Kupffer cells prevent pancreatic ductal adenocarcinoma metastasis to the liver in mice

Liver Metastasis in Cancer: Molecular Mechanisms and Management

Liver metastasis is a leading cause of mortality from malignant tumors and significantly impairs the efficacy of therapeutic interventions. In recent years, both preclinical and clinical research have made significant progress in understanding the molecular mechanisms and therapeutic strategies of liver metastasis. Metastatic tumor cells from different primary sites undergo highly similar biological processes, ultimately achieving ectopic colonization and growth in the liver. In this review, we begin by introducing the inherent metastatic-friendly features of the liver. We then explore the panorama of liver metastasis and conclude the three continuous, yet distinct phases based on the liver's response to metastasis. This includes metastatic sensing stage, metastatic stress stage, and metastasis support stage. We discuss the intricate interactions between metastatic tumor cells and various resident and recruited cells. In addition, we emphasize the critical role of spatial remodeling of immune cells in liver metastasis. Finally, we review the recent advancements and the challenges faced in the clinical management of liver metastasis. Future precise antimetastatic treatments should fully consider individual heterogeneity and implement different targeted interventions based on stages of liver metastasis.

Vascular-Associated Mononuclear Phagocytes: First-Line Soldiers Ambushing Metastasis

Mononuclear phagocytes (MPs), which consist of dendritic cells, monocytes, and macrophages, are distributed throughout the body and actively eliminate invading microorganisms and abnormal cells. Depending on the local microenvironment, MPs manifest considerably various lifespans and phenotypes to maintain tissue homeostasis. Vascular-associated mononuclear phagocytes (VaMPs) are the special subsets of MPs that are localized either within the lumen side or on the apical surface of vessels, acting as the critical sentinels to recognize and defend against disseminated tumor cells. In this review, we introduce three major types of VaMPs, patrolling monocytes, Kupffer cells, and perivascular macrophages, and discuss their emerging roles in immunosurveillance during incipient metastasis. We also explore the roles of lineage-determining transcription factors and cell surface receptors that endow VaMPs with potent anti-tumor activity. Finally, we highlight the molecular and cellular mechanisms that drive the phenotypic plasticity of VaMPs and summarize combinatory strategies for targeting VaMPs in overt metastasis.

Stachydrine targeting tumor-associated macrophages inhibit colorectal cancer liver metastasis by regulating the JAK2/STAT3 pathway

Introduction

Colorectal cancer (CRC) represents the third most prevalent form of cancer worldwide, with liver metastasis representing a significant contributor to mortality. The interaction between tumor-associated macrophages (TAMs) and tumor cells plays a pivotal role in the development of colorectal cancer liver metastases (CRLM) and represents a promising avenue for therapeutic intervention. Stachydrine (STA), a compound derived from the Leonurus heterophyllus plant, has been shown to effectively inhibit tumor growth through a range of mechanisms.

Methods

The study employed imaging and histopathology to evaluate the efficacy of STA monotherapy in preventing CRLM. The inhibition of M2 macrophage polarization by STA was confirmed through the use of flow cytometry and immunofluorescence. Subsequently, a series of assays, including quantitative reverse transcription polymerase chain reaction (qRT-PCR), flow cytometry, scratch, invasion, and tube formation assays, were conducted to confirm STA's capacity to impede tumor cell migration, invasion, and angiogenesis in vitro. Western blotting and flow cytometry were employed to elucidate the mechanisms through which STA exerts its effects on tumor metastasis.

Results

In our research, STA has been shown to attenuate liver metastasis in CRC mouse models by inhibiting the polarization of macrophages to the M2 phenotype. This anti-metastatic effect is dependent on the presence of macrophages. In vitro, STA has been found to impede tumor cell migration, invasion, and angiogenesis by preventing TAMs from polarizing to the M2 phenotype via the JAK2/STAT3 signaling pathway. Moreover, the combination of STA with anti-PD-1 therapy has been observed to restore immune infiltration within the tumor microenvironment and inhibit tumor progression.

Conclusion

The findings of this study demonstrate that STA exerts an inhibitory effect on colorectal cancer liver metastasis by targeting macrophages and impeding their M2 polarization via the JAK2/STAT3 pathway. Furthermore, the combination of STA with anti-PD-1 therapy has been observed to enhance the effectiveness of immune checkpoint blockade and reduce tumor spread, indicating the potential of STA to improve the efficacy of immunotherapy for liver metastases.

