Exosomes secreted by prostate cancer cells under hypoxia promote matrix metalloproteinases activity at pre-metastatic niches

Pathways and outputs orchestrated in tumor microenvironment cells by hypoxia-induced tumor-derived exosomes in pan-cancer

Hypoxia is a critical microenvironmental condition that plays a major role in driving tumorigenesis and cancer progression. Increasing evidence has revealed novel functions of hypoxia in intercellular communication. The hypoxia induced tumor derived exosomes (hiTDExs) released in high quantities by tumor cells under hypoxia are packed with unique cargoes that are essential for cancer cells' interactions within their microenvironment. These hiTDExs facilitate not only immune evasion but also promote cancer cell growth, survival, angiogenesis, EMT, resistance to therapy, and the metastatic spread of the disease. Nevertheless, direct interventions targeting hypoxia signaling in cancer therapy face challenges related to tumor progression and resistance, limiting their clinical effectiveness. Therefore, deepening our understanding of the molecular processes through which hiTDExs remodels tumors and their microenvironment, as well as how tumor cells adjust to hypoxic conditions, remains essential. This knowledge will pave the way for novel approaches in treating hypoxic tumors. In this review, we discuss recent work revealing the hiTDExs mediated interactions between tumor and its microenvironment. We have described key hiTDExs cargos (lncRNA, circRNAs, cytokines, etc.) and their targets in the receipt cells, responsible for various biological effects. Moreover, we emphasized the importance of hiTDExs as versatile elements of cell communication in the tumor microenvironment. Finally, we highlighted the effects of hiTDExs on the molecular changes in target cells by executing molecular cargo transfer between cells and altering signaling pathways. Currently, hiTDExs show promise in the treatment of diseases. Understanding the molecular processes through which hiTDExs influence tumor behavior and their microenvironment, along with how tumor cells adapt to and survive in low-oxygen conditions, remains a central focus in cancer research, paving the way for innovative strategies in treating hypoxic tumors and enhancing immunotherapy.

Effect of hypoxia on extracellular vesicles in malignant and non-malignant conditions

Extracellular vesicles (EVs) are produced by virtually all types of cells and can be detected in nearly all extracellular places. These particles mediate intercellular communication and transfer their cargo to the recipient cells, inducing a variety of processes in these cells through transmission of several biomolecules such as miRNAs, lncRNAs, other transcripts and a variety of proteins. It has been documented that size, quantity, and expression of biomolecules in the EVs are influenced by the level of oxygen. In fact, hypoxia can affect several cellular processes through modulation of the cargo of these vesicles. Hypoxic exosomes derived from tumor cells have several protumoral effects on the recipient cells, including enhancement of proliferation, migration, and invasion in other tumoral cells, induction of metastasis in distant organs, stimulation of angiogenesis in the endothelial cells, and modulation of macrophage polarization. Hypoxic EVs also contribute to several non-malignant diseases. This review summarizes the effect of hypoxia on EVs cargo in malignant and nonmalignant diseases of different organs.

Stress-induced extracellular vesicles: insight into their altered proteomic composition and probable physiological role in cancer

EVs (extracellular vesicles) are phospholipid bilayer vesicles that can be released by both prokaryotic and eukaryotic cells in normal as well as altered physiological conditions. These vesicles also termed as signalosomes, possess a distinctive cargo comprising nucleic acids, proteins, lipids, and metabolites, enabling them to play a pivotal role in both local and long-distance intercellular communication. The composition, origin, and release of EVs can be influenced by different physiological conditions and a variety of stress factors, consequently affecting the contents carried within these vesicles. Therefore, identifying the modified contents of EVs can provide valuable insights into their functional role in stress-triggered communication. Particularly, this is important when EVs released from tumor microenvironment are investigated for their role in the development and dissemination of cancer. This review article emphasizes the importance of differential EV shedding and altered proteomic content in response to reduced oxygen concentration, altered levels of glucose and glutamine, pH variations, oxidative stress and Ca2+ ion concertation and it is subsequent effects on the behavior of recipient cells.

Small extracellular vesicles: crucial mediators for prostate cancer

Small extracellular vesicles (sEVs) play a critical role in the progression, diagnosis, and treatment of prostate cancer (PCa), particularly within the tumor microenvironment (TME). Acting as novel biomarkers and agents for targeted biological therapy, sEVs contribute significantly to improving patient survival. These vesicles transport a variety of biomolecules, including proteins, nucleic acids, and lipids, which are instrumental in remodeling the TME, facilitating intercellular communication, and influencing key processes such as tumor growth, metastasis, and therapy resistance. A thorough understanding of sEV heterogeneity, including their biogenesis, characteristics, and potential applications, is essential. Recent advances have illuminated the origins, formation processes, and molecular cargo of PCa-derived sEVs (PCa-sEVs), enhancing our understanding of their role in disease progression. Furthermore, sEVs show promise as diagnostic markers, with potential applications in early detection and prognostic assessment in PCa. Therapeutically, natural and engineered sEVs offer versatile applications, including drug delivery, gene therapy, and immunomodulation, underscoring their potential in PCa management. This review delves into the substantial potential of sEVs in clinical practices for PCa.

Extracellular vesicles in cancer´s communication: messages we can read and how to answer

Extracellular vesicles (EVs) are emerging as critical mediators of intercellular communication in the tumor microenvironment (TME), profoundly influencing cancer progression. These nano-sized vesicles, released by both tumor and stromal cells, carry a diverse cargo of proteins, nucleic acids, and lipids, reflecting the dynamic cellular landscape and mediating intricate interactions between cells. This review provides a comprehensive overview of the biogenesis, composition, and functional roles of EVs in cancer, highlighting their significance in both basic research and clinical applications. We discuss how cancer cells manipulate EV biogenesis pathways to produce vesicles enriched with pro-tumorigenic molecules, explore the specific contributions of EVs to key hallmarks of cancer, such as angiogenesis, metastasis, and immune evasion, emphasizing their role in shaping TME and driving therapeutic resistance. Concurrently, we submit recent knowledge on how the cargo of EVs can serve as a valuable source of biomarkers for minimally invasive liquid biopsies, and its therapeutic potential, particularly as targeted drug delivery vehicles and immunomodulatory agents, showcasing their promise for enhancing the efficacy and safety of cancer treatments. By deciphering the intricate messages carried by EVs, we can gain a deeper understanding of cancer biology and develop more effective strategies for early detection, targeted therapy, and immunotherapy, paving the way for a new era of personalized and precise cancer medicine with the potential to significantly improve patient outcomes.

