Prostate Cancer Phenotype Influences Bone Mineralization at Metastasis: A Study Using an In Vitro Prostate Cancer Metastasis Testbed

Current Advances in the Use of Tissue Engineering for Cancer Metastasis Therapeutics

Cancer is a leading cause of death worldwide and results in nearly 10 million deaths each year. The global economic burden of cancer from 2020 to 2050 is estimated to be USD 25.2 trillion. The spread of cancer to distant organs through metastasis is the leading cause of death due to cancer. However, as of today, there is no cure for metastasis. Tissue engineering is a promising field for regenerative medicine that is likely to be able to provide rehabilitation procedures to patients who have undergone surgeries, such as mastectomy and other reconstructive procedures. Another important use of tissue engineering has emerged recently that involves the development of realistic and robust in vitro models of cancer metastasis, to aid in drug discovery and new metastasis therapeutics, as well as evaluate cancer biology at metastasis. This review covers the current studies in developing tissue-engineered metastasis structures. This article reports recent developments in in vitro models for breast, prostate, colon, and pancreatic cancer. The review also identifies challenges and opportunities in the use of tissue engineering toward new, clinically relevant therapies that aim to reduce the cancer burden.

Induction of Reactive Bone Stromal Fibroblasts in 3D Models of Prostate Cancer Bone Metastases

A dynamic interplay between prostate cancer (PCa) cells and reactive bone stroma modulates the growth of metastases within the bone microenvironment. Of the stromal cells, metastasis-associated fibroblasts (MAFs) are known to contribute but are the least studied cell type in PCa tumour progression. It is the aim of the current study to establish a biologically relevant 3D in vitro model that mimics the cellular and molecular profiles of MAFs found in vivo. Using 3D in vitro cell culture models, the bone-derived fibroblast cell line, HS-5, was treated with conditioned media from metastatic-derived PCa cell lines, PC3 and MDA-PCa 2b, or mouse-derived fibroblasts 3T3. Two corresponding reactive cell lines were propagated: HS5-PC3 and HS5-MDA, and evaluated for alterations in morphology, phenotype, cellular behaviour, plus protein and genomic profiles. HS5-PC3 and HS5-MDA displayed distinct alterations in expression levels of N-Cadherin, non-functional E-Cadherin, alpha-smooth muscle actin (α-SMA), Tenascin C, and vimentin, along with transforming growth factor receptor expression (TGF β R1 and R2), consistent with subpopulations of MAFs reported in vivo. Transcriptomic analysis revealed a reversion of HS5-PC3 towards a metastatic phenotype with an upregulation in pathways known to regulate cancer invasion, proliferation, and angiogenesis. The exploitation of these engineered 3D models could help further unravel the novel biology regulating metastatic growth and the role fibroblasts play in the colonisation process.

Interstitial fluid flow contributes to prostate cancer invasion and migration to bone; study conducted using a novel horizontal flow bioreactor

Prostate cancer bone metastasis is the leading cause of cancer-related mortality in men in the United States, causing severe damage to skeletal tissue. The treatment of advanced-stage prostate cancer is always challenging due to limited drug treatment options, resulting in low survival rates. There is a scarcity of knowledge regarding the mechanisms associated with the effects of biomechanical cues by the interstitial fluid flow on prostate cancer cell growth and migration. We have designed a novel bioreactor system to demonstrate the impact of interstitial fluid flow on the migration of prostate cancer cells to the bone during extravasation. First, we demonstrated that a high flow rate induces apoptosis in PC3 cells via TGF-β1 mediated signaling; thus, physiological flow rate conditions are optimum for cell growth. Next, to understand the role of interstitial fluid flow in prostate cancer migration, we evaluated the migration rate of cells under static and dynamic conditions in the presence or absence of bone. We report that CXCR4 levels were not significantly changed under static and dynamic conditions, indicating that CXCR4 activation in PC3 cells is not influenced by flow conditions but by the bone, where CXCR4 levels were upregulated. The bone-upregulated CXCR4 levels led to increased MMP-9 levels resulting in a high migration rate in the presence of bone. In addition, upregulated levels ofα_vβ₃integrins under fluid flow conditions contributed to an overall increase in the migration rate of PC3 cells. Overall, this study demonstrates the potential role of interstitial fluid flow in prostate cancer invasion. Understanding the critical role of interstitial fluid flow in promoting prostate cancer cell progression will enhance current therapies for advanced-stage prostate cancer and provide improved treatment options for patients.

