Pre-metastatic niches: organ-specific homes for metastases

Fractionated radiotherapy initiated at the early stage of bone metastasis is effective to prolong survival in mouse model

BACKGROUND AND PURPOSE

Bone metastasis is common for breast cancer and associated with poor prognosis. Currently, radiotherapy (RT) serves as the standard treatment for patients exhibiting symptoms of bone metastasis to alleviate pain. Whether earlier application of RT will better control bone metastasis remains unclear.

METHODS

We utilized a mouse model of breast cancer bone metastasis by intra-femoral injection of 4T1-luc breast tumor cells. The bone metastasis was treated by RT using various doses, timings, and modalities. Tumor growth was assessed through bioluminescence imaging, and lung metastases was quantified following lung tissue fixation. Flow cytometry was employed to analyze alterations in immune cell populations.

RESULTS

Single high-dose RT suppressed tumor growth of bone metastases, but caused severe side effects. Conversely, fractionated RT mitigated tumor growth in bone metastases with fewer adverse effects. Fractioned RT initiated at the early stage of bone metastasis effectively inhibited tumor growth in the bone, suppressed secondary lung metastases, and prolonged mouse survival. In line with the known pro- and anti-metastatic effects of neutrophils and T cells in breast cancer, respectively, earlier fractioned RT consistently decreased the proportions of neutrophils while increased the proportions of T cells in both the bone and the lung tissues.

CONCLUSION

The data suggest that fractionated RT can inhibit the progression of early stage of bone metastasis and reduce secondary lung metastasis, leading to favorable outcomes. Therefore, these findings provide preclinical evidence to support the application of fractionated RT to treat patients with bone metastasis as earlier as possible.

APOC1 expressed in macrophages promotes the pulmonary metastasis of colorectal cancer via CCL2/CCL5

Metastasis is the main cause of death in colorectal cancer (CRC), and the lungs are common sites of metastasis. However, there is little effective target to intervene colorectal cancer pulmonary metastasis (CCPM), especially on its unique immune microenvironment. In this study, sixteen genes were identified as core CCPM-related differentially expressed genes (DEGs) between CRC and CCPM. Three genes including Apolipoprotein C1 (APOC1) were associated with prognosis, stage and metastasis of CRC. In immunohistochemistry, APOC1 was mainly expressed in macrophages, and expressed more in CCPM than CRC. Patients with synchronous CCPM, higher stage, poorer OS and CCPM-free interval tended to have higher expression. In experiments in vitro, knockdown of APOC1 in macrophages reduced the migration, invasion, and epithelial-mesenchymal transition of CRC cells. Knockdown of APOC1 in macrophages significantly decreased secretion of chemokines like CCL2 and CCL5. The pro-metastatic effect of macrophages expressing APOC1 was partially blocked by the antibodies of CCL2 and CCL5. Activation of STAT3 was a key process in APOC1's regulation of CCL2 and CCL5. In experiments in vivo, knockdown of APOC1 in macrophages reduced pulmonary metastasis. To conclude, APOC1 is one of core CCPM-related DEGs and associated with the metastasis and survival of CRC. Macrophages expressing APOC1 promote the CCPM by APOC1-STAT3-CCL2/CCL5 axis. APOC1 and macrophages expressing APOC1 play vital roles and may be potential therapeutic targets in CCPM.

The impact of a high fat diet and platelet activation on pre-metastatic niche formation

There is active crosstalk between tumor cells and the tumor microenvironment during metastatic progression, a process that is significantly affected by obesity, particularly in breast cancer. Here we analyze the impact of a high fat diet (HFD) on metastasis, focusing on the role of platelets in the formation of premetastatic niches (PMNs). We find that a HFD provokes pre-activation of platelets and endothelial cells, promoting the formation of PMNs in the lung. These niches are characterized by increased vascular leakiness, platelet activation and overexpression of fibronectin in both platelets and endothelial cells. A HFD promotes interactions between platelets, tumor cells and endothelial cells within PMNs, enhancing tumor cell homing and metastasis. Importantly, therapeutic interventions like anti-platelet antibody administration or a dietary switch reduce metastatic cell homing and outgrowth. Moreover, blocking fibronectin reduces the interaction of tumor cells with endothelial cells. Importantly, when coagulation parameters prior to neoadjuvant treatment are considered, triple negative breast cancer (TNBC) female patients with reduced Partial Thromboplastin time (aPTT) had a significantly shorter time to relapse. These findings highlight how diet and platelet activation in pre-metastatic niches affect tumor cell homing and metastasis, suggesting potential therapeutic interventions and prognostic markers for TNBC patients.

Recurrence patterns and prediction of survival after recurrence for gallbladder cancer

BACKGROUND

Gallbladder cancer (GBC) is associated with a poor prognosis. Recurrence patterns and their effect on survival remain ill-defined. This study aimed to analyze recurrence patterns and develop a machine learning (ML) model to predict survival after recurrence (SAR) of GBC.

METHODS

Patients who underwent curative-intent resection of GBC between 1999 and 2022 were identified using an international database. An Extreme Gradient Boosting ML model to predict SAR was developed and validated.

RESULTS

Among 348 patients, 110 (31.6%) developed disease recurrence during follow-up. The most common recurrence site was local (29.1%), followed by multiple site (26.4%), liver (21.8%), peritoneal (18.2%), and lung (0.05%). The median SAR was the longest in patients with lung recurrence (36.0 months), followed by those with local recurrence (15.7 months). In contrast, patients with peritoneal (8.9 months), liver (8.5 months), or multiple-site (6.4 months) recurrence had a considerably shorter SAR. Patients with multiple-site recurrence had a worse SAR than individuals with single-site recurrence (6.4 vs 11.10 months, respectively; P =.014). The model demonstrated good performance in the evaluation and bootstrapping cohorts (area under the receiver operating characteristic curve: 71.4 and 71.0, respectively). The most influential variables were American Society of Anesthesiologists classification, local recurrence, receipt of adjuvant chemotherapy, American Joint Committee on Cancer T and N categories, and developing early disease recurrence (<12 months). To enable clinical applicability, an easy-to-use calculator was made available (https://catalano-giovanni.shinyapps.io/SARGB).

CONCLUSION

Except for lung recurrence, SAR for GBC was poor. A subset of patients with less aggressive disease biology may have favorable SAR. ML-based SAR prediction may help individuate candidates for curative re-resection when feasible.

Bone mineral density affects tumor growth by shaping microenvironmental heterogeneity

Breast cancer bone metastasis is a major cause of mortality in patients with advanced breast cancer. Although decreased mineral density is a known risk factor for bone metastasis, the underlying mechanisms remain poorly understood because studying the isolated effect of bone mineral density on tumor heterogeneity is challenging with conventional approaches. Moreover, mineralized biomaterials are commonly utilized for clinical bone defect repair, but how mineralized biomaterials affect the foreign body response and wound healing is unclear. Here, we investigate how bone mineral affects tumor growth and microenvironmental complexity in vivo by combining single-cell RNA-sequencing with mineral-containing or mineral-free decellularized bone matrices. We discover that the absence of bone mineral significantly influences fibroblast and immune cell heterogeneity, promoting phenotypes that increase tumor growth and alter the response to injury or disease. Importantly, we observe that the stromal response to bone mineral content depends on the murine tumor model used. While lack of bone mineral induces tumor-promoting microenvironments in both immunocompromised and immunocompetent animals, these changes are mediated by altered fibroblast phenotype in immunocompromised mice and macrophage polarization in immunocompetent mice. Collectively, our findings suggest that bone mineral density affects tumor growth by impacting microenvironmental complexity in an organism-dependent manner.

