Abstract: Objective The aim of this study was to investigate the mechanism of placental growth factor(PLGF)mediated crosstalk between non-small cell lung cancer(NSCLC)cells and tumor-associated macrophages(TAM). Methods A NSCLC model in mice was established by tail vein injecting NSCLC A549 cells into 10-weeks-old male NOD/SCID mice,which were transfected by adeno-associated virus(AAV).A flow cytometry was used to detect various macrophage(MΦ)subtypes.Levels of PLGF,vascular endothelial growth factor receptor-1(Flt-1) and transforming growth factor β1(TGF-β1)were examined in tumor cells and TAM by RT-qPCR.With the different cultured media of A549 cells and MΦ cells,it could divide into A549 group and MΦ group,A549+MΦ group,A549+MΦ+ sFlt-1 group(with 10 μg/L sFlt-1),PLGF+MΦ group(with 100 ng PLGF)and PLGF+MΦ+ sFlt-1 group(with 100 ng PLGF and 10 μg/L sFlt-1).Transwell assay and MTT assay were used to detect the proliferation and migration of A549 cells with different co-culture conditioned media.With the different cultured media of HUVEC cell,it could divide into control group,conditioned media(CM)group,CM+SB431542 group,TGF-β1 group and TGF-β1+SB431542 group.HUVEC cells collagen gel assay was used to detect the tumor vascularization. Results Compared with RFP- cells,PLGF was predominantly expressed by tumor cells(31.72±4.69 vs. 2.31±0.06,P＜0.001),while Flt-1 was predominantly expressed by CD163+macrophages(P＜0.001).The proliferation ability of A549 cells in the A549+MΦ group was significantly higher than in A549 group and A549+MΦ+sFlt-1 group(OD value:3.62±0.23 vs. 4.53±0.34 vs. 3.71±0.37,P＜0.05).TGF-β1 in TAM/M2 macrophages was higher than that in M1 macrophages(0.99±0.23 vs. 0.07±0.02,P＜0.05).The formation of tubular structures in HUVEC cells were the most in the CM group and TGF-β1 group(P＜0.05),which was inhibited by TGF-β1 inhibitor SB431542. Conclusion The crosstalk between TAM and NSCLC cells via PLGF/Flt-1 and TGF-β1 signal pathways promotes the growth and vascularization of NSCLC.

Key words: Non-small cell lung cancer(NSCLC), Placental growth factor(PLGF), Tumor-associated macrophages(TAM), Transforming growth factor β1(TGF-β1)