Dynamic Change of Polarity in Primary Cultured Spheroids of Human Colorectal Adenocarcinoma and Its Role in Metastasis

Intestinal epithelial cells possess apical-basal polarity, which governs the exchange of nutrients and waste. Perturbation of cell polarity appears to be a general feature of cancers, although most colorectal cancers are differentiated adenocarcinomas, in which polarity is maintained to some extent. Little is known about the role of dysregulated polarity in cancer. The cancer tissue–originated spheroid method was applied to the preparation and culture of spheroids. Spheroids were cultured in suspension or in type I collagen gel. Polarity was assessed by IHC of apical markers and electron microscopy. Two types of polarity status in spheroids were observed: apical-in, with apical membrane located at cavities inside the spheroids in type I collagen gel; and apical-out, with apical membrane located at the outermost layer of spheroids in suspension. These polarities were highly interchangeable. Inhibitors of Src and dynamin attenuated the polarity switch. In patients, clusters of cancer cells that invaded vessels had both apical-in and apical-out morphologic features, whereas primary and metastatic tumors had apical-in features. In a mouse liver metastasis model, apical-out spheroids injected into the portal vein became apical-in spheroids in the liver within a few days. Inhibitors of Src and dynamin significantly decreased liver metastasis. Polarity switching was observed in spheroids and human cancer. The polarity switch was critical in an experimental liver metastasis model.