Exosome-encapsulated miRNAs contribute to CXCL12/CXCR4-induced liver metastasis of colorectal cancer by enhancing M2 polarization of macrophages

Intracellular and extracellular factors of colorectal cancer liver metastasis: a pivotal perplex to be fully elucidated

Metastasis is the leading cause of death in colorectal cancer (CRC) patients, and the liver is the most common site of metastasis. Tumor cell metastasis can be thought of as an invasion-metastasis cascade and metastatic organotropism is thought to be a process that relies on the intrinsic properties of tumor cells and their interactions with molecules and cells in the microenvironment. Many studies have provided new insights into the molecular mechanism and contributing factors involved in CRC liver metastasis for a better understanding of the organ-specific metastasis process. The purpose of this review is to summarize the theories that explain CRC liver metastasis at multiple molecular dimensions (including genetic and non-genetic factors), as well as the main factors that cause CRC liver metastasis. Many findings suggest that metastasis may occur earlier than expected and with specific organ-anchoring property. The emergence of potential metastatic clones, the timing of dissemination, and the distinct routes of metastasis have been explained by genomic studies. The main force of CRC liver metastasis is also thought to be epigenetic alterations and dynamic phenotypic traits. Furthermore, we review key extrinsic factors that influence CRC cell metastasis and liver tropisms, such as pre-niches, tumor stromal cells, adhesion molecules, and immune/inflammatory responses in the tumor microenvironment. In addition, biomarkers associated with early diagnosis, prognosis, and recurrence of liver metastasis from CRC are summarized to enlighten potential clinical practice, including some markers that can be used as therapeutic targets to provide new perspectives for the treatment strategies of CRC liver metastasis.

Tumor-derived extracellular vesicles modulate innate immune responses to affect tumor progression

Immune cells are capable of influencing tumor progression in the tumor microenvironment (TME). Meanwhile, one mechanism by which tumor modulate immune cells function is through extracellular vesicles (EVs), which are cell-derived extracellular membrane vesicles. EVs can act as mediators of intercellular communication and can deliver nucleic acids, proteins, lipids, and other signaling molecules between cells. In recent years, studies have found that EVs play a crucial role in the communication between tumor cells and immune cells. Innate immunity is the first-line response of the immune system against tumor progression. Therefore, tumor cell-derived EVs (TDEVs) which modulate the functional change of innate immune cells serve important functions in the context of tumor progression. Emerging evidence has shown that TDEVs dually enhance or suppress innate immunity through various pathways. This review aims to summarize the influence of TDEVs on macrophages, dendritic cells, neutrophils, and natural killer cells. We also summarize their further effects on the progression of tumors, which may provide new ideas for developing novel tumor therapies targeting EVs.

Single-cell transcriptome analysis of tumor immune microenvironment characteristics in colorectal cancer liver metastasis

BACKGROUND

Liver metastasis is the leading cause of death in colorectal cancer (CRC) patients, and the precise mechanisms remain unclear. In this study, single-cell RNA sequencing (scRNA-seq) was used to analyze the cellular and molecular heterogeneity between CRC primary lesion and corresponding liver metastasis, and to clarify the characteristics of the tumor microenvironment (TME) in synchronous liver metastasis of CRC.

METHODS

A case of microsatellite stable (MSS) sigmoid carcinoma with synchronous liver metastasis was selected, and tissues from the primary tumor and the liver metastasis were collected for scRNA-seq. The EdgeR package software was used to identify the differentially expressed genes between cells. Gene Set Enrichment Analysis (GSEA) was performed and the clusterProfiler R package was used for Gene Ontology (GO) enrichment analysis. The SCENIC and CellphoneDB packages were used to reconstruct the transcriptional regulatory networks and to analyze the intercellular interaction network, respectively.

RESULTS

Compared to the primary tumor, the proportion of myeloid cells in the metastatic tumor was significantly increased, while B cells and plasma cells were decreased. In the metastatic tumor, the myeloid-derived suppressor cell (MDSC) characteristic gene, mannose receptor C-type 1 (MRC1) and tumor associated macrophage 2 (TAM2)-related gene, were highly expressed. Furthermore, angiogenesis, oxidative phosphorylation, and endothelial mesenchymal transition (EMT) of myeloid cells were also significantly enhanced. There were less myeloid cells in primary tumors, and these were mainly monocytes and TAM1; while the number of TAM2 was significantly upregulated in the metastatic samples. In liver metastasis, the T cell population was exhausted, and this was accompanied by a significant increase in the number of CD4+ T cells and a decrease in the number of CD8+ T cells. Furthermore, some immune checkpoint molecules were highly expressed. Interactions between myeloid cells and other cell populations appeared to be strong.

CONCLUSIONS

The TME of CRC liver metastasis is significantly immunosuppressed. Interactions between myeloid cells and other cell populations in the TME contribute to the establishment of a pro-metastatic niche that promotes colonization and growth of CRC cells in the liver. TAMs may be a potential immunotherapeutic target for MSS CRC.

Recent advances in the diagnostic and therapeutic roles of microRNAs in colorectal cancer progression and metastasis

Colorectal cancer (CRC) is the third most common malignancy in the world and one of the leading causes of cancer death; its incidence is still increasing in most countries. The early diagnostic accuracy of CRC is low, and the metastasis rate is high, resulting in a low survival rate of advanced patients. MicroRNAs (miRNAs) are a small class of noncoding RNAs that can inhibit mRNA translation and trigger mRNA degradation, and can affect a variety of cellular and molecular targets. Numerous studies have shown that miRNAs are related to tumour progression, immune system activity, anticancer drug resistance, and the tumour microenvironment. Dysregulation of miRNAs occurs in a variety of malignancies, including CRC. In this review, we summarize the recent research progress of miRNAs, their roles in tumour progression and metastasis, and their clinical value as potential biomarkers or therapeutic targets for CRC. Furthermore, we combined the roles of miRNAs in tumorigenesis and development with the therapeutic strategies of CRC patients, which will provide new ideas for the diagnosis and treatment of CRC.

Role of exosomal non-coding RNAs from tumor cells and tumor-associated macrophages in the tumor microenvironment

Exosomes have a crucial role in intercellular communication and mediate interactions between tumor cells and tumor-associated macrophages (TAMs). Exosome-encapsulated non-coding RNAs (ncRNAs) are involved in various physiological processes. Tumor-derived exosomal ncRNAs induce M2 macrophage polarization through signaling pathway activation, signal transduction, and transcriptional and post-transcriptional regulation. Conversely, TAM-derived exosomal ncRNAs promote tumor proliferation, metastasis, angiogenesis, chemoresistance, and immunosuppression. MicroRNAs induce gene silencing by directly targeting mRNAs, whereas lncRNAs and circRNAs act as miRNA sponges to indirectly regulate protein expressions. The role of ncRNAs in tumor-host interactions is ubiquitous. Current research is increasingly focused on the tumor microenvironment. On the basis of the "cancer-immunity cycle" hypothesis, we discuss the effects of exosomal ncRNAs on immune cells to induce T cell exhaustion, overexpression of programmed cell death ligands, and create a tumor immunosuppressive microenvironment. Furthermore, we discuss potential applications and prospects of exosomal ncRNAs as clinical biomarkers and drug delivery systems.