Effects of small extracellular vesicles derived from normoxia- and hypoxia-treated prostate cancer cells on the submandibular salivary gland epithelium in vitro

Small extracellular vesicles (sEVs) are an important part of intercellular communication. They are phospholipid bilayer particles that carry active biomolecules such as proteins, various nucleic acids, and lipids. In recipient cells, sEVs can alter cellular functions, including cancer development and premetastatic niche formation in distant organs. Moreover, sEVs can carry cancer-specific features, which makes them promising biomarker candidates. However, the interactions of sEVs with biological barriers and consequences thereof, are not clarified yet. The blood-saliva barrier is crucial for preventing the entry of pathogens and (in)organic substances into the bloodstream, as well as molecule filtration from blood to saliva. The effects of brain derived DU145 prostate cancer (PCa) sEVs on a human submandibular salivary gland barrier (SSGB) in vitro were investigated. Small EVs were harvested from normoxic (N, atmospheric O2) or hypoxic (H, 1% O2) conditions, fluorescently labeled with CellTrackerTM Orange and thoroughly characterized. HTB-41 B2 cells were used as SSGB model cultured on 24-well ThinCert® inserts. After model optimization indicating effects of serum and serum-sEVs on barrier properties, PCa sEVs were applied to the basolateral (blood) side in either 10% serum, or serum-free conditions, and barrier integrity was continuously monitored for 40 hours. This study found that H and N PCa sEVs were uptaken by the SSGB in vitro model in similar quantities regardless of the media composition in the basolateral compartment. Permeation of fluorescent PCa sEVs into the apical compartment was not detectable with the applied methods. However, treatment with H and N sEVs under different serum conditions revealed distinct molecular clusters after hierarchical analysis of mRNA data measured by high-throughput qPCR, which were partly reflected at the protein level. For example, serum-reduction dependent decrease of barrier properties was accompanied with the decrease of CDH1 or Claudin-7 expression. Interestingly, the presence of H sEVs significantly increased the number of sEV-sized particles in the apical compartment of the SSGB model compared to basolaterally added N sEVs. This functional effect on the number of particles in the saliva (apical) compartment induced by different sEVs applied in the blood (basolateral) compartment might be a new approach to understand one possible mechanism how differences of salivary EVs might occur which then could be used as biomarker.

The interplay between the tumor microenvironment and tumor-derived small extracellular vesicles in cancer development and therapeutic response

The tumor microenvironment (TME) plays an essential role in tumor cell survival by profoundly influencing their proliferation, metastasis, immune evasion, and resistance to treatment. Extracellular vesicles (EVs) are small particles released by all cell types and often reflect the state of their parental cells and modulate other cells' functions through the various cargo they transport. Tumor-derived small EVs (TDSEVs) can transport specific proteins, nucleic acids and lipids tailored to propagate tumor signals and establish a favorable TME. Thus, the TME's biological characteristics can affect TDSEV heterogeneity, and this interplay can amplify tumor growth, dissemination, and resistance to therapy. This review discusses the interplay between TME and TDSEVs based on their biological characteristics and summarizes strategies for targeting cancer cells. Additionally, it reviews the current issues and challenges in this field to offer fresh insights into comprehending tumor development mechanisms and exploring innovative clinical applications.

Exosomal microRNAs in cancer metastasis: A bridge between tumor micro and macroenvironment

Malignant tumors are complicated structures of cancer cells that are constantly in communication with their local and distant environment. Exosomes are released by tumor cells and can facilitate the cell-cell interaction within the local microenvironment and the primary tumor. In fact, exosomes are secreted by both tumor and non-tumor cells, to provide a mutual communication network between cells and their micro- and/or macro-environments. Exososmes can contain a variety of biological cargos mostly based on their originated cells. Uptake of these exosomes by their recipient cells results in the alterations that their cargo can exert. MicroRNAs are identified as one of the most critical exosomal components, considering their pivotal regulatory roles in distinct biological process, including metastasis. Release and absorbance of exosomal microRNAs is possible by various cells within the host, and can have distinct biological consequences. Therefore, in this review we will discuss the role of exosomal microRNAs derived from tumor cells and untransformed cells within their micro- and macroenvironment in cancer progression and metastasis.

Prognostic Value of PlGF Upregulation in Prostate Cancer

BACKGROUND

Prostate cancer (PCa) is the second most commonly diagnosed cancer in men worldwide, with metastasis, particularly to bone, being the primary cause of mortality. Currently, prognostic markers like PSA levels and Gleason classification are limited in predicting metastasis, emphasizing the need for novel clinical biomarkers. New molecules predicting tumor progression have been identified over time. Some, such as the immune checkpoint inhibitors (ICIs) PD-1/PD-L1, have become valid markers as theranostic tools essential for prognosis and drug target therapy. However, despite the success of ICIs as an anti-cancer therapy for solid tumors, their efficacy in treating bone metastases has mainly proven ineffective, suggesting intrinsic resistance to this therapy in the bone microenvironment. This study explores the potential of immunological intratumoral biomarkers, focusing on placental growth factor (PlGF), Vascular Endothelial Growth Factor Receptor 1 (VEGFR1), and Programmed Cell Death Protein 1 (PD-1), in predicting bone metastasis formation.

METHODS

we analyzed PCa samples from patients with and without metastasis by immunohistochemical analysis.

RESULTS

Results revealed that PlGF expression is significantly higher in primary tumors of patients that developed metastasis within five years from the histological diagnosis. Additionally, PlGF expression correlates with increased VEGFR1 and PD-1 levels, as well as the presence of intratumoral M2 macrophages.

CONCLUSIONS

These findings suggest that PlGF contributes to an immunosuppressive environment, thus favoring tumor progression and metastatic process. Results here highlight the potential of integrating these molecular markers with existing prognostic tools to enhance the accuracy of metastasis prediction in PCa. By identifying patients at risk for metastasis, clinicians can tailor treatment strategies more effectively, potentially improving survival outcomes and quality of life. This study underscores the importance of further research into the role of intratumoral biomarkers in PCa management.

Aspirin alleviates fibronectin-induced preeclampsia phenotypes in a mouse model and reverses fibronectin-mediated trophoblast invasiveness under hypoxia by regulating ciliogenesis and Akt and MAPK signaling

The placenta experiences a low-oxygen stage during early pregnancy. Aspirin is an effective preventative treatment for preeclampsia if applied early in pregnancy. Elevation of fibronectin (FN) level has been reported to be associated with preeclampsia; however, the role of FN in the physiological hypoxic phase and whether aspirin exerts its effect on FN at this hypoxic stage remain unknown. We determined pregnancy outcomes by injecting saline or recombinant FN protein into C57BL/6 pregnant mice and one group of FN-injected mice was fed aspirin. The effects of FN, the underlying pathways on trophoblast biology, and cilia formation under hypoxia were investigated in FN-pretreated or FN-knockdown HTR-8/SVneo cells in a hypoxic chamber (0.1 % O2). Preeclampsia-like phenotypes, including blood pressure elevation and proteinuria, developed in FN-injected pregnant mice. The fetal weight of FN-injected mice was significantly lower than that of non-FN-injected mice (p < 0.005). Trophoblast FN expression was upregulated under hypoxia, which could be suppressed by aspirin treatment. FN inhibited trophoblast invasion and migration under hypoxia, and this inhibitory effect occurred through downregulating ZEB1/2, MMP 9 and the Akt and MAPK signaling pathways. Ciliogenesis of trophoblasts was stimulated under hypoxia but was inhibited by FN treatment. Aspirin was shown to reverse the FN-mediated inhibitory effect on trophoblast invasion/migration and ciliogenesis. In conclusion, FN overexpression induces preeclampsia-like symptoms and impairs fetal growth in mice. Aspirin may exert its suppressive effect on FN upregulation and FN-mediated cell function in the hypoxic stage of pregnancy and therefore provides a preventative effect on preeclampsia development.

Exosomes: a significant medium for regulating drug resistance through cargo delivery

Exosomes are small lipid nanovesicles with a diameter of 30-150 nm. They are present in all body fluids and are actively secreted by the majority of cells through the process of exocytosis. Exosomes play an essential role in intercellular communication and act as significant molecular carriers in regulating various physiological and pathological processes, such as the emergence of drug resistance in tumors. Tumor-associated exosomes transfer drug resistance to other tumor cells by releasing substances such as multidrug resistance proteins and miRNAs through exosomes. These substances change the cell phenotype, making it resistant to drugs. Tumor-associated exosomes also play a role in impacting drug resistance in other cells, like immune cells and stromal cells. Exosomes alter the behavior and function of these cells to help tumor cells evade immune surveillance and form a tumor niche. In addition, exosomes also export substances such as tumoricidal drugs and neutralizing antibody drugs to help tumor cells resist drug therapy. In this review, we summarize the mechanisms of exosomes in promoting drug resistance by delivering cargo in the context of the tumor microenvironment (TME).

