The lymph node pre-metastatic niche

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.

Mechanisms of lymph node metastasis: An extracellular vesicle perspective

In several solid tumors such as breast cancer, prostate cancer, colorectal cancer or melanoma, tumor draining lymph nodes are the earliest tissues where colonization by tumor cells is detected. Lymph nodes act as sentinels of metastatic dissemination, the deadliest phase of tumor progression. Besides hematogenous dissemination, lymphatic spread of tumor cells has been demonstrated, adding more complexity to the mechanisms involved in metastasis. A network of blood and lymphatic vessels surrounds tumors providing routes for tumor soluble factors to mediate regional and long-distance effects. Additionally, extracellular vesicles (EVs), particularly small EVs/exosomes, have been shown to circulate through the blood and lymph, favoring the formation of pre-metastatic niches in the tumor-draining lymph nodes (TDLNs) and distant organs. In this review, we present an overview of the relevance of lymph node metastasis, the structural and immune changes occurring in TDLNs during tumor progression, and how extracellular vesicles contribute to modulating some of these alterations while promoting the formation of lymph node pre-metastatic niches.

Intra-patient spatial comparison of non-metastatic and metastatic lymph nodes reveals the reduction of CD169+ macrophages by metastatic breast cancers

BACKGROUND

Breast cancer cells suppress the host immune system to efficiently invade the lymph nodes; however, the underlying mechanism remains incompletely understood. Here, we aimed to comprehensively characterise the effects of breast cancers on immune cells in the lymph nodes.

METHODS

We collected non-metastatic and metastatic lymph node samples from 6 patients with breast cancer with lymph node metastasis. We performed bulk transcriptomics, spatial transcriptomics, and imaging mass cytometry to analyse the obtained lymph nodes. Furthermore, we conducted histological analyses against a larger patient cohort (474 slices from 58 patients).

FINDINGS

The comparison between paired lymph nodes with and without metastasis from the same patients demonstrated that the number of CD169+ lymph node sinus macrophages, an initiator of anti-cancer immunity, was reduced in metastatic lymph nodes (36.7 ± 21.1 vs 7.3 ± 7.0 cells/mm2, p = 0.0087), whereas the numbers of other major immune cell types were unaltered. We also detected that the infiltration of CD169+ macrophages into metastasised cancer tissues differed by section location within tumours, suggesting that CD169+ macrophages were gradually decreased after anti-cancer reactions. Furthermore, CD169+ macrophage elimination was prevalent in major breast cancer subtypes and correlated with breast cancer staging (p = 0.022).

INTERPRETATION

We concluded that lymph nodes with breast cancer metastases have fewer CD169+ macrophages, which may be detrimental to the activity of anti-cancer immunity.

FUNDING

JSPS KAKENHI (16H06279, 20H03451, 20H04842, 22H04925, 19K16770, and 21K15530, 24K02236), JSPS Fellows (JP22KJ1822), AMED (JP21ck0106698), JST FOREST (JPMJFR2062), Caravel, Co., Ltd, Japan Foundation for Applied Enzymology, and Sumitomo Pharma Co., Ltd. under SKIPS.

Immune responses and immunotherapeutic approaches in the treatment against cancer

Cancer cells within a population are heterogeneous due to genomic mutations or epigenetic changes. The immune response to cancer especially the T cell repertoire within the cancer microenvionment is important to the control and growth of cancer cells. When a cancer clone breaks through the surveillance of the immune system, it wins the battle to overcome the host's immune system. In this review, the complicated profile of the cancer microenvironment is emphasized. The molecular evidence of immune responses to cancer has been recently established. Based on these molecular mechanisms of immune interactions with cancer, clinical trials based on checkpoint inhibition therapy against CTLA-4 and/or PD-1 versus PD-L1 have been successful in the treatment of melanoma, lung cancer and other types of cancer. The diversity of the T cell repertoire is described and the tumor infiltrating lymphocytes within the cancer may be expanded ex vivo and infused back to the patient as a treatment modality for adoptive immunotherapy.

Urinary extracellular vesicle-derived miR-126-3p predicts lymph node invasion in patients with high-risk prostate cancer

To investigate extracellular vesicles (EVs), biomarkers for predicting lymph node invasion (LNI) in patients with high-risk prostate cancer (HRPCa), plasma, and/or urine samples were prospectively collected from 45 patients with prostate cancer (PCa) and five with benign prostatic hyperplasia (BPH). Small RNA sequencing was performed to identify miRNAs in the EVs. All patients with PCa underwent radical prostatectomy and extended pelvic lymph node dissection. Differentially expressed miRNAs were identified in patients with and without pathologically-verified LNI. The candidate miRNAs were validated in low-risk prostate cancer (LRPCa) and BPH. Four miRNA species (e.g., miR-126-3p) and three miRNA species (e.g., miR-27a-3p) were more abundant in urinary and plasma EVs, respectively, of patients with PCa. None of these miRNA species were shared between urinary and plasma EVs. miR-126-3p was significantly more abundant in patients with HR PCa with LNI than in those without (P = 0.018). miR-126-3p was significantly more abundant in the urinary EVs of patients with HRPCa than in those with LRPCa (P = 0.017) and BPH (P = 0.011). In conclusion, urinary EVs-derived miR-126-3p may serve as a good biomarker for predicting LNI in patients with HRPCa.

Urinary extracellular vesicle-derived miR-126-3p predicts lymph node invasion in patients with high-risk prostate cancer

To investigate extracellular vesicles (EVs) biomarkers for predicting lymph node invasion (LNI) in patients with high-risk prostate cancer (HRPCa), plasma and/or urine samples were prospectively collected from 45 patients with prostate cancer (PCa) and five with benign prostatic hyperplasia (BPH). Small RNA sequencing was performed to identify miRNAs in the EVs. All patients with PCa underwent radical prostatectomy and extended pelvic lymph node dissection. Differentially-expressed miRNAs were identified in patients with and without pathologically-verified LNI. The candidate miRNAs were validated in low-risk prostate cancer (LRPCa) and BPH. Four miRNA species (e.g. miR-126-3p) and three miRNA species (e.g. miR-27a-3p) were more abundant in urinary and plasma EVs, respectively, of patients with PCa. None of these miRNA species were shared between urinary and plasma EVs. miR-126-3p was significantly more abundant in patients with HR PCa with LNI than in those without (P = 0.018). miR-126-3p was significantly more abundant in the urinary EVs of patients with HRPCa than in those with LRPCa (P = 0.017) and BPH (P = 0.011). In conclusion, urinary EVs-derived miR-126-3p may serve as a good biomarker for predicting LNI in patients with HRPCa.

New insights into the correlations between circulating tumor cells and target organ metastasis

Organ-specific metastasis is the primary cause of cancer patient death. The distant metastasis of tumor cells to specific organs depends on both the intrinsic characteristics of the tumor cells and extrinsic factors in their microenvironment. During an intermediate stage of metastasis, circulating tumor cells (CTCs) are released into the bloodstream from primary and metastatic tumors. CTCs harboring aggressive or metastatic features can extravasate to remote sites for continuous colonizing growth, leading to further lesions. In the past decade, numerous studies demonstrated that CTCs exhibited huge clinical value including predicting distant metastasis, assessing prognosis and monitoring treatment response et al. Furthermore, increasingly numerous experiments are dedicated to identifying the key molecules on or inside CTCs and exploring how they mediate CTC-related organ-specific metastasis. Based on the above molecules, more and more inhibitors are being developed to target CTCs and being utilized to completely clean CTCs, which should provide promising prospects to administer advanced tumor. Recently, the application of various nanomaterials and microfluidic technologies in CTCs enrichment technology has assisted to improve our deep insights into the phenotypic characteristics and biological functions of CTCs as a potential therapy target, which may pave the way for us to make practical clinical strategies. In the present review, we mainly focus on the role of CTCs being involved in targeted organ metastasis, especially the latest molecular mechanism research and clinical intervention strategies related to CTCs.

