Background: The tumor microenvironment (TME) is a dynamic system orchestrated by intricate cell-to-cell crosstalk. Specifically, macrophages within the TME play a crucial role in driving tumor progression. Exosomes are key mediators of communication between tumor cells and the TME. However, the mechanisms underlying exosome-driven crosstalk between tumor cells and macrophages during colorectal cancer (CRC) progression remain incompletely elucidated. Methods: Single-cell RNA sequencing were analyzed using the Seurat package. Exosomes were isolated using ultracentrifugation and characterized by transmission electron microscopy, nanoparticle tracking analysis, and western blot. miRNAs differentially expressed in exosomes were analyzed using the limma package. CD206 expression in CRC tissues, exosomes tracing, and exosomal miR-106a-5p transport were observed through immunofluorescence. Macrophage polarization was assessed via qRT-PCR, ELISA, and flow cytometry. The interactions between miR-106a-5p, hnRNPA1, and SOCS6 were evaluated using miRNA pull-down, RIP, and dual-luciferase reporter assays. Transwell assays and liver metastasis model explored the role of exosomal miR-106a-5p-induced M2 macrophages in promoting CRC liver metastasis. Result: The proportion of M2 macrophages is increased in CRC with liver metastasis compared to those without. Highly metastatic CRC cells release exosomes enriched with miR-106a-5p, which promote macrophages M2 polarization by suppressing SOCS6 and activating JAK2/STAT3 pathway. These M2 macrophages reciprocally enhance CRC liver metastasis. hnRNPA1 regulate the transport of miR-106a-5p into exosomes. Clinically, elevated miR-106a-5p in plasma exosomes correlated with liver metastasis and poor prognosis. Conclusion: CRC-derived exosomal miR-106a-5p plays a critical role in promoting liver metastasis and is a potential biomarker for the prevention and treatment of CRC liver metastasis.

Liver metastasis is the main cause of death in colorectal cancer (CRC). Pre-metastatic niche (PMN), a favorable microenvironment for cancer cells colonization at distant organ, plays a pivotal role...

Background: Metastasis is the main cause for gastric cancer (GC)-related deaths. Better understanding of GC metastatic mechanism would provide novel diagnostic markers and therapeutic targets. Though it has been reported that mammalian sterile-20-like kinase 4 (MST4) exerts the oncogenic role in other tumors, the prognostic value and biological role of MST4 in GC are still unknown. Methods: The expression level of MST4 in GC was analyzed by using TCGA database. Then, Western blot and polymerase chain reaction (PCR) were used to determine the MST4 expression in GC tissues and cell lines. Immunohistochemistry was performed to investigate the expression of proteins in human GC tissues, and its correlation with clinicopathologic parameters as well as the prognosis for patients with GC was analyzed. In addition, the biological function and its molecular mechanism of MST4 in GC were investigated by in vitro and in vivo assays. Results: It demonstrated that MST4 expression was significantly upregulated in GC tissues and cell lines. High expression of MST4 was correlated with aggressive clinicopathological parameters such as lymph node metastasis, lymphovascular invasion (all P < 0.05). GC patients with high MST4 expression had both shorter overall survival (OS) and disease-free survival (DFS) than those with low MST4 expression (all P < 0.05). MST4 expression was an independent and significant risk factor for OS and DFS of GC patients (all P < 0.05). Results of functional experiments showed that MST4 could promote GC cells migration, invasion in vitro and metastasis in vivo. In terms of mechanism, MST4 promoted metastasis by facilitating epithelial–mesenchymal transition (EMT) through activating Ezrin pathway in GC. Further studies indicate that down-regulated miR-124-3p expression contributes to upregulated MST4 expression in GC. Conclusion: Our data showed that MST4 predicts poor prognosis and promotes metastasis by facilitating epithelial–mesenchymal transition in GC. Therefore, our study suggests that MST4 can be used as a valuable prognostic biomarker and a potential therapeutic target in GC.

