Modeling pre-metastatic lymphvascular niche in the mouse ear sponge assay

The mTOR Inhibitor Rapamycin Counteracts Follicle Activation Induced by Ovarian Cryopreservation in Murine Transplantation Models

Background and Objectives: Ovarian tissue cryopreservation followed by autotransplantation (OTCTP) is currently the only fertility preservation option for prepubertal patients. Once in remission, the autotransplantation of frozen/thawed tissue is performed when patients want to conceive. A major issue of the procedure is follicular loss directly after grafting mainly due to follicle activation. To improve follicular survival during the OTCTP procedure, we inhibited the mTOR pathway involved in follicle activation using rapamycin, an mTOR inhibitor. Next, we compared two different in vivo models of transplantation: the recently described non-invasive heterotopic transplantation model between the skin layers of the ears, and the more conventional and invasive transplantation under the kidney capsule. Materials and Methods: To study the effects of adding rapamycin during cryopreservation, 4-week-old C57BL/6 mouse ovaries, either fresh, slow-frozen, or slow-frozen with rapamycin, were autotransplanted under the kidney capsule of mice and recovered three weeks later for immunohistochemical (IHC) analysis. To compare the ear with the kidney capsule transplantation model, fresh 4-week-old C57BL/6 mouse ovaries were autotransplanted to either site, followed by an injection of either LY294002, a PI3K inhibitor, vehicle control, or neither, and these were recovered three weeks later for IHC analysis. Results: Rapamycin counteracts cryopreservation-induced follicle proliferation, as well as AKT and mTOR pathway activation, in ovaries autotransplanted for three weeks under the kidney capsule of mice. Analyses of follicle proliferation, mTOR activation, and the effects of LY294002 treatment were similar in transplanted ovaries using either the ear or kidney capsule transplantation model. Conclusions: By adding rapamycin during the OTCTP procedure, we were able to transiently maintain primordial follicles in a quiescent state. This is a promising method for improving the longevity of the ovarian graft. Furthermore, both the ear and kidney capsule transplantation models were suitable for investigating follicle activation and proliferation and pharmacological strategies.

The cellular and molecular mediators of metastasis to the lung

Organ-specific metastasis to secondary organs is dependent on the formation of a supportive pre-metastatic niche. This tissue-specific microenvironmental response is thought to be mediated by mutational and epigenetic changes to primary tumour cells resulting in altered cross-talk between cell types. This response is augmented through the release of tumour and stromal signalling mediators including cytokines, chemokines, exosomes and growth factors. Although researchers have elucidated some of the cancer-promoting features that are bespoke to organotropic metastasis to the lungs, it remains unclear if these are organ-specific or generic between organs. Understanding the mechanisms that mediate the metastasis-promoting synergy between the host microenvironment, immunity, and pulmonary structures may elucidate predictive, prognostic and therapeutic markers that could be targeted to reduce the metastatic burden of disease. Herein, we give an updated summary of the known cellular and molecular mechanisms that contribute to the formation of the lung pre-metastatic niche and tissue-specific metastasis.

Periostin in lymph node pre-metastatic niches governs lymphatic endothelial cell functions and metastatic colonization

Although lymph node (LN) metastasis is an important prognostic parameter in cervical cancer, the tissue remodeling at a pre-metastatic state is poorly documented in LNs. We here identified periostin (POSTN) as a component of non-metastatic LNs by applying proteomic analyses and computerized image quantifications on LNs of patients with cervical cancer. We provide evidence for remarkable modifications of POSTN and lymphatic vessel distributions and densities in non-metastatic sentinel and metastatic human LNs, when compared to distant non-metastatic LNs. POSTN deposition at a pre-metastatic stage was demonstrated in a pre-clinical murine model (the ear sponge assay). Its expression by fibroblastic LN cells was assessed by in situ hybridization and in vitro cultures. In vitro, POSTN promoted lymphatic endothelial cell functions and tumor cell proliferation. Accordingly, the in vivo injection of recombinant POSTN together with VEGF-C boosted the lymphangiogenic response, while the metastatic potential of tumor cells was drastically reduced using a POSTN blocking antibody. This translational study also supports the existence of an unprecedented dialog “in cascade”, between the primary tumor and the first pelvic nodal relay in early cervical cancer, and subsequently from pelvic LN to para-aortic LNs in locally advanced cervical cancers. Collectively, this work highlights the association of POSTN deposition with lymphangiogenesis in LNs, and provides evidence for a key contribution of POSTN in promoting VEGF-C driven lymphangiogenesis and the seeding of metastatic cells.