Conditioned medium of PC‑3 prostate cancer cells affects microRNA and mRNA profiles in mechanically strained osteoblasts

Bone is the main site of metastasis from prostate cancer; therefore, it is important to investigate the microRNAs (miRNAs) and mRNA associated with bone metastases from prostate cancer. Since an appropriate mechanical environment is important in the growth of bone, in the present study, the miRNA, mRNA, and long non-coding RNA (lncRNA) profiles of mechanically strained osteoblasts treated with conditioned medium (CM) from PC-3 prostate cancer cells were studied. MC3T3-E1 osteoblastic cells were treated with the CM of PC-3 prostate cancer cells and were simultaneously stimulated with a mechanical tensile strain of 2,500 µε at 0.5 Hz; the osteoblastic differentiation of the MC3T3-E1 cells was then assessed. In addition, the differential expression levels of mRNA, miRNA and lncRNA in MC3T3-E1 cells treated with the CM of PC-3 cells were screened, and some of the miRNAs and mRNAs were verified by reverse transcription-quantitative PCR (RT-qPCR). The signal molecules and signaling pathways associated with osteogenic differentiation were predicted by bioinformatics analysis. The CM of PC-3 prostate cancer cells suppressed osteoblastic differentiation of MC3T3-E1 cells. A total of seven upregulated miRNAs and 12 downregulated miRNAs were selected by sequencing and further verified using RT-qPCR, and related differentially expressed genes (11 upregulated and 12 downregulated genes) were also selected by sequencing and further verified using RT-qPCR; subsequently, according to the enrichment of differentially expressed genes in signaling pathways, nine signaling pathways involved in osteogenic differentiation were screened out. Furthermore, a functional mRNA-miRNA-lncRNA regulatory network was constructed. The differentially expressed miRNAs, mRNAs and lncRNAs may provide a novel signature in bone metastases of prostate cancer. Notably, some of the signaling pathways and related genes may be associated with pathological osteogenic differentiation caused by bone metastasis of prostate cancer.

Nanoclays in medicine: a new frontier of an ancient medical practice

Clays have been used as early as 2500 BC in human civilization for medicinal purposes. The ease of availability, biocompatibility, and versatility of these unique charged 2D structures abundantly available in nature have enabled the extensive applications of clays in human history. Recent advances in the use of clays in nanostructures and as components of polymer clay nanocomposites have exponentially expanded the use of clays in medicine. This review covers the details of structures and biomedical applications of several common clays, including montmorillonite, LAPONITE®, kaolinite, and halloysite. Here we describe the applications of these clays in wound dressings as hemostatic agents in drug delivery of drugs for cancer and other diseases and tissue engineering. Also reviewed are recent experimental and modeling studies that elucidate the impact of clay structures on cellular processes and cell adhesion processes. Various mechanisms of clay-mediated bioactivity, including protein localization, modulation of cell adhesion, biomineralization, and the potential of clay nanoparticles to impact cell differentiation, are presented. We also review the current developments in understanding the impact of clays on cellular responses. This review also elucidates new emerging areas of use of nanoclays in osteogenesis and the development of in vitro models of bone metastasis of cancer.

Label-free discrimination of tumorigenesis stages using in vitro prostate cancer bone metastasis model by Raman imaging

Metastatic prostate cancer colonizes the bone to pave the way for bone metastasis, leading to skeletal complications associated with poor prognosis and morbidity. This study demonstrates the feasibility of Raman imaging to differentiate between cancer cells at different stages of tumorigenesis using a nanoclay-based three-dimensional (3D) bone mimetic in vitro model that mimics prostate cancer bone metastasis. A comprehensive study comparing the classification of as received prostate cancer cells in a two-dimensional (2D) model and cancer cells in a 3D bone mimetic environment was performed over various time intervals using principal component analysis (PCA). Our results showed distinctive spectral differences in Raman imaging between prostate cancer cells and the cells cultured in 3D bone mimetic scaffolds, particularly at 1002, 1261, 1444, and 1654 cm-1, which primarily contain proteins and lipids signals. Raman maps capture sub-cellular responses with the progression of tumor cells into metastasis. Raman feature extraction via cluster analysis allows for the identification of specific cellular constituents in the images. For the first time, this work demonstrates a promising potential of Raman imaging, PCA, and cluster analysis to discriminate between cancer cells at different stages of metastatic tumorigenesis.

