Spatially patterned 3D model mimics key features of cancer metastasis to bone

Bone is the most common target of metastasis in breast cancer and prostate cancer, leading to significant mortality due to lack of effective treatments. The discovery of novel therapies has been hampered by a lack of physiologically relevant in vitro models that can mimic key clinical features of bone metastases. To fill this critical gap, here we report spatially patterned, tissue engineered 3D models of breast cancer and prostate cancer bone metastasis which mimic bone-specific invasion, cancer aggressiveness, cancer-induced dysregulation of bone remodeling, and in vivo drug response. We demonstrate the potential of integrating such 3D models with single-cell RNA sequencing to identify key signaling drivers of cancer metastasis to bone. Together, these results validate that spatially patterned 3D bone metastasis models mimic key clinical features of bone metastasis and can serve as a novel research tool to elucidate bone metastasis biology and expedite drug discovery.

A 3D Osteosarcoma Model with Bone-Mimicking Cues Reveals a Critical Role of Bone Mineral and Informs Drug Discovery

Osteosarcoma (OS) is an aggressive bone cancer for which survival has not improved over three decades. While biomaterials have been widely used to engineer 3D soft-tissue tumor models, the potential of engineering 3D biomaterials-based OS models for comprehensive interrogation of OS pathology and drug discovery remains untapped. Bone is characterized by high mineral content, yet the role of bone mineral in OS progression and drug response remains unknown. Here, a microribbon-based OS model with bone-mimicking compositions is developed to elucidate the role of 3D culture and hydroxyapatite in OS signaling and drug response. The results reveal that hydroxyapatite in 3D is critical to support retention of OS signaling and drug resistance similar to patient tissues and mouse orthotopic tumors. The physiological relevance of this 3D model is validated using four established OS cell lines, seven patient-derived xenograft (PDX) cell lines and two animal models. Integrating 3D OS PDX models with RNA-sequencing identified 3D-specific druggable target, which predicts drug response in mouse orthotopic model. These results establish microribbon-based 3D OS models as a novel experimental tool to enable discovery of novel therapeutics that would be otherwise missed with 2D model and may serve as platforms to study patient-specific OS heterogeneity and drug resistance mechanisms.

Abstract 696: Spatially patterned, 3D in vitro models of cancer metastasis to bone for elucidating key drivers of metastasis and drug discovery

Bone is one of the most common sites of cancer metastasis, affecting more than 70% of patients with advanced breast cancer and prostate cancer. Despite its prevalence, there are still no effective treatments for bone metastasis, leading to very poor survival rates and the mechanism by which certain cancer cells preferentially spread to the bones remains poorly understood. Thus, there is a critical need to develop in vitro experimental models that can mimic key aspects of bone metastasis development to elucidate driving mechanisms of this disease and expedite the discovery of novel drug candidates. To address this unmet need, here we report a spatially patterned, 3D in vitro model which mimics cancer metastasis to bone by incorporating interactions with multiple tissue types. The model is composed of an outer ring of tissue engineered bone derived from 3D osteogenic differentiation of human mesenchymal stem cells (hMSCs), and a center containing cancer cells. This interface between these two tissues mimics the way cancer cells invade into the bones through the bone marrow/bone interface and allows us to track the invasion of fluorescently labeled cancer cells into bone using confocal imaging. Cancer cells and hMSCs were also labeled with orthogonal luciferases (FireflyLuc and NanoLuc), allowing for simultaneous quantification of cancer cell proliferation and osteoblast survival using BLI. We tested the ability of this model to recapitulate known characteristics of in vivo bone metastases including tissue-specific invasion, cancer aggressiveness, cancer-induced bone resorption, and in vivo drug response. Using multiple established breast cancer (MDA-MB-231 and MCF-7) and prostate cancer (LNCaP and PC-3) cell lines, we demonstrate that such spatially patterned coculture models mimic the preferential invasion of cancer cells to bone, but not cartilage or muscle (negative controls) and the rate of invasion in this 3D model correlated with the level of cancer cell aggressiveness. To mimic the effect of cancer invasion on bone remodeling, we established a triculture model in which osteoclasts were seeded over the tissue engineered bone. Micro-computed tomography imaging validated that this model could recapitulate cancer-induced bone resorption, and the degree of bone resorption also correlated with cancer cell aggressiveness. Using parathyroid hormone as a model drug, we demonstrate this 3D model recapitulates drug responses consistent with what has been observed using in vivo mouse models. Such spatially patterned 3D models can provide a scalable platform for drug screening with substantially reduced time and cost compared to animal models. Furthermore, integrating these 3D cancer metastasis models with high-dimensional methods, such as single-cell RNAseq could expedite the discovery of novel druggable drivers of bone metastasis.