Extracellular vesicle and lipoprotein diagnostics (ExoLP-Dx) with membrane sensor: A robust microfluidic platform to overcome heterogeneity

The physiological origins and functions of extracellular vesicles (EVs) and lipoproteins (LPs) propel advancements in precision medicine by offering non-invasive diagnostic and therapeutic prospects for cancers, cardiovascular, and neurodegenerative diseases. However, EV/LP diagnostics (ExoLP-Dx) face considerable challenges. Their intrinsic heterogeneity, spanning biogenesis pathways, surface protein composition, and concentration metrics complicate traditional diagnostic approaches. Commonly used methods such as nanoparticle tracking analysis, enzyme-linked immunosorbent assay, and nuclear magnetic resonance do not provide any information about their proteomic subfractions, including active proteins/enzymes involved in essential pathways/functions. Size constraints limit the efficacy of flow cytometry for small EVs and LPs, while ultracentrifugation isolation is hampered by co-elution with non-target entities. In this perspective, we propose a charge-based electrokinetic membrane sensor, with silica nanoparticle reporters providing salient features, that can overcome the interference, long incubation time, sensitivity, and normalization issues of ExoLP-Dx from raw plasma without needing sample pretreatment/isolation. A universal EV/LP standard curve is obtained despite their heterogeneities.

Revisiting the role of mesenchymal stromal cells in cancer initiation, metastasis and immunosuppression

Immune checkpoint blockade (ICB) necessitates a thorough understanding of intricate cellular interactions within the tumor microenvironment (TME). Mesenchymal stromal cells (MSCs) play a pivotal role in cancer generation, progression, and immunosuppressive tumor microenvironment. Within the TME, MSCs encompass both resident and circulating counterparts that dynamically communicate and actively participate in TME immunosurveillance and response to ICB. This review aims to reevaluate various facets of MSCs, including their potential self-transformation to function as cancer-initiating cells and contributions to the creation of a conducive environment for tumor proliferation and metastasis. Additionally, we explore the immune regulatory functions of tumor-associated MSCs (TA-MSCs) and MSC-derived extracellular vesicles (MSC-EVs) with analysis of potential connections between circulating and tissue-resident MSCs. A comprehensive understanding of the dynamics of MSC-immune cell communication and the heterogeneous cargo of tumor-educated versus naïve MSCs may unveil a new MSC-mediated immunosuppressive pathway that can be targeted to enhance cancer control by ICB.

Applications of Urinary Extracellular Vesicles in the Diagnosis and Active Surveillance of Prostate Cancer

Prostate cancer is the most common non-cutaneous cancer among men in the UK, causing significant health and economic burdens. Diagnosis and risk prognostication can be challenging due to the genetic and clinical heterogeneity of prostate cancer as well as uncertainties in our knowledge of the underlying biology and natural history of disease development. Urinary extracellular vesicles (EVs) are microscopic, lipid bilayer defined particles released by cells that carry a variety of molecular cargoes including nucleic acids, proteins and other molecules. Urine is a plentiful source of prostate-derived EVs. In this narrative review, we summarise the evidence on the function of urinary EVs and their applications in the evolving field of prostate cancer diagnostics and active surveillance. EVs are implicated in the development of all hallmarks of prostate cancer, and this knowledge has been applied to the development of multiple diagnostic tests, which are largely based on RNA and miRNA. Common gene probes included in multi-probe tests include PCA3 and ERG, and the miRNAs miR-21 and miR-141. The next decade will likely bring further improvements in the diagnostic accuracy of biomarkers as well as insights into molecular biological mechanisms of action that can be translated into opportunities in precision uro-oncology.

Exosomes promote pre-metastatic niche formation in colorectal cancer

It is well known that colorectal cancer (CRC) has a high morbidity rate, a poor prognosis when metastasized, and a greatly shortened 5-year survival rate. Therefore, understanding the mechanism of tumor metastasis is still important. Based on the "seed and soil" theory, the concept of " premetastatic niche (PMN)" was introduced by Kaplan et al. The complex interaction between primary tumors and the metastatic organ provides a beneficial microenvironment for tumor cells to colonize at a distance. With further exploration of the PMN, exosomes have gradually attracted interest from researchers. Exosomes are extracellular vesicles secreted from cells that include various biological information and are involved in communication between cells. As a key molecule in the PMN, exosomes are closely related to tumor metastasis. In this article, we obtained information by conducting a comprehensive search across academic databases including PubMed and Web of Science using relevant keywords. Only recent, peer-reviewed articles published in the English language were considered for inclusion. This study aims to explore in depth how exosomes promote the formation of pre-metastatic microenvironment (PMN) in colorectal cancer and its related mechanisms.

Extracellular vesicle-mediated pre-metastatic niche formation via altering host microenvironments

The disordered growth, invasion and metastasis of cancer are mainly attributed to bidirectional cell-cell interactions. Extracellular vesicles (EVs) secreted by cancer cells are involved in orchestrating the formation of pre-metastatic niches (PMNs). Tumor-derived EVs mediate bidirectional communication between tumor and stromal cells in local and distant microenvironments. EVs carrying mRNAs, small RNAs, microRNAs, DNA fragments, proteins and metabolites determine metastatic organotropism, enhance angiogenesis, modulate stroma cell phenotypes, restructure the extracellular matrix, induce immunosuppression and modify the metabolic environment of organs. Evidence indicates that EVs educate stromal cells in secondary sites to establish metastasis-supportive microenvironments for seeding tumor cells. In this review, we provide a comprehensive overview of PMN formation and the underlying mechanisms mediated by EVs. Potential approaches to inhibit cancer metastasis by inhibiting the formation of PMNs are also presented.

The role of matrix metalloproteinase-2 in the metastatic cascade: a review

Matrix metalloproteinase-2 (MMP-2) is a gelatinase and is involved in multiple steps of the metastatic cascade. More than a decade ago an increased expression of MMP-2 in tumour cells or higher serum levels was reported to be a prognostic biomarker for a lower disease-free and overall survival rate. In recent years new evidence has indicated that MMP-2 has an important role in the tumour ecosystem. It is one of the many players in the onco-sphere, involved in interacting between tumour cells, host cells and the microenvironment. It plays a role in the dissemination of tumour cells, the epithelial–mesenchymal and mesenchymal–epithelial transitions, the formation of the pre-metastatic and metastatic niches, dormancy of tumour cells and modulating the immune system. The aim of this review is to highlight these multiple roles in the metastatic cascade and how many signalling pathways can up or down-regulate MMP-2 activity in the different stages of cancer progression and the effect of MMP-2 on the onco-sphere. Research in head and neck cancer is used as an example of these processes. The use of non-specific MMP inhibitors has been unsuccessful showing only limited benefits and associated with high toxicity as such that none have progressed past Phase III trials. Preclinical trials are undergoing using antibodies directed against specific matrix metalloproteinases, these targeted therapies may be potentially less toxic to the patients.

