SPIB Acts As A Tumor Suppressor By Activating The NFκB And JNK Signaling Pathways Through MAP4K1 In Colorectal Cancer Cells

Background:Colorectal cancer(CRC)is one of the major cancers worldwide.Spi-B transcription factor(SPIB)is a member of the E-twenty-six(ETS)transcription factor family.Previous studies have shown that the expression of SPIB is downregulated in human colorectal cancer tissues.However,its biological function in colorectal cancer cells has not been reported.The purpose of our study was to explore the biological function and related mechanism of SPIB in colorectal cancer cells to provide a reference for the molecular detection and targeted drug therapy of colorectal cancer.Methods:The biological function of SPIB in colorectal cancer cells was studied by colony formation assay,CCK-8 cell proliferation assay,transwell assay,tube formation assay,and flow cytometry analysis.A growth inhibition assay was used to measure the impact of SPIB on oxaliplatin and 5-fluorouracil(5-FU).Dual-luciferase reporter assay and western blotting(WB)were used to detect the mechanism of SPIB in colorectal cancer cells.Results:SPIB mRNA was downregulated in CRC tissues,and was low expression in colorectal cancer cells.SPIB could inhibit the proliferation,migration and invasion of CRC cells;inhibit angiogenesis;and induce CRC cells cycle arrest in G2/M phase and promote the apoptosis of CRC cells.In a growth inhibition assay,we found that compared with the control group,the 50% inhibitory concentration(IC50)values of oxaliplatin and 5-FU in the SPIB overexpression group were significantly reduced.WB results showed that compared with the control group,the overexpression of SPIB upregulated cleaved-PARP(c-PARP),nuclear factor k B p65(NFκB p65),phospho-NFκB p65(p-NFκB p65),JNK1,and C-Jun protein expression levels,the silence of SPIB downregulated c-PARP,NFκB p65,p-NFκB p65,JNK1,and C-Jun protein expression levels.A dual-luciferase reporter assay showed that SPIB could activate the promoter of MAP4K1 and enhance the expression of MAP4K1.After silencing MAP4K1,the protein expression levels of c-PARP,NFκB p65,p-NFκB p65,JNK1,and C-Jun were downregulated.Conclusions:In this study,we found that SPIB is a tumor suppressor in colorectal cancer cells and that SPIB sensitizes colorectal cancer cells to oxaliplatin and 5-FU.We also found that MAP4K1 is a target gene of SPIB and that SPIB exerts its anti-colorectal cancer effect by activating the NFκB and JNK signaling pathways through MAP4K1.The above findings may provide a reference for new molecular markers and therapeutic targets for CRC.