for tissue engineering and regenerative medicine present tractable biomimetic systems with potential applications for cancer research. Recently, the National Cancer Institute convened a Strategic Workshop to explore the use of tissue biomanufacturing for development of dynamic, physiologically relevant in vitro and ex vivo biomimetic systems to study cancer biology and drug efficacy. The workshop provided a forum to identify current progress, research gaps, and necessary steps to advance the field. Opportunities discussed included development of tumor biomimetic systems with an emphasis on reproducibility and validation of new biomimetic tumor models, as described in this report.

Galvanic microparticles increase migration of human dermal fibroblasts in a wound-healing model via reactive oxygen species pathway

Electrical signals have been implied in many biological mechanisms, including wound healing, which has been associated with transient electrical currents not present in intact skin. One method to generate electrical signals similar to those naturally occurring in wounds is by supplementation of galvanic particles dispersed in a cream or gel. We constructed a three-layered model of skin consisting of human dermal fibroblasts in hydrogel (mimic of dermis), a hydrogel barrier layer (mimic of epidermis) and galvanic microparticles in hydrogel (mimic of a cream containing galvanic particles applied to skin). Using this model, we investigated the effects of the properties and amounts of Cu/Zn galvanic particles on adult human dermal fibroblasts in terms of the speed of wound closing and gene expression. The collected data suggest that the effects on wound closing are due to the ROS-mediated enhancement of fibroblast migration, which is in turn mediated by the BMP/SMAD signaling pathway. These results imply that topical low-grade electric currents via microparticles could enhance wound healing.

Biomechanical regulation of drug sensitivity in an engineered model of human tumor

Predictive testing of anticancer drugs remains a challenge. Bioengineered systems, designed to mimic key aspects of the human tumor microenvironment, are now improving our understanding of cancer biology and facilitating clinical translation. We show that mechanical signals have major effects on cancer drug sensitivity, using a bioengineered model of human bone sarcoma. Ewing sarcoma (ES) cells were studied within a three-dimensional (3D) matrix in a bioreactor providing mechanical loadings. Mimicking bone-like mechanical signals within the 3D model, we rescued the ERK1/2-RUNX2 signaling pathways leading to drug resistance. By culturing patient-derived tumor cells in the model, we confirmed the effects of mechanical signals on cancer cell survival and drug sensitivity. Analyzing human microarray datasets, we showed that RUNX2 expression is linked to poor survival in ES patients. Mechanical loadings that activated signal transduction pathways promoted drug resistance, stressing the importance of introducing mechanobiological cues into preclinical tumor models for drug screening.

Cardiac recovery via extended cell-free delivery of extracellular vesicles secreted by cardiomyocytes derived from induced pluripotent stem cells

The ability of extracellular vesicles (EVs) to regulate a broad range of cellular processes has recently been exploited for the treatment of diseases. For example, EVs secreted by therapeutic cells injected into infarcted hearts can induce recovery through the delivery of cell-specific microRNAs. However, retention of the EVs and the therapeutic effects are short-lived. Here, we show that an engineered hydrogel patch capable of slowly releasing EVs secreted from cardiomyocytes (CMs) derived from induced pluripotent stem cells reduced arrhythmic burden, promoted ejection-fraction recovery, decreased CM apoptosis 24 h after infarction, and reduced infarct size and cell hypertrophy 4 weeks post-infarction when implanted onto infarcted rat hearts. We also show that EVs are enriched with cardiac-specific microRNAs known to modulate CM-specific processes. The extended delivery of EVs secreted from induced-pluripotent-stem-cell-derived CMs into the heart may help us to treat heart injury and to understand heart recovery.A hydrogel patch for the sustained delivery of extracellular vesicles from cardiomyocytes derived from induced pluripotent stem cells improves tissue regeneration in infarcted rat hearts.

Bioengineered Models of Solid Human Tumors for Cancer Research

The lack of controllable in vitro models that can recapitulate the features of solid tumors such as Ewings sarcoma limits our understanding of the tumor initiation and progression and impedes the development of new therapies. Cancer research still relies of the use of simple cell culture, tumor spheroids, and small animals. Tissue-engineered tumor models are now being grown in vitro to mimic the actual tumors in patients. Recently, we have established a new protocol for bioengineering the Ewings sarcoma, by infusing tumor cell aggregates into the human bone engineered from the patients mesenchymal stem cells. The bone niche allows crosstalk between the tumor cells, osteoblasts and supporting cells of the bone, extracellular matrix, and the tissue microenvironment. The bioreactor platform used in these experiments also allows the implementation of physiologically relevant mechanical signals. Here, we describe a method to build an in vitro model of Ewings sarcoma that mimics the key properties of the native tumor and provides the tissue context and physical regulatory signals.

Mimicking biophysical stimuli within bone tumor microenvironment.

In vivo, cells reside in a complex environment regulating their fate and function. Most of this complexity is lacking in standard in vitro models, leading to readouts falling short of predicting the actual in vivo situation. The use of engineering tools, combined with deep biological knowledge, leads to the development and use of bioreactors providing biologically sound niches. Such bioreactors offer new tools for biological research, and are now also entering the field of cancer research. Here we present the development and validation of a modular bioreactor system providing: (i) high throughput analyses, (ii) a range of biological conditions, (iii) high degree of control, and (iv) application of physiological stimuli to the cultured samples. The bioreactor was used to engineer a three-dimensional (3D) tissue model of cancer, where the effects of mechanical stimulation on the tumor phenotype were evaluated. Mechanical stimuli applied to the engineered tumor model activated the mechanotransduction machinery and resulted in measurable changes of mRNA levels towards a more aggressive tumor phenotype.