CDKN1B and breast cancer: The same R-pep-PNA-a221 tested in breast cancer cells produced the same effect in glioma cells, leading to the downregulation of the miR-221 oncogene target p27kip1 [154], while co-administration of R-pep-PNA-a221 and a R8-conjugated PNA anti-miR-155 promoted apoptosis and reverted the drug-resistance phenotype of glioma cells [155].