RAB27A promotes melanoma cell invasion and metastasis via regulation of pro-invasive exosomes

Effects of a Global Rab27a Null Mutation on Murine PVAT and Cardiovascular Function

BACKGROUND

RAB27A is a member of the RAS oncogene superfamily of GTPases and regulates cell secretory function. It, is expressed within blood vessels and perivascular adipose tissue. We hypothesized that loss of RAB27A would alter cardiovascular function.

METHODS

Body weight of Rab27aash mice was measured from 2 to 18 months of age, along with glucose resorption at 6 and 12 months of age and glucose sensitivity at 18 months of age. Body weight and cellular and molecular features of perivascular adipose tissue and aortic tissue were examined in a novel C57BL/6J Rab27a null strain. Analyses included morphometric quantification and proteomic analyses. Wire myography measured vasoreactivity, and echocardiography measured cardiac function. Comparisons across ages and genotypes were evaluated via 2-way ANOVA with multiple comparison testing. Significance for myography was determined via 4-parameter nonlinear regression testing.

RESULTS

Genome-wide association data linked rare human RAB27A variants with body mass index and glucose handling. Changes in glucose tolerance were observed in Rab27aash male mice at 18 months of age. In WT (wild-type) and Rab27a null male mice, body weight, adipocyte lipid area, and aortic area increased with age. In female mice, only body weight increased with age, independent of RAB27A presence. Protein signatures from male Rab27a null mice suggested greater associations with cardiovascular and metabolic phenotypes compared with female tissues. Wire myography results showed Rab27a null males exhibited increased vasoconstriction and reduced vasodilation at 8 weeks of age. Rab27a null females exhibited increased vasoconstriction and vasodilation at 20 weeks of age. Consistent with these vascular changes, male Rab27a null mice experienced age-related cardiomyopathy, with severe differences observed by 21 weeks of age.

CONCLUSIONS

Global RAB27A loss impacted perivascular adipose tissue and thoracic aorta proteomic signatures, altered vasocontractile responses, and decreased left ventricular ejection fraction in mice.

miRNA profiling of B16F10 melanoma cell exosomes reveals melanin synthesis-related genes

This study investigates the communication between skin cells, specifically melanocytes, keratinocytes, and fibroblasts, which is crucial for the process of melanin production known as melanogenesis. We aimed to understand the role of melanocyte exosomes in regulating melanogenesis and to uncover the microRNAs influencing this process. We isolated exosomes and characterized them using advanced microscopy and protein analysis to achieve this. We conducted experiments on melanoma cells to study melanin production regulation and examined how exosomes influenced gene expression related to melanogenesis. The results revealed that melanocyte exosomes increased certain types of tyrosinases, thereby enhancing melanin production. Furthermore, we acquired the miRNA profile of exosomes and hypothesized that specific siRNAs, such as miR-21a-5p, could potentially facilitate melanin synthesis. Our findings shed light on the importance of exosomes in skin health and provide valuable insights into intercellular communication mechanisms. Understanding these processes can pave the way for innovative therapies to treat melanin-related disorders and maintain healthy skin.

Tyrosinase regulates the motility of human melanoma cell line A375 through its hydroxylase enzymatic activity

Melanoma, originating from melanocytes, is a highly aggressive tumor. Tyrosinase is involved in melanin production in melanocytes, and its overexpression is noted in malignant melanomas. However, the role of tyrosinase in melanomas remains unclear. Therefore, this study aimed to evaluate the potential functions of tyrosinase in the human melanoma cell line A375. The expression level of tyrosinase in A375 cells was undetectable. However, markedly increased expression level was observed in the mouse melanoma cell line B16F10 and the human melanoma cell line WM266-4. Subsequently, we investigated the effect of ectopic tyrosinase expression on A375 cell motility using wound-healing assay. The overexpression of tyrosinase resulted in enhanced cell migration in both stable and transient tyrosinase expression cells. The levels of filamentous actin were decreased in tyrosinase-expressing A375 cells, suggesting that tyrosinase regulates cell motility by modulating actin polymerization. Histidine residues in tyrosinase are important for its enzymatic activity for synthesizing melanin. Substitution of these histidine residues to alanine residues mitigated the promotion of tyrosinase-induced A375 cell metastasis. Furthermore, melanin treatment enhanced A375 cell metastasis and phosphorylation of Cofilin. Thus, our findings suggest that tyrosinase increases the migration of A375 cells by regulating actin polymerization through its enzymatic activity.

Modeling Melanoma Heterogeneity In Vitro: Redox, Resistance and Pigmentation Profiles

Microenvironment and transcriptional plasticity generate subpopulations within the tumor, and the use of BRAF inhibitors (BRAFis) contributes to the rise and selection of resistant clones. We stochastically isolated subpopulations (C1, C2, and C3) from naïve melanoma and found that the clones demonstrated distinct morphology, phenotypic, and functional profiles: C1 was less proliferative, more migratory and invasive, less sensitive to BRAFis, less dependent on OXPHOS, more sensitive to oxidative stress, and less pigmented; C2 was more proliferative, less migratory and invasive, more sensitive to BRAFis, less sensitive to oxidative stress, and more pigmented; and C3 was less proliferative, more migratory and invasive, less sensitive to BRAFis, more dependent on OXPHOS, more sensitive to oxidative stress, and more pigmented. Hydrogen peroxide plays a central role in oxidative stress and cell signaling, and PRDXs are one of its main consumers. The intrinsically resistant C1 and C3 clones had lower MITF, PGC-1α, and PRDX1 expression, while C1 had higher AXL and decreased pigmentation markers, linking PRDX1 to clonal heterogeneity and resistance. PRDX2 is depleted in acquired BRAFi-resistant cells and acts as a redox sensor. Our results illustrate that decreased pigmentation markers are related to therapy resistance and decreased antioxidant defense.

Leukemia cancer cells and immune cells derived-exosomes: Possible roles in leukemia progression and therapy

Exosomes have a significant impact on tumor survival, proliferation, metastasis, and recurrence. They also open up new therapeutic options and aid in the pathological identification and diagnosis of cancers. Exosomes have been shown in numerous studies to be essential for facilitating cell-to-cell communication. In B-cell hematological malignancies, the proteins and RNAs that are encased by circulating exosomes are thought to represent prospective sources for therapeutic drugs as well as biomarkers for diagnosis and prognosis. Additionally, exosomes can offer a "snapshot" of the tumor and the metastatic environment at any given point in time. In this review study, we concluded that leukemia-derived exosomes could be utilized as prognostic, diagnostic, and therapeutic biomarkers for individuals suffering from leukemia. Moreover, clinical studies have demonstrated that immune cells like dendritic cells create exosomes, which have the ability to activate the immune system against leukemia.

Protocol for Testing Human Melanoma Exosomes that Shift the Healthy Phenotype of Human Dermal Cells

Exosomes are small membrane-derived vesicles that transmit DNA constituents, mRNAs, microRNAs, and proteins from donor cells to a receiver cell. Various cells comprising of mesenchymal, immune, and cancer cells discharge exosomes. Cancer cell exosomes form the entry and reprogramming of essentials connected to a tumor environment. Melanoma-derived exosomes transport diverse proteins such as c-MET and RAB27a, which leave a melanoma mark. Increased mesenchymal epithelial transition (MET) expressions in serum exosomes have been considered an indicator of disease progression. Meanwhile, RAB27a has been identified as being involved in exosome discharge and trafficking. Decreased expressions of RAB27a in human melanoma cells have shown to diminish exosome release.We examined the effects of the downregulation and upregulation of RAB27a and c-MET in human dermal fibroblasts by utilizing the isolated exosomes of malignant melanoma cell lines. Melanoma exosomes derived from cancer cells conveyed information to healthy dermal fibroblasts and stem cells while inducing phenotypic change. In this chapter, we show optimized protocols that were used by our group for in vitro analysis with melanoma exosomes.