Metastasis suppressor NME1 in exosomes or liposomes conveys motility and migration inhibition in breast cancer model systems

Tumor-derived exosomes have documented roles in accelerating the initiation and outgrowth of metastases, as well as in therapy resistance. Little information supports the converse, that exosomes or similar vesicles can suppress metastasis. We investigated the NME1 (Nm23-H1) metastasis suppressor as a candidate for metastasis suppression by extracellular vesicles. Exosomes derived from two cancer cell lines (MDA-MB-231T and MDA-MB-435), when transfected with the NME1 (Nm23-H1) metastasis suppressor, secreted exosomes with NME1 as the predominant constituent. These exosomes entered recipient tumor cells, altered their endocytic patterns in agreement with NME1 function, and suppressed in vitro tumor cell motility and migration compared to exosomes from control transfectants. Proteomic analysis of exosomes revealed multiple differentially expressed proteins that could exert biological functions. Therefore, we also prepared and investigated liposomes, empty or containing partially purified rNME1. rNME1 containing liposomes recapitulated the effects of exosomes from NME1 transfectants in vitro. In an experimental lung metastasis assay the median lung metastases per histologic section was 158 using control liposomes and 15 in the rNME1 liposome group, 90.5% lower than the control liposome group (P = 0.016). The data expand the exosome/liposome field to include metastasis suppressive functions and describe a new translational approach to prevent metastasis.

Identification of Biomarkers Associated with Liver Metastasis Progression from Colorectal Cancer Using Exosomal RNA Profiling

This study aimed to identify novel biomarkers for metastatic colorectal cancer progression using exosomal RNA expression profiling. The exosomal RNA expression profiles of 54 patients with mCRC were investigated. Exosomal RNA profiling was performed at the time of relapse immediately before metastasectomy and cancer recurrence or progression after metastasectomy. The up- and down-regulated RNA expression profiles were screened and analyzed using H-cluster, principle component analysis and gene ontology. The tissue expression profile of the liver metastases was compared with the GSE 41258 set using GSEA tools. We identified two distinctive biological process gene sets (IFNA and PCDB families) related to metastatic progression. The interferon-α response gene set was enriched, especially when the tumor volume was ≥1 cm3. CXCL10, CXCL11 and SAMD 9 mRNA were highly expressed in the plasma exosome samples of patients with mCRC to the liver. Furthermore, high expression of CXCL10 but not CXCL11 or SAMD9 was associated with a poor prognosis and shorter progression-free survival. Conclusions: Cancer-derived exosomal CXCL10 may be a novel biomarker for liver metastasis of mCRC and a potential target for the prevention and treatment of mCRC with liver metastasis.

Mechanism underlying circRNA dysregulation in the TME of digestive system cancer

Circular RNAs (circRNAs) are a new series of noncoding RNAs (ncRNAs) that have been reported to be expressed in eukaryotic cells and have a variety of biological functions in the regulation of cancer pathogenesis and progression. The TME, as a microscopic ecological environment, consists of a variety of cells, including tumor cells, immune cells and other normal cells, ECM and a large number of signaling molecules. The crosstalk between circRNAs and the TME plays a complicated role in affecting the malignant behaviors of digestive system cancers. Herein, we summarize the mechanisms underlying aberrant circRNA expression in the TME of the digestive system cancers, including immune surveillance, angiogenesis, EMT, and ECM remodelling. The regulation of the TME by circRNA is expected to be a new therapeutic method.

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.

Protein tyrosine kinase inhibitor resistance in malignant tumors: molecular mechanisms and future perspective

Protein tyrosine kinases (PTKs) are a class of proteins with tyrosine kinase activity that phosphorylate tyrosine residues of critical molecules in signaling pathways. Their basal function is essential for maintaining normal cell growth and differentiation. However, aberrant activation of PTKs caused by various factors can deviate cell function from the expected trajectory to an abnormal growth state, leading to carcinogenesis. Inhibiting the aberrant PTK function could inhibit tumor growth. Therefore, tyrosine kinase inhibitors (TKIs), target-specific inhibitors of PTKs, have been used in treating malignant tumors and play a significant role in targeted therapy of cancer. Currently, drug resistance is the main reason for limiting TKIs efficacy of cancer. The increasing studies indicated that tumor microenvironment, cell death resistance, tumor metabolism, epigenetic modification and abnormal metabolism of TKIs were deeply involved in tumor development and TKI resistance, besides the abnormal activation of PTK-related signaling pathways involved in gene mutations. Accordingly, it is of great significance to study the underlying mechanisms of TKIs resistance and find solutions to reverse TKIs resistance for improving TKIs efficacy of cancer. Herein, we reviewed the drug resistance mechanisms of TKIs and the potential approaches to overcome TKI resistance, aiming to provide a theoretical basis for improving the efficacy of TKIs.

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.

Exosomal non-coding RNAs have a significant effect on tumor metastasis

Exosomes are produced by the majority of eukaryotic cells and are capable of transporting a variety of substances, including non-coding RNAs, between cells. Metastasis is a significant cause of death from cancer. Numerous studies have established an important role for exosomal non-coding RNAs in tumor metastasis. Exosomal non-coding RNAs from a variety of cells have been shown to affect tumor metastasis via several mechanisms. Exosomes transmit non-coding RNAs between tumor cells, fibroblasts, endothelial cells, and immune cells within the tumor microenvironment. Exosomal non-coding RNAs also have an effect on epithelial-mesenchymal transition, angiogenesis, and lymphangiogenesis. Exosomes derived from tumor cells have the ability to transport non-coding RNAs to distant organs, thereby facilitating the formation of the metastatic niche. Due to their role in tumor metastasis, exosomal non-coding RNAs have the potential to serve as diagnostic or prognostic markers as well as therapeutic targets for tumors. The purpose of this paper is to review and discuss the mechanisms of exosomal non-coding RNAs, their role in tumor metastasis, and their clinical utility, aiming to establish new directions for tumor metastasis, diagnosis, and treatment research.

Tyrosine kinase receptor RON activates MAPK/RSK/CREB signal pathway to enhance CXCR4 expression and promote cell migration and invasion in bladder cancer

Bladder cancer (BC) is one of the most lethal malignancies worldwide. The poor survival may be due to a high proportion of tumor metastasis. RON and CXCR4 are the key regulators of cell motility in BC, while the relationship between RON and CXCR4 remains elusive. In the present study, immunohistochemistry analysis of BC and adjacent normal tissues found that higher RON expression was positively correlated with CXCR4 expression. Inhibiting and replenishing RON level were used to regulate CXCR4 expression, observing the effects on migration and invasion of BC cells. Overexpression of RON reversed the inhibited cell migration and invasion following siCXCR4 treatment. Conversely, overexpression of CXCR4 restored the inhibition of cell migration and invasion caused by shRON. The activation of RON-MAPK/RSK/CREB pathway was demonstrated in BC cells under MSP treatment. Dual luciferase and CHIP assay showed that p-CREB targeted CXCR4 by binding to its CRE sequence. RON knockdown suppressed BC tumor growth in xenograft mouse tumors, accompanied by reduced expression of CXCR4. In conclusion, our data adds evidence that RON, a membrane tyrosine kinase receptor, promotes BC migration and invasion not only by itself, but also by activating MAPK/RSK/CREB signaling pathway to enhance CXCR4 expression.

