Revisiting the advances and challenges in the clinical applications of extracellular vesicles in cancer.

Extracellular vesicles (EVs) have been the subject of an exponentially growing number of studies covering their biogenesis mechanisms, isolation and analysis techniques, physiological and pathological roles, and clinical applications, such as biomarker and therapeutic uses. Nevertheless, the heterogeneity of EVs both challenges our understanding of them and presents new opportunities for their potential application. Recently, the EV field experienced a wide range of advances. However, the challenges also remain huge. This review focuses on the recent progress and difficulties encountered in the practical use of EVs in clinical settings. In addition, we also explored the concept of EV heterogeneity to acquire a more thorough understanding of EVs and their involvement in cancer, specifically focusing on the fundamental nature of EVs.

Glutamine addiction in tumor cell: oncogene regulation and clinical treatment.

After undergoing metabolic reprogramming, tumor cells consume additional glutamine to produce amino acids, nucleotides, fatty acids, and other substances to facilitate their unlimited proliferation. As such, the metabolism of glutamine is intricately linked to the survival and progression of cancer cells. Consequently, targeting the glutamine metabolism presents a promising strategy to inhibit growth of tumor cell and cancer development. This review describes glutamine uptake, metabolism, and transport in tumor cells and its pivotal role in biosynthesis of amino acids, fatty acids, nucleotides, and more. Furthermore, we have also summarized the impact of oncogenes like C-MYC, KRAS, HIF, and p53 on the regulation of glutamine metabolism and the mechanisms through which glutamine triggers mTORC1 activation. In addition, role of different anti-cancer agents in targeting glutamine metabolism has been described and their prospective applications are assessed.

Extracellular vesicle-cell adhesion molecules in tumours: biofunctions and clinical applications.

Cell adhesion molecule (CAM) is an umbrella term for several families of molecules, including the cadherin family, integrin family, selectin family, immunoglobulin superfamily, and some currently unclassified adhesion molecules. Extracellular vesicles (EVs) are important information mediators in cell-to-cell communication. Recent evidence has confirmed that CAMs transported by EVs interact with recipient cells to influence EV distribution in vivo and regulate multiple cellular processes. This review focuses on the loading of CAMs onto EVs, the roles of CAMs in regulating EV distribution, and the known and possible mechanisms of these actions. Moreover, herein, we summarize the impacts of CAMs transported by EVs to the tumour microenvironment (TME) on the malignant behaviour of tumour cells (proliferation, metastasis, immune escape, and so on). In addition, from the standpoint of clinical applications, the significance and challenges of using of EV-CAMs in the diagnosis and therapy of tumours are discussed. Finally, considering recent advances in the understanding of EV-CAMs, we outline significant challenges in this field that require urgent attention to advance research and promote the clinical applications of EV-CAMs. Video Abstract.

mRNA vaccine in cancer therapy: Current advance and future outlook.

Messenger ribonucleic acid (mRNA) vaccines are a relatively new class of vaccines that have shown great promise in the immunotherapy of a wide variety of infectious diseases and cancer. In the past 2 years, SARS-CoV-2 mRNA vaccines have contributed tremendously against SARS-CoV2, which has prompted the arrival of the mRNA vaccine research boom, especially in the research of cancer vaccines. Compared with conventional cancer vaccines, mRNA vaccines have significant advantages, including efficient production of protective immune responses, relatively low side effects and lower cost of acquisition. In this review, we elaborated on the development of cancer vaccines and mRNA cancer vaccines, as well as the potential biological mechanisms of mRNA cancer vaccines and the latest progress in various tumour treatments, and discussed the challenges and future directions for the field.

Crosstalk between autophagy and CSCs: molecular mechanisms and translational implications.

Cancer stem cells(CSCs) play a key role in regulating tumorigenesis, progression, as well as recurrence, and possess typical metabolic characteristics. Autophagy is a catabolic process that can aid cells to survive under stressful conditions such as nutrient deficiency and hypoxia. Although the role of autophagy in cancer cells has been extensively studied, CSCs possess unique stemness, and their potential relationship with autophagy has not been fully analyzed. This study summarizes the possible role of autophagy in the renewal, proliferation, differentiation, survival, metastasis, invasion, and treatment resistance of CSCs. It has been found that autophagy can contribute to the maintenance of CSC stemness, facilitate the tumor cells adapt to changes in the microenvironment, and promote tumor survival, whereas in some other cases autophagy acts as an important process involved in the deprivation of CSC stemness thus leading to tumor death. Mitophagy, which has emerged as another popular research area in recent years, has a great scope when explored together with stem cells. In this study, we have aimed to elaborate on the mechanism of action of autophagy in regulating the functions of CSCs to provide deeper insights for future cancer treatment.

