Extralymphatic tumors prepare draining lymph nodes to invasion via a T-cell cross-tolerance process

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.

Ex vivo model of breast cancer cell invasion in live lymph node tissue

Lymph nodes (LNs) are common sites of metastatic invasion in breast cancer, often preceding spread to distant organs and serving as key indicators of clinical disease progression. However, the mechanisms of cancer cell invasion into LNs are not well understood. Existing in vivo models struggle to isolate the specific impacts of the tumor-draining lymph node (TDLN) milieu on cancer cell invasion due to the co-evolving relationship between TDLNs and the upstream tumor. To address these limitations, we used live ex vivo LN tissue slices with intact chemotactic function to model cancer cell spread within a spatially organized microenvironment. After showing that BRPKp110 breast cancer cells were chemoattracted to factors secreted by naïve LN tissue in a 3D migration assay, we demonstrated that ex vivo LN slices could support cancer cell seeding, invasion, and spread. This novel approach revealed dynamic, preferential cancer cell invasion within specific anatomical regions of LNs, particularly the subcapsular sinus (SCS) and cortex, as well as chemokine-rich domains of immobilized CXCL13 and CCL1. While CXCR5 was necessary for a portion of BRPKp110 invasion into naïve LNs, disruption of CXCR5/CXCL13 signaling alone was insufficient to prevent invasion towards CXCL13-rich domains. Finally, we extended this system to pre-metastatic TDLNs, where the ex vivo model predicted a lower invasion of cancer cells. The reduced invasion was not due to diminished chemokine secretion, but it correlated with elevated intranodal IL-21. In summary, this innovative ex vivo model of cancer cell spread in live LN slices provides a platform to investigate cancer invasion within the intricate tissue microenvironment, supporting time-course analysis and parallel read-outs. We anticipate that this system will enable further research into cancer-immune interactions and allow isolation of specific factors that make TDLNs resistant to cancer cell invasion, which are challenging to dissect in vivo.

B Cells and IL-21-Producing Follicular Helper T Cells Cooperate to Determine the Dynamic Alterations of Premetastatic Tumor Draining Lymph Nodes of Breast Cancer

Metastasis is the major cause of cancer-related death, and lymph node is the most common site of metastasis in breast cancer. However, the alterations that happen in tumor-draining lymph nodes (TDLNs) to form a premetastatic microenvironment are largely unknown. Here, we first report the dynamic changes in size and immune status of TDLNs before metastasis in breast cancer. With the progression of tumor, the TDLN is first enlarged and immune-activated at early stage that contains specific antitumor immunity against metastasis. The TDLN is then contracted and immunosuppressed at late stage before finally getting metastasized. Mechanistically, B and follicular helper T (Tfh) cells parallelly expand and contract to determine the size of TDLN. The activation status and specific antitumor immunity of CD8+ T cells in the TDLN are determined by interleukin-21 (IL-21) produced by Tfh cells, thus showing parallel changes. The turn from activated enlargement to suppressed contraction is due to the spontaneous contraction of germinal centers mediated by follicular regulatory T cells. On the basis of the B-Tfh-IL-21-CD8+ T cell axis, we prove that targeting the axis could activate TDLNs to resist metastasis. Together, our findings identify the dynamic alterations and regulatory mechanisms of premetastatic TDLNs of breast cancer and provide new strategies to inhibit lymph node metastasis.

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.

Lymph node metastasis and tumor-educated immune tolerance: Potential therapeutic targets against distant metastasis

Lymph node metastasis has been shown to positively associated with the prognosis of many cancers. However, in clinical treatment, lymphadenectomy is not always successful, suggesting that immune cells in the tumor and sentinel lymph nodes still play a pivotal role in tumor immunosuppression. Recent studies had shown that tumors can tolerate immune cells through multiple strategies, including tumor-induced macrophage reprogramming, T cells inactivation, production of B cells pathogenic antibodies and activation of regulatory T cells to promote tumor colonization, growth, and metastasis in lymph nodes. We reviewed the bidirectional effect of immune cells on anti-tumor or promotion of cancer cell metastasis during lymph node metastasis, and the mechanisms by which malignant cancer cells modify immune cells to create a more favorable environment for the growth and survival of cancer cells. Research and treatment strategies focusing on the immune system in lymph nodes and potential immune targets in lymph node metastasis were also be discussed.

Adding liposomal doxorubicin enhances the abscopal effect induced by radiation/αPD1 therapy depending on tumor cell mitochondrial DNA and cGAS/STING

BACKGROUND

Localized radiotherapy (RT) can cause a T cell-mediated abscopal effect on non-irradiated tumor lesions, especially in combination with immune checkpoint blockade. However, this effect is still clinically rare and improvements are highly desirable. We investigated whether triple combination with a low dose of clinically approved liposomal doxorubicin (Doxil) could augment abscopal responses compared with RT/αPD-1 and Doxil/αPD-1. We also investigated whether the enhanced abscopal responses depended on the mitochondrial DNA (mtDNA)/cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING)/IFN-I pathway.

MATERIALS/METHODS

We used Doxil in combination with RT and αPD-1 in two tumor models (B16-CD133 melanoma and MC38 colon carcinoma) with mice bearing two tumors, only one of which was irradiated. Mechanistic studies on the role of the mtDNA/cGAS/STING/IFN-I axis were performed using inhibitors and knockout cells in vitro as well as in mice.