Navigating liver cancer: Precision targeting for enhanced treatment outcomes

Cancer treatments such as surgery and chemotherapy have several limitations, including ineffectiveness against large or persistent tumors, high relapse rates, drug toxicity, and non-specificity of therapy. Researchers are exploring advanced strategies for treating this life-threatening disease to address these challenges. One promising approach is targeted drug delivery using prodrugs or surface modification with receptor-specific moieties for active or passive targeting. While various drug delivery systems have shown potential for reaching hepatic cells, nano-carriers offer significant size, distribution, and targetability advantages. Engineered nanocarriers can be customized to achieve effective and safe targeting of tumors by manipulating physical characteristics such as particle size or attaching receptor-specific ligands. This method is particularly advantageous in treating liver cancer by targeting specific hepatocyte receptors and enzymatic pathways for both passive and active therapeutic strategies. It highlights the epidemiology of liver cancer and provides an in-depth analysis of the various targeting approaches, including prodrugs, liposomes, magneto-liposomes, micelles, glycol-dendrimers, magnetic nanoparticles, chylomicron-based emulsion, and quantum dots surface modification with receptor-specific moieties. The insights from this review can be immensely significant for preclinical and clinical researchers working towards developing effective treatments for liver cancer. By utilizing these novel strategies, we can overcome the limitations of conventional therapies and offer better outcomes for liver cancer patients.

Tissue-resident immune cells: from defining characteristics to roles in diseases

Tissue-resident immune cells (TRICs) are a highly heterogeneous and plastic subpopulation of immune cells that reside in lymphoid or peripheral tissues without recirculation. These cells are endowed with notably distinct capabilities, setting them apart from their circulating leukocyte counterparts. Many studies demonstrate their complex roles in both health and disease, involving the regulation of homeostasis, protection, and destruction. The advancement of tissue-resolution technologies, such as single-cell sequencing and spatiotemporal omics, provides deeper insights into the cell morphology, characteristic markers, and dynamic transcriptional profiles of TRICs. Currently, the reported TRIC population includes tissue-resident T cells, tissue-resident memory B (BRM) cells, tissue-resident innate lymphocytes, tissue-resident macrophages, tissue-resident neutrophils (TRNs), and tissue-resident mast cells, but unignorably the existence of TRNs is controversial. Previous studies focus on one of them in specific tissues or diseases, however, the origins, developmental trajectories, and intercellular cross-talks of every TRIC type are not fully summarized. In addition, a systemic overview of TRICs in disease progression and the development of parallel therapeutic strategies is lacking. Here, we describe the development and function characteristics of all TRIC types and their major roles in health and diseases. We shed light on how to harness TRICs to offer new therapeutic targets and present burning questions in this field.

Smad2 Cooperating with TGIF2 Contributes to EMT and Cancer Stem Cells Properties in Pancreatic Cancer via Co-Targeting SOX2

The underlying mechanisms between cancer stem cells (CSC) and epithelial-mesenchymal transition (EMT) in pancreatic cancer (PC) remain unclear. In this study, we identified TGIF2 as a target gene of CSC using sncRNA and machine learning. TGIF2 is closely related to the expression of SOX2, EGFR, and E-cadherin, indicating poor prognosis. Mechanistically, TGIF2 promoted the EMT phenotype and CSC properties following the activation of SOX2, Slug, CD44, and ERGF/MAPK signaling, which were rescued by SOX2 silencing. TGIF2 silencing contributes to the opposite phenotype via SOX2. Notably, Smad2 cooperates with TGIF2 to co-regulate the SOX2 promoter, which in turn promotes EMT and CSC signaling by transactivating Slug and EGFR, respectively. The transactivation of EGFR/MAPK signaling by SOX2 promotes TGIF2 nuclear translocation, forming a positive feedback loop in vitro. Moreover, the interaction of TGIF2 and SOX2 with EGFR inhibitors promoted subcutaneous tumors and liver metastasis in vivo. Thus, the TGIF2/SOX2 axis contributes to CSC, EMT, and chemoresistance, providing a promising target for PC therapy.

Adaptor protein 3BP2 regulates gene expression in addition to the ubiquitination and proteolytic activity of MALT1 in dectin-1-stimulated cells

Dectin-1, a C-type lectin, plays important roles in the induction of antifungal immunity. Caspase recruitment domain-containing protein 9 (CARD9) is essential for the dectin-1-induced production of cytokines through the activation of NF-κB. However, the molecular mechanisms underlying the dectin-1-mediated activation of CARD9 have not been fully elucidated. Recently, we reported that the adaptor protein SH3 domain-binding protein 2 (3BP2) is required for the dectin-1-induced production of cytokines and activation of NF-κB, although the relationship between 3BP2 and CARD9 in dectin-1-mediated signaling remains unclear. Here, we report that 3BP2 is required for dectin-1-induced expression of several genes that may contribute to antifungal immunity in bone marrow-derived dendritic cells (BMDCs). The results of reporter assays using HEK-293T cells indicate that 3BP2 induces CARD9-mediated activation of NF-κB through B-cell leukemia/lymphoma 10, mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1), and TNF receptor-associated factor 6-dependent mechanisms. In addition, we show that 3BP2 induces CARD9-mediated ubiquitination of cellular proteins and that MALT1 cleaves 3BP2 in a CARD9-dependent manner. Furthermore, we show that 3BP2 is required for the ubiquitination, in addition to the activation, of MALT1, which leads to MALT1-depenedent cleavage of 3BP2 in dectin-1-stimulated BMDCs. Finally, we identified hematopoietic cell-specific Lyn substrate 1 as a target of 3BP2, which is essential for dectin-1-induced expression of interleukin 10 in BMDCs. These results indicate that 3BP2 regulates gene expression and functions of MALT1 in dectin-1-stimulated cells and that 3BP2 plays an important role in the dectin-1-mediated antifungal immunity.