Small Extracellular Vesicles Derived from Helicobacter Pylori-Infected Gastric Cancer Cells Induce Lymphangiogenesis and Lymphatic Remodeling via Transfer of miR-1246

Lymph node metastasis (LNM) is a significant barrier to the prognosis of patients with gastric cancer (GC). Helicobacter pylori (H. pylori)-positive GC patients experience a higher rate of LNM than H. pylori-negative GC patients. However, the underlying mechanism remains unclear. Based on the findings of this study, H. pylori-positive GC patients have greater lymphangiogenesis and lymph node immunosuppression than H. pylori-negative GC patients. In addition, miR-1246 is overexpressed in the plasma small extracellular vesicles (sEVs) of H. pylori-positive GC patients, indicating a poor prognosis. Functionally, sEVs derived from GC cells infected with H. pylori deliver miR-1246 to lymphatic endothelial cells (LECs) and promote lymphangiogenesis and lymphatic remodeling. Mechanistically, miR-1246 suppresses GSK3β expression and promotes β-Catenin and downstream MMP7 expression in LECs. miR-1246 also stabilizes programmed death ligand-1 (PD-L1) by suppressing GSK3β and induces the apoptosis of CD8+ T cells. Overall, miR-1246 in plasma sEVs may be a novel biomarker and therapeutic target in GC-LNM.

Unraveling temporal and spatial biomarkers of epithelial-mesenchymal transition in colorectal cancer: insights into the crucial role of immunosuppressive cells

The occurrence and progression of tumors can be established through a complex interplay among tumor cells undergoing epithelial-mesenchymal transition (EMT), invasive factors and immune cells. In this study, we employed single-cell RNA sequencing (scRNA-seq) and spatially resolved transcriptomics (ST) to evaluate the pseudotime trajectory and spatial interactive relationship between EMT-invasive malignant tumors and immune cells in primary colorectal cancer (CRC) tissues at different stages (stage I/II and stage III with tumor deposit). Our research characterized the spatiotemporal relationship among different invasive tumor programs by constructing pseudotime endpoint-EMT-invasion tumor programs (EMTPs) located at the edge of ST, utilizing evolution trajectory analysis integrated with EMT-invasion genes. Strikingly, the invasive and expansive process of tumors undergoes remarkable spatial reprogramming of regulatory and immunosuppressive cells, such as myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages (TAMs), regulatory T cells (Treg), and exhausted T cells (Tex). These EMTP-adjacent cell are linked to EMT-related invasion genes, especially the C-X-C motif ligand 1 (CXCL1) and CXCL8 genes that are important for CRC prognosis. Interestingly, the EMTPs in stage I mainly produce an inflammatory margin invasive niche, while the EMTPs in stage III tissues likely produce a hypoxic pre-invasive niche. Our data demonstrate the crucial role of regulatory and immunosuppressive cells in tumor formation and progression of CRC. This study provides a framework to delineate the spatiotemporal invasive niche in CRC samples.

Immunomodulatory properties of the lymphatic endothelium in the tumor microenvironment

The tumor microenvironment (TME) is an intricate complex and dynamic structure composed of various cell types, including tumor, stromal and immune cells. Within this complex network, lymphatic endothelial cells (LECs) play a crucial role in regulating immune responses and influencing tumor progression and metastatic dissemination to lymph node and distant organs. Interestingly, LECs possess unique immunomodulatory properties that can either promote or inhibit anti-tumor immune responses. In fact, tumor-associated lymphangiogenesis can facilitate tumor cell dissemination and metastasis supporting immunoevasion, but also, different molecular mechanisms involved in LEC-mediated anti-tumor immunity have been already described. In this context, the crosstalk between cancer cells, LECs and immune cells and how this communication can shape the immune landscape in the TME is gaining increased interest in recent years. In this review, we present a comprehensive and updated report about the immunomodulatory properties of the lymphatic endothelium within the TME, with special focus on primary tumors and tumor-draining lymph nodes. Furthermore, we outline emerging research investigating the potential therapeutic strategies targeting the lymphatic endothelium to enhance anti-tumor immune responses. Understanding the intricate mechanisms involved in LEC-mediated immune modulation in the TME opens up new possibilities for the development of innovative approaches to fight cancer.

Unraveling the Role of EV-Derived miR-150-5p in Prostate Cancer Metastasis and Its Association with High-Grade Gleason Scores: Implications for Diagnosis

Metastasis remains the leading cause of mortality in prostate cancer patients. The presence of tumor cells in lymph nodes is an established prognostic indicator for several cancer types, such as melanoma, breast, oral, pancreatic, and cervical cancers. Emerging evidence highlights the role of microRNAs enclosed within extracellular vesicles as facilitators of molecular communication between tumors and metastatic sites in the lymph nodes. This study aims to investigate the potential diagnostic utility of EV-derived microRNAs in liquid biopsies for prostate cancer. By employing microarrays on paraffin-embedded samples, we characterized the microRNA expression profiles in metastatic lymph nodes, non-metastatic lymph nodes, and primary tumor tissues of prostate cancer. Differential expression of microRNAs was observed in metastatic lymph nodes compared to prostate tumors and non-metastatic lymph node tissues. Three microRNAs (miR-140-3p, miR-150-5p, and miR-23b-3p) were identified as differentially expressed between tissue and plasma samples. Furthermore, we evaluated the expression of these microRNAs in exosomes derived from prostate cancer cells and plasma samples. Intriguingly, high Gleason score samples exhibited the lowest expression of miR-150-5p compared to control samples. Pathway analysis suggested a potential regulatory role for miR-150-5p in the Wnt pathway and bone metastasis. Our findings suggest EV-derived miR-150-5p as a promising diagnostic marker for identifying patients with high-grade Gleason scores and detecting metastasis at an early stage.

Clathrin light chain A-enriched small extracellular vesicles remodel microvascular niche to induce hepatocellular carcinoma metastasis

Small extracellular vesicles (sEVs) play a key role in exchanging cargoes between cells in tumour microenvironment. This study aimed to elucidate the functions and mechanisms of hepatocellular carcinoma (HCC) derived sEV-clathrin light chain A (CLTA) in remodelling microvascular niche. CLTA level in the circulating sEVs of HCC patients was analysed by enzyme-linked immunosorbent assay (ELISA). The functions of sEV-CLTA in affecting HCC cancerous properties were examined by multiple functional assays. Mass spectrometry was used to identify downstream effectors of sEV-CLTA in human umbilical vein endothelial cells (HUVECs). Tube formation, sprouting, trans-endothelial invasion and vascular leakiness assays were performed to determine the functions of sEV-CLTA and its effector, basigin (BSG) in HUVECs. BSG inhibitor, SP-8356, was tested in a mouse model of patient-derived xenografts (PDXs). Circulating sEVs of HCC patients had markedly enhanced CLTA levels than control individuals and were reduced in patients after surgery. HCC derived sEV-CLTA enhanced HCC cancerous properties, disrupted endothelial integrity and induced angiogenesis. Mechanistically, CLTA remodels microvascular niche by stabilizing and upregulating BSG. Last, SP-8356 alone or in combination with sorafenib attenuated PDXs growth. The study reveals the role of HCC derived sEV-CLTA in microvascular niche formation. Inhibition of CLTA and its mediated pathway may illuminate a new therapeutic strategy for HCC patients.