Myeloid cells are involved in tumor immunity, metastasis and metabolism in tumor microenvironment

Bone marrow-derived cells in the tumor microenvironment, including macrophages, neutrophils, dendritic cells, myeloid-derived suppressor cells, eosinophils and basophils, participate in the generation, development, invasion and metastasis of tumors by producing different cytokines and interacting with other cell types, and play a pro-tumor or anti-tumor role in regulating tumor immunity. Due to the complexity of cell types in the tumor microenvironment and the unknown process of tumor development and metastasis, cancer treatment to achieve better survival status remains challenging. In this article, we summarize the effects of myeloid cells in tumor microenvironment on tumor immunity, cancer migration, and crosstalk with metabolism (including glucose metabolism, lipid metabolism, and amino acid metabolism), which will help to further study the tumor microenvironment and seek targeted therapeutic strategies for patients.

p62 sorts Lupus La and selected microRNAs into breast cancer-derived exosomes

Exosomes are multivesicular body-derived extracellular vesicles that are secreted by metazoan cells. Exosomes have utility as disease biomarkers, and exosome-mediated miRNA secretion has been proposed to facilitate tumor growth and metastasis. Previously, we demonstrated that the Lupus La protein (La) mediates the selective incorporation of miR-122 into metastatic breast cancer-derived exosomes; however, the mechanism by which La itself is sorted into exosomes remains unknown. Using unbiased proximity labeling proteomics, biochemical fractionation, superresolution microscopy and genetic tools, we establish that the selective autophagy receptor p62 sorts La and miR-122 into exosomes. We then performed small RNA sequencing and found that p62 depletion reduces the exosomal secretion of tumor suppressor miRNAs and results in their accumulation within cells. Our data indicate that p62 is a quality control factor that modulates the miRNA composition of exosomes. Cancer cells may exploit p62-dependent exosome cargo sorting to eliminate tumor suppressor miRNAs and thus to promote cell proliferation.

Extracellular vesicles from the lung pro-thrombotic niche drive cancer-associated thrombosis and metastasis via integrin beta 2

Cancer is a systemic disease with complications beyond the primary tumor site. Among them, thrombosis is the second leading cause of death in patients with certain cancers (e.g., pancreatic ductal adenocarcinoma [PDAC]) and advanced-stage disease. Here, we demonstrate that pro-thrombotic small extracellular vesicles (sEVs) are secreted by C-X-C motif chemokine 13 (CXCL13)-reprogrammed interstitial macrophages in the non-metastatic lung microenvironment of multiple cancers, a niche that we define as the pro-thrombotic niche (PTN). These sEVs package clustered integrin β2 that dimerizes with integrin αX and interacts with platelet-bound glycoprotein (GP)Ib to induce platelet aggregation. Blocking integrin β2 decreases both sEV-induced thrombosis and lung metastasis. Importantly, sEV-β2 levels are elevated in the plasma of PDAC patients prior to thrombotic events compared with patients with no history of thrombosis. We show that lung PTN establishment is a systemic consequence of cancer progression and identify sEV-β2 as a prognostic biomarker of thrombosis risk as well as a target to prevent thrombosis and metastasis.

A Novel Systemic siDR6 Delivery System Based on DP7-C for the Treatment of Metastatic Lung Cancer

Background

The treatment of metastatic lung cancer, a common complication of many primary cancers, has historically been a significant clinical challenge. Once lung metastasis occurs, patients' survival is often significantly shortened. Therefore, prevention and treatment of lung metastases is an important aspect of cancer treatment. In this study, a simple, low-toxicity, cholesterol-modified cationic cell-penetrating peptide DP7 (DP7-C), in combination with siDR6 was used for intravenous administration for the treatment of lung metastases.

Methods

Initially, clinical databases were analyzed to determine the expression levels of death receptor 6 (DR6) in metastatic tumors and the correlation between DR6 expression and patient survival times. The DP7-C/siDR6 micelles were prepared by a self-assembly method. By cultivating 293T, B16F10 and LL2 cells, the in vitro experiments were performed to assess the transfection efficiency, safety and anti-cancer ability of DP7-C/siDR6, while its targeting efficiency and prevention of lungs were investigated by mouse experiments. Furthermore, the therapeutic efficacy of DP7-C/siDR6 was demonstrated in the LL2 model of lung cancer in situ, the B16F10 model of artificial lung metastasis, and the 4T1 model of spontaneous lung metastasis.

Results

The clinical data analysis revealed that DR6 was highly expressed in the majority of metastatic tumors and that patients with high DR6 expression exhibited significantly shorter survival times. The DP7-C/siDR6 showed high transfection efficiency, and it could inhibit tumor cell growth by suppressing the STAT3 signaling pathway. Subsequent mouse experiments demonstrated that intravenous administration of DP7-C/siDR6 resulted in efficient lung targeting. The inhibition of DR6 expression on lung endothelial cells was found to prevent metastasis-induced primary necrosis of lung endothelial cells, thereby preventing tumor metastasis. And the DP7-C/siDR6 treatment showed excellent therapeutic efficacy in the tumor models.

Conclusion

The systemic delivery of DP7-C micelles carrying siDR6 provide an alternative therapeutic strategy to halt cancer lung metastasis.

The Pre-metastatic Niche: How Cancer Stem Cell-Derived Exosomal MicroRNA Fit into the Puzzle

Cancer metastasis is a complicated biological process that critically affects cancer progression, patient outcomes, and treatment plans. A significant step in metastasis is the formation of a pre-metastatic niche (PMN). A small subset of cells within tumors, known as cancer stem cells (CSCs), possess unique characteristics including, differentiation into different cell types within the tumor, self-renewal, and resistance to conventional therapies, that enable them to initiate tumors and drive metastasis. PMN plays an important role in preparing secondary organs for the arrival and proliferation of CSCs, thereby facilitating metastasis. CSC-derived exosomes are crucial components in the complex interplay between CSCs and the tumor microenvironment. These exosomes function as transporters of various substances that can promote cancer progression, metastasis, and modulation of pre-metastatic environments by delivering microRNA (miRNA, miR) cargo. This review aims to illustrate how exosomal miRNAs (exo-miRs) secreted by CSCs can predispose PMN and promote angiogenesis and metastasis.

Exploring the role of gut microbiota in colorectal liver metastasis through the gut-liver axis

Colorectal liver metastasis (CRLM) represents a major therapeutic challenge in colorectal cancer (CRC), with complex interactions between the gut microbiota and the liver tumor microenvironment (TME) playing a crucial role in disease progression via the gut-liver axis. The gut barrier serves as a gatekeeper, regulating microbial translocation, which influences liver colonization and metastasis. Through the gut-liver axis, the microbiota actively shapes the TME, where specific microbial species and their metabolites exert dual roles in immune modulation. The immunologically "cold" nature of the liver, combined with the influence of the gut microbiota on liver immunity, complicates effective immunotherapy. However, microbiota-targeted interventions present promising strategies to enhance immunotherapy outcomes by modulating the gut-liver axis. Overall, this review highlights the emerging evidence on the role of the gut microbiota in CRLM and provides insights into the molecular mechanisms driving the dynamic interactions within the gut-liver axis.