LncRNA nuclear-enriched abundant transcript 1 shuttled by prostate cancer cells-secreted exosomes initiates osteoblastic phenotypes in the bone metastatic microenvironment via miR-205-5p/runt-related transcription factor 2/splicing factor proline- and glutamine-rich/polypyrimidine tract-binding protein 2 axis

Prostate cancer (PCa) patients commonly present with osteoblastic-type bone metastasis. Exosomes derived from tumor cells possess biological significance and can mediate intercellular communication in the tumor microenvironment. Long noncoding RNA (lncRNA) nuclear-enriched abundant transcript 1 (NEAT1) is also implicated in the stability in tumorigenesis and the development of PCa, but the underlying mechanism remains elusive. Hence, the current study set out to investigate the physiological mechanisms by which exosomes-encapsulated NEAT1 affects the progression of PCa. First, after isolation, we found PCa cell-derived exosomes induced the osteogenic differentiation of human bone marrow-derived mesenchymal stem cells (hBMSCs). Besides, NEAT1 in PCa cells could be transferred into hBMSCs via exosomes. Further gain- and loss-of-function experimentation revealed that NEAT1 acted as a competing endogenous RNA (ceRNA) of microRNA (miR)-205-5p to upregulate the runt-related transcription factor 2 (RUNX2) levels. Moreover, NEAT1 could promote the RUNX2 expression via the splicing factor proline- and glutamine-rich (SFPQ)/polypyrimidine tract-binding protein 2 (PTBP2) axis. Functional assays uncovered that NEAT1 shuttled by PCa-exosomes facilitated the activity of alkaline phosphatase (ALP) and mineralization of extracellular matrix, and continuously upregulated the levels of RUNX2, ALP, alpha-1 type 1 collagen, and osteocalcin by regulating RUNX2, to induce the osteogenic differentiation of hBMSCs. Furthermore, in vivo experimentation confirmed that upregulated NEAT1 induced osteogenesis. Collectively, our findings indicated that PCa-derived exosomes-loaded NEAT1 upregulated RUNX2 to facilitate the osteogenesis of hBMSCs by competitively binding to miR-205-5p via the SFPQ/PTBP2 axis, therefore providing a potential therapeutic target to treat osteogenesis of hBMSCs in PCa. PCa cells secrete exosomes containing NEAT1, and NEAT1 exerts effects on osteogenic differentiation of hBMSCs in PCa. NEAT1 shuttled by PCa-derived exosomes could be transferred into hBMSCs, where NEAT1 exerted inductive properties in osteogenic differentiation of hBMSCs through the upregulation of RUNX2 by competitively binding to miR-205-5p and regulating SFPQ/PTBP2 in vitro and in vivo.

Nanostructured Biomaterials for In Vitro Models of Bone Metastasis Cancer

In recent years, tissue engineering approaches have attracted substantial attention owing to their ability to create physiologically relevant in vitro disease models that closely mimic in vivo conditions. Here, we review nanocomposite materials and scaffolds used for the design of in vitro models of cancer, including metastatic sites. We discuss the role of material properties in modulating cellular phenotype in 3D disease models. Also, we highlight the application of tissue-engineered bone as a tool for faithful recapitulation of the microenvironment of metastatic prostate and breast cancer, since these two types of cancer have the propensity to metastasize to bone. Overall, we summarize recent efforts on developing 3D in vitro models of bone metastatic cancers that provide a platform to study tumor progression and facilitate high-throughput drug screening.

Mechanobiological evaluation of prostate cancer metastasis to bone using an in vitro prostate cancer testbed

Prostate cancer exhibits a propensity to metastasize to the bone, which often leads to fatality. Bone metastasis is characterized by complex biochemical, morphological, pathophysiological, and genetic changes to cancer cells as they colonize at bone sites. In this study, we report the evaluation of MDA PCa2b prostate cancer cells' nanomechanical properties during the mesenchymal-to-epithelial transition (MET) and during disease progression at the metastatic site. Bone-mimetic tissue-engineered 3D nanoclay scaffolds have been used to create in vitro metastatic site for prostate cancer. A significant softening of the prostate cancer cells during MET and further softening as disease progression occurs at metastasis is also reported. The significant reduction in elastic modulus of prostate cancer cells during MET was attributed to actin reorganization and depolymerization. This study provides input towards direct nanomechanical measurements to evaluate the time evolution of cells' mechanical behavior in tumors at bone metastasis site.