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

Simple Summary

Lymphangiogenesis is the formation of new lymphatic vessels in physiological conditions but has also been found to be associated with pathologies. For example, it has been proven to be involved in cancer progression and metastatic dissemination through the body. Thus, it became a key element to study in the management of this widespread disease. To date, the study of lymphangiogenesis takes place at the biological (in vitro and in vivo) and computational (in silico) levels. The association of these complementary fields combined with imaging techniques constitutes a real toolbox in pathological lymphangiogenesis understanding.

Abstract

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.

Evaluation of an alternative heterotopic transplantation model for ovarian tissue to test pharmaceuticals improvements for fertility restoration

BACKGROUND

Ovarian tissue cryopreservation and transplantation (OTCTP) is currently the main option available to preserve fertility in prepubertal patients undergoing aggressive cancer therapy treatments. However, a major limitation of OTCTP is follicle loss after transplantation. The mouse is a model of choice for studying ovarian function and follicle development after ovarian tissue grafting in vivo. In these mouse models, ovarian tissue or ovaries can be transplanted to different sites. Our aim was to evaluate a new alternative to heterotopic transplantation models that could be useful to test pharmaceutical improvement for ovarian grafts after OTCTP.

METHODS

Slow frozen murine whole ovaries were transplanted into the mouse ears (between the external ear skin layer and the cartilage). Ovarian transplants were recovered after 3, 14 or 21 days. Grafts were analyzed by immunohistochemistry and follicle density analyses were performed.

RESULTS

An increase of ovarian vascularization (CD31 and Dextran-FITC positive staining), as well as cellular proliferation (Ki67 staining) were observed 3 weeks after transplantation in comparison to 3 days. Fibrosis density, evaluated after Van Gieson staining, decreased 3 weeks after transplantation. Furthermore, transplantation of cryopreserved ovaries into ovariectomized mice favored follicle activation compared to transplantation into non-ovariectomized mice.

CONCLUSION

The present study indicates that surgical tissue insertion in the highly vascularized murine ear is an effective model for ovarian grafting. This model could be helpful in research to test pharmaceutical strategies to improve the function and survival of cryopreserved and transplanted ovarian tissue.

Angiopoietin-2-induced lymphatic endothelial cell migration drives lymphangiogenesis via the β1 integrin-RhoA-formin axis

Lymphangiogenesis is an essential physiological process but also a determining factor in vascular-related pathological conditions. Angiopoietin-2 (Ang2) plays an important role in lymphatic vascular development and function and its upregulation has been reported in several vascular-related diseases, including cancer. Given the established role of the small GTPase RhoA on cytoskeleton-dependent endothelial functions, we investigated the relationship between RhoA and Ang2-induced cellular activities. This study shows that Ang2-driven human dermal lymphatic endothelial cell migration depends on RhoA. We demonstrate that Ang2-induced migration is independent of the Tie receptors, but dependent on β1 integrin-mediated RhoA activation with knockdown, pharmacological approaches, and protein sequencing experiments. Although the key proteins downstream of RhoA, Rho kinase (ROCK) and myosin light chain, were activated, blockade of ROCK did not abrogate the Ang2-driven migratory effect. However, formins, an alternative target of RhoA, were identified as key players, and especially FHOD1. The Ang2-RhoA relationship was explored in vivo, where lymphatic endothelial RhoA deficiency blocked Ang2-induced lymphangiogenesis, highlighting RhoA as an important target for anti-lymphangiogenic treatments.

