Extracellular vesicles (EVs) are cell-derived membrane-surrounded vesicles carrying various types of molecules. These EV cargoes are often used as pathophysiological biomarkers and delivered to recipient cells whose fates are often altered in local and distant tissues. Classical EVs are exosomes, microvesicles, and apoptotic bodies, while recent studies discovered autophagic EVs, stressed EVs, and matrix vesicles. Here, we classify classical and new EVs and non-EV nanoparticles. We also review EVs-mediated intercellular communication between cancer cells and various types of tumor-associated cells, such as cancer-associated fibroblasts, adipocytes, blood vessels, lymphatic vessels, and immune cells. Of note, cancer EVs play crucial roles in immunosuppression, immune evasion, and immunotherapy resistance. Thus, cancer EVs change hot tumors into cold ones. Moreover, cancer EVs affect nonimmune cells to promote cellular transformation, including epithelial-to-mesenchymal transition (EMT), chemoresistance, tumor matrix production, destruction of biological barriers, angiogenesis, lymphangiogenesis, and metastatic niche formation.

Extracellular heat shock proteins (ex-HSPs) have been found in exosomes, oncosomes, membrane surfaces, as well as free HSP in cancer and various pathological conditions, also known as alarmins. Such ex-HSPs include HSP90 (α, β, Gp96, Trap1), HSP70, and large and small HSPs. Production of HSPs is coordinately induced by heat shock factor 1 (HSF1) and hypoxia-inducible factor 1 (HIF-1), while matrix metalloproteinase 3 (MMP-3) and heterochromatin protein 1 are novel inducers of HSPs. Oncosomes released by tumor cells are a major aspect of the resistance-associated secretory phenotype (RASP) by which immune evasion can be established. The concepts of RASP are: (i) releases of ex-HSP and HSP-rich oncosomes are essential in RASP, by which molecular co-transfer of HSPs with oncogenic factors to recipient cells can promote cancer progression and resistance against stresses such as hypoxia, radiation, drugs, and immune systems; (ii) RASP of tumor cells can eject anticancer drugs, targeted therapeutics, and immune checkpoint inhibitors with oncosomes; (iii) cytotoxic lipids can be also released from tumor cells as RASP. ex-HSP and membrane-surface HSP (mHSP) play immunostimulatory roles recognized by CD91+ scavenger receptor expressed by endothelial cells-1 (SREC-1)+ Toll-like receptors (TLRs)+ antigen-presenting cells, leading to antigen cross-presentation and T cell cross-priming, as well as by CD94+ natural killer cells, leading to tumor cytolysis. On the other hand, ex-HSP/CD91 signaling in cancer cells promotes cancer progression. HSPs in body fluids are potential biomarkers detectable by liquid biopsies in cancers and tissue-damaged diseases. HSP-based vaccines, inhibitors, and RNAi therapeutics are also reviewed.

The tumor organoid (tumoroid) model in three-dimensional (3D) culture systems has been developed to reflect more closely the in vivo tumors than 2D-cultured tumor cells. Notably, extracellular vesicles (EVs) are efficiently collectible from the culture supernatant of gel-free tumoroids. Matrix metalloproteinase (MMP) 3 is a multi-functional factor playing crucial roles in tumor progression. However, roles of MMP3 within tumor growth and EVs have not unveiled. Here, we investigated the protumorigenic roles of MMP3 on integrities of tumoroids and EVs. We generated MMP3-knockout (KO) cells using the CRISPR/Cas9 system from rapidly metastatic LuM1 tumor cells. Moreover, we established fluorescent cell lines with palmitoylation signal-fused fluorescent proteins (tdTomato and enhanced GFP). Then we confirmed the exchange of EVs between cellular populations and tumoroids. LuM1-tumoroids released large EVs (200–1000 nm) and small EVs (50–200 nm) while the knockout of MMP3 resulted in the additional release of broken EVs from tumoroids. The loss of MMP3 led to a significant reduction in tumoroid size and the development of the necrotic area within tumoroids. MMP3 and CD9 (a category-1 EV marker tetraspanin protein) were significantly down-regulated in MMP3-KO cells and their EV fraction. Moreover, CD63, another member of the tetraspanin family, was significantly reduced only in the EVs fractions of the MMP3-KO cells compared to their counterpart. These weakened phenotypes of MMP3-KO were markedly rescued by the addition of MMP3-rich EVs or conditioned medium (CM) collected from LuM1-tumoroids, which caused a dramatic rise in the expression of MMP3, CD9, and Ki-67 (a marker of proliferating cells) in the MMP3-null/CD9-low tumoroids. Notably, MMP3 enriched in tumoroids-derived EVs and CM deeply penetrated recipient MMP3-KO tumoroids, resulting in a remarkable enlargement of solid tumoroids, while MMP3-null EVs did not. These data demonstrate that EVs can mediate molecular transfer of MMP3, resulting in increasing the proliferation and tumorigenesis, indicating crucial roles of MMP3 in tumor progression.