RAB27B-regulated exosomes mediate LSC maintenance via resistance to senescence and crosstalk with the microenvironment

The fate of leukaemia stem cells (LSCs) is determined by both their inherent mechanisms and crosstalk with their niches. Although LSCs were confirmed to be eradicated by restarting senescence, the specific key regulators of LSC resistance to senescence and remodelling of the niche to obtain a microenvironment suitable for stemness remain unknown. Here, we found that RAB27B, a gene regulating exosome secretion, was overexpressed in LSCs and associated with the poor prognosis of acute myeloid leukaemia (AML) patients. The increased RAB27B in LSCs prevented their senescence and maintained their stemness in vitro and in vivo. Mechanically, the increased RAB27B expression in LSCs selectively promoted the loading and release of exosomes rich in senescence-inducing proteins by direct combination. Furthermore, RAB27B-regulated LSC-derived exosomes remodelled the niche and induced senescence of mesenchymal stem cells (MSCs) with increased RAB27B expression ex vivo and in vivo. The increased RAB27B in the senescent MSCs conversely promoted LSC maintenance ex vivo and in vivo via selective excretion of exosomes rich in stemness-promoting proteins. Therefore, we identified the specifically increased RAB27B in LSCs and their educated senescent MSCs as a hub molecule for LSC resistance to senescence and maintenance through crosstalk with its niche via selective exosome excretion.

Resveratrol Inhibits Hepatocellular Carcinoma Progression through Regulating Exosome Secretion

BACKGROUND AND OBJECTIVES

Resveratrol is a promising drug for tumor therapy, but its anti-tumor mechanism remains unclarified. The present study aimed to explore the effect of resveratrol on the secretion of exosomes and the role of resveratrol-induced exosomes in the progression of hepatocellular carcinoma.

METHODS

The number and contents of exosomes induced by resveratrol were determined by nanoparticle tracking analysis and high-throughput sequencing in Huh7 cells, respectively. Expression of Rab27a was assessed by western blotting and immunofluorescence. Cell proliferation, migration and epithelial-mesenchymal transition were examined with the stimuli of resveratrol and exosomes, the activity of autophagy and wnt/β-catenin signaling induced by resveratrol-induced exosomes and knockdown of lncRNA SNHG29 were monitored by western blotting and immunofluorescence.

RESULTS

It was found that resveratrol might inhibit the exosome secretion by down-regulating the expression of Rab27a, thereby suppressing the proliferation, migration and epithelial-mesenchymal transition of Huh7 cells. Moreover, resveratrol-induced exosomes could also inhibit the malignant phenotype of Huh7 cells via inhibiting the nuclear translocation of β-catenin and the activation of autophagy, which lncRNA SNHG29 might mediate.

CONCLUSION

Resveratrol inhibits hepatocellular carcinoma progression by regulating exosome secretion and contents.

The Regulation of Exosome Generation and Function in Physiological and Pathological Processes

Exosomes, a type of extracellular vesicle with a diameter of approximately 100 nm that is secreted by all cells, regulate the phenotype and function of recipient cells by carrying molecules such as proteins, nucleic acids, and lipids and are important mediators of intercellular communication. Exosomes are involved in various physiological and pathological processes such as immunomodulation, angiogenesis, tumorigenesis, metastasis, and chemoresistance. Due to their excellent properties, exosomes have shown their potential application in the clinical diagnosis and treatment of disease. The functions of exosomes depend on their biogenesis, uptake, and composition. Thus, a deeper understanding of these processes and regulatory mechanisms can help to find new targets for disease diagnosis and therapy. Therefore, this review summarizes and integrates the recent advances in the regulatory mechanisms of the entire biological process of exosomes, starting from the formation of early-sorting endosomes (ESCs) by plasma membrane invagination to the release of exosomes by fusion of multivesicular bodies (MVBs) with the plasma membrane, as well as the regulatory process of the interactions between exosomes and recipient cells. We also describe and discuss the regulatory mechanisms of exosome production in tumor cells and the potential of exosomes used in cancer diagnosis and therapy.

Invasion-Block and S-MARVEL: A high-content screening and image analysis platform identifies ATM kinase as a modulator of melanoma invasion and metastasis

Robust high-throughput assays are crucial for the effective functioning of a drug discovery pipeline. Herein, we report the development of Invasion-Block, an automated high-content screening platform for measuring invadopodia-mediated matrix degradation as a readout for the invasive capacity of cancer cells. Combined with Smoothen-Mask and Reveal, a custom-designed, automated image analysis pipeline, this platform allowed us to evaluate melanoma cell invasion capacity posttreatment with two libraries of compounds comprising 3840 U.S. Food and Drug Administration (FDA)-approved drugs with well-characterized safety and bioavailability profiles in humans as well as a kinase inhibitor library comprising 210 biologically active compounds. We found that Abl/Src, PKC, PI3K, and Ataxia-telangiectasia mutated (ATM) kinase inhibitors significantly reduced melanoma cell invadopodia formation and cell invasion. Abrogation of ATM expression in melanoma cells via CRISPR-mediated gene knockout reduced 3D invasion in vitro as well as spontaneous lymph node metastasis in vivo. Together, this study established a rapid screening assay coupled with a customized image-analysis pipeline for the identification of antimetastatic drugs. Our study implicates that ATM may serve as a potent therapeutic target for the treatment of melanoma cell spread in patients.

Engineered exosomes-based theranostic strategy for tumor metastasis and recurrence

Metastasis-associated processes are the predominant instigator of fatalities linked to cancer, wherein the pivotal role of circulating tumor cells lies in the resurgence of malignant growth. In recent epochs, exosomes, constituents of the extracellular vesicle cohort, have garnered attention within the field of tumor theranostics owing to their inherent attributes encompassing biocompatibility, modifiability, payload capacity, stability, and therapeutic suitability. Nonetheless, the rudimentary functionalities and limited efficacy of unmodified exosomes curtail their prospective utility. In an effort to surmount these shortcomings, intricate methodologies amalgamating nanotechnology with genetic manipulation, chemotherapy, immunotherapy, and optical intervention present themselves as enhanced avenues to surveil and intercede in tumor metastasis and relapse. This review delves into the manifold techniques currently employed to engineer exosomes, with a specific focus on elucidating the interplay between exosomes and the metastatic cascade, alongside the implementation of tailored exosomes in abating tumor metastasis and recurrence. This review not only advances comprehension of the evolving landscape within this domain but also steers the trajectory of forthcoming investigations.