Prostate cancer-derived small extracellular vesicle proteins: the hope in diagnosis, prognosis, and therapeutics

Current diagnostic tools for prostate cancer (PCa) diagnosis and risk stratification are insufficient. The hidden onset and poor efficacy of traditional therapies against metastatic PCa make this disease a heavy burden in global men's health. Prostate cancer-derived extracellular vesicles (PCDEVs) have garnered attention in recent years due to their important role in communications in tumor microenvironment. Recent advancements have demonstrated PCDEVs proteins play an important role in PCa invasion, progression, metastasis, therapeutic resistance, and immune escape. In this review, we briefly discuss the applications of sEV proteins in PCa diagnosis and prognosis in liquid biopsy, focus on the roles of the PCa-derived small EVs (sEVs) proteins in tumor microenvironment associated with cancer progression, and explore the therapeutic potential of sEV proteins applied for future metastatic PCa therapy.

Extracellular Vesicles: Biological Packages That Modulate Tumor Cell Invasion

Tumor progression, from early-stage invasion to the formation of distal metastases, relies on the capacity of tumor cells to modify the extracellular matrix (ECM) and communicate with the surrounding stroma. Extracellular vesicles (EVs) provide an important means to regulate cell invasion due to the selective inclusion of cargoes such as proteases and matrix proteins into EVs that can degrade or modify the ECM. EVs have also been shown to facilitate intercellular communication in the tumor microenvironment through paracrine signaling, which can impact ECM invasion by cancer cells. Here, we describe the current knowledge of EVs as facilitators of tumor invasion by virtue of their effects on proteolytic degradation and modification of the ECM, their ability to educate the stromal cells in the tumor microenvironment, and their role as mediators of long-range communication aiding in cell invasion and matrix remodeling at secondary sites.

Hypoxic regulation of extracellular vesicles: Implications for cancer therapy

Extracellular vesicles (EVs) play a pivotal role in intercellular communication and have been implicated in cancer progression. Hypoxia, a pervasive hallmark of cancer, is known to regulate EV biogenesis and function. Hypoxic EVs contain a specific set of proteins, nucleic acids, lipids, and metabolites, capable of reprogramming the biology and fate of recipient cells. Enhancing the intrinsic therapeutic efficacy of EVs can be achieved by strategically modifying their structure and contents. Moreover, the use of EVs as drug delivery vehicles holds great promise for cancer treatment. However, various hurdles must be overcome to enable their clinical application as cancer therapeutics. In this review, we aim to discuss the current knowledge on the hypoxic regulation of EVs. Additionally, we will describe the underlying mechanisms by which EVs contribute to cancer progression in hypoxia and outline the progress and limitations of hypoxia-related EV therapeutics for cancer.

Role of exosomes in prostate cancer bone metastasis

Bone is a preferred metastatic site of prostate cancer (PCa), and most patients with PCa metastases develop osteogenic bone metastasis, which manifests as disturbed bone structure and poor bone quality. However, the underlying mechanisms of PCa bone metastasis remain unclear. In recent years, increasing evidence has implicated extracellular vesicles, especially exosomes, in PCa bone metastasis. Exosomes are 30-150 nm in diameter, enclosing a cargo of biomolecules, such as DNA, RNA, and proteins. Exosomes play a functional role in intercellular communication, modulate the functions of recipient cells, and potentially modulate bone microenvironment changes, thereby influencing the development of PCa bone metastasis. This review summarizes the involvement of exosomes in the imbalance between bone resorption and formation, and establishing a pre-metastatic niche in bone marrow, as well as potential clinical applications of exosomes in therapeutic strategies for treating patients with advanced PCa with bone metastasis.

Cellular and molecular characteristics of the premetastatic niches

The premetastatic niches (PMN) formed by primary tumor-derived molecules regulate distant organs and tissues to further favor tumor colonization. Targeted PMN therapy may prevent tumor metastasis in the early stages, which is becoming increasingly important. At present, there is a lack of in-depth understanding of the cellular and molecular characteristics of the PMN. Here, we summarize current research advances on the cellular and molecular characteristics of the PMN. We emphasize that PMN intervention is a potential therapeutic strategy for early prevention of tumor metastasis, which provides a promising basis for future research and clinical application.

Calcium signalling pathways in prostate cancer initiation and progression

Cancer cells proliferate, differentiate and migrate by repurposing physiological signalling mechanisms. In particular, altered calcium signalling is emerging as one of the most widespread adaptations in cancer cells. Remodelling of calcium signalling promotes the development of several malignancies, including prostate cancer. Gene expression data from in vitro, in vivo and bioinformatics studies using patient samples and xenografts have shown considerable changes in the expression of various components of the calcium signalling toolkit during the development of prostate cancer. Moreover, preclinical and clinical evidence suggests that altered calcium signalling is a crucial component of the molecular re-programming that drives prostate cancer progression. Evidence points to calcium signalling re-modelling, commonly involving crosstalk between calcium and other cellular signalling pathways, underpinning the onset and temporal progression of this disease. Discrete alterations in calcium signalling have been implicated in hormone-sensitive, castration-resistant and aggressive variant forms of prostate cancer. Hence, modulation of calcium signals and downstream effector molecules is a plausible therapeutic strategy for both early and late stages of prostate cancer. Based on this premise, clinical trials have been undertaken to establish the feasibility of targeting calcium signalling specifically for prostate cancer.

Weaving the nest: extracellular matrix roles in pre-metastatic niche formation

The discovery that primary tumors condition distant organ sites of future metastasis for seeding by disseminating tumor cells through a process described as the pre-metastatic niche (PMN) formation revolutionized our understanding of cancer progression and opened new avenues for therapeutic interventions. Given the inherent inefficiency of metastasis, PMN generation is crucial to ensure the survival of rare tumor cells in the otherwise hostile environments of metastatic organs. Early on, it was recognized that preparing the "soil" of the distal organ to support the outgrowth of metastatic cells is the initiating event in PMN development, achieved through the remodeling of the organ's extracellular matrix (ECM). Remote restructuring of ECM at future sites of metastasis under the influence of primary tumor-secreted factors is an iterative process orchestrated through the crosstalk between resident stromal cells, such as fibroblasts, epithelial and endothelial cells, and recruited innate immune cells. In this review, we will explore the ECM changes, cellular effectors, and the mechanisms of ECM remodeling throughout PMN progression, as well as its impact on shaping the PMN and ultimately promoting metastasis. Moreover, we highlight the clinical and translational implications of PMN ECM changes and opportunities for therapeutically targeting the ECM to hinder PMN formation.

The impact of hypoxia on extracellular vesicle secretome profile of cancer

Extracellular vesicles (EVs) are emerging as key mediators of cell-to-cell communications and signal transporters between tumor and stroma, and hypoxia is a critical characteristic of tumor microenvironment (TME) in solid cancers. Hypoxia stimulates tumor cells to generate and secrete more EVs, and the EVs shed from cancer transfer biological information to boost hypoxia and hypoxia inducible factor (HIF) functionality. Hypoxia alters EV secretome profile to carry pro-tumorigenic factors for promoting numerous tumor-related processes including increased cancer cell proliferation and survival, immune escape, aberrant angiogenesis, and invasion and metastasis. Exosomal hypoxia inducible factor (HIF)-1α is an essential driver of epithelial-mesenchymal transition (EMT) and stemness profile in cancer. Hypoxic cancer-derived EVs are also contributed to therapy resistance. In fact, EVs are messengers of hypoxic tolerance in cancer, which enable adaptation of tumor cells to changes occurring within TME for their further resistance and metastasis. Tracing EVs shed from hypoxic tumor cells into plasma provide important information about the genomic signature of cancer. In this review, we aimed to discuss about key tumorigenic events promoted by inter-connections between hypoxia and EVs, mainly exosomes, secreted into tumor area focusing on key hallmarks of cancer.