Citation Format: Eva C. González Díaz, Michelle Tai, Callan E. Monette, Joy Wu, Fan Yang. Spatially patterned, 3D in vitro models of cancer metastasis to bone for elucidating key drivers of metastasis and drug discovery [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 696.

Tissue-engineered 3D models for elucidating primary and metastatic bone cancer progression

Malignant bone tumors are aggressive neoplasms which arise from bone tissue or as a result of metastasis. The most prevalent types of cancer, such as breast, prostate, and lung cancer, all preferentially metastasize to bone, yet the role of the bone niche in promoting cancer progression remains poorly understood. Tissue engineering has the potential to bridge this knowledge gap by providing 3D in vitro systems that can be specifically designed to mimic key properties of the bone niche in a more physiologically relevant context than standard 2D culture. Elucidating the crucial components of the bone niche that recruit metastatic cells, support tumor growth, and promote cancer-induced destruction of bone tissue would support efforts for preventing and treating these devastating malignancies. In this review, we summarize recent efforts focused on developing in vitro 3D models of primary bone cancer and bone metastasis using tissue engineering approaches. Such 3D in vitro models can enable the identification of effective therapeutic targets and facilitate high-throughput drug screening to effectively treat bone cancers. STATEMENT OF SIGNIFICANCE: Biomaterials-based 3D culture have been traditionally used for tissue regeneration. Recent research harnessed biomaterials to create 3D in vitro cancer models, with demonstrated advantages over conventional 2D culture in recapitulating tumor progression and drug response in vivo. However, previous work has been largely limited to modeling soft tissue cancer, such as breast cancer and brain cancer. Unlike soft tissues, bone is characterized with high stiffness and mineral content. Primary bone cancer affects mostly children with poor treatment outcomes, and bone is the most common site of cancer metastasis. Here we summarize emerging efforts on engineering 3D bone cancer models using tissue engineering approaches, and future directions needed to further advance this relatively new research area.

Mineralized Biomaterials Mediated Repair of Bone Defects Through Endogenous Cells

Synthetic biomaterials that create a dynamic calcium (Ca²⁺)-, phosphate (PO₄^3-) ion-, and calcium phosphate (CaP)-rich microenvironment, similar to that found in native bone tissue, have been shown to promote osteogenic commitment of stem cells in vitro and in vivo. The intrinsic osteoconductivity and osteoinductivity of such biomaterials make them promising bone grafts for the treatment of bone defects. We thus aimed to evaluate the potential of mineralized biomaterials to induce bone repair of a critical-sized cranial defect in the absence of exogenous cells and growth factors. Our results demonstrate that the mineralized biomaterial alone can support complete bone formation within critical-sized bone defects through recruitment of endogenous cells and neo-bone tissue formation in mice. The newly formed bone tissue recapitulated many key characteristics of native bone such as formation of bone minerals reaching similar bone mineral density, presence of bone-forming osteoblasts and tartrate-resistant acid phosphatase-expressing osteoclasts, as well as vascular networks. Biomaterials that recruit endogenous cells and provide a tissue-specific microenvironment to modulate cellular behavior and support generation of functional tissues are a key step forward in moving bench-side tissue engineering approaches to the bedside. Such tissue engineering strategies could eventually pave the path toward readily available therapies that significantly reduce patient cost of care and improve overall clinical outcomes.