Real-Time Imaging Reveals Local, Transient Vascular Permeability, and Tumor Cell Intravasation Stimulated by TIE2hi Macrophage-Derived VEGFA

Astragali Radix-Curcumae Rhizoma normalizes tumor blood vessels by HIF-1α to anti-tumor metastasis in colon cancer

BACKGROUND

Abnormal tumor blood vessels can significantly promote the malignant progression of tumors, prompting researchers to focus on drugs that normalize these vessels for clinical treatment. The combination of the Qi-tonifying drug Astragali Radix and the blood-activating drug Curcumae Rhizoma, referred to as AC, exhibited significant anti-tumor metastasis effects. However, the association between the anti-tumor metastasis effect of AC and its potential role in regulating tumor vascular remodeling warrants further exploration.

PURPOSE

This study aimed to elucidate the mechanism through which AC induces tumor blood vessel normalization in colon cancer (CC).

METHODS

The potential active components of AC were identified through UPLC-MS/MS. An orthotopic transplantation model of CC was established in BALB/c mice using the CT26-Lucifer cell line, and the effects of AC were evaluated using IVIS imaging, hematoxylin and eosin (H&E) staining, and immunohistochemistry. Network pharmacology and molecular biology analyses were employed to identify the potential direct targets of AC. Subsequently, RT-PCR and Western blotting techniques were utilized to validate the findings obtained from network pharmacology. Furthermore, ELISA and other methodologies were used to investigate glycolysis-related indicators, along with immunofluorescence technology to demonstrate changes in vascular leakage and perfusion characteristics associated with blood vessel normalization.

RESULTS

We identified HIF-1α as a potential direct target of AC. This interaction influences the glycolytic processes in both tumor cells and tumor-associated endothelial cells (TECs) by directly binding to HIF-1α and modulating its nuclear translocation, thereby determining the integrity of TEC junctions. Mechanistically, AC directly regulates the key enzyme PFKFB3 in glycolysis by modulating HIF-1α expression and inhibiting its nuclear translocation. This action reduces tumor glycolytic flux, decreases the internalization of VE-cad, and influences the expression of downstream matrix metalloproteinases (MMPs), thereby strengthening the adherens and tight junctions between TECs and restoring vascular integrity.

CONCLUSION

This study presents novel findings that AC can regulate glycolysis through the inhibition of HIF-1α nuclear translocation, thereby promoting the normalization of tumor blood vessels and effectively inhibiting tumor metastasis. These results suggested that AC may serve as an effective therapeutic agent for normalizing tumor blood vessels.

Targeting VEGF signaling for tumor microenvironment remodeling and metastasis inhibition: Therapeutic strategies and insights

The tumor microenvironment (TME) plays a pivotal role in cancer progression and metastasis, with vascular endothelial growth factor (VEGF) signaling serving as a key regulator of tumor angiogenesis and immune evasion. VEGF induces abnormal blood vessel formation, promoting tumor growth, immune suppression, and metastasis through epithelialmesenchymal transition (EMT). As a result, VEGF signaling has become a critical therapeutic target in cancer treatment. This review examines the molecular mechanisms driving VEGF-mediated tumor growth and angiogenesis, with a focus on the interaction between tumor and endothelial cells and the dual role of VEGF in fostering vascularization and immune suppression. Current anti-VEGF therapies, including monoclonal antibodies (e.g., bevacizumab) and tyrosine kinase inhibitors (TKIs), have demonstrated efficacy and have received FDA approval for various cancers; however, therapeutic resistance remains a significant challenge. Strategies to overcome resistance, such as novel VEGF inhibitors, vascular normalization approaches, and combination therapies with immune checkpoint inhibitors, have been explored. Additionally, future directions emphasize the need for personalized approaches to improve treatment efficacy and reduce metastasis. A comprehensive understanding of VEGF signaling in the TME may pave the way for more effective cancer therapies.

Microfabricated Organ-Specific Models of Tumor Microenvironments

Despite the advances in detection, diagnosis, and treatments, cancer remains a lethal disease, claiming the lives of more than 600,000 people in the United States alone in 2024. To accelerate the development of new therapeutic strategies with improved responses, significant efforts have been made to develop microfabricated in vitro models of tumor microenvironments (TMEs) that address the limitations of animal-based cancer models. These models incorporate several advanced tissue engineering techniques to better reflect the organ- and patient-specific TMEs. Additionally, microfabricated models integrated with next-generation single-cell omics technologies provide unprecedented insights into patient's cellular and molecular heterogeneity and complexity. This review provides an overview of the recent understanding of cancer development and outlines the key TME elements that can be captured in microfabricated models to enhance their physiological relevance. We highlight the recent advances in microfabricated cancer models that reflect the unique characteristics of their organs of origin or sites of dissemination.

Intravital Imaging of Immune Responses in the Cancer Microenvironment

BACKGROUND

To date, many types of immune cells have been identified, but their precise role in cancer immunity remains unclear. Understanding the immune responses involved in cancer and the cancer microenvironment is becoming increasingly important for elucidating disease mechanisms. In recent years, the application of intravital imaging in cancer research has provided new insights into the mechanisms of cancer-specific immune events, including innate and adaptive immunity.

RESULTS

In this review, we focus on the emerging role of intravital imaging in cancer research and describe how cancer and immune cells can be observed using intravital imaging in vivo. We also discuss new insights gained by this state-of-the-art technique.

CONCLUSIONS

Intravital imaging is a relatively new field of research that offers significant advantages, including the ability to directly capture cell-cell interactions, pathophysiology, and immune cell dynamics in the cancer microenvironment in vivo.

The origin and polarization of Macrophages and their role in the formation of the Pre-Metastatic niche in osteosarcoma

Osteosarcoma, a primary malignant bone tumor commonly found in adolescents, is highly aggressive, with a high rate of disability and mortality. It has a profound negative impact on both the physical and psychological well-being of patients. The standard treatment approach, comprising surgery and chemotherapy, has seen little improvement in patient outcomes over the past several decades. Once relapse or metastasis occurs, prognosis worsens significantly. Therefore, there is an urgent need to explore new therapeutic approaches. In recent years, the successful application of immunotherapy in certain cancers has demonstrated its potential in the field of cancer treatment. Macrophages are the predominant components of the immune microenvironment in osteosarcoma and represent critical targets for immunotherapy. Macrophages exhibit dual characteristics; while they play a key role in maintaining tumor-promoting properties within the microenvironment, such as inflammation, angiogenesis, and immune suppression, they also possess antitumor potential as part of the innate immune system. A deeper understanding of macrophages and their relationship with osteosarcoma is essential for the development of novel therapeutic strategies.