RESULTS

Addition of a single low dose of Doxil to RT and αPD-1 strongly enhanced the RT/αPD-1-induced abscopal effect in both models. Complete cures of non-irradiated tumors were mainly observed in triple-treated mice. Triple therapy induced more cross-presenting dendritic cells (DCs) and more tumor-specific CD8+ T cells than RT/αPD-1 and Doxil/αPD-1, particularly in non-irradiated tumors. Coincubation of Doxil-treated and/or RT-treated tumor cells with DCs enhanced DC antigen cross-presentation which is crucial for inducing CD8+ T cells. CD8+ T cell depletion or implantation of cGAS-deficient or STING-deficient tumor cells abolished the abscopal effect. Doxorubicin-induced/Doxil-induced IFNβ1 markedly depended on the cGAS/STING pathway. Doxorubicin-treated/Doxil-treated tumor cells depleted of mtDNA secreted less IFNβ1, of the related T cell-recruiting chemokine CXCL10, and ATP; coincubation with mtDNA-depleted tumor cells strongly reduced IFNβ1 secretion by DCs. Implantation of mtDNA-depleted tumor cells, particularly at the non-irradiated/abscopal site, substantially diminished the Doxil-enhanced abscopal effect and tumor infiltration by tumor-specific CD8+ T cells.

CONCLUSIONS

These data show that single low-dose Doxil can substantially enhance the RT/αPD-1-induced abscopal effect, with a strong increase in cross-presenting DCs and CD8+ tumor-specific T cells particularly in abscopal tumors compared with RT/αPD-1 and Doxil/αPD-1. Moreover, they indicate that the mtDNA/cGAS/STING/IFN-I axis is important for the immunogenic/immunomodulatory doxorubicin effects. Our findings may be helpful for the planning of clinical radiochemoimmunotherapy trials in (oligo)metastatic patients.

Nomogram for Predicting Occult Locally Advanced Esophageal Squamous Cell Carcinoma Before Surgery

Introduction

The limitations of preoperative examination result in locally advanced esophageal squamous cell carcinoma (ESCC) often going undetected preoperatively. This study aimed to develop a clinical tool for identifying patients at high risk for occult locally advanced ESCC; the tool can be supplemented with preoperative examination to improve the reliability of preoperative staging.

Materials and Methods

Data of 598 patients who underwent radical resection of ESCC from 2010 to 2017 were analyzed. Logistic multivariate analysis was used to develop a nomogram. The training cohort included patients who underwent surgery during an earlier period (n = 426), and the validation cohort included those who underwent surgery thereafter (n = 172), to confirm the model’s performance. Nomogram discrimination and calibration were evaluated using Harrell's concordance index (C-index) and calibration plots, respectively.

Results

Logistic multivariate analysis suggested that higher preoperative carcinoembryonic antigen levels (>2.43, odds ratio [OR]: 2.093; 95% confidence interval [CI], 1.233–2.554; P = 0.006), presence of preoperative symptoms (OR: 2.737; 95% CI, 1.194–6.277; P = 0.017), presence of lymph node enlargement (OR: 2.100; 95% CI, 1.243–3.550; P = 0.006), and advanced gross aspect (OR: 13.103; 95% CI, 7.689–23.330; P < 0.001) were independent predictors of occult locally advanced ESCC. Based on these predictive factors, a nomogram was developed. The C-indices of the training and validation cohorts were 0.827 and 0.897, respectively, indicating that the model had a good predictive performance. To evaluate the accuracy of the model, we divided patients into high-risk and low-risk groups according to their nomogram scores, and a comparison was made with histopathological data.

Conclusion

The nomogram achieved a good preoperative prediction of occult locally advanced ESCC; it can be used to make rational therapeutic choices.

Tumor-draining lymph nodes: At the crossroads of metastasis and immunity

Early engagement of the lymphatic system by solid tumors in peripheral, nonlymphoid tissues is a clinical hallmark of cancer and often forecasts poor prognosis. The significance of lymph node metastasis for distant spread, however, has been questioned by large-scale lymph node dissection trials and the likely prevalence of direct hematogenous metastasis. Still, an emerging appreciation for the immunological role of the tumor-draining lymph node has renewed interest in its basic biology, role in metastatic progression, antitumor immunity, and patient outcomes. In this review, we discuss our current understanding of the early mechanisms through which tumors engage lymphatic transport and condition tumor-draining lymph nodes, the significance of these changes for both metastasis and immunity, and potential implications of the tumor-draining lymph node for immunotherapy.

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.

Tumor cells, rather than dendritic cells, deliver antigen to the lymph node for cross-presentation

It is widely accepted that generation of tumor specific CD8+ T-cell responses occur via cross-priming; however the source of tumor antigen for this event is unknown. We examined the source and form of tumor antigen required for cross-presentation in the local lymph node (LN) using a syngeneic mouse tumor model expressing a marker antigen. We found that cross-presentation of this model tumor antigen in the LN is dependent on continuous traffic of antigen from the tumor site, but without any detectable migration of tumor resident dendritic cells (DCs). Instead, small numbers of tumor cells metastasize to local LNs where they are exposed to a localized CTL attack, resulting in delivery of tumor antigen into the cross-presentation pathway.