Increased levels of PD1 and glycolysis in CD4+ T cells are positively associated with lymph node metastasis in OSCC

BACKGROUND

Cervical lymph node metastasis is one of the poorest prognostic factors in oral squamous cell carcinoma (OSCC). Activated immune cells generally have metabolic abnormalities in the tumour microenvironment. However, it is unknown whether abnormal glycolysis in T cells could facilitate metastatic lymph nodes in OSCC patients. The aim of this study was to investigate the effects of immune checkpoints in metastatic lymph nodes and determine the correlation between glycolysis and immune checkpoint expression in CD4⁺ T cells.

METHODS

Flow cytometry and immunofluorescence staining were used to analyse the differences in CD4⁺ PD1⁺ T cells between metastatic lymph nodes (LN⁺) and negative lymph nodes (LN^-). RT‒PCR was performed to detail the expression of immune checkpoints and glycolysis-related enzymes in LN⁺ and LN^-.

RESULTS

The frequency of CD4⁺ T cells decreased in LN⁺ patients (p = 0.0019). The PD1 expression of LN⁺ increased markedly compared to that of LN^- (p = 0.0205). Similarly, the PD1 of CD4⁺ T cells in LN⁺ increased significantly compared to that of LN^-. Additionally, glycolysis-related enzyme levels in CD4⁺ T cells from LN⁺ patients were dramatically higher than those in LN^- patients. PD1 and Hk2 expression in CD4⁺ T cells was also increased in LN⁺ OSCC patients with prior surgical treatment compared to those without.

CONCLUSIONS

These findings suggest that lymph node metastasis and recurrence in OSCC are associated with increases in PD1 and glycolysis in CD4⁺ T cells; this response may serve as a potential regulator of OSCC progression.

Implications of the Organ-Specific Immune Environment for Immune Priming Effect of Radiotherapy in Metastatic Setting

With the development of immune checkpoint inhibitors (ICIs), the tumour immune microenvironment (TIME) has been increasingly considered to improve cancer management. The TIME of metastatic lesions is strongly influenced by the underlying immune contexture of the organ in which they are located. The metastatic location itself appears to be an important prognostic factor in predicting outcomes after ICI treatment in cancer patients. Patients with liver metastases are less likely to respond to ICIs than patients with metastases in other organs, likely due to variations in the metastatic TIME. Combining additional treatment modalities is an option to overcome this resistance. Radiotherapy (RT) and ICIs have been investigated together as an option to treat various metastatic cancers. RT can induce a local and systemic immune reaction, which can promote the patient's response to ICIs. Here, we review the differential impact of the TIME according to metastatic location. We also explore how RT-induced TIME modifications could be modulated to improve outcomes of RT-ICI combinations.

A TMVP1-modified near-infrared nanoprobe: molecular imaging for tumor metastasis in sentinel lymph node and targeted enhanced photothermal therapy

BACKGROUND

TMVP1 is a novel tumor targeting polypeptide screened by our laboratory with a core sequence of five amino acids LARGR. It specially binds to vascular endothelial growth factor receptor-3 (VEGFR-3), which is mainly expressed on neo-lymphatic vessels in sentinel lymph node (SLN) with tumor metastasis in adults. Here, we prepared a targeted nanoprobe using TMVP1-modified nanomaterials for tumor metastasis SLN imaging.

RESULTS

In this study, TMVP1-modified polymer nanomaterials were loaded with the near-infrared (NIR) fluorescent dye, indocyanine green (ICG), to prepare a molecular imaging TMVP1-ICG nanoparticles (NPs) to identify tumor metastasis in SLN at molecular level. TMVP1-ICG-NPs were successfully prepared using the nano-precipitation method. The particle diameter, morphology, drug encapsulation efficiency, UV absorption spectrum, cytotoxicity, safety, and pharmacokinetic properties were determined. The TMVP1-ICG-NPs had a diameter of approximately 130 nm and an ICG loading rate of 70%. In vitro cell experiments and in vivo mouse experiments confirmed that TMVP1-ICG-NPs have good targeting ability to tumors in situ and to SLN with tumor metastasis by binding to VEGFR-3. Effective photothermal therapy (PTT) with TMVP1-ICG-NPs was confirmed in vitro and in vivo. As expected, TMVP1-ICG-NPs improved ICG blood stability, targeted tumor metastasis to SLN, and enhanced PTT/photodynamic (PDT) therapy, without obvious cytotoxicity, making it a promising theranostic nanomedicine.

CONCLUSION

TMVP1-ICG-NPs identified SLN with tumor metastasis and were used to perform imaging-guided PTT, which makes it a promising strategy for providing real-time NIR fluorescence imaging and intraoperative PTT for patients with SLN metastasis.

Examined lymph node count for gastric cancer patients after curative surgery

Lymph node (LN) metastasis is the most common form of metastasis in gastric cancer (GC). The status and stage of LN metastasis are important indicators that reflect the progress of GC. The number of LN metastases is still the most effective index to evaluate the prognosis of patients in all stages of LN metastasis. Examined LN (ELN) count refers to the number of LNs harvested from specimens by curative gastrectomy for pathological examination. This review summarizes the factors that influence ELN count, including individual and tumor factors, intraoperative dissection factors, postoperative sorting factors, and pathological examination factors. Different ELN counts will lead to prognosis-related stage migration. Fine LN sorting and regional LN sorting are the two most important LN sorting technologies. The most direct and effective way to harvest a large number of LNs is for surgeons to perform in vitro fine LN sorting.

Polysaccharides of Plantago asiatica enhance antitumor activity via regulating macrophages to M1-like phenotype

Monocyte-derived macrophages can be polarized into antitumor M1 phenotype, which inhibited the growth of tumors, and immune-suppressive M2 phenotype, which promoted the development and metastasis of tumors. Plantain polysaccharide (PLP), extracted from the Plantago asiatica, has shown its various biological activities. However, the ability of PLP involved in immune regulation was still obscure. Accordingly, we aimed to investigate whether PLP could polarize macrophages and further inhibit 4T1 tumor cells in vivo and in vitro. In this research, in vitro results showed that PLP displayed the potential in polarizing RAW264.7 macrophages into M1 phenotype and indirect inhibiting migratory effect on 4T1 cells. Furthermore, the phagocytosis and the release of reactive oxygen species (ROS) of macrophages were enhanced. In vivo anti-tumor results demonstrated that PLP could effectively inhibit the growth of 4T1 breast tumors by promoting accumulation of macrophages and T cells in the spleen and lymph node. In conclusion, these findings indicated that PLP inhibited the proliferation and progression of breast tumors by accumulating CD4⁺, CD8⁺ T cells and M1-like macrophages in lymph node and spleen, and therefore provided an experimental basis for PLP as a potential antitumor adjunctive therapy in preclinical and clinical trials.

Extracellular vesicles and melanoma: New perspectives on tumor microenvironment and metastasis

Secreted extracellular vesicles (EVs) are lipid bilayer particles without functional nucleus naturally released from cells which constitute an intercellular communication system. There is a broad spectrum of vesicles shed by cells based on their physical properties such as size (small EVs and large EVs), biogenesis, cargo and functions, which provide an increasingly heterogenous landscape. In addition, they are involved in multiple physiological and pathological processes. In cancer, EV release is opted by tumor cells as a beneficial process for tumor progression. Cutaneous melanoma is a cancer that originates from the melanocyte lineage and shows a favorable prognosis at early stages. However, when melanoma cells acquire invasive capacity, it constitutes the most aggressive and deadly skin cancer. In this context, extracellular vesicles have been shown their relevance in facilitating melanoma progression through the modulation of the microenvironment and metastatic spreading. In agreement with the melanosome secretory capacity of melanocytes, melanoma cells display an enhanced EV shedding activity that has contributed to the utility of melanoma models for unravelling EV cargo and functions within a cancer scenario. In this review, we provide an in-depth overview of the characteristics of melanoma-derived EVs and their role in melanoma progression highlighting key advances and remaining open questions in the field.

