STAT3 Signaling Pathway Regulates Glioma Stem Cells Induced Host Macrophage Malignance

?Objective?Continuous activation of the STAT3 signaling pathway contributes to cellular proliferation,angiogenesis and activation of anti-apoptosis pathways to promote tumor progression.Besides,STAT3 activation plays an important role in the polarisation of M2 macrophages and immune suppression.Our previous study found that glioma stem cells(SU3)could induce host macrophage malignance in the immune microenvironment,and a cancerous cell line SU3-induced host celiac tumor cells(SU3-ihCTCs)was obtained.We also found STAT3 was activated in SU3-ihCTCs.This study was to investigate the role of STAT3 signaling pathway in regulating malignant transformation of macrophages induced by glioma stem cells.?Methods?The ratio of F4/80 positive cells in SU3-ihCTCs was tested by flow cytometry,and the macrophage markers were analyzed with reverse transcription-polymerase chain reaction(RT-PCR)or quantitative PCR(qPCR),respectively.SU3-ihCTCs were treated with 1~6 ?mol/L of STAT3 inhibitor WP1066for24 hours,then the expression of STAT3,p-STAT3,Bcl-2 and Cleaved caspase3 were detected with Western blotting,and the ratio of apoptosis were tested by flow cytometry.The macrophage cell line RAW264.7 was used as controls.BalB/C nude mice received subcutaneous implants of SU3-ihCTCs,the tumor size was measured every other day,and the final weight of tumor was measured.The expression of STAT3,p-STAT3,Bcl-2 and Cleaved caspase3 of the transplanted tumors were tested by Western blotting and immunohistochemical analysis.?Results?SU3-ihCTCs expressed higher of M2 macrophage makers,Arg-1,FIZZ1 and CD163,the ratio of F4/80 positive cells was 90.9%.STAT3 was activated in SU3-ihCTCs,and p-STAT3 expression was higher than that in normal peritonealmacrophages.When SU3-ihCTCs were treated with the STAT3 inhibitor WP1066,the expressions of M2 makers,p-STAT3 and apoptosis inhibitory protein Bcl-2 were down-regulated,the expression of apoptosis related protein Cleaved Caspase-3 was up-regulated.At the same time,the proliferation of SU3-ihCTCs was inhibited and apoptosis was enhanced.In vivo studies had shown that WP1066 treatment significantly decreased the volume and weight of SU3-ihCTCs xenografts in nude mice,and immunohistochemical and Western blotting analyses showed that the expression levels of p-STAT3 and Bcl-2 decreased and those of the apoptosis-related protein caspase-3 were increased.?Conclusions? We suggest that glioma stem cells induce host macrophage malignance in tumor microenvironment(TME),STAT3 pathway play an important role in the transformation process.These results present new evidence that macrophages in TME promote tumor proliferation.STAT3 signaling pathway may present a therapeutic target to suppress the tumor development.