Lymphatic system is the mainstream for breast cancer dissemination and metastasis revealed by single-cell lineage tracing

Cancer metastasis is the primary cause of cancer-related death, yet the forces that drive cancer cells through various steps and different routes to distinct target organs/tissues remain elusive. In this study, we applied a barcoding system based single-cell lineage tracing approach to study the metastasis rate and route of breast cancer cells and their interactions with the tumor microenvironment (TME) during metastasis. The results indicate that only a small fraction of cells, accounting for fewer than 3% of total barcodes, can intravasate from the primary site into the blood circulation, whereas more cells disseminate through the lymphatic system to different organs. Tumor cells derived from the same progenitor cell exhibit different gene expression patterns in different soils, and the cancer cell-TME communication paradigm varies significantly between primary and metastatic tumors. Furthermore, metastable cells require a prewired particular cytokine expression ability which may be specific for lymph metastasis route although the underlying mechanism requires further investigation. In summary, leveraging a single-cell lineage tracing system, we demonstrate that the crosstalk between tumor cells and the TME is the driving force controlling the preferential metastatic fate of cancer cells through the lymphatic system.

Extraction of a stromal metastatic gene signature in breast cancer via spatial profiling

BACKGROUND

The identification of molecular features characterizing metastatic disease is a critical area of oncology research, as metastatic foci often exhibit distinct biological behaviors compared to primary tumors. While the focus has largely been on the neoplastic cells themselves, the characterization of the associated stroma remains largely underexplored, with significant implications for understanding metastasis.

MAIN BODY

By employing spatially resolved transcriptomics, we analyzed the transcriptional features of primary breast adenocarcinoma and its associated metastatic foci, on a representative set of microregions. We identified a stromal metastatic (Met) signature, which was subsequently validated across transcriptomic reference human breast cancer (BC) datasets and in spatial transcriptomics of a murine model.

CONCLUSION

We discuss the potential of a stromal Met signature to pinpoint metastatic breast cancer, serving as a prognostic tool that can provide a foundation for the exploration of tumor-extrinsic molecular hallmarks of BC metastatic foci.

The vascular microenvironment and its stem cells regulate vascular homeostasis

The vascular microenvironment comprises of anatomical structures, extracellular matrix components, and various cell populations, which play a crucial role in regulating vascular homeostasis and influencing vascular structure and function. Under physiological conditions, intrinsic regulation of the vascular microenvironment is required to sustain vascular homeostasis. In contrast, under pathological conditions, alterations to this microenvironment lead to vascular injury and pathological remodeling. According to the anatomy, the vascular microenvironment can be subdivided into three sections from the inside out. The vascular endothelial microenvironment, centered on vascular endothelial cells (VECs), includes the extracellular matrix and various vascular physicochemical factors. The VECs interact with vascular physicochemical factors to regulate the function of various parenchymal cells, including hepatocytes, neurons and tumor cells. The vascular wall microenvironment, comprising the vasa vasorum and their unique stem/progenitor cell niches, plays a pivotal role in vascular inflammation and pathological remodeling. Additionally, the perivascular microenvironment, which includes perivascular adipose tissue, consists of adipocytes and stem cells, which contribute to the pathological processes of atherosclerosis. It is anticipated that targeted regulation of the vascular microenvironment will emerge as a novel approach for the treatment of various diseases. Accordingly, this review will examine the structure of the vascular microenvironment, the regulation of vascular function by vascular cells and stem/progenitor cells, and the role of the vascular microenvironment in regulating cardiovascular diseases.

Fibrinogen: A new player and target on the formation of pre-metastatic niche in tumor metastasis

Tumor metastasis involves a series of complex and coordinated processes, which is the main cause of patient death and still a significant challenge in cancer treatment. Pre-metastatic niches (PMN), a specialized microenvironment that develops in distant organs prior to the arrival of metastatic cancer cells, plays a crucial role in driving tumor metastasis. The development of PMN depends on a complex series of cellular and molecular components including tumor-derived factors, bone marrow-derived cells, resident immune cells, and extracellular matrix. Fibrinogen, a key factor in the typical blood clotting process, is related to tumor metastasis and prognosis, according to a growing body of evidence in recent years. Fibrinogen has emerged as an important factor in mediating the formation of tumor microenvironment. Nevertheless, a clear and detailed mechanism by which fibrinogen promotes tumor metastasis remains unknown. In this review, we first explore the roles of fibrinogen in the development of PMN from four perspectives: immunosuppression, inflammation, angiogenesis, and extracellular matrix remodeling. We highlight the significance of fibrinogen in shaping PMN and discuss its potential therapeutic values, opening new avenues for targeting fibrinogen to prevent or treat metastasis.

Breast cancer stem cell-derived exosomal lnc-PDGFD induces fibroblast-niche formation and promotes lung metastasis

Triple-negative breast cancer (TNBC) is the most aggressive subtype with high metastatic potential and lack of therapeutic targets. Breast cancer stem cells (BCSCs) are enriched in TNBC and contribute to its metastatic propensity. Accumulating evidence suggests that cancer-derived exosomes are key drivers of premetastatic niche formation in distal organs. However, the function and underlying mechanism of BCSC-derived exosomes in TNBC metastasis remain elusive. Here, we demonstrated that BCSC-derived exosomes exhibit a greater capacity to activate fibroblasts and promote TNBC cell metastasis to the lung than non-BCSC-derived exosomes. Additionally, we found that upregulation of exosomal long non-coding RNA platelet derived growth factor D (lnc-PDGFD) expression in BCSCs is responsible for fibroblast activation through YBX1/NF-kB signaling in the lung. Activated fibroblasts further promote tumor progression by secreting IL-11. Taken together, BCSC-derived exosomes enriched with lnc-PDGFD could activate fibroblasts, thereby facilitating lung metastasis in TNBC patients. These results provide new insights into the mechanism of TNBC metastasis to the lung.

Adapt and shape: metabolic features within the metastatic niche

The success of disseminating cancer cells (DTCs) at specific metastatic sites is influenced by several metabolic factors. Even before DTCs arrival, metabolic conditioning from the primary tumor participates in creating a favorable premetastatic niche at distant organs. In addition, DTCs adjust their metabolism to better survive along the metastatic journey and successfully colonize their ultimate destination. However, the idea that the environment of the target organs may metabolically impact the metastatic fate is often underestimated. Here, we review the coexistence of two distinct strategies by which cancer cells shape and/or adapt to the metabolic profile of colonized tissues, ultimately creating a proper soil for their seeding and proliferation.