Non-thermal histotripsy tumor ablation promotes abscopal immune responses that enhance cancer immunotherapy

Background

Developing the ability to use tumor-directed therapies to trigger potentially therapeutic immune responses against cancer antigens remains a high priority for cancer immunotherapy. We hypothesized that histotripsy, a novel non-invasive, non-thermal ablation modality that uses ultrasound-generated acoustic cavitation to disrupt tissues, could engender adaptive immune responses to tumor antigens.

Methods

Immunocompetent C57BL/6 mice inoculated with flank melanoma or hepatocellular carcinoma tumors were treated with histotripsy, thermal ablation, radiation therapy, or cytotoxic T lymphocyte-associated protein-4 (CTLA-4) blockade checkpoint inhibition. Lymphocyte responses were measured using flow cytometric and immunohistochemical analyses. The impact of histotripsy on abscopal immune responses was assessed in mice bearing bilateral tumors, or unilateral tumors with pulmonary tumors established via tail vein injection.

Results

Histotripsy ablation of subcutaneous murine melanoma tumors stimulated potent local intratumoral infiltration of innate and adaptive immune cell populations. The magnitude of this immunostimulation was stronger than that seen with tumor irradiation or thermal ablation. Histotripsy also promoted abscopal immune responses at untreated tumor sites and inhibited growth of pulmonary metastases. Histotripsy was capable of releasing tumor antigens with retained immunogenicity, and this immunostimulatory effect was associated with calreticulin translocation to the cellular membrane and local and systemic release of high mobility group box protein 1. Histotripsy ablation potentiated the efficacy of checkpoint inhibition immunotherapy in murine models of melanoma and hepatocellular carcinoma.

Conclusions

These preclinical observations suggest that non-invasive histotripsy ablation can be used to stimulate tumor-specific immune responses capable of magnifying the impact of checkpoint inhibition immunotherapy.

Esophageal Microenvironment: From Precursor Microenvironment to Premetastatic Niche

Esophageal cancer (EC) is the sixth most deadly cancer, and its incidence is still increasing year by year. Although the researches on the molecular mechanisms of EC have been widely carried out and incremental progress has been made, its overall survival rate is still low. There is cumulative evidence showing that the esophageal microenvironment plays a vital role in the development of EC. In precancerous lesions of the esophagus, high-risk environmental factors can promote the development of precancerous lesions by inducing the production of inflammatory factors and the recruitment of immune cells. In the tumor microenvironment, tumor-promoting cells can inhibit anti-tumor immunity and promote tumor progression through a variety of pathways, such as bone marrow-derived suppressor cells (MDSCs), tumor-associated fibroblasts (CAFs), and regulatory T cells (Tregs). The formation of extracellular hypoxia and acidic microenvironment and the change of extracellular matrix stiffness are also important factors affecting tumor progression and metastasis. Simultaneously, primary tumor-derived cytokines and bone marrow-derived immune cells can also promote the formation of pre-metastasis niche of EC lymph nodes, which are beneficial to EC lymph node metastasis. Further research on the specific mechanism of these processes in the occurrence, development, and metastasis of each EC subtype will support us to grasp the overall pre-cancerous prevention, targeted treatment, and metastatic assessment of EC.

Poly(propylacrylic acid)-peptide nanoplexes as a platform for enhancing the immunogenicity of neoantigen cancer vaccines

Cancer vaccines targeting patient-specific tumor neoantigens have recently emerged as a promising component of the rapidly expanding immunotherapeutic armamentarium. However, neoantigenic peptides typically elicit weak CD8+ T cell responses, and so there is a need for universally applicable vaccine delivery strategies to enhance the immunogenicity of these peptides. Ideally, such vaccines could also be rapidly fabricated using chemically synthesized peptide antigens customized to an individual patient. Here, we describe a strategy for simple and rapid packaging of peptide antigens into pH-responsive nanoparticles with endosomal escape activity. Electrostatically-stabilized polyplex nanoparticles (nanoplexes) can be assembled instantaneously by mixing decalysine-modified antigenic peptides and poly(propylacrylic acid) (pPAA), a polyanion with pH-dependent, membrane destabilizing activity. These nanoplexes increase and prolong antigen uptake and presentation on MHC-I (major histocompatibility complex class I) molecules expressed by dendritic cells, resulting in enhanced activation of CD8+ T cells. Using an intranasal immunization route, nanoplex vaccines inhibit formation of lung metastases in a murine melanoma model. Additionally, nanoplex vaccines strongly synergize with the adjuvant α-galactosylceramide (α-GalCer) in stimulating robust CD8+ T cell responses, significantly increasing survival time in mice with established melanoma tumors. Collectively, these findings demonstrate that peptide/pPAA nanoplexes offer a facile and versatile platform for enhancing CD8+ T cell responses to peptide antigens, with potential to complement ongoing advancements in the development of neoantigen-targeted cancer vaccines.