Overexpression of RAB27A in Oral Squamous Cell Carcinoma Promotes Tumor Migration and Invasion via Modulation of EGFR Membrane Stability

Oral squamous cell carcinoma (OSCC) is the most prevalent subtype of head and neck tumors, highly prone to lymph node metastasis. This study aims to examine the expression pattern of Ras-related protein Rab-27A (RAB27A) and explore its potential implications in OSCC. The expression of RAB27A was assessed through immunohistochemical analysis utilizing tissue microarrays. In vitro experiments were conducted using RAB27A-knockdown cells to investigate its impact on OSCC tumor cells. Additionally, transcriptome sequencing was performed to elucidate potential underlying mechanisms. RAB27A was significantly overexpressed in OSCC, and particularly in metastatic lymph nodes. It was positively correlated with the clinical progression and poor survival prognosis. Silencing RAB27A notably decreased the proliferation, migration, and invasion abilities of OSCC cells in vitro. A Gene Ontology (GO) enrichment analysis indicated a strong association between RAB27A and the epidermal growth factor receptor (EGFR) signaling pathway. Further investigations revealed that RAB27A regulated the palmitoylation of EGFR via zinc finger DHHC-type containing 13 (ZDHHC13). These findings provide insights into OSCC progression and highlight RAB27A as a potential therapeutic target for combating this aggressive cancer.

Cutaneous squamous cell carcinoma-derived extracellular vesicles exert an oncogenic role by activating cancer-associated fibroblasts

Cutaneous squamous cell carcinoma (cSCC) is a fast-increasing cancer with metastatic potential. Extracellular vesicles (EVs) are small membrane-bound vesicles that play important roles in intercellular communication, particularly in the tumor microenvironment (TME). Here we report that cSCC cells secrete an increased number of EVs relative to normal human epidermal keratinocytes (NHEKs) and that interfering with the capacity of cSCC to secrete EVs inhibits tumor growth in vivo in a xenograft model of human cSCC. Transcriptome analysis of tumor xenografts by RNA-sequencing enabling the simultaneous quantification of both the human and the mouse transcripts revealed that impaired EV-production of cSCC cells prominently altered the phenotype of stromal cells, in particular genes related to extracellular matrix (ECM)-formation and epithelial-mesenchymal transition (EMT). In line with these results, co-culturing of human dermal fibroblasts (HDFs) with cSCC cells, but not with normal keratinocytes in vitro resulted in acquisition of cancer-associated fibroblast (CAF) phenotype. Interestingly, EVs derived from metastatic cSCC cells, but not primary cSCCs or NHEKs, were efficient in converting HDFs to CAFs. Multiplex bead-based flow cytometry assay and mass-spectrometry (MS)-based proteomic analyses revealed the heterogenous cargo of cSCC-derived EVs and that especially EVs derived from metastatic cSCCs carry proteins associated with EV-biogenesis, EMT, and cell migration. Mechanistically, EVs from metastatic cSCC cells result in the activation of TGFβ signaling in HDFs. Altogether, our study suggests that cSCC-derived EVs mediate cancer-stroma communication, in particular the conversion of fibroblasts to CAFs, which eventually contribute to cSCC progression.

The emerging role of MicroRNA-182 in tumorigenesis; a promising therapeutic target

A wide range of studies have indicated that microRNAs (miRNAs), a type of small single-stranded regulatory RNAs, are dysregulated in a different variety of human cancers. Therefore, they are expected to play important roles in tumorigenesis by functioning as oncogenic (oncomiRs) or tumor-suppressive miRNAs. Subsequently, their potential as diagnostic and therapeutic targets for malignancies has attracted attention in recent years. In particular, studies have revealed the aberrant expression of miR-182 through tumorigenesis and its important roles in various aspects of malignancies, including proliferation, metastasis, and chemoresistance. Accumulating reports have illustrated that miR-182, as a dual-role regulator, directly or indirectly regulates the expression of a wide range of genes and modulates the activity of various signaling pathways involved in tumor progression, such as JAK / STAT3, Wnt / β-catenin, TGF-β, and P13K / AKT. Therefore, considering the high therapeutic and diagnostic potential of miR-182, this review aims to point out the effects of miR-182 dysregulation on the signaling pathways involved in tumorigenesis.

Melanoma cells with acquired resistance to vemurafenib have decreased autophagic flux and display enhanced ability to transfer resistance

Over the last years, the incidence of melanoma, the deadliest form of skin cancer, has risen significantly. Nearly half of the melanoma patients exhibit the BRAF^V600E mutation. Although the use of BRAF and MEK inhibitors (BRAFi and MEKi) showed an impressive success rate in melanoma patients, durability of response remains an issue because tumor quickly becomes resistant. Here, we generated and characterized Lu1205 and A375 melanoma cells resistant to vemurafenib (BRAFi). Resistant cells (Lu1205R and A375R) exhibit higher IC₅₀ (5-6 fold increase) and phospho-ERK levels and 2-3 times reduced apoptosis than their sensitive parents (Lu1205S and A375S). Moreover, resistant cells are 2-3 times bigger, display a more elongated morphology and have a modulation the migration capacity. Interestingly, pharmacological inhibition of sphingosine kinases, that prevents sphingosine-1-phosphate production, reduces migration of Lu1205R cells by 50 %. In addition, although Lu1205R cells showed increased basal levels of the autophagy markers LC3II and p62, they have decreased autophagosome degradation and autophagy flux. Remarkably, expression of Rab27A and Rab27B, which are involved in the release of extracellular vesicles are dramatically augmented in resistant cells (i.e. 5-7 fold increase). Indeed, conditioned media obtained from Lu1205R cells increased the resistance to vemurafenib of sensitive cells. Hence, these results support that resistance to vemurafenib modulates migration and the autophagic flux and may be transferred to nearby sensitive melanoma cells by factors that are released to the extracellular milieu by resistant cells.

Neutrophils in Cancer and Potential Therapeutic Strategies Using Neutrophil-Derived Exosomes

Neutrophils are the most abundant immune cells and make up about 70% of white blood cells in human blood and play a critical role as the first line of defense in the innate immune response. They also help regulate the inflammatory environment to promote tissue repair. However, in cancer, neutrophils can be manipulated by tumors to either promote or hinder tumor growth depending on the cytokine pool. Studies have shown that tumor-bearing mice have increased levels of neutrophils in peripheral circulation and that neutrophil-derived exosomes can deliver various cargos, including lncRNA and miRNA, which contribute to tumor growth and degradation of extracellular matrix. Exosomes derived from immune cells generally possess anti-tumor activities and induce tumor-cell apoptosis by delivering cytotoxic proteins, ROS generation, H2O2 or activation of Fas-mediated apoptosis in target cells. Engineered exosome-like nanovesicles have been developed to deliver chemotherapeutic drugs precisely to tumor cells. However, tumor-derived exosomes can aggravate cancer-associated thrombosis through the formation of neutrophil extracellular traps. Despite the advancements in neutrophil-related research, a detailed understanding of tumor-neutrophil crosstalk is still lacking and remains a major barrier in developing neutrophil-based or targeted therapy. This review will focus on the communication pathways between tumors and neutrophils, and the role of neutrophil-derived exosomes (NDEs) in tumor growth. Additionally, potential strategies to manipulate NDEs for therapeutic purposes will be discussed.

