Emerging nanomedicine-based therapeutics for hematogenous metastatic cascade inhibition: Interfering with the crosstalk between "seed and soil"

Invasion and metastasis in cancer: molecular insights and therapeutic targets

The progression of malignant tumors leads to the development of secondary tumors in various organs, including bones, the brain, liver, and lungs. This metastatic process severely impacts the prognosis of patients, significantly affecting their quality of life and survival rates. Research efforts have consistently focused on the intricate mechanisms underlying this process and the corresponding clinical management strategies. Consequently, a comprehensive understanding of the biological foundations of tumor metastasis, identification of pivotal signaling pathways, and systematic evaluation of existing and emerging therapeutic strategies are paramount to enhancing the overall diagnostic and treatment capabilities for metastatic tumors. However, current research is primarily focused on metastasis within specific cancer types, leaving significant gaps in our understanding of the complex metastatic cascade, organ-specific tropism mechanisms, and the development of targeted treatments. In this study, we examine the sequential processes of tumor metastasis, elucidate the underlying mechanisms driving organ-tropic metastasis, and systematically analyze therapeutic strategies for metastatic tumors, including those tailored to specific organ involvement. Subsequently, we synthesize the most recent advances in emerging therapeutic technologies for tumor metastasis and analyze the challenges and opportunities encountered in clinical research pertaining to bone metastasis. Our objective is to offer insights that can inform future research and clinical practice in this crucial field.

An Advanced Multivalent Ligand-Decorated Microsphere Enrichment System Efficiently Captures Circulating Tumor Cells In Vivo

Capturing circulating tumor cells (CTCs) in vivo from the bloodstream lessens tumor metastasis and recurrence risks. However, the absence of CTC receptors due to epithelial-mesenchymal transition (EMT), the limited binding capacity of a single ligand, and the complexity of the blood flow environment significantly reduce the efficiency of CTC capture in vivo. Herein, a multivalent ligand-decorated microsphere enrichment system (MLMES) is crafted that incorporates a capture column replete with an immunosorbent that precisely recognizes and binds the stably expressed cluster of differentiation 44 (CD44) and glucose transporter protein 1 (GLUT1) receptors present on the exterior of CTCs. As peripheral blood flows through the column, CTCs are efficiently captured, achieving an in vivo capture rate of up to 64.2%, the highest reported to date. Moreover, the MLMES demonstrates excellent biocompatibility, broad-spectrum tumor cells capture, and storage stability. Importantly, it significantly eliminates a substantial quantity of CTCs from peripheral blood, reducing the risk of metastasis. This breakthrough method has broad clinical application potential in preventing tumor metastasis and recurrence, bringing new possibilities for improving cancer treatment.

The effect and mechanism of IL-37d on neutrophil recruitment in the early stage of tumor metastasis in the lungs

BACKGROUND

Chronic inflammation plays a pivotal role in cancer progression, with tumor-associated neutrophils (TANs) actively shaping the pre-metastatic niche. Interleukin-37 (IL-37), a known immunosuppressive cytokine, is implicated in this regulation, although its precise function remains underexplored.Therefore, this study seeks to further elucidate the inhibitory effect of IL-37d on neutrophil recruitment within the pre-metastatic lung microenvironment and its underlying mechanisms, thereby providing a theoretical foundation for clinical interventions in the early stages of cancer progression.

METHODS

This study investigates the impact of IL-37d on tumor growth, metastasis, and survival in a murine model, with a focus on the molecular mechanisms involved. Specifically, we explored IL-37d's ability to inhibit toll-like receptor 3 (TLR3) activation in lung epithelial cells, reduce calcium-binding proteins S100A8/A9 (S100a8/9) expression, and suppress matrix metalloproteinase 9 (MMP9) activity. We also examined IL-37d's effect on neutrophil migration from the bone marrow to the lungs during early metastasis.

RESULTS

IL-37d treatment significantly reduced lung metastasis and extended survival in mice. Mechanistically, IL-37d inhibited TLR3 activation, downregulated S100a8/9 expression, and reduced MMP9 activity, thereby impairing the migration of bone marrow-derived neutrophils to the lungs. This led to decreased neutrophil infiltration and a disruption of the pre-metastatic niche formation.

CONCLUSION

Our study represents the first investigation into the role of IL-37d in inhibiting tumor metastasis during the early stages by suppressing S100A8/9 and MMP9 expression in lung tissue, thereby reducing neutrophil recruitment and spontaneous migration from the bone marrow.

