MicroRNAs are short non-coding RNAs expressed in various tissues and cell types that suppress theexpression of target genes. MicroRNAs involved in cancer are called oncomiRs. Inhibition ofoncomiRs using antisense oligomers (that is, antimiRs) is an evolving therapeutic strategy. However,the in vivo efficacy of current antimiR technologies is hindered by physiological and cellular barriersfor delivery into targeted cells.A novel antimiR delivery platform that specifically targets tumour microenvironment makes use ofsynthetic molecules called peptide nucleic acid (PNA) antimiRs attached to a peptide called pHLIP.PNA antimiRs are antimiRs whose nucleotides are connected by peptide bonds instead of the normalphosphodiester bonds. The structure of pHLIP is pH dependent. At low pH, a transmembrane structureis induced in pHLIP that facilitates transport of attached PNA into tumour cells (Fig. 1). pHLIPmediated transport of antimiR-155 effectively inhibited the miR-155 oncomiR in cultured cells(Fig. 2).