Exosomes: Diagnostic and Therapeutic Implications in Cancer

Exosomes are a subset of extracellular vesicles produced by all cells, and they are present in various body fluids. Exosomes play crucial roles in tumor initiation/progression, immune suppression, immune surveillance, metabolic reprogramming, angiogenesis, and the polarization of macrophages. In this work, we summarize the mechanisms of exosome biogenesis and secretion. Since exosomes may be increased in the cancer cells and body fluids of cancer patients, exosomes and exosomal contents can be used as cancer diagnostic and prognostic markers. Exosomes contain proteins, lipids, and nucleic acids. These exosomal contents can be transferred into recipient cells. Therefore, this work details the roles of exosomes and exosomal contents in intercellular communications. Since exosomes mediate cellular interactions, exosomes can be targeted for developing anticancer therapy. This review summarizes current studies on the effects of exosomal inhibitors on cancer initiation and progression. Since exosomal contents can be transferred, exosomes can be modified to deliver molecular cargo such as anticancer drugs, small interfering RNAs (siRNAs), and micro RNAs (miRNAs). Thus, we also summarize recent advances in developing exosomes as drug delivery platforms. Exosomes display low toxicity, biodegradability, and efficient tissue targeting, which make them reliable delivery vehicles. We discuss the applications and challenges of exosomes as delivery vehicles in tumors, along with the clinical values of exosomes. In this review, we aim to highlight the biogenesis, functions, and diagnostic and therapeutic implications of exosomes in cancer.

The Roles of Exosomal Proteins: Classification, Function, and Applications

Exosome, a subpopulation of extracellular vesicles, plays diverse roles in various biological processes. As one of the most abundant components of exosomes, exosomal proteins have been revealed to participate in the development of many diseases, such as carcinoma, sarcoma, melanoma, neurological disorders, immune responses, cardiovascular diseases, and infection. Thus, understanding the functions and mechanisms of exosomal proteins potentially assists clinical diagnosis and targeted delivery of therapies. However, current knowledge about the function and application of exosomal proteins is still limited. In this review, we summarize the classification of exosomal proteins, and the roles of exosomal proteins in exosome biogenesis and disease development, as well as in the clinical applications.

Extracellular vesicles and melanoma: New perspectives on tumor microenvironment and metastasis

Secreted extracellular vesicles (EVs) are lipid bilayer particles without functional nucleus naturally released from cells which constitute an intercellular communication system. There is a broad spectrum of vesicles shed by cells based on their physical properties such as size (small EVs and large EVs), biogenesis, cargo and functions, which provide an increasingly heterogenous landscape. In addition, they are involved in multiple physiological and pathological processes. In cancer, EV release is opted by tumor cells as a beneficial process for tumor progression. Cutaneous melanoma is a cancer that originates from the melanocyte lineage and shows a favorable prognosis at early stages. However, when melanoma cells acquire invasive capacity, it constitutes the most aggressive and deadly skin cancer. In this context, extracellular vesicles have been shown their relevance in facilitating melanoma progression through the modulation of the microenvironment and metastatic spreading. In agreement with the melanosome secretory capacity of melanocytes, melanoma cells display an enhanced EV shedding activity that has contributed to the utility of melanoma models for unravelling EV cargo and functions within a cancer scenario. In this review, we provide an in-depth overview of the characteristics of melanoma-derived EVs and their role in melanoma progression highlighting key advances and remaining open questions in the field.

Extracellular Vesicles-Based Cell-Cell Communication in Melanoma: New Perspectives in Diagnostics and Therapy

Extracellular vesicles (EVs) are a heterogeneous group of cell-secreted particles that carry cargo of functional biomolecules crucial for cell-to-cell communication with both physiological and pathophysiological consequences. In this review, we focus on evidence demonstrating that the EV-mediated crosstalk between melanoma cells within tumor, between melanoma cells and immune and stromal cells, promotes immune evasion and influences all steps of melanoma development from local progression, pre-metastatic niche formation, to metastatic colonization of distant organs. We also discuss the role of EVs in the development of resistance to immunotherapy and therapy with BRAF^V600/MEK inhibitors, and shortly summarize the recent advances on the potential applications of EVs in melanoma diagnostics and therapy.

Exosome-Derived microRNA: Implications in Melanoma Progression, Diagnosis and Treatment

Melanoma is a malignant and aggressive cancer, and its progression is greatly affected by interactions between melanoma cells and their surroundings. Exploration on mechanism of melanoma and improved diagnostic and therapeutic strategies are becoming increasingly important. Unlike extracellular messengers that mainly work on targeted cells through corresponding receptors, exosomes are essential intercellular messengers that deliver biologically active substances such as nucleic acids and proteins to target cells for cell-cell communication. Of them, microRNAs (miRNAs) are common and important exosomal components that can regulate the expression of a wide range of target genes. Accordingly, exosome-derived miRNAs play a significant role in melanoma progression, including invasion and metastasis, microenvironment establishment, angiogenesis, and immune escape. MiRNA signatures of exosomes are specific in melanoma patients compared to healthy controls, thus circulating miRNAs, especially exosomal miRNAs, become potential diagnostic markers and therapeutic targets for melanoma. This review aims to summarize recent studies on the role of exosomal miRNAs in melanoma as well as ongoing efforts in melanoma treatment.

Circulating Exosomal miR-493-3p Affects Melanocyte Survival and Function by Regulating Epidermal Dopamine Concentration in Segmental Vitiligo

Circulating exosomal microRNAs have been used as potential biomarkers for various disorders. However, to date, the microRNA expression profile of circulating exosomes in patients with segmental vitiligo (SV) has not been identified. Thus, we aimed to identify the expression profile of circulating exosomal microRNAs and investigate their role in the pathogenesis of SV. Our study identified the expression profile of circulating exosomal microRNAs in SV and selected miR-493-3p as a candidate biomarker whose expression is significantly increased in circulating exosomes and perilesions in patients with SV. Circulating exosomes were internalized by human primary keratinocytes and increased dopamine secretion in vitro. Furthermore, miR-493-3p overexpression in keratinocytes increased dopamine concentration in the culture supernatant, which led to a significant increase in ROS and melanocyte apoptosis as well as a decrease in melanocyte proliferation and melanin synthesis in the coculture system by targeting HNRNPU. We also confirmed that HNRNPU could bind to and regulate COMT, a major degradative enzyme of dopamine. Hence, circulating exosomal miR-493-3p is a biomarker for SV, and the miR-493-3p/HNRNPU/COMT/dopamine axis may contribute to melanocyte dysregulation in the pathogenesis of SV.

RAB27A promotes the proliferation and invasion of colorectal cancer cells

Colorectal cancer (CRC) is one of the most commonly diagnosed cancer types worldwide. Despite significant advances in prevention and diagnosis, CRC is still one of the leading causes of cancer-related mortality globally. RAB27A, the member of RAB27 family of small GTPases, is the critical protein for intracellular secretion and has been reported to promote tumor progression. However, it is controversial for the role of RAB27A in CRC progression, so we explored the exact function of RAB27A in CRC development in this study. Based on the stable colon cancer cell lines of RAB27A knockdown and ectopic expression, we found that RAB27A knockdown inhibited proliferation and clone formation of SW480 colon cancer cells, whereas ectopic expression of RAB27A in RKO colon cancer cells facilitated cell proliferation and clone formation, indicating that RAB27A is critical for colon cancer cell growth. In addition, our data demonstrated that the migration and invasion of colon cancer cells were suppressed by RAB27A knockdown, but promoted by RAB27A ectopic expression. Therefore, RAB27A is identified as an onco-protein in mediating CRC development, which may be a valuable prognostic indicator and potential therapeutic target for CRC.

Melanoma stem cells promote metastasis via exosomal miR-1268a inactivation of autophagy

Background

Metastatic melanoma has a high mortality rate and poor survival. This is associated with efficient metastatic colonization, but the underlying mechanisms remain elusive. Communication between cancer stem cells (CSCs) and cancer cells plays an important role in metastatic dissemination. Whether cancer stem cells can alter the metastatic properties of non-CSC cells; and whether exosomal crosstalk can mediate such interaction, have not been demonstrated in melanoma prior to this report.