Role of Hypoxia and Rac1 Inhibition in the Metastatic Cascade

The hypoxic condition has a pivotal role in solid tumors and was shown to correlate with the poor outcome of anticancer treatments. Hypoxia contributes to tumor progression and leads to therapy resistance. Two forms of a hypoxic environment might have relevance in tumor mass formation: chronic and cyclic hypoxia. The main regulators of hypoxia are hypoxia-inducible factors, which regulate the cell survival, proliferation, motility, metabolism, pH, extracellular matrix function, inflammatory cells recruitment and angiogenesis. The metastatic process consists of different steps in which hypoxia-inducible factors can play an important role. Rac1, belonging to small G-proteins, is involved in the metastasis process as one of the key molecules of migration, especially in a hypoxic environment. The effect of hypoxia on the tumor phenotype and the signaling pathways which may interfere with tumor progression are already quite well known. Although the role of Rac1, one of the small G-proteins, in hypoxia remains unclear, predominantly, in vitro studies performed so far confirm that Rac1 inhibition may represent a viable direction for tumor therapy.

Role of imbalanced gut microbiota in promoting CRC metastasis: from theory to clinical application

Metastasis poses a major challenge in colorectal cancer (CRC) treatment and remains a primary cause of mortality among patients with CRC. Recent investigations have elucidated the involvement of disrupted gut microbiota homeostasis in various facets of CRC metastasis, exerting a pivotal influence in shaping the metastatic microenvironment, triggering epithelial-mesenchymal transition (EMT), and so on. Moreover, therapeutic interventions targeting the gut microbiota demonstrate promise in enhancing the efficacy of conventional treatments for metastatic CRC (mCRC), presenting novel avenues for mCRC clinical management. Grounded in the "seed and soil" hypothesis, this review consolidates insights into the mechanisms by which imbalanced gut microbiota promotes mCRC and highlights recent strides in leveraging gut microbiota modulation for the clinical prevention and treatment of mCRC. Emphasis is placed on the considerable potential of manipulating gut microbiota within clinical settings for managing mCRC.

Tumor immune microenvironment-modulated nanostrategy for the treatment of lung cancer metastasis

ABSTRACT

As one of the most malignant tumors worldwide, lung cancer, fueled by metastasis, has shown rising mortality rates. However, effective clinical strategies aimed at preventing metastasis are lacking owing to its dynamic multi-step, complicated, and progressive nature. Immunotherapy has shown promise in treating cancer metastasis by reversing the immunosuppressive network of the tumor microenvironment. However, drug resistance inevitably develops due to inadequate delivery of immunostimulants and an uncontrolled immune response. Consequently, adverse effects occur, such as autoimmunity, from the non-specific immune activation and non-specific inflammation in off-target organs. Nanocarriers that improve drug solubility, permeability, stability, bioavailability, as well as sustained, controlled, and targeted delivery can effectively overcome drug resistance and enhance the therapeutic effect while reducing adverse effects. In particular, nanomedicine-based immunotherapy can be utilized to target tumor metastasis, presenting a promising therapeutic strategy for lung cancer. Nanotechnology strategies that boost the immunotherapy effect are classified based on the metastatic cascade related to the tumor immune microenvironment; the breaking away of primary tumors, circulating tumor cell dissemination, and premetastatic niche formation cause distant secondary site colonization. In this review, we focus on the opportunities and challenges of integrating immunotherapy with nanoparticle formulation to establish nanotechnology-based immunotherapy by modulating the tumor microenvironment for preclinical and clinical applications in the management of patients with metastatic lung cancer. We also discuss prospects for the emerging field and the clinical translation potential of these techniques.

A Pro-Metastatic Derivatives Eliminator for In Vivo Dual-Removal of Circulating Tumor Cells and Tumor-Derived Exosomes Impedes their Biodistribution into Distant Organs

Circulating tumor cells (CTCs) and tumor-derived exosomes (TDEs) play an irreplaceable role in the metastatic cascade and preventing them from reaching distant organs via blood circulation helps to reduce the probability of cancer recurrence and metastasis. However, technologies that can simultaneously prevent CTCs and TDEs from reaching distant organs have not been thoroughly developed until now. Here, inspired by hemoperfusion, a pro-metastatic derivative eliminator (PMDE) is developed for the removal of both CTCs and TDEs from the peripheral blood, which also inhibits their biodistribution in distant organs. This device is designed with a dual antibody-modified immunosorbent filled into a capture column that draws peripheral blood out of the body to flow through the column to specifically capture CTCs and TDEs, followed by retransfusing the purified blood into the body. The PMDE can efficiently remove CTCs and TDEs from the peripheral blood and has excellent biocompatibility. Interestingly, the PMDE device can significantly inhibit the biodistribution of CTCs and TDEs in the lung and liver by scavenging them. This work provides a new perspective on anti-metastatic therapy and has broad prospects in clinical applications to prevent metastasis and recurrence.