Background: The tumour microenvironment consists of a complex and dynamic milieu of cancer cells, including tumour-associated stromal cells (leukocytes, fibroblasts, vascular cells, etc.) and their extracellular products. During invasion and metastasis, cancer cells actively remodel the tumour microenvironment and alterations of microenvironment, particularly cancer-associated fibroblasts (CAFs), can promote tumour progression. However, the underlying mechanisms of the CAF formation and their metastasis-promoting functions remain unclear. Methods: Primary liver fibroblasts and CAFs were isolated and characterized. CAFs in clinical samples were identified by immunohistochemical staining and the clinical significance of CAFs was also analysed in two independent cohorts. A transwell coculture system was used to confirm the role of HCC cells in CAF recruitment and activation. qRT-PCR, western blotting and ELISA were used to screen paracrine cytokines. The role and mechanism of Egfl7 in CAFs were explored via an in vitro coculture system and an in vivo mouse orthotopic transplantation model. Results: We showed that CAFs in hepatocellular carcinoma (HCC) are characterized by the expression of α-SMA and that HCC cells can recruit liver fibroblasts (LFs) and activate them to promote their transformation into CAFs. High α-SMA expression, indicating high CAF infiltration, was correlated with malignant characteristics. It was also an independent risk factor for HCC survival and could predict a poor prognosis in HCC patients. Then, we demonstrated that EGF-like domain multiple 7 (Egfl7) was preferentially secreted by HCC cells, and exhibited high potential to recruit and activate LFs into the CAF phenotype. The ability of Egfl7 to modulate LFs relies upon increased phosphorylation of FAK and AKT via the receptor α_νβ₃ integrin. Strikingly, CAFs activated by paracrine Egfl7 could further remodel the tumour microenvironment by depositing fibrils and collagen and in turn facilitate HCC cell proliferation, invasion and metastasis. Conclusion: Our data highlighted a novel role of Egfl7 in remodelling the tumour microenvironment: it recruits LFs and activates them to promote their transformation into CAFs via the α_νβ₃ integrin signaling pathway, which further promotes HCC progression and contributes to poor clinical outcomes in HCC patients.

Metastasis is the leading cause of mortality for colorectal cancer (CRC). Cancer-derived exosomes are widely recognized as the primary catalysts behind the development of pre-metastasis niche (PMN) in distal sites. However, the exact mechanism behind this process in CRC remains elusive. This study aimed to investigate the function and mechanisms underlying the role of exosomal miR-188-3p in activating hepatic stellate cells (HSCs) to develop the PMN and promote liver metastasis. We extracted exosomes from CRC cells using ultracentrifugation. Exosomes were identified using transmission electron microscopy, nanoparticle tracking analysis, and Western blot. Exosome uptake was assessed using fluorescence tracing, exosome PKH67 staining, and real-time quantitative PCR. The effects of CRC cell-derived exosomes on HSCs migration were evaluated using Transwell migration and wound healing assays. Key differentially expressed miRNAs were screened from the GEO database, and bioinformatics prediction along with dual-luciferase reporter assays were used to identify downstream target genes of miR-188-3p. Downstream related proteins of the target genes were detected by Western blot. In vivo, the distribution of exosomes and activation of HSCs in the liver were explored by tail vein injection of exosomes into nude mice. Further, the impact of exosomal miR-188-3p on liver metastasis was investigated using a spleen injection liver metastasis model. Finally, the expression levels of miR-188-3p in exosomes from CRC patient plasma were determined by real-time quantitative PCR, and the relationship between the expression of miR-188-3p in plasma exosomes and CRC prognosis was analyzed. The expression level of miR-188-3p within plasma exosomes demonstrated a statistically significant increase in CRC with liver metastasis compared to those without liver metastases. We also demonstrated the transferability of miR-188-3p from CRC cells to HSCs cells via the exosomes. Exosomal miR-188-3p plays a pivotal role in orchestrating the establishment of PMN through targeting PHLPP2 to activate HSCs before tumor metastasis. Exosomal miR-188-3p was found to actively foster in vivo metastasis of CRC. Additionally, plasma exosomal miR-188-3p potentially serves as a viable blood-based biomarker for CRLM. Exosomal miR-188-3p derived from CRC cells can promote liver metastasis by activating HSCs to form a PMN through targeting PHLPP2 to activate the AKT/mTOR pathway. These results offer a new perspective on the mechanisms driving CRLM.

MiR-144-3p is aberrantly expressed in several types of human cancer and functions as a tumor suppressor by inhibiting metastasis. However, the clinical significance and biological function of miR-144-3p in colorectal adenocarcinoma (CRA) have yet to be elucidated. Here we reported that miR-144-3p expression level was significantly down-regulated in CRA tissues compared with matched noncancerous colorectal mucosae tissues. Low miR-144-3p expression was correlated with adverse clinicopathologic characteristics and poor prognosis of CRA patients. Cox regression analysis showed that low miR-144-3p expression was an independent risk factor for DFS and OS in CRA. In vitro and in vivo assays showed that miR-144-3p significantly inhibited proliferation, migration and invasion of CRA cells. In particular, miR-144-3p could suppress EMT process of CRA cells by regulating the cytoskeleton and EMT markers. Bioinformatics analysis indicated that EMT associated transcription factors ZEB1 and ZEB2 were potential targets of miR-144-3p, and miR-144-3p inhibited ZEB1 and ZEB2 expression and was negatively correlated with their expression in CRA. Finally, we confirmed that ZEB1 and ZEB2 down-regulation collaboratively mediated the inhibitory effect of miR-144-3p on proliferation, invasion and EMT of CRA cells. In conclusion, our study provided evidence that miR-144-3p could inhibit CRA cell proliferation, invasion and EMT by targeting ZEB1/2.