Tagging the pre-metastatic node in oral cancer: A cross-sectional study

INTRODUCTION

Lymph node involvement is the first indication of spread of oral squamous cell carcinoma (OSCC) and it is also a most significant prognostic factor. Lymph nodes show various tumor-induced histological changes preceding actual metastasis, viz. increased vascularity, follicular hyperplasia and desmoplasia which leads to pre-metastatic niche formation. This pre-metastatic niche primarily provides a favorable microenvironment to for the survival and subsequent growth of cancer cells within the lymph node.

AIM

A retrospective study to evaluate carcinoma-induced changes in lymph nodes harvested from radical neck dissection in OSCC patients.

OBJECTIVES

1) To evaluate cancer-induced histological changes in positive and negative lymph nodes in OSCC patients. 2) To look for common histopathological changes in both pre-metastatic and metastatic lymph nodes.

MATERIALS AND METHODS

Forty lymph nodes harvested from seven OSCC patients were sectioned and stained (Hematoxylin-Eosin) for documentation of histologically evident morphological and functional alterations. The Chi-square test was applied between the non-metastatic and metastatic lymph nodes findings and a statistically significant difference was seen.

RESULTS

Sections from 28 negative nodes showed changes associated with pre-metastatic niche conditioning whereas, 12 sections exhibit frank metastases.

CONCLUSION

The modified immunological responses and remodeling of the vasculature are the most common histologic tumor-induced pre-metastatic changes. This study reviewed and categorized these histological changes that point to pre-metastatic niche conditioning of lymph nodes.

The metastatic niche formation: focus on extracellular vesicle-mediated dialogue between lung cancer cells and the microenvironment

Lung cancer is the deadliest cancer in the world, with the majority of patients presenting with advanced or metastatic disease at first diagnosis. The lungs are also one of the most common sites of metastasis from lung cancer and other tumors. Understanding the mechanisms that regulate metastasis formation from primary lung cancer and in the lungs is therefore fundamental unmet clinical need. One of the first steps during the establishment of lung cancer metastases includes the formation of the pre-metastatic niche (PMN) at distant organs, which may occur even during the early phases of cancer development. The PMN is established through intricate cross-talk between primary tumor-secreted factors and stromal components at distant sites. Mechanisms controlling primary tumor escape and seeding of distant organs rely on specific properties of tumor cells but are also tightly regulated by interactions with stromal cells at the metastatic niche that finally dictate the success of metastasis establishment. Here, we summarize the mechanisms underlying pre-metastatic niche formation starting from how lung primary tumor cells modulate distant sites through the release of several factors, focusing on Extracellular Vesicles (EVs). In this context, we highlight the role of lung cancer-derived EVs in the modulation of tumor immune escape. Then, we illustrate the complexity of Circulating Tumor Cells (CTCs) that represent the seeds of metastasis and how interactions with stromal and immune cells can help their metastatic dissemination. Finally, we evaluate the contribution of EVs in dictating metastasis development at the PMN through stimulation of proliferation and control of disseminated tumor cell dormancy. Overall, we present an overview of different steps in the lung cancer metastatic cascade, focusing on the EV-mediated interactions between tumor cells and stromal/immune cells.

Naming the Barriers between Anti-CCR5 Therapy, Breast Cancer and Its Microenvironment

Breast cancer represents the most common malignancy among women in the world. Although immuno-, chemo- and radiation therapy are widely recognized as the therapeutic trifecta, new strategies in the fight against breast cancer are continually explored. The local microenvironment around the tumor plays a great role in cancer progression and invasion, representing a promising therapeutic target. CCL5 is a potent chemokine with a physiological role of immune cell attraction and has gained particular attention in R&D for breast cancer treatment. Its receptor, CCR5, is a well-known co-factor for HIV entry through the cell membrane. Interestingly, biology research is unusually unified in describing CCL5 as a pro-oncogenic factor, especially in breast cancer. In silico, in vitro and in vivo studies blocking the CCL5/CCR5 axis show cancer cells become less invasive and less malignant, and the extracellular matrices produced are less oncogenic. At present, CCR5 blocking is a mainstay of HIV treatment, but despite its promising role in cancer treatment, CCR5 blocking in breast cancer remains unperformed. This review presents the role of the CCL5/CCR5 axis and its effector mechanisms, and names the most prominent hurdles for the clinical adoption of anti-CCR5 drugs in cancer.

Reprogramming of sentinel lymph node microenvironment during tumor metastasis

Metastasis is a major cause of death in patients with cancer. The two main routes for cancer cell dissemination are the blood and lymphatic systems. The underlying mechanism of hematogenous metastasis has been well characterized in the past few decades. However, our understanding of the molecular basis of lymphatic metastasis remains at a premature stage. Conceptually, cancer cells invade into lymphatic capillary, passively move to collecting lymphatic vessels, migrate into sentinel lymph node (SLN;, the first lymph node to which cancer cells spread from the primary tumor), and enter the blood circulatory system via the subclavian vein. Before arriving, cancer cells release specific soluble factors to modulate the microenvironment in SLN to establish a beachhead for successful colonization. After colonization, cancer cells inhibit anti-tumor immunity by inducing the recruitment of regulatory T cell and myeloid-derived suppressor cells, suppressing the function of dendritic cell and CD8⁺ T cell, and promoting the release of immunosuppressive cytokines. The development of novel strategies to reverse cancer cell-triggered SLN remodeling may re-activate immunity to reduce beachhead buildup and distant metastasis. In addition to being a microanatomic location for metastasis, the SLN is also an important site for immune modulation. Nanotechnology-based approaches to deliver lymph node-tropic antibodies or drug-conjugated nanoparticles to kill cancer cells on site are a new direction for cancer treatment. Conversely, the induction of stronger immunity by promoting antigen presentation in lymph nodes provides an alternate way to enhance the efficacy of immune checkpoint therapy and cancer vaccine. In this review article, we summarize recent findings on the reprogramming of SLN during lymphatic invasion and discuss the possibility of inhibiting tumor metastasis and eliciting anti-tumor immunity by targeting SLN.

Applications of machine learning in tumor-associated macrophages

Evaluation of tumor-host interaction and intratumoral heterogeneity in the tumor microenvironment (TME) is gaining increasing attention in modern cancer therapies because it can reveal unique information about the tumor status. As tumor-associated macrophages (TAMs) are the major immune cells infiltrating in TME, a better understanding of TAMs could help us further elucidate the cellular and molecular mechanisms responsible for cancer development. However, the high-dimensional and heterogeneous data in biology limit the extensive integrative analysis of cancer research. Machine learning algorithms are particularly suitable for oncology data analysis due to their flexibility and scalability to analyze diverse data types and strong computation power to learn underlying patterns from massive data sets. With the application of machine learning in analyzing TME, especially TAM’s traceable status, we could better understand the role of TAMs in tumor biology. Furthermore, we envision that the promotion of machine learning in this field could revolutionize tumor diagnosis, treatment stratification, and survival predictions in cancer research. In this article, we described key terms and concepts of machine learning, reviewed the applications of common methods in TAMs, and highlighted the challenges and future direction for TAMs in machine learning.

Lymphatic vessels in cancer

The lymphatic system, composed of initial and collecting lymphatic vessels as well as lymph nodes that are present in almost every tissue of the human body, acts as an essential transport system for fluids, biomolecules and cells between peripheral tissues and the central circulation. Consequently, it is required for normal body physiology but is also involved in the pathogenesis of various diseases, most notably cancer. The important role of tumor-associated lymphatic vessels and lymphangiogenesis in the formation of lymph node metastasis has been elucidated during the last two decades, whereas the underlying mechanisms and the relation between lymphatic and peripheral organ dissemination of cancer cells are incompletely understood. Lymphatic vessels are also important for tumor-host communication, relaying molecular information from a primary or metastatic tumor to regional lymph nodes and the circulatory system. Beyond antigen transport, lymphatic endothelial cells, particularly those residing in lymph node sinuses, have recently been recognized as direct regulators of tumor immunity and immunotherapy responsiveness, presenting tumor antigens and expressing several immune-modulatory signals including PD-L1. In this review, we summarize recent discoveries in this rapidly evolving field and highlight strategies and challenges of therapeutic targeting of lymphatic vessels or specific lymphatic functions in cancer patients.