YAP1-TEAD1 mediates the perineural invasion of prostate cancer cells induced by cancer-associated fibroblasts

Perineural invasion (PNI) driven by the tumor microenvironment (TME) has emerged as a key pattern of metastasis of prostate cancer (PCa), while its underlying mechanism is still elusive. Here, we identified increased CAFs and YAP1 expression levels in patients with metastatic PCa. In the cultured PCa cell line LNCaP, co-culture with cancer-associated fibroblasts (CAFs) could upregulate YAP1 protein expression. Either ectopic overexpression of YAP1 or co-culture with CAFs could promote the infiltration of LNCaPs towards dorsal root ganglia (DRG). This effect could be blocked using an YAP1 inhibitor. In vivo, overexpression of YAP1 could increase PNI in a mouse model of sciatic nerve tumor invasion. Mechanistically, TEAD1 binds to the NGF promotor and YAP1/TEAD1 activates its transcription and consequently increases NGF secretion. In turn, PCa cells treated with CM from CAFs or stable YAP1 overexpression can stimulate DRG to secrete CCL2. The epithelial-to-mesenchymal transition (EMT) of PCa cells is thus activated via CCL2/CCR2. Overall, our data demonstrate that CAFs can activate YAP1/TEAD1 signaling and increase the secretion of NGF, therefore promoting PCa PNI. In addition, EMT induced by PNI suggests a feedback loop is present between neurons and PCa cells.

Extracellular vesicles from colorectal cancer cells promote metastasis via the NOD1 signalling pathway

Pattern-recognition receptors (PRRs) have been shown to promote tumour metastasis via sensing tumour cell-derived small extracellular vesicles (EVs). Nucleotide-binding oligomerisation domain 1 (NOD1), a cytoplasmic PRR, plays a role in colorectal cancer (CRC) by detecting bacterial products. However, the precise mechanisms underlying the effects of NOD1, following identification of CRC cell-derived EVs (CRC-EVs), to potentiate CRC liver metastasis (CRC-LM), remain poorly understood. Here, we demonstrate that CRC-EVs activate NOD1 in macrophages to initiate secretion of inflammatory cytokines and chemokines. NOD1-activated macrophages also promote CRC cell migration, while in a murine model of liver metastasis (LM), NOD1-deficient mice exhibit reduced metastasis following CRC-EV treatment. Furthermore, cell division cycle 42 (CDC42), a small Rho guanosine-5'-triphosphate (GTP)ase, is delivered by CRC-EVs into macrophages where it activates NOD1. In addition, EVs from the plasma of patients with CRC-LM mediate NOD1 activation in human peripheral blood mononuclear cells. Moreover, high NOD1 expression in tumour tissues is associated with poor prognosis of CRC-LM. Our findings suggest that CRC-EVs activate NOD1 to promote tumour metastasis, thus, NOD1 may serve as a potential target in the diagnosis and treatment of CRC-LM.

Tumor-infiltrated activated B cells suppress liver metastasis of colorectal cancers

More than 40% of patients with late-stage colorectal cancer (CRC) develop liver metastasis (LM). Which immune cells play important roles in CRC-LM and contribute to the difference between left-sided CRC (LCC) and right-sided CRC (RCC) remain unclear. By single-cell RNA sequencing (scRNA-seq), we not only find that activated B cells are significantly depleted in CRC with LM, but also find a subtype of B cells developed from activated B cells, namely immature plasma cell population alpha (iMPA), highly correlated with metastasis. Mechanistically, inhibition of the Wnt and transforming growth factor β (TGF-β) pathways in cancer cell promotes activated B cell migration via the SDF-1-CXCR4 axis. This study reveals that B cell subpopulations in the tumor immune microenvironment (TIME) play a key role in CRC-LM as well as in LCC and RCC. The preventive effects of modulating B cell subpopulations in CRC may provide a rationale for subsequent drug development and CRC-LM management.

The potential role of exosomal miRNAs and membrane proteins in acute HIV-infected people

Exosomes play an important role during human immunodeficiency virus (HIV) acute infection. Yet, information regarding its cargo and its association with HIV rapid progressors (RPs) and typical progressors (TPs) remain largely unknown. In this study, exosomal miRNAs sequencing and mass cytometry were used to identify differential exosomal miRNAs and membrane proteins that participate in the pathogenesis of TPs and RPs. We discovered that miR-144-5p, miR-1180-3p, miR-451a, miR-362-5p, and miR-625-5p are associated with the TPs and miR-362-5p with the RPs. Decreased autophagy, amino acid metabolism, immune response, and IL-6 are closely related to RPs. In addition, SP1 was selected as the most significant transcription factor (TF) associated with disease progression. CD49D, CD5, CCR5, CD40, CD14, and CD86 were selected as the differential exosomal membrane proteins between TPs and RPs. This study provides valuable information for clarifying the mechanism in people with acute HIV infection.

Decellularized organ biomatrices facilitate quantifiable in vitro 3D cancer metastasis models

Metastatic cancers are chemoresistant, involving complex interplay between disseminated cancer cell aggregates and the distant organ microenvironment (extracellular matrix and stromal cells). Conventional metastasis surrogates (scratch/wound healing, Transwell migration assays) lack 3D architecture and ECM presence. Metastasis studies can therefore significantly benefit from biomimetic 3D in vitro models recapitulating the complex cascade of distant organ invasion and colonization by collective clusters of cells. We aimed to engineer reproducible and quantifiable 3D models of highly therapy-resistant cancer processes: (i) colorectal cancer liver metastasis; and (ii) breast cancer lung metastasis. Metastatic seeds are engineered using 3D tumor spheroids to recapitulate the 3D aggregation of cancer cells both in the tumor and in circulation throughout the metastatic cascade of many cancers. Metastatic soil was engineered by decellularizing porcine livers and lungs to generate biomatrix scaffolds, followed by extensive materials characterization. HCT116 colorectal and MDA-MB-231 breast cancer spheroids were generated on hanging drop arrays to initiate clustered metastatic seeding into liver and lung biomatrix scaffolds, respectively. Between days 3-7, biomatrix cellular colonization was apparent with increased metabolic activity and the presence of cellular nests evaluated via multiphoton microscopy. HCT116 and MDA-MB-231 cells colonized liver and lung biomatrices, and at least 15% of the cells invaded more than 20 μm from the surface. Engineered metastases also expressed increased signatures of genes associated with the metastatic epithelial to mesenchymal transition (EMT). Importantly, inhibition of matrix metalloproteinase-9 inhibited metastatic invasion into the biomatrix. Furthermore, metastatic nests were significantly more chemoresistant (>3 times) to the anti-cancer drug oxaliplatin, compared to 3D spheroids. Together, our data indicated that HCT116 and MDA-MB-231 spheroids invade, colonize, and proliferate in livers and lungs establishing metastatic nests in 3D settings in vitro. The metastatic nature of these cells was confirmed with functional readouts regarding EMT and chemoresistance. Modeling the dynamic metastatic cascade in vitro has potential to identify therapeutic targets to treat or prevent metastatic progression in chemoresistant metastatic cancers.

