Roles of cancer-associated fibroblast functional heterogeneity in shaping the lymphatic metastatic landscape:new insights and therapeutic strategies

Lymph node (LN) metastasis is a process in which cancer cells travel from primary tumors to LNs via the lymphatic system,then proliferate and spread within the LNs. In most cancers,LN metastasis is a major mode of cancer dissemination,and a critical indicator of cancer progression and worsening prognosis1. The occurrence of LN metastasis indicates that the tumor has invaded the lymphatic system.

Extracellular vesicle-mediated heterogeneous communication between cancer and the lymphatic system facilitates lymphatic metastasis

Introduction The dissemination of cancer cells to organs initiates the formation of an aggressive cancer phenotype and is a predominant cause of cancer-associated death.For most epithelial cancers,lymphatic system metastasis has been characterized as the most common and earliest metastatic pathway,and the detection of metastasis in lymph nodes(LNs)often predicts poor survival among patients'.Although increasing attention is being paid to the clinical importance of LN metastasis,the underlying mechanisms have remained unclear in the past decade.Accumulating evidence suggests that the occurrence of LN metastasis is not stochastic but is a programming biological event regulated by the bidirectional crosstalk between metastasis-initiating cancer cells and the tumor microenvironment(TME)2.However,the regulators and patterns of cancer-TME communication in LN metastasis remain to be furtherexplored.

An HGF-dependent positive feedback loop between bladder cancer cells and fibroblasts mediates lymphangiogenesis and lymphatic metastasis

Background Cancer-associated fibroblasts (CAFs) play a vital role in facilitating tumor progression through extensive reciprocal interplay with cancer cells. Tumor-derived extracellular vesicles (EVs) are the critical mediators involved in the crosstalk between cancer cells and stromal cells, contributing to the metastasis of cancers. Yet, the biological mechanisms of tumor-derived EVs in triggering CAFs phenotype to stimulate the lymph node (LN) metastasis of bladder cancer (BCa) are largely unknown. Here, we aimed to explore the effects and molecular mechanisms of tumor-derived EV-mediated CAFs phenotype in regulating BCa LN metastasis. Methods The high-throughput sequencing was utilized to identify the crucial long non-coding RNA (lncRNA) associated with CAF enrichment in BCa. The functional role of the transition of fibroblasts to CAFs induced by LINC00665-mediated EVs was investigated through the in vitro and in vivo assays. Chromatin isolation by RNA purification assays, fluorescence resonance energy transfer assays, cytokine profiling and patient-derived xenograft (PDX) model were performed to explore the underlying mechanism of LINC00665 in the LN metastasis of BCa. Results We found that CAFs are widely enriched in the tumor microenvironment of BCa, which correlated with BCa lymphangiogenesis and LN metastasis. We then identified a CAF-associated long non-coding RNA, LINC00665, which acted as a crucial mediator of CAF infiltration in BCa. Clinically, LINC00665 was associated with LN metastasis and poor prognosis in patients with BCa. Mechanistically, LINC00665 transcriptionally upregulated RAB27B expression and induced H3K4me3 modification on the promoter of RAB27B through the recruitment of hnRNPL. Moreover, RAB27B-induced EVs secretion endowed fibroblasts with the CAF phenotype, which reciprocally induced LINC00665 overexpression to form a RAB27B-HGF-c-Myc positive feedback loop, enhancing the lymphangiogenesis and LN metastasis of BCa. Importantly, we demonstrated that blocking EV-transmitted LINC00665 or HGF broke this loop and impaired BCa lymphangiogenesis in a PDX model. Conclusion Our study uncovers a precise mechanism that LINC00665 sustains BCa LN metastasis by inducing a RAB27B-HGF-c-Myc positive feedback loop between BCa cells and fibroblasts, suggesting that LINC00665 could be a promising therapeutic target for patients with LN metastatic BCa.

SUMOylation-triggered ALIX activation modulates extracellular vesicles circTLCD4-RWDD3 to promote lymphatic metastasis of non-small cell lung cancer

Lymph node(LN)metastasis is one of the predominant metastatic routes of non-small cell lung cancer(NSCLC)and is considered as a leading cause for the unsatisfactory prognosis of patients.Although lymphangiogenesis is well-recognized as a crucial process in mediating LN metastasis,the regulatory mechanism involving lymphangiogenesis and LN metastasis in NSCLC remains unclear.In this study,we employed high-throughput sequencing to identify a novel circular RNA(circRNA),circTLCD4-RWDD3,which was significantly upregulated in extracellular vesicles(EVs)from LN metastatic NSCLC and was positively associated with deteriorated OS and DFS of patients with NSCLC from multicenter clinical cohort.Downregulating the expression of EV-packaged circTLCD4-RWDD3 inhibited lymphangiogenesis and LN metastasis of NSCLC both in vitro and in vivo.Mechanically,circTLCD4-RWDD3 physically interacted with hnRNPA2B1 and mediated the SUMO2 modification at K108 residue of hnRNPA2B1 by upregulating UBC9.Subsequently,circTLCD4-RWDD3-induced SUMOylated hnRNPA2B1 was recognized by the SUMO interaction motif(SIM)of ALIX and activated ALIX to recruit ESCRT-III,thereby facilitating the sorting of circTLCD4-RWDD3 into NSCLC cell-derived EVs.Moreover,EV-packaged circTLCD4-RWDD3 was internalized by lymphatic endothelial cells to activate the transcription of PROX1,resulting in the lymphangiogenesis and LN metastasis of NSCLC.Importantly,blocking EV-mediated transmission of circTLCD4-RWDD3 via mutating SIM in ALIX or K108 residue of hnRNPA2B1 inhibited the lymphangiogenesis and LN metastasis of NSCLC in vivo.Our findings reveal a precise mechanism underlying SUMOylated hnRNPA2B1-induced EV packaging of circTLCD4-RWDD3 in facilitating LN metastasis of NSCLC,suggesting that EV-packaged circTLCD4-RWDD3 could be a potential therapeutic target against LN metastatic NSCLC.