Targeting tumor-associated macrophages in hepatocellular carcinoma: biology, strategy, and immunotherapy.

Hepatocellular carcinoma (HCC), one of the most malignant tumors, is characterized by its stubborn immunosuppressive microenvironment. As one of the main members of the tumor microenvironment (TME) of HCC, tumor-associated macrophages (TAMs) play a critical role in its occurrence and development, including stimulating angiogenesis, enhancing immunosuppression, and promoting the drug resistance and cancer metastasis. This review describes the origin as well as phenotypic heterogeneity of TAMs and their potential effects on the occurrence and development of HCC and also discusses about various adjuvant therapy based strategies that can be used for targeting TAMs. In addition, we have highlighted different treatment modalities for TAMs based on immunotherapy, including small molecular inhibitors, immune checkpoint inhibitors, antibodies, tumor vaccines, adoptive cellular immunotherapy, and nanocarriers for drug delivery, to explore novel combination therapies and provide feasible therapeutic options for clinically improving the prognosis and quality of life of HCC patients.

Retraction Notice to: YAP1 Inhibition in HUVECs Is Associated with Released Exosomes and Increased Hepatocarcinoma Invasion and Metastasis.

[This retracts the article DOI: 10.1016/j.omtn.2020.05.021.].

METTL3 promotes m6A hypermethylation of RBM14 via YTHDF1 leading to the progression of hepatocellular carcinoma.

Liver is a well-known immunological organ with unique microenvironment. In normal conditions, the rich immune-infiltrating cells cooperate with non-parenchymal cells, such as Kupffer cells (KCs). The presence of liver immunosuppressive microenvironment underlines the importance to dissect this interaction to understand how this cross-talk promotes tumor growth in hepatocellular carcinoma (HCC). Therefore, the aim of the study here was to probe the role of methyltransferase-like 3 (METTL3) in the HCC progression and its effect on the polarization of KCs. KCs showed M2 polarization, and METTL3 was overexpressed in our collected HCC tissues relative to adjacent tissues. METTL3 depletion inhibited the M2 polarization of KCs, thereby reverting the malignant phenotype of HCC cells in vitro and growth and metastasis in vivo. Mechanistically, YTH domain-containing family protein 1 (YTHDF1) bound to RNA-binding protein 14 (RBM14), whereas METTL3 knockdown in KCs cells suppressed RBM14 expression by decreasing N-methyladenosine (m6A) methylation. Overexpression of RBM14 mitigated the anti-tumor effects of sh-METTL3 in vitro and in vivo. It is suggested that the mechanism of sh-METTL3 suppressing the polarization of KCs and the progression of HCC is to regulate the RBM14 expression via YTHDF1-dependent m6A modification.

Histone deacetylase 2 regulates STAT1-dependent upregulation of atypical chemokine receptor 3 to induce M2 macrophage migration and immune escape in hepatocellular carcinoma.

Atypical chemokine receptor 3 (ACKR3) has been linked to the tumor microenvironment. This work investigates the effects of ACKR3 and its regulatory molecules on the chemotactic migration of tumor-associated macrophages (TAMs) in hepatocellular carcinoma (HCC). RT-qPCR and western blot assays identified elevated ACKR3 and HDAC2 levels in HCC tissues and cells. Knockdown or overexpression of ACKR3 was induced in HCC cells through vectors of lentivirus plasmids, and then the conditioned medium of the HCC cells was collected to stimulate TAMs. The stimulated TAMs were co-cultured with CD3+ T cells. ACKR3 knockdown in HCC cells inhibited migration of TAMs and promoted M1 polarization, which restored the activity of T cells. Histone deacetylase 2 (HDAC2) recruited signal transducer and activator of transcription 1 (STAT1) to the ACKR3 promoter to activate ACKR3 transcription. HDAC2 silencing suppressed nuclear translocation of STAT1 and decreased ACKR3 expression. HDAC2 knockdown in HCC cells similarly suppressed TAM migration, promoted M1 polarization, and restored T cell function, but these changes were inversed by ACKR3 upregulation. HDAC2 or ACKR3 silencing weakened tumor growth and immune escape in mice. In conclusion, this study demonstrates that HDAC2 upregulates ACKR3 via STAT1 to induce migration of M2 macrophages and immune escape in HCC.