Focal adhesion in the tumour metastasis: from molecular mechanisms to therapeutic targets

The tumour microenvironment is the "hotbed" of tumour cells, providing abundant extracellular support for growth and metastasis. However, the tumour microenvironment is not static and is constantly remodelled by a variety of cellular components, including tumour cells, through mechanical, biological and chemical means to promote metastasis. Focal adhesion plays an important role in cell-extracellular matrix adhesion. An in-depth exploration of the role of focal adhesion in tumour metastasis, especially their contribution at the biomechanical level, is an important direction of current research. In this review, we first summarize the assembly of focal adhesions and explore their kinetics in tumour cells. Then, we describe in detail the role of focal adhesion in various stages of tumour metastasis, especially its key functions in cell migration, invasion, and matrix remodelling. Finally, we describe the anti-tumour strategies targeting focal adhesion and the current progress in the development of some inhibitors against focal adhesion proteins. In this paper, we summarize for the first time that focal adhesion play a positive feedback role in pro-tumour metastatic matrix remodelling by summarizing the five processes of focal adhesion assembly in a multidimensional way. It is beneficial for researchers to have a deeper understanding of the role of focal adhesion in the biological behaviour of tumour metastasis and the potential of focal adhesion as a therapeutic target, providing new ideas for the prevention and treatment of metastases.

Next-Generation Photosensitizers: Cyanine-Carborane Salts for Superior Photodynamic Therapy of Metastatic Cancer

Photodynamic therapy (PDT) has emerged as a promising targeted treatment for cancer. However, current PDT is limited by low tissue penetration, insufficient phototoxicity (toxicity with light irradiation), and undesirable cytotoxicity (toxicity without light irradiation). Here, we report the discovery of cyanine-carborane salts as potent photosensitizers (PSs) that harness the near-infrared (NIR) absorbing [cyanine+] with the inertness of [carborane-]. The implementation of [cyanine+] [carborane-] salts dramatically enhance cancer targeting of the PSs and decrease cytotoxicity. We characterize the cellular uptake of the cyanine-carborane PSs, organelle localization, generation of reactive oxygen species (ROS) with the ability to cogenerate multiple ROS species, suppression of pro-metastatic pathways, and activation of apoptotic pathways. We further demonstrate the ability of optimized PSs to eliminate tumors in vivo using an orthotopic mouse model of breast cancer. These newly developed [cyanine+] [carborane-] salt PSs introduce a potent therapeutic approach against aggressive breast cancer while decreasing side effects.

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.

Drug Treatment Direction Based on the Molecular Mechanism of Breast Cancer Brain Metastasis

Today, breast cancer (BC) is the most frequently diagnosed malignancy and a leading cause of cancer-related deaths among women worldwide. Brain metastases (BMs) are a common complication among individuals with advanced breast cancer, significantly impacting both survival rates and the overall condition of life of patients. This review systematically analyzes the innovative approaches to drug treatment for breast cancer brain metastases (BCBMs), with particular emphasis placed on treatments targeting molecular mechanisms and signaling pathways and drug delivery strategies targeting the blood brain barrier (BBB). The article discusses various drugs that have demonstrated effectiveness against BCBM, featuring a mix of monoclonal antibodies, nimble small-molecule tyrosine kinase inhibitors (TKIs), and innovative antibody-drug conjugates (ADCs). This study of various drugs and techniques designed to boost the permeability of the BBB sheds light on how these innovations can improve the treatment of brain metastases. This review highlights the need to develop new therapies for BCBM and to optimize existing treatment strategies. With a deeper comprehension of the intricate molecular mechanisms and advances in drug delivery technology, it is expected that more effective personalized treatment options will become available in the future for patients with BCBM.

The metastatic cascade through the lens of therapeutic inhibition

Metastasis is a main cause of cancer-related death, and a deeper understanding of the metastatic process will inform more targeted and mechanistic approaches that can abrogate challenges in treatment efficacy and toxicity. Several steps throughout the metastatic cascade, from angiogenesis to secondary tumor formation, offer specific vulnerabilities to therapies that can lead to the decline or cessation of metastatic progression. A deeper understanding of the metastatic cascade also allows combination systemic therapies to be used synergistically. In this review, we describe current treatment modalities in the context of multiple steps of the metastatic cascade. We highlight their mechanisms and present their efficacy across multiple cancers. This work also presents targets within the metastatic cascade in need of more research that can advance the landscape of treatments and lead to the goal of metastatic cancer remission.

The Role of Macrophages in Various Types of Tumors and the Possibility of Their Use as Targets for Antitumor Therapy

In solid tumors, tumor-associated macrophages (TAMs) are one of the most numerous populations and play an important role in the processes of tumor cell invasion, metastasis, and angiogenesis. Therefore, TAMs are considered promising diagnostic and prognostic biomarkers of tumors, and many attempts have been made to influence these cells as part of antitumor therapy. There are several key principles of action on ТАМs: the inhibition of monocyte/macrophage transition; the destruction of macrophages; the reprogramming of macrophage phenotypes (polarization of M2 macrophages to M1); the stimulation of phagocytic activity of macrophages and CAR-M therapy. Despite the large number of studies in this area, to date, there are no adequate approaches using antitumor therapy based on alterations in TAM functioning that would show high efficacy when administered in a mono-regimen for the treatment of malignant neoplasms. Studies devoted to the evaluation of the efficacy of drugs acting on TAMs are characterized by a small sample and the large heterogeneity of patient groups; in addition, in such studies, chemotherapy or immunotherapy is used, which significantly complicates the evaluation of the effectiveness of the agent acting on TAMs. In this review, we attempted to systematize the evidence on attempts to influence TAMs in malignancies such as lung cancer, breast cancer, colorectal cancer, cervical cancer, prostate cancer, gastric cancer, head and neck squamous cell cancer, and soft tissue sarcomas.

Phase Ib Clinical and Pharmacodynamic Study of the TIE2 Kinase Inhibitor Rebastinib with Paclitaxel or Eribulin in HER2-Negative Metastatic Breast Cancer

PURPOSE

Breast cancer cells disseminate to distant sites via tumor microenvironment of metastasis (TMEM) doorways. The TIE2 inhibitor rebastinib blocks TMEM doorway function in the PyMT mouse model of breast cancer. We aimed to assess the safety and pharmacodynamics of rebastinib plus paclitaxel or eribulin in patients with HER2-negative metastatic breast cancer (MBC).

PATIENTS AND METHODS

This phase Ib trial enrolled 27 patients with MBC who received 50 mg or 100 mg of rebastinib orally twice daily in combination with weekly paclitaxel 80 mg/m2 (if ≤2 prior non-taxane regimens) or eribulin 1.4 mg/m2 on days 1 and 8 (if ≥1 prior regimen). Safety, tolerability, and pharmacodynamic parameters indicating TIE2 kinase inhibition and TMEM doorway function were evaluated.

RESULTS

No dose-limiting toxicities in cycle 1 or 2 were observed among the first 12 patients at either rebastinib dose level. The most common treatment-emergent adverse events were anemia (85%), fatigue (78%), anorexia (67%), leukopenia (67%), increased alanine aminotransferase (59%), hyperglycemia (56%), nausea (52%), and neutropenia (52%). Adverse events attributed to rebastinib include muscular weakness and myalgias. Intraocular pressure increased at the 100-mg rebastinib dose level, whereas angiopoietin-2 levels increased at both dose levels, providing pharmacodynamic evidence for TIE2 blockade. Circulating tumor cells decreased significantly with the combined treatment. Objective response occurred in 5/23 (22%) evaluable patients.

CONCLUSIONS

In patients with MBC, the recommended phase II dose of rebastinib associated with pharmacodynamic evidence of TIE2 inhibition is either 50 or 100 mg orally twice daily in combination with paclitaxel or eribulin.