Urothelial bladder cancer may suppress perforin expression in CD8+ T cells by an ICAM-1/TGFβ2 mediated pathway

The immune system plays a significant role in urothelial bladder cancer (UBC) progression, with CD8⁺ T cells being capable to directly kill tumor cells using perforin and granzymes. However, tumors avoid immune recognition by escape mechanisms. In this study, we aim to demonstrate tumor immune escape mechanisms that suppress CD8⁺ T cells cytotoxicity. 42 patients diagnosed with UBC were recruited. CD8⁺ T cells from peripheral blood (PB), sentinel nodes (SN), and tumor were analyzed in steady state and in vitro-stimulated conditions by flow cytometry, RT-qPCR, and ELISA. Mass spectrometry (MS) was used for identification of proteins from UBC cell line culture supernatants. Perforin was surprisingly found to be low in CD8⁺ T cells from SN, marked by 1.8-fold decrease of PRF1 expression, with maintained expression of granzyme B. The majority of perforin-deficient CD8⁺ T cells are effector memory T (T_EM) cells with exhausted Tc2 cell phenotype, judged by the presence of PD-1 and GATA-3. Consequently, perforin-deficient CD8⁺ T cells from SN are low in T-bet expression. Supernatant from muscle invasive UBC induces perforin deficiency, a mechanism identified by MS where ICAM-1 and TGFβ2 signaling were causatively validated to decrease perforin expression in vitro. Thus, we demonstrate a novel tumor escape suppressing perforin expression in CD8⁺ T cells mediated by ICAM-1 and TGFβ2, which can be targeted in combination for cancer immunotherapy.

Potential lymphangiogenesis therapies: Learning from current antiangiogenesis therapies-A review

In recent years, lymphangiogenesis, the process of lymphatic vessel formation from existing lymph vessels, has been demonstrated to have a significant role in diverse pathologies, including cancer metastasis, organ graft rejection, and lymphedema. Our understanding of the mechanisms of lymphangiogenesis has advanced on the heels of studies demonstrating vascular endothelial growth factor C as a central pro-lymphangiogenic regulator and others identifying multiple lymphatic endothelial biomarkers. Despite these breakthroughs and a growing appreciation of the signaling events that govern the lymphangiogenic process, there are no FDA-approved drugs that target lymphangiogenesis. In this review, we reflect on the lessons available from the development of antiangiogenic therapies (26 FDA-approved drugs to date), review current lymphangiogenesis research including nanotechnology in therapeutic drug delivery and imaging, and discuss molecules in the lymphangiogenic pathway that are promising therapeutic targets.

Growth and Immune Evasion of Lymph Node Metastasis

Cancer patients with lymph node (LN) metastases have a worse prognosis than those without nodal disease. However, why LN metastases correlate with reduced patient survival is poorly understood. Recent findings provide insight into mechanisms underlying tumor growth in LNs. Tumor cells and their secreted molecules engage stromal, myeloid, and lymphoid cells within primary tumors and in the lymphatic system, decreasing antitumor immunity and promoting tumor growth. Understanding the mechanisms of cancer survival and growth in LNs is key to designing effective therapy for the eradication of LN metastases. In addition, uncovering the implications of LN metastasis for systemic tumor burden will inform treatment decisions. In this review, we discuss the current knowledge of the seeding, growth, and further dissemination of LN metastases.

Defining the role of the tumor vasculature in antitumor immunity and immunotherapy

It is now well established that cancer cells co-exist within a complex environment with stromal cells and depend for their growth and dissemination on tight and plastic interactions with components of the tumor microenvironment (TME). Cancer cells incite the formation of new blood and lymphatic vessels from preexisting vessels to cope with their high nutrient/oxygen demand and favor tumor outgrowth. Research over the past decades has highlighted the crucial role played by tumor-associated blood and lymphatic vasculature in supporting immunoevasion and in subverting T-cell-mediated immunosurveillance, which are the main hallmarks of cancers. The structurally and functionally aberrant tumor vasculature contributes to the protumorigenic and immunosuppressive TME by maintaining a cancer cell’s permissive environment characterized by hypoxia, acidosis, and high interstitial pressure, while simultaneously generating a physical barrier to T cells' infiltration. Recent research moreover has shown that blood endothelial cells forming the tumor vessels can actively suppress the recruitment, adhesion, and activity of T cells. Likewise, during tumorigenesis the lymphatic vasculature undergoes dramatic remodeling that facilitates metastatic spreading of cancer cells and immunosuppression. Beyond carcinogenesis, the erratic tumor vasculature has been recently implicated in mechanisms of therapy resistance, including those limiting the efficacy of clinically approved immunotherapies, such as immune checkpoint blockers and adoptive T-cell transfer. In this review, we discuss emerging evidence highlighting the major role played by tumor-associated blood and lymphatic vasculature in thwarting immunosurveillance mechanisms and antitumor immunity. Moreover, we also discuss novel therapeutic approaches targeting the tumor vasculature and their potential to help overcoming immunotherapy resistance.

The Role of the Tumor Vasculature in the Host Immune Response: Implications for Therapeutic Strategies Targeting the Tumor Microenvironment

Recently developed cancer immunotherapy approaches including immune checkpoint inhibitors and chimeric antigen receptor T cell transfer are showing promising results both in trials and in clinical practice. These approaches reflect increasing recognition of the crucial role of the tumor microenvironment in cancer development and progression. Cancer cells do not act alone, but develop a complex relationship with the environment in which they reside. The host immune response to tumors is critical to the success of immunotherapy; however, the determinants of this response are incompletely understood. The immune cell infiltrate in tumors varies widely in density, composition, and clinical significance. The tumor vasculature is a key component of the microenvironment that can influence tumor behavior and treatment response and can be targeted through the use of antiangiogenic drugs. Blood vascular and lymphatic endothelial cells have important roles in the trafficking of immune cells, controlling the microenvironment, and modulating the immune response. Improving access to the tumor through vascular alteration with antiangiogenic drugs may prove an effective combinatorial strategy with immunotherapy approaches and might be applicable to many tumor types. In this review, we briefly discuss the host's immune response to cancer and the treatment strategies utilizing this response, before focusing on the pathological features of tumor blood and lymphatic vessels and the contribution these might make to tumor immune evasion.