Tumor-derived exosomes in the cancer immune microenvironment and cancer immunotherapy.

Tumor-derived exosomes (TDEs) are key immune regulators in the tumor microenvironment. They have been shown to reshape the immune microenvironment and prevent antitumor immune responses via their immunosuppressive cargo, thereby determining responsiveness to cancer therapy. By delivering suppressive cargo to the immune cells, TDEs directly or indirectly influence the functions and antitumor activities of immune cells. TDE-based therapy is emerging as a cutting-edge and promising strategy for inhibiting tumor progression or enhancing antitumor immunity. Therefore, in this study, we reviewed the mechanism by which TDEs regulate immune cells and their applications in immunotherapy.

Mesenchymal/stromal stem cells: necessary factors in tumour progression.

Mesenchymal/stromal stem cells (MSCs) are a crucial component of the tumour microenvironment (TME). They can be recruited from normal tissues into the TME and educated by tumour cells to transform into tumour-associated MSCs, which are oncogenic cells that promote tumour development and progression by impacting or transforming into various kinds of cells, such as immune cells and endothelial cells. Targeting MSCs in the TME is a novel strategy to prevent malignant processes. Exosomes, as communicators, carry various RNAs and proteins and thus link MSCs and the TME, which provides options for improving outcomes and developing targeted treatment.

ALDH2 Hampers Immune Escape in Liver Hepatocellular Carcinoma through ROS/Nrf2-mediated Autophagy.

Aldehyde dehydrogenase 2 (ALDH2) has been implicated in the progression of liver hepatocellular carcinoma (LIHC). The most important feature of LIHC is the immune escape process. This study sets to study the role of ALDH2 in regulating immune escape in LIHC. Bioinformatics analysis was applied to examine the expression of ALDH2 in LIHC and its impact on patients' survival. The effect of ALDH2 expression on malignant phenotype of LIHC cells was assessed by gain-of-function assays. RT-qPCR and Western blot were conducted to examine the expression of related factors, thus investigating the downstream mechanisms of ALDH2. ELISA assay was carried out to measure the level of oxidative stress in cells, and crystal violet staining was conducted to observe the killing effect of T cells on tumor cells. Finally, xenograft assay was carried out to verify the role of ALDH2 in vivo.ALDH2 was poorly expressed in LIHC, which predicted dismal prognoses for patients. ALDH2 inhibited the malignant aggressiveness of LIHC cells. ALDH2 blocked the activation of Nrf2 by suppressing reactive oxygen species (ROS) in LIHC, and Nrf2 significantly reversed the tumor-suppressing properties of ALDH2. Nrf2 hindered autophagy and led to immune escape of LIHC cells. Moreover, ALDH2 considerably suppressed the growth of xenografts, increased autophagy and promoted the accumulation of T cells in tumors. In contrast, Nrf2 drastically reversed the repressive effect of ALDH2 on tumor growth.ALDH2 impaired the ROS/Nrf2 axis to promote autophagy, thereby repressing immune escape in LIHC.

Targeting tumor innervation: premises, promises, and challenges.

A high intratumoral nerve density is correlated with poor survival, high metastasis, and high recurrence across multiple solid tumor types. Recent research has revealed that cancer cells release diverse neurotrophic factors and exosomes to promote tumor innervation, in addition, infiltrating nerves can also mediate multiple tumor biological processes via exosomes and neurotransmitters. In this review, through seminal studies establishing tumor innervation, we discuss the communication between peripheral nerves and tumor cells in the tumor microenvironment (TME), and revealed the nerve-tumor regulation mechanisms on oncogenic process, angiogenesis, lymphangiogenesis, and immunity. Finally, we discussed the promising directions of 'old drugs newly used' to target TME communication and clarified a new line to prevent tumor malignant capacity.

The regulation, function, and role of lipophagy, a form of selective autophagy, in metabolic disorders.

