EpCAM+CD73+ mark epithelial progenitor cells in postnatal human lung and is associated with pathogenesis of pulmonary disease including lung adenocarcinoma.

Abstract

Lung injury in mice induces mobilization of discrete subsets of epithelial progenitor cells to promote new airway and alveolar structures. However, whether similar cell types exist in human lung remains unresolved. Using flow cytometry, we identified a distinct cluster of cells expressing epithelial cell adhesion molecule (EpCAM), a cell surface marker expressed on epithelial progenitor cells, enriched in the ecto-5'-nucleotidase CD73 in unaffected postnatal human lung resected from pediatric patients with congenital lung lesions. Within the EpCAM+CD73+ population, a small subset co-express integrin β4 and HTII-280. This population remained stable with age. Spatially, EpCAM+CD73+ cells were positioned along the basal membrane of respiratory epithelium and alveolus next to CD73+ cells lacking EpCAM. Expanded EpCAM+CD73+ cells give rise to pseudostratified epithelium in 2D air-liquid interface or a clonal 3D organoid assay. Organoids generated under alveolar differentiation conditions were cystic-like and lacked robust alveolar mature cell types. Compared with unaffected postnatal lung, congenital lung lesions were marked by clusters of EpCAM+CD73+ cells in airway and cystic distal lung structures lined by simple epithelium of composed of EpCAM+SCGB1A1+ cells and hyperplastic EpCAM+proSPC+ cells. In non-small cell lung cancer (NSCLC), there was a marked increase in EpCAM+CD73+ tumor cells enriched in inhibitory immune checkpoint molecules CD47 and programmed death-ligand 1 (PD-L1), which was associated with poor survival in lung adenocarcinoma. In conclusion, EpCAM+CD73+ cells are a rare novel epithelial progenitor cell in human lung. Importantly, re-emergence of CD73 in lung adenocarcinoma enriched in negative immune checkpoint molecules may serve as a novel therapeutic target.