Regulation of metastatic organotropism

Metastasis is responsible for most cancer-related deaths. Different cancers have their own preferential sites of metastases, a phenomenon termed metastatic organotropism. The mechanisms underlying organotropism are multifactorial and include the generation of a pre-metastatic niche (PMN), metastatic homing, colonization, dormancy, and metastatic outgrowth. Historically, studies of metastatic organotropism have been limited by a lack of models allowing direct comparison of cells exhibiting different patterns of tropism. However, new innovative models and large-scale sequencing efforts have propelled organotropism research. Herein, we summarize the recent discoveries in metastatic organotropism regulation, focusing on lung, liver, brain, and bone tropism. We discuss how emerging technologies are continuing to improve our ability to model and, hopefully, predict and treat organotropism.

Synthetic short mRNA prevents metastasis via innate-adaptive immunity

Although most cancer deaths are caused by metastasis, there are no effective therapeutic approaches. This study describes the efficacy of a short synthetic mRNA (s-mRNA) designed by the sequence of non-vesicular extracellular IL1β-mRNA found in the pre-metastatic lung of tumor-bearing mice. The administration of s-mRNA inhibits murine lung metastasis by inducing the innate and adaptive immune systems. s-mRNA binds to ZC3H12D, an RNA-binding protein on natural killer cells and cytotoxic T lymphocytes. The ZC3H12D-s-mRNA complex translocated to the nucleus without being involved in translation. This process induces cytolytic activity and cell death in cancer cells without inducing a cytokine storm, and immune cells retain their antitumor activity. Although the antitumor activity of cytotoxic lymphocytes declines as the disease progresses in cancer patients, s-mRNA induces sustained high killing capacities of natural killer cells and cytotoxic T lymphocytes from colon cancer patients. Therefore, s-mRNA could be a breakthrough solution to prevent metastasis.

Emerging roles of intratumoral microbiota: a key to novel cancer therapies

Microorganisms, including bacteria, viruses, and fungi, have been found to play critical roles in tumor microenvironments. Due to their low biomass and other obstacles, the presence of intratumor microbes has been challenging to definitively establish. However, advances in biotechnology have enabled researchers to reveal the association between intratumor microbiota and cancer. Recent studies have shown that tumor tissues, once thought to be sterile, actually contain various microorganisms. Disrupted mucosal barriers and adjacent normal tissues are important sources of intratumor microbiota. Additionally, microbes can invade tumors by traveling through the bloodstream to the tumor site and infiltrating through damaged blood vessels. These intratumor microbiota may promote the initiation and progression of cancers by inducing genomic instability and mutations, affecting epigenetic modifications, activating oncogenic pathways, and promoting inflammatory responses. This review summarizes the latest advancements in this field, including techniques and methods for identifying and culturing intratumor microbiota, their potential sources, functions, and roles in the efficacy of immunotherapy. It explores the relationship between gut microbiota and intratumor microbiota in cancer patients, and whether altering gut microbiota might influence the characteristics of intratumor microbiota and the host immune microenvironment. Additionally, the review discusses the prospects and limitations of utilizing intratumor microbiota in antitumor immunotherapy.

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.

Endothelial calcium firing mediates the extravasation of metastatic tumor cells

Metastatic dissemination is driven by genetic, biochemical, and biophysical cues that favor the distant colonization of organs and the formation of life-threatening secondary tumors. We have previously demonstrated that endothelial cells (ECs) actively remodel during extravasation by enwrapping arrested tumor cells (TCs) and extruding them from the vascular lumen while maintaining perfusion. In this work, we dissect the cellular and molecular mechanisms driving endothelial remodeling. Using high-resolution intravital imaging in zebrafish embryos, we demonstrate that the actomyosin network of ECs controls tissue remodeling and subsequent TC extravasation. Furthermore, we uncovered that this cytoskeletal remodeling is driven by altered endothelial-calcium (Ca2+) signaling caused by arrested TCs. Accordingly, we demonstrated that the inhibition of voltage-dependent calcium L-type channels impairs extravasation. Lastly, we identified P2X4, TRP, and Piezo1 mechano-gated Ca2+ channels as key mediators of the process. These results further highlight the central role of endothelial remodeling during the extravasation of TCs and open avenues for successful therapeutic targeting.

Analysing the relevance of TGF-β and its regulators in cervical cancer to identify therapeutic and diagnostic markers

The role of transforming growth factor-beta (TGF-β) is dual, such that, it inhibits tumor development in initial stage and promotes metastasis in later stage. The present study is aimed to analyse the relevance of different types of TGF-β and their receptors on the overall survival (OS) and TGF-β driven gene expression in individuals with cervical cancer (CC) using ONCODB and GEPIA databases. The in-silico gene expression analysis showed, TGF-β1 and TGFβR2 are upregulated in cells infected with human papilloma virus (HPV)16, whereas, TGF-β2, TGFβR1 and TGFβR3 expression were downregulated. In HPV 18 infected cells, TGF-β1, TGF-β2 and TGFβR1 were downregulated, meanwhile, TGF-β3, TGFβR2 and TGFβR3 were upregulated. OS analysis of CC patients with different TGF-β expression revealed that, TGF-β1, TGF-β2, TGF-β3 and TGFβR2 were associated with reduced survival rate. Further, we identified four microRNAs (miRNAs) (hsa-miR-21-5p, hsa-miR-29b-3p, hsa-miR-101-3p and hsa-miR-130a-3p) interacted favorably with TGF-β in HPV 16 and 18 positive samples using MIENTURNET. This present review further emphasizes that, targeting TGF-β could be a novel and futuristic approach for CC management and therapeutics.

N, Huang J, Li Y, Zhao G, Liu M. Exosome tropism and various pathways in lung cancer metastasis

Lung cancer, characterized by its high morbidity and mortality rates, has the capability to metastasize to various organs, thereby amplifying its detrimental impact and fatality. The metastasis of lung cancer is a complex biological phenomenon involving numerous physiological transformations. Exosomes, small membranous vesicles enriched with biologically active components, are pivotal in mediating intercellular communication and regulating physiological functions due to their specificity and stability. Extensive research has elucidated the production and functions of exosomes in cancer contexts. Multitude of evidence demonstrates a strong association between lung cancer metastasis and exosomes. Additionally, the concept of the pre-metastatic niche is crucial in the metastatic process facilitated by exosomes. This review emphasizes the role of exosomes in mediating lung cancer metastasis and their impact on the disease's development and the progression to other tissues. Furthermore, it explores the potential of exosomes as biomarkers for lung cancer metastasis, offering significant insights for future clinical advancements.

Development of a phenotypic screening assay to measure activation of cancer-associated fibroblasts

Background

In cancer metastasis, tumor cells condition distant tissues to create a supportive environment, or metastatic niche, by driving the activation of cancer-associated fibroblasts (CAFs). These CAFs remodel the extracellular matrix, creating a microenvironment that supports tumor growth and compromises immune cell function, enabling cancer cells to evade immune detection. Consequently, targeting the activation of CAFs has been proposed as a therapeutic strategy to hinder metastatic spread. Our objective was to develop the first in vitro phenotypic screening assay capable of assessing this activation process.

Methods

Human primary lung fibroblasts were co-cultured with highly invasive breast cancer cells (MDA-MB-231) to identify changes in the expression of selected genes using RT-qPCR. An In-Cell ELISA (ICE)-based assay using human lung fibroblasts, MDA-MB-231 cells and human monocytes (THP-1 cells) was developed to measure the activation of CAFs. Another ELISA assay was used to measure released osteopontin.