The lymph node pre-metastatic niche

Lymph node metastases occur frequently during the progression of many types of cancer, and their presence often reflects poor prognosis. The drainage of tumor-derived factors such as antigens, growth factors, cytokines, and exosomes through the lymphatic system to the regional lymph nodes plays an important role in the pre-metastatic conditioning of the microenvironment in lymph nodes, making them receptive and supportive metastatic niches for disseminating tumor cells. Modified immunological responses and remodeling of the vasculature are the most studied tumor-induced pre-metastatic changes in the lymph node microenvironment that promote metastasis, although other metastasis-relevant alterations are also starting to be studied. Here, I review our current understanding of the lymph node pre-metastatic niche, how tumors condition this niche, and the relevance of this conditioning for our understanding of the process of metastasis.

Distinct mechanisms of B and T lymphocyte accumulation generate tumor-draining lymph node hypertrophy

Tumor-draining lymph nodes (TDLNs) often enlarge in human cancer patients and in murine tumor models, due to lymphocyte accumulation and lymphatic sinus growth. B lymphocytes within TDLNs can drive lymph node hypertrophy in response to tumor growth, however little is known about the mechanisms directing the preferential accumulation of B lymphocytes relative to T cells in enlarging TDLNs. To define why B and T lymphocytes accumulate in TDLNs, we quantified lymphocyte proliferation, apoptosis, entry, and exit in TDLNs versus contralateral non-TDLNs (NTDLNs) in a footpad B16-F10 melanoma mouse model. B and T lymphocyte proliferation and apoptosis were increased as the TDLNs enlarged, although relative rates were similar to those of NTDLNs. TDLN entry of B and T lymphocytes via high endothelial venules was also modestly increased in enlarged TDLNs. Strikingly, the egress of B cells was strongly reduced in TDLNs versus NTDLNs, while T cell egress was modestly decreased, indicating that regulation of lymphocyte exit from TDLNs is a major mechanism of preferential B lymphocyte accumulation. Surface sphingosine-1-phosphate receptor 1 (S1PR1) which binds S1P and signals lymphocyte egress, exhibited greater downregulation in B relative to T lymphocytes, consistent with preferential retention of B lymphocytes in TDLNs. TDLN lymphocytes did not activate surface CD69 expression, indicating a CD69-independent mechanism of downregulation of S1PR1. B and T cell trafficking via afferent lymphatics to enter TDLNs also increased, suggesting a pathway for accumulation of tumor-educated lymphocytes in TDLNs. These mechanisms regulating TDLN hypertrophy could provide new targets to manipulate lymphocyte responses to cancer.

The lymphatic system and pancreatic cancer

This review summarizes current knowledge of the biology, pathology and clinical understanding of lymphatic invasion and metastasis in pancreatic cancer. We discuss the clinical and biological consequences of lymphatic invasion and metastasis, including paraneoplastic effects on immune responses and consider the possible benefit of therapies to treat tumors that are localized to lymphatics. A review of current techniques and methods to study interactions between tumors and lymphatics is presented.

Immune modulation by ER stress and inflammation in the tumor microenvironment

It is now increasingly evident that the immune system represents a barrier to tumor emergence, growth, and recurrence. Although this idea was originally proposed almost 50 years ago as the "immune surveillance hypothesis", it is commonly recognized that, with few rare exceptions, tumor cells always prevail. Thus, one of the central unsolved paradoxes of tumor immunology is how a tumor escapes immune control, which is reflected in the lack of effective autochthonous or vaccine-induced anti-tumor T cell responses. In this review, we discuss the role of the endoplasmic reticulum (ER) stress response/unfolded protein response (UPR) in the immunomodulation of myeloid cells and T cells. Specifically, we will discuss how the tumor cell UPR polarizes myeloid cells in a cell-extrinsic manner, and how in turn, thus polarized myeloid cells negatively affect T cell activation and clonal expansion.

Immunomodulatory roles of lymphatic vessels in cancer progression

Lymphatic vessels in the tumor microenvironment are known to foster tumor metastasis in many cancers, and they can undergo activation, hyperplasia, and lymphangiogenesis in the tumor microenvironment and in the tumor-draining lymph node. The mechanism underlying this correlation was originally considered as lymphatic vessels providing a physical route for tumor cell dissemination, but recent studies have highlighted new roles of the lymphatic endothelium in regulating host immunity. These include indirectly suppressing T-cell function by secreting immunosuppressive factors and inhibiting dendritic cell (DC) maturation, as well as directly driving T-cell tolerance by antigen presentation in the presence of inhibitory ligands. Furthermore, lymphatic endothelium scavenges and regulates transendothelial transport actively, controlling the sustained delivery of lymph-borne antigens from chronically inflamed tissues to draining lymph nodes where immature DCs, in the absence of danger signals, along with lymph node stromal cells present these antigens to T cells for maintenance of peripheral tolerance to self-antigens, a mechanism that may be hijacked by some tumors. This Masters of Immunology primer aims to present an overview of research in this area and highlight emerging evidence that suggests lymphatic vessels, and lymphangiogenesis, play important immunomodulatory roles in the tumor microenvironment.