Siglec-15 Is an Immune Suppressor and Potential Target for Immunotherapy in the Pre-Metastatic Lymph Node of Colorectal Cancer

Lymph node metastasis indicates a poor prognosis in colorectal cancer. To better understand the underlying mechanisms of lymph node metastasis, we analyzed transcriptome characteristics of the pre-metastatic lymph node, a putative microenvironment favorable for the seeding and proliferation of cancer cells. Thus, we tried to compare and elucidate the transcriptional and immune characteristics of sentinel lymph nodes (SNs) with matched non-sentinel lymph nodes (NSNs) in colorectal cancer patients. In this study, a total of 38 pairs of SNs and NSNs were collected, in which 26 pairs of non-metastatic lymph nodes were subjected to RNA-seq and bioinformatics analysis for the gene expression profiles. There were 16 differentially expressed genes between SNs and NSNs being identified, including 9 upregulated and 7 downregulated genes in SN. Gene Ontology (GO) classification analysis revealed that the differentially expressed genes were mainly involved in leukocyte differentiation, chemokine secretion, and immune system regulation. In the meantime, gene set enrichment analysis (GSEA) showed that immune-related signaling pathways, such as transforming growth factor beta (TGF-β) signaling and tumor necrosis factor alpha (TNF-α)/nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling, were enriched in NSN, while cell proliferation–related signaling pathways were enriched in SN, including MYC signaling and G2M checkpoint signaling. We further identified SIGLEC15 as a top upregulated gene in SN. However, RNAscope assay showed that SIGLEC15 was not largely co-expressed with M2 macrophage marker CD163. We then selected eight pairs of lymph nodes for further cytological studies. Flow cytometry analysis revealed that Siglec-15 was expressed on all myeloid cell subsets. The relative expression of SEGLEC15 (SN/NSN) was correlated with the microsatellite instability (MSI) status in colorectal cancer patients. Further studies found that small interfering ribonucleic acid (siRNA)-mediated silencing of SLGLEC15 can enhance the anti-tumor function of T cells, as indicated by cytokine release analysis. In conclusion, we presented here a first report on the gene expression profiling of the pre-metastatic lymph node in colorectal cancer. The findings in this study suggest that SIGLEC15 plays an important role in SN immunosuppression. SEGLEC15 silencing could be a therapeutic strategy for restoring T cell function in tumor SNs.

The lymphatic vasculature: An active and dynamic player in cancer progression

The lymphatic vasculature has been widely described and explored for its key functions in fluid homeostasis and in the organization and modulation of the immune response. Besides transporting immune cells, lymphatic vessels play relevant roles in tumor growth and tumor cell dissemination. Cancer cells that have invaded into afferent lymphatics are propagated to tumor‐draining lymph nodes (LNs), which represent an important hub for metastatic cell arrest and growth, immune modulation, and secondary dissemination to distant sites. In recent years many studies have reported new mechanisms by which the lymphatic vasculature affects cancer progression, ranging from induction of lymphangiogenesis to metastatic niche preconditioning or immune modulation. In this review, we provide an up‐to‐date description of lymphatic organization and function in peripheral tissues and in LNs and the changes induced to this system by tumor growth and progression. We will specifically focus on the reported interactions that occur between tumor cells and lymphatic endothelial cells (LECs), as well as on interactions between immune cells and LECs, both in the tumor microenvironment and in tumor‐draining LNs. Moreover, the most recent prognostic and therapeutic implications of lymphatics in cancer will be reported and discussed in light of the new immune‐modulatory roles that have been ascribed to LECs.

Spatial architecture of the immune microenvironment orchestrates tumor immunity and therapeutic response

Tumors are not only aggregates of malignant cells but also well-organized complex ecosystems. The immunological components within tumors, termed the tumor immune microenvironment (TIME), have long been shown to be strongly related to tumor development, recurrence and metastasis. However, conventional studies that underestimate the potential value of the spatial architecture of the TIME are unable to completely elucidate its complexity. As innovative high-flux and high-dimensional technologies emerge, researchers can more feasibly and accurately detect and depict the spatial architecture of the TIME. These findings have improved our understanding of the complexity and role of the TIME in tumor biology. In this review, we first epitomized some representative emerging technologies in the study of the spatial architecture of the TIME and categorized the description methods used to characterize these structures. Then, we determined the functions of the spatial architecture of the TIME in tumor biology and the effects of the gradient of extracellular nonspecific chemicals (ENSCs) on the TIME. We also discussed the potential clinical value of our understanding of the spatial architectures of the TIME, as well as current limitations and future prospects in this novel field. This review will bring spatial architectures of the TIME, an emerging dimension of tumor ecosystem research, to the attention of more researchers and promote its application in tumor research and clinical practice.

