Cancer-associated fibroblast-derived exosome Leptin promotes malignant biological lineage in pancreatic ductal adenocarcinoma by regulating ABL2 via miR-224-3p.

[BACKGROUND] Cancer-associated fibroblasts, as a major component of the tumor microenvironment, have been shown to exhibit protumorigenic effects in pancreatic ductal adenocarcinoma. Moreover, cancer-associated fibroblasts-derived exosomes have been reported to promote tumor development, but exact mechanisms have not been elucidated. The purpose of this study was to investigate the processes by which exosomes generated from cancer-associated fibroblasts promote tumor growth.

[METHODS] twenty-one patients with pancreatic ductal adenocarcinoma who evaluated preoperatively as potentially surgically resectable without distant metastasis and pathologically examined postoperatively as pancreatic ductal cell carcinoma were included. We determined the expression of Leptin as well as downstream proteins at the clinical and cellular levels. Cancer-associated fibroblast-derived exosomes were characterised by nanoparticle transmission electron microscopy and tracking analysis. To ascertain the mechanism mediating the action of exosomal Leptin in pancreatic ductal adenocarcinoma, we performed CCK-8 assay, colony formation assays, transwell and wound healing assays in PSN1 cells to evaluate cell proliferation, migration and invasion. Western blotting was used to detect the level of Leptin, ABL2 and exosome markers. qRT-PCR was employed to evaluate miR-224-3p. Cancer-associated fibroblasts markers and exosome uptake were verified by immunofluorescence.

[RESULTS] Western blotting assays show that Leptin is present inside tissues and cancer-associated fibroblasts in pancreatic ductal adenocarcinoma. Cancer-associated fibroblasts stimulated PSN1 cells growth, migration and invasion in vitro by secreting the exosomal Leptin. Exosomal Leptin could regulate miR-224-3p, which targets negative regulation of ABL2. Inhibiting Leptin significantly limited PSN1 cells growth, migration and invasion. In vitro analyses revealed that miR-224-3p mimics mitigate the inhibitory effect of cancer-associated fibroblasts knockdown of Leptin on PSN1 cells development, but overexpression of ABL2 partly abolished the tumor-promoting phenotype of miR-224-3p mimics.

[CONCLUSION] Our results revealed that cancer-associated fibroblasts mediate pancreatic ductal adenocarcinoma development by regulating the miR-224-3p/ABL2 molecular axis through the secretion of the exosomal Leptin.