Results

The results revealed that exosomes secreted by highly metastatic melanoma CSCs (OL-SCs) promoted the invasiveness of the low metastatic melanoma cells (OL) and accelerated metastatic progression. miR-1268a was up-regulated in cells and exosomes of OL-SCs. Moreover, OL-SCs-derived exosomal miR-1268a, upon taking up by OL cells, promoted the metastatic colonization ability of OL cells in vitro and in vivo. In addition, the pro-metastatic activity of exosomal miR-1268a is achieved through inhibition of autophagy.

Conclusion

Our study demonstrates that OL cells can acquire the “metastatic ability” from OL-SCs cells. OL-SCs cells achieves this goal by utilizing its exosomes to deliver functional miRNAs, such as miR-1268a, to the targeted OL cells which in turn augments metastatic colonization by inactivating the autophagy pathway in OL cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40659-022-00397-z.

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.

Extracellular Vesicle/Macrophage Axis: Potential Targets for Inflammatory Disease Intervention

Extracellular vesicles (EVs) can regulate the polarization of macrophages in a variety of inflammatory diseases by mediating intercellular signal transduction and affecting the occurrence and development of diseases. After macrophages are regulated by EVs, they mainly show two phenotypes: the proinflammatory M1 type and the anti-inflammatory M2 type. A large number of studies have shown that in diseases such as mastitis, inflammatory bowel disease, Acute lung injury, and idiopathic pulmonary fibrosis, EVs promote the progression of the disease by inducing the M1-like polarization of macrophages. In diseases such as liver injury, asthma, and myocardial infarction, EVs can induce M2-like polarization of macrophages, inhibit the inflammatory response, and reduce the severity of the disease, thus indicating new pathways for treating inflammatory diseases. The EV/macrophage axis has become a potential target for inflammatory disease pathogenesis and comprehensive treatment. This article reviews the structure and function of the EV/macrophage axis and summarizes its biological functions in inflammatory diseases to provide insights for the diagnosis and treatment of inflammatory diseases.

Tumor-derived exosomes: the emerging orchestrators in melanoma

Cutaneous melanoma is an aggressive cancer type derived from melanocytes and its incidence has rapidly increased worldwide. Despite the vast improvement in therapy, melanoma is still confronted with high invasion, metastasis, and recurrence rate. Recent studies have confirmed that the exosomes are naturally occurring membranous extracellular vesicles with nano-sized lipid bilayers, performing as information messagers within cellular reciprocal action. Exosomes are unquestionably endowed with multifaceted roles in various diseases, including melanoma. Notably, tumor-derived exosomes play a pivotal role in conditioning the tumor microenvironment to promote the growth, metastasis, immune escape, and even drug-resistance of melanoma by transferring carcinogenic nucleic acids and proteins. Clinically, the dynamic expressions of exosomal components and loadings in melanoma patients with different tumor stages confer the clinical application of melanoma exosomes as diagnostic biomarkers. Hence, this review highlights the recent complicated roles and mechanisms of melanoma exosomes, as well as their potential as diagnostic and therapeutic targets in melanoma. The in-depth insights into the properties and behaviors of melanoma exosomes are of great potential to yield attractive therapeutic methods for melanoma.

Low-metastatic melanoma cells acquire enhanced metastatic capability via exosomal transfer of miR-199a-1-5p from highly metastatic melanoma cells

The mean survival of metastatic melanoma is less than 1 year. While the high mortality rate is associated with the efficient metastatic colonization of the involved organs, the underlying mechanisms remain elusive. The role of exosomes in facilitating the interactions between cancer cells and the metastatic microenvironment has received increasing attention. Previous studies on the role of exosomes in metastasis have been heavily focused on cancer cell-derived exosomes in modulating the functions of stromal cells. Whether the extravasated neighboring cancer cells at the distant organ can alter the metastatic properties of one another, a new mechanism of metastatic colonization, has not been demonstrated prior to this report. In this study, a paired M4 melanoma derivative cell lines, i.e., M14-OL and POL, that we established and characterized were employed. They exhibit high (POL cells) and low (OL cells) metastatic colonization efficiency in vivo, respectively. We show that exosomal crosstalk between metastatic cancer cells is a new mechanism that underlies cancer metastasis and heterogeneity. Low metastatic melanoma cells (OL) can acquire the “metastatic power” from highly metastatic melanoma cells (POL). POL achieves this goal by utilizing its exosomes to deliver functional miRNAs, such as miR-199a-1-5p, to the targeted OL cell which in turn inactivates cell cycle inhibitor CDKN1B and augments metastatic colonization.

Nanomaterial-based biosensor developing as a route toward in vitro diagnosis of early ovarian cancer

The grand challenges of ovarian cancer early diagnosis have led to an alarmingly high mortality rate from ovarian cancer (OC) in the past half century. In vitro diagnosis (IVD) has great potential in the early diagnosis of OC through non-invasive and dynamic analysis of biomarkers. However, common IVDs often fail to provide reliable test results due to lack of sensitivity, specificity, and convenience. In recent years, the discovery of new biomarkers and the progress of nanomaterials can solve the shortcomings of traditional IVD for early OC. These emerging biosensors based on nanomaterials offer great improvements in convenience, speed, selectivity, and sensitivity of IVD. In this review, we firstly systematically summarized the limits of commercial IVD biosensors of OC and the latest discovery of new biomarkers for OC. The representative optimization strategies for six potential ovarian cancer biomarkers are systematically discussed with emphasis on nanomaterial selection and the design of detection principles. Then, various strategies adopted by emerging biosensors based on nanomaterials are also introduced in detail, including optical, electrochemical, microfluidic, and surface plasmon sensors. Finally, current challenges of early OC IVD are proposed, and future research directions on this promising field are also discussed.

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Failure to diagnose OC early will lead to high mortality.

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The detection of OC-related biomarkers by IVD method will achieve early diagnosis of OC.

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The development of nanomaterials-based biosensors is expected to enhance efficiency of detection.

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Strategies and progress for nanomaterials-based biosensors are systematically reviewed.

BHMPS Inhibits Breast Cancer Migration and Invasion by Disrupting Rab27a-Mediated EGFR and Fibronectin Secretion

Simple Summary

Numerous studies targeting Rab GTPases and its multiple effectors have been attempted since exocytosis has been shown to alter tumor malignancy by modulating cancer cell behavior and tumor microenvironment. Here, we demonstrated that BHMPS inhibits migration and invasion of breast cancer cells by blocking the interaction between Rab27a and Slp4. BHMPS interfered with vesicle trafficking and secretion by decreasing FAK and JNK activation. In addition, BHMPS suppressed tumor growth in Rab27a-overexpressing MDA-MB-231 xenograft mice. This study highlighted the importance of understanding the mechanisms of Rab27a-mediated metastasis in improving the therapeutic options for metastatic cancers.

