RRM2 and cancer: Another approach of polyplexes was used for efficiently generating reactive oxygen species that helped in endosomal escape of siRNA that was later internalised by cancer cells in vitro and inhibited tumour growth in two xenograft murine models by reducing RRM2 (ribonucleotide reductase subunit M2) expression in cancer which consequently reduced cell proliferation and enhanced cancer cell apoptosis [161].