Regulatory Roles of Noncoding RNAs in the Progression of Gastrointestinal Cancers and Health Disparities

Annually, more than a million individuals are diagnosed with gastrointestinal (GI) cancers worldwide. With the advancements in radio- and chemotherapy and surgery, the survival rates for GI cancer patients have improved in recent years. However, the prognosis for advanced-stage GI cancers remains poor. Site-specific GI cancers share a few common risk factors; however, they are largely distinct in their etiologies and descriptive epidemiologic profiles. A large number of mutations or copy number changes associated with carcinogenesis are commonly found in noncoding DNA regions, which transcribe several noncoding RNAs (ncRNAs) that are implicated to regulate cancer initiation, metastasis, and drug resistance. In this review, we summarize the regulatory functions of ncRNAs in GI cancer development, progression, chemoresistance, and health disparities. We also highlight the potential roles of ncRNAs as therapeutic targets and biomarkers, mainly focusing on their ethnicity-/race-specific prognostic value, and discuss the prospects of genome-wide association studies (GWAS) to investigate the contribution of ncRNAs in GI tumorigenesis.

The value of exosome-derived noncoding RNAs in colorectal cancer proliferation, metastasis, and clinical applications

Colorectal cancer (CRC) is the third most common cancer in the world today, and its incidence and mortality rates are increasing every year. The ease of proliferation and metastasis of CRC has long been an important reason for its high mortality rate. Exosomes serve as key mediators that mediate communication between tumor cells and various other cells. Non-coding RNAs (ncRNAs) have been shown to play a key role in apoptosis, immunosuppression and proliferation metastasis in cancer. ncRNAs are loaded on exosomes and initiate the onset of metastasis by promoting epithelial-mesenchymal transition (EMT) at the primary site of the tumor. Meanwhile, exosome-derived ncRNAs construct a pre-metastatic niche (PMN) for CRC metastasis by forming an inflammatory microenvironment in distant organs, immunosuppression, and promoting angiogenesis and remodeling of the extracellular matrix. Here, we summarize the specific mechanisms associated with exosome-derived ncRNAs promoting local invasion and metastasis in CRC. Finally, we focus on their value for clinical application in future CRC diagnosis and treatment.

EV-miRome-wide profiling uncovers miR-320c for detecting metastatic colorectal cancer and monitoring the therapeutic response

PURPOSE

Molecular composition of circulating small extracellular vesicles (EVs) does not merely reflect the cells of origin, but also is enriched in specific biomolecules directly associated with the cellular transformation. However, while most of the currently identified EV-miRs are only geared towards one-dimensional disease detection, their application for long-term tracking and treatment response monitoring has been largely elusive.

METHODS

We established and optimized a rapid, sensitive and robust liquid biopsy sampling method, and further used small RNA sequencing to comprehensively catalogue EV-miRomes in association with the progression and outcome of metastatic colorectal cancer (mCRC).

RESULTS

By cross-comparison of EV-miRomes (n = 290) from multi-stage and longitudinal cohorts, we uncovered a 15-EV-miR signature with dual detection and long-term monitoring of tumor size progression for mCRC. From this panel, EV-miR-320c was uncovered as a strong clinical marker - aside from its diagnostic power and a therapeutic monitoring performance superior to carcinoembryonic antigen (CEA), its high expression has also been linked to lower overall survival and a greater likelihood of disease recurrence. Further, integrative analyses of tissue transcriptomic and liquid biopsy implicated this 15-EV-miR signature in programming the mesenchymal-epithelial transition (MET) for distant localization of the metastasized cells and also in creating a tumor-favoring metastatic niche.

CONCLUSION

Our clinically-oriented delineation of the mCRC-associated circulating EV-miRomes systematically revealed the functional significance of these liquid biopsy markers and further strengthen their translational potential in mCRC therapeutic monitoring.

Cytokine- and chemokine-induced inflammatory colorectal tumor microenvironment: Emerging avenue for targeted therapy

Colorectal cancer (CRC) is a predominant life-threatening cancer, with liver and peritoneal metastases as the primary causes of death. Intestinal inflammation, a known CRC risk factor, nurtures a local inflammatory environment enriched with tumor cells, endothelial cells, immune cells, cancer-associated fibroblasts, immunosuppressive cells, and secretory growth factors. The complex interactions of aberrantly expressed cytokines, chemokines, growth factors, and matrix-remodeling enzymes promote CRC pathogenesis and evoke systemic responses that affect disease outcomes. Mounting evidence suggests that these cytokines and chemokines play a role in the progression of CRC through immunosuppression and modulation of the tumor microenvironment, which is partly achieved by the recruitment of immunosuppressive cells. These cells impart features such as cancer stem cell-like properties, drug resistance, invasion, and formation of the premetastatic niche in distant organs, promoting metastasis and aggressive CRC growth. A deeper understanding of the cytokine- and chemokine-mediated signaling networks that link tumor progression and metastasis will provide insights into the mechanistic details of disease aggressiveness and facilitate the development of novel therapeutics for CRC. Here, we summarized the current knowledge of cytokine- and chemokine-mediated crosstalk in the inflammatory tumor microenvironment, which drives immunosuppression, resistance to therapeutics, and metastasis during CRC progression. We also outlined the potential of this crosstalk as a novel therapeutic target for CRC. The major cytokine/chemokine pathways involved in cancer immunotherapy are also discussed in this review.

Astragalus mongholicus Bunge-Curcuma aromatica Salisb. suppresses growth and metastasis of colorectal cancer cells by inhibiting M2 macrophage polarization via a Sp1/ZFAS1/miR-153-3p/CCR5 regulatory axis

Colorectal cancer (CRC) is regarded as one of the commonest cancer types around the world. Due to the poor understanding on the causes of CRC formation and progression, this study sets out to investigate the physiological mechanisms by which Astragalus mongholicus Bunge-Curcuma aromatica Salisb. (ARCR) regulates CRC growth and metastasis, and the role in which M2 macrophage polarization plays in this process. An orthotopic-transplant model of CRC was established to evaluate the influence of ARCR on the polarization of M2 macrophage and the growth and metastasis of tumors. Next, the binding affinity among Sp1, ZFAS1, miR-153-5p, and CCR5 was identified using multiple assays. Finally, after co-culture of bone marrow-derived macrophages (BMDM) with CRC cell line CT26.WT, the cell proliferative, invasive, and migrated abilities were assessed in gain- or loss-of-function experiments. ARCR inhibited the infiltration of M2 macrophages into tumor microenvironment to suppress the CRC growth and metastasis in vivo. Additionally, ARCR inhibited the transcription of ZFAS1 by reducing Sp1 expression to repress M2 macrophage polarization. Moreover, ZFAS1 competitively binds to miR-153-3p to upregulate the CCR5 expression. Finally, ARCR suppressed the polarization of M2 macrophages to inhibit the tumor growth and tumor metastasis in CRC by mediating the Sp1/ZFAS1/miR-153-3p/CCR5 regulatory axis. Collectively, ARCR appears to suppress the CRC cell growth and metastasis by suppressing M2 macrophage polarization via Sp1/ZFAS1/miR-153-3p/CCR5 regulatory axis. 1. ARCR suppress the CRC cell growth and metastasis 2. ZFAS1 promotes CCR5 expression by competitively binding to miR-153-3p. 3. Sp1 promotes M2 macrophage polarization by activating ZFAS1 via miR-153-3p/CCR5. 4. The study unveiled a protective target against CRC.