Abstract

Our previous work demonstrated that (E)-N-benzyl-6-(2-(3, 4-dihydroxybenzylidene) hydrazinyl)-N-methylpyridine-3-sulfonamide (BHMPS), a novel synthetic inhibitor of Rab27aSlp(s) interaction, suppresses tumor cell invasion and metastasis. Here, we aimed to further investigate the mechanisms of action and biological significance of BHMPS. BHMPS decreased the expression of epithelial-mesenchymal transition transcription factors through inhibition of focal adhesion kinase and c-Jun N-terminal kinase activation, thereby reducing the migration and invasion of breast cancer. Additionally, knockdown of Rab27a inhibited tumor migration, with changes in related signaling molecules, whereas overexpression of Rab27a reversed this phenomenon. BHMPS effectively prevented the interaction of Rab27a and its effector Slp4, which was verified by co-localization, immunoprecipitation, and in situ proximity ligation assays. BHMPS decreased the secretion of epidermal growth factor receptor and fibronectin by interfering with vesicle trafficking, as indicated by increased perinuclear accumulation of CD63-positive vesicles. Moreover, administration of BHMPS suppressed tumor growth in Rab27a-overexpressing MDA-MB-231 xenograft mice. These findings suggest that BHMPS may be a promising candidate for attenuating tumor migration and invasion by blocking Rab27a-mediated exocytosis.

Signal pathways of melanoma and targeted therapy

Melanoma is the most lethal skin cancer that originates from the malignant transformation of melanocytes. Although melanoma has long been regarded as a cancerous malignancy with few therapeutic options, increased biological understanding and unprecedented innovations in therapies targeting mutated driver genes and immune checkpoints have substantially improved the prognosis of patients. However, the low response rate and inevitable occurrence of resistance to currently available targeted therapies have posed the obstacle in the path of melanoma management to obtain further amelioration. Therefore, it is necessary to understand the mechanisms underlying melanoma pathogenesis more comprehensively, which might lead to more substantial progress in therapeutic approaches and expand clinical options for melanoma therapy. In this review, we firstly make a brief introduction to melanoma epidemiology, clinical subtypes, risk factors, and current therapies. Then, the signal pathways orchestrating melanoma pathogenesis, including genetic mutations, key transcriptional regulators, epigenetic dysregulations, metabolic reprogramming, crucial metastasis-related signals, tumor-promoting inflammatory pathways, and pro-angiogenic factors, have been systemically reviewed and discussed. Subsequently, we outline current progresses in therapies targeting mutated driver genes and immune checkpoints, as well as the mechanisms underlying the treatment resistance. Finally, the prospects and challenges in the development of melanoma therapy, especially immunotherapy and related ongoing clinical trials, are summarized and discussed.

The Challenging Melanoma Landscape: From Early Drug Discovery to Clinical Approval

Melanoma is recognized as the most dangerous type of skin cancer, with high mortality and resistance to currently used treatments. To overcome the limitations of the available therapeutic options, the discovery and development of new, more effective, and safer therapies is required. In this review, the different research steps involved in the process of antimelanoma drug evaluation and selection are explored, including information regarding in silico, in vitro, and in vivo experiments, as well as clinical trial phases. Details are given about the most used cell lines and assays to perform both two- and three-dimensional in vitro screening of drug candidates towards melanoma. For in vivo studies, murine models are, undoubtedly, the most widely used for assessing the therapeutic potential of new compounds and to study the underlying mechanisms of action. Here, the main melanoma murine models are described as well as other animal species. A section is dedicated to ongoing clinical studies, demonstrating the wide interest and successful efforts devoted to melanoma therapy, in particular at advanced stages of the disease, and a final section includes some considerations regarding approval for marketing by regulatory agencies. Overall, considerable commitment is being directed to the continuous development of optimized experimental models, important for the understanding of melanoma biology and for the evaluation and validation of novel therapeutic strategies.

Targeted Quantitative Profiling of GTP-Binding Proteins Associated with Metastasis of Melanoma Cells

Metastasis is a major obstacle in the therapeutic intervention of melanoma, and several GTP-binding proteins were found to play important roles in regulating cancer metastasis. To assess systematically the regulatory roles of these proteins in melanoma metastasis, we employed a targeted chemoproteomic method, which relies on the application of stable isotope-labeled desthiobiotin-GTP acyl phosphate probes in conjunction with scheduled multiple-reaction monitoring (MRM), for profiling quantitatively the GTP-binding proteins. Following probe labeling, tryptic digestion, and affinity pull-down of desthiobiotin-conjugated peptides, differences in expression levels of GTP-binding proteins in two matched pairs of primary/metastatic melanoma cell lines were measured using liquid chromatography-MRM analysis. We also showed that among the top upregulated proteins in metastatic melanoma cells, AK4 promotes the migration and invasion of melanoma cells; overexpression of AK4 in primary melanoma cells leads to augmented migration and invasion, and reciprocally, knockdown of AK4 in metastatic melanoma cells results in repressed invasiveness. In summary, we examined the relative expression levels of GTP-binding proteins in two pairs of primary/metastatic melanoma cell lines. Our results confirmed some previously reported regulators of melanoma metastasis and revealed a potential role of AK4 in promoting melanoma metastasis.

Visualizing murine breast and melanoma tumor microenvironment using intravital multiphoton microscopy

Intravital multiphoton imaging of the tumor milieu allows for the dissection of intricate and dynamic biological processes in situ. Herein, we present a step-by-step protocol for setting up an experimental cancer imaging model that has been optimized for solid tumors such as breast cancer and melanoma implanted in the flanks of mice. This protocol can be utilized for dissecting tumor-immune cell dynamics in vivo or other tumor-specific biological questions.

For complete details on the use of this protocol for intravital imaging of breast cancer, please refer to Tikoo et al. (2021a), and for intravital imaging of melanoma, please refer to Tikoo et al. (2021b).

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Detailed protocol for setting up high-resolution intravital imaging of murine tumors

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3D printing of custom stage inserts for tumor stabilization

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Procedures for cannulation of blood vessels

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Surgical preparation and tissue stabilization for imaging tumor milieu in vivo

Extracellular Vesicles as Mediators of Cancer Disease and as Nanosystems in Theranostic Applications

Cancer remains a leading cause of death worldwide despite decades of intense efforts to understand the molecular underpinnings of the disease. To date, much of the focus in research has been on the cancer cells themselves and how they acquire specific traits during disease development and progression. However, these cells are known to secrete large numbers of extracellular vesicles (EVs), which are now becoming recognized as key players in cancer. EVs contain a large number of different molecules, including but not limited to proteins, mRNAs, and miRNAs, and they are actively secreted by many different cell types. In the last two decades, a considerable body of evidence has become available indicating that EVs play a very active role in cell communication. Cancer cells are heterogeneous, and recent evidence reveals that cancer cell-derived EV cargos can change the behavior of target cells. For instance, more aggressive cancer cells can transfer their "traits" to less aggressive cancer cells and convert them into more malignant tumor cells or, alternatively, eliminate those cells in a process referred to as "cell competition". This review discusses how EVs participate in the multistep acquisition of specific traits developed by tumor cells, which are referred to as "the hallmarks of cancer" defined by Hanahan and Weinberg. Moreover, as will be discussed, EVs play an important role in drug resistance, and these more recent advances may explain, at least in part, why pharmacological therapies are often ineffective. Finally, we discuss literature proposing the use of EVs for therapeutic and prognostic purposes in cancer.

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.

