Prostate cancer specific integrin alphavbeta3 modulates bone metastatic growth and tissue remodeling

Nanotherapeutics for prostate cancer treatment: A comprehensive review

Prostate cancer (PCa) is the most prevalent solid organ malignancy and seriously affects male health. The adverse effects of prostate cancer therapeutics can cause secondary damage to patients. Nanotherapeutics, which have special targeting abilities and controlled therapeutic release profiles, may serve as alternative agents for PCa treatment. At present, many nanotherapeutics have been developed to treat PCa and have shown better treatment effects in animals than traditional therapeutics. Although PCa nanotherapeutics are highly attractive, few successful cases have been reported in clinical practice. To help researchers design valuable nanotherapeutics for PCa treatment and avoid useless efforts, herein, we first reviewed the strategies and challenges involved in prostate cancer treatment. Subsequently, we presented a comprehensive review of nanotherapeutics for PCa treatment, including their targeting methods, controlled release strategies, therapeutic approaches and mechanisms. Finally, we proposed the future prospects of nanotherapeutics for PCa treatment.

Monoclonal antibody-navigated carbon-encapsulated iron nanoparticles used for MRI-based tracking integrin receptors in murine melanoma

Integrin beta-3 is a cell adhesion molecule that mediate cell-to-cell and cell-to-extracellular matrix communication. The major goal of this study was to explore melanoma cells (B16F10) based upon specific direct targeting of the β3 subunit (CD61) in the integrin αvβ3 receptor using carbon-encapsulated iron nanoparticles decorated with monoclonal antibodies (Fe@C-CONH-anti-CD61 and Fe@C-(CH2)2-CONH-anti-CD61). Both melanoma cells treated with nanoparticles as well as C57BL/6 mice bearing syngeneic B16-F10 tumors intravenously injected with nanoparticles were tested in preclinical MRI studies. The as-synthesized carbon-encapsulated iron nanoparticles functionalized with CD61 monoclonal antibodies have been successfully used as a novel targeted contrast agent for MRI-based tracking melanoma cells expressing the β3 subunit of the integrin αvβ3 receptor.

Interleukin-30 subverts prostate cancer-endothelium crosstalk by fostering angiogenesis and activating immunoregulatory and oncogenic signaling pathways

BACKGROUND

Cancer-endothelial interplay is crucial for tumor behavior, yet the molecular mechanisms involved are largely unknown. Interleukin(IL)-30, which is expressed as a membrane-anchored cytokine by human prostate cancer (PC) cells, promotes PC vascularization and progression, but the underlying mechanisms have yet to be fully explored.

METHODS

PC-endothelial cell (EC) interactions were investigated, after coculture, by flow cytometry, transcriptional profiling, western blot, and ELISA assays. Proteome profiler phospho-kinase array unveiled the molecular pathways involved. The role of tumor-derived IL30 on the endothelium's capacity to generate autocrine circuits and vascular budding was determined following IL30 overexpression, by gene transfection, or its deletion by CRISPR/Cas9 genome editing. Clinical value of the experimental findings was determined through immunopathological study of experimental and patient-derived PC samples, and bioinformatics of gene expression profiles from PC patients.

RESULTS

Contact with PC cells favors EC proliferation and production of angiogenic and angiocrine factors, which are boosted by PC expression of IL30, that feeds autocrine loops, mediated by IGF1, EDN1, ANG and CXCL10, and promotes vascular budding and inflammation, via phosphorylation of multiple signaling proteins, such as Src, Yes, STAT3, STAT6, RSK1/2, c-Jun, AKT and, primarily CREB, GSK-3α/β, HSP60 and p53. Deletion of the IL30 gene in PC cells inhibits endothelial expression of IGF1, EDN1, ANG and CXCL10 and substantially impairs tumor angiogenesis. In its interaction with IL30-overexpressing PC cells the endothelium boosts their expression of a wide range of immunity regulatory genes, including CCL28, CCL4, CCL5, CCR2, CCR7, CXCR4, IL10, IL13, IL17A, FASLG, IDO1, KITLG, TNFA, TNFSF10 and PDCD1, and cancer driver genes, including BCL2, CCND2, EGR3, IL6, VEGFA, KLK3, PTGS1, LGALS4, GNRH1 and SHBG. Immunopathological analyses of PC xenografts and in silico investigation of 1116 PC cases, from the Prostate Cancer Transcriptome Atlas, confirmed the correlation between the expression of IL30 and that of both pro-inflammatory genes, NOS2, TNFA, CXCR5 and IL12B, and cancer driver genes, LGALS4, GNRH1 and SHBG, which was validated in a cohort of 80 PC patients.

CONCLUSIONS

IL30 regulates the crosstalk between PC and EC and reshapes their transcriptional profiles, triggering angiogenic, immunoregulatory and oncogenic gene expression programs. These findings highlight the angiostatic and oncostatic efficacy of targeting IL30 to fight PC.

Circulating Tumor Cells Adhesion: Application in Biosensors

The early and non-invasive diagnosis of tumor diseases has been widely investigated by the scientific community focusing on the development of sensors/biomarkers that act as a way of recognizing the adhesion of circulating tumor cells (CTCs). As a challenge in this area, strategies for CTCs capture and enrichment currently require improvements in the sensors/biomarker's selectivity. This can be achieved by understanding the biological recognition factors for different cancer cell lines and also by understanding the interaction between surface parameters and the affinity between macromolecules and the cell surface. To overcome some of these concerns, electrochemical sensors have been used as precise, fast-response, and low-cost transduction platforms for application in cytosensors. Additionally, distinct materials, geometries, and technologies have been investigated to improve the sensitivity and specificity properties of the support electrode that will transform biochemical events into electrical signals. This review identifies novel approaches regarding the application of different specific biomarkers (CD44, Integrins, and EpCAm) for capturing CTCs. These biomarkers can be applied in electrochemical biosensors as a cytodetection strategy for diagnosis of cancerous diseases.

Inhibition of cancer-type amino acid transporter LAT1 suppresses B16-F10 melanoma metastasis in mouse models

Metastasis is the leading cause of mortality in cancer patients. L-type amino acid transporter 1 (LAT1, SLC7A5) is a Na+-independent neutral amino acid transporter highly expressed in various cancers to support their growth. Although high LAT1 expression is closely associated with cancer metastasis, its role in this process remains unclear. This study aimed to investigate the effect of LAT1 inhibition on cancer metastasis using B16-F10 melanoma mouse models. Our results demonstrated that nanvuranlat (JPH203), a high-affinity LAT1-selective inhibitor, suppressed B16-F10 cell proliferation, migration, and invasion. Similarly, LAT1 knockdown reduced cell proliferation, migration, and invasion. LAT1 inhibitors and LAT1 knockdown diminished B16-F10 lung metastasis in a lung metastasis model. Furthermore, nanvuranlat and LAT1 knockdown suppressed lung, spleen, and lymph node metastasis in an orthotopic metastasis model. We discovered that the LAT1 inhibitor reduced the cell surface expression of integrin αvβ3. Our findings revealed that the downregulation of the mTOR signaling pathway, induced by LAT1 inhibitors, decreased the expression of integrin αvβ3, contributing to the suppression of metastasis. These results highlight the critical role of LAT1 in cancer metastasis and suggest that LAT1 inhibition may serve as a potential target for anti-metastasis cancer therapy.

Animal models of bone metastatic prostate cancer

Metastatic disease is a main cause of mortality in prostate cancer and remains to be incurable despite emerging new treatment agents. Development of novel treatment agents are confined within the boundaries of our knowledge of bone metastatic prostate cancer. Exploration into the underlying mechanism of metastatic tumorigenesis and treatment resistance will further expose novel targets for novel treatment agents. Up to date, many of these researches have been conducted with animal models which have served as classical tools that play a pivotal role in understanding the fundamental nature of cancer. The ability to reproduce the natural course of prostate cancer would be of profound value. However, currently available models do not reproduce the entire process of tumorigenesis to bone metastasis and are limited to reproducing small portions of the entire process. Therefore, knowledge of available models and understanding the strengths and weaknesses for each model is key to achieve research objectives. In this article, we take an overview of cell line injection animal models and patient derived xenograft models that have been applied to the research of human prostate cancer bone metastasis.

