Provided herein are peptides comprising an amino acid sequence having at least about 85% sequence identity to RYRPRAPIIAVT (SEQ ID NO: 1). These cationic peptides inhibit PKM2 methylation and may be used in the treatment of breast cancer and other diseases or conditions in which PKM2 is overexpressed. Such PKM2 peptides may be delivered to cancer cells using pH sensitive unimolecular nanoparticles comprising anionic polymers.