RAB5A effect on metastasis of hepatocellular carcinoma cell line via altering the pro-invasive content of exosomes

Tumor microenvironment exerts a critical role in cancer progression and metastasis. Exosomes, cell-cell communicators and major players of the tumor microenvironment are considered as a serious mediator of cancer metastasis. Here, we determined the effect of RAB5A gene on the hepatocellular carcinoma (HCC) cells particularly whether RAB5A could affect HCC metastasis via regulating the pro-invasive content of exosomes. In response to RAB5A knockdown, we analyzed the proliferation rate and migration capability of HCC cells. Then, we estimated changes in the total protein composition of exosomes via analyzing the expression of exosomal markers, CD63 and Alix. Thereafter, alterations of the pro-invasive content of exosomes were functionally evaluated using matrigel invasion assay. Our results revealed that knockdown of RAB5A could decrease HCC cell proliferation rate and migration capability significantly. Moreover, no significant changes in the expression of exosomal CD63 and Alix reflected that no differences might be occurred in protein composition of RAB5A knockdown cell-derived exosomes. Matrigel invasion assay functionally showed that exosomes-derived from RAB5A knockdown cells still had pro-invasive properties and their pro-invasive content was not affected in response to RAB5A knockdown. In conclusion, we believe that our results propose a new explanation about RAB5A and metastatic potentials of exosomes-derived from HCC cells.

Exosomal CD47 Plays an Essential Role in Immune Evasion in Ovarian Cancer

Ovarian cancer is largely diagnosed at advanced stages upon detection of multiple peritoneal dissemination, resulting in poor outcomes. CD47 is overexpressed in tumors, facilitates tumor immune evasion, and is located on exosomes. We aimed to investigate the role of exosomal CD47 in ovarian cancer progression. Prognostic significance of CD47 expression in ovarian cancer was examined using a public database including 1,435 patients and validated with 26 patients at our institution. CD47 expression was associated with poor progression-free survival and inversely correlated with macrophage infiltration in ovarian cancer tissues. Exosomes were collected from ovarian cancer cell lines, and CD47 expression on exosomes was confirmed via flow cytometry. Inhibition of exosome secretion with GW4869 and exosome uptake with 5-(N-ethyl-N-isopropyl)-amiloride inhibited the surface CD47 expression on ovarian cancer cells and promoted phagocytosis by macrophages. RAB27A (a key regulator of exosome release) knockdown inhibited exosome secretion and led to CD47 downregulation in ovarian cancer cells. In a xenograft mouse model, suppression of the release of tumor-derived exosomes by GW4869 or RAB27A knockdown suppressed tumor progression and enhanced M1 macrophage phagocytosis in cancer tissues. Collectively, CD47 expression was correlated with poor prognoses in patients with ovarian cancer, suggesting the importance of immune evasion. CD47 was expressed on exosomes and the inhibition of exosome secretion and/or uptake enhanced cancer cell phagocytosis by macrophages, and thus, suppressed peritoneal dissemination. This suggests the potential of a novel immune checkpoint therapeutic agent that focuses on exosomes. IMPLICATIONS: Mechanistic insight from the current study suggests that exosomal CD47 may be an advantageous therapeutic target in ovarian cancer.

RAB1A regulates glioma cellular proliferation and invasion via the mTOR signaling pathway and epithelial-mesenchymal transition

Aim: We aimed at investigating the mechanism of RAB1A proliferation and invasion in gliomas. Materials & methods: Genome-wide expression profile data and immunohistochemistry were analyzed to assess RAB1A expression in gliomas. The Transwell assay, wound healing assay, brain slice coculture model, cellular fluorescence and intracranial xenograft model of nude mice were used to determine the proliferation and invasion of glioma cells. Results & conclusion: RAB1A was highly expressed in gliomas compared with normal brain tissue. The overall survival time of glioma patients with high RAB1A expression was significantly shortened. RAB1A regulated the activity of RAC1 by inhibiting the mTOR signaling pathway, affecting actin polymerization, cell morphology and cell polarity. RAB1A downregulation inhibited the epithelial-mesenchymal transition, proliferation and invasion of glioma cells.

3D Cell Cultures as Prospective Models to Study Extracellular Vesicles in Cancer

The improvement of culturing techniques to model the environment and physiological conditions surrounding tumors has also been applied to the study of extracellular vesicles (EVs) in cancer research. EVs role is not only limited to cell-to-cell communication in tumor physiology, they are also a promising source of biomarkers, and a tool to deliver drugs and induce antitumoral activity. In the present review, we have addressed the improvements achieved by using 3D culture models to evaluate the role of EVs in tumor progression and the potential applications of EVs in diagnostics and therapeutics. The most employed assays are gel-based spheroids, often utilized to examine the cell invasion rate and angiogenesis markers upon EVs treatment. To study EVs as drug carriers, a more complex multicellular cultures and organoids from cancer stem cell populations have been developed. Such strategies provide a closer response to in vivo physiology observed responses. They are also the best models to understand the complex interactions between different populations of cells and the extracellular matrix, in which tumor-derived EVs modify epithelial or mesenchymal cells to become protumor agents. Finally, the growth of cells in 3D bioreactor-like systems is appointed as the best approach to industrial EVs production, a necessary step toward clinical translation of EVs-based therapy.

Autophagy and Exosomes Relationship in Cancer: Friends or Foes?

Autophagy is an intracellular degradation process involved in the removal of proteins and damaged organelles by the formation of a double-membrane vesicle named autophagosome and degraded through fusion with lysosomes. An intricate relationship between autophagy and the endosomal and exosomal pathways can occur at different stages with important implications for normal physiology and human diseases. Recent researches have revealed that extracellular vesicles (EVs), such as exosomes, could have a cytoprotective role by inducing intracellular autophagy; on the other hand, autophagy plays a crucial role in the biogenesis and degradation of exosomes. Although the importance of these processes in cancer is well established, their interplay in tumor is only beginning to be documented. In some tumor contexts (1) autophagy and exosome-mediated release are coordinately activated, sharing the molecular machinery and regulatory mechanisms; (2) cancer cell-released exosomes impact on autophagy in recipient cells through mechanisms yet to be determined; (3) exosome-autophagy relationship could affect drug resistance and tumor microenvironment (TME). In this review, we survey emerging discoveries relevant to the exosomes and autophagy crosstalk in the context of cancer initiation, progression and recurrence. Consequently, we discuss clinical implications by targeting autophagy-exosomal pathway interaction and how this could lay a basis for the purpose of novel cancer therapeutics.

Exosomal miR-3180-3p inhibits proliferation and metastasis of non-small cell lung cancer by downregulating FOXP4

BACKGROUND

Non-small cell lung cancer (NSCLC) is one of the most malignant cancers worldwide and its pathogenesis is not completely clear. In this study, we explored the functions and mechanisms of exosomes transferring miR-3180-3p in NSCLC progression.

METHODS

The expression levels of miR-3180-3p in NSCLC tissues and paracarcinoma tissues was obtained from the GEO database (GEO: GSE53882). Exosomes derived from A549 cells were identified. Proliferation, migration and invasion were measured after treatment with exosomal miR-3180-3p or transfection using miR-3180-3p mimics. The relationship between miR-3180-3p and forkhead box P4 (FOXP4) was predicted using a bioinformatic tool and measured using a dual-luciferase reporter gene assay and western blotting. Finally, a mouse xenograft model of NSCLC cells was established to verify the function of exosomal miR-3180-3p in vivo.

RESULTS

We found that miR-3180-3p decreased in both NSCLC cell lines and patient tissues. Overexpression of miR-3180-3p or treatment with exosomal miR-3180-3p significantly suppressed cell proliferation and metastasis in NSCLC cell lines. Subsequently, we found miR-3180-3p downregulated FOXP4 protein expression levels. Furthermore, the volumes and weights of nude mouse tumors expressing exosomal miR-3180-3p were significantly reduced.

CONCLUSIONS

Exosomal miR-3180-3p suppresses NSCLC progression by downregulating FOXP4 expression.

