Abstract
Primary mammary tumor organoids grown in 3D are an excellent system to study tumor biology. They resemble the organization and physiology of native epithelia more closely than cancer cell lines grown in 2D, and additionally model interactions with the ECM (Boj et al., 2015; Clevers, 2016; Shamir and Ewald, 2014). Mammary tumor organoids are therefore a promising model system to identify and characterize novel drivers of breast cancer that would be unlikely to be identified using 2D cell lines. Antisense oligonucleotides can be used to efficiently and specifically knockdown target genes in the cell (Bennett et al., 2017). They can be taken up freely by organoids without the need for a transfection agent, making them a convenient tool for routine lab studies and screens.