Alternations in inflammatory macrophage niche drive phenotypic and functional plasticity of Kupffer cells

Inflammatory signals lead to recruitment of circulating monocytes and induce their differentiation into pro-inflammatory macrophages. Therefore, whether blocking inflammatory monocytes can mitigate disease progression is being actively evaluated. Here, we employ multiple lineage-tracing models and show that monocyte-derived macrophages (mo-mac) are the major population of immunosuppressive, liver metastasis-associated macrophages (LMAM), while the proportion of Kupffer cells (KC) as liver-resident macrophages is diminished in metastatic nodules. Paradoxically, genetic ablation of mo-macs results in only a marginal decrease in LMAMs. Using a proliferation-recording system and a KC-tracing model in a monocyte-deficient background, we find that LMAMs can be replenished either via increased local macrophage proliferation or by promoting KC infiltration. In the latter regard, KCs undergo transient proliferation and exhibit substantial phenotypic and functional alterations through epigenetic reprogramming following the vacating of macrophage niches by monocyte depletion. Our data thus suggest that a simultaneous blockade of monocyte recruitment and macrophage proliferation may effectively target immunosuppressive myelopoiesis and reprogram the microenvironment towards an immunostimulatory state.

Establishment of a Transplantation Model of PDAC-Derived Liver Metastases

BACKGROUND

The highly metastatic nature of pancreatic ductal adenocarcinoma (PDAC) and the difficulty to achieve favorable patient outcomes emphasize the need for novel therapeutic solutions. For preclinical evaluations, genetically engineered mouse models are often used to mimic human PDAC but frequently fail to replicate synchronous development and metastatic spread. This study aimed to develop a transplantation model to achieve synchronous and homogenous PDAC growth with controlled metastatic patterns in the liver.

METHODS

To generate an orthotopic PDAC model, the DT6606 cell line was injected into the pancreas head of C57BL/6 mice, and their survival was monitored over time. To generate a heterotopic transplantation model, growing doses of three PDAC cell lines (DT6606, DT6606lm, and K8484) were injected into the portal vein of mice. Magnetic resonance imaging (MRI) was used to monitor metastatic progression, and histologic analysis was performed.

RESULTS

Orthotopically injected mice succumbed to the tumor within an 11-week period (average survival time, 78.2 ± 4.45 days). Post-mortem examinations failed to identify liver metastasis. In the intraportal model, 2 × 105 DT6606 cells resulted in an absence of liver metastases by day 21, whereas 5 × 104 DT6606lm cells and 7 × 104 K8484 cells resulted in steady metastatic growth. Higher doses caused significant metastatic liver involvement. The use of K8484 cells ensured the growth of tumors closely resembling the histopathologic characteristics of human PDAC.

CONCLUSIONS

This report details the authors' efforts to establish an "optimal" murine model for inducing metastatic PDAC, which is critical for advancing our understanding of the disease and developing more effective treatments.

The Role of Myeloid Cells on the Development of Hepatic Metastases in Gastrointestinal Cancer

The development of hepatic metastases is the leading cause of mortality in gastrointestinal (GI) cancers and substantial research efforts have been focused on elucidating the intricate mechanisms by which tumor cells successfully migrate to, invade, and ultimately colonize the liver parenchyma. Recent evidence has shown that perturbations in myeloid biology occur early in cancer development, characterized by the initial expansion of specific innate immune populations that promote tumor growth and facilitate metastases. This review summarizes the pathophysiology underlying the proliferation of myeloid cells that occurs with incipient neoplasia and explores the role of innate immune-host interactions, specifically granulocytes and neutrophil extracellular traps, in promoting hepatic colonization by tumor cells through the formation of the "premetastatic niche". We further summarize the role of additional myeloid subpopulations such as monocytes and macrophages, dendritic cells, platelets, and eosinophils on promoting disease metastases in GI cancers. Lastly, we describe burgeoning therapeutic approaches aimed at targeting specific myeloid populations to reduce liver metastases and highlight the inherent challenges that exist in studying the efficacy of these treatments in preclinical models. As the inception and outgrowth of liver metastases are primary drivers of prognosis in GI malignancies; further research into the complex mechanisms involved in this critical process is urgently needed.

The Role of Human and Animal Monocytes and Macrophages in Homeostasis and Disease

Monocytes and macrophages are the innate immune cells that are the first-line responders to invading pathogens or foreign objects[...].