The role of integrin family in bone metabolism and tumor bone metastasis

Integrins have been the research focus of cell-extracellular matrix adhesion (ECM) and cytokine receptor signal transduction. They are involved in the regulation of bone metabolism of bone precursor cells, mesenchymal stem cells (MSCs), osteoblasts (OBs), osteoclasts (OCs), and osteocytes. Recent studies expanded and updated the role of integrin in bone metabolism, and a large number of novel cytokines were found to activate bone metabolism pathways through interaction with integrin receptors. Integrins act as transducers that mediate the regulation of bone-related cells by mechanical stress, fluid shear stress (FSS), microgravity, hypergravity, extracellular pressure, and a variety of physical factors. Integrins mediate bone metastasis of breast, prostate, and lung cancer by promoting cancer cell adhesion, migration, and survival. Integrin-mediated targeted therapy showed promising prospects in bone metabolic diseases. This review emphasizes the latest research results of integrins in bone metabolism and bone metastasis and provides a vision for treatment strategies.

Role of myeloid-derived suppressor cells in tumor recurrence

The establishment of primary tumor cells in distant organs, termed metastasis, is the principal cause of cancer mortality and is a crucial therapeutic target in oncology. Thus, it is critical to establish a better understanding of metastatic progression for the future development of improved therapeutic approaches. Indeed, such development requires insight into the timing of tumor cell dissemination and seeding of distant organs resulting in occult lesions. Following dissemination of tumor cells from the primary tumor, they can reside in niches in distant organs for years or decades, following which they can emerge as an overt metastasis. This timeline of metastatic dormancy is regulated by interactions between the tumor, its microenvironment, angiogenesis, and tumor antigen-specific T-cell responses. An improved understanding of the mechanisms and interactions responsible for immune evasion and tumor cell release from dormancy would help identify and aid in the development of novel targeted therapeutics. One such mediator of dormancy is myeloid derived suppressor cells (MDSC), whose number in the peripheral blood (PB) or infiltrating tumors has been associated with cancer stage, grade, patient survival, and metastasis in a broad range of tumor pathologies. Thus, extensive studies have revealed a role for MDSCs in tumor escape from adoptive and innate immune responses, facilitating tumor progression and metastasis; however, few studies have considered their role in dormancy. We have posited that MDSCs may regulate disseminated tumor cells resulting in resurgence of senescent tumor cells. In this review, we discuss clinical studies that address mechanisms of tumor recurrence including from dormancy, the role of MDSCs in their escape from dormancy during recurrence, the development of occult metastases, and the potential for MDSC inhibition as an approach to prolong the survival of patients with advanced malignancies. We stress that assessing the impact of therapies on MDSCs versus other cellular targets is challenging within the multimodality interventions required clinically.

Bone Metastases and Health in Prostate Cancer: From Pathophysiology to Clinical Implications

Clinically relevant bone metastases are a major cause of morbidity and mortality for prostate cancer patients. Distinct phenotypes are described: osteoblastic, the more common osteolytic and mixed. A molecular classification has been also proposed. Bone metastases start with the tropism of cancer cells to the bone through different multi-step tumor-host interactions, as described by the "metastatic cascade" model. Understanding these mechanisms, although far from being fully elucidated, could offer several potential targets for prevention and therapy. Moreover, the prognosis of patients is markedly influenced by skeletal-related events. They can be correlated not only with bone metastases, but also with "bad" bone health. There is a close correlation between osteoporosis-a skeletal disorder with decreased bone mass and qualitative alterations-and prostate cancer, in particular when treated with androgen deprivation therapy, a milestone in its treatment. Systemic treatments for prostate cancer, especially with the newest options, have improved the survival and quality of life of patients with respect to skeletal-related events; however, all patients should be evaluated for "bone health" and osteoporotic risk, both in the presence and in the absence of bone metastases. Treatment with bone-targeted therapies should be evaluated even in the absence of bone metastases, as described in special guidelines and according to a multidisciplinary evaluation.

Targeting integrin pathways: mechanisms and advances in therapy

Integrins are considered the main cell-adhesion transmembrane receptors that play multifaceted roles as extracellular matrix (ECM)-cytoskeletal linkers and transducers in biochemical and mechanical signals between cells and their environment in a wide range of states in health and diseases. Integrin functions are dependable on a delicate balance between active and inactive status via multiple mechanisms, including protein-protein interactions, conformational changes, and trafficking. Due to their exposure on the cell surface and sensitivity to the molecular blockade, integrins have been investigated as pharmacological targets for nearly 40 years, but given the complexity of integrins and sometimes opposite characteristics, targeting integrin therapeutics has been a challenge. To date, only seven drugs targeting integrins have been successfully marketed, including abciximab, eptifibatide, tirofiban, natalizumab, vedolizumab, lifitegrast, and carotegrast. Currently, there are approximately 90 kinds of integrin-based therapeutic drugs or imaging agents in clinical studies, including small molecules, antibodies, synthetic mimic peptides, antibody-drug conjugates (ADCs), chimeric antigen receptor (CAR) T-cell therapy, imaging agents, etc. A serious lesson from past integrin drug discovery and research efforts is that successes rely on both a deep understanding of integrin-regulatory mechanisms and unmet clinical needs. Herein, we provide a systematic and complete review of all integrin family members and integrin-mediated downstream signal transduction to highlight ongoing efforts to develop new therapies/diagnoses from bench to clinic. In addition, we further discuss the trend of drug development, how to improve the success rate of clinical trials targeting integrin therapies, and the key points for clinical research, basic research, and translational research.

Role of Interleukin-1 family in bone metastasis of prostate cancer

Prostate cancer (PCa) is one of the most fatal diseases in male patients with high bone metastatic potential. Bone metastasis severely shortens overall survival and brings skeletal-related events (SREs) which reduces the life quality of patients, and this situation is currently regarded as irreversible and incurable. The progression and metastasis of PCa are found to be closely associated with inflammatory cytokines and chemokines. As pivotal members of inflammatory cytokines, Interleukin-1 (IL-1) family plays a crucial role in this process. Elevated expression of IL-1 family was detected in PCa patients with bone metastasis, and accumulating evidences proved that IL-1 family could exert vital effects on the progression and bone metastasis of many cancers, while some members have dual effects. In this review, we discuss the role of IL-1 family in the bone metastasis of PCa. Furthermore, we demonstrate that many members of IL-1 family could act as pivotal biomarkers to predict the clinical stage and prognosis of PCa patients. More importantly, we have elucidated the role of IL-1 family in the bone metastasis of PCa, which could provide potential targets for the treatment of PCa bone metastasis and probable directions for future research.

Autocrine pro-legumain promotes breast cancer metastasis via binding to integrin αvβ3

Tumor metastasis is the leading cause of cancer-associated mortality. Unfortunately, the underlying mechanism of metastasis is poorly understood. Expression of legumain (LGMN), an endo-lysosomal cysteine protease, positively correlates with breast cancer metastatic progression and poor prognosis. Here, we report that LGMN is secreted in the zymogen form by motile breast cancer cells. Through binding to cell surface integrin αvβ3 via an RGD motif, the autocrine pro-LGMN activates FAK-Src-RhoA signaling in cancer cells and promotes cancer cell migration and invasion independent of LGMN protease activity. Either silencing LGMN expression or mutationally abolishing pro-LGMN‒αvβ3 interaction significantly inhibits cancer cell migration and invasion in vitro and breast cancer metastasis in vivo. Finally, we developed a monoclonal antibody against LGMN RGD motif, which blocks pro-LGMN‒αvβ3 binding, and effectively suppresses cancer cell migration and invasion in vitro and breast cancer metastasis in vivo. Thus, disruption of pro-LGMN‒integrin αvβ3 interaction may be a potentially promising strategy for treating breast cancer metastasis.