The Roles of Myeloid Cells in Breast Cancer Progression

This chapter reviews tumor-associated myeloid cells, including macrophages, neutrophils, and other innate immune cells, and their multifaceted roles in supporting breast cancer progression and metastasis. In primary tumors, myeloid cells play key roles in promoting tumor epithelial-mesenchymal transition (EMT) and invasion. They can facilitate intravasation (entry into the bloodstream) and colonization, disrupting the endothelial cell layer and reshaping the extracellular matrix. They can also stimulate angiogenesis, suppress immune cell responses, and enhance cancer cell adaptability. In the bloodstream, circulating myeloid cells enable the survival of disseminated tumor cells via immunosuppressive effects and physical shielding. At the metastatic sites, they prime the premetastatic niche, facilitate tumor cell extravasation, and support successful colonization and outgrowth. Mechanistically, myeloid cells enhance cancer cell survival, dormancy escape, proliferation, and mesenchymal-epithelial transition (MET). Nonetheless, substantial gaps in our understanding persist regarding the functional and spatiotemporal diversity, as well as the evolutionary patterns, of myeloid cells during metastatic progression. Myeloid cell plasticity and differential responses to therapies present key barriers to successful treatments. Identifying specific pro-tumoral myeloid cell subpopulations and disrupting their interactions with cancer cells represent promising therapeutic opportunities. Emerging evidence suggests combining immunomodulators or stromal normalizers with conventional therapies could help overcome therapy-induced immunosuppression and improve patient outcomes. Overall, further elucidating myeloid cell heterogeneity and function throughout the process of breast cancer progression and metastasis will enable more effective therapeutic targeting of these critical stromal cells.

The Microenvironment in DCIS and Its Role in Disease Progression

Ductal carcinoma in situ (DCIS) accounts for ~20% of all breast cancer diagnoses but whilst known to be a precursor of invasive breast cancer (IBC), evidence suggests only one in six patients will ever progress. A key challenge is to distinguish between those lesions that will progress and those that will remain indolent. Molecular analyses of neoplastic epithelial cells have not identified consistent differences between lesions that progressed and those that did not, and this has focused attention on the tumour microenvironment (ME).The DCIS ME is unique, complex and dynamic. Myoepithelial cells form the wall of the ductal-lobular tree and exhibit broad tumour suppressor functions. However, in DCIS they acquire phenotypic changes that bestow them with tumour promoter properties, an important evolution since they act as the primary barrier for invasion. Changes in the peri-ductal stromal environment also arise in DCIS, including transformation of fibroblasts into cancer-associated fibroblasts (CAFs). CAFs orchestrate other changes in the stroma, including the physical structure of the extracellular matrix (ECM) through altered protein synthesis, as well as release of a plethora of factors including proteases, cytokines and chemokines that remodel the ECM. CAFs can also modulate the immune ME as well as impact on tumour cell signalling pathways. The heterogeneity of CAFs, including recognition of anti-tumourigenic populations, is becoming evident, as well as heterogeneity of immune cells and the interplay between these and the adipocyte and vascular compartments. Knowledge of the impact of these changes is more advanced in IBC but evidence is starting to accumulate for a role in DCIS. Detailed in vitro, in vivo and tissue studies focusing on the interplay between DCIS epithelial cells and the ME should help to define features that can better predict DCIS behaviour.

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.

The tumor microenvironment of VETC+ hepatocellular carcinoma is enriched of immunosuppressive TAMs spatially close to endothelial cells

BACKGROUND AND AIM

VETC (vessel that encapsulate tumor cluster) is a peculiar vascular phenotype observed in hepatocellular carcinoma (HCC), associated with distant metastases and poor outcome. VETC has been linked to the Tie2/Ang2 axis and is characterized by lymphocytes poor (cold) tumor microenvironment (TME). In this setting the role of Tumor Associated Macrophages (TAMs) has never been explored. Aim of the study is to investigate the presence and features of TAMs in VETC+ HCC and the possible interplay between TAMs and endothelial cells (ECs).

METHODS

The series under study included 42 HCC. Once separated according to the VETC phenotype (21 VETC+; 21 VETC-) we stained consecutive slides with immunohistochemistry for CD68, CD163 and Tie2. Slides were then scanned and QuPath used to quantify morphological features.

RESULTS

VETC+ cases were significantly (p < 0.001) enriched with large, lipid rich CD163+ TAMs (M2 oriented) that were spatially close to ECs; HCC cells significantly (p: 0.002) overexpressed Tie2 with a polarization toward ECs.

CONCLUSIONS

The pro-metastatic attitude of VETC is sustained by a strict morphological relationship between immunosuppressive M2-TAMs, ECs and Tie2-expressing HCC cells.

Macrophage subtypes inhibit breast cancer proliferation in culture

Macrophages are a highly plastic cell type that adopt distinct subtypes and functional states depending on environmental cues. These functional states can vary widely, with distinct macrophages capable of displaying opposing functions. We sought to understand how macrophage subtypes that exist on two ends of a spectrum influence the function of other cells. We used a coculture system with primary human macrophages to probe the effects of macrophage subtypes on breast cancer cell proliferation. Our studies revealed a surprising phenotype in which both macrophage subtypes inhibited cancer cell proliferation compared with cancer cells alone. Of particular interest, using two different proliferation assays with two different breast cancer cell lines, we showed that differentiating macrophages into a "protumor" subtype inhibited breast cancer cell proliferation. These findings are inconsistent with the prevailing interpretation that "protumor" macrophages promote cancer cell proliferation and suggest a re-evaluation of how these interpretations are made.

Mechanical deformation and death of circulating tumor cells in the bloodstream

The circulation of tumor cells through the bloodstream is a significant step in tumor metastasis. To better understand the metastatic process, circulating tumor cell (CTC) survival in the circulation must be explored. While immune interactions with CTCs in recent decades have been examined, research has yet to sufficiently explain some CTC behaviors in blood flow. Studies related to CTC mechanical responses in the bloodstream have recently been conducted to further study conditions under which CTCs might die. While experimental methods can assess the mechanical properties and death of CTCs, increasingly sophisticated computational models are being built to simulate the blood flow and CTC mechanical deformation under fluid shear stresses (FSS) in the bloodstream.Several factors contribute to the mechanical deformation and death of CTCs as they circulate. While FSS can damage CTC structure, diverse interactions between CTCs and blood components may either promote or hinder the next metastatic step-extravasation at a remote site. Overall understanding of how these factors influence the deformation and death of CTCs could serve as a basis for future experiments and simulations, enabling researchers to predict CTC death more accurately. Ultimately, these efforts can lead to improved metastasis-specific therapeutics and diagnostics specific in the future.

Exosomal integrins in tumor progression, treatment and clinical prediction (Review)

Integrins are a large family of cell adhesion molecules involved in tumor cell differentiation, migration, proliferation and neovascularization. Tumor cell‑derived exosomes carry a large number of integrins, which are closely associated with tumor progression. As crucial mediators of intercellular communication, exosomal integrins have gained attention in the field of cancer biology. The present review examined the regulatory mechanisms of exosomal integrins in tumor cell proliferation, migration and invasion, and emphasized their notable roles in tumor initiation and progression. The potential of exosomal integrins as drug delivery systems in cancer treatment was explored. Additionally, the potential of exosomal integrins in clinical tumor prediction was considered, while summarizing their applications in diagnosis, prognosis assessment and treatment response prediction. Thus, the present review aimed to provide guidance and insights for future basic research and the clinical translation of exosomal integrins. The study of exosomal integrins is poised to offer new perspectives and methods for precise cancer treatment and clinical prediction.

