Therapeutic potential of a novel RMR peptide targeting the PAK1and RUNX3 interaction in human oral cancer models

Abstract

P21 Activated Kinase 1 is an oncogenic serine threonine kinase known to play a significant role in the regulation of cytoskeleton and cell morphology Runt related transcription factor 3 was initially known for its tumour suppressor function but recent studies have reported the oncogenic role of RUNX3 in various cancers Previous findings from our laboratory provided evidence that RUNX3 is a physiological interacting substrate of PAK1 and threonine 209 phosphorylation of RUNX3 acts as a molecular switch in dictating the tissue specific dualistic functions of RUNX3 for the first time At the same time previous results from clinical samples showed that the tumor samples had high expression of pRUNX3 as compared to the adjacent normal tissues suggesting that Threonine 209 phosphorylation by PAK1 could be a potential therapeutic target and of great clinical relevance with implications of RUNX3 inactivation in cancer cells where RUNX3 is known to be oncogenic Based on these evidences and to explore the translational significance of these findings we designed a small peptide RMR from the protein sequence of RUNX3 flanking the Threonine 209 phosphorylation site and a control peptide AAA differing only in the interaction between PAK1 and peptide The selection of this specific peptide from multiple peptides was based on their binding energies hydrogen bonding, docking efficiency with the active site of PAK1 and their ability to displace PAK1 and RUNX3 interaction in our prediction models and it was also confirmed by in vitro kinase assay We also tested the efficacy of this peptide to block the RUNX3 Threonine 209 phosphorylation mediated tumorigenic functions in in vitro cell culture models patient derived explant models and in in vivo tumor xenograft models All these results efficiently proved the potential of this peptide to develop as an efficient molecule of therapeutic value against RUNX3 Threonine 209 phosphorylation dependent tumour phenotypes newline newline newline newline