Results

When lung fibroblast were co-cultured with MDA-MB-231 cells, among the 10 selected genes, the genes for osteopontin (SPP1), insulin like growth factor 1 (IGF1), periostin (POSTN) and α-smooth muscle actin (α-SMA, ACTA2) elicited the greatest fold change (55-, 37-, 8- and 5-fold respectively). Since osteopontin, IGF-1 and periostin are secreted proteins and α-SMA is an intracellular cytoskeleton protein, α-SMA was chosen to be the readout biomarker for the ICE assay. When fibroblasts were co-cultured with MDA-MB-231 cells and monocytes in the 96 well ICE assay, α-SMA expression was increased 2.3-fold yielding a robust Z' of 0.56. A secondary, low throughput assay was developed by measuring the release of osteopontin which showed a 6-fold increase when fibroblasts were co-cultured with MDA-MB-231 cells and monocytes.

Discussion

This phenotypic assay is the first to measure the activation of CAFs in a 96-well format, making it suitable for medium-to high-throughput screening of potential therapeutic compounds. By focusing on observable cellular phenotypic changes rather than targeting specific molecular pathways, this assay allows for a broader and unbiased identification of compounds capable of modulating CAF activation.

Mechanical signatures in cancer metastasis

The cancer metastatic cascade includes a series of mechanical barrier-crossing events, involving the physical movement of cancer cells from their primary location to a distant organ. This review describes the physical changes that influence tumour proliferation, progression, and metastasis. We identify potential mechanical signatures at every step of the metastatic cascade and discuss some latest mechanobiology-based therapeutic interventions to highlight the importance of interdisciplinary approaches in cancer diagnosis and treatment.

Recent Advances in Microfluidics for Nucleic Acid Analysis of Small Extracellular Vesicles in Cancer

Small extracellular vesicles (sEVs) are membranous vesicles released from cellular structures through plasma membrane budding. These vesicles contain cellular components such as proteins, lipids, mRNAs, microRNAs, long-noncoding RNA, circular RNA, and double-stranded DNA, originating from the cells they are shed from. Ranging in size from ≈25 to 300 nm and play critical roles in facilitating cell-to-cell communication by transporting signaling molecules. The discovery of sEVs in bodily fluids and their involvement in intercellular communication has revolutionized the fields of diagnosis, prognosis, and treatment, particularly in diseases like cancer. Conventional methods for isolating and analyzing sEVs, particularly their nucleic acid content face challenges including high costs, low purity, time-consuming processes, limited standardization, and inconsistent yield. The development of microfluidic devices, enables improved precision in sorting, isolating, and molecular-level separation using small sample volumes, and offers significant potential for the enhanced detection and monitoring of sEVs associated with cancer. These advanced techniques hold great promise for creating next-generation diagnostic and prognostic tools given their possibility of being cost-effective, simple to operate, etc. This comprehensive review explores the current state of research on microfluidic devices for the detection of sEV-derived nucleic acids as biomarkers and their translation into practical point-of-care and clinical applications.

Basement membranes in lung metastasis growth and progression

The lung is a highly vascularized tissue that often harbors metastases from various extrathoracic malignancies. Lung parenchyma consists of a complex network of alveolar epithelial cells and microvessels, structured within an architecture defined by basement membranes. Consequently, understanding the role of the extracellular matrix (ECM) in the growth of lung metastases is essential to uncover the biology of this pathology and developing targeted therapies. These basement membranes play a critical role in the progression of lung metastases, influencing multiple stages of the metastatic cascade, from the acquisition of an aggressive phenotype to intravasation, extravasation and colonization of secondary sites. This review examines the biological composition of basement membranes, focusing on their core components-collagens, fibronectin, and laminin-and their specific roles in cancer progression. Additionally, we discuss the function of integrins as primary mediators of cell adhesion and signaling between tumor cells, basement membranes and the extracellular matrix, as well as their implications for metastatic growth in the lung. We also explore vascular co-option (VCO) as a form of tumor growth resistance linked to basement membranes and tumor vasculature. Finally, the review covers current clinical therapies targeting tumor adhesion, extracellular matrix remodeling, and vascular development, aiming to improve the precision and effectiveness of treatments against lung metastases.

S100A8 as a potential therapeutic target for cancer metastasis

Metastasis is a major cause of cancer-related deaths. Similar to the tumor microenvironment formation, the premetastatic niche develops in distant organs before the arrival of tumor cells. Elucidating the mechanism(s) underlying premetastatic niche formation could contribute to the establishment of effective therapeutic targets for metastasis. Our research indicates that primary tumors hijack Toll-like receptor 4 (TLR4) signaling to establish a premetastatic niche in the lungs by utilizing an endogenous ligand S100A8. S100A8 is expressed not only in immune cells but also in various types of tumor cells. By focusing on S100A8 as a therapeutic target, we identified at least three multivalent S100A8 inhibitory peptides. Here, we review the tumor-promoting role of S100A8-mediated TLR4 signaling and propose S100A8 as a potential therapeutic target for aggressive cancer.

Radiomics analysis of thoracic vertebral bone marrow microenvironment changes before bone metastasis of breast cancer based on chest CT

Bone metastasis from breast cancer significantly elevates patient morbidity and mortality, making early detection crucial for improving outcomes. This study utilizes radiomics to analyze changes in the thoracic vertebral bone marrow microenvironment from chest computerized tomography (CT) images prior to bone metastasis in breast cancer, and constructs a model to predict metastasis.

METHODS

This study retrospectively gathered data from breast cancer patients who were diagnosed and continuously monitored for five years from January 2013 to September 2023. Radiomic features were extracted from the bone marrow of thoracic vertebrae on non-contrast chest CT scans. Multiple machine learning algorithms were utilized to construct various radiomics models for predicting the risk of bone metastasis, and the model with optimal performance was integrated with clinical features to develop a nomogram. The effectiveness of this combined model was assessed through receiver operating characteristic (ROC) analysis as well as decision curve analysis (DCA).

RESULTS

The study included a total of 106 patients diagnosed with breast cancer, among whom 37 developed bone metastases within five years. The radiomics model's area under the curve (AUC) for the test set, calculated using logistic regression, is 0.929, demonstrating superior predictive performance compared to alternative machine learning models. Furthermore, DCA demonstrated the potential of radiomics models in clinical application, with a greater clinical benefit in predicting bone metastasis than clinical model and nomogram.

CONCLUSION

CT-based radiomics can capture subtle changes in the thoracic vertebral bone marrow before breast cancer bone metastasis, offering a predictive tool for early detection of bone metastasis in breast cancer.

