One of the most frequently asked questions about antisense oligonucleotides (ASOs) is, “How do ASOs enter cells?” In the past few years, my research group has provided ever more detailed answers to that question and have also set out to answer an equally important question: “Where do ASOs go once inside cells and how do they get there?” In a review published in Nature Biotechnology, we summarized the answers to these questions. Remarkably, since that review was published in 2017, the pace at which our understanding of these complex processes has actually increased. (see Wang, et. al. Molecular Therapeutic. 2018, in press; Wang, et. al., Nucleic Acid Res., 46: 3579-3594, 2018; Wang et. al., Nucleic Acid Res. 45: 5309-5322, 2017)
A conclusion that derives from our work, which sounds very simple but, in reality, is a fundamental observation, is this: the fate of phosphorothioate (PS) ASOs is defined by proteins. Cellular uptake and subcellular distribution are mediated by proteins that bind PS ASOs. We have identified most of the key proteins and characterized most of the effects of these proteins on ASO behaviors of proteins in and on the cell to which ASOs bind.