Autophagy is a conserved method of quality control in which cytoplasmic contents are degraded via lysosomes. Lipophagy, a form of selective autophagy and a novel type of lipid metabolism, has recently received much attention. Lipophagy is defined as the autophagic degradation of intracellular lipid droplets (LDs). Although much remains unknown, lipophagy appears to play a significant role in many organisms, cell types, metabolic states, and diseases. It participates in the regulation of intracellular lipid storage, intracellular free lipid levels (e.g., fatty acids), and energy balance. However, it remains unclear how intracellular lipids regulate autophagy. Impaired lipophagy can cause cells to become sensitive to death stimuli and may be responsible for the onset of a variety of diseases, including nonalcoholic fatty liver disease and metabolic syndrome. Like autophagy, the role of lipophagy in cancer is poorly understood, although analysis of specific autophagy receptors has helped to expand the diversity of chemotherapeutic targets. These studies have stimulated increasing interest in the role of lipophagy in the pathogenesis and treatment of cancer and other human diseases.

Extracellular vesicle PD-L1 in reshaping tumor immune microenvironment: biological function and potential therapy strategies.

Programmed cell death 1 ligand 1 (PD-L1) is the ligand for programmed death protein-1 (PD-1), is associated with immunosuppression. Signaling via PD-1/PD-L1 will transmits negative regulatory signals to T cells, inducing T-cell inhibition, reducing CD8+ T-cell proliferation, or promoting T-cell apoptosis, which effectively reduces the immune response and leads to large-scale tumor growth. Accordingly, many antibody preparations targeting PD-1 or PD-L1 have been designed to block the binding of these two proteins and restore T-cell proliferation and cytotoxicity of T cells. However, these drugs are ineffective in clinical practice. Recently, numerous of studies have shown that, in addition to the surface of tumor cells, PD-L1 is also found on the surface of extracellular vesicles secreted by these cells. Extracellular vesicle PD-L1 can also interact with PD-1 on the surface of T cells, leading to immunosuppression, and has been proposed as a potential mechanism underlying PD-1/PD-L1-targeted drug resistance. Therefore, it is important to explore the production, regulation and tumor immunosuppression of PD-L1 on the surface of tumor cells and extracellular vesicles, as well as the potential clinical application of extracellular vesicle PD-L1 as tumor biomarkers and therapeutic targets. Video Abstract.

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.

CISD2 Promotes Resistance to Sorafenib-Induced Ferroptosis by Regulating Autophagy in Hepatocellular Carcinoma.

PURPOSE: Sorafenib is a multi-kinase inhibitor that is used as a standard treatment for advanced hepatocellular carcinoma (HCC). However, the mechanism of sorafenib resistance in HCC is still unclear. It has been shown that CISD2 expression is related to the progression and poor prognosis of HCC. Here, we show a new role for CISD2 in sorafenib resistance in HCC. METHODS: Bioinformatic analysis was used to detect the expression of negative regulatory genes of ferroptosis in sorafenib-resistant samples. The concentration gradient method was used to establish sorafenib-resistant HCC cells. Western blot was used to detect the protein expression of CISD2, LC3, ERK, PI3K, AKT, mTOR, and Beclin1 in HCC samples. Quantitative real-time PCR (qPCR) was used to detect gene expression. CISD2 shRNA and Beclin1 shRNA were transfected to knock down the expression of the corresponding genes. Cell viability was detected by a CCK-8 assay. ROS were detected by DCFH-DA staining, and MDA and GSH were detected with a Lipid Peroxidation MDA Assay Kit and Micro Reduced Glutathione (GSH) Assay Kit, respectively. Flow cytometry was used to detect apoptosis and the levels of ROS and iron ions. RESULTS: CISD2 was highly expressed in HCC cells compared with normal cells and was associated with poor prognosis in patients. Knockdown of CISD2 promoted a decrease in the viability of drug-resistant HCC cells. CISD2 knockdown promoted sorafenib-induced ferroptosis in resistant HCC cells. The levels of ROS, MDA, and iron ions increased, but the change in GSH was not obvious. Knockdown of CISD2 promoted uncontrolled autophagy in resistant HCC cells. Inhibition of autophagy attenuated CISD2 knockdown-induced ferroptosis. The autophagy promoted by CISD2 knockdown was related to Beclin1. When CISD2 and Beclin1 were inhibited, the effect on ferroptosis was correspondingly weakened. CONCLUSION: Inhibition of CISD2 promoted sorafenib-induced ferroptosis in resistant cells, and this process promoted excessive iron ion accumulation through autophagy, leading to ferroptosis. The combination of CISD2 inhibition and sorafenib treatment is an effective therapeutic strategy for resistant HCC.