Immune determinants of the pre-metastatic niche

Primary tumors actively and specifically prime pre-metastatic niches (PMNs), the future sites of organotropic metastasis, preparing these distant microenvironments for disseminated tumor cell arrival. While initial studies of the PMN focused on extracellular matrix alterations and stromal reprogramming, it is increasingly clear that the far-reaching effects of tumors are in great part achieved through systemic and local PMN immunosuppression. Here, we discuss recent advances in our understanding of the tumor immune microenvironment and provide a comprehensive overview of the immune determinants of the PMN's spatiotemporal evolution. Moreover, we depict the PMN immune landscape, based on functional pre-clinical studies as well as mounting clinical evidence, and the dynamic, reciprocal crosstalk with systemic changes imposed by cancer progression. Finally, we outline emerging therapeutic approaches that alter the dynamics of the interactions driving PMN formation and reverse immunosuppression programs in the PMN ensuring early anti-tumor immune responses.

Cancer stem cell in prostate cancer progression, metastasis and therapy resistance

Prostate cancer (PCa) is the most diagnosed malignancy in the men worldwide. Cancer stem cells (CSCs) are the sub-population of cells present in the tumor which possess unique properties of self-renewal and multilineage differentiation thus thought to be major cause of therapy resistance, disease relapse, and mortality in several malignancies including PCa. CSCs have also been shown positive for the common stem cells markers such as ALDH EZH2, OCT4, SOX2, c-MYC, Nanog etc. Therefore, isolation and characterization of CSCs specific markers which may discriminate CSCs and normal stem cells are critical to selectively eliminate CSCs. Rapid advances in the field offers a theoretical explanation for many of the enduring uncertainties encompassing the etiology and an optimism for the identification of new stem-cell targets, development of reliable and efficient therapies in the future. The emerging reports have also provided unprecedented insights into CSCs plasticity, quiescence, renewal, and therapeutic response. In this review, we discuss the identification of PCa stem cells, their unique properties, stemness-driving pathways, new diagnostics, and therapeutic interventions.

Breast Cancer Exosomal microRNAs Facilitate Pre-Metastatic Niche Formation in the Bone: A Mathematical Model

Pre-metastatic niche is a location where cancer cells, separating from a primary tumor, find "fertile soil" for growth and proliferation, ensuring successful metastasis. Exosomal miRNAs of breast cancer are known to enter the bone and degrade it, which facilitates cancer cells invasion into the bone interior and ensures its successful colonization. In this paper, we use a mathematical model to first describe, in health, the continuous remodeling of the bone by bone-forming osteoblasts, bone-resorbing osteoclasts and the RANKL-OPG-RANK signaling system, which keeps the balance between bone formation and bone resorption. We next demonstrate how breast cancer exosomal miRNAs disrupt this balance, either by increasing or by decreasing the ratio of osteoclasts/osteoblasts, which results in abnormal high bone resorption or abnormal high bone forming, respectively, and in bone weakening in both cases. Finally we consider the case of abnormally high resorption and evaluate the effect of drugs, which may increase bone density to normal level, thus protecting the bone from invasion by cancer cells.

90 K increased delivery efficiency of extracellular vesicles through mediating internalization

Using mass spectrometry-based high-throughput proteomics, we identified a membrane protein on extracellular vesicles (EVs), 90 K, which predicts poor overall survival of patients with head and neck cancer. 90 K levels in serum EVs could serve as an independent factor for poor prognosis of patients with head and neck cancer. Pre-treatment of immune competent mice with tumor-derived EVs (TDEs) elicited an immune-suppressive microenvironment for tumor cells, which was regulated by 90 K. The immunosuppressive function of TDE-90 K depends on the presence of myeloid derived suppressor cells (MDSCs) rather than regulatory T cells. The immune regulatory role of TDEs on MDSCs depends on miR-21 which is encapsulated in TDEs. Moreover, 90 K is required for the internalization of TDE cargo though interacting with integrin-β1 and anti-siglec-9 rather than directly affecting the immune function of MDSCs. 90 K modification of γδT cell-derived EVs (γδTEVs) could increase the delivery efficiency and therapeutic effect of PD-L1 siRNA by γδTEVs. We concluded that as a secreted protein modulating cell-cell and cell-matrix interactions, 90 K can be carried by TDEs to mediate the internalization and delivery of TDEs cargo by recipient cells. This function of 90 K could be utilized to improve the efficiency of EV-based drug delivery.

Message in the bottle: regulation of the tumor microenvironment via exosome-driven proteolysis

Exosomes comprise a subtype of extracellular vesicles involved in cell-to-cell communication, specifically by transporting biological molecules, such as proteins and nucleic acids, to either local or more distant recipient cells, thus triggering distinct biological behaviors. Included in the exosome cargo is frequently a wide range of proteolytic enzymes, such as the matrix metalloproteinases (MMPs), the disintegrin and metalloproteinases (ADAMs), and the ADAM with thrombospondin-like motifs (ADAMTSs), whose functions contribute to the development and progression of cancer. In recent years, extensive research on the potential use of exosomes in diagnostic and therapeutic applications for personalized medicine has emerged, but the targeting of the proteolytic cargo of exosomes has not been fully exploited in this direction. In this review, we aim to explore both the mechanistic and the translational importance of proteolytic enzymes carried by the tumor cell-derived exosomes, as well as their role in the acquisition and support of certain hallmarks of cancer.

Role of the Hypoxic-Secretome in Seed and Soil Metastatic Preparation

During tumor growth, the delivery of oxygen to cells is impaired due to aberrant or absent vasculature. This causes an adaptative response that activates the expression of genes that control several essential processes, such as glycolysis, neovascularization, immune suppression, and the cancer stemness phenotype, leading to increased metastasis and resistance to therapy. Hypoxic tumor cells also respond to an altered hypoxic microenvironment by secreting vesicles, factors, cytokines and nucleic acids that modify not only the immediate microenvironment but also organs at distant sites, allowing or facilitating the attachment and growth of tumor cells and contributing to metastasis. Hypoxia induces the release of molecules of different biochemical natures, either secreted or inside extracellular vesicles, and both tumor cells and stromal cells are involved in this process. The mechanisms by which these signals that can modify the premetastatic niche are sent from the primary tumor site include changes in the extracellular matrix, recruitment and activation of different stromal cells and immune or nonimmune cells, metabolic reprogramming, and molecular signaling network rewiring. In this review, we will discuss how hypoxia might alter the premetastatic niche through different signaling molecules.

[Prostate and breast cancer: similarities and differences]

Prostate and breast carcinomas are amongst the most common new diseases in men and women, with steadily rising incidences. In addition to the significant health consequences, both diseases also lead to a significantly reduced quality of life due to their influence on sexual function. The aim of this work is to identify scientific approaches and research priorities that in the future might lead to synergies in both disciplines by specifically considering the similarities and differences between the two diseases. For this purpose, clinically relevant aspects such as risk factors, treatment options, as well as scientific similarities and differences that offer direct joint research approaches in the areas of cultivation and modeling of both tumor entities were analyzed. Through this approach, we were able to demonstrate that due to the comparable biology of the two diseases and the underlying mechanisms, scientific synergies may certainly lead to targeted research. Clinical similarities also indicate that close collaboration between the two disciplines could lead to improved treatment of our patients. Evidence deficiencies in both diseases (e.g. the metastasis mechanisms of both tumor entities) and controversially discussed aspects such as risk factors clearly show that further scientific projects for a more detailed understanding of both diseases are necessary to ensure future success in the treatment of our patients.

