The mechanisms by which tumor-derived extracellular vesicles and particles (EVPs) promote vascular permeability during premetastatic niche formation remain unclear. Here, we show that tumor EVPs rapidly induce vascular leakiness within 1 h of administration in female mice, creating a permissive environment that enhances metastatic seeding. Rather than acting directly on endothelial cells, EVPs activate NF-κB and JAK-STAT signaling in interstitial macrophages, leading to IL-6 secretion and increased vascular permeability. Interstitial macrophage depletion markedly reduces EVP-induced vascular leakiness and metastasis. We identify extracellular vesicle-associated integrin α5 (ITGα5) as a major functional determinant of this process, promoting macrophage activation and IL-6 secretion without affecting EVP uptake. EVPs derived from colorectal cancer tumors with high ITGα5 similarly induce macrophage IL-6 secretion and vascular permeability. Together, these findings define an EVP-macrophage-IL-6 axis that drives vascular permeability during premetastatic niche formation and identify EVP-associated ITGα5 as a key mediator of metastatic progression and a potential therapeutic target.

Antigen processing and presentation (APP) is essential for adaptive immunosurveillance. We uncover a mechanism whereby activated T cell-derived extracellular vesicles (ATEVs) drive a positive feedback loop that enhances antigen presentation and immune responses in normal physiology and cancer. ATEV-induced immunogenicity relies on extracellular vesicular double-stranded DNA (EVDNA), which is notably abundant and primarily composed of genomic DNA enriched in immune-related genes, including those encoding APP machinery. Mechanistically, granzyme B (Gzmb) packaged by ATEVs disrupts the nuclear envelope of recipient cells, facilitating intranuclear transfer and subsequent transient expression of EVDNA encoding APP genes. DNase treatment removes most AT-EVDNA, abrogating APP upregulation and thus T cell activation and recruitment to tumors. Notably, ATEVs hold promise as an acellular immunotherapy, restoring APP and synergizing with checkpoint blockade in immunotherapy-refractory tumors. Collectively, our findings uncover a mechanism of transient, non-viral gene delivery by ATEVs that boosts APP and anti-tumor immunity while limiting autoimmunity.

Cancer is a systemic disease with complications beyond the primary tumor site. Among them, thrombosis is the second leading cause of death in patients with certain cancers (e.g., pancreatic ductal adenocarcinoma [PDAC]) and advanced-stage disease. Here, we demonstrate that pro-thrombotic small extracellular vesicles (sEVs) are secreted by C-X-C motif chemokine 13 (CXCL13)-reprogrammed interstitial macrophages in the non-metastatic lung microenvironment of multiple cancers, a niche that we define as the pro-thrombotic niche (PTN). These sEVs package clustered integrin beta(2) that dimerizes with integrin alpha(X) and interacts with platelet-bound glycoprotein (GP)Ib to induce platelet aggregation. Blocking integrin beta(2) decreases both sEV-induced thrombosis and lung metastasis. Importantly, sEV-beta(2) levels are elevated in the plasma of PDAC patients prior to thrombotic events compared with patients with no history of thrombosis. We show that lung PTN establishment is a systemic consequence of cancer progression and identify sEV-beta(2) as a prognostic biomarker of thrombosis risk as well as a target to prevent thrombosis and metastasis.