Tumor Cell-Induced Platelet Aggregation as an Emerging Therapeutic Target for Cancer Therapy

Tumor cells have the ability to induce platelet activation and aggregation. This has been documented to be involved in tumor progression in several types of cancers, such as lung, colon, breast, pancreatic, ovarian, and brain. During the process, platelets protect circulating tumor cells from the deleterious effects of shear forces, shield tumor cells from the immune system, and provide growth factors, facilitating metastatic spread and tumor growth at the original site as well as at the site of metastasis. Herein, we present a wider view on the induction of platelet aggregation by specific factors primarily developed by cancer, including coagulation factors, adhesion receptors, growth factors, cysteine proteases, matrix metalloproteinases, glycoproteins, soluble mediators, and selectins. These factors may be presented on the surface of tumor cells as well as in their microenvironment, and some may trigger more than just one simple receptor–ligand mechanism. For a better understanding, we briefly discuss the physiological role of the factors in the platelet activation process, and subsequently, we provide scientific evidence and discuss their potential role in the progression of specific cancers. Targeting tumor cell-induced platelet aggregation (TCIPA) by antiplatelet drugs may open ways to develop new treatment modalities. On the one hand, it may affect patients’ prognosis by enhancing known therapies in advanced-stage tumors. On the other hand, the use of drugs that are mostly easily accessible and widely used in general practice may be an opportunity to propose an unparalleled antitumor prophylaxis. In this review, we present the recent discoveries of mechanisms by which cancer cells activate platelets, and discuss new platelet-targeted therapeutic strategies.

Spontaneously Restoring Specific Bioaffinity of RGD in Linear RGD-containing Peptides by Conjugation with Zwitterionic Dendrimers

Peptides are more versatile than small molecule drugs, but their specific bioaffinities are usually lower than their original native proteins because of the loss of preferred conformations. To overcome this key obstacle, we demonstrated a hydrogen bond-induced conformational constraint method to enhance the specific bioaffinities of peptides to achieve a high success rate by using linear RGD-containing peptides as a model of bioactive peptides. By performing molecular simulation, we found that the chemically immobilized linear CRGDS via cysteine (C) at the N-terminus on zwitterionic PAMAM G-5 can not only spontaneously restore the natural conformation of the RGD segment through the assistance of the dynamic hydrogen bond from serine (S) at the C-terminus of the peptide, but it can also narrow the distribution of all possible conformations. Consequently, the conjugates showed comparable or even better high affinity than native proteins without the use of conventional, labor-intensive, synthesis-based structure search methods to construct a binding conformation. In addition, the conjugates showed globular protein-like characteristics chemically, physically, and physiologically. They exhibited not only high efficacy and biosafety both in vitro and in vivo, but they also showed extremely high thermostability even upon boiling in a solution. This approach offers great design flexibility for reviving functional peptides without impairing their high specific affinity for their targets. STATEMENT OF SIGNIFICANCE: : In this work, we developed a swift approach to spontaneously restore the natural conformation of a linear peptide from a nature protein and thus enhance its specific bioaffinity instead of constructing a binding conformation by the labor-intensive, synthesis-based structure search method. In details, our new approach involves dynamically constraining the linear peptide on a zwitterionic PAMAM G-5 surface by a combination of chemical bonding at one terminus and dynamic hydrogen bonding at the other terminus of the linear peptide. The zwitterionic background offers abundant interaction sites for hydrogen bonding as well as resistance to nonspecific interactions. This approach fully restores the specific bioaffinity of RGD segments on a zwitterionic PAMAM G-5 through only one conjugation point at the C-terminus of the peptide. Moreover, the bioaffinity of all three types of RGD-containing peptides is successfully restored, which indicates the high rate of success of this approach in affinity restoring.

Role of p38 MAP kinase in cancer stem cells and metastasis

Therapeutic resistance and metastatic progression are responsible for the majority of cancer mortalities. In particular, the development of resistance is a significant barrier to the efficacy of cancer treatments such as chemotherapy, radiotherapy, targeted therapies, and immunotherapies. Cancer stem cells (CSCs) underlie treatment resistance and metastasis. p38 mitogen-activated protein kinase (p38 MAPK) is downstream of several CSC-specific signaling pathways, and it plays an important role in CSC development and maintenance and contributes to metastasis and chemoresistance. Therefore, the development of therapeutic approaches targeting p38 can sensitize tumors to chemotherapy and prevent metastatic progression.

SPARC Induces E-Cadherin Repression and Enhances Cell Migration through Integrin αvβ3 and the Transcription Factor ZEB1 in Prostate Cancer Cells

Secreted protein acidic and rich in cysteine (SPARC), or osteonectin, is a matricellular protein that modulates interactions between cells and their microenvironment. SPARC is expressed during extracellular matrix remodeling and is abundant in bone marrow and high-grade prostate cancer (PCa). In PCa, SPARC induces changes associated with epithelial–mesenchymal transition (EMT), enhancing migration and invasion and increasing the expression of EMT transcriptional factor Zinc finger E-box-binding homeobox 1 (ZEB1), but not Zinc finger protein SNAI1 (Snail) or Zinc finger protein SNAI2 (Slug). It is unknown whether the SPARC-induced downregulation of E-cadherin in PCa cells depends on ZEB1. Several integrins are mediators of SPARC effects in cancer cells. Because integrin signaling can induce EMT programs, we hypothesize that SPARC induces E-cadherin repression through the activation of integrins and ZEB1. Through stable knockdown and the overexpression of SPARC in PCa cells, we demonstrate that SPARC downregulates E-cadherin and increases vimentin, ZEB1, and integrin β3 expression. Knocking down SPARC in PCa cells decreases the tyrosine-925 phosphorylation of FAK and impairs focal adhesion formation. Blocking integrin αvβ3 and silencing ZEB1 revert both the SPARC-induced downregulation of E-cadherin and cell migration enhancement. We conclude that SPARC induces E-cadherin repression and enhances PCa cell migration through the integrin αvβ3/ZEB1 signaling pathway.

Evidence That β1-Integrin Is Required for the Anti-Viability and Anti-Proliferative Effect of Resveratrol in CRC Cells

The β1-integrin receptor is broadly expressed on tumor and other cells in the tumor microenvironment (TME), and is an unfavorable prognostic factor for cancers. Nature-derived resveratrol has preventive and apoptotic effects on tumors, but whether resveratrol can exert its suppressive actions on TME-induced tumorigenesis through β1-integrin on the surface of CRC cells is still unknown. HCT116 or SW480 cells were exposed to inhibitory antibodies against β1-integrin, bacitracin (selective β1-integrin inhibitor), integrin-binding RGD (Arg-Gly-Asp) peptide, and/or resveratrol. We evaluated the anti-tumor actions and signaling impacts of resveratrol in colorectal cancer (CRC)-TME. We found that resveratrol completely altered the β1-integrin distribution pattern and expression on the surface of CRC cells in TME. Moreover, resveratrol down-regulated CRC cell proliferation, colony formation, viability, and up-regulated apoptosis in a concentration-dependent way. These actions of resveratrol were antagonized mainly by inhibitory antibodies against β1-integrin but not β5-integrin, and by an integrin-binding RGD peptide but not by RGE peptide, and by bacitracin in TME. Similarly, resveratrol-blocked TME-induced p65-NF-kB and its promoted gene markers linked to proliferation (cyclin D1), invasion (focal adhesion kinase, FAK), or apoptosis (caspase-3), were largely abrogated by anti-β1-integrin or RGD peptide, suggesting that β1-integrin is a potential transmission pathway for resveratrol/integrin down-stream signaling in CRC cells. The current results highlight, for the first time, the important gateway role of β1-integrins as signal carriers for resveratrol on the surfaces of HCT116 and SW480 cells, and their functional cooperation for the modulatory effects of resveratrol on TME-promoted tumorigenesis.

