ISG15 and adenocarcinoma: Consistent with RIG-I induction, cationic-lipid-mediated transfection of HCV 5′-triphosphate RNA (referred to here as “5′-ppp-RNA”) into the A549 adenocarcinoma human lung epithelial cell line resulted in the induction of both IFNB1 cytokine and ISG15 mRNA transcripts (Fig. 1B).