Extracellular vesicles and particles impact the systemic landscape of cancer

Intercellular cross talk between cancer cells and stromal and immune cells is essential for tumor progression and metastasis. Extracellular vesicles and particles (EVPs) are a heterogeneous class of secreted messengers that carry bioactive molecules and that have been shown to be crucial for this cell-cell communication. Here, we highlight the multifaceted roles of EVPs in cancer. Functionally, transfer of EVP cargo between cells influences tumor cell growth and invasion, alters immune cell composition and function, and contributes to stromal cell activation. These EVP-mediated changes impact local tumor progression, foster cultivation of pre-metastatic niches at distant organ-specific sites, and mediate systemic effects of cancer. Furthermore, we discuss how exploiting the highly selective enrichment of molecules within EVPs has profound implications for advancing diagnostic and prognostic biomarker development and for improving therapy delivery in cancer patients. Altogether, these investigations into the role of EVPs in cancer have led to discoveries that hold great promise for improving cancer patient care and outcome.

Formation of pre-metastatic bone niche in prostate cancer and regulation of traditional chinese medicine

Prostate cancer with bone metastasis has a high cancer-specific mortality. Thus, it is essential to delineate the mechanism of bone metastasis. Pre-metastatic niche (PMN) is a concept in tumor metastasis, which is characterized by tumor-secreted factors, reprogramming of stromal cells, and immunosuppression by myeloid-derived suppressor cells (MDSC), which is induced by bone marrow-derived cells (BMDC) in the target organ. However, PMN does not explain the predilection of prostate cancer towards bone metastasis. In this review, we discuss the initiation of bone metastasis of prostate cancer from the perspective of PMN and tumor microenvironment in a step-wise manner. Furthermore, we present a new concept called pre-metastatic bone niche, featuring inherent BMDC, to interpret bone metastasis. Moreover, we illustrate the regulation of traditional Chinese medicine on PMN.

Molecular mechanisms and clinical applications of exosomes in prostate cancer

Prostate cancer (PC) is a common tumor in men, and the incidence rate is high worldwide. Exosomes are nanosized vesicles released by all types of cells into multiple biological fluid types. These vesicles contribute to intercellular communication by delivering both nucleic acids and proteins to recipient cells. In recent years, many studies have explored the mechanisms by which exosomes mediate the epithelial-mesenchymal transition, angiogenesis, tumor microenvironment establishment, and drug resistance acquisition in PC, and the mechanisms that have been identified and the molecules involved have provided new perspectives for the possible discovery of novel diagnostic markers in PC. Furthermore, the excellent biophysical properties of exosomes, such as their high stability, high biocompatibility and ability to cross biological barriers, have made exosomes promising candidates for use in novel targeted drug delivery system development. In this review, we summarize the roles of exosomes in the growth and signal transmission in PC and show the promising future of exosome contributions to PC diagnostics and treatment.

Liquid Biopsy in Pre-Metastatic Niche: From Molecular Mechanism to Clinical Application

Metastatic dissemination represents a hallmark of cancer that is responsible for the high mortality rate. Recently, emerging evidence demonstrates a time-series event—pre-metastatic niche (PMN) has a profound impact on cancer metastasis. Exosomes, cell-free DNA (cfDNA), circulating tumor cells (CTC), and tumor microenvironment components, as critical components in PMN establishment, could be monitored by liquid biopsy. Intensive studies based on the molecular profile of liquid biopsy have made it a viable alternative to tissue biopsy. Meanwhile, the complex molecular mechanism and intercellular interaction are great challenges for applying liquid biopsy in clinical practice. This article reviews the cellular and molecular components involved in the establishment of the PMN and the promotion of metastasis, as well as the mechanisms of their interactions. Better knowledge of the characteristics of the PMN may facilitate the application of liquid biopsy for clinical diagnosis, prognosis, and treatment.

Identification of ISG15 and ZFP36 as novel hypoxia- and immune-related gene signatures contributing to a new perspective for the treatment of prostate cancer by bioinformatics and experimental verification

Background

Prostatic cancer (PCa) is one of the most common malignant tumors in men worldwide. Emerging evidence indicates significance of hypoxia and immunity in PCa invasion and metastasis. This study aimed to develop a hypoxia- and immune-related gene risk signature and explore the molecular mechanisms to formulate a better prognostic tool for PCa patients.

Methods

The hypoxia and immune scores of all PCa patients in The Cancer Genome Atlas (TCGA) dataset were calculated via the maximally selected rank statistics method and the ESTIMATE algorithm. From common genes identified overlapping hypoxia- and immune-related differentially expressed genes (DE-HRGs and DE-IRGs), a hypoxia- and immune-related gene risk signature was developed utilizing univariate and multivariate Cox regression analyses, and validated in the Memorial Sloan Kettering Cancer Centre (MSKCC) database. The immune cell infiltration level of PCa samples were evaluated with ssGSEA algorithm. Differential expression of prognostic genes was evidenced by immunohistochemistry and western blot (WB) in paired PCa samples. Expression levels of these genes and their variations under regular and hypoxic conditions were examined in cell lines. The functional effects of the prognostic gene on PCa cells were examined by wound healing and transwell assays.

Results

A hypoxia- and immune-related gene risk signature constructed by ISG15 and ZFP36 displays significant predictive potency, with higher risk score representing worse survival. A nomogram based on independent prognostic factors including the risk score and Gleason score exhibited excellent clinical value in the survival prediction of PCa. Infiltration levels of eosinophils, neutrophils, Tcm, Tem, TFH, Th1 cells, and Th17 cells were significantly lower in the high-risk group. Conversely, aDC, pDC, T helper cells, and Tregs were significantly higher. Additionally, the two prognostic genes were closely correlated with the tumor-infiltrating immune cell subset in PCa progression. RT-qPCR and WB presented higher and lower expression of ISG15 and ZFP36 in PCa cells, respectively. They were correspondingly increased and decreased in PCa cells under hypoxic conditions. Wound healing and transwell assays showed that over-expression of ISG15 promoted the migration and invasion of PCa cells.

Conclusion

Our study identified a novel hypoxia- and immune-related gene signature, contributing a new perspective to the treatment of PCa

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03398-4.

Hypoxia Induced Changes of Exosome Cargo and Subsequent Biological Effects

Exosomes are small extracellular vesicles that are secreted by almost all types of cells and exist in almost all extracellular spaces. As an important mediator of intercellular communication, exosomes encapsulate the miRNA, lncRNA, cirRNA, mRNA, cytokine, enzyme, lipid, and other components from the cytoplasm into its closed single membrane structure and transfer them to recipient units in an autocrine, paracrine, or endocrine manner. Hypoxia is a state of low oxygen tension and is involved in many pathological processes. Hypoxia influences the size, quantity, and expression of exosome cargos. Exosomes derived from hypoxic tumor cells transfer genetics, proteins, and lipids to the recipient units to exert pleiotropic effects. Different donor cells produce different cargo contents, target different recipient units and lead to different biological effects. Hypoxic exosomes derived from tumor cells uptaken by normoxic tumor cells lead to promoted proliferation, migration, and invasion; uptaken by extracellular space or liver lead to promoted metastasis; uptaken by endothelial cells lead to promoted angiogenesis; uptaken by immune cells lead to promoted macrophage polarization and changed tumor immune microenvironment. In addition to various types of tumors, hypoxic exosomes also participate in the development of diseases in the cardiovascular system, neuron system, respiratory system, hematology system, endocrine system, urinary system, reproduction system, and skeletomuscular system. Understanding the special characteristics of hypoxic exosomes provide new insight into elaborating the pathogenesis of hypoxia related disease. This review summarizes hypoxia induced cargo changes and the biological effects of hypoxic exosomes in tumors and non-malignant diseases in different systems.