Current biological implications and clinical relevance of metastatic circulating tumor cells

Metastatic disease and cancer recurrence are the primary causes of cancer-related deaths. Circulating tumor cells (CTCs) and disseminated tumor cells (DTCs) are the driving forces behind the spread of cancer cells. The emergence and development of liquid biopsy using rare CTCs as a minimally invasive strategy for early-stage tumor detection and improved tumor management is a promising advancement in recent years. However, before blood sample analysis and clinical translation, precise isolation of CTCs from patients' blood based on their biophysical properties, followed by molecular identification of CTCs using single-cell multi-omics technologies is necessary to understand tumor heterogeneity and provide effective diagnosis and monitoring of cancer progression. Additionally, understanding the origin, morphological variation, and interaction between CTCs and the primary and metastatic tumor niche, as well as and regulatory immune cells, will offer new insights into the development of CTC-based advanced tumor targeting in the future clinical trials.

Patient-derived organoids in precision cancer medicine

Organoids are three-dimensional (3D) cultures, normally derived from stem cells, that replicate the complex structure and function of human tissues. They offer a physiologically relevant model to address important questions in cancer research. The generation of patient-derived organoids (PDOs) from various human cancers allows for deeper insights into tumor heterogeneity and spatial organization. Additionally, interrogating non-tumor stromal cells increases the relevance in studying the tumor microenvironment, thereby enhancing the relevance of PDOs in personalized medicine. PDOs mark a significant advancement in cancer research and patient care, signifying a shift toward more innovative and patient-centric approaches. This review covers aspects of PDO cultures to address the modeling of the tumor microenvironment, including extracellular matrices, air-liquid interface and microfluidic cultures, and organ-on-chip. Specifically, the role of PDOs as preclinical models in gene editing, molecular profiling, drug testing, and biomarker discovery and their potential for guiding personalized treatment in clinical practice are discussed.

Macrophages in tumor cell migration and metastasis

Tumor-associated macrophages (TAMs) are a phenotypically diverse, highly plastic population of cells in the tumor microenvironment (TME) that have long been known to promote cancer progression. In this review, we summarize TAM ontogeny and polarization, and then explore how TAMs enhance tumor cell migration through the TME, thus facilitating metastasis. We also discuss how chemotherapy and host factors including diet, obesity, and race, impact TAM phenotype and cancer progression. In brief, TAMs induce epithelial-mesenchymal transition (EMT) in tumor cells, giving them a migratory phenotype. They promote extracellular matrix (ECM) remodeling, allowing tumor cells to migrate more easily. TAMs also provide chemotactic signals that promote tumor cell directional migration towards blood vessels, and then participate in the signaling cascade at the blood vessel that allows tumor cells to intravasate and disseminate throughout the body. Furthermore, while chemotherapy can repolarize TAMs to induce an anti-tumor response, these cytotoxic drugs can also lead to macrophage-mediated tumor relapse and metastasis. Patient response to chemotherapy may be dependent on patient-specific factors such as diet, obesity, and race, as these factors have been shown to alter macrophage phenotype and affect cancer-related outcomes. More research on how chemotherapy and patient-specific factors impact TAMs and cancer progression is needed to refine treatment strategies for cancer patients.

Macrophage diversity in cancer dissemination and metastasis

Invasion and metastasis are hallmarks of cancer. In addition to the well-recognized hematogenous and lymphatic pathways of metastasis, cancer cell dissemination can occur via the transcoelomic and perineural routes, which are typical of ovarian and pancreatic cancer, respectively. Macrophages are a universal major component of the tumor microenvironment and, in established tumors, promote growth and dissemination to secondary sites. Here, we review the role of tumor-associated macrophages (TAMs) in cancer cell dissemination and metastasis, emphasizing the diversity of myeloid cells in different tissue contexts (lungs, liver, brain, bone, peritoneal cavity, nerves). The generally used models of lung metastasis fail to capture the diversity of pathways and tissue microenvironments. A better understanding of TAM diversity in different tissue contexts may pave the way for tailored diagnostic and therapeutic approaches.

Spatial mapping of the HCC landscape identifies unique intratumoral perivascular-immune neighborhoods

BACKGROUND

HCC develops in the context of chronic inflammation; however, the opposing roles the immune system plays in both the development and control of tumors are not fully understood. Mapping immune cell interactions across the distinct tissue regions could provide greater insight into the role individual immune populations have within tumors.

METHODS

A 39-parameter imaging mass cytometry panel was optimized with markers targeting immune cells, stromal cells, endothelial cells, hepatocytes, and tumor cells. We mapped the immune landscape of tumor, invasive margin, and adjacent nontumor regions across 16 resected tumors comprising 144 regions of interest. X-shift clustering and manual gating were used to characterize cell subsets, and Spectre quantified the spatial environment to identify cellular neighborhoods. Ligand-receptor communication was quantified on 2 single-cell RNA-sequencing data sets and 1 spatial transcriptomic data set.

RESULTS

We show immune cell densities remain largely consistent across these 3 regions, except for subsets of monocyte-derived macrophages, which are enriched within the tumors. Mapping cellular interactions across these regions in an unbiased manner identifies immune neighborhoods comprised of tissue-resident T cells, dendritic cells, and various macrophage populations around perivascular spaces. Importantly, we identify multiple immune cells within these neighborhoods interacting with VEGFA+ perivascular macrophages. VEGFA was further identified as a ligand for communication between perivascular macrophages and CD34+ endothelial cells.

CONCLUSIONS

Immune cell neighborhood interactions, but not cell densities, differ between intratumoral and adjacent nontumor regions in HCC. Unique intratumoral immune neighborhoods around the perivascular space point to an altered landscape within tumors. Enrichment of VEGFA+ perivascular macrophages within these tumors could play a key role in angiogenesis and vascular permeability.

Subverting Attachment to Prevent Attacking: Alteration of Effector Immune Cell Migration and Adhesion as a Key Mechanism of Tumor Immune Evasion

Cell adhesion regulates specific migratory patterns, location, communication with other cells, physical interactions with the extracellular matrix, and the establishment of effector programs. Proper immune control of cancer strongly depends on all these events occurring in a highly accurate spatiotemporal sequence. In response to cancer-associated inflammatory signals, effector immune cells navigating the bloodstream shift from their patrolling exploratory migration mode to establish adhesive interactions with vascular endothelial cells. This interaction enables them to extravasate through the blood vessel walls and access the cancer site. Further adhesive interactions within the tumor microenvironment (TME) are crucial for coordinating their distribution in situ and for mounting an effective anti-tumor immune response. In this review, we examine how alterations of adhesion cues in the tumor context favor tumor escape by affecting effector immune cell infiltration and trafficking within the TME. We discuss the mechanisms by which tumors directly modulate immune cell adhesion and migration patterns to affect anti-tumor immunity and favor tumor evasion. We also explore indirect immune escape mechanisms that involve modifications of TME characteristics, such as vascularization, immunogenicity, and structural topography. Finally, we highlight the significance of these aspects in designing more effective drug treatments and cellular immunotherapies.

