Fig. 2: Histopathological characterization of PDOs.
A Bright field microscopy images of PDOs derived from gastric and esophageal cancers. All of the gastric cancer PDOs originated from poorly differentiated tumor tissues and showed less coherent (GC006 and GC011) and grape-like growth patterns (GC004, GC010, and GC015) without any lumen structures. All but one (EC018) of the esophageal PDOs originated from squamous cell carcinoma tissues and showed a round shape without any lumen structures. EC018 originated from esophageal adenocarcinoma tissue and showed a more irregular outline than PDOs derived from squamous carcinoma tissue. B Scanning (SEM) and transmission (TEM) electron microscope images of PDOs derived from gastric signet ring cell carcinoma (SRCGC) (GC006), esophageal squamous cell carcinoma (ESCC) (EC007) and esophageal adenocarcinoma (EAC) (EC018). GC006 showed less cohesive cell clusters by SEM and abundant mucous granules (yellow arrowheads) by TEM. Additionally, nuclei (N) are compressed by the granules toward the cell periphery in GC006. These features of GC006 are typical of SRCGC. EC007 showed a solid spherical shape by SEM and contained substantial numbers of cells without a lumen structure, consistent with the features of organoids derived from squamous carcinoma tissue7,9. Tight junctions were also observed between the cells (white arrows). EC018 showed an irregular surface by SEM and luminal structures lined by microvilli (white arrowheads) by TEM, which is a characteristic of adenocarcinoma. C Hematoxylin & eosin (HE), periodic acid-Schiff (PAS; a marker of mucin-producing cells) and immunohistochemistry with antibodies against AE1/AE3 (a marker of pan cytokeratin), TP63 (a marker of basal cells) and Ki67 (a proliferation marker). GC006 and EC018 showed positive PAS staining, suggesting that these PDOs produced mucin. All of the three organoids were positive for cytokeratin (AE1/AE3), indicating their epithelial origin. Almost all of the cells in EC007 were positive for TP63, thus characterizing them as squamous cells. All of the three organoids contained abundant MKI67-positive cells, suggesting their proliferative capacity. Bars in A and C are 50 and 20 µm, respectively.