The Regulation of Lymph Node Pre-Metastatic Niche Formation in Head and Neck Squamous Cell Carcinoma

In many distinct forms of malignancies, there is a close relationship between lymph node (LN) metastases and further dissemination to distant organs, and this is a critical prognostic factor. At the beginning of the process, the original tumor secretes soluble substances or releases extracellular vesicles (EVs) that are carried through lymphatic channels to draining (sentinel) LN. The tumor-derived factors then drive LN remodeling. These significant alterations occur prior to the emergence of the first metastatic cell, bringing about the development of a pre-metastatic niche that allows metastatic cells to survive and thrive. In this review, we discuss current information available about the regulation of lymph node pre-metastatic niche in head and neck squamous cell carcinoma (HNSCC), and the role of EVs in forming the pre-metastatic niche.

CD73 in small extracellular vesicles derived from HNSCC defines tumour-associated immunosuppression mediated by macrophages in the microenvironment

Research on tumour cell‐derived small extracellular vesicles (sEVs) that regulate tumour microenvironment (TME) has provided strategies for targeted therapy of head and neck squamous cell carcinoma (HNSCC). Herein, we demonstrated that sEVs derived from HNSCC cancer cells carried CD73 (sEVs^CD73), which promoted malignant progression and mediated immune evasion. The sEVs^CD73 phagocytosed by tumour‐associated macrophages (TAMs) in the TME induced immunosuppression. Higher CD73^high TAMs infiltration levels in the HNSCC microenvironment were correlated with poorer prognosis, while sEVs^CD73 activated the NF‐κB pathway in TAMs, thereby inhibiting immune function by increasing cytokines secretion such as IL‐6, IL‐10, TNF‐α, and TGF‐β1. The absence of sEVs^CD73 enhanced the sensitivity of anti‐PD‐1 therapy through reversed immunosuppression. Moreover, circulating sEVs^CD73 increased the risk of lymph node metastasis and worse prognosis. Taken together, our study suggests that sEVs^CD73 derived from tumour cells contributes to immunosuppression and is a potential predictor of anti‐PD‐1 responses for immune checkpoint therapy in HNSCC.

Potential key roles of tumour budding: a representative malignant pathological feature of non-small cell lung cancer and a sensitive indicator of prognosis

OBJECTIVES

To investigate the relationship between tumour budding, clinicopathological characteristics of patients and prognosis in non-small cell lung cancer.

STUDY DESIGN

A retrospective study was used.

PARTICIPANTS

We selected 532 patients with non-small cell lung cancer from China, including 380 patients with adenocarcinoma and 152 with squamous cell carcinoma.

PRIMARY AND SECONDARY OUTCOME MEASURES

Tumour budding was visible using H&E staining as well as pancytokeratin staining. The count data and measurement data were compared using the χ² test and the t-test, respectively. The overall survival rate was the follow-up result. The survival curves were drawn using the Kaplan-Meier method, and the differences between groups were analysed using the log-rank method. The independent prognostic factor of patients with lung cancer was determined using a multivariate Cox proportional hazard model.

RESULTS

In patients with lung adenocarcinoma, there was a correlation between tumour budding and spread through air spaces (OR 36.698; 95% CI 13.925 to 96.715; p<0.001), and in patients with squamous cell carcinoma, tumour budding state was closely related to the peritumoural space (OR 11.667; 95% CI 4.041 to 33.683; p<0.001). On Cox regression analysis, multivariate analysis showed that tumour budding, pleural and vascular invasion, spread through air spaces, tumour size, lymph node metastasis, and tumour node metastasis stage were independent risk factors of prognosis for patients with non-small cell lung cancer.

CONCLUSIONS

As an effective and simple pathological diagnostic index, it is necessary to establish an effective grading system in the clinical diagnosis of lung cancer to verify the value of tumour budding as a prognostic indicator. We hope that this analysis of Chinese patients with non-small cell lung cancer can provide useful reference material for the continued study of tumour budding.

Innate lymphoid cells: NK and cytotoxic ILC3 subsets infiltrate metastatic breast cancer lymph nodes

Innate lymphoid cells (ILCs) – which include cytotoxic Natural Killer (NK) cells and helper-type ILC – are important regulators of tissue immune homeostasis, with possible roles in tumor surveillance. We analyzed ILC and their functionality in human lymph nodes (LN). In LN, NK cells and ILC3 were the prominent subpopulations. Among the ILC3s, we identified a CD56⁺/ILC3 subset with a phenotype close to ILC3 but also expressing cytotoxicity genes shared with NK. In tumor-draining LNs (TD-LNs) and tumor samples from breast cancer (BC) patients, NK cells were prominent, and proportions of ILC3 subsets were low. In tumors and TD-LN, NK cells display reduced levels of NCR (Natural cytotoxicity receptors), despite high transcript levels and included a small subset CD127⁻ CD56⁻ NK cells with reduced function. Activated by cytokines CD56⁺/ILC3 cells from donor and patients LN acquired cytotoxic capacity and produced IFNg. In TD-LN, all cytokine activated ILC populations produced TNFα in response to BC cell line. Analyses of cytotoxic and helper ILC indicate a switch toward NK cells in TD-LN. The local tumor microenvironment inhibited NK cell functions through downregulation of NCR, but cytokine stimulation restored their functionality.

In Vitro, In Vivo, and In Silico Models of Lymphangiogenesis in Solid Malignancies

Lymphangiogenesis (LA) is the formation of new lymphatic vessels by lymphatic endothelial cells (LECs) sprouting from pre-existing lymphatic vessels. It is increasingly recognized as being involved in many diseases, such as in cancer and secondary lymphedema, which most often results from cancer treatments. For some cancers, excessive LA is associated with cancer progression and metastatic dissemination to the lymph nodes (LNs) through lymphatic vessels. The study of LA through in vitro, in vivo, and, more recently, in silico models is of paramount importance in providing novel insights and identifying the key molecular actors in the biological dysregulation of this process under pathological conditions. In this review, the different biological (in vitro and in vivo) models of LA, especially in a cancer context, are explained and discussed, highlighting their principal modeled features as well as their advantages and drawbacks. Imaging techniques of the lymphatics, complementary or even essential to in vivo models, are also clarified and allow the establishment of the link with computational approaches. In silico models are introduced, theoretically described, and illustrated with examples specific to the lymphatic system and the LA. Together, these models constitute a toolbox allowing the LA research to be brought to the next level.

