The Cancer Genome Atlas dataset comprising of 448 cases of lung adenocarcinoma, tissue microarray of 144 cases of lung adenocarcinoma, and pleural lavage fluid of 41 cases was used to examine miR-21 expression levels. The function of EV-miR-21 was investigated in vitro.
The miR-21 expression level in primary sites was associated with a poor prognosis and correlated with pleural invasion of adenocarcinoma. EV-miR-21 levels in pleural lavage fluid were associated with positive cytology and pleural invasion in the primary sites, even in cytology-negative cases. In vitro studies demonstrated that EV-miR-21 induces the MMT. Mesothelial cells in the MMT showed functions similar to cancer-associated fibroblasts, which are an important stromal component in primary sites and disseminated pleural lesions.
EV-miR-21 in pleural lavage fluid is important as a diagnostic and prognostic factor. Moreover, EV-miR-21 induces the MMT, which can form premetastatic niches of dissemination in the pleural cavity.
© 2020 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.