Interleukin-34 promotes the proliferation and epithelial-mesenchymal transition of gastric cancer cells

BACKGROUND Interleukin(IL)-34 is a pro-inflammatory cytokine involved in tumor development.The role of IL-34 in the proliferation and epithelial-mesenchymal transition(EMT)of gastric cancer(GC)remains to be investigated.AIM To investigate whether and how IL-34 affects the proliferation of GC cells and EMT.METHODS Using immunohistochemical staining,the expression of IL-34 protein was detected in 60 paired GC and normal paracancerous tissues and the relationship between IL-34 and clinicopathological factors was analyzed.The expression of IL-34 mRNA and protein in normal gastric epithelial cell lines and GC was detected using quantitative real-time polymerase chain reaction(qRT-PCR)and western blotting,respectively.Stable IL-34 knockdown and overexpression in AGS cell lines were established by lentiviral infection and validated by qRT-PCR and western blotting.The cholecystokinin-8 assay,clone formation assay,cell scratch assay,and transwell system were used to detect GC cell proliferation,clone formation,migration,and invasion capacity,respectively.The effects of IL-34 on the growth of GC transplant tumors were assessed using a subcutaneous transplant tumor assay in nude mice.The effects of IL-34 on the expression level of EMT-associated proteins in AGS cells were examined by western blotting.RESULTS Expression of IL-34 protein and mRNA was higher in GC cell lines than in GES-1 cells.Compared to matched normal paraneoplastic tissues,the expression of IL-34 protein was higher in 60 GC tissues,which was correlated with tumor size,T-stage,N-stage,tumor,node and metastasis stage,and degree of differentiation.Knockdown of IL-34 expression inhibited the proliferation,clone formation,migration,and invasion of AGS cells,while overexpression of IL-34 promoted cell proliferation,clone formation,migration,and invasion.Furthermore,the reduction of IL-34 promoted the expression of E-cadherin in AGS cells but inhibited the expression of vimentin and N-cadherin.Overexpression of IL-34 inhibited E-cadherin expression but promoted expression of vimentin and N-cadherin in AGS cells.Overexpression of IL-34 promoted the growth of subcutaneous transplanted tumors in nude mice.CONCLUSION IL-34 expression is increased in GC tissues and cell lines compared to normal gastric tissues or cell lines.In GC cells,IL-34 promoted proliferation,clone formation,migration,and invasion by regulating EMT-related protein expression cells.Interference with IL-34 may represent a novel strategy for diagnosis and targeted therapy of GC.