Aspartate signalling drives lung metastasis via alternative translation

Lung metastases occur in up to 54% of patients with metastatic tumours1,2. Contributing factors to this high frequency include the physical properties of the pulmonary system and a less oxidative environment that may favour the survival of cancer cells3. Moreover, secreted factors from primary tumours alter immune cells and the extracellular matrix of the lung, creating a permissive pre-metastatic environment primed for the arriving cancer cells4,5. Nutrients are also primed during pre-metastatic niche formation6. Yet, whether and how nutrients available in organs in which tumours metastasize confer cancer cells with aggressive traits is mostly undefined. Here we found that pulmonary aspartate triggers a cellular signalling cascade in disseminated cancer cells, resulting in a translational programme that boosts aggressiveness of lung metastases. Specifically, we observe that patients and mice with breast cancer have high concentrations of aspartate in their lung interstitial fluid. This extracellular aspartate activates the ionotropic N-methyl-D-aspartate receptor in cancer cells, which promotes CREB-dependent expression of deoxyhypusine hydroxylase (DOHH). DOHH is essential for hypusination, a post-translational modification that is required for the activity of the non-classical translation initiation factor eIF5A. In turn, a translational programme with TGFβ signalling as a central hub promotes collagen synthesis in lung-disseminated breast cancer cells. We detected key proteins of this mechanism in lung metastases from patients with breast cancer. In summary, we found that aspartate, a classical biosynthesis metabolite, functions in the lung environment as an extracellular signalling molecule to promote aggressiveness of metastases.

Rbfox3 Promotes Transformation of MDSC-Like Tumor Cells to Shape Immunosuppressive Microenvironment

Myeloid-derived suppressor cells (MDSCs) within the tumor microenvironment (TME) contribute to the malignant progression of tumors by exerting immunosuppressive effects. Bacterial lipopolysaccharides (LPS) have been widely demonstrated in various types of solid tumors. LPS can promote the malignant progression of tumors, which mechanism has not yet been fully elucidated. In this study, a type of MDSC-like tumor cells (MLTCs) is found in tumor tissues induced by low-dose and long-term LPS stimulation. MLTCs can simultaneously express tumor cell and MDSCs markers. Similar to MDSCs, MLTCs can produce arginine, nitric oxide, and reactive oxygen species and inhibit the activity of NK and T cells to promote the formation of an immunosuppressive microenvironment. MLTCs can also promote tumor cell proliferation and vasculogenic mimicry formation. CRISPR-Cas9 activity screening studies identified RNA-binding Fox-1 homolog 3 (Rbfox3) as a critical protein for MLTCs formation after LPS treatment. Rbfox3 can transcriptionally regulate the expression of Ass1 in the form of phase-separated particles. Crocin can inhibit the generation of MLTCs by disrupting phase-separated particles of Rbfox3 and enhance the anti-tumor effects of immune checkpoint inhibitors (ICIs).

Exosomal signaling in cancer metastasis: Molecular insights and therapeutic opportunities

Exosomes are membrane-bound extracellular vesicles that play a role in exchanging biological products across membranes and serve as intermediaries in intercellular communication to maintain normal homeostasis. Numerous molecules, including lipids, proteins, and nucleic acids are enclosed in exosomes. Exosomes are constantly released into the extracellular environment and exhibit distinct characteristics based on the secreted cells that produce them. Exosome-mediated cell-to-cell communication has reportedly been shown to affect multiple cancer hallmarks, such as immune response modulation, pre-metastatic niche formation, angiogenesis, stromal cell reprogramming, extracellular matrix architecture remodeling, or even drug resistance, and eventually the development and metastasis of cancer cells. Exosomes can be used as therapeutic targets and possible diagnostic biomarkers by selectively loading oncogenic molecules into them. We highlight the important roles that exosomes play in cancer development in this review, which may lead to the development of fresh approaches for future clinical uses.

Leptomeningeal metastatic disease: new frontiers and future directions

Leptomeningeal metastatic disease (LMD), encompassing entities of 'meningeal carcinomatosis', neoplastic meningitis' and 'leukaemic/lymphomatous meningitis', arises secondary to the metastatic dissemination of cancer cells from extracranial and certain intracranial malignancies into the leptomeninges and cerebrospinal fluid. The clinical burden of LMD has been increasing secondary to more sensitive diagnostics, aggressive local therapies for discrete brain metastases, and improved management of extracranial disease with targeted and immunotherapeutic agents, resulting in improved survival. However, owing to drug delivery challenges and the unique microenvironment of LMD, novel therapies against systemic disease have not yet translated into improved outcomes for these patients. Underdiagnosis and misdiagnosis are common, response assessment remains challenging, and the prognosis associated with this disease of whole neuroaxis remains extremely poor. The dearth of effective therapies is further challenged by the difficulties in studying this dynamic disease state. In this Review, a multidisciplinary group of experts describe the emerging evidence and areas of active investigation in LMD and provide directed recommendations for future research. Drawing upon paradigm-changing advances in mechanistic science, computational approaches, and trial design, the authors discuss domain-specific and cross-disciplinary strategies for optimizing the clinical and translational research landscape for LMD. Advances in diagnostics, multi-agent intrathecal therapies, cell-based therapies, immunotherapies, proton craniospinal irradiation and ongoing clinical trials offer hope for improving outcomes for patients with LMD.

Exosomal Galectin-3 promotes peritoneal metastases in gastric adenocarcinoma via microenvironment alterations

Peritoneal carcinomatosis (PC) in gastric adenocarcinoma (GAC) is the most common metastatic site and leads to a short median survival. Exosomes have been shown to remodel the microenvironment, facilitating tumor metastases. However, the functional component in GAC cell-derived exosomes that remodel the landscape in the peritoneal cavity remains unclear. To address this, we performed in-depth proteomic profiling of ascites-derived exosomes from patients with PC, and we found that Galectin-3 was highly enriched in exosomes derived from malignant ascites. exosomal Galectin-3 was the crucial regulator of PC. Blockage of exosomal Galectin-3 significantly inhibited tumor metastases and prolonged overall survival. Exosomal Galectin-3 activated cancer-associated fibroblasts through integrin α1β1/FAK/Akt/mTOR/CXCL12 signaling. Combined inhibition of the CXCL12-CXCR4 axis and exosomal Galectin-3 enhanced the efficacy of anti-PD-1 immunotherapy, leading to significantly diminished PC progression and durable antitumor responses. These findings provide a rationale for clinical strategy of targeting exosomal Galectin-3 to treat PC.

Adaptations of neutrophils in cancer

There is a renewed interest in neutrophil biology, largely instigated by their prominence in cancer. From an immunologist's perspective, a conceptual breakthrough is the realization that prototypical inflammatory, cytotoxic leukocytes can be tamed to promote the survival and growth of other cells. This has sparked interest in defining the biological principles and molecular mechanisms driving the adaptation of neutrophils to cancer. Yet, many questions remain: is this adaptation mediated by reprogramming mature neutrophils inside the tumoral mass, or rather by rewiring granulopoiesis in the bone marrow? Why, in some instances, are neutrophils beneficial and in others detrimental to cancer? How many different functional programs can be induced in neutrophils by tumors, and is this dependent on the type of tumor? This review summarizes what we know about these questions and discusses therapeutic strategies based on our incipient knowledge of how neutrophils adapt to cancer.

Continued attention: The role of exosomal long non-coding RNAs in tumors over the past three years

This review summarizes the research on exosomal lncRNAs in tumors over the past three years. It highlights the significant roles of exosomal lncRNAs in modulating various cellular processes within the tumor microenvironment. Exosomal lncRNAs have been shown to influence the behavior of tumor cells, promoting proliferation, metastasis, epithelial-mesenchymal transition (EMT), angiogenesis, glycolysis, and contributing to tumor growth and metabolism. Moreover, exosomal lncRNAs have been found to interact with immune cells, such as modulating the functions of macrophages and influencing the overall immune response against tumors. Fibroblasts within the tumor microenvironment are also affected by exosomal lncRNAs, which can alter the extracellular matrix (ECM) and stromal composition. Notably, these exosomal lncRNAs hold promise in the diagnosis and treatment of tumors, offering potential biomarkers and therapeutic targets for improved clinical outcomes.