KEY POINTS

SIGNIFICANT FINDINGS OF THE STUDY: We found that exosomal miR-3180-3p suppressed NSCLC progression and also identified a miR-3180-3p target gene. These findings provide a foundation to determine innovative therapeutic strategies.

WHAT THIS STUDY ADDS

This study contributes to research investigating exosomal containing miRNAs.

RAB5A is associated with genes involved in exosome secretion: Integration of bioinformatics analysis and experimental validation

Exosomes, as cell-cell communicators with an endosomal origin, are involved in the progression of various diseases. RAB5A, a member of the small Rab GTPases family, which is well known as a key regulator of cellular endocytosis, is expected to be involved in exosome secretion. Here, we found the impact of RAB5A on exosome secretion from human hepatocellular carcinoma cell line using a rapid yet reliable bioinformatics approach followed by experimental analysis. Initially, RAB5A and exosome secretion-related genes were gathered from bioinformatics tools, namely, CTD, COREMINE, and GeneMANIA; and published papers. Protein-protein interaction (PPI) was then constructed by the Search Tool for Retrieval of Interacting Genes (STRING) database. Among them, several genes with different combined scores were validated by the real-time quantitative polymerase chain reaction (RT-qPCR) in stable RAB5A knockdown cells. Thereafter, to validate the bioinformatics results functionally, the impact of RAB5A knockdown on exosome secretion was evaluated. Bioinformatics analysis showed that RAB5A interacts with 37 genes involved in exosome secretion regulatory pathways. Validation by RT-qPCR confirmed the association of RAB5A with candidate interacted genes and interestingly showed that even medium to low combined scores of the STRING database could be experimentally valid. Moreover, the functional analysis demonstrated that the stable silencing of RAB5A could experimentally decrease exosome secretion. In conclusion, we suggest RAB5A as a regulator of exosome secretion based on our bioinformatics approach and experimental analysis. Also, we propose the usage of PPI-derived from the STRING database regardless of their combined scores in advanced bioinformatics analysis.

Versatile Role of Rab27a in Glioma: Effects on Release of Extracellular Vesicles, Cell Viability, and Tumor Progression

Introduction: Glioma cells exert influence over the tumor-microenvironment in part through the release of extracellular vesicles (EVs), membrane-enclosed structures containing proteins, lipids, and RNAs. In this study, we evaluated the function of Ras-associated protein 27a (Rab27a) in glioma and evaluated the feasibility of assessing its role in EV release in glioma cells in vitro and in vivo. Methods: Rab27a was knocked down via a short hairpin RNA (shRNA) stably expressed in mouse glioma cell line GL261, with a scrambled shRNA as control. EVs were isolated by ultracentrifugation and quantified with Nanoparticle Tracking Analysis (NTA) and Tunable Resistive Pulse Sensing (TRPS). CellTiter-Glo viability assays and cytokine arrays were used to evaluate the impact of Rab27a knockdown. GL261.shRab27a cells and GL261.shControl were implanted into the left striatum of eight mice to assess tumor growth and changes in the tumor microenvironment. Results: Knockdown of Rab27a in GL261 glioma cells decreased the release of small EVs isolated at 100,000 × g in vitro (p = 0.005), but not the release of larger EVs, isolated at 10,000 × g. GL261.shRab27a cells were less viable compared to the scramble control in vitro (p < 0.005). A significant increase in CCL2 expression in shRab27a GL261 cells was also observed (p < 0.001). However, in vivo there was no difference in tumor growth or overall survival between the two groups, while shRab27a tumors showed lower proliferation at the tumor borders. Decreased infiltration of IBA1 positive macrophages and microglia, but not FoxP3 positive regulatory T cells was observed. Conclusion: Rab27a plays an important role in the release of small EVs from glioma cells, and also in their viability and expression of CCL2 in vitro. As interference in Rab27a expression influences glioma cell viability and expression profiles, future studies should be cautious in using the knockdown of Rab27a as a means of studying the role of small EVs in glioma growth.

7-dehydrocholesterol suppresses melanoma cell proliferation and invasion via Akt1/NF-κB signaling

Melanoma is the most lethal cutaneous cancer with a high metastatic rate worldwide, causing ~55,500 deaths annually. Although the selective B-Raf oncogene serine/threonine-kinase (BRAF) inhibitors, dabrafenib and vemurafenib, have been approved for the treatment of BRAF-mutant metastatic melanoma, the 5-year survival rate remains unfavorable due to acquired therapy resistance. Therefore, it is of great importance to develop alternative therapeutic drugs and uncover their mechanisms for the treatment of melanoma. 7-dehydrocholesterol (7-DHC) has been demonstrated to inhibit melanoma, but the mechanism is unclear. Therefore, the present study aimed to elucidate the mechanisms of the inhibitory effect of 7-DHC in melanoma cells via analyzing the proliferation, migration, apoptosis, cell cycle and transcriptional sequencing of melanoma cells treated with 7-DHC, as well as constructing a gene signature according to public data of patients with melanoma. In the present study, 7-DHC, the precursor of vitamin D₃, was able to induce apoptosis and inhibit cell proliferation and invasion of melanoma cells in a dose-dependent manner. RNA sequencing of melanoma cells treated with different concentrations of 7-DHC revealed that, compared with untreated melanoma cells, 65 genes were downregulated, and genes involved in the regulation of NF-ĸB import into the nucleus and NF-ĸB signaling were significantly repressed. Consistently, the Akt kinase family was one of most common somatic mutation hotspots in patients with melanoma according to The Cancer Genome Atlas enrichment analysis. Furthermore, 7-DHC decreased the phosphorylation of Akt1-Ser473 rather than that of MEK1, and the decreased phosphorylation of Akt1 subsequently inhibited the translocation of free RELA proto-oncogene NF-κB subunit to the nucleus. Finally, by intersecting downregulated genes by 7-DHC treatment and upregulated genes in patients with melanoma, a 7-DHC gene signature was identified, which was negatively associated with the prognosis. Overall, the present results demonstrated that 7-DHC suppressed melanoma cell proliferation and invasion via the Akt1/NF-ĸB signaling pathway, and 7-DHC key target genes were negatively associated with the prognosis. These findings highlight the potential application of 7-DHC for the treatment of melanoma in the future.

Rab27a deletion impairs the therapeutic potential of endothelial progenitor cells for myocardial infarction

Endothelial progenitor cell (EPC) transplantation has shown advantages in the treatment of myocardial infarction (MI) in animal models and clinical trials through mechanisms of direct intercellular contacts, autocrine, and paracrine. However, the effects of EPC transplantation for MI treatment remain controversial and the underlying mechanisms have not been fully elucidated. Here, we explored the role of Rab27a in the therapeutic potential of EPC transplantation in MI. We found that Rab27a knockout impaired the viability, and reduced the proliferation and tube formation function of ECPs. The recovery of cardiac function and improvement of ventricular remodeling from EPCs transplantation were significantly damaged by Rab27a deletion in vivo. Rab27a deletion inhibited the protein expression of phosphoinositide 3-kinase (PI3K) and cyclin D1 and the phosphorylation levels of Akt and FoxO3a. Therefore, Rab27a knockout suppressed the PI3K-Akt-FoxO3a/cyclin D1 signaling pathway. Furthermore, Rab27a ablation dramatically reduced exosome release in EPCs. These results demonstrated that Rab27a plays an essential role in EPC functions. The elucidation of this mechanism provides novel insights into EPC transplantation as a promising treatment for post-MI injuries.