Recent Advances in CXCL12/CXCR4 Antagonists and Nano-Based Drug Delivery Systems for Cancer Therapy

Chemokines can induce chemotactic cell migration by interacting with G protein-coupled receptors to play a significant regulatory role in the development of cancer. CXC chemokine-12 (CXCL12) can specifically bind to CXC chemokine receptor 4 (CXCR4) and is closely associated with the progression of cancer via multiple signaling pathways. Over recent years, many CXCR4 antagonists have been tested in clinical trials; however, Plerixafor (AMD3100) is the only drug that has been approved for marketing thus far. In this review, we first summarize the mechanisms that mediate the physiological effects of the CXCL12/CXCR4 axis. Then, we describe the use of CXCL12/CXCR4 antagonists. Finally, we discuss the use of nano-based drug delivery systems that exert action on the CXCL12/CXCR4 biological axis.

Chemokines in progression, chemoresistance, diagnosis, and prognosis of colorectal cancer

Plenty of factors affect the oncogenesis and progression of colorectal cancer in the tumor microenvironment, including various immune cells, stromal cells, cytokines, and other factors. Chemokine is a member of the cytokine superfamily. It is an indispensable component in the tumor microenvironment. Chemokines play an antitumor or pro-tumor role by recruitment or polarization of recruiting immune cells. Meanwhile, chemokines, as signal molecules, participate in the formation of a cross talk among signaling pathways and non-coding RNAs, which may be involved in promoting tumor progression. In addition, they also function in immune escape. Chemokines are related to drug resistance of tumor cells and may even provide reference for the diagnosis, therapy, and prognosis of patients with colorectal cancer.

The Significance of MicroRNAs in the Molecular Pathology of Brain Metastases

Brain metastases are the most frequent intracranial tumors in adults and the cause of death in almost one-fourth of cases. The incidence of brain metastases is steadily increasing. The main reason for this increase could be the introduction of new and more efficient therapeutic strategies that lead to longer survival but, at the same time, cause a higher risk of brain parenchyma infiltration. In addition, the advances in imaging methodology, which provide earlier identification of brain metastases, may also be a reason for the higher recorded number of patients with these tumors. Metastasis is a complex biological process that is still largely unexplored, influenced by many factors and involving many molecules. A deeper understanding of the process will allow the discovery of more effective diagnostic and therapeutic approaches that could improve the quality and length of patient survival. Recent studies have shown that microRNAs (miRNAs) are essential molecules that are involved in specific steps of the metastatic cascade. MiRNAs are endogenously expressed small non-coding RNAs that act as post-transcriptional regulators of gene expression and thus regulate most cellular processes. The dysregulation of these molecules has been implicated in many cancers, including brain metastases. Therefore, miRNAs represent promising diagnostic molecules and therapeutic targets in brain metastases. This review summarizes the current knowledge on the importance of miRNAs in brain metastasis, focusing on their involvement in the metastatic cascade and their potential clinical implications.

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.

Exosomal microRNA-25 released from cancer cells targets SIK1 to promote hepatocellular carcinoma tumorigenesis

BACKGROUND

Hepatocellular carcinoma (HCC) is recognized as a leading cause of cancer-associated fatality worldwide. Our study here aimed to probe the mechanism by which exosomes secreted by CSQT-2, an HCC cell line, affected the progression of HCC.

METHODS

Exosomes were extracted from CSQT-2 cells. Colony formation, Transwell, sphere formation and flow cytometric analyses were applied to assess cell biological activities. Microarray analysis detected the change of microRNA (miRNA) expression after exosome treatment, followed by RT-qPCR validation. Luciferase reporter was applied to detect the binding between SIK1 and miR-25. Xenograft studies in nude mice manifested tumor growth and metastatic ability of miR-25 and SIK1.

RESULTS

The exosome treatment enhanced cell malignant phenotype in vitro and tumor growth and liver and lung metastases in vivo. The exosomes elevated miR-25 expression in HCC cells. miR-25 targeted SIK1 which was decreased in the exosomes-treated cells. miR-25 inhibitor reduced cell malignant phenotype and attenuated tumorigenesis and metastasis in vivo. SIK1 silencing reversed the effect of miR-25 inhibitor. The exosome treatment potentiated the Wnt/β-catenin pathway in cells, whereas miR-25 inhibitor blunted the pathway activity.

CONCLUSION

MiR-25 shuttled through CSQT-2-derived exosomes promoted the development of HCC by reducing SIK1 expression and potentiating the Wnt/β-catenin pathway.

Cancer-associated fibroblast-derived exosomal microRNA-20a suppresses the PTEN/PI3K-AKT pathway to promote the progression and chemoresistance of non-small cell lung cancer

BACKGROUND

Cancer-associated fibroblasts (CAFs) contributes to overall tumor progression. In the current survey, we explored the ability of microRNA-20a (miR-20a) within these CAF-derived exosomes to influence non-small-cell lung cancer (NSCLC) progression.

MATERIALS AND METHODS

Normal tissue-associated fibroblasts (NAFs) and CAFs were collected from samples of NSCLC patient tumors and paracancerous lung tissues. Exosomes derived from these cells were then characterized via Western blotting, nanoparticle tracking analyses, and transmission electron microscopy. The expression of miR-20a was assessed via qPCR and fluorescence in situ hybridization (FISH). CCK-8, EdU uptake, and colony formation assessments were used for evaluating tumor proliferation, while Hoechst staining was performed to monitor the in vitro apoptotic death of tumor cells. A model of xenograft tumor established in nude mice was also used to evaluate in vivo tumor responses.

RESULTS

CAF-derived exosomes exhibited miR-20a upregulation and promoted NSCLC cell proliferation and resistance to cisplatin (DDP). Mechanistically, CAF-derived exosomes were discovered to transmit miR-20a to tumor cells wherein it was able to target PTEN to enhance DDP resistance and proliferation. Associated PTEN downregulation following exosome-derived miR-20a treatment enhanced PI3K/AKT pathway activation.

CONCLUSION

The achieved outcomes explain that CAFs can release miR-20a-containing exosomes capable of promoting NSCLC progression and chemoresistance, highlighting this pathway as a possible therapeutic target in NSCLC.

Macrophages Are a Double-Edged Sword: Molecular Crosstalk between Tumor-Associated Macrophages and Cancer Stem Cells

Cancer stem cells (CSCs) are a subset of highly tumorigenic cells in tumors. They have enhanced self-renewal properties, are usually chemo-radioresistant, and can promote tumor recurrence and metastasis. They can recruit macrophages into the tumor microenvironment and differentiate them into tumor-associated macrophages (TAMs). TAMs maintain CSC stemness and construct niches that are favorable for CSC survival. However, how CSCs and TAMs interact is not completely understood. An understanding on these mechanisms can provide additional targeting strategies for eliminating CSCs. In this review, we comprehensively summarize the reported mechanisms of crosstalk between CSCs and TAMs and update the related signaling pathways involved in tumor progression. In addition, we discuss potential therapies targeting CSC–TAM interaction, including targeting macrophage recruitment and polarization by CSCs and inhibiting the TAM-induced promotion of CSC stemness. This review also provides the perspective on the major challenge for developing potential therapeutic strategies to overcome CSC-TAM crosstalk.