Matrix metalloproteinase 3 (MMP3) plays multiple roles in extracellular proteolysis as well as intracellular transcription, prompting a new definition of moonlighting metalloproteinase (MMP), according to a definition of protein moonlighting (or gene sharing), a phenomenon by which a protein can perform more than one function. Indeed, connective tissue growth factor (CTGF, aka cellular communication network factor 2 (CCN2)) is transcriptionally induced as well as cleaved by MMP3. Moreover, several members of the MMP family have been found within tumor-derived extracellular vesicles (EVs). We here investigated the roles of MMP3-rich EVs in tumor progression, molecular transmission, and gene regulation. EVs derived from a rapidly metastatic cancer cell line (LuM1) were enriched in MMP3 and a C-terminal half fragment of CCN2/CTGF. MMP3-rich, LuM1-derived EVs were disseminated to multiple organs through body fluid and were pro-tumorigenic in an allograft mouse model, which prompted us to define LuM1-EVs as oncosomes in the present study. Oncosome-derived MMP3 was transferred into recipient cell nuclei and thereby trans-activated the CCN2/CTGF promoter, and induced CCN2/CTGF production in vitro. TRENDIC and other cis-elements in the CCN2/CTGF promoter were essential for the oncosomal responsivity. The CRISPR/Cas9-mediated knockout of MMP3 showed significant anti-tumor effects such as the inhibition of migration and invasion of tumor cells, and a reduction in CCN2/CTGF promoter activity and fragmentations in vitro. A high expression level of MMP3 or CCN2/CTGF mRNA was prognostic and unfavorable in particular types of cancers including head and neck, lung, pancreatic, cervical, stomach, and urothelial cancers. These data newly demonstrate that oncogenic EVs-derived MMP is a transmissive trans-activator for the cellular communication network gene and promotes tumorigenesis at distant sites.

Tumor growth, progression, and therapy resistance are crucial factors in the prognosis of cancer. The properties of three-dimensional (3D) tumor-like organoids (tumoroids) more closely resemble in vivo tumors compared to two-dimensionally cultured cells and are therefore effectively used for assays and drug screening. We here established a repurposed drug for novel anticancer research and therapeutics using a 3D tumoroid-based screening system. We screened six pharmacologically active compounds by using an original tumoroid-based multiplex phenotypic screening system with a matrix metalloproteinase 9 (MMP9) promoter-driven fluorescence reporter for the evaluation of both tumoroid formation and progression. The antiparkinson drug benztropine was the most effective compound uncovered by the screen. Benztropine significantly inhibited in vitro tumoroid formation, cancer cell survival, and MMP9 promoter activity. Benztropine also reduced the activity of oncogenic signaling transducers and trans-activators for MMP9, including STAT3, NF-κB, and β-catenin, and the properties of cancer stem cells/cancer-initiating cells. Benztropine and GBR-12935 directly targeted the dopamine transporter DAT/SLC6A3, whose genetic alterations such as amplification were correlated with poor prognosis for cancer patients. Benztropine also inhibited the tumor growth, circulating tumor cell (CTC) number, and rate of metastasis in a tumor allograft model in mice. In conclusion, we propose the repurposing of benztropine for anticancer research and therapeutics that can suppress tumor progression, CTC, and metastasis of aggressive cancers by reducing key pro-tumorigenic factors.

Extracellular vesicles (EVs), such as exosomes or oncosomes, often carry oncogenic molecules derived from tumor cells. In addition, accumulating evidence indicates that tumor cells can eject anti-cancer drugs such as chemotherapeutics and targeted drugs within EVs, a novel mechanism of drug resistance. The EV-releasing drug resistance phenotype is often coupled with cellular dedifferentiation and transformation in cells undergoing epithelial-mesenchymal transition (EMT), and the adoption of a cancer stem cell phenotype. The release of EVs is also involved in immunosuppression. Herein, we address different aspects by which EVs modulate the tumor microenvironment to become resistant to anticancer and antibody-based drugs, as well as the concept of the resistance-associated secretory phenotype (RASP).