Rab GTPases: Central Coordinators of Membrane Trafficking in Cancer.

Tumor progression involves invasion, migration, metabolism, autophagy, exosome secretion, and drug resistance. Cargos transported by membrane vesicle trafficking underlie all of these processes. Rab GTPases, which, through coordinated and dynamic intracellular membrane trafficking alongside cytoskeletal pathways, determine the maintenance of homeostasis and a series of cellular functions. The mechanism of vesicle movement regulated by Rab GTPases plays essential roles in cancers. Therefore, targeting Rab GTPases to adjust membrane trafficking has the potential to become a novel way to adjust cancer treatment. In this review, we describe the characteristics of Rab GTPases; in particular, we discuss the role of their activation in the regulation of membrane transport and provide examples of Rab GTPases regulating membrane transport in tumor progression. Finally, we discuss the clinical implications and the potential as a cancer therapeutic target of Rab GTPases.

LINC00511 drives invasive behavior in hepatocellular carcinoma by regulating exosome secretion and invadopodia formation.

BACKGROUND: Tumor cells are known to release large numbers of exosomes containing active substances that participate in cancer progression. Abnormally expressed long noncoding RNAs (lncRNAs) have been confirmed to regulate multiple processes associated with tumor progression. However, the mechanism by which lncRNAs affect exosome secretion remains unclear. METHODS: The underlying mechanisms of long noncoding RNA LINC00511 (LINC00511) regulation of multivesicular body (MVB) trafficking, exosome secretion, invadopodia formation, and tumor invasion were determined through gene set enrichment analysis (GSEA), immunoblotting, nanoparticle tracking analysis, confocal colocalization analysis, electron microscopy, and invasion experiments. RESULTS: We revealed that the tumorigenesis process is associated with a significant increase in vesicle secretion in hepatocellular carcinoma (HCC). Additionally, LINC00511 was significantly more highly expressed in HCC tissues and is related to vesicle trafficking and MVB distribution. We also found that in addition to the formation of invadopodia in HCC progression, abnormal LINC00511 induces invadopodia formation in HCC cells by regulating the colocalization of vesicle associated membrane protein 7 (VAMP7) and synaptosome associated protein 23 (SNAP23) to induce the invadopodia formation, which are key secretion sites for MVBs and control exosome secretion. Finally, we revealed that LINC0051-induced invadopodia and exosome secretion were involved in tumor progression. CONCLUSIONS: Our experiments revealed novel findings on the relationship between LINC00511 dysregulation in HCC and invadopodia production and exosome secretion. This is a novel mechanism by which LINC00511 regulates invadopodia biogenesis and exosome secretion to further promote cancer progression.

IKKß activation promotes amphisome formation and extracellular vesicle secretion in tumor cells.

Intracellular organelle cross-talk is a new and important research area. Under stress conditions, the coordinated action of the autophagy and endosomal systems in tumor cells is essential for maintaining cellular homeostasis and survival. The activation of the IκB kinase (IKK) complex is also involved in the regulation of stress and homeostasis in tumor cells. Here, we try to explore the effects of constitutively active IKKß subunits (CA-IKKß) on autophagy and endosomal system interactions. We confirm that CA-IKKß induces accumulation of autophagosomes and their fusion with MVBs to form amphisomes in cancer cells, and also drives the release of EVs containing autophagy components through an amphisome-dependent mechanism. We further demonstrate that CA-IKKß inhibits the expression of RAB7, thereby weakening the lysosomal-dependent degradation pathway. CA-IKKß also induces phosphorylation of SNAP23 at Ser95 instead of Ser110, which further promotes amphisome-plasma membrane fusion and sEV secretion. These results indicate that CA-IKKß drives the formation and transport of amphisomes, thereby regulating tumor cell homeostasis, which may illuminate a special survival mechanism in tumor cells under stress.