Distant Metastases of Breast Cancer Resemble Primary Tumors in Cancer Cell Composition but Differ in Immune Cell Phenotypes

Breast cancer is the most commonly diagnosed cancer in women, with distant metastasis being the main cause of breast cancer-related deaths. Elucidating the changes in the tumor and immune ecosystems that are associated with metastatic disease is essential to improve understanding and ultimately treatment of metastasis. Here, we developed an in-depth, spatially resolved single-cell atlas of the phenotypic diversity of tumor and immune cells in primary human breast tumors and matched distant metastases, using imaging mass cytometry to analyze a total of 75 unique antibody targets. Although the same tumor cell phenotypes were typically present in primary tumors and metastatic sites, suggesting a strong founder effect of the primary tumor, their proportions varied between matched samples. Notably, the metastatic site did not influence tumor phenotype composition, except for the brain. Metastatic sites exhibited a lower number of immune cells overall but had a higher proportion of myeloid cells as well as exhausted and cytotoxic T cells. Myeloid cells showed distinct tissue-specific compositional signatures and increased presence of potentially matrix remodeling phenotypes in metastatic sites. This analysis of tumor and immune cell phenotypic composition of metastatic breast cancer highlights the heterogeneity of the disease within patients and across distant metastatic sites, indicating myeloid cells as the predominant immune modulators that could potentially be targeted at these sites. Significance: Multiplex imaging analysis of matched primary and metastatic breast tumors provides a phenotypic and spatial map of tumor microenvironments, revealing similar compositions of cancer cells and divergent immunologic features between matched samples.

Immune Cell Profiling Reveals a Common Pattern in Premetastatic Niche Formation Across Various Cancer Types

BACKGROUND

Metastasis is the major cause of cancer-related mortality. The premetastatic niche is a promising target for its prevention. However, the generality and cellular dynamics in premetastatic niche formation have remained unclear.

AIMS

This study aimed to elucidate the generality and cellular dynamics in premetastatic niche formation.

MATERIALS AND METHODS

We performed comprehensive flow cytometric analysis of lung and peripheral immune cells at three time points (early premetastatic, late premetastatic, and micrometastatic phases) for mice with subcutaneous implants of three types of cancer cells (breast cancer, lung cancer, or melanoma cells). The immuno-cell profiles were then used to predict the metastatic phase by machine learning.

RESULTS

We found a common pattern of changes in both lung and peripheral immune cell profiles across the three cancer types, including a decrease in the proportion of eosinophils in the early premetastatic phase, an increase in that of regulatory T cells in the late premetastatic phase, and an increase in that of polymorphonuclear myeloid-derived suppressor cells and a decrease in that of B cells in the micrometastatic phase. Machine learning using immune cell profiles could predict the metastatic phase with approximately 75% accuracy.

DISCUSSION

Validation of our findings in humans will require data on the presence or absence of micrometastases in patients and the accumulation of comprehensive and temporal information on immune cells. In addition, blood proteins, extracellular vesicles, DNA, RNA, or metabolites may be useful for more accurate prediction.

CONCLUSION

The discovery of generalities in premetastatic niche formation allow prediction of metastatic phase and provide a basis for the development of methods for early detection and prevention of cancer metastasis in a cancer type-independent manner.

Immune Microenvironment in Breast Cancer Metastasis

Metastatic disease is the final stage of breast cancer that accounts for vast majority of patient death. Mounting data over recent years strongly support the critical roles of the immune microenvironment in determining breast cancer metastasis. The latest single-cell studies provide further molecular evidence illustrating the heterogeneity of this immune microenvironment. This chapter summarizes major discoveries on the role of various immune cells in metastasis progression and discusses future research opportunities. Studies investigating immune heterogeneity within primary breast cancer and across different metastasis target organs can potentially lead to more precise treatment strategies with improved efficacy.

[Myeloid-derived suppressor cells as important factors and potential targets for breast cancer progression]

Recurrence and metastasis remain the leading cause of death in breast cancer patients due to the lack of effective treatment. A microenvironment suitable for cancer cell growth, referred to as pre-metastatic niche (PMN), is formed in distant organs before metastasis occurs. Myeloid-derived suppressor cells (MDSCs) are a heterogenous population of immature myeloid cells with immunosuppressive effects. They can expand in large numbers in breast cancer patients and participate in the formation of PMN. MDSCs can remodel the extracellular matrix of pulmonary vascular endothelial cells and recruit cancer stem cells to promote the lung metastasis of breast cancer. Furthermore, MDSCs facilitate immune evasion of breast cancer cells to impact the efficacy of immunotherapy. It is proposed that MDSCs represent a potential therapeutic target for the inhibition of recurrence and metastasis in breast cancer. Therapeutic strategies targeting MDSCs have shown promising efficacy in preclinical studies and clinical trials. This review presents a summary of the principal factors involved in the recruitment and activation of MDSCs during the formation of PMN, and outlines MDSCs functions such as immunosuppression and the current targeted therapies against MDSCs, aiming to provide new ideas for the treatment of distant metastases in breast cancer.

Reprogramming tumor-associated macrophages with lipid nanosystems reduces PDAC tumor burden and liver metastasis

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) requires innovative therapeutic strategies to counteract its progression and metastatic potential. Since the majority of patients are diagnosed with advanced metastatic disease, treatment strategies targeting not only the primary tumor but also metastatic lesions are needed. Tumor-Associated Macrophages (TAMs) have emerged as central players, significantly influencing PDAC progression and metastasis. Our objective was to validate an innovative therapeutic strategy involving the reprogramming of TAMs using lipid nanosystems to prevent the formation of a pro-metastatic microenvironment in the liver.

RESULTS

In vitro results demonstrate that M2-polarized macrophages lose their M2-phenotype following treatment with lipid nanoemulsions composed of vitamin E and sphingomyelin (VitE:SM), transitioning to an M0/M1 state. Specifically, VitE:SM nanoemulsion treatment decreased the expression of macrophage M2 markers such as Arg1 and Egr2, while M1 markers such as Cd86, Il-1b and Il-12b increased. Additionally, the TGF-βR1 inhibitor Galunisertib (LY2157299) was loaded into VitE:SM nanoemulsions and delivered to C57BL/6 mice orthotopically injected with KPC PDAC tumor cells. Treated mice showed diminished primary tumor growth and reduced TAM infiltration in the liver. Moreover, we observed a decrease in liver metastasis with the nanoemulsion treatment in an intrasplenic model of PDAC liver metastasis. Finally, we validated the translatability of our VitE:SM nanosystem therapy in a human cell-based 3D co-culture model in vivo, underscoring the pivotal role of macrophages in the nanosystem's therapeutic effect in the context of human PDAC metastasis.

CONCLUSIONS

The demonstrated effectiveness and safety of our nanosystem therapy highlights a promising therapeutic approach for PDAC, showcasing its potential in reprogramming TAMs and mitigating the occurrence of liver metastasis.