The lymph node microenvironment and its role in the progression of metastatic cancer

Lymph nodes are initial sites for cancer metastasis in many solid tumors. However, their role in cancer progression is still not completely understood. Emerging evidence suggests that the lymph node microenvironment provides hospitable soil for the seeding and proliferation of cancer cells. Resident immune and stromal cells in the lymph node express and secrete molecules that may facilitate the survival of cancer cells in this organ. More comprehensive studies are warranted to fully understand the importance of the lymph node in tumor progression. Here, we will review the current knowledge of the role of the lymph node microenvironment in metastatic progression.

Unraveling autoimmunity with the adoptive transfer of T cells from TCR-transgenic mice

Transgenesis of rearranged α and β chains from the T-cell receptor has allowed the generation of a variety of mice with a predetermined T-cell repertoire. These mice have been extensively used as tools to circumvent the low precursor frequency of naturally occurring endogenous T cells. As such, they have been valuable to study pathways of T-cell development in the thymus. In addition, these mice can also be considered as a valuable source of naive and/or memory T cells with a defined specificity. I will comment in this chapter the use of this source of T cells with known antigen reactivity to study in vivo T-cell behavior in the periphery, including during autoimmune responses.

Targeting the tumor-draining lymph node with adjuvanted nanoparticles reshapes the anti-tumor immune response

Accumulating evidence implicates the tumor-draining lymph node (TDLN) in tumor-induced immune escape, as it drains regulatory molecules and leukocytes from the tumor microenvironment. We asked whether targeted delivery of adjuvant to the TDLN, presumably already bathed in tumor antigens, could promote anti-tumor immunity and hinder tumor growth. To this end, we used 30 nm polymeric nanoparticles (NPs) that effectively target dendritic cells (DCs, CD11c(+)) within the lymph node (LN) after intradermal administration. These NPs accumulated within the TDLN when administered in the limb ipsilateral (i.l.) to the tumor or in the non-TDLN when administered in the contralateral (c.l.) limb. Incorporating the adjuvants CpG or paclitaxel into the NPs (CpG-NP and PXL-NP) induced DC maturation in vitro. When administered daily i.l. and thus targeting the TDLN of a B16-F10 melanoma, adjuvanted NPs induced DC maturation within the TDLN and reshaped the CD4(+) T cell distribution within the tumor towards a Th1 (CXCR3(+)) phenotype. Importantly, this also led to an increase in the frequency of antigen-specific CD8(+) T cells within the tumor. This correlated with slowed tumor growth, in contrast to unhindered tumor growth after c.l. delivery of adjuvanted NPs (targeting a non-TDLN) or i.l. delivery of free adjuvant. CpG-NP treatment in the i.l. limb also was associated with an increase in CD8(+)/CD4(+) T cell ratios and frequencies of activated (CD25(+)) CD8(+) T cells within the TDLN whereas PXL-NP treatment reduced the frequency of regulatory T (FoxP3(+) CD4(+)) cells in the TDLN. Together, these data implicate the TDLN as a delivery target for adjuvant therapy of solid tumors.

Preparation of myeloid derived suppressor cells (MDSC) from naive and pancreatic tumor-bearing mice using flow cytometry and automated magnetic activated cell sorting (AutoMACS)

MDSC are a heterogeneous population of immature macrophages, dendritic cells and granulocytes that accumulate in lymphoid organs in pathological conditions including parasitic infection, inflammation, traumatic stress, graft-versus-host disease, diabetes and cancer. In mice, MDSC express Mac-1 (CD11b) and Gr-1 (Ly6G and Ly6C) surface antigens. It is important to note that MDSC are well studied in various tumor-bearing hosts where they are significantly expanded and suppress anti-tumor immune responses compared to naïve counterparts. However, depending on the pathological condition, there are different subpopulations of MDSC with distinct mechanisms and targets of suppression. Therefore, effective methods to isolate viable MDSC populations are important in elucidating their different molecular mechanisms of suppression in vitro and in vivo. Recently, the Ghansah group has reported the expansion of MDSC in a murine pancreatic cancer model. Our tumor-bearing MDSC display a loss of homeostasis and increased suppressive function compared to naïve MDSC. MDSC percentages are significantly less in lymphoid compartments of naïve vs. tumor-bearing mice. This is a major caveat, which often hinders accurate comparative analyses of these MDSC. Therefore, enriching Gr-1(+) leukocytes from naïve mice prior to Fluorescence Activated Cell Sorting (FACS) enhances purity, viability and significantly reduces sort time. However, enrichment of Gr-1(+) leukocytes from tumor-bearing mice is optional as these are in abundance for quick FACS sorting. Therefore, in this protocol, we describe a highly efficient method of immunophenotyping MDSC and enriching Gr-1(+) leukocytes from spleens of naïve mice for sorting MDSC in a timely manner. Immunocompetent C57BL/6 mice are inoculated with murine Panc02 cells subcutaneously whereas naïve mice receive 1XPBS. Approximately 30 days post inoculation; spleens are harvested and processed into single-cell suspensions using a cell dissociation sieve. Splenocytes are then Red Blood Cell (RBC) lysed and an aliquot of these leukocytes are stained using fluorochrome-conjugated antibodies against Mac-1 and Gr-1 to immunophenotype MDSC percentages using Flow Cytometry. In a parallel experiment, whole leukocytes from naïve mice are stained with fluorescent-conjugated Gr-1 antibodies, incubated with PE-MicroBeads and positively selected using an automated Magnetic Activated Cell Sorting (autoMACS) Pro Separator. Next, an aliquot of Gr-1(+) leukocytes are stained with Mac-1 antibodies to identify the increase in MDSC percentages using Flow Cytometry. Now, these Gr1(+) enriched leukocytes are ready for FACS sorting of MDSC to be used in comparative analyses (naïve vs. tumor- bearing) in in vivo and in vitro assays.