The Impact of Obesity, Adipose Tissue, and Tumor Microenvironment on Macrophage Polarization and Metastasis

Tumor metastasis is a major cause of death in cancer patients. It involves not only the intrinsic alterations within tumor cells, but also crosstalk between these cells and components of the tumor microenvironment (TME). Tumorigenesis is a complex and dynamic process, involving the following three main stages: initiation, progression, and metastasis. The transition between these stages depends on the changes within the extracellular matrix (ECM), in which tumor and stromal cells reside. This matrix, under the effect of growth factors, cytokines, and adipokines, can be morphologically altered, degraded, or reorganized. Many cancers evolve to form an immunosuppressive TME locally and create a pre-metastatic niche in other tissue sites. TME and pre-metastatic niches include myofibroblasts, immuno-inflammatory cells (macrophages), adipocytes, blood, and lymphatic vascular networks. Several studies have highlighted the adipocyte-macrophage interaction as a key driver of cancer progression and dissemination. The following two main classes of macrophages are distinguished: M1 (pro-inflammatory/anti-tumor) and M2 (anti-inflammatory/pro-tumor). These cells exhibit distinct microenvironment-dependent phenotypes that can promote or inhibit metastasis. On the other hand, obesity in cancer patients has been linked to a poor prognosis. In this regard, tumor-associated adipocytes modulate TME through the secretion of inflammatory mediators, which modulate and recruit tumor-associated macrophages (TAM). Hereby, this review describes the cellular and molecular mechanisms that link inflammation, obesity, and cancer. It provides a comprehensive overview of adipocytes and macrophages in the ECM as they control cancer initiation, progression, and invasion. In addition, it addresses the mechanisms of tumor anchoring and recruitment for M1, M2, and TAM macrophages, specifically highlighting their origin, classification, polarization, and regulatory networks, as well as their roles in the regulation of angiogenesis, invasion, metastasis, and immunosuppression, specifically highlighting the role of adipocytes in this process.

Melanoma-derived extracellular vesicles mediate lymphatic remodelling and impair tumour immunity in draining lymph nodes

Tumour-draining lymph nodes (LNs) undergo massive remodelling including expansion of the lymphatic sinuses, a process that has been linked to lymphatic metastasis by creation of a pre-metastatic niche. However, the signals leading to these changes have not been completely understood. Here, we found that extracellular vesicles (EVs) derived from melanoma cells are rapidly transported by lymphatic vessels to draining LNs, where they selectively interact with lymphatic endothelial cells (LECs) as well as medullary sinus macrophages. Interestingly, uptake of melanoma EVs by LN-resident LECs was partly dependent on lymphatic VCAM-1 expression, and induced transcriptional changes as well as proliferation of those cells. Furthermore, melanoma EVs shuttled tumour antigens to LN LECs for cross-presentation on MHC-I, resulting in apoptosis induction in antigen-specific CD8+ T cells. In conclusion, our data identify EV-mediated melanoma-LN LEC communication as a new pathway involved in tumour progression and tumour immune inhibition, suggesting that EV uptake or effector mechanisms in LECs might represent a new target for melanoma therapy.

Melanoma-derived small extracellular vesicles induce lymphangiogenesis and metastasis through an NGFR-dependent mechanism

Secreted extracellular vesicles (EVs) influence the tumor microenvironment and promote distal metastasis. Here, we analyzed the involvement of melanoma-secreted EVs in lymph node pre-metastatic niche formation in murine models. We found that small EVs (sEVs) derived from metastatic melanoma cell lines were enriched in nerve growth factor receptor (NGFR, p75NTR), spread through the lymphatic system and were taken up by lymphatic endothelial cells, reinforcing lymph node metastasis. Remarkably, sEVs enhanced lymphangiogenesis and tumor cell adhesion by inducing ERK kinase, nuclear factor (NF)-κB activation and intracellular adhesion molecule (ICAM)-1 expression in lymphatic endothelial cells. Importantly, ablation or inhibition of NGFR in sEVs reversed the lymphangiogenic phenotype, decreased lymph node metastasis and extended survival in pre-clinical models. Furthermore, NGFR expression was augmented in human lymph node metastases relative to that in matched primary tumors, and the frequency of NGFR⁺ metastatic melanoma cells in lymph nodes correlated with patient survival. In summary, we found that NGFR is secreted in melanoma-derived sEVs, reinforcing lymph node pre-metastatic niche formation and metastasis.

68Ga-FAPI-04 vs. 18F-FDG in a longitudinal preclinical PET imaging of metastatic breast cancer

PURPOSE

This longitudinal study aims to evaluate the performance of 68 Ga-FAPI-04 and 18F-FDG and to profile the dynamic process of tumor metastasis in a preclinical 4T1 breast cancer model. Although both of these two radioligands are wildly used in clinic, no study was reported on their performance in the longitudinal monitoring of tumor metastasis. Also, no correlation between the expression level of fibroblast activation protein (FAP) and the development of tumor metastasis has been elucidated previously. In this study, we evaluated the performance of 68 Ga-FAPI-04 and 18F-FDG PET during the entire process of tumor metastasis, and their potential for the early diagnosis of tumor metastasis. We also clarified the correlation of uptakes as well as the signal-to-background (S/B) ratios between these two probes at different stages of tumor metastasis.

METHODS

Forty 4T1 metastatic breast cancer murine models were established using female BALB/c mice, followed by the longitudinal imaging with 68 Ga-FAPI-04 and 18F-FDG once a week for up to 6 weeks. In vitro hematoxylin and eosin (H&E) and immunochemistry (IHE) staining were performed to evaluate FAP expression on the metastatic lesions. Further statistical analysis was performed to evaluate the correlation of 68 Ga-FAPI-04 and 18F-FDG uptake (%ID/cc) at different stages of the metastasis.

RESULTS

68 Ga-FPAI-04 holds an advantage over 18F-FDG with higher sensitivity at the early stage of tumor metastasis. However, with the progress of tumor metastasis, uptake of 68 Ga-FAPI-04 decreases and becomes less sensitive than 18F-FDG. There is also no direct correlation between uptake or S/B ratios of 68 Ga-FAPI-04 and 18F-FDG during this dynamic process.

CONCLUSION

68 Ga-FAPI-04 is more sensitive than 18F-FDG in detecting the early stage of tumor metastasis, but becomes less sensitive than 18F-FDG at the late stage of tumor metastasis. We envision this result would be meaningful for the explanation of the 68 Ga-FAPI-04 and 18F-FDG imaging both in the future clinic and preclinic studies.

Interaction Between Modern Radiotherapy and Immunotherapy for Metastatic Prostate Cancer

Prostate cancer is the most frequently diagnosed cancer in men and a leading cause of cancer-related death. In recent decades, the development of immunotherapies has resulted in great promise to cure metastatic disease. However, prostate cancer has failed to show any significant response, presumably due to its immunosuppressive microenvironment. There is therefore growing interest in combining immunotherapy with other therapies able to relieve the immunosuppressive microenvironment. Radiation therapy remains the mainstay treatment for prostate cancer patients, is known to exhibit immunomodulatory effects, depending on the dose, and is a potent inducer of immunogenic tumor cell death. Optimal doses of radiotherapy are thus expected to unleash the full potential of immunotherapy, improving primary target destruction with further hope of inducing immune-cell-mediated elimination of metastases at distance from the irradiated site. In this review, we summarize the current knowledge on both the tumor immune microenvironment in prostate cancer and the effects of radiotherapy on it, as well as on the use of immunotherapy. In addition, we discuss the utility to combine immunotherapy and radiotherapy to treat oligometastatic metastatic prostate cancer.

Exosomes in the Tumor Microenvironment: From Biology to Clinical Applications

Cancer is one of the most important health problems and the second leading cause of death worldwide. Despite the advances in oncology, cancer heterogeneity remains challenging to therapeutics. This is because the exosome-mediated crosstalk between cancer and non-cancer cells within the tumor microenvironment (TME) contributes to the acquisition of all hallmarks of cancer and leads to the formation of cancer stem cells (CSCs), which exhibit resistance to a range of anticancer drugs. Thus, this review aims to summarize the role of TME-derived exosomes in cancer biology and explore the clinical potential of mesenchymal stem-cell-derived exosomes as a cancer treatment, discussing future prospects of cell-free therapy for cancer treatment and challenges to be overcome.