Macrophages Cytokine Spp1 Increases Growth of Prostate Intraepithelial Neoplasia to Promote Prostate Tumor Progression

Prostate cancer development and progression are associated with increased infiltrating macrophages. Prostate cancer is derived from prostatic intraepithelial neoplasia (PIN) lesions. However, the effects macrophages have on PIN progression remain unclear. Here, we showed that the recruited macrophages adjacent to PIN expressed M2 macrophage markers. In addition, high levels of Spp1 transcripts, also known as osteopontin, were identified in these macrophages. Extraneously added Spp1 accelerated PIN cell proliferation through activation of Akt and JNK in a 3D culture setting. We also showed that PIN cells expressed CD44, integrin αv, integrin β1, and integrin β3, all of which have been previously reported as receptors for Spp1. Finally, blockade of Akt and JNK activation through their specific inhibitor completely abolished macrophage Spp1-induced cell proliferation of PIN. Hence, our data revealed Spp1 as another macrophage cytokine/growth factor and its mediated mechanism to upregulate PIN cell growth, thus promoting prostate cancer development.

Advances in CAR-T Cell Genetic Engineering Strategies to Overcome Hurdles in Solid Tumors Treatment

During this last decade, adoptive transfer of T lymphocytes genetically modified to express chimeric antigen receptors (CARs) emerged as a valuable therapeutic strategy in hematological cancers. However, this immunotherapy has demonstrated limited efficacy in solid tumors. The main obstacle encountered by CAR-T cells in solid malignancies is the immunosuppressive tumor microenvironment (TME). The TME impedes tumor trafficking and penetration of T lymphocytes and installs an immunosuppressive milieu by producing suppressive soluble factors and by overexpressing negative immune checkpoints. In order to overcome these hurdles, new CAR-T cells engineering strategies were designed, to potentiate tumor recognition and infiltration and anti-cancer activity in the hostile TME. In this review, we provide an overview of the major mechanisms used by tumor cells to evade immune defenses and we critically expose the most optimistic engineering strategies to make CAR-T cell therapy a solid option for solid tumors.

A Small Molecule–Drug Conjugate (SMDC) Consisting of a Modified Camptothecin Payload Linked to an αVß3 Binder for the Treatment of Multiple Cancer Types

To improve tumor selectivity of cytotoxic agents, we designed VIP236, a small molecule–drug conjugate consisting of an αVβ3 integrin binder linked to a modified camptothecin payload (VIP126), which is released by the enzyme neutrophil elastase (NE) in the tumor microenvironment (TME). The tumor targeting and pharmacokinetics of VIP236 were studied in tumor-bearing mice by in vivo near-infrared imaging and by analyzing tumor and plasma samples. The efficacy of VIP236 was investigated in a panel of cancer cell lines in vitro, and in MX-1, NCI-H69, and SW480 murine xenograft models. Imaging studies with the αVβ3 binder demonstrated efficient tumor targeting. Administration of VIP126 via VIP236 resulted in a 10-fold improvement in the tumor/plasma ratio of VIP126 compared with VIP126 administered alone. Unlike SN38, VIP126 is not a substrate of P-gp and BCRP drug transporters. VIP236 presented strong cytotoxic activity in the presence of NE. VIP236 treatment resulted in tumor regressions and very good tolerability in all in vivo models tested. VIP236 represents a novel approach for delivering a potent cytotoxic agent by utilizing αVβ3 as a targeting moiety and NE in the TME to release the VIP126 payload—designed for high permeability and low efflux—directly into the tumor stroma.

The Extracellular Matrix in Soft Tissue Sarcomas: Pathobiology and Cellular Signalling

Soft tissue sarcomas are rare cancers of mesenchymal origin or differentiation comprising over 70 different histological subtypes. Due to their mesenchymal differentiation, sarcomas are thought to produce and deposit large quantities of extracellular matrix (ECM) components. Interactions between ECM ligands and their corresponding adhesion receptors such as the integrins and the discoidin domain receptors play key roles in driving many fundamental oncogenic processes including uncontrolled proliferation, cellular invasion and altered metabolism. In this review, we focus on emerging studies that describe the key ECM components commonly found in soft tissue sarcomas and discuss preclinical and clinical evidence outlining the important role that these proteins and their cognate adhesion receptors play in sarcomagenesis. We conclude by providing a perspective on the need for more comprehensive in-depth analyses of both the ECM and adhesion receptor biology in multiple histological subtypes in order to identify new drug targets and prognostic biomarkers for this group of rare diseases of unmet need.

Main Factors Involved in Thyroid Hormone Action

The thyroid hormone receptors are the mediators of a multitude of actions by the thyroid hormones in cells. Most thyroid hormone activities require interaction with nuclear receptors to bind DNA and regulate the expression of target genes. In addition to genomic regulation, thyroid hormones function via activation of specific cytosolic pathways, bypassing interaction with nuclear DNA. In the present work, we reviewed the most recent literature on the characteristics and roles of different factors involved in thyroid hormone function in particular, we discuss the genomic activity of thyroid hormone receptors in the nucleus and the functions of different thyroid hormone receptor isoforms in the cytosol. Furthermore, we describe the integrin αvβ3-mediated thyroid hormone signaling pathway and its rapid nongenomic action in the cell. We furthermore reviewed the thyroid hormone transporters enabling the uptake of thyroid hormones in the cell, and we also include a paragraph on the proteins that mediate thyroid receptors’ shuttling from the nucleus to the cytosol.

Mechanisms, Diagnosis and Treatment of Bone Metastases

Bone and bone marrow are among the most frequent metastatic sites of cancer. The occurrence of bone metastasis is frequently associated with a dismal disease outcome. The prevention and therapy of bone metastases is a priority in the treatment of cancer patients. However, current therapeutic options for patients with bone metastatic disease are limited in efficacy and associated with increased morbidity. Therefore, most current therapies are mainly palliative in nature. A better understanding of the underlying molecular pathways of the bone metastatic process is warranted to develop novel, well-tolerated and more successful treatments for a significant improvement of patients' quality of life and disease outcome. In this review, we provide comparative mechanistic insights into the bone metastatic process of various solid tumors, including pediatric cancers. We also highlight current and innovative approaches to biologically targeted therapy and immunotherapy. In particular, we discuss the role of the bone marrow microenvironment in the attraction, homing, dormancy and outgrowth of metastatic tumor cells and the ensuing therapeutic implications. Multiple signaling pathways have been described to contribute to metastatic spread to the bone of specific cancer entities, with most knowledge derived from the study of breast and prostate cancer. However, it is likely that similar mechanisms are involved in different types of cancer, including multiple myeloma, primary bone sarcomas and neuroblastoma. The metastatic rate-limiting interaction of tumor cells with the various cellular and noncellular components of the bone-marrow niche provides attractive therapeutic targets, which are already partially exploited by novel promising immunotherapies.

RGD engineered dendrimer nanotherapeutic as an emerging targeted approach in cancer therapy

A bird's eye view is now demanded in the area of cancer research to suppress the suffering of cancer patient and mediate the lack of treatment related to chemotherapy. Chemotherapy is always preferred over surgery or radiation therapy, but they never met the patient's demand of safe medication. Targeted therapy has now been in research that could hinder the unnecessary effect of drug on normal cells but could affect the tumor cells in much efficient manner. Angiogenesis is process involved in development of new blood vessel that nourishes tumor growth. Integrin receptors are over expressed on cancer cells that play vital role in angiogenesis for growth and metastasis of tumor cell. A delivery of RGD based peptide to integrin targeted site could help in its successful binding and liberation of drug in tumor vasculature. Dendrimers, in addition to its excellent pharmacokinetic properties also helps to carry targeting ligand to site of tumor by successfully conjugating with them. The aim of this review is to bring light upon the role of integrin in cancer progression, interaction of RGD to integrin receptor and more importantly the RGD-dendrimer based targeted therapy for the treatment of various cancers.