Lymphatic and interstitial flow in the tumour microenvironment: linking mechanobiology with immunity

Tumours often engage the lymphatic system in order to invade and metastasize. The tumour-draining lymph node may be an immune-privileged site that protects the tumour from host immunity, and lymph flow that drains tumours is often increased, enhancing communication between the tumour and the sentinel node. In addition to increasing the transport of tumour antigens and regulatory cytokines to the lymph node, increased lymph flow in the tumour margin causes mechanical stress-induced changes in stromal cells that stiffen the matrix and alter the immune microenvironment of the tumour. We propose that synergies between lymphatic drainage and flow-induced mechanotransduction in the stroma promote tumour immune escape by appropriating lymphatic mechanisms of peripheral tolerance.

Lymphatics: at the interface of immunity, tolerance, and tumor metastasis

The lymphatic system has long been accepted as a passive escape route for metastasizing tumor cells. The classic view that lymphatics solely regulate fluid balance, lipid metabolism, and immune cell trafficking to the LN is now being challenged. Research in the field is entering a new phase with increasing evidence suggesting that lymphatics play an active role modulating inflammation, autoimmune disease, and the anti-tumor immune response. Evidence exists to suggest that the lymphatics and chemokines guide LN bi-functionally, driving immunity vs. tolerance according to demand. At sites of chronic inflammation, autoimmunity, and tumors, however, the same chemokines and aberrant lymphangiogenesis foster disease progression. These caveats point to the existence of a complex, finely balanced relationship between lymphatics and the immune system in health and disease. This review discusses emerging concepts in the fields of immunology, tumor biology, and lymphatic physiology, identifying critical, overlapping functions of lymphatics, the LN and lymphoid factors in tipping the balance of immunity vs. tolerance in favor of a growing tumor.

Evidence for a repertoire of functional untolerized CD4+ T cells specific for melanoma-associated antigens

Active vaccination against melanoma requires tolerance break as melanoma-associated antigens (MAA) used in vaccine formula are mostly self-antigens. While tolerance to MAA in the CD8(+) T cell compartment is well characterized, it is still not the case for the CD4(+) T cell compartment. Here, we analysed CD4(+) T cell tolerance to such antigens in mice genetically engineered to express ovalbumin (OVA) in melanocytes (Tyr-OVA mice). When we crossed Tyr-OVA mice with DO11.10 and OT-II mice transgenic for an OVA-specific TCR restricted by MHC class II, we observed different tolerization levels. Central tolerance was complete for high avidity DO11.10 CD4(+) T cells, but absent for low avidity OT-II CD4(+) T cells. OT-II CD4(+) T cells also ignored OVA in the periphery of Tyr-OVA mice, albeit being potently reactive to vaccination. OVA challenge in single transgenic Tyr-OVA mice confirmed the existence of OVA-reactive CD4(+) T cells with the induction of efficient T helper cells for antibody production and anti-tumour T cell response. In total, our study demonstrates the existence of low avidity MAA-specific CD4(+) T cells escaping by ignorance central and peripheral tolerance, but valuable in the context of vaccination against melanoma.

No relationship between the distribution of mast cells and the survival of stage IIIB colon cancer patients

Background

Mast cells promote the progression of experimental tumors and might be a valuable therapeutic target. However, the relevant clinical evidence is still controversial. This study analyzed the relationship between the distribution of mast cells and the survival of patients with colon cancer to study whether mast cells contribute to tumor progression.

Materials and methods

Ninety-three cases of pathologically confirmed primary cancer tissues matched with adjacent normal mucosa, metastases of regional-draining lymph nodes and regional-draining lymph nodes without metastases were collected from stage IIIB colon carcinoma patients between January 1997 and July 2004 at the Cancer Center of Sun Yat-Sen University. Tryptase-positive mast cells were counted. The relationships of the distribution of mast cells with clinicopathologic parameters and 5-year survival were analyzed.

Results

Although the mast cell count in the mucosa adjacent to the primary colon cancer was significantly higher than that in the stroma of the primary colon cancer, no difference in mast cell counts was observed between the stroma in lymph node metastasis and the lymph tissue adjacent to the metastasis. Additionally, the mast cell count in the regional-draining lymph node without the invasion of cancer cells was significantly higher than that in the stroma of lymph node metastasis and adjacent lymph tissue. However, none of those mast cell counts was related to 5-year survival.