Ovarian cancer-derived TGF-β1 induces cancer-associated adipocytes formation by activating SMAD3/TRIB3 pathway to establish pre-metastatic niche

Ovarian cancer (OC) is prone to adipose tissue metastasis. However, the underlying molecular mechanisms remain elusive. Here, we observed that omental adipocytes were induced into cancer-associated adipocytes (CAAs) by OC-derived TGF-β1 to establish a pre-metastatic niche (PMN) through collagen and fibronectin secretion. Mechanistically, OC-derived TGF-β1 binds to adipocyte membrane receptors and thus activates intracellular signaling by SMAD3 phosphorylation. The activation of TGF-β1/SMAD3 signaling pathway dedifferentiates adipocytes into CAAs by upregulating Tribbles homolog 3 (TRIB3), which suppresses the phosphorylation of CEBPβ. Additionally, CAAs secrete collagen I, collagen VI, and fibronectin to remodel the extracellular matrix and promote the adhesion of OC cells. Pharmacological inhibition of the TGF-β1/SMAD3 pathway significantly inhibits CAAs and PMN formation, thereby reducing the OC metastatic burden. Our findings indicate that the formation of CAAs and PMN in adipose tissues facilitates OC cell implantation and blocking the TGF-β1/SMAD3 signaling pathway could prevent OC omental metastasis.

Salivary adenoid cystic carcinoma-derived α2,6-sialylated extracellular vesicles increase vascular permeability by triggering ER-stress in endothelial cells and promote lung metastasis

Salivary adenoid cystic carcinoma (SACC) tends to metastasize to the lungs in the early stages of the disease. Factors secreted by the primary tumor can induce the formation of a supportive microenvironment in distant organs prior to metastasis, a process known as pre-metastatic niche (PMN) formation. Extracellular vesicles (EVs) participate in PMN formation. In this study, α2,6-sialylation of EVs derived from SACC cells with high metastatic potential increased vascular permeability, thereby facilitating tumor metastasis to the lungs. Mechanistic studies indicated that EV α2,6-sialylation triggers protein kinase R-like endoplasmic reticulum kinase (PERK)-eukaryotic initiation factor 2α (eIF2α)-dependent activation of endoplasmic reticulum (ER) stress in the endothelium, leading to the disruption of vascular endothelial cadherin membrane expression. Sialidase or an ER stress inhibitor rescued vascular permeability induced by SACC EVs, which decreased the number of SACC cells extravasating into the lungs both in vitro and in vivo. This study identified a critical role of α2,6-sialylation of SACC EVs in lung metastasis. The findings indicate that EV α2,6-sialylation-induced ER stress in endothelial cells might be a therapeutic target for preventing SACC lung metastasis.

Tumor-derived exosomes: Unravelling the pathogenesis of pancreatic cancer with liver metastases and exploring the potential for clinical translation

Pancreatic cancer (PC) is one of the most malignant solid cancers, and PC metastasis, particularly liver metastasis, is a major cause of cancer mortality. A key event in tumor metastasis is the formation of pre-metastatic niche (PMN), which provides a microenvironment conducive to tumor cells colonization and progression. Various molecules loaded in tumor-derived exosomes (TDEs) contribute to PMN formation and distant tumor metastasis, by regulating immune and stromal cell function, inducing angiogenesis, and promoting metabolic reprogramming. Therefore, therapies targeting PMN may offer novel advantages to prevent tumor metastasis at an earlier stage. In this review, we summarize multifaceted mechanisms underlying hepatic PMN formation, with a focus on how PC TDEs participate in angiogenesis and vascular permeability, create immune suppressive microenvironment, remodel the extracellular matrix, and regulate metabolic reprogramming. In addition, we highlight the promise of TDEs for early diagnosis and effective therapy of PC liver metastases.

Circulating tumor cells shed large extracellular vesicles in capillary bifurcations that activate endothelial and immune cells

Circulating tumor cells (CTCs) and their clusters are the drivers of metastasis, but we have an incomplete understanding of how they interact with capillary beds. Using microfluidic models mimicking human capillary bifurcations, we observed cell size- and bifurcation-dependent shedding of nuclei-free fragments by patient CTCs, CTC-derived explant cells and numerous cancer cell lines. Shedding reduced cell sizes up to 61%, facilitating their transit through bifurcations. We demonstrated that shed fragments were a novel subclass of large extracellular vesicles (LEVs), "shearosomes", that require shear stress for their biogenesis and whose proteome was associated with immune-related pathways. Shearosomes exhibited functions characteristic of previously identified EVs including cell-directed internalization by endothelial and immune cells, and intercellular communication abilities such as disruption of endothelial barrier integrity, polarization of monocytes into M2 tumor-promoting macrophages and interactions between endothelial and immune cells. Cumulatively, these findings suggest that CTCs shed shearosomes in capillary beds that drive key processes involved in the formation of pre-metastatic niches.

Macrophages promote pre-metastatic niche formation of breast cancer through aryl hydrocarbon receptor activity

Macrophages that acquire an immunosuppressive phenotype play a crucial role in establishing the pre-metastatic niche (PMN), which is essential for facilitating breast cancer metastasis to distant organs. Our study showed that increased activity of the aryl hydrocarbon receptor (AHR) in lung macrophages plays a crucial role in establishing the immunosuppressive PMN in breast cancer. Specifically, AHR activation led to high expression of PD-L1 on macrophages by directly binding to the promoter of Pdl1. This upregulation of PD-L1 promoted the differentiation of regulatory T cells (Tregs) within the PMN, further enhancing immunosuppressive conditions. Mice with Ahr conditional deletion in macrophages had reduced lung metastasis of breast cancer. The elevated AHR levels in PMN macrophages were induced by GM-CSF, which was secreted by breast cancer cells. Mechanistically, the activated STAT5 signaling pathway induced by GM-CSF prevented AHR from being ubiquitinated, thereby sustaining its activity in macrophages. In breast cancer patients, the expression of AHR and PD-L1 was correlated with increased Treg cell infiltration, and higher levels of AHR were associated with a poor prognosis. These findings reveal that the crosstalk of breast cancer cells, lung macrophages, and Treg cells via the GM-CSF-STAT5-AHR-PD-L1 cascade modulates the lung pre-metastatic niche during breast cancer progression.

Recent Advancements in Imaging Techniques for Individual Extracellular Vesicles

Extracellular vesicles (EVs), secreted from most cells, are small lipid membranes of vesicles of 30 to 1000 nm in diameter and contain nucleic acids, proteins, and intracellular organelles originating from donor cells. EVs play pivotal roles in intercellular communication, particularly in forming niches for cancer cell metastasis. However, EVs derived from donor cells exhibit significant heterogeneity, complicating the investigation of EV subtypes using ensemble averaging methods. In this context, we highlight recent studies that characterize individual EVs using advanced techniques, including single-fluorescent-particle tracking, single-metal-nanoparticle tracking, single-non-label-particle tracking, super-resolution microscopy, and atomic force microscopy. These techniques have facilitated high-throughput analyses of the properties of individual EV particles such as their sizes, compositions, and physical properties. Finally, we address the challenges that need to be resolved via single-particle (-molecule) imaging and super-resolution microscopy in future research.