Anti-Cancer Effects of Cyclic Peptide ALOS4 in a Human Melanoma Mouse Model

We examined the effects of ALOS4, a cyclic peptide discovered previously by phage library selection against integrin α_vβ₃, on a human melanoma (A375) xenograft model to determine its abilities as a potential anti-cancer agent. We found that ALOS4 promoted healthy weight gain in A375-engrafted nude mice and reduced melanoma tumor mass and volume. Despite these positive changes, examination of the tumor tissue did not indicate any significant effects on proliferation, mitotic index, tissue vascularization, or reduction of αSMA or Ki-67 tumor markers. Modulation in overall expression of critical downstream α_vβ₃ integrin factors, such as FAK and Src, as well as reductions in gene expression of c-Fos and c-Jun transcription factors, indirectly confirmed our suspicions that ALOS4 is likely acting through an integrin-mediated pathway. Further, we found no overt formulation issues with ALOS4 regarding interaction with standard inert laboratory materials (polypropylene, borosilicate glass) or with pH and temperature stability under prolonged storage. Collectively, ALOS4 appears to be safe, chemically stable, and produces anti-cancer effects in a human xenograft model of melanoma. We believe these results suggest a role for ALOS4 in an integrin-mediated pathway in exerting its anti-cancer effects possibly through immune response modulation.

Integrins Within the Tumor Microenvironment: Biological Functions, Importance for Molecular Targeting, and Cancer Therapeutics Innovation

Many cellular functions important for solid tumor initiation and progression are mediated by members of the integrin family, a diverse family of cell attachment receptors. With recent studies emphasizing the role of the tumor microenvironment (TME) in tumor initiation and progression, it is not surprising that considerable attention is being paid to integrins. Several integrin antagonists are under clinical trials, with many demonstrating promising activity in patients with different cancers. A deeper knowledge of the functions of integrins within the TME is still required and might lead to better inhibitors being discovered. Integrin expression is commonly dysregulated in many tumors with integrins playing key roles in signaling as well as promotion of tumor cell invasion and migration. Integrins also play a major role in adhesion of circulating tumor cells to new sites and the resulting formation of secondary tumors. Furthermore, integrins have demonstrated the ability to promoting stem cell-like properties in tumor cells as well as drug resistance. Anti-integrin therapies rely heavily on the doses or concentrations used as these determine whether the drugs act as antagonists or as integrin agonists. This expert review offers the latest synthesis in terms of the current knowledge of integrins functions within the TME and as potential molecular targets for cancer therapeutics innovation.

Osteoblast-Derived Paracrine and Juxtacrine Signals Protect Disseminated Breast Cancer Cells from Stress

Metastatic breast cancer in bone is incurable and there is an urgent need to develop new therapeutic approaches to improve survival. Key to this is understanding the mechanisms governing cancer cell survival and growth in bone, which involves interplay between malignant and accessory cell types. Here, we performed a cellular and molecular comparison of the bone microenvironment in mouse models representing either metastatic indolence or growth, to identify mechanisms regulating cancer cell survival and fate. In vivo, we show that regardless of their fate, breast cancer cells in bone occupy niches rich in osteoblastic cells. As the number of osteoblasts in bone declines, so does the ability to sustain large numbers of breast cancer cells and support metastatic outgrowth. In vitro, osteoblasts protected breast cancer cells from death induced by cell stress and signaling via gap junctions was found to provide important juxtacrine protective mechanisms between osteoblasts and both MDA-MB-231 (TNBC) and MCF7 (ER+) breast cancer cells. Combined with mathematical modelling, these findings indicate that the fate of DTCs is not controlled through the association with specific vessel subtypes. Instead, numbers of osteoblasts dictate availability of protective niches which breast cancer cells can colonize prior to stimulation of metastatic outgrowth.

Tumor acidic microenvironment-induced drug release of RGD peptide nanoparticles for cellular uptake and cancer therapy

Spatial accuracy is crucial in drug delivery, especially to increase the efficacy and reduce the side effects of antitumor drugs. In this study, we developed a simple and broadly applicable strategy in which a target peptide ligand was introduced to construct a pH-responsive drug-loading system to achieve targeted delivery and drug release in lesions. In addition to reaching the tumor tissue through passive targeting modalities such as the enhanced permeability and retention (EPR) effect, active targeting nanoparticles used RGD motifs coupled to nanocarriers to specifically bind certain integrins, such as ανβ3, which is expressed on the surface of tumor cells, to achieve active tumor cell targeting. Self-assembling peptides have significant advantages in their structural design. The amphiphilic peptide LKR could form a spherical and self-assembled nanoparticle, which encapsulated the fat-soluble antitumor drug doxorubicin (Dox) in neutral medium. The Dox-encapsulating peptide nanoparticles swelled and burst, rapidly releasing Dox in an acidic microenvironment. Flow cytometry and fluorescence detection showed that the self-assembled LKR nanoparticles enhanced the drug accumulation in tumor cells compared with normal mammalian cells. The Dox-encapsulating peptide nanoparticles exhibited desirable antitumor effects in vivo. In summary, the acidic microenvironment of tumors was used to induce drug release from a targeted peptide drug-loading system to enhance cellular uptake and therapeutic effects in situ, providing a promising therapeutic approach for the treatment of major diseases such as hepatoma.

Integrin Alpha V in Urine: A Novel Noninvasive Marker for Prostate Cancer Detection

Prostate cancer (PCa) diagnosis based on patient urine analysis provides non-invasive and promising method as compared to biopsy and a prostate-specific antigen (PSA) test. This study was conceived to investigate whether Integrin alpha V (ITGAV) protein is present in urine and assess the urinary ITGAV diagnostic potential for PCa. Materials and Methods: Urinary ITGAV expression was determined by Western blot analysis and quantified by ELISA in urine from men with PCa (n = 47), benign prostate hyperplasia (n = 42) and age-matched controls (n = 22). Results: The level of ITGAV protein was significantly lower in PCa urine samples as compared to those in the control group (p < 0.00001). The decrease of ITGAV in urine was highly predictive of PCa with 91.5% sensitivity, 91.4% specificity, 0.93 area under the ROC curve, and its specificity was better than that of serum PSA. Conclusion: Urinary ITGAV provides a novel noninvasive biomarker with high specificity.

Potential Roles of Muscle-Derived Extracellular Vesicles in Remodeling Cellular Microenvironment: Proposed Implications of the Exercise-Induced Myokine, Irisin

Extracellular vesicles (EVs) have emerged as key players of intercellular communication and mediate crosstalk between tissues. Metastatic tumors release tumorigenic EVs, capable of pre-conditioning distal sites for organotropic metastasis. Growing evidence identifies muscle cell-derived EVs and myokines as potent mediators of cellular differentiation, proliferation, and metabolism. Muscle-derived EVs cargo myokines and other biological modulators like microRNAs, cytokines, chemokines, and prostaglandins hence, are likely to modulate the remodeling of niches in vital sites, such as liver and adipose tissues. Despite the scarcity of evidence to support a direct relationship between muscle-EVs and cancer metastasis, their indirect attribution to the regulation of niche remodeling and the establishment of pre-metastatic homing niches can be put forward. This hypothesis is supported by the role of muscle-derived EVs in findings gathered from other pathologies like inflammation and metabolic disorders. In this review, we present and discuss studies that evidently support the potential roles of muscle-derived EVs in the events of niche pre-conditioning and remodeling of metastatic tumor microenvironment. We highlight the potential contributions of the integrin-mediated interactions with an emerging myokine, irisin, to the regulation of EV-driven microenvironment remodeling in tumor metastasis. Further research into muscle-derived EVs and myokines in cancer progression is imperative and may hold promising contributions to advance our knowledge in the pathophysiology, progression and therapeutic management of metastatic cancers.