Extracellular vesicles (EVs) transport biomolecules that mediate intercellular communication. We previously showed that EVs contain DNA (EV-DNA) representing the entire genome. However, the mechanism of genomic EV-DNA packaging and its role in cancer remain elusive. We now demonstrate that EV-DNA is predominantly localized on the vesicle surface and associated with uniquely modified and cleaved histones. Moreover, a genome-wide clustered regularly interspaced short palindromic repeats knockout screen revealed that immune developmental pathways and genes, including apoptotic peptidase activating factor 1 (APAF1) and neutrophil cytosolic factor 1 (NCF1), regulate EV-DNA packaging. Furthermore, in colorectal cancer models, uptake of EV-DNA by pre-metastatic liver Kupffer cells (KCs) activated DNA damage responses. This activation rewired KC cytokine production and promoted the formation of tertiary lymphoid structures, thereby suppressing liver metastasis. Conversely, loss of APAF1 decreased EV-DNA packaging and promoted liver metastasis. Importantly, colorectal cancer biopsy EV-DNA secretion could serve as a predictive biomarker for postoperative metastasis. Taken together, our findings indicate that uniquely chromatinized EV-DNA induces antitumor immunity. Lyden and colleagues find that immune developmental genes, such as apoptotic peptidase activating factor 1 (APAF1), support DNA packaging on the surface of tumor-derived extracellular vesicles that are taken up by resident liver macrophages, thereby suppressing metastasis.

Metastasis occurs frequently after resection of pancreatic cancer (PaC). In this study, we hypothesized that multi-parametric analysis of pre-metastatic liver biopsies would classify patients according to their metastatic risk, timing and organ site. Liver biopsies obtained during pancreatectomy from 49 patients with localized PaC and 19 control patients with non-cancerous pancreatic lesions were analyzed, combining metabolomic, tissue and single-cell transcriptomics and multiplex imaging approaches. Patients were followed prospectively (median 3 years) and classified into four recurrence groups; early (<6 months after resection) or late (>6 months after resection) liver metastasis (LiM); extrahepatic metastasis (EHM); and disease-free survivors (no evidence of disease (NED)). Overall, PaC livers exhibited signs of augmented inflammation compared to controls. Enrichment of neutrophil extracellular traps (NETs), Ki-67 upregulation and decreased liver creatine significantly distinguished those with future metastasis from NED. Patients with future LiM were characterized by scant T cell lobular infiltration, less steatosis and higher levels of citrullinated H3 compared to patients who developed EHM, who had overexpression of interferon target genes (MX1 and NR1D1) and an increase of CD11B(+) natural killer (NK) cells. Upregulation of sortilin-1 and prominent NETs, together with the lack of T cells and a reduction in CD11B(+) NK cells, differentiated patients with early-onset LiM from those with late-onset LiM. Liver profiles of NED closely resembled those of controls. Using the above parameters, a machine-learning-based model was developed that successfully predicted the metastatic outcome at the time of surgery with 78% accuracy. Therefore, multi-parametric profiling of liver biopsies at the time of PaC diagnosis may determine metastatic risk and organotropism and guide clinical stratification for optimal treatment selection.

Extracellular vesicles and particles (EVPs) are pivotal mediators of pre-metastatic niche formation and cancer progression, including induction of vascular permeability, which facilitates tumor cell extravasation and metastasis. However, the mechanisms through which EVPs exert this effect remain poorly understood. Here, we elucidate a novel mechanism by which tumor EVPs enhance endothelial cell permeability, tumor extravasation, and lung metastasis to different degrees, depending on tumor type. Strikingly, vascular leakiness is observed within 48h following tumor implantation and as early as one hour following intravenous injection of tumour-derived EVPs in naïve mice. Surprisingly, rather than acting directly on endothelial cells, EVPs first activate interstitial macrophages (IMs) leading to activation of JAK/STAT signaling and IL-6 secretion in IMs which subsequently promote endothelial permeability. Depletion of IMs significantly reduces tumour-derived EVP-dependent vascular leakiness and metastatic potential. Tumour EVPs that strongly induce vascular leakiness express high levels of ITGα5, and ITGα5 ablation impairs IM activation, cytokine secretion, and subsequently vascular permeability and metastasis. Importantly, IL-6 expression is elevated in IMs from non-involved tumor-adjacent lung tissue compared to distal lung tissue in lung cancer patients, highlight the clinical relevance of our discovery. Our findings identify a key role for IM activation as an initiating step in tumor type-specific EVP-driven vascular permeability and metastasis, offering promising targets for therapeutic intervention.