Tumor microenvironment mechanisms and bone metastatic disease progression of prostate cancer

During disease progression from primary towards metastatic prostate cancer (PCa), and in particular bone metastases, the tumor microenvironment (TME) evolves in parallel with the cancer clones, altering extracellular matrix composition (ECM), vasculature architecture, and recruiting specialized tumor-supporting cells that favor tumor spread and colonization at distant sites. We introduce the clinical profile of advanced metastatic PCa in terms of common genetic alterations. Findings from recently developed models of PCa metastatic spread are discussed, focusing mainly on the role of the TME (mainly matrix and fibroblast cell types), at distinct stages: premetastatic niche orchestrated by the primary tumor towards the metastatic site and bone metastasis. We report evidence of premetastatic niche formation, such as the mechanisms of distant site conditioning by extracellular vesicles, chemokines and other tumor-derived mechanisms, including altered cancer cell-ECM interactions. Furthermore, evidence supporting the similarities of stroma alterations among the primary PCa and bone metastasis, and contribution of TME to androgen deprivation therapy resistance are also discussed. We summarize the available bone metastasis transgenic mouse models of PCa from a perspective of pro-metastatic TME alterations during disease progression and give an update on the current diagnostic and therapeutic radiological strategies for bone metastasis clinical management.

Exosomal MMP-1 transfers metastasis potential in triple-negative breast cancer through PAR1-mediated EMT

PURPOSE

Triple-negative breast cancer (TNBC) is a subtype of breast cancer with high risk of distant metastasis, in which the intercellular communication between tumor cells also plays a role. Exosomes can be released by tumor cells and promote distant metastasis through intercellular communication or changes in tumor microenvironment, it is an optimized transportation facility for biologically active payloads. This was a hypothesis-generating research on role of exosomal payload in TNBC distant metastasis.

METHODS

Exosomes isolated from supernatant of MDA-MB-231 and MDA-MB-231-HM (a highly pulmonary metastatic variant of parental MDA-MB-231 cells) were characterized. MMP-1 level was detected using mass spectrometry and western blot. Transwell assay, wound healing and CCK-8 assay were employed to explore the effect of exosomal MMP-1 on the metastatic capability of TNBC cells in vitro. Human breast cancer lung metastasis model in nude mice was established to observe the effect of exosomal MMP-1 in vivo. Tissue microarray and blood samples of TNBC patients were applied to analyze the relevance between MMP-1 with metastasis.

RESULTS

MDA-MB-231-HM cells secrete exosomes enriched MMP-1, which can be taken up and enhance invasion and migration activities of TNBC cells, including MDA-MB-231, MDA-MB-468 and BT549. After ingesting exosomes enriched with MMP-1, cells secret more MMP-1, which may interact with membrane G protein receptor protease activated receptor 1 (PAR1), thereby initiating epithelial-mesenchymal transition (EMT) to enhance capability of migration and invasion. The lung colonization model shows that the expressions of MMP-1 and PAR1 in the metastases of the 231-HM-exo treated mice were both upregulated. Clinically, the enrichment of MMP-1 can be detected in exosomes extracted from serum of patients with metastasis at higher concentration than that in pre-operative patients. Moreover, in patients with multiple distant metastases, the level of MMP-1 in exosomes is also higher than that in patients with single lesion.

CONCLUSION

MMP-1 from TNBC cells of high metastasis potential can promote the distant metastasis of transform those with low metastasis potential through PAR1-mediated EMT and is likely to be a potential molecular marker.

Utilising extracellular vesicles for early cancer diagnostics: benefits, challenges and recommendations for the future

To increase cancer patient survival and wellbeing, diagnostic assays need to be able to detect cases earlier, be applied more frequently, and preferably before symptoms develop. The expansion of blood biopsy technologies such as detection of circulating tumour cells and cell-free DNA has shown clinical promise for this. Extracellular vesicles released into the blood from tumour cells may offer a snapshot of the whole of the tumour. They represent a stable and multifaceted complex of a number of different types of molecules including DNA, RNA and protein. These represent biomarker targets that can be collected and analysed from blood samples, offering great potential for early diagnosis. In this review we discuss the benefits and challenges of the use of extracellular vesicles in this context and provide recommendations on where this developing field should focus their efforts to bring future success.

Optical Imaging of Matrix Metalloproteinases Activity in Prostate Tumors in Mice

The molecular characterization of cancer could have significant clinical benefits, including early diagnosis, making treatment decisions, and monitoring therapeutic response. In this regard, noninvasive assessment of expression/activity of specific molecules in tumors could be vital in managing cancer. Optical probes have demonstrated promise in the molecular imaging of cancer. Here, we have described a method to noninvasively assess the activity of matrix metalloproteinases (MMPs) in human prostate tumors in mice. We used an activatable probe MMPSense™ 750 FAST (MMPSense750) with fluorescent properties in the near-infrared (NIR) range with peak excitation at ~749 nm and peak emission ~775 nm. These optical properties offer the advantage of a higher depth of detection. This probe has shown immense potential in imaging MMPs activity in deeper tissue with high target-specific signal and low background autofluorescence. Therefore, this probe could be valuable in assessing MMPs activity in primary tumors and metastasis.

Exosomes in the hypoxic TME: from release, uptake and biofunctions to clinical applications

Hypoxia is a remarkable trait of the tumor microenvironment (TME). When facing selective pressure, tumor cells show various adaptive characteristics, such as changes in the expression of cancer hallmarks (increased proliferation, suppressed apoptosis, immune evasion, and so on) and more frequent cell communication. Because of the adaptation of cancer cells to hypoxia, exploring the association between cell communication mediators and hypoxia has become increasingly important. Exosomes are important information carriers in cell-to-cell communication. Abundant evidence has proven that hypoxia effects in the TME are mediated by exosomes, with the occasional formation of feedback loops. In this review, we equally focus on the biogenesis and heterogeneity of cancer-derived exosomes and their functions under hypoxia and describe the known and potential mechanism ascribed to exosomes and hypoxia. Notably, we call attention to the size change of hypoxic cancer cell-derived exosomes, a characteristic long neglected, and propose some possible effects of this size change. Finally, jointly considering recent developments in the understanding of exosomes and tumors, we describe noteworthy problems in this field that urgently need to be solved for better research and clinical application.

Emerging Role of Cancer-Associated Fibroblasts-Derived Exosomes in Tumorigenesis

Cancer-associated fibroblasts (CAFs) are the most important component of the stromal cell population in the tumor microenvironment and play an irreplaceable role in oncogenesis and cancer progression. Exosomes, a class of small extracellular vesicles, can transfer biological information (e.g., proteins, nucleic acids, and metabolites as messengers) from secreting cells to target recipient cells, thereby affecting the progression of human diseases, including cancers. Recent studies revealed that CAF-derived exosomes play a crucial part in tumorigenesis, tumor cell proliferation, metastasis, drug resistance, and the immune response. Moreover, aberrant expression of CAF-derived exosomal noncoding RNAs and proteins strongly correlates with clinical pathological characterizations of cancer patients. Gaining deeper insight into the participation of CAF-derived exosomes in tumorigenesis may lead to novel diagnostic biomarkers and therapeutic targets in human cancers.