Intratumoral CXCL12 Gradients Contextualize Tumor Cell Invasion, Migration and Immune Suppression in Breast Cancer

Although the CXCL12/CXCR4 pathway has been prior investigated for its prometastatic and immuno- suppressive roles in the tumor microenvironment, evidence on the spatiotemporal regulation of these hallmarks has been lacking. Here, we demonstrate that CXCL12 forms a gradient specifically around cancer cell intravasation doorways, also known as Tumor Microenvironment of Metastasis (TMEM) doorways, thus facilitating the chemotactic translocation of prometastatic tumor cells expressing CXCR4 toward the perivascular TMEM doorways for subsequent entry into peripheral circulation. Fur- thermore, we demonstrate that the CXCL12-rich micro-environment around TMEM doorways may cre- ate immunosuppressive niches, whereby CD8 + T cells, despite being attracted to these regions, often exhibit reduced effector functions, limiting their efficacy. While the CXCL12/CXCR4 pathway can mini- mally influence the overall composition of immune cell populations, it biases the distribution of CD8 + T cells away from TMEM doorways, justifying its prior-established role as immunosuppressive factor for CD8 + T cells. Our research suggests that the complex interactions between CXCL12 and the various tumor and immune cell types contributes not only to the completion of the initial steps of the metastatic cascade, but also offers an immunological "sanctuary" to prometastatic tumor cells homed around TMEM doorways. Overall, our study enhances our current understanding on the mechanisms, via which CXCL12 orchestrates tumor cell behavior and immune dynamics, potentially guiding future thera- peutic strategies to combat breast cancer metastasis and improve anti-tumor immunity.

SPOP downregulation promotes bladder cancer progression based on cancer cell-macrophage crosstalk via STAT3/CCL2/IL-6 axis and is regulated by VEZF1

Background: Cancer cells are intimately intertwined with tumor microenvironment (TME), fostering a symbiotic relationship propelling cancer progression. However, the interaction between cancer cells and tumor-associated macrophages (TAMs) in urothelial bladder cancer (UBC) remains poorly understood. Methods: UBC cell lines (5637, T24 and SW780), along with a monocytic cell line (U937) capable of differentiating into macrophage, were used in a co-culture system for cell proliferation and stemness by MTT, sphere formation assays. VEZF1/SPOP/STAT3/CCL2/ IL-6 axis was determined by luciferase reporter, ChIP, RNA-seq, co-IP, in vitro ubiquitination, RT-qPCR array and ELISA analyses. Results: We observed the frequent downregulation of SPOP, an E3 ubiquitin ligase, was positively associated with tumor progression and TAM infiltration in UBC patients and T24 xenografts. Cancer cell-TAM crosstalk promoting tumor aggressiveness was demonstrated dependent on SPOP deficiency: 1) In UBC cells, STAT3 was identified as a novel substrate of SPOP, and SPOP deficiency increased STAT3 protein stability, elevated chemokine CCL2 secretion, which induced chemotaxis and M2 polarization of macrophage; 2) In co-cultured macrophages, IL-6 secretion enhanced UBC cell proliferation and stemness. Additionally, transcription factor VEZF1 could directly activate SPOP transcription, and its overexpression suppressed the above effects in UBC cells. Conclusions: A pivotal role of SPOP in maintaining UBC stemness and remodeling immunosuppressive TME was revealed. Both the intrinsic signaling (dysregulated VEZF1/SPOP/STAT3 axis) and the extrinsic cues from TME (CCL2-IL-6 axis based on macrophages) promoted UBC progression. Targeting this crosstalk may offer a promising therapeutic strategy for UBC patients with SPOP deficiency.

Pre-metastatic niche: formation, characteristics and therapeutic implication

Distant metastasis is a primary cause of mortality and contributes to poor surgical outcomes in cancer patients. Before the development of organ-specific metastasis, the formation of a pre-metastatic niche is pivotal in promoting the spread of cancer cells. This review delves into the intricate landscape of the pre-metastatic niche, focusing on the roles of tumor-derived secreted factors, extracellular vesicles, and circulating tumor cells in shaping the metastatic niche. The discussion encompasses cellular elements such as macrophages, neutrophils, bone marrow-derived suppressive cells, and T/B cells, in addition to molecular factors like secreted substances from tumors and extracellular vesicles, within the framework of pre-metastatic niche formation. Insights into the temporal mechanisms of pre-metastatic niche formation such as epithelial-mesenchymal transition, immunosuppression, extracellular matrix remodeling, metabolic reprogramming, vascular permeability and angiogenesis are provided. Furthermore, the landscape of pre-metastatic niche in different metastatic organs like lymph nodes, lungs, liver, brain, and bones is elucidated. Therapeutic approaches targeting the cellular and molecular components of pre-metastatic niche, as well as interventions targeting signaling pathways such as the TGF-β, VEGF, and MET pathways, are highlighted. This review aims to enhance our understanding of pre-metastatic niche dynamics and provide insights for developing effective therapeutic strategies to combat tumor metastasis.

The complex role of macrophages in pancreatic cancer tumor microenvironment: a review on cancer progression and potential therapeutic targets

Pancreatic cancer (PC) is one of the deadliest cancers worldwide with low survival rates and poor outcomes. The treatment landscape for PC is fraught with obstacles, including drug resistance, lack of effective targeted therapies and the immunosuppressive tumor microenvironment (TME). The resistance of PC to existing immunotherapies highlights the need for innovative approaches, with the TME emerging as a promising therapeutic target. The recent advancements in understanding the role of macrophages, this context highlight their significant impact on tumor development and progression. There are two important types of macrophages: M1 and M2, which play critical roles in the TME. Therapeutics strategies including, depletion of tumor-associated macrophages (TAMs), reprogramming TAMs to promote anti-tumor activity, and targeting macrophage recruitment can lead to promising outcomes. Targeting macrophage-related pathways may offer novel strategies for modulating immune responses, inhibiting angiogenesis, and overcoming resistance to chemotherapy in PC treatment.

Navigating tumor angiogenesis: therapeutic perspectives and myeloid cell regulation mechanism

Sustained angiogenesis stands as a hallmark of cancer. The intricate vascular tumor microenvironment fuels cancer progression and metastasis, fosters therapy resistance, and facilitates immune evasion. Therapeutic strategies targeting tumor vasculature have emerged as transformative for cancer treatment, encompassing anti-angiogenesis, vessel normalization, and endothelial reprogramming. Growing evidence suggests the dynamic regulation of tumor angiogenesis by infiltrating myeloid cells, such as macrophages, myeloid-derived suppressor cells (MDSCs), and neutrophils. Understanding these regulatory mechanisms is pivotal in paving the way for successful vasculature-targeted cancer treatments. Therapeutic interventions aimed to disrupt myeloid cell-mediated tumor angiogenesis may reshape tumor microenvironment and overcome tumor resistance to radio/chemotherapy and immunotherapy.

How much do we know about the metastatic process?