Role of Extracellular Vesicles on Cancer Lymphangiogenesis and Lymph Node Metastasis

Lymph node metastasis (LNM) of tumors is an established indicator of poor prognosis in patients. Tumor-associated lymphangiogenesis is a key step in LNM and has gained much attention. However, currently, there is no anti-tumor lymphangiogenesis drug used in clinical practice. Recently, studies on extracellular vesicles (EVs) have shown that different types of cells in the tumor microenvironment can release EVs that encapsulate a variety of molecules, including proteins, nucleic acids, and metabolites. Lymph endothelial cells (LECs) regulate tumor lymphangiogenesis through the uptake of EVs packed with different biologically active contents. In this review, we will discuss the possible mechanisms by which EVs participate in the regulation of tumor-associated lymphangiogenesis and LNM, summarize the potential value of EVs that can be used as biomarkers for the determination of tumor LNM, and indicate the potential anti-tumor lymphangiogenesis therapy.

Current concepts of ectopic nodal inclusions with special emphasis on nodal nevi

Nodal inclusions of ectopic tissue within lymph nodes are seen comparatively often in dermatopathology and general pathology. Glandular and nonglandular epithelium, as well as melanocytic nevi can be observed within lymph nodes and represent mostly incidental findings without any relevance. The main challenge in reporting these morphologic features is to differentiate such benign inclusions from metastatic settlements of distinct organ tumors. As sentinel node biopsy and lymph node dissection have become standard procedure in clinical oncology and have an immense clinical impact, the correct evaluation of these nodal inclusions is indispensable to avoid undertreatment or overtreatment of patients. In addition, the genesis of these inclusions has not yet been satisfactorily clarified. Two concepts have been laid out: the theory of benign metastases and the migration arrest theory. However, neither theory has so far been able to answer the following questions: Why do we find more nodal nevi in patients with melanoma who had a sentinel node biopsy than in patients without melanoma, and why do we not find nodal nevi in deep visceral lymph nodes? We present a comprehensive review of the current knowledge on nodal inclusions, proposing a concept for the pathogenesis of nodal nevi, to answer these questions.

Physiological models for in vivo imaging and targeting the lymphatic system: Nanoparticles and extracellular vesicles

Imaging of the lymphatic vasculature has gained great attention in various fields, not only because lymphatic vessels act as a key draining system in the body, but also for their implication in autoimmune diseases, organ transplant, inflammation and cancer. Thus, neolymphangiogenesis, or the generation of new lymphatics, is typically an early event in the development of multiple tumor types, particularly in aggressive ones such as malignant melanoma. Still, the understanding of how lymphatic endothelial cells get activated at distal (pre)metastatic niches and their impact on therapy is still unclear. Addressing these questions is of particular interest in the case of immune modulators, because endothelial cells may favor or halt inflammatory processes depending on the cellular context. Therefore, there is great interest in visualizing the lymphatic vasculature in vivo. Here, we review imaging tools and mouse models used to analyze the lymphatic vasculature during tumor progression. We also discuss therapeutic approaches based on nanomedicines to target the lymphatic system and the potential use of extracellular vesicles to track and target sentinel lymph nodes. Finally, we summarize main pre-clinical models developed to visualize the lymphatic vasculature in vivo, discussing their applications with a particular focus in metastatic melanoma.

JUNB suppresses distant metastasis by influencing the initial metastatic stage

The complex interactions between cells of the tumor microenvironment and cancer cells are considered a major determinant of cancer progression and metastasis. Yet, our understanding of the mechanisms of metastatic disease is not sufficient to successfully treat patients with advanced-stage cancer. JUNB is a member of the AP-1 transcription factor family shown to be frequently deregulated in human cancer and associated with invasion and metastasis. A strikingly high stromal JUNB expression in human breast cancer samples prompted us to functionally investigate the consequences of JUNB loss in cells of the tumor microenvironment on cancer progression and metastasis in mice. To adequately mimic the clinical situation, we applied a syngeneic spontaneous breast cancer metastasis model followed by primary tumor resection and identified stromal JUNB as a potent suppressor of distant metastasis. Comprehensive characterization of the JUNB-deficient tumor microenvironment revealed a strong influx of myeloid cells into primary breast tumors and lungs at early metastatic stage. In these infiltrating neutrophils, BV8 and MMP9, proteins promoting angiogenesis and tissue remodeling, were specifically upregulated in a JUNB-dependent manner. Taken together, we established stromal JUNB as a strong suppressor of distant metastasis. Consequently, therapeutic strategies targeting AP-1 should be carefully designed not to interfere with stromal JUNB expression as this may be detrimental for cancer patients.

Tumor Immune Microenvironment Characterization of Primary Lung Adenocarcinoma and Lymph Node Metastases

Background

The essential roles of the tumor microenvironment (TME) have been recognized during the initiation and progression of primary lung adenocarcinoma (LUAD). The aim of the present study was to delineate the immune landscape in both primary cancer and matched lymph node metastasis from a cohort of locally advanced stage LUAD patients with distinct outcomes.

Methods

Formalin-fixed, paraffin-embedded samples were collected from 36 locally advanced LUAD patients. Transcriptome data of the tumor immune microenvironment were resolved using an immune oncology panel RNA sequencing platform. Bioinformatics approaches were used to determine the differentially expressed genes (DEGs), dysregulated pathways, and immune cell fraction between patients with early recurrence (ER) and late recurrence (LR).

Results

Here, we showed that in primary cancer tissues, 23 DEGs were obtained between patients with ER and LR. Functional analysis revealed that the LR in LUAD patients may be associated with enriched gene sets belonging to the antigen presentation and MHC protein complex, innate immune response, and IFN-γ signaling pathways. Next, the transcriptome data were adopted to quantify immune cell fractions, indicating that high infiltration of mast cells and neutrophils was correlated with ER. Interestingly, similar findings were observed in metastatic lymph nodes from patients suffering from ER or LR. By analyzing the shared immune features of primary cancers and lymphatic metastases, we unraveled the prognostic value and joint utility of two DEGs, CORO1A and S100A8.

Conclusions

In LUAD, the enrichment in antigen presentation, MHC protein complex, and IFN-γ signaling, and low infiltration of neutrophils in primary or metastatic nodules may be indications for a favorable prognosis. Integrated with bioinformatics approaches, transcriptome data of immune-related genes from formalin-fixed, paraffin-embedded (FFPE) samples can effectively profile the landscape of the tumor immune microenvironment and help predict clinical outcomes.

Inactivation of EMILIN-1 by Proteolysis and Secretion in Small Extracellular Vesicles Favors Melanoma Progression and Metastasis

Several studies have demonstrated that melanoma-derived extracellular vesicles (EVs) are involved in lymph node metastasis; however, the molecular mechanisms involved are not completely defined. Here, we found that EMILIN-1 is proteolyzed and secreted in small EVs (sEVs) as a novel mechanism to reduce its intracellular levels favoring metastasis in mouse melanoma lymph node metastatic cells. Interestingly, we observed that EMILIN-1 has intrinsic tumor and metastasis suppressive-like properties reducing effective migration, cell viability, primary tumor growth, and metastasis. Overall, our analysis suggests that the inactivation of EMILIN-1 by proteolysis and secretion in sEVs reduce its intrinsic tumor suppressive activities in melanoma favoring tumor progression and metastasis.

The pre-metastatic niche in lymph nodes: formation and characteristics

Lymph node metastasis is a crucial prognostic parameter in many different types of cancers and a gateway for further dissemination to distant organs. Prior to metastatic dissemination, the primary tumor prepares for the remodeling of the draining (sentinel) lymph node by secreting soluble factors or releasing extracellular vesicles that are transported by lymphatic vessels. These important changes occur before the appearance of the first metastatic cell and create what is known as a pre-metastatic niche giving rise to the subsequent survival and growth of metastatic cells. In this review, the lymph node structure, matrix composition and the emerging heterogeneity of cells forming it are described. Current knowledge of the major cellular and molecular processes associated with nodal pre-metastatic niche formation, including lymphangiogenesis, extracellular matrix remodeling, and immunosuppressive cell enlisting in lymph nodes are additionally summarized. Finally, future directions that research could possibly take and the clinical impact are discussed.