Gold Nanoparticles Inhibit Extravasation of Canine Osteosarcoma Cells in the Ex Ovo Chicken Embryo Chorioallantoic Membrane Model

Canine osteosarcoma (OS) is an aggressive bone tumor with high metastatic potential and poor prognosis, mainly due to metastatic disease. Nanomedicine-based agents can be used to improve both primary and metastatic tumor treatment. Recently, gold nanoparticles were shown to inhibit different stages of the metastatic cascade in various human cancers. Here, we assessed the potential inhibitory effect of the glutathione-stabilized gold nanoparticles (Au-GSH NPs) on canine OS cells extravasation, utilizing the ex ovo chick embryo chorioallantoic membrane (CAM) model. The calculation of cells extravasation rates was performed using wide-field fluorescent microscopy. Transmission electron microscopy and Microwave Plasma Atomic Emission Spectroscopy revealed Au-GSH NPs absorption by OS cells. We demonstrated that Au-GSH NPs are non-toxic and significantly inhibit canine OS cells extravasation rates, regardless of their aggressiveness phenotype. The results indicate that Au-GSH NPs can act as a possible anti metastatic agent for OS treatment. Furthermore, the implemented CAM model may be used as a valuable preclinical platform in veterinary medicine, such as testing anti-metastatic agents.

Trauma-Responsive Scaffold Synchronizing Oncolysis Immunization and Inflammation Alleviation for Post-Operative Suppression of Cancer Metastasis

Tumor surgery can create an inflammatory trauma to aggravate residual tumor "seed" to colonize pre-metastatic niches (PMNs) "soil" at secondary sites, thereby promoting post-operative metastasis. However, two-pronged strategies for post-surgical elimination of asynchronous "seeds" and "soil" at different regions are currently lacking. Here, we have designed a hydrogel that can be injected into a resection cavity, where it immediately forms a scaffold and gradually degrades responding to enriched reactive oxygen species at adjacent trauma for local delivery and on-demand release of autologous cancer cells succumbing to oncolysis (ACCO) and anti-inflammatory agent. The autologous cell source self-provides a whole array of tumor-associated antigens, and the oncolysis orchestration of a subcellular cascade confers a self-adjuvanting property, together guaranteeing high immunogenicity of the ACCO vaccine that enables specific antitumor immunization. In parallel, inflammation alleviation exerted bidirectional functions to reshape the local immune landscape and resuscitate ACCO, leading to the eradication of residual tumor "seeds" while simultaneously intercepting the "seed-soil" crosstalk to normalize distant lung leading to regression of pre-existing PMN "soil". As a result, regional and metastatic recurrence were completely thwarted. Together, this framework synchronizing oncolysis immunization and inflammation alleviation provides an effective option for post-operative suppression of metastasis.

A liposome-based combination strategy using doxorubicin and a PI3K inhibitor efficiently inhibits pre-metastatic initiation by acting on both tumor cells and tumor-associated macrophages

Pre-metastatic initiation is essential in tumor metastasis, and the inhibition of it could prevent the spread of cancers to distant organs. Both tumor-associated macrophages (TAMs) and the epithelial-mesenchymal transition (EMT) play an important role in the pre-metastatic initiation stage. Herein, a liposome-based combination strategy which involves doxorubicin-loaded liposomes (Lip-Dox) and PI3K inhibitor-loaded liposomes (Lip-LY) was developed to simultaneously regulate tumor cells and TAMs for inhibiting pre-metastatic initiation. In tumor cells, Lip-LY sensitized cells to Lip-Dox treatment and inhibited the EMT process which was promoted by succinate, further mitigating succinate-induced migration and invasion of 4T1 cells. In TAMs, Lip-LY could efficiently inhibit the polarization of TAMs and reduce the percentage of M2 TAMs, so as to exhibit synergistic effects with Lip-Dox in TAM-induced metastasis. As a result, the combination treatment successfully reduced the lung metastasis of 4T1 bearing BALB/c mice by destroying metastatic tumor cells and inhibiting pre-metastatic initiation with decreased metastasis-associated protein expression. Overall, our work provided a simple and promising combination strategy for inhibiting pre-metastatic initiation in multiple ways to treat cancer metastasis.

Immunogenic hydrogel toolkit disturbing residual tumor “seeds” and pre-metastatic “soil” for inhibition of postoperative tumor recurrence and metastasis

Tumor recurrence and metastasis is the leading cause of mortality for postoperative breast cancer patients. However, chemotherapy intervention after surgery is often unsatisfactory, because residual microtumors are difficult to target and require frequent administration. Here, an all-in-one and once-for-all drug depot based on in situ-formed hydrogel was applied to fit the irregular surgical trauma, and enable direct contact with residual tumors and sustained drug release. Our immunological analysis after resection of orthotopic breast tumor revealed that postsurgical activation of CXCR4–CXCL12 signal exacerbated the immunosuppression and correlated with adaptive upregulation of PD-L1 in recurrent tumors. Thus, a multifunctional hydrogel toolkit was developed integrating strategies of CXCR4 inhibition, immunogenicity activation and PD-L1 blockade. Our results showed that the hydrogel toolkit not only exerted local effect on inhibiting residual tumor cell “seeds” but also resulted in abscopal effect on disturbing pre-metastatic “soil”. Furthermore, vaccine-like effect and durable antitumor memory were generated, which resisted a secondary tumor rechallenge in 100% cured mice. Strikingly, one single dose of such modality was able to eradicate recurrent tumors, completely prevent pulmonary metastasis and minimize off-target toxicity, thus providing an effective option for postoperative intervention.