Biomed Pharmacother. the let\7i and its downstream gene, that is KDM3A. The findings showed the presence of a high expression of KDM3A and DCLK1 and reduced expression of let\7i Didox and FXYD3 in lung cancer. KDM3A elevated DCLK1 by removing the methylation of H3K9me2. Moreover, DCLK1 suppressed the FXYD3 expression. BMSC\EV\derived let\7i resulted in the down\regulation of KDM3A expression and reversed its promoting role in lung cancer development. Consistently, in vivo experiments in nude mice also confirmed that tumour growth was suppressed by the BMSC\EV\derived let\7i. In conclusion, our findings demonstrated that the BMSC\EV\derived let\7i possesses an inhibitory Didox role in lung cancer progression through the KDM3A/DCLK1/FXYD3 axis, suggesting a new molecular target for lung cancer treatment. at 4C with the supernatant collected. Afterwards, positive control Sdc2 antibody RNA polymerization Enzyme II, negative control antibody Normal human IgG and KDM3A antibody (ab91252, Abcam), H3K9me2 antibody (ab1220, Abcam) were added, respectively, to immunoprecipitate DNA/protein complex. After immunoprecipitation, the DNA was washed, reverse\crosslinked, and protein was removed by proteinase K treatment. Eluted DNA was purified using the Active Motif’s ChIP DNA purification kit (Cat. No. 58?002, Millipore), and qPCR was conducted to verify the DCLK1 promoter expression. 2.17. Xenograft tumours in nude mice Twenty\four healthy Balb/c nude mice (Beijing Institute of Pharmacology, Chinese Academy of Medical Sciences, Beijing, China) aged 6\8?weeks were housed in a specific pathogen\free (SPF) animal laboratory in different cages with a humidity of 60%\65%, temperature 22C\25C and provided with free food and water under 12\hour light and dark cycle. The experiment was started one week after adaptive feeding, and the health status of nude mice was observed before the experiment. A xenograft model was founded with the subcutaneous injection of 1 1??106 A549 cells into the stomach of nude mice. After successful modelling, they were randomly and equally divided into 4 organizations, and treated in a different way as follows: PBS (500 L of PBS was injected tail vein every 2 d), EV\let\7i\mimic (EVs were extracted after transfection of let\7i\mimic into BMSC, suspended in sterile PBS and injected into mice from tail vein every 2 days at 500 L, 25?g/mL each time), si\FXYD3 (si\FXYD3 adenoviral vectors were injected into nude mice from tail vein every 2?days at 500 L, 25?g/mL each time) and si\FXYD3?+?EV\let\7i\mimic (EVs were extracted after transfection of let\7i\mimic into BMSC and EVs and si\FXYD3 adenoviral vectors) were combined and injected from tail vein every 2?days. The tumour volume of each mouse was measured having a vernier caliper. After A549 cell transplantation, the tumours were dissected and weighed, after which the mice were killed within the 30th day time following these procedures. Haematoxylin\eosin staining was used to detect lung metastasis on paraffin sections. 2.18. Statistical analysis The SPSS 21.0 statistical software (IBM Corp.) was utilized for statistical analysis. Data were indicated as the mean??standard derivation. Data of malignancy cells and paracancerous cells were compared using paired test, and data between the other two organizations were compared using an unpaired test. Assessment among multiple organizations was analysed by one\way analysis of variance (ANOVA). Assessment among organizations at different time\points was analysed from the two\way ANOVA. Tumour volume was analysed from the repeated\steps ANOVA value were selected, and Venn diagram was plotted to take the intersection with 13 miRNAs acquired (Number?1B). Databases RAID (Score?>?0.6) (http://www.rna\society.org/raid2/index.html), mirDIP (Integrated Score?>?0.8) (http://ophid.utoronto.ca/mirDIP/), DIANA TOOLS (miTG score?>?0.7) (http://diana.imis.athena\innovation.gr/DianaTools), miRDB (Target Score?>?85) (http://www.mirdb.org), starBase (clipExpNum?>?10, pancancerNum?>?5) and miRWalk (energy Didox < ?20, convenience??0.1) (http://mirwalk.umm.uni\heidelberg.de) were employed to predict the downstream genes of let\7i and Venn.