Cancer cells can leave their primary sites and travel through the circulation to distant sites, where they lodge as disseminated cancer cells (DCCs), even during the early and asymptomatic stages of tumor progression. In experimental models and clinical samples, DCCs can be detected in a non-proliferative state, defined as cellular dormancy. This state can persist for extended periods until DCCs reawaken, usually in response to niche-derived reactivation signals. Therefore, their clinical detection in sites like lymph nodes and bone marrow is linked to poor survival. Current cancer therapy designs are based on the biology of the primary tumor and do not target the biology of the dormant DCC population and thus fail to eradicate the initial or subsequent waves of metastasis. In this brief review, we discuss the current methods for detecting DCCs and highlight new strategies that aim to target DCCs that constitute minimal residual disease to reduce or prevent metastasis formation. Furthermore, we present current evidence on the relevance of DCCs derived from early stages of tumor progression in metastatic disease and describe the animal models available for their study. We also discuss our current understanding of the dissemination mechanisms utilized by genetically less- and more-advanced cancer cells, which include the functional analysis of intermediate or hybrid states of epithelial-mesenchymal transition (EMT). Finally, we raise some intriguing questions regarding the clinical impact of studying the crosstalk between evolutionary waves of DCCs and the initiation of metastatic disease.

Research advances on signaling pathways regulating the polarization of tumor-associated macrophages in lung cancer microenvironment

Lung cancer (LC) is one of the most common cancer worldwide. Tumor-associated macrophages (TAMs) are important component of the tumor microenvironment (TME) and are closely related to the stages of tumor occurrence, development, and metastasis. Macrophages are plastic and can differentiate into different phenotypes and functions under the influence of different signaling pathways in TME. The classically activated (M1-like) and alternatively activated (M2-like) represent the two polarization states of macrophages. M1 macrophages exhibit anti-tumor functions, while M2 macrophages are considered to support tumor cell survival and metastasis. Macrophage polarization involves complex signaling pathways, and blocking or regulating these signaling pathways to enhance macrophages' anti-tumor effects has become a research hotspot in recent years. At the same time, there have been new discoveries regarding the modulation of TAMs towards an anti-tumor phenotype by synthetic and natural drug components. Nanotechnology can better achieve combination therapy and targeted delivery of drugs, maximizing the efficacy of the drugs while minimizing side effects. Up to now, nanomedicines targeting the delivery of various active substances for reprogramming TAMs have made significant progress. In this review, we primarily provided a comprehensive overview of the signaling crosstalk between TAMs and various cells in the LC microenvironment. Additionally, the latest advancements in novel drugs and nano-based drug delivery systems (NDDSs) that target macrophages were also reviewed. Finally, we discussed the prospects of macrophages as therapeutic targets and the barriers to clinical translation.

Decoding the spatiotemporal heterogeneity of tumor-associated macrophages

Tumor-associated macrophages (TAMs) are pivotal in cancer progression, influencing tumor growth, angiogenesis, and immune evasion. This review explores the spatial and temporal heterogeneity of TAMs within the tumor microenvironment (TME), highlighting their diverse subtypes, origins, and functions. Advanced technologies such as single-cell sequencing and spatial multi-omics have elucidated the intricate interactions between TAMs and other TME components, revealing the mechanisms behind their recruitment, polarization, and distribution. Key findings demonstrate that TAMs support tumor vascularization, promote epithelial-mesenchymal transition (EMT), and modulate extracellular matrix (ECM) remodeling, etc., thereby enhancing tumor invasiveness and metastasis. Understanding these complex dynamics offers new therapeutic targets for disrupting TAM-mediated pathways and overcoming drug resistance. This review underscores the potential of targeting TAMs to develop innovative cancer therapies, emphasizing the need for further research into their spatial characteristics and functional roles within the TME.

Current computational methods for spatial transcriptomics in cancer biology

Cells in multicellular organisms constitute a self-organizing society by interacting with their neighbors. Cancer originates from malfunction of cellular behavior in the context of such a self-organizing system. The identities or characteristics of individual tumor cells can be represented by the hallmark of gene expression or transcriptome, which can be addressed using single-cell dissociation followed by RNA sequencing. However, the dissociation process of single cells results in losing the cellular address in tissue or neighbor information of each tumor cell, which is critical to understanding the malfunctioning cellular behavior in the microenvironment. Spatial transcriptomics technology enables measuring the transcriptome which is tagged by the address within a tissue. However, to understand cellular behavior in a self-organizing society, we need to apply mathematical or statistical methods. Here, we provide a review on current computational methods for spatial transcriptomics in cancer biology.

Numerical investigation on flow-induced wall shear stress variation of metastatic cancer cells in lymphatics with elastic valves

Hematogenous metastasis occurs when cancer cells detach from the extracellular matrix in the primary tumor into the bloodstream or lymphatic system. Elucidating the response of metastatic tumor cells in suspension to the flow conditions in lymphatics with valves from a mechanical/fluidic perspective is necessary. A physiologically relevant computational model of a lymphatic vessel with valves was constructed using fully coupled fluid-cell-vessel interactions to investigate the effects of lymphatic vessel contractility, valve properties, and cell size and stiffness on the variations in magnitude and gradient of the flow-induced wall shear stress (WSS) experienced by suspended tumor cells. Results indicated that the maximum WSSmax increased with the increments in cell diameter, vessel contraction amplitude, and valve stiffness. The decrease in vessel contraction period and valve aspect ratio also increased the maximum WSSmax. The influence of the properties of the valve on the WSS was more significant among the factors mentioned above. The maximum WSSmax acting on the cancer cell when the cell reversed the direction of its motion in the valve region increased by 0.5-1.4 times that before the cell entered the valve region. The maximum change in WSS was in the range of 0.004-0.028 Pa/µm depending on the factors studied. They slightly exceeded the values associated with breast cancer cell apoptosis. The results of this study provide biofluid mechanics-based support for mechanobiological research on the metastasis of metastatic cancer cells in suspension within the lymphatics.

An update to experimental and clinical aspects of tumor-associated macrophages in cancer development: hopes and pitfalls

Tumor-associated macrophages (TAMs) represent one of the most abundant tumor-infiltrating stromal cells, and their normal function in tumor microenvironment (TME) is to suppress tumor cells by producing cytokines which trigger both direct cell cytotoxicity and antibody-mediated immune response. However, upon prolonged exposure to TME, the classical function of these so-called M1-type TAMs can be converted to another type, "M2-type," which are recruited by tumor cells so that they promote tumor growth and metastasis. This is the reason why the accumulation of TAMs in TME is correlated with poor prognosis in cancer patients. Both M1- and M2-types have high degree of plasticity, and M2-type cells can be reprogrammed to M1-type for therapeutic purposes. This characteristic introduces TAMs as promising target for developing novel cancer treatments. In addition, inhibition of M2-type cells and blocking their recruitment in TME, as well as their depletion by inducing apoptosis, are other approaches for effective immunotherapy of cancer. In this review, we summarize the potential of TAMs to be targeted for cancer immunotherapy and provide an up-to-date about novel strategies for targeting TAMs.

A Novel Method for the Early Detection of Single Circulating, Metastatic and Self-Seeding Cancer Cells in Orthotopic Breast Cancer Mouse Models

BACKGROUND

Metastasis is the main cause of cancer-related deaths, but efficient targeted therapies against metastasis are still missing. Major gaps exist in our understanding of the metastatic cascade, as existing methods cannot combine sensitivity, robustness, and practicality to dissect cancer progression. Addressing this issue requires improved strategies to distinguish early metastatic colonization from metastatic outgrowth.

