This allows for endosome-independent, direct cytosolic siRNA delivery, significantly enhancing siRNA transfection and reducing in vitro and in vivo target protein expression in SR-BI+ cancer cells relative to free siRNA and on par with liposomal-siRNA complexes, which are the current clinical gold standards for mediating siRNA delivery in vivo (Yang et al., 2011b; Lin et al., 2012; Ding et al., 2014; Tripathy et al., 2014; Zuckerman and Davis, 2015). Here, SCARB1 is linked to cancer.