Cancer alters the function of multiple organs beyond those targeted by metastasis 1 , 2 . Here we show that inflammation, fatty liver and dysregulated metabolism are hallmarks of systemically affected livers in mouse models and in patients with extrahepatic metastasis. We identified tumour-derived extracellular vesicles and particles (EVPs) as crucial mediators of cancer-induced hepatic reprogramming, which could be reversed by reducing tumour EVP secretion via depletion of Rab27a . All EVP subpopulations, exosomes and principally exomeres, could dysregulate hepatic function. The fatty acid cargo of tumour EVPs—particularly palmitic acid—induced secretion of tumour necrosis factor (TNF) by Kupffer cells, generating a pro-inflammatory microenvironment, suppressing fatty acid metabolism and oxidative phosphorylation, and promoting fatty liver formation. Notably, Kupffer cell ablation or TNF blockade markedly decreased tumour-induced fatty liver generation. Tumour implantation or pre-treatment with tumour EVPs diminished cytochrome P450 gene expression and attenuated drug metabolism in a TNF-dependent manner. We also observed fatty liver and decreased cytochrome P450 expression at diagnosis in tumour-free livers of patients with pancreatic cancer who later developed extrahepatic metastasis, highlighting the clinical relevance of our findings. Notably, tumour EVP education enhanced side effects of chemotherapy, including bone marrow suppression and cardiotoxicity, suggesting that metabolic reprogramming of the liver by tumour-derived EVPs may limit chemotherapy tolerance in patients with cancer. Our results reveal how tumour-derived EVPs dysregulate hepatic function and their targetable potential, alongside TNF inhibition, for preventing fatty liver formation and enhancing the efficacy of chemotherapy.

Scanning electron microscopy (SEM) offers an unparalleled view of the membrane topography of mammalian cells by using a conventional osmium (OsO4) and ethanol-based tissue preparation. However, conventional SEM methods limit optimal resolution due to ethanol and lipid interactions and interfere with visualization of fluorescent reporter proteins. Therefore, SEM correlative light and electron microscopy (CLEM) has been hindered by the adverse effects of ethanol and OsO4 on retention of fluorescence signals. To overcome this technological gap in achieving high-resolution SEM and retain fluorescent reporter signals, we developed a freeze-drying method with gaseous nitrogen (FDGN). We demonstrate that FDGN preserves cyto-architecture to allow visualization of detailed membrane topography while retaining fluorescent signals and that FDGN processing can be used in conjunction with a variety of high-resolution imaging systems to enable collection and validation of unique, high-quality data from these approaches. In particular, we show that FDGN coupled with high resolution microscopy provided detailed insight into viral or tumor-derived extracellular vesicle (TEV)-host cell interactions and may aid in designing new approaches to intervene during viral infection or to harness TEVs as therapeutic agents.

Primary tumors secrete a variety of factors to turn distant microenvironments into favorable and fertile 'soil' for subsequent metastases. Among these 'seeding' factors that initiate pre-metastatic niche (PMN) formation, tumorderived extracellular vesicles (EVs) are of particular interest as tumor EVs can direct organotropism depending on their surface integrin profiles. In addition, EVs also contain versatile, bioactive cargo, which include proteins, metabolites, lipids, RNA, and DNA fragments. The cargo incorporated into EVs is collectively shed from cancer cells and cancer-associated stromal cells. Increased understanding of how tumor EVs promote PMN establishment and detection of EVs in bodily fluids highlight how tumor EVs could serve as potential diagnostic and prognostic biomarkers, as well as provide a therapeutic target for metastasis prevention. This review focuses on tumor-derived EVs and how they direct organotropism and subsequently modulate stromal and immune microenvironments at distal sites to facilitate PMN formation. We also outline the progress made thus far towards clinical applications of tumor EVs.

