Identification of Functional Fragments in gMYL6 and the Mechanism of Improving NK Cell-Mediated Cytotoxicity

In a previous study, the unrecognized role of gMYL6 in the up-regulation of human NK cells development and cytotoxicity was reported. Objective: To further elucidate the mechanism of action of small recombinant fragments of gMYL6 enhancing the NK cells activity. Methods: Mononuclear cells were isolated from umbilical cord blood (UCB) by density-gradient centrifugation and NK cells were propagated and cultured. The small peptides from the gMYL6, with the ability to enhance the cytotoxicity of NK cells were screened by CCK-8 method and one of the most powerful peptides was identified for the next study. Flow cytometry was used to assess the proliferation and apoptosis of K562 cells, as well as the cell cycle arrest. The apoptosis of target cells was observed by AO/EB fluorescence staining, and the degree of apoptosis was assessed by flow cytometry. Protein imprinting method was also used to explore the pathway of small peptides to enhance the NK cells' activity. On the other hand, Real-time Quantitative PCR Detecting System was used to verify the mechanism of K562 cells suppression. Results: Small D peptide significantly increased NK cells cytotoxicity and induced both cell cycle arrest at G2/M and apoptosis of K562 cells. Conclusion: Small D peptide could be a novel promising peptide for cancer immunotherapy since it was shown to promote the cytotoxicity of cord blood-derived NK cells.