Acetylsalicylic acid and salicylic acid present anticancer properties against melanoma by promoting nitric oxide-dependent endoplasmic reticulum stress and apoptosis

Melanoma is the most aggressive and fatal type of skin cancer due to being highly proliferative. Acetylsalicylic acid (ASA; Aspirin) and salicylic acid (SA) are ancient drugs with multiple applications in medicine. Here, we showed that ASA and SA present anticancer effects against a murine model of implanted melanoma. These effects were also validated in 3D- and 2D-cultured melanoma B16F10 cells, where the drugs promoted pro-apoptotic effects. In both in vivo and in vitro models, SA and ASA triggered endoplasmic reticulum (ER) stress, which culminates with the upregulation of the pro-apoptotic transcription factor C/EBP homologous protein (CHOP). These effects are initiated by ASA/SA-triggered Akt/mTOR/AMPK-dependent activation of nitric oxide synthase 3 (eNOS), which increases nitric oxide and reactive oxygen species production inducing ER stress response. In the end, we propose that ASA and SA instigate anticancer effects by a novel mechanism, the activation of ER stress.

Tumor exposed-lymphatic endothelial cells promote primary tumor growth via IL6

Solid tumors are composed of tumor cells and stromal cells including lymphatic endothelial cells (LEC), which are mainly viewed as cells forming lymphatic vessels involved in the transport of metastatic and immune cells. We here reveal a new mechanism by which tumor exposed-LEC (teLEC) exert mitogenic effects on tumor cells. Our conclusions are supported by morphological and molecular changes induced in teLEC that in turn enhance cancer cell invasion in 3D cultures and tumor cell proliferation in vivo. The characterization of teLEC secretome by RNA-Sequencing and cytokine array revealed that interleukine-6 (IL6) is one of the most modulated molecules in teLEC, whose production was negligible in unexposed LEC. Notably, neutralizing anti-human IL6 antibody abrogated teLEC-mediated mitogenic effects in vivo, when LEC were mixed with tumor cells in the ear sponge assay. We here assign a novel function to teLEC that is beyond their role of lymphatic vessel formation. This work highlights a new paradigm, in which teLEC exert “fibroblast-like properties”, contribute in a paracrine manner to the control of tumor cell properties and are worth considering as key stromal determinant in future studies.

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teLEC, but not normal LEC, produce huge amount of IL6.

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IL6-derived teLEC exert mitogenic effect on tumor cells, in the primary tumor.

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teLEC act as fibroblast-like cells in the tumor microenvironment.

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It warrants to revisit the “vascular-centric view” of LECs.

Mechanisms of Tumor-Induced Lymphovascular Niche Formation in Draining Lymph Nodes

Enlargement of the lymphatic vascular network in tumor-draining lymph nodes (LNs) often precedes LN metastasis, likely providing a lymphovascular niche for tumor cells. We investigated morphological and molecular changes associated with the lymphatic remodeling process, using the 4T1 breast cancer and B16F10 melanoma models. Lymphatic expansion in tumor-draining LNs is mediated by sprouting and proliferation of lymphatic endothelial cells (LECs) as early as 4 days after tumor implantation. RNA sequencing revealed an altered transcriptional profile of LECs from tumor-draining compared to naive LNs with similar changes in both tumor models. Integrin αIIb is upregulated in LECs of tumor-draining LNs and mediates LEC adhesion to fibrinogen in vitro. LEC-associated fibrinogen was also detected in LNs in vivo, suggesting a role of integrin αIIb in lymphatic remodeling. Together, our results identify specific responses of LN LECs to tumor stimuli and provide insights into the mechanisms of lymphovascular niche formation in tumor-draining LNs.

