Endometrial cancer cell lines such as KLE are derived from glandular epithelium, and as such, can be induced in vitro to grow spheroids reminiscent of endometrial glands.32 These endometrial spheroids display basal/apical polarity when stained for F-actin, a marker of apical polarity based on phalloidin staining, and the apical tight junction protein ZO-1.33 Using this staining technique we found that spheroids generated from KLE cells after CTCF knockdown had a reduced proportion of spheroids showing apical/central F-actin and ZO-1 staining compared to control cells (Figures 4e and f). The gene discussed is CTCF; the disease is endometrial cancer.