METHODS

Luciferase-labelled MDA-MB-231, MCF7, and 4T1 breast cancer cells were spiked into samples from tumour-naïve mice to establish the limit of detection for disseminated tumour cells. Luciferase-labelled breast cancer cells (±unlabelled cancer-associated fibroblasts; CAFs) were orthotopically implanted in immunocompromised mice. An ex vivo luciferase assay was used to quantify tumour cell dissemination.

RESULTS

In vitro luciferase assay confirmed a linear and positive correlation between cancer cell numbers and the bioluminescence detected at single cell level in blood, brain, lung, liver, and mammary fat pad samples. Remarkably, single luciferase-labelled cancer cells were detectable in all of these sites, as the bioluminescence quantified in the analysed samples was substantially higher than background levels. Ex vivo, circulating tumour cells, metastasis, and tumour self-seeding were detected in all samples from animals implanted with highly metastatic luciferase-labelled MDA-MB-231 cells. In turn, detection of poorly metastatic luciferase-labelled MCF7 cells was scarce but significantly enhanced upon co-implantation with CAFs as early as 20 days after the experiment was initiated.

CONCLUSIONS

These results demonstrate the feasibility of using an ultrasensitive luciferase-based method to dissect the mechanisms of early metastatic colonization to improving the development of antimetastatic therapies.

The role of endothelial junctions in the regulation of the extravasation of tumor cells. A historical reappraisal

Endothelial cells lining the vessel wall are connected by adherent, tight and gap junctions. Adherent junctions are common to all endothelial cells, whereas tight and gap junctions graduate within different vascular segments. Endothelial cell-cell junctions sustain vascular homeostasis and to control the transendothelial migration of inflammatory cells. Tumor cells need to weaken endothelial cell-cell junctions to penetrate the endothelial barrier and transendothelial migration and metastasis of tumor cells are tightly controlled by endothelial cell-cell junctions.

Characterisation of circulating tumor-associated and immune cells in patients with advanced-stage non-small cell lung cancer

Objectives

Globally, non-small cell lung cancer (NSCLC) is the most prevalent form of lung cancer and the leading cause of cancer-related deaths. Tumor-associated circulating cells in NSCLC can have a wide variety of morphological and phenotypic characteristics, including epithelial, immunological or hybrid subtypes. The distinctive characteristics and potential clinical significance of these cells in patients with NSCLC are explored in this study.

Methods

We utilised a spiral microfluidic device to enrich large cells and cell aggregates from the peripheral blood samples of NSCLC patients. These cells were characterised through high-resolution immunofluorescent imaging and statistical analysis, correlating findings with clinical information from our patient cohort.

Results

We have identified varied populations of heterotypic circulating tumor cell clusters with differing immune cell composition that included a distinct class of atypical tumor-associated macrophages that exhibits unique morphology and cell size. This subtype's prevalence is positively correlated with the tumor stage, progression and metastasis.

Conclusions

Our study reveals a heterogeneous landscape of circulating tumor cells and their clusters, underscoring the complexity of NSCLC pathobiology. The identification of a unique subtype of atypical tumor-associatedmacrophages that simultaneously express both tumor and immune markers and whose presence correlates with late disease stages, poor clinical outcomes and metastatic risk infers  the potential of these cells as biomarkers for NSCLC staging and prognosis. Future studies should focus on the role of these cells in the tumor microenvironment and their potential as therapeutic targets. Additionally, longitudinal studies tracking these cell types through disease progression could provide further insights into their roles in NSCLC evolution and response to treatment.

Macrophage subtypes inhibit breast cancer proliferation in culture

Macrophages are a highly plastic cell type that adopt distinct subtypes and functional states depending on environmental cues. These functional states can vary wildly, with distinct macrophages capable of displaying opposing functions. We sought to understand how macrophage subtypes that exist on two ends of a spectrum influence the function of other cells. We used a co-culture system with primary human macrophages to probe the effects of macrophage subtypes on breast cancer cell proliferation. Our studies revealed a surprising phenotype in which both macrophage subtypes inhibited cancer cell proliferation compared to cancer cells alone. Of particular interest, using two different proliferation assays with two different breast cancer cell lines, we showed that differentiating macrophages into a "pro-tumor" subtype inhibited breast cancer cell proliferation. These findings are inconsistent with the prevailing interpretation that "pro-tumor" macrophages promote cancer cell proliferation and suggest a re-evaluation of how these interpretations are made.

Milestones in tumor vascularization and its therapeutic targeting

Research into the mechanisms and manifestations of solid tumor vascularization was launched more than 50 years ago with the proposition and experimental demonstrations that angiogenesis is instrumental for tumor growth and was, therefore, a promising therapeutic target. The biological knowledge and therapeutic insights forthcoming have been remarkable, punctuated by new concepts, many of which were not foreseen in the early decades. This article presents a perspective on tumor vascularization and its therapeutic targeting but does not portray a historical timeline. Rather, we highlight eight conceptual milestones, integrating initial discoveries and recent progress and posing open questions for the future.

Targeting tumor-associated macrophages to reverse antitumor drug resistance

Currently, antitumor drugs show limited clinical outcomes, mainly due to adaptive resistance. Clinical evidence has highlighted the importance of the tumor microenvironment (TME) and tumor-associated macrophages (TAMs) in tumor response to conventional antitumor drugs. Preclinical studies show that TAMs following antitumor agent can be reprogrammed to an immunosuppressive phenotype and proangiogenic activities through different mechanisms, mediating drug resistance and poor prognosis. Potential extrinsic inhibitors targeting TAMs repolarize to an M1-like phenotype or downregulate proangiogenic function, enhancing therapeutic efficacy of anti-tumor therapy. Moreover, pharmacological modulation of macrophages that restore the immune stimulatory characteristics is useful to reshaping the tumor microenvironment, thus further limiting tumor growth. This review aims to introduce macrophage response in tumor therapy and provide a potential therapeutic combination strategy of TAM-targeting immunomodulation with conventional antitumor drugs.

Signaling crosstalk between tumor endothelial cells and immune cells in the microenvironment of solid tumors

Tumor-associated endothelial cells (TECs) are crucial mediators of immune surveillance and immune escape in the tumor microenvironment (TME). TECs driven by angiogenic growth factors form an abnormal vasculature which deploys molecular machinery to selectively promote the function and recruitment of immunosuppressive cells while simultaneously blocking the entry and function of anti-tumor immune cells. TECs also utilize a similar set of signaling regulators to promote the metastasis of tumor cells. Meanwhile, the tumor-infiltrating immune cells further induce the TEC anergy by secreting pro-angiogenic factors and prevents further immune cell penetration into the TME. Understanding the complex interactions between TECs and immune cells will be needed to successfully treat cancer patients with combined therapy to achieve vasculature normalization while augmenting antitumor immunity. In this review, we will discuss what is known about the signaling crosstalk between TECs and tumor-infiltrating immune cells to reveal insights and strategies for therapeutic targeting.