Conclusion

Although mast cell count varied with location, none of the mast cell counts was related to 5-year survival, suggesting that mast cells do not contribute to the progression of stage IIIB colon cancer.

B cells are required for optimal CD4+ and CD8+ T cell tumor immunity: therapeutic B cell depletion enhances B16 melanoma growth in mice

B lymphocytes can both positively and negatively regulate cellular immune responses. Previous studies have demonstrated augmented T cell-mediated tumor immunity in genetically B cell-deficient mice, suggesting that therapeutic B cell depletion would enhance tumor immunity. To test this hypothesis and quantify B cell contributions to T cell-mediated anti-tumor immune responses, mature B cells were depleted from wild-type adult mice using CD20 mAb prior to syngeneic B16 melanoma tumor transfers. Remarkably, s.c. tumor volume and lung metastasis were increased 2-fold in B cell-depleted mice. Effector-memory and IFN-gamma-or TNF-alpha-secreting CD4(+) and CD8(+) T cell induction was significantly impaired in B cell-depleted mice with tumors. Tumor Ag-specific CD8(+) T cell proliferation was also impaired in tumor-bearing mice that lacked B cells. Thus, B cells were required for optimal T cell activation and cellular immunity in this in vivo nonlymphoid tumor model. Although B cells may not have direct effector roles in tumor immunity, impaired T cell activation, and enhanced tumor growth in the absence of B cells argue against previous proposals to augment tumor immunity through B cell depletion. Rather, targeting tumor Ags to B cells in addition to dendritic cells is likely to optimize tumor-directed vaccines and immunotherapies.

Tumor lymphatics

In this article we survey more than three centuries of observation and research into tumor-associated lymphatic vessels, and their role in the metastatic spread of cancer. This historical overview documents how questions regarding tumor lymphatics have been central to concepts about the process of metastasis, and how this has subsequently influenced the clinical treatment of cancer. In turn, we show how analysis of the efficacy of these treatments has challenged long-standing notions regarding the tumor lymphatics. Starting with the discovery of VEGFR-3 and its ligands VEGF-C and VEGF-D, we also review how the rapid developments over the last 15 years in the molecular analysis of the lymphatic system and in particular lymphangiogenesis have contributed to this debate. Finally we speculate on how apparently paradoxical bodies of evidence regarding the role of tumor lymphatics in determining patterns of metastatic spread might be reconciled.

Direct presentation of a melanocyte-associated antigen in peripheral lymph nodes induces cytotoxic CD8+ T cells

Encounter of self-antigens in the periphery by mature T cells induces tolerance in the steady-state. Hence, it is not understood why the same peripheral antigens are also promiscuously expressed in the thymus to mediate central tolerance. Here, we analyzed CD8(+) T-cell tolerance to such an antigen constituted by ovalbumin under the control of the tyrosinase promoter. As expected, endogenous CD8(+) T-cell responses were altered in the periphery of transgenic mice, resulting from promiscuous expression of the self-antigen in mature medullary epithelial cells and deletion of high-affinity T cells in the thymus. In adoptive T-cell transfer experiments, we observed constitutive presentation of the self-antigen in peripheral lymph nodes. Notably, this self-antigen presentation induced persisting cytotoxic cells from high-affinity CD8(+) T-cell precursors. Lymph node resident melanoblasts expressing tyrosinase directly presented the self-antigen to CD8(+) T cells, independently of bone marrow-derived antigen-presenting cells. This peripheral priming was independent of the subcellular localization of the self-antigen, indicating that this mechanism may apply to other melanocyte-associated antigens. Hence, central tolerance by promiscuous expression of peripheral antigens is a mandatory, rather than a superfluous, mechanism to counteract the peripheral priming, at least for self-antigens that can be directly presented in lymph nodes. The peripheral priming by lymph node melanoblasts identified here may constitute an advantage for immunotherapies based on adoptive T-cell transfer.

Inefficient presentation of tumor-derived antigen by tumor-infiltrating dendritic cells

BACKGROUND

Transplantable B16 melanoma is widely used as a tumor model to investigate tumor immunity. We wished to characterize the leukocyte populations infiltrating B16 melanoma tumors, and the functional properties of tumor-infiltrating dendritic cells (TIDC).

MATERIALS AND METHODS

We used the B16 melanoma cell line expressing ovalbumin protein (OVA) to investigate the phenotype and T cell stimulatory capacity of TIDC.

RESULTS

The majority of leukocytes in B16 melanoma were macrophages, which colocalized with TIDCs, B and T cells to the peripheral area of the tumor. Both myeloid and plasmacytoid DC populations were present within tumors. Most of these DCs appeared immature, but about a third expressed a mature phenotype. TIDCs did not present tumor-derived antigen, as they were unable to induce the proliferation of tumor-specific CD4+ and CD8+ T cells in vitro unless in the presence of specific peptides. Some presentation of tumor-derived antigen could be demonstrated in the tumor-draining lymph node using in vivo proliferation assays. However, while proliferation of CD8+ T cells was reproducibly demonstrated, no proliferation of CD4+ T cells was observed.

CONCLUSION

In summary, our data suggest that DCs in tumors have limited antigen-presenting function. Inefficient antigen presentation extends to the tumor-draining lymph node, and may affect the generation of antitumor immune responses.