Differential expression of αVβ3 and αVβ6 integrins in prostate cancer progression

Neuroendocrine prostate cancer (NEPrCa) arises de novo or after accumulation of genomic alterations in pre-existing adenocarcinoma tumors in response to androgen deprivation therapies. We have provided evidence that small extracellular vesicles released by PrCa cells and containing the αVβ3 integrin promote neuroendocrine differentiation of PrCa in vivo and in vitro. Here, we examined αVβ3 integrin expression in three murine models carrying a deletion of PTEN (SKO), PTEN and RB1 (DKO), or PTEN, RB1 and TRP53 (TKO) genes in the prostatic epithelium; of these three models, the DKO and TKO tumors develop NEPrCa with a gene signature comparable to those of human NEPrCa. Immunostaining analysis of SKO, DKO and TKO tumors shows that αVβ3 integrin expression is increased in DKO and TKO primary tumors and metastatic lesions, but absent in SKO primary tumors. On the other hand, SKO tumors show higher levels of a different αV integrin, αVβ6, as compared to DKO and TKO tumors. These results are confirmed by RNA-sequencing analysis. Moreover, TRAMP mice, which carry NEPrCa and adenocarcinoma of the prostate, also have increased levels of αVβ3 in their NEPrCa primary tumors. In contrast, the αVβ6 integrin is only detectable in the adenocarcinoma areas. Finally, analysis of 42 LuCaP patient-derived xenografts and primary adenocarcinoma samples shows a positive correlation between αVβ3, but not αVβ6, and the neuronal marker synaptophysin; it also demonstrates that αVβ3 is absent in prostatic adenocarcinomas. In summary, we demonstrate that αVβ3 integrin is upregulated in NEPrCa primary and metastatic lesions; in contrast, the αVβ6 integrin is confined to adenocarcinoma of the prostate. Our findings suggest that the αVβ3 integrin, but not αVβ6, may promote a shift in lineage plasticity towards a NE phenotype and might serve as an informative biomarker for the early detection of NE differentiation in prostate cancer.

Targeting cancer metastasis with antibody therapeutics

Cancer metastasis, the spread of disease from a primary to a distal site through the circulatory or lymphatic systems, accounts for over 90% of all cancer related deaths. Despite significant progress in the field of cancer therapy in recent years, mortality rates remain dramatically higher for patients with metastatic disease versus those with local or regional disease. Although there is clearly an urgent need to develop drugs that inhibit cancer spread, the overwhelming majority of anticancer therapies that have been developed to date are designed to inhibit tumor growth but fail to address the key stages of the metastatic process: invasion, intravasation, circulation, extravasation, and colonization. There is growing interest in engineering targeted therapeutics, such as antibody drugs, that inhibit various steps in the metastatic cascade. We present an overview of antibody therapeutic approaches, both in the pipeline and in the clinic, that disrupt the essential mechanisms that underlie cancer metastasis. These therapies include classes of antibodies that indirectly target metastasis, including anti-integrin, anticadherin, and immune checkpoint blocking antibodies, as well as monoclonal and bispecific antibodies that are specifically designed to interrupt disease dissemination. Although few antimetastatic antibodies have achieved clinical success to date, there are many promising candidates in various stages of development, and novel targets and approaches are constantly emerging. Collectively, these efforts will enrich our understanding of the molecular drivers of metastasis, and the new strategies that arise promise to have a profound impact on the future of cancer therapeutic development. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Thy-1 (CD90)-Induced Metastatic Cancer Cell Migration and Invasion Are β3 Integrin-Dependent and Involve a Ca2+/P2X7 Receptor Signaling Axis

Cancer cell adhesion to the vascular endothelium is an important step in tumor metastasis. Thy-1 (CD90), a cell adhesion molecule expressed in activated endothelial cells, has been implicated in melanoma metastasis by binding to integrins present in cancer cells. However, the signaling pathway(s) triggered by this Thy-1-Integrin interaction in cancer cells remains to be defined. Our previously reported data indicate that Ca²⁺-dependent hemichannel opening, as well as the P2X7 receptor, are key players in Thy-1-α_Vβ₃ Integrin-induced migration of reactive astrocytes. Thus, we investigated whether this signaling pathway is activated in MDA-MB-231 breast cancer cells and in B16F10 melanoma cells when stimulated with Thy-1. In both cancer cell types, Thy-1 induced a rapid increase in intracellular Ca²⁺, ATP release, as well as cell migration and invasion. Connexin and Pannexin inhibitors decreased cell migration, implicating a requirement for hemichannel opening in Thy-1-induced cell migration. In addition, cell migration and invasion were precluded when the P2X7 receptor was pharmacologically blocked. Moreover, the ability of breast cancer and melanoma cells to transmigrate through an activated endothelial monolayer was significantly decreased when the β₃ Integrin was silenced in these cancer cells. Importantly, melanoma cells with silenced β₃ Integrin were unable to metastasize to the lung in a preclinical mouse model. Thus, our results suggest that the Ca²⁺/hemichannel/ATP/P2X7 receptor-signaling axis triggered by the Thy-1-α_Vβ₃ Integrin interaction is important for cancer cell migration, invasion and transvasation. These findings open up the possibility of therapeutically targeting the Thy-1-Integrin signaling pathway to prevent metastasis.

Kindlin-3 mutation in mesenchymal stem cells results in enhanced chondrogenesis

Identifying patient mutations driving skeletal development disorders has driven our understanding of bone development. Integrin adhesion deficiency disease is caused by a Kindlin-3 (fermitin family member 3) mutation, and its inactivation results in bleeding disorders and osteopenia. In this study, we uncover a role for Kindlin-3 in the differentiation of bone marrow mesenchymal stem cells (BMSCs) down the chondrogenic lineage. Kindlin-3 expression increased with chondrogenic differentiation, similar to RUNX2. BMSCs isolated from a Kindlin-3 deficient patient expressed chondrocyte markers, including SOX9, under basal conditions, which were further enhanced with chondrogenic differentiation. Rescue of integrin activation by a constitutively activated β₃ integrin construct increased adhesion to multiple extracellular matrices and reduced SOX9 expression to basal levels. Growth plates from mice expressing a mutated Kindlin-3 with the integrin binding site ablated demonstrated alterations in chondrocyte maturation similar to that seen with the human Kindlin-3 deficient BMSCs. These findings suggest that Kindlin-3 expression mirrors RUNX2 during chondrogenesis.

Osteopontin: A Key Regulator of Tumor Progression and Immunomodulation

Simple Summary

Anti-PD-1/PD-L1 and anti-CTLA-4-based immune checkpoint blockade (ICB) immunotherapy have recently emerged as a breakthrough in human cancer treatment. Durable efficacy has been achieved in many types of human cancers. However, not all human cancers respond to current ICB immunotherapy and only a fraction of the responsive cancers exhibit efficacy. Osteopontin (OPN) expression is highly elevated in human cancers and functions as a tumor promoter. Emerging data suggest that OPN may also regulate immune cell function in the tumor microenvironment. This review aims at OPN function in human cancer progression and new findings of OPN as a new immune checkpoint. We propose that OPN compensates PD-L1 function to promote tumor immune evasion, which may underlie human cancer non-response to current ICB immunotherapy.

Abstract

OPN is a multifunctional phosphoglycoprotein expressed in a wide range of cells, including osteoclasts, osteoblasts, neurons, epithelial cells, T, B, NK, NK T, myeloid, and innate lymphoid cells. OPN plays an important role in diverse biological processes and is implicated in multiple diseases such as cardiovascular, diabetes, kidney, proinflammatory, fibrosis, nephrolithiasis, wound healing, and cancer. In cancer patients, overexpressed OPN is often detected in the tumor microenvironment and elevated serum OPN level is correlated with poor prognosis. Initially identified in activated T cells and termed as early T cell activation gene, OPN links innate cells to adaptive cells in immune response to infection and cancer. Recent single cell RNA sequencing revealed that OPN is primarily expressed in tumor cells and tumor-infiltrating myeloid cells in human cancer patients. Emerging experimental data reveal a key role of OPN is tumor immune evasion through regulating macrophage polarization, recruitment, and inhibition of T cell activation in the tumor microenvironment. Therefore, in addition to its well-established direct tumor cell promotion function, OPN also acts as an immune checkpoint to negatively regulate T cell activation. The OPN protein level is highly elevated in peripheral blood of human cancer patients. OPN blockade immunotherapy with OPN neutralization monoclonal antibodies (mAbs) thus represents an attractive approach in human cancer immunotherapy.