A high-cholesterol diet promotes the intravasation of breast tumor cells through an LDL-LDLR axis

Most metastases in breast cancer occur via the dissemination of tumor cells through the bloodstream. How tumor cells enter the blood (intravasation) is, however, a poorly understood mechanism at the cellular and molecular levels. Particularly uncharacterized is how intravasation is affected by systemic nutrients. High levels of systemic LDL-cholesterol have been shown to contribute to breast cancer progression and metastasis in various models, but the cellular and molecular mechanisms involved are still undisclosed. Here we show that a high- cholesterol diet promotes intravasation in two mouse models of breast cancer and that this could be reverted by blocking LDL binding to LDLR in tumor cells. Moreover, we show that LDL promotes vascular invasion in vitro and the intercalation of tumor cells with endothelial cells, a phenotypic change resembling vascular mimicry (VM). At the molecular level, LDL increases the expression of SERPINE2, previously shown to be required for both VM and intravasation. Overall, our manuscript unravels novel mechanisms by which systemic hypercholesterolemia may affect the onset of metastatic breast cancer by favouring phenotypic changes in breast cancer cells and increasing intravasation.

PDGFRα+ITGA11+ fibroblasts foster early-stage cancer lymphovascular invasion and lymphatic metastasis via ITGA11-SELE interplay

Cancer-associated fibroblasts (CAFs) exhibit considerable heterogeneity in advanced cancers; however, the functional annotation and mechanism of CAFs in early-stage cancers remain elusive. Utilizing single-cell RNA sequencing and spatial transcriptomic, we identify a previously unknown PDGFRα+ITGA11+ CAF subset in early-stage bladder cancer (BCa). Multicenter clinical analysis of a 910-case cohort confirms that PDGFRα+ITGA11+ CAFs are associated with lymphovascular invasion (LVI) and poor prognosis in early-stage BCa. These CAFs facilitate LVI and lymph node (LN) metastasis in early-stage BCa, as evidenced in a PDGFRα+ITGA11+ CAFs-specific deficient mouse model. Mechanistically, PDGFRα+ITGA11+ CAFs promote lymphangiogenesis via recognizing ITGA11 surface receptor SELE on lymphatic endothelial cells to activate SRC-p-VEGFR3-MAPK pathway. Further, CHI3L1 from PDGFRα+ITGA11+ CAFs aligns the surrounding matrix to assist cancer cell intravasation, fostering early-stage BCa LVI and LN metastasis. Collectively, our study reveals the crucial role of PDGFRα+ITGA11+ CAFs in shaping metastatic landscape, informing the treatment of early-stage BCa LVI.

Circadian regulation of cancer stem cells and the tumor microenvironment during metastasis

The circadian clock regulates daily rhythms of numerous physiological activities through tightly coordinated modulation of gene expression and biochemical functions. Circadian disruption is associated with enhanced tumor formation and metastasis via dysregulation of key biological processes and modulation of cancer stem cells (CSCs) and their specialized microenvironment. Here, we review how the circadian clock influences CSCs and their local tumor niches in the context of different stages of tumor metastasis. Identifying circadian therapeutic targets could facilitate the development of new treatments that leverage circadian modulation to ablate tumor-resident CSCs, inhibit tumor metastasis and enhance response to current therapies.

Curcuma longa extract inhibits migration by reducing MMP-9 and Rac-1 expression in highly metastatic breast cancer cells

Background and purpose

Highly metastatic breast cancer is a population of cancer cells that has metastasized to other organs in the body leading to apoptosis resistance. It was reported that MDAMB-231 cells contain lower levels of reactive oxygen species associated with metastatic capability. Curcuma longa (CL) possesses cytotoxic effects in several cancer cells including metastatic breast cancer cells. This study aimed to investigate the effect of CL-inhibited cell migration in highly metastatic breast cancer MDAMB-231 cells.

Experimental approach

CL was extracted under maceration with methanol. The cytotoxic effect on single and combination treatment of CL was assessed through the MTT assay. Migration analysis was evaluated using scratch wound healing assay, MMP-9 expression by gelatine zymography, Rac-1, and MMP-9 gene expression using Real-Time Quantitative Reverse transcription polymerase chain reaction (qRT-PCR). The apoptosis induction was analyzed through Bax gene expression and Bcl-2 protein expression.

Findings/Results

We found that CL inhibits the growth of MDAMB-231 cells, induces Bax gene expression, and suppresses Bcl-2 expression in a dose-dependent manner. Moreover, cancer cell migration was suppressed by the presence of CL. qRT-PCR and gelatine zymography assay showed that CL downregulates Rac-1 and MMP-9 gene expression.

Conclusion and implications

CL could inhibit the growth and migration of highly metastatic breast cancer cells by reducing the Rac-1 gene expression and regulating apoptosis protein expression.

Circulating tumor cells in lung cancer: Integrating stemness and heterogeneity to improve clinical utility

Circulating tumor cells (CTC), released by primary tumors into the bloodstream, represent a valuable source to inform on cancer heterogeneity, cancer progression, metastatic disease and therapy efficacy without the need of invasive tumor biopsies. However, the extreme rarity and heterogeneity of CTCs, occurring at genotypic, phenotypic and functional levels, poses a major challenge for the study of this population and explains the lack of standardized strategies of CTC isolation. Lung cancer, the leading causes of cancer-related death worldwide, is a paradigmatic example of how CTC heterogeneity can undermine the clinical utility of this biomarker, since contrasting data have been reported using different isolation technologies. Some evidences suggest that only a fraction of CTC, characterized by stem-like feature and partial epithelial-mesenchymal transition (EMT) phenotype, can sustain metastasis initiation. Cancer stem cells (CSCs) have the potential to maintain primary tumors, initiate metastasis and escape both chemotherapy and immunotherapy treatments. Moreover, a close connection has been reported in several tumor types among hybrid phenotype, characterized by retention of epithelial and mesenchymal traits, acquisition of CSC feature and increased metastatic potential. This review focuses on the phenotypic and functional heterogeneity of CTCs and the resulting implications for their isolation and clinical validation, especially in the setting of non-small cell lung cancer (NSCLC). In particular, we discuss the most relevant studies providing evidence for the presence and prognostic/predictive value of CTC subsets characterized by stem-like and hybrid EMT phenotype. Despite technical and conceptual issues, tracking circulating CSCs has the potential to improve the prognostic/predictive value of CTCs in NSCLC setting and could provide novel insights into the comprehension of the metastatic process and identification of novel therapeutic targets.

Understanding organotropism in cancer metastasis using microphysiological systems

Cancer metastasis, the leading cause of cancer-related deaths, remains a complex challenge in medical science. Stephen Paget's "seed and soil theory" introduced the concept of organotropism, suggesting that metastatic success depends on specific organ microenvironments. Understanding organotropism not only offers potential for curbing metastasis but also novel treatment strategies. Microphysiological systems (MPS), especially organ-on-a-chip models, have emerged as transformative tools in this quest. These systems, blending microfluidics, biology, and engineering, grant precise control over cell interactions within organ-specific microenvironments. MPS enable real-time monitoring, morphological analysis, and protein quantification, enhancing our comprehension of cancer dynamics, including tumor migration, vascularization, and pre-metastatic niches. In this review, we explore innovative applications of MPS in investigating cancer metastasis, particularly focusing on organotropism. This interdisciplinary approach converges the field of science, engineering, and medicine, thereby illuminating a path toward groundbreaking discoveries in cancer research.