Exosome-Derived Non-Coding RNAs in the Tumor Microenvironment of Colorectal Cancer: Possible Functions, Mechanisms and Clinical Applications

Colorectal cancer (CRC) is the second leading cause of cancer death and the third most prevalent malignancy. Colorectal tumors exchange information with the surrounding environment and influence each other, which collectively constitutes the tumor microenvironment (TME) of CRC. Many studies have shown that exosome-derived non-coding RNAs (ncRNAs) play important roles in various pathophysiological processes by regulating the TME of CRC. This review summarizes recent findings on the fundamental roles of exosomal ncRNAs in angiogenesis, vascular permeability, tumor immunity, tumor metabolism and drug resistance. Certainly, the in-depth understanding of exosomal ncRNAs will provide comprehensive insights into the clinical application of these molecules against CRC.

The Interaction Between Epigenetic Changes, EMT, and Exosomes in Predicting Metastasis of Colorectal Cancers (CRC)

Worldwide, colorectal cancer (CRC) ranks as the third most common malignancy, and the second most deadly with nearly one million attributable deaths in 2020. Metastatic disease is present in nearly 25% of newly diagnosed CRC, and despite advances in chemotherapy, less than 20% will remain alive at 5 years. Epigenetic change plays a key role in the epithelial-to-mesenchymal transition (EMT), which is a crucial phenotype for metastasis and mainly includes DNA methylation, non-coding RNAs (ncRNAs), and N6-methyladenosine (m6A) RNA, seemingly valuable biomarkers in CRCs. For ncRNAs, there exists a “molecular sponge effect” between long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), and microRNAs (miRNAs). The detection of exosomes is a novel method in CRC monitoring, especially for predicting metastasis. There is a close relationship between exosomes and EMT in CRCs. This review summarizes the close relationship between epigenetic changes and EMT in CRCs and emphasizes the crucial function of exosomes in regulating the EMT process.

Small Extracellular Vesicles: Key Forces Mediating the Development and Metastasis of Colorectal Cancer

Colorectal cancer (CRC) is the third most common cancer worldwide, and its incidence and mortality rates have been increasing annually in recent years. A variety of different small extracellular vesicles (sEVs) are important mediators of intercellular communication and have an important role in tumor metastasis and progression. The development and metastasis of CRC are closely linked to tumor-cell-derived sEVs, non-tumor-cell-derived sEVs, and intestinal-microbiota-derived sEVs. Numerous studies have shown that the tumor microenvironment (TME) is a key component in the regulation of CRC proliferation, development, and metastasis. These sEVs can create a TME conducive to CRC growth and metastasis by forming an immunosuppressive microenvironment, remodeling the extracellular matrix, and promoting tumor cell metabolism. Therefore, in this paper, we review the role of different types of sEVs in colorectal cancer development and metastasis. Furthermore, based on the properties of sEVs, we further discuss the use of sEVs as early biomarkers for colorectal cancer diagnosis and the potential for their use in the treatment of CRC.

Exosomal microRNAs shuttling between tumor cells and macrophages: cellular interactions and novel therapeutic strategies

Extracellular vesicles secreted by tumor microenvironment (TME) cells are vital players in tumor progression through transferring nucleic acids and proteins. Macrophages are the main immune cells in TME and tumor associated macrophages (TAM) express M2 phenotype, which induce tumor proliferation, angiogenesis, invasion, metastasis and immune elimination, resulting in the subsequent evolution of malignancies. There are a high number of studies confirmed that tumor cells and TAM interact with each other through extracellular vesicles in various cancers, like pancreatic ductal adenocarcinoma, gastric cancer, breast cancer, ovarian cancer, colon cancer, glioblastoma, hepatocellular cancer, and lung cancer. Herein, this review summarizes the current knowledge on mechanisms of communications between tumor cells and TAM via extracellular vesicles, mainly about microRNAs, and targeting these events might represent a novel approach in the clinical implications of this knowledge into successful anti-cancer strategies.

Single-cell landscape of immunocytes in patients with extrahepatic cholangiocarcinoma

Background

The intricate landscape of immunocytes in the tumor microenvironment (TME) is fundamental to immunotherapy but notably under-researched in extrahepatic cholangiocarcinoma (ECCA).

Methods

Single-cell RNA sequencing technology was conducted to make an in-depth analysis of immunocytes from matched tumor tissues, paratumor tissues and peripheral blood from ECCA patients. The potential cellular interactions between two cell populations were analyzed with software CellPhoneDB (v2.1.7).

Results

We obtained 13526 cells and characterized the transcriptomes and heterogeneity of different clusters and subclusters of immunocytes from ECCA, including CD4+ T cells, CD8+ T cells, B cells and myeloid immunocytes. We observed the rarely described immunocyte subclusters "intermediate" exhausted CD8+ T (CD8+ Tex) cells and “nonclassic” plasmacytes (CD27+ CD138+ CD38−). In addition, we identified potential immunotherapy targets, for example, ACP5, MAGEH1, TNFRSF9 and CCR8 for Tregs and MT1 for CD8+ Tex cells. We also found strong cellular interactions among Treg cells, M2 macrophages and CD8+ Tex cells through ligand–receptor analysis, implying that potential cellular cross-linkage promoted the immunosuppressive nature of the TME.

Conclusions

In a word, our study illuminated the components of the TME and revealed potential cellular interactions at the individual cellular level in ECCA, we aimed to provide a new perspective for further immunological studies and immunotherapy of ECCA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03424-5.

Single-cell sequencing: a promising approach for uncovering the mechanisms of tumor metastasis

Single-cell sequencing (SCS) is an emerging high-throughput technology that can be used to study the genomics, transcriptomics, and epigenetics at a single cell level. SCS is widely used in the diagnosis and treatment of various diseases, including cancer. Over the years, SCS has gradually become an effective clinical tool for the exploration of tumor metastasis mechanisms and the development of treatment strategies. Currently, SCS can be used not only to analyze metastasis-related malignant biological characteristics, such as tumor heterogeneity, drug resistance, and microenvironment, but also to construct metastasis-related cell maps for predicting and monitoring the dynamics of metastasis. SCS is also used to identify therapeutic targets related to metastasis as it provides insights into the distribution of tumor cell subsets and gene expression differences between primary and metastatic tumors. Additionally, SCS techniques in combination with artificial intelligence (AI) are used in liquid biopsy to identify circulating tumor cells (CTCs), thereby providing a novel strategy for treating tumor metastasis. In this review, we summarize the potential applications of SCS in the field of tumor metastasis and discuss the prospects and limitations of SCS to provide a theoretical basis for finding therapeutic targets and mechanisms of metastasis.