Tumor extracellular vesicles drive metastasis (it's a long way from home)

Among a plethora of functions, extracellular vesicles released by primary tumors spread in the organism and reach distant organs where they can induce the formation of a premetastatic niche. This constitutes a favorable microenvironment for circulating tumor cells which facilitates their seeding and colonization. In this review, we describe the journey of extracellular vesicles (EVs) from the primary tumor to the future metastatic organ, with a focus on the mechanisms used by EVs to target organs with a specific tropism (i.e., organotropism). We then highlight important tumor EV cargos in the context of premetastatic niche formation and summarize their known effects on extracellular matrix remodeling, angiogenesis, vessel permeabilization, resident cell activation, recruitment of foreign cells, and ultimately the formation of a pro-inflammatory and immuno-tolerant microenvironment. Finally, we discuss current experimental limitations and remaining opened questions in light of metastatic diagnosis and potential therapies targeting PMN formation.

Pre-metastatic Niche Formation in Different Organs Induced by Tumor Extracellular Vesicles

Primary tumors selectively modify the microenvironment of distant organs such as the lung, liver, brain, bone marrow, and lymph nodes to facilitate metastasis. This supportive metastatic microenvironment in distant organs was termed the pre-metastatic niche (PMN) that is characterized by increased vascular permeability, extracellular matrix remodeling, bone marrow-derived cells recruitment, angiogenesis, and immunosuppression. Extracellular vesicles (EVs) are a group of cell-derived membranous structures that carry various functional molecules. EVs play a critical role in PMN formation by delivering their cargos to recipient cells in target organs. We provide an overview of the characteristics of the PMN in different organs promoted by cancer EVs and the underlying mechanisms in this review.

Hypoxia inducible factor signaling in breast tumors controls spontaneous tumor dissemination in a site-specific manner

Hypoxia is a common feature in tumors and induces signaling that promotes tumor cell survival, invasion, and metastasis, but the impact of hypoxia inducible factor (HIF) signaling in the primary tumor on dissemination to bone in particular remains unclear. To better understand the contributions of hypoxia inducible factor 1 alpha (HIF1α), HIF2α, and general HIF pathway activation in metastasis, we employ a PyMT-driven spontaneous murine mammary carcinoma model with mammary specific deletion of Hif1α, Hif2α, or von Hippel-Lindau factor (Vhl) using the Cre-lox system. Here we show that Hif1α or Hif2α deletion in the primary tumor decreases metastatic tumor burden in the bone marrow, while Vhl deletion increases bone tumor burden, as hypothesized. Unexpectedly, Hif1α deletion increases metastatic tumor burden in the lung, while deletion of Hif2α or Vhl does not affect pulmonary metastasis. Mice with Hif1α deleted tumors also exhibit reduced bone volume as measured by micro computed tomography, suggesting that disruption of the osteogenic niche may be involved in the preference for lung dissemination observed in this group. Thus, we reveal that HIF signaling in breast tumors controls tumor dissemination in a site-specific manner.

Angiogenesis and Anti-Angiogenic Treatment in Prostate Cancer: Mechanisms of Action and Molecular Targets

Prostate cancer (PC) is the most common cancer in men and the second leading cause of cancer-related death worldwide. Many therapeutic advances over the last two decades have led to an improvement in the survival of patients with metastatic PC, yet the majority of these patients still succumb to their disease. Antiagiogenic therapies have shown substantial benefits for many types of cancer but only a marginal benefit for PC. Ongoing clinical trials investigate antiangiogenic monotherapies or combination therapies. Despite the important role of angiogenesis in PC, clinical trials in refractory castration-resistant PC (CRPC) have demonstrated increased toxicity with no clinical benefit. A better understanding of the mechanism of angiogenesis may help to understand the failure of trials, possibly leading to the development of new targeted anti-angiogenic therapies in PC. These could include the identification of specific subsets of patients who might benefit from these therapeutic strategies. This paper provides a comprehensive review of the pathways involved in the angiogenesis, the chemotherapeutic agents with antiangiogenic activity, the available studies on anti-angiogenic agents and the potential mechanisms of resistance.

LOXL2-enriched small extracellular vesicles mediate hypoxia-induced premetastatic niche and indicates poor outcome of head and neck cancer

Small extracellular vesicles (sEVs) operate as a signaling platform due to their ability to carry functional molecular cargos. However, the role of sEVs in hypoxic tumor microenvironment-mediated premetastatic niche formation remains poorly understood. Methods: Protein expression profile of sEVs derived from normoxic and hypoxic head and neck squamous cell carcinoma (HNSCC) cells were determined by Isobaric Tagging Technology for Relative Quantitation. In vitro invasion assay and in vivo colonization were performed to evaluate the role of sEV-delivering proteins. Results: We identified lysyl oxidase like 2 (LOXL2) which had the highest fold increase in hypoxic sEVs compared with normoxic sEVs. Hypoxic cell-derived sEVs delivered high amounts of LOXL2 to non-hypoxic HNSCC cells to elicit epithelial-to-mesenchymal transition (EMT) and induce the invasion of the recipient cancer cells. Moreover, LOXL2-enriched sEVs were incorporated by distant fibroblasts and activate FAK/Src signaling in recipient fibroblasts. Increased production of fibronectin mediated by FAK/Src signaling recruited myeloid-derived suppressor cells to form a premetastatic niche. Serum sEV LOXL2 can reflect a hypoxic and aggressive tumor type and can serve as an alternative to tissue LOXL2 as an independent prognostic factor of overall survival for patients with HNSCC. Conclusion: sEVs derived from the hypoxic tumor microenvironment of HNSCC can drive local invasion of non-hypoxic HNSCC cells and stimulate premetastatic niche formation by delivering LOXL2 to non-hypoxic HNSCC cells and fibroblasts to induce EMT and fibronectin production, respectively.

Role of Exosomes in Prostate Cancer Metastasis

Prostate cancer remains a life-threatening disease among men worldwide. The majority of PCa-related mortality results from metastatic disease that is characterized by metastasis of prostate tumor cells to various distant organs, such as lung, liver, and bone. Bone metastasis is most common in prostate cancer with osteoblastic and osteolytic lesions. The precise mechanisms underlying PCa metastasis are still being delineated. Intercellular communication is a key feature underlying prostate cancer progression and metastasis. There exists local signaling between prostate cancer cells and cells within the primary tumor microenvironment (TME), in addition to long range signaling wherein tumor cells communicate with sites of future metastases to promote the formation of pre-metastatic niches (PMN) to augment the growth of disseminated tumor cells upon metastasis. Over the last decade, exosomes/ extracellular vesicles have been demonstrated to be involved in such signaling. Exosomes are nanosized extracellular vesicles (EVs), between 30 and 150 nm in thickness, that originate and are released from cells after multivesicular bodies (MVB) fuse with the plasma membrane. These vesicles consist of lipid bilayer membrane enclosing a cargo of biomolecules, including proteins, lipids, RNA, and DNA. Exosomes mediate intercellular communication by transferring their cargo to recipient cells to modulate target cellular functions. In this review, we discuss the contribution of exosomes/extracellular vesicles in prostate cancer progression, in pre-metastatic niche establishment, and in organ-specific metastases. In addition, we briefly discuss the clinical significance of exosomes as biomarkers and therapeutic agents.