Lebecetin, a snake venom C-type lectin protein, modulates LPS-induced inflammatory cytokine production in human THP-1-derived macrophages

The excessive production of inflammatory mediators results in an overactive immune response leading to the worsening of various human diseases. Thus, there is a still need to identify molecules able to regulate the inflammatory response. Lebecetin, a C-type lectin protein isolated from Macrovipera lebetina snake venom, was previously characterized as a platelet aggregation inhibitor and antitumor active biomolecule. In the present work, we investigated its effect on the production of some cytokines linked to inflammatory response and the underlying mechanisms in lipopolysaccharide (LPS)-induced THP1 macrophages. Interestingly, we found that lebecetin reduced the levels of the pro-inflammatory cytokines TNF-α, IL-6, and IL-8 while it partially increased LPS-induced secretion of the immunomodulatory cytokine IL-10. Furthermore, this modulatory effect was accompanied by decreased activation of ERK1/2, p38, AKT kinases and NF-κB along with reduced expression of αvβ3 integrin. Thus, this study highlights the promising role of lebecetin as a natural biomolecule that could manage the inflammatory response involved in the development and progression of inflammatory diseases.

Preclinical studies of a novel snake venom-derived recombinant disintegrin with antitumor activity: A review

Snake venoms consist of a complex mixture of many bioactive molecules. Among them are disintegrins, which are peptides without enzymatic activity, but with high binding affinity for integrins, transmembrane receptors that function to connect cells with components of the extracellular matrix. Integrin-mediated cell attachment is critical for cell migration and dissemination, as well as for signal transduction pathways involved in cell growth. During tumor development, integrins play key roles by supporting cancer cell proliferation, angiogenesis, and metastasis. The recognition that snake venom disintegrins can block integrin functions has spawned a number of studies to explore their cancer therapeutic potential. While dozens of different disintegrins have been isolated, none of them as yet has undergone clinical evaluation in cancer patients. Among the best-characterized and preclinically most advanced disintegrins is vicrostatin (VCN), a recombinant disintegrin that was rationally designed by fusing 62 N-terminal amino acids derived from the disintegrin contortrostatin with 6 C-terminal amino acids from echistatin, the disintegrins from another snake species. Bacterially produced VCN was shown to target multiple tumor-associated integrins, achieving potent anti-tumor and anti-angiogenic effects in in vitro and in vivo models in the absence of noticeable toxicity. This review will introduce the field of snake venom disintegrins as potential anticancer agents and illustrate the translational development and cancer-therapeutic potential of VCN as an example.

The dormant cancer cell life cycle

The success of targeted therapies and immunotherapies has created optimism that cancers may be curable. However, not all patients respond, drug resistance is common and many patients relapse owing to dormant cancer cells. These rare and elusive cells can disseminate early and hide in specialized niches in distant organs before being reactivated to cause disease relapse after successful treatment of the primary tumour. Despite their importance, we are yet to leverage knowledge generated from experimental models and translate the potential of targeting dormant cancer cells to prevent disease relapse in the clinic. This is due, at least in part, to the lack of adherence to consensus definitions by researchers, limited models that faithfully recapitulate this stage of metastatic spread and an absence of interdisciplinary approaches. However, the application of new high-resolution, single-cell technologies is starting to revolutionize the field and transcend classical reductionist models of studying individual cell types or genes in isolation to provide a global view of the complex underlying cellular ecosystem and transcriptional landscape that controls dormancy. In this Perspective, we synthesize some of these recent advances to describe the hallmarks of cancer cell dormancy and how the dormant cancer cell life cycle offers opportunities to target not only the cancer but also its environment to achieve a durable cure for seemingly incurable cancers.

Small extracellular vesicles modulated by αVβ3 integrin induce neuroendocrine differentiation in recipient cancer cells

The ability of small extracellular vesicles (sEVs) to reprogram cancer cells is well established. However, the specific sEV components able to mediate aberrant effects in cancer cells have not been characterized. Integrins are major players in mediating sEV functions. We have previously reported that the αVβ3 integrin is detected in sEVs of prostate cancer (PrCa) cells and transferred into recipient cells. Here, we investigate whether sEVs from αVβ3-expressing cells affect tumour growth differently than sEVs from control cells that do not express αVβ3. We compared the ability of sEVs to stimulate tumour growth, using sEVs isolated from PrCa C4-2B cells by iodixanol density gradient and characterized with immunoblotting, nanoparticle tracking analysis, immunocapturing and single vesicle analysis. We incubated PrCa cells with sEVs and injected them subcutaneously into nude mice to measure in vivo tumour growth or analysed in vitro their anchorage-independent growth. Our results demonstrate that a single treatment with sEVs shed from C4-2B cells that express αVβ3, but not from control cells, stimulates tumour growth and induces differentiation of PrCa cells towards a neuroendocrine phenotype, as quantified by increased levels of neuroendocrine markers. In conclusion, the expression of αVβ3 integrin generates sEVs capable of reprogramming cells towards an aggressive phenotype.

Interactions Between Tumor Biology and Targeted Nanoplatforms for Imaging Applications

Although considerable efforts have been conducted to diagnose, improve, and treat cancer in the past few decades, existing therapeutic options are insufficient, as mortality and morbidity rates remain high. Perhaps the best hope for substantial improvement lies in early detection. Recent advances in nanotechnology are expected to increase the current understanding of tumor biology, and will allow nanomaterials to be used for targeting and imaging both in vitro and in vivo experimental models. Owing to their intrinsic physicochemical characteristics, nanostructures (NSs) are valuable tools that have received much attention in nanoimaging. Consequently, rationally designed NSs have been successfully employed in cancer imaging for targeting cancer-specific or cancer-associated molecules and pathways. This review categorizes imaging and targeting approaches according to cancer type, and also highlights some new safe approaches involving membrane-coated nanoparticles, tumor cell-derived extracellular vesicles, circulating tumor cells, cell-free DNAs, and cancer stem cells in the hope of developing more precise targeting and multifunctional nanotechnology-based imaging probes in the future.

Targeting Integrins in Cancer Nanomedicine: Applications in Cancer Diagnosis and Therapy

Due to advancements in nanotechnology, the application of nanosized materials (nanomaterials) in cancer diagnostics and therapeutics has become a leading area in cancer research. The decoration of nanomaterial surfaces with biological ligands is a major strategy for directing the actions of nanomaterials specifically to cancer cells. These ligands can bind to specific receptors on the cell surface and enable nanomaterials to actively target cancer cells. Integrins are one of the cell surface receptors that regulate the communication between cells and their microenvironment. Several integrins are overexpressed in many types of cancer cells and the tumor microvasculature and function in the mediation of various cellular events. Therefore, the surface modification of nanomaterials with integrin-specific ligands not only increases their binding affinity to cancer cells but also enhances the cellular uptake of nanomaterials through the intracellular trafficking of integrins. Moreover, the integrin-specific ligands themselves interfere with cancer migration and invasion by interacting with integrins, and this finding provides a novel direction for new treatment approaches in cancer nanomedicine. This article reviews the integrin-specific ligands that have been used in cancer nanomedicine and provides an overview of the recent progress in cancer diagnostics and therapeutic strategies involving the use of integrin-targeted nanomaterials.

