[Valproate up-regulates the expression of NKG2DL through the MEK/ERK signaling pathway to enhance the killing effect of NK cells on A375 human melanoma cells].

ABSTRACT

Objective To investigate the effect of sodium valproate (VPA) on the expression of NKG2D ligand and the killing effect of NK cells on melanoma cells through MEK/ERK signaling pathway. Methods In the group with A375 cells in logarithmic phase treated with 1 mmol/L of VPA for 24 hours, the protein expression levels of MICA, MICB, phosphorylated MEK (p-MEK), MEK, phosphorylated ERK1/2 (p-ERK1/2), and ERK1/2 were detected by Western blotting, the expressions of MICA and MICB were detected by flow cytometry, and the killing effect of NK92 cells on A375 cells was detected by lactate dehydrogenase (LDH) release assay. In the group with A375 cells treated with the MEK/ERK signaling pathway inhibitor PD98059 combined with VPA, the protein expressions of MICA and MICB were detected by Western blotting, the expressions of MICA and MICB were detected by flow cytometry, and the killing effect of NK92 cells on A375 cells was detected by LDH release assay. The changes of melanoma volume in non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice were detected by tumor formation assay, and the expression of MICA and MICB was detected by immunohistochemical staining. Results Compared with those in the control group, the expressions of MICA and MICB of A375 cells, the killing effect of NK92 cells on A375 cells, and the ratios of p-MEK/MEK and p-ERK1/2/ERK1/2 were increased in the VPA group. Compared with those in the VPA group, the expressions of MICA and MICB of A375 cells and the killing effect of NK92 cells on A375 cells were decreased in the group of VPA combined with PD98059. Compared with those in the group of NK92 cells, the tumor volume of NOD/SCID mice was reduced, and the expressions of MICA and MICB were increased in the group of NK92 cells with VPA. Compared with those in the group of NK92 cells with VPA, the tumor volume of NOD/SCID mice was increased, and the expressions of MICA and MICB were decreased in the group of NK92 cells with VPA and PD98059. Conclusion VPA up-regulates the expression of MICA and MICB in melanoma cells and enhances the killing effect of NK92 cells on melanoma, which may be related to the activation of MEK/ERK signaling pathway.