Biomechanical Properties of Metastatically Involved Osteolytic Bone

PURPOSE OF REVIEW

Skeletal metastasis involves the uncoupling of physiologic bone remodeling resulting in abnormal bone turnover and radical changes in bony architecture, density, and quality. Bone strength assessment and fracture risk prediction are critical in clinical treatment decision-making. This review focuses on bone tissue and structural mechanisms altered by osteolytic metastasis and the resulting changes to its material and mechanical behavior.

RECENT FINDINGS

Both organic and mineral phases of bone tissue are altered by osteolytic metastatic disease, with diminished bone quality evident at multiple length-scales. The mechanical performance of bone with osteolytic lesions is influenced by a combination of tissue-level and structural changes. This review considers the effects of osteolytic metastasis on bone biomechanics demonstrating its negative impact at tissue and structural levels. Future studies need to assess the cumulative impact of cancer treatments on metastatically involved bone quality, and its utility in directing multimodal treatment planning.

The biology and engineered modeling strategies of cancer-nerve crosstalk

A recent finding critical to cancer aggravation is the interaction between cancer cells and nerves. There exist two main modes of cancer-nerve interaction: perineural invasion (PNI) and tumor innervation. PNI occurs when cancer cells infiltrate the adjacent nerves, and its relative opposite, tumor innervation, occurs when axons extend into tumor bodies. Like most cancer studies, these crosstalk interactions have mostly been observed in patient samples and animal models at this point, making it difficult to understand the mechanisms in a controlled manner. As such, in recent years in vitro studies have emerged that have helped identify various microenvironmental factors responsible for cancer-nerve crosstalk, including but not limited to neurotrophic factors, neurotransmitters, chemokines, cancer-derived exosomes, and Schwann cells. The versatility of in vitro systems warrants continuous development to increase physiological relevance to study PNI and tumor innervation, for example by utilizing biomimetic three-dimensional (3D) culture systems. Despite the wealth of 3D in vitro cancer models, comparatively there exists a lack of 3D in vitro models of nerve, PNI, and tumor innervation. Native-like 3D in vitro models of cancer-nerve interactions may further help develop therapeutic strategies to curb nerve-mediated cancer aggravation. As such, we provide an overview of the key players of cancer-nerve crosstalk and current in vitro models of the crosstalk, as well as cancer and nerve models. We also discuss a few future directions in cancer-nerve crosstalk research.

Role of αVβ3 in Prostate Cancer: Metastasis Initiator and Important Therapeutic Target

In prostate cancer, distant organ metastasis is the leading cause of patient death. Although the mechanism of malignant tumor metastasis is unclear, studies have confirmed that integrin αVβ3 plays an important role in this process. In prostate cancer, αVβ3 mediates adhesion, invasion, immune escape and neovascularization through interactions with different ligands. Among these ligands and in addition to proteins that are directly related to tumor invasion, other proteins that contain the RGD structure could also bind to αVβ3 and cause a number of biological effects. In this article, we summarized the ligand and downstream proteins related to αVβ3-mediated prostate cancer metastasis as well as some diagnostic and therapeutic measures targeting αVβ3.

Bone interface modulates drug resistance in breast cancer bone metastasis

Metastatic breast cancer cells on arriving at bone site interact with the bone cells to influence their growth, proliferation, and chemoresistance. There are currently no effective therapeutics available in the clinic for bone metastases. Many existing anti-cancer therapeutics are ineffective at the metastatic bone site due to a lack of accurate models of breast cancer bone metastasis for drug screening. Here, we report the development of an effective in vitro model using osteogenically differentiated human mesenchymal stem cells (MSCs) and human breast cancer cells on 3D nanoclay scaffolds as a testbed for screening drugs. Our results demonstrate that breast cancer cells grown in 3D bone-mimetic scaffolds exhibited altered physiological and biochemical properties, including tumoroids formation, elevated levels of cytokine such as IL-6, and its downstream effector-mediated inhibition of apoptosis and upregulation of multidrug transporters proteins, leading to drug resistance against paclitaxel. Most importantly, Signal Transducer and Activator of Transcription 3 (STAT3), a potential biomarker for chemoresistance in many cancers, was activated in the 3D breast cancer bone metastasis model. Thus, our data suggest that 3D bone-mimetic nanoclay scaffolds-based in vitro tumor model is a promising testbed for screening new therapeutics for breast cancer bone metastasis where bone interface governs drug resistance in breast cancer cells.