Novel spatiotemporal patterns of epithelial tumor invasion in Drosophila discs large egg chambers

Loss of Discslarge (Dlg) in early Drosophila egg chambers causes invasion of tumor follicle cells from the anterior epithelium, a pattern that resembles developmental border cell migration during mid-oogenesis. Here, we have analyzed novel spatial and temporal patterns of dlg invasion. Even though Dlg is ubiquitously expressed in all follicle cells, invasions are biased at the anterior and posterior termini. The patterns of invasion correlate with both a higher rate of follicle cell proliferation and with a greater frequency of loss of epithelial polarity at the termini compared with central regions of the egg chamber. Nonetheless, the average number of cells that invade per invasion event from terminal vs. central regions is approximately equal. Of interest, patterns of dlg invasion appear to coincide with boundaries established by proto-oncogene signals responsible for anterior-posterior patterning. The Drosophila egg chamber may thus be a useful model for exploring how epithelial tumor invasion might be a neomorphogenetic process organized by signals essential for developmental pattern formation.