Pioneering cancer biologist and beloved mentor

There is a clinical need for new therapeutics to improve healing of chronic impaired wounds. Thus, we investigated how biopolymer conjugation could be used to improve the wound healing performance of a key growth factor for tissue regeneration: Sonic hedgehog (Shh). We generated two multivalent Shh conjugates (mvShh) using hyaluronic acid with two different MWs, which exhibited equivalent potency and proteolytic protection in vitro. Using db/db diabetic mice, we showed that mvShh made with smaller HyA MW resulted in more rapid and robust neovascularization compared to mvShh made with larger MW HyA. Further, smaller mvShh conjugates resulted in faster wound resolution compared to the unconjugated Shh. This study is the first to show how the wound healing efficacy of multivalent protein polymer conjugates is sensitive to the polymer MW, and our findings suggest that this parameter could be used to enhance the efficacy of growth factor conjugates.

Limited transendothelial permeability across tumor microvessels represents a significant bottleneck in the development of tumor-specific diagnostic agents and theranostic drugs. Here, we show an approach to increase transendothelial permeability of macromolecular and nanoparticle-based contrast agents via inhibition of the type I TGF-β receptor, activin-like kinase 5 (Alk5), in tumors. Alk5 inhibition significantly increased tumor contrast agent delivery and enhancement on imaging studies, while healthy organs remained relatively unaffected. Imaging data correlated with significantly decreased tumor interstitial fluid pressure, while tumor vascular density remained unchanged. This immediately clinically translatable concept involving Alk5 inhibitor pretreatment prior to an imaging study could be leveraged for improved tumor delivery of macromolecular and nanoparticle-based imaging probes and, thereby, facilitate development of more sensitive imaging tests for cancer diagnosis, enhanced tumor characterization, and personalized, image-guided therapies.

HoxA5 is expressed in quiescent endothelial cells (EC), but absent in activated angiogenic EC. To examine the efficacy of targeting HoxA5 therapeutically to quell pathologic or tumor angiogenesis, we generated an inducible, transgenic mouse model of sustained HoxA5 expression in ECs. During pathologic angiogenesis, sustained HoxA5 regulates expression several angiogenic effector molecules, notably increased expression of TSP-2 and reduced expression of VEGF, thus leading to inhibition of pathological angiogenesis in tissues. To evaluate if this impressive reduction of vascularization could also impact tumor angiogenesis, HoxA5 mice were bred with a mouse model of de novo squamous carcinogenesis, e.g., K14-HPV16 mice. Activation of EC-HoxA5 significantly reduced infiltration by mast cells into neoplastic skin, an early hallmark of progression to dysplasia, reduced angiogenic vasculature, and blunted characteristics of tumor progression. To evaluate HoxA5 as a therapeutic, topical application of a HoxA5 transgene onto early neoplastic skin of K14-HPV16 mice similarly resulted in a significant impairment of angiogenic vasculature and progression to dysplasia to a similar extent as observed with genetic delivery of HoxA5. Together these data indicate that HoxA5 represents a novel molecule for restricting pathological and tumorigenic angiogenesis.

Abstract Despite evidence showing a positive correlation between angiogenesis and solid tumor progression, anti-angiogenic therapies have yielded limited, and often, tissue-specific responses. Whereas colorectal and renal cancers show improved responses, anti-angiogenic therapy has not proven effective at clinically managing breast tumor progression or prolonging patient survival. Moreover, anti-angiogenic treatment may promote the emergence of tumors with increased aggression and resistance to standard chemotherapies. Our laboratory has shown that sustained endothelial expression of the anti-angiogenic HoxA5 homeodomain transcription factor reduces angiogenesis and delays progression of squamous cell carcinoma in the KRT14-HPV16 mouse model of skin cancer. We subsequently investigated, whether constitutive endothelial expression of HoxA5 could also impede mammary tumor growth and metastasis. Surprisingly, we observed that endothelial HoxA5 expression increased both primary tumor growth and lung metastasis in the MMTV-PyMT mouse model of breast cancer. Primary tumors from PyMT/HoxA5+ mice exhibited an increased number of large vessels but were significantly more hypoxic, as compared to tumors from control mice. Orthotopic injection of isolated mammary tumor cells from PyMT/HoxA5+ mice into wild-type animals also resulted in larger tumors, as compared to tumor cells isolated from PyMT mice of the same age. Interestingly, although metastasis was increased in the PyMT/HoxA5+ transgenic mice, we did not detect differences in circulating tumor cells, suggesting that tumor cells from PyMT/HoxA5+ mice have increased tumor initiating potential. Thus, while anti-angiogenic HoxA5 expression in the endothelium delays skin tumor progression, more aggressive tumors arise in the mammary gland. We are currently evaluating the response of breast tumors in PyMT/HoxA5+ mice to standard cancer chemotherapeutics, as well as evaluating novel approaches to potentially target more aggressive tumors emerging from chronic hypoxic conditions. Citation Format: Josette Northcott, Hans Layman, Nancy Boudreau. Mammary tumor aggressiveness is exacerbated by endothelial HoxA5 expression. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5221. doi:10.1158/1538-7445.AM2015-5221

