Cancer-associated fibroblasts (CAFs)-derived extracellular vesicles (EVs) can mediate tumorigenesis. Long noncoding RNA (LncRNA) SNHG3 is implicated in colorectal cancer (CRC) progression. The current study sought to clarify the role of CAFs-EVs carrying SNHG3 in CRC cell proliferation. Firstly, CAFs and normal fibroblasts (NFs) were cultured and identified, followed by isolation and characterization of CAFs-EVs and NFs-EVs. CRC cells were cultured with CAFs-EVs or CAFs-EVs overexpressing SNHG3. The effects of SNHG3 on CRC cell proliferation was evaluated using CCK-8, colony formation, and EdU staining assays. The binding relationships among SNHG3, miR-34b-5p, and HuR were validated, in addition to analyzing the binding between HuR and HOXC6. Lastly, xenograft tumor model was established to verify the role of CAFs-EVs carrying SNHG3 in vivo. SNHG3 was highly expressed in CRC cells and CAFs-EVs, whereas CAFs-EVs facilitated CRC cell proliferation. Mechanically, CAFs-EVs carried SNHG3 into CRC cells to upregulate HuR expression by competitively binding to miR-34b-5p, promote the binding of HuR and HOXC6, and enhance HOXC6 transcription. miR-34b-5p over-expression or HOXC6 silencing annulled the effect of CAFs-EVs. SNHG3 carried by CAFs-EVs facilitated CRC proliferation via the miR-34b-5p/HuR/HOXC6 axis in vivo. Collectively, our findings indicated that CAFs-EVs carried SNHG3 into CRC cells to upregulate HuR expression by sponging miR-34b-5p and finally enhance HOXC6 transcription, thereby facilitating CRC cell proliferation.

Mesenchymal stem cell–derived extracellular vesicles (MSC-EV) can transport microRNAs (miRNAs) into colorectal cancer (CRC) cells, thus to inhibit the malignant phenotype of cancer cells. Whether MSC-EV could deliver miR-34a-5p to suppress CRC development was surveyed through the research. miR-34a-5p, c-MYC, DNA methyltransferase 3a (DNMT3a), and phosphatase and tensin homolog deleted on chromosome 10 (PTEN) expression were measured in CRC tissues and cell lines. miR-34a-5p and c-MYC expression were altered by transfection in HCT-116 cells. MSC-EV were transfected with miR-34a-5p- and c-MYC-related oligonucleotides and co-cultured with HCT-116 cells. HCT-116 cell growth after treatment was observed. Furthermore, the functional roles of miR-34a-5p and c-MYC were explored in vivo. The combined interactions of miR-34a-5p/c-MYC/DNMT3a/PTEN axis were assessed. miR-34a-5p and PTEN were downregulated while c-MYC and DNMT3a were upregulated in CRC. Depletion of miR-34a-5p drove while that of c-MYC restricted CRC cell growth. MSC-EV retarded CRC progression. Moreover, MSC-EV carrying overexpressed miR-34a-5p or depleted c-MYC further disrupted CRC cell progression. miR-34a-5p targeted c-MYC to regulate DNMT3a and PTEN. c-MYC overexpression abrogated EV-derived miR-34a-5p upregulation-induced effects on CRC. Restoring miR-34a-5p or depleting c-MYC in MSC-EV limited CRC tumor formation. MSC-EV-derived miR-34a-5p depresses CRC development through modulating the binding of c-MYC to DNMT3a and epigenetically regulating PTEN.