Peptide-Conjugated Nanoparticles as Targeted Anti-angiogenesis Therapeutic and Diagnostic in Cancer

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Targeting angiogenesis in the microenvironment of a tumor can enable suppression of tumor angiogenesis and delivery of anticancer drugs into the tumor. Anti-angiogenesis targeted delivery systems utilizing passive targeting such as Enhanced Permeability and Retention (EPR) and specific receptor-mediated targeting (active targeting) should result in tumor-specific targeting. One targeted anti-angiogenesis approach uses peptides conjugated to nanoparticles, which can be loaded with anticancer agents. Anti-angiogenesis agents can suppress tumor angiogenesis and thereby affect tumor growth progression (tumor growth arrest), which may be further reduced with the targetdelivered anticancer agent. This review provides an update of tumor vascular targeting for therapeutic and diagnostic applications, with conventional or long-circulating nanoparticles decorated with peptides that target neovascularization (anti-angiogenesis) in the tumor microenvironment.

Bone sialoprotein-αvβ3 integrin axis promotes breast cancer metastasis to the bone

The underlying mechanisms of breast cancer cells metastasizing to distant sites are complex and multifactorial. Bone sialoprotein (BSP) and αvβ3 integrin were reported to promote the metastatic progress of breast cancer cells, particularly metastasis to bone. Most theories presume that BSP promotes breast cancer metastasis by binding to αvβ3 integrin. Interestingly, we found the αvβ3 integrin decreased in BSP silenced cells (BSPi), which have weak ability to form bone metastases. However, the relevance of their expression in primary tumor and the way they participate in metastasis are not clear. In this study, we evaluated the relationship between BSP, αvβ3 integrin levels, and the bone metastatic ability of breast cancer cells in patient tissues, and the data indicated that the αvβ3 integrin level is closely correlated to BSP level and metastatic potential. Overexpression of αvβ3 integrin in cancer cells could reverse the effect of BSPi in vitro and promote bone metastasis in a mouse model, whereas knockdown of αvβ3 integrin have effects just like BSPi. Moreover, The Cancer Genome Atlas data and RT‐PCR analysis have also shown that SPP1, KCNK2, and PTK2B might be involved in this process. Thus, we propose that αvβ3 integrin is one of the downstream factors regulated by BSP in the breast cancer‐bone metastatic cascade.

Integrins as A New Target for Cancer Treatment

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Despite the great progress in the development of targeted therapies for different types of cancer utilizing monoclonal antibodies (e.g., cetuximab for colorectal cancer and head and neck cancer therapy), kinase inhibitors (e.g., sorafenib for kidney cancer and gastrointestinal stromal tumours therapy), and immunomodulatory treatments (e.g., nivolumab and pembrolizumab for melanoma therapy and lung cancer therapy), there is still a need to search for new, more effective treatments.

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Integrins are responsible for intercellular adhesion and interaction with the cellular matrix. The function of integrins is related to the transduction of intracellular signals associated with adhesion, migration, cell proliferation, differentiation, and apoptosis. Molecules targeting integrins that lead to cancer cell death have been developed. The most advanced molecules studied in clinical trials are abituzumab, intetumumab and cilengitide. There are different groups of anti-integrin drugs: monoclonal antibodies (e.g., abituzumab) and other such as cilengitide, E7820 and MK-0429. These drugs have been evaluated in various cancer types. However, they have shown modest efficacy, and none of them have yet been approved for cancer treatment. Studies have shown that patient selection using biomarkers might improve the efficacy of anti-integrin cancer treatment. Many preclinical models have demonstrated promising results using integrin visualization for cancer detection and treatment efficacy monitoring; however, these strategies require further evaluation in humans.

Antitumor activity of integrin αVβ3 antibody conjugated-cationic microbubbles in liver cancer

Background

The overexpression of integrin α_Vβ₃ in hepatocarcinoma (HCC) promotes tumor progression, metastasis, and clinical staging. Thus, the inhibition of integrin α_Vβ₃ might be potentially effective as an anti-cancer agent in HCC.

Methods

In this study, we aimed to investigate the antitumor effect of integrin α_Vβ₃ antibody conjugated cationic microbubbles (CMBs) in HCC model. By conjugating with integrin α_Vβ₃ antibody with non-targeting CMBs, CMBs_αvβ3 was constructed. The antitumor effect of CMBs_αvβ3 was evaluated in HepG2 cells in vitro and in HepG2 xenograft mice models. Bcl-2, p53 and CD31 mRNA level, and caspase-3 activity were examined in xenograft tumors. Cell proliferation assay and scratch test were performed to evaluate the anti-migrant effect of CMBs_αvβ3in vitro.

Results

CMBs_αvβ3 could specifically target to HCC HepG2 cells and improve pEGFP-KDRP-CD/TK plasmid transfection efficiency. In HepG2 xenograft mice models, CMBs_αvβ3 treatment significantly suppressed tumor weights and volumes. CMBs_αvβ3 treatment suppressed Bcl-2 and p53 mRNA level in tumors. In HepG2 cells, CMBs_αvβ3 significantly impaired wound healing and inhibited cell proliferation. Moreover, when combined with CD/TK double suicide gene transfection and 5-FC/GCV treatment, caspase-3 was activated and the cell proliferation was tremendously inhibited.

Conclusions

CMBs_αvβ3 not only suppresses cell migration and proliferation, but also facilitates 5-FC/GCV plus CD/TK double suicide gene-induced apoptotic cell death. CMBs_αvβ3 is a promising gene delivery agent with potential anti-tumor activity itself.

Osteopontin as a multifaceted driver of bone metastasis and drug resistance

Metastasis to bone frequently occurs in majority of patients with advanced breast cancer and prostate cancer, leading to devastating skeletal-related events and substantially reducing the survival of patients. Currently, the crosstalk between tumor cells and the bone stromal compartment was widely investigated for bone metastasis and the resistance to many conventional therapeutic methods. Osteopontin (OPN), also known as SPP1 (secreted phosphoprotein 1), a secreted and chemokine-like glyco-phosphoprotein is involved in tumor progression such as cell proliferation, angiogenesis, and metastasis. The expression of OPN in tumor tissue and plasma has been clinically proved to be correlated to poor prognosis and shortened survival in patients with breast cancer and prostate cancer. This review summarizes the multifaceted roles that OPN plays in bone microenvironment and drug resistance, with emphasis on breast and prostate cancers, via binding to αvβ3 integrin and CD44 receptor and inducing signaling cascades. We further discuss the promising therapeutic strategy for OPN targeting, mainly inhibiting OPN at transcriptional or protein level or blocking it binding to receptor or its downstream signaling pathways. The comprehending of the function of OPN in bone microenvironment is crucial for the development of novel biomarker and potential therapeutic target for the diagnosis and treatment of bone metastasis and against the emergence of drug resistance in advanced cancers.

Integrins, CAFs and Mechanical Forces in the Progression of Cancer

Cells respond to both chemical and mechanical cues present within their microenvironment. Various mechanical signals are detected by and transmitted to the cells through mechanoreceptors. These receptors often contact with the extracellular matrix (ECM), where the external signals are converted into a physiological response. Integrins are well-defined mechanoreceptors that physically connect the actomyosin cytoskeleton to the surrounding matrix and transduce signals. Families of α and β subunits can form a variety of heterodimers that have been implicated in cancer progression and differ among types of cancer. These heterodimers serve as the nexus of communication between the cells and the tumor microenvironment (TME). The TME is dynamic and composed of stromal cells, ECM and associated soluble factors. The most abundant stromal cells within the TME are cancer-associated fibroblasts (CAFs). Accumulating studies implicate CAFs in cancer development and metastasis through their remodeling of the ECM and release of large amounts of ECM proteins and soluble factors. Considering that the communication between cancer cells and CAFs, in large part, takes place through the ECM, the involvement of integrins in the crosstalk is significant. This review discusses the role of integrins, as the primary cell-ECM mechanoreceptors, in cancer progression, highlighting integrin-mediated mechanical communication between cancer cells and CAFs.