To experimentally determine if AVL9, DENND5A and NUPL1 function in epithelial cell polarity and to better understand how they restrict cancer cell proliferation, we set out to knock down each gene in MDCKII (Madin-Darby canine kidney II) cells, a well-established cell line model for studying cell polarity and epithelial morphogenesis [18-20], and to examine the effects of the gene knockdown on the MDCKII cystogenesis via three dimensional (3D) culture [21]. The gene discussed is AVL9; the disease is cancer.