Apg-2 depletion inhibits the formation of regular cysts in 3-D cultures. Control and Apg-2 RNAi cell lines were cultured without or with tetracycline in collagen/matrigel gels. The cells were regularly inspected by phase contrast microscopy to monitor cyst and lumen formation. The shown images were taken 7 days after the cultures had been started. Note, most cysts formed by Apg-2 depleted cells had an irregular shape and lacked a lumen.