Fatty acid oxidation: driver of lymph node metastasis

Fatty acid oxidation (FAO) is the emerging hallmark of cancer metabolism because certain tumor cells preferentially utilize fatty acids for energy. Lymph node metastasis, the most common way of tumor metastasis, is much indispensable for grasping tumor progression, formulating therapy measure and evaluating tumor prognosis. There is a plethora of studies showing different ways how tumor cells metastasize to the lymph nodes, but the role of FAO in lymph node metastasis remains largely unknown. Here, we summarize recent findings and update the current understanding that FAO may enable lymph node metastasis formation. Afterward, it will open innovative possibilities to present a distinct therapy of targeting FAO, the metabolic rewiring of cancer to terminal cancer patients.

Correlation of microRNA-367 in the clinicopathologic features and prognosis of breast cancer patients

Breast cancer (BC) is a malignant tumor originating from cells of the breast. Notably, microRNAs have been recognized as biomarkers of BC metastasis. The present study is designed to evaluate the association between microRNA (miR)-367 expression and BC with the variance of clinicopathologic features and prognosis.Initially, 63 BC patients were allocated in the BC group, while the other 40 healthy volunteers were recruited as the control group. miR-367 expression in the serum of patients and healthy controls was detected using real-time polymerase chain reaction. Furthermore, the relation between miR-367 in serum and clinicopathologic features and prognosis of BC patients was accessed.miR-367 expression in serum of the BC group was evidently lower than that in the control group (all P < .001). Besides, miR-367 underexpression in the BC group was closely associated with the variance in tumor nodes metastasis advanced stage, tumor diameter, and lymph node metastasis of BC (all P < .001). In addition, compared with the control group, poorly expressed miR-367 BC group had short period of disease-free survival and overall survival (all P < .001).Our study demonstrated that miR-367 expression is associated with BC clinicopathologic features and prognosis. This investigation may offer new insight for BC treatment.

A Circular RNA, Cholangiocarcinoma-Associated Circular RNA 1, Contributes to Cholangiocarcinoma Progression, Induces Angiogenesis, and Disrupts Vascular Endothelial Barriers

BACKGROUND AND AIMS

Circular RNAs (circRNAs) and extracellular vesicles (EVs) are involved in various malignancies. We aimed to clarify the functions and mechanisms of dysregulated circRNAs in the cells and EVs of cholangiocarcinoma (CCA).

APPROACH AND RESULTS

CircRNA microarray was used to identify circRNA expression profiles in CCA tissues and bile-derived EVs (BEVs). CCA-associated circRNA 1 (circ-CCAC1) expression was measured by quantitative real-time PCR. The clinical importance of circ-CCAC1 was analyzed by receiver operating characteristic curves, Fisher's exact test, Kaplan-Meier plots, and Cox regression model. The functions of circ-CCAC1 and exosomal circ-CCAC1 were explored in CCA cells and human umbilical vein endothelial cells (HUVECs), respectively. Different animal models were used to verify the in vitro results. RNA sequencing, bioinformatics, RNA immunoprecipitation, RNA pulldown, chromatin immunoprecipitation followed by sequencing, and luciferase reporter assays were used to determine the regulatory networks of circ-CCAC1 in CCA cells and HUVECs. Circ-CCAC1 levels were increased in cancerous bile-resident EVs and tissues. The diagnostic and prognostic values of circ-CCAC1 were identified in patients with CCA. For CCA cells, circ-CCAC1 increased cell progression by sponging miR-514a-5p to up-regulate Yin Yang 1 (YY1). Meanwhile, YY1 directly bound to the promoter of calcium modulating ligand to activate its transcription. Moreover, circ-CCAC1 from CCA-derived EVs was transferred to endothelial monolayer cells, disrupting endothelial barrier integrity and inducing angiogenesis. Mechanistically, circ-CCAC1 increased cell leakiness by sequestering enhancer of zeste homolog 2 in the cytoplasm, thus elevating SH3 domain-containing GRB2-like protein 2 expression to reduce the levels of intercellular junction proteins. In vivo studies further showed that increased circ-CCAC1 levels in circulating EVs and cells accelerated both CCA tumorigenesis and metastasis.

CONCLUSIONS

Circ-CCAC1 plays a vital role in CCA tumorigenesis and metastasis and may be an important biomarker/therapeutic target for CCA.

Exosomal integrins and their influence on pancreatic cancer progression and metastasis

As one of the most lethal and untreatable types of cancer so far, pancreatic cancer is not benefitting from advancements in research. Despite all the efforts, this malignancy is still very difficult to diagnose in time, resistant to treatments, and prone to relapses. The appearance of metastasis-notoriously difficult to fight and a signal of unfortunate prognosis-is the event most dreaded by every cancer patient, especially by those with pancreatic cancer. Strategies for early detection and treatment of metastases are limited, and new action plans are desperately awaited. Recently, the importance of cell-secreted vesicles, or exosomes, in cell-cell communication and, particularly, their key role in promoting pathological conditions, such as infectious diseases and cancer, have attracted the attention of the scientific community. The discovery of some exosome membrane components, such as adhesion receptors and integrins, and their ability to influence cancer cell functions and metastasis progression, has added some important understanding of the metastatic process and will hopefully open the door to the development of new tools for identifying and targeting metastases. The aim of this review is to discuss the role played by integrins in exosomal-mediated pancreatic cancer progression and metastasis.

Heterogeneity in Signaling Pathway Activity within Primary and between Primary and Metastatic Breast Cancer

Targeted therapy aims to block tumor-driving signaling pathways and is generally based on analysis of one primary tumor (PT) biopsy. Tumor heterogeneity within PT and between PT and metastatic breast lesions may, however, impact the effect of a chosen therapy. Whereas studies are available that investigate genetic heterogeneity, we present results on phenotypic heterogeneity by analyzing the variation in the functional activity of signal transduction pathways, using an earlier developed platform to measure such activity from mRNA measurements of pathways' direct target genes. Statistical analysis comparing macro-scale variation in pathway activity on up to five spatially distributed PT tissue blocks (n = 35), to micro-scale variation in activity on four adjacent samples of a single PT tissue block (n = 17), showed that macro-scale variation was not larger than micro-scale variation, except possibly for the PI3K pathway. Simulations using a "checkerboard clone-size" model showed that multiple small clones could explain the higher micro-scale variation in activity found for the TGFβ and Hedgehog pathways, and that intermediate/large clones could explain the possibly higher macro-scale variation of the PI3K pathway. While within PT, pathway activities presented a highly positive correlation, correlations weakened between PT and lymph node metastases (n = 9), becoming even worse for PT and distant metastases (n = 9), including a negative correlation for the ER pathway. While analysis of multiple sub-samples of a single biopsy may be sufficient to predict PT response to targeted therapies, metastatic breast cancer treatment prediction requires analysis of metastatic biopsies. Our findings on phenotypic intra-tumor heterogeneity are compatible with emerging ideas on a Big Bang type of cancer evolution in which macro-scale heterogeneity appears not dominant.

Progression of Metastasis through Lymphatic System

Lymph nodes are the most common sites of metastasis in cancer patients. Nodal disease status provides great prognostic power, but how lymph node metastases should be treated is under debate. Thus, it is important to understand the mechanisms by which lymph node metastases progress and how they can be targeted to provide therapeutic benefits. In this review, we focus on delineating the process of cancer cell migration to and through lymphatic vessels, survival in draining lymph nodes and further spread to other distant organs. In addition, emerging molecular targets and potential strategies to inhibit lymph node metastasis are discussed.