Non-Coding RNAs Implicated in the Tumor Microenvironment of Colorectal Cancer: Roles, Mechanisms and Clinical Study

Colorectal cancer (CRC) is one of the most common malignant tumors. The morbidity and mortality rates have been increasing all over the world. It is critical to elucidate the mechanism of CRC occurrence and development. However, tumor microenvironment (TME) includes immune cells, fibroblasts, endothelial cells, cytokines, chemokines and other components that affect the progression of CRC and patients' prognosis. Non-coding RNAs (ncRNAs) including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), circular RNAs (circRNAs) without protein-coding ability have been shown to engage in tumor microenvironment-mediated angiogenesis and metastasis. Therefore, clarifying the mechanism of ncRNAs regulating the microenvironment is very important to develop the therapeutic target of CRC and improve the survival time of patients. This review focuses on the role and mechanism of ncRNAs in the CRC microenvironment and puts forward possible clinical treatment strategies.

Exosomal miR-146a-5p and miR-155-5p promote CXCL12/CXCR7-induced metastasis of colorectal cancer by crosstalk with cancer-associated fibroblasts

C-X-C motif chemokine receptor 7 (CXCR7) is a newly discovered atypical chemokine receptor that binds to C-X-C motif chemokine ligand 12 (CXCL12) with higher affinity than CXCR4 and is associated with the metastasis of colorectal cancer (CRC). Cancer-associated fibroblasts (CAFs) have been known to promote tumor progression. However, whether CAFs are involved in CXCR7-mediated metastasis of CRC remains elusive. We found a significant positive correlation between CXCR7 expression and CAF activation markers in colonic tissues from clinical specimens and in villin-CXCR7 transgenic mice. RNA sequencing revealed a coordinated increase in the levels of miR-146a-5p and miR-155-5p in CXCR7-overexpressing CRC cells and their exosomes. Importantly, these CRC cell-derived miR-146a-5p and miR-155-5p could be uptaken by CAFs via exosomes and promote the activation of CAFs through JAK2–STAT3/NF-κB signaling by targeting suppressor of cytokine signaling 1 (SOCS1) and zinc finger and BTB domain containing 2 (ZBTB2). Reciprocally, activated CAFs further potently enhanced the invasive capacity of CRC cells. Mechanistically, CAFs transfected with miR-146a-5p and miR-155-5p exhibited a robust increase in the levels of inflammatory cytokines interleukin-6, tumor necrosis factor-α, transforming growth factor-β, and CXCL12, which trigger the epithelial–mesenchymal transition and pro-metastatic switch of CRC cells. More importantly, the activation of CAFs by miR-146a-5p and miR-155-5p facilitated tumor formation and lung metastasis of CRC in vivo using tumor xenograft models. Our work provides novel insights into CXCR7-mediated CRC metastasis from tumor–stroma interaction and serum exosomal miR-146a-5p and miR-155-5p could serve as potential biomarkers and therapeutic targets for inhibiting CRC metastasis.

The role of epigenetic modifications in Colorectal Cancer Metastasis

Distant metastasis is the major contributor to the high mortality rate of colorectal cancer (CRC). To overcome the poor prognosis caused by distant metastasis, the mechanisms of CRC metastasis should be further explored. Epigenetic events are the main mediators of gene regulation and further affect tumor progression. Recent studies have found that some epigenetic enzymes are often dysregulated or mutated in multiple tumor types, which prompted us to study the roles of these enzymes in CRC metastasis. In this review, we summarized the alteration of enzymes related to various modifications, including histone modification, nonhistone modification, DNA methylation, and RNA methylation, and their epigenetic mechanisms during the progression of CRC metastasis. Existing data suggest that targeting epigenetic enzymes is a promising strategy for the treatment of CRC metastasis.

Exosomes Regulate the Epithelial-Mesenchymal Transition in Cancer

Exosomes are important mediators of intercellular communication and participate in complex biological processes by transferring a variety of bioactive molecules between cells. Epithelial–mesenchymal transition (EMT) is a process in which the cell phenotype changes from epithelioid to mesenchymal-like. EMT is also an important process for cancer cells by which they acquire invasive and metastatic capabilities, which aggravates the degree of tumor malignancy. Numerous studies have demonstrated that exosomes encapsulate various components, such as microRNAs and proteins, and transfer information between tumor cells or between tumor cells and the tumor microenvironment, thereby regulating the EMT process. Exosomes can also be used for cancer diagnosis and treatment or as a drug delivery platform. Thus, they can be used as a therapeutic tool to control the occurrence of EMT and affect cancer progression. In this review, we summarize the latest research advancements in the regulation of the EMT process in tumor cells by the contents of exosomes. Furthermore, we discuss the potential and challenges of using exosomes as a tool for cancer treatment.

Colorectal liver metastasis: molecular mechanism and interventional therapy

Colorectal cancer (CRC) is one of the most frequently occurring malignancy tumors with a high morbidity additionally, CRC patients may develop liver metastasis, which is the major cause of death. Despite significant advances in diagnostic and therapeutic techniques, the survival rate of colorectal liver metastasis (CRLM) patients remains very low. CRLM, as a complex cascade reaction process involving multiple factors and procedures, has complex and diverse molecular mechanisms. In this review, we summarize the mechanisms/pathophysiology, diagnosis, treatment of CRLM. We also focus on an overview of the recent advances in understanding the molecular basis of CRLM with a special emphasis on tumor microenvironment and promise of newer targeted therapies for CRLM, further improving the prognosis of CRLM patients.

MiR-130b-3p promotes colorectal cancer progression by targeting CHD9

Colorectal cancer (CRC) is the third most common cancer worldwide. Previous research revealed that microRNA 130b-3p (miR-130b-3p) significantly upregulated in CRC patients can be detected in feces from patients with such a neoplasm. In this study, the biological role and molecular mechanism of miR-130b-3p in CRC were explored. The miR-130b-3p level in CRC tissues, feces and cell lines was measured using RT-qPCR analysis. CCK-8, EdU, TUNEL, flow cytometry, Western blotting, and in vivo experiments were performed to explore the biological function of miR-130b-3p in CRC progression. For this purpose, 16 BALB/c nude mice were assigned to two groups. The experiment lasted for four months. Bioinformatics analysis and luciferase reporter assay were used to investigate the regulatory mechanism related to miR-130b-3p. In our research, miR-130b-3p was upregulated in CRC tissues and cells and it was detected in feces from CRC patients. Moreover, miR-130b-3p inhibition suppressed CRC cell proliferation and promoted cell apoptosis in vitro as well as repressed CRC tumor growth in vivo. Mechanistically, miR-130b-3p directly targeted the 3'untranslated region (UTR) of chromodomain helicase DNA binding protein 9 (CHD9) and negatively regulated CHD9 expression. Furthermore, CHD9 played an anti-oncogenic role in CRC. Inhibition of CHD9 expression was likely to be a key mechanism by which miR-130b-3p increased CRC cell growth, with a target protector experiment revealing miR-130b-3p influenced proliferation via direct inhibition of CHD9. MiR-130b-3p promotes the progression and tumorigenesis of CRC at least partially by targeting CHD9.Abbreviations: CRC: Colorectal cancer; miR-130b-3p: microRNA 130b-3p; CHD9: chromodomain helicase DNA binding protein 9; UTR: untranslated region; FIT: fecal immunochemical test; AAs: advanced adenomas.