Despite their preclinical promise, few recombinant growth factors have been fully developed into effective therapies, in part, due to the short interval of therapeutic activity after administration. To address this problem, we developed nanoscale polymer conjugates for multivalent presentation of therapeutic proteins that enhance the activation of targeted cellular responses. As an example of this technology, we conjugated multiple Sonic hedgehog (Shh) proteins onto individual hyaluronic acid biopolymers to generate multivalent protein clusters at defined ratios (i.e., valencies) that yield enhanced Shh pathway activation at equivalent concentrations relative to unconjugated Shh. In this study, we investigated whether these multivalent conjugates (mvShh) could be used to improve the therapeutic function of Shh. We found that a single treatment with mvShh significantly accelerated the closure of full-thickness wounds in diabetic (db/db) mice compared to either an equivalent dose of unconjugated Shh or the vehicle control. Furthermore, we identified specific indicators of wound healing in fibroblasts and endothelial cells (i.e., transcriptional activation and cell migration) that were activated by mvShh in vitro and at concentrations approximately an order of magnitude lower than the unconjugated Shh. Taken together, our findings suggest that mvShh conjugates exhibit greater potency to activate the Shh pathway, and this multivalency advantage improves its therapeutic effect to accelerate wound closure in a diabetic animal model. Our strategy of multivalent protein presentation using nanoscale polymer conjugates has the potential to make a significant impact on the development of protein-based therapies by improving their in vivo performance.

Abstract Current anti-angiogenic therapy for the treatment of solid tumors is based on directed inhibition of growth factor signaling pathways essential for the development of new blood vessels. Despite evidence showing a positive correlation between angiogenesis and breast cancer progression, existing anti-angiogenic therapies have not proven effective at clinically managing breast tumors or prolonging patient survival. Several studies have shown that tissue microenvironment shapes local angiogenic responses and tumor progression - a finding that may partially explain the refractoriness of breast tumors to anti-angiogenic therapy. Data from our laboratory supports an anti-angiogenic role for the HoxA5 homeodomain containing transcription factor. Using the KRT14-HPV16 mouse model of skin cancer crossed with our tetracycline-regulated mouse line that expresses HoxA5 in the endothelium, we observed that HoxA5 reduced angiogenesis and slowed tumor progression in the skin. Thus, we hypothesized that constitutive endothelial expression of HoxA5 during mammary tumor development would prevent tumor growth and metastasis via modulation of the endothelial phenotype. Surprisingly, in the MMTV-PyMT mouse model of breast cancer, we observed that endothelial HoxA5 expression increased both primary tumor growth and lung metastasis. Mammary tumors from PyMT/HoxA5+ mice had larger areas of hypoxia and necrosis, as compared to primary tumors from control mice. Although we did not detect any change in intra-tumoral vascular staining (CD31+), we observed an increased number of large vessels and reduced vascular leakage in the primary tumors from PyMT/HoxA5+ mice. In contrast, subcutaneous injection of MMTV-PyMT mammary tumor cells into HoxA5 transgenic mice displayed significantly reduced tumor growth and decreased intra-tumoral vascularization, as compared to controls. This suggests that, unlike the anti-angiogenic properties of HoxA5 in the skin microenvironment, within the context of the mammary gland HoxA5 has vascular normalization effects. We conclude that the tissue microenvironment shapes the vascular response to anti-angiogenic agents and thereby controls tumor progression. Citation Format: Josette Northcott, Ileana Cuevas, Hans Layman, Nancy Boudreau. Breast tumor microenvironment shapes vascular response to endothelial HoxA5 expression. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr A07. doi:10.1158/1538-7445.CHTME14-A07