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Lymph node lymphatic endothelial cells (LN LECs) dramatically react to tumor stimuli

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Cell adhesion molecules are among the strongest differentially regulated genes

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Itga2b is upregulated and associated with fibrinogen in tumor-draining LN LECs

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Itga2b mediates adhesion of LN LECs to fibrinogen

Decoding cancer cell death-driven immune cell recruitment: An in vivo method for site-of-vaccination analyses

Anticancer vaccines have recently received renewed attention for immunotherapy of at least a subset of cancer-types. Such vaccines mostly involve either killed cancer or tumor cells alone, or combinations thereof with specific (co-incubated) innate immune cells. In recent years, the immunogenic characteristics of the dead or dying cancer cells have emerged as decisive factors behind the success of anticancer vaccines. This has amplified the importance of accounting for immunology of cell death while preparing anticancer vaccines. This, in turn, has increased the emphasis on the immune reactions at the site-of-vaccination since the therapeutic efficacy of the killed cancer/tumor cell vaccines is contingent upon the nature and characteristics of these reactions at the site-of-injection. In this article, we present a systematic methodology that exploits the murine ear pinna model to study differential immune cell recruitment by dead/dying cancer cells injected in vivo, thereby modeling the site-of-injection relevant for anticancer vaccines.

uPARAP/Endo180 receptor is a gatekeeper of VEGFR-2/VEGFR-3 heterodimerisation during pathological lymphangiogenesis

The development of new lymphatic vessels occurs in many cancerous and inflammatory diseases through the binding of VEGF-C to its receptors, VEGFR-2 and VEGFR-3. The regulation of VEGFR-2/VEGFR-3 heterodimerisation and its downstream signaling in lymphatic endothelial cells (LECs) remain poorly understood. Here, we identify the endocytic receptor, uPARAP, as a partner of VEGFR-2 and VEGFR-3 that regulates their heterodimerisation. Genetic ablation of uPARAP leads to hyperbranched lymphatic vasculatures in pathological conditions without affecting concomitant angiogenesis. In vitro, uPARAP controls LEC migration in response to VEGF-C but not VEGF-A or VEGF-CCys156Ser. uPARAP restricts VEGFR-2/VEGFR-3 heterodimerisation and subsequent VEGFR-2-mediated phosphorylation and inactivation of Crk-II adaptor. uPARAP promotes VEGFR-3 signaling through the Crk-II/JNK/paxillin/Rac1 pathway. Pharmacological Rac1 inhibition in uPARAP knockout mice restores the wild-type phenotype. In summary, our study identifies a molecular regulator of lymphangiogenesis, and uncovers novel molecular features of VEGFR-2/VEGFR-3 crosstalk and downstream signaling during VEGF-C-driven LEC sprouting in pathological conditions.

Consensus guidelines for the use and interpretation of angiogenesis assays

The formation of new blood vessels, or angiogenesis, is a complex process that plays important roles in growth and development, tissue and organ regeneration, as well as numerous pathological conditions. Angiogenesis undergoes multiple discrete steps that can be individually evaluated and quantified by a large number of bioassays. These independent assessments hold advantages but also have limitations. This article describes in vivo, ex vivo, and in vitro bioassays that are available for the evaluation of angiogenesis and highlights critical aspects that are relevant for their execution and proper interpretation. As such, this collaborative work is the first edition of consensus guidelines on angiogenesis bioassays to serve for current and future reference.

Ear Sponge Assay: A Method to Investigate Angiogenesis and Lymphangiogenesis in Mice

Angiogenesis and lymphangiogenesis have become important research areas in the biomedical field. The outgrowth of new blood (angiogenesis) and lymphatic (lymphangiogenesis) vessels from preexisting ones is involved in many pathologies including cancer. In-depth investigations of molecular determinants such as proteases in these complex processes require reliable in vivo models. Here we present the ear sponge assay as an easy, rapid, quantitative and reproducible model of angiogenesis and lymphangiogenesis. In this system, a gelatin sponge soaked with tumor cells, cell-conditioned medium, or a compound to be tested is implanted, for 2-4 weeks, between the two mouse ear skin layers. The two vascular networks are next examined through histological procedures.