Colorectal Cancer-Derived Small Extracellular Vesicles Promote Tumor Immune Evasion by Upregulating PD-L1 Expression in Tumor-Associated Macrophages

Tumor-associated macrophages (TAMs) are one of the most abundant cell types in colorectal cancer (CRC) tumor microenvironment (TME). Recent studies observed complicated "cross-talks" between cancer cells and macrophages in TME. However, the underlying mechanisms are still poorly elucidated. Here, PD-L1 levels are very low in CRC cells but highly abundant in TAMs, and a specific PD-L1+CD206+ macrophage subpopulation are identified, which is induced by tumor cells and associated with a poor prognosis. Mechanistic investigations reveal that CRC cells can secrete small extracellular vesicles (sEVs) taken up by macrophages that induce M2 like polarization and PD-L1 expression, resulting in increased PD-L1+CD206+ macrophage abundance and decreased T cell activity in CRC TME. sEV-derived miR-21-5p and miR-200a are identified as key signaling molecules mediating the regulatory effects of CRC on macrophages. Further studies reveal that CRC-derived miR-21-5p and miR-200a synergistically induces macrophage M2 like polarization and PD-L1 expression by regulating the PTEN/AKT and SCOS1/STAT1 pathways, resulting in decreased CD8+ T cell activity and increased tumor growth. This study suggests that inhibiting the secretion of specific sEV-miRNAs from CRC and targeting PD-L1 in TAMs may serve as novel methods for CRC treatment as well as a sensitization method for anti-PD-L1 therapy in CRC.

Exosomal RNAs: Novel Potential Biomarkers for Diseases-A Review

Exosomes are a subset of nano-sized extracellular vesicles originating from endosomes. Exosomes mediate cell-to-cell communication with their cargos, which includes mRNAs, miRNAs, lncRNAs, and circRNAs. Exosomal RNAs have cell specificity and reflect the conditions of their donor cells. Notably, their detection in biofluids can be used as a diagnostic marker for various diseases. Exosomal RNAs are ideal biomarkers because their surrounding membranes confer stability and they are detectable in almost all biofluids, which helps to reduce trauma and avoid invasive examinations. However, knowledge of exosomal biomarkers remains scarce. The present review summarizes the biogenesis, secretion, and uptake of exosomes, the current researches exploring exosomal mRNAs, miRNAs, lncRNAs, and circRNAs as potential biomarkers for the diagnosis of human diseases, as well as recent techniques of exosome isolation.

Stromal Cell-Derived Factor-1α (SDF-1α) Promotes Growth and Migration of Bone Marrow Stromal Cells (BMSCs) and Gastric Cancer Cells Through Phosphatidylinositol 3-Kinase/AKT (PI3K/Akt) Pathway

SDF-1α activity is closely related to information transmission and cell migration when contributing to lymphatic metastasis in various tumors. Herein, we explored the interaction among SDF-1α, CXCR4 and PI3K/Akt signaling pathway in gastric cancer (GC) and their roles in this disorder. Human GC cells KATO-III and BMSCs were co-cultured without contact. GC cells were transfected with SDF-1α, CXCR4 inhibitor, and PI3K inhibitor. After examining the efficiency of transfection, cell migration was evaluated using Transwell chamber, and expression SDF-1α, CD133, and CXCR4 was determined by RT-qPCR. With transfection rate of 98%, the number of migrated cells reduced upon inhibition of CXCR4 and PI3K. Luciferase activity in 565 nm are high than CXCR4 inhibition group. (p < 0.05). Likewise, up-regulation of SDF-1α increased the expression of SDF-1 (0.825±0.061), CD133 (0.875±0.058), CXCR4 (0.801±0.052), and Akt (0.852±0.062), compared to the blank group, CXCR4 inhibition group and PI3K inhibition group (p < 0.05). Down-regulation of CXCR4 and PI3K, however, decreased the expression insignificantly (p > 0.05). Collectively, up-regulation of SDF-1α activates CXCR4 signaling pathway of BMSCs and stimulates its downstream PI3K/Akt signaling pathway and and increases the expression of CD133, thereby promoting malignant behaviors of GC cells.

The Role of Small Extracellular Vesicles in the Progression of Colorectal Cancer and Its Clinical Applications

Colorectal cancer (CRC) is one of the most common cancers worldwide and a longstanding critical challenge for public health. Screening has been suggested to effectively reduce both the incidence and mortality of CRC. However, the drawback of the current screening modalities, both stool-based tests and colonoscopies, is limited screening adherence, which reduces the effectiveness of CRC screening. Blood tests are more acceptable than stool tests or colonoscopy as a first-line screening approach. Therefore, identifying blood biomarkers for detecting CRC and its precancerous neoplasms is urgently needed to fulfill the unmet clinical need. Currently, many kinds of blood contents, such as circulating tumor cells, circulating tumor nucleic acids, and extracellular vesicles, have been investigated as biomarkers for CRC detection. Among these, small extracellular vesicles (sEVs) have been demonstrated to detect CRC effectively in recent reports. sEVs enable intercellular shuttling-for instance, trafficking between recipient cancer cells and stromal cells-which can affect tumor initiation, proliferation, angiogenesis, immune regulation; metastasis, the cancer-specific molecules, such as proteins, microRNAs, long noncoding RNAs, and circular RNAs, loaded into cancer-derived sEVs may serve as biomarkers for the detection of cancers, including CRC. Indeed, accumulating evidence has shown that nucleic acids and proteins contained in CRC-derived sEVs are effective as blood biomarkers for CRC detection. However, investigations of the performance of sEVs for diagnosing CRC in clinical trials remains limited. Thus, the effectiveness of sEV biomarkers for diagnosing CRC needs further validation in clinical trials.

Estrogen receptor beta promotes lung cancer invasion via increasing CXCR4 expression

Lung cancer is one of the most lethal malignant tumors in the world. The high recurrence and mortality rate make it urgent for scientists and clinicians to find new targets for better treatment of lung cancer. Early studies indicated that estrogen receptor β (ERβ) might impact the progression of non-small-cell lung cancer (NSCLC). However, the detailed mechanisms, especially its linkage to the CXCR4-mediated cell invasion, remain unclear. Here we found that ERβ could promote NSCLC cell invasion via increasing the circular RNA (circRNA), circ-TMX4, expression via directly binding to the 5′ promoter region of its host gene TMX4. ERβ-promoted circ-TMX4 could then sponge and inhibit the micro RNA (miRNA, miR), miR-622, expression, which can then result in increasing the CXCR4 messenger RNA translation via a reduced miRNA binding to its 3′ untranslated region (3′UTR). The preclinical study using an in vivo mouse model with orthotopic xenografts of NSCLC cells confirmed the in vitro data, and the human NSCLC database analysis and tissue staining also confirmed the linkage of ERβ/miR-622/CXCR4 signaling to the NSCLC progression. Together, our findings suggest that ERβ can promote NSCLC cell invasion via altering the ERβ/circ-TMX4/miR-622/CXCR4 signaling, and targeting this newly circ-TMX4/miR-622/CXCR4 signaling may help us find new treatment strategies to better suppress NSCLC progression.