Development of Novel Peptides That Target the Ninjurin 1 and 2 Pathways to Inhibit Cell Growth and Survival via p53

Ninjurin 1 and 2 (NINJ1, NINJ2) belong to the homophilic cell adhesion family and play significant roles in cellular communication and tissue development. While both NINJ1 and NINJ2 are found to be over-expressed in several types of cancers, it remains unclear whether they can be targeted for cancer treatment. In this study, we aimed to develop NINJ1/2 peptides derived from the N-terminal extracellular domain that can elicit growth suppression and thus possess therapeutic potentials. We found that peptide NINJ1-A, which is derived from the N-terminal adhesion motif of NINJ1, was able to inhibit cell growth in a NINJ1- or p53-dependent manner. Similarly, peptide NINJ2-A, which is derived from the N-terminal adhesion motif of NINJ2, was able to inhibit cell growth in a NINJ2- or p53-dependent manner. We also found that NINJ1 and NINJ2 physically interact via their respective N-terminal domains. Interestingly, NINJ1-B and NINJ2-B peptides, which were derived from the N-terminal amphipathic helix domains of NINJ1 and NINJ2, respectively, were able to disrupt NINJ1-NINJ2 interaction and inhibit cell growth in a NINJ1/NINJ2-dependent manner. Notably, NINJ1-B and NINJ2-B peptides demonstrated greater potency in growth suppression than NINJ1-A and NINJ2-A peptides, respectively. Mechanistically, we found that NINJ1-B and NINJ2-B peptides were able to induce p53 expression and suppress cell growth in a p53-dependent manner. Together, our findings provide valuable insights into the development of NINJ1/NINJ2 peptides as potential cancer therapeutics, particularly for cancers harboring wild-type p53.