Abstract The tumor suppressor gene HOXD10 is frequently lost in breast cancer, and we have previously shown that restoring expression of this master transcriptional regulator can revert mammary tumor cells to a normal, polarized phenotype and inhibit their growth in nude mice (Carrio et al., Cancer Res., 2005). In addition, we showed that restoring HOXD10 also reduced VEGFA expression and decreased endothelial cell migration in vitro (Chen et al., Cancer Res., 2009). Considering the critical role of the immune system in mammary tumor progression and metastasis, we investigated whether Hoxd10 could also prevent breast tumor progression in an immunocompetent model. Metastatic 4T1 cell lines were transduced with Hoxd10 and were either orthotopically or intravenously injected into four to eight week old, female Balb/c mice. We observed a significant reduction in tumor burden at both primary at metastatic sites in tumors expressing Hoxd10. Immunohistochemical staining for CD31 of primary tumors expressing Hoxd10 revealed decreased angiogenesis. Flow cytometry and immunohistochemical staining also revealed a decrease in infiltrating Cd11b+Gr1+ leukocytes in Hoxd10-expressing tissues. Gene and protein analysis revealed that in addition to decreased VEGFA, HOXD10 also reduced expression of CCL2, a key chemokine linked to recruitment of Cd11B+Gr1+ leukocytes. Using an in vitro migration assay, we confirmed that the HOXD10-mediated reduction in CCL2 expression was directly linked to reduced recruitment of monocytes to tumor cells. Together, these data show that HOXD10 can stabilize the tumor microenvironment by coordinately reducing tumor cell growth, angiogenesis, leukocyte recruitment, and metastasis, and suggest a novel and comprehensive therapeutic approach to treat mammary tumors. Citation Format: Suraj Kachgal, Amy Chen, Mazen Sidani, Shahrzad Afghani, Nancy J. Boudreau. HOXD10 suppresses mammary tumor growth and metastasis coincident with decreased CD11b+Gr1+ leukocyte infiltration and angiogenesis. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 592. doi:10.1158/1538-7445.AM2014-592

Objective: Homeobox (HOX) transcription factors coordinate gene expression in wound repair and angiogenesis. Previous studies have shown that gene transfer of HoxA3 to wounds of diabetic mice accelerates wound healing, increasing angiogenesis and keratinocyte migration. In this study, we examined whether HoxA3 can also improve angiogenesis, epidermal integrity, and viability of composite skin grafts. Approach: To determine the effects of HoxA3 on composite skin grafts, we constructed bilayered composite grafts incorporating fibroblasts engineered to constitutively secrete HoxA3. We then transplanted these composite grafts in vivo. Results: The composite grafts produced a stratified epidermal layer after seventeen days in culture and following transplantation in vivo, these grafts exhibit normal epidermal differentiation and reduced contraction compared to controls. In addition, HoxA3 grafts showed increased angiogenesis. Quantitative polymerase chain reaction (PCR) analyses of HoxA3 graft tissue reveal an increase in the downstream HoxA3 target genes MMP-14 and uPAR expression, as well as a reduction in CCL-2 and CxCl-12. Innovation: Expression of secreted HoxA3 in composite grafts represents a comprehensive approach that targets both keratinocytes and endothelial cells to promote epidermal proliferation and angiogenesis. Conclusion: Secreted HoxA3 improves angiogenesis, reduces expression of inflammatory mediators, and prolongs composite skin graft integrity.