SPIB Acts as a Tumor Suppressor by Activating NFkB and JNK Signaling Pathways Through MAP4K1 in Colorectal Cancer Cells

Abstract BackgroundColorectal cancer (CRC) is one of the major cancers in the world. Spi-B Transcription Factor (SPIB) is one member of the E-twenty-six (ETS) transcription factor family. Previous studies have shown that the expression of SPIB is down-regulated in human colorectal cancer tissues. However, its biological function in colorectal cancer cells is not reported. The purpose of our study is to explore the biological function and related mechanism of SPIB in colorectal cancer cells, to provide reference for the molecular detection and targeted drug therapy of colorectal cancer.MethodsThe biological function of SPIB in colorectal cancer cells were studied by colony formation assay, CCK-8 cell proliferation assay, transwell assay, tube formation assay, flow cytometry analysis. Growth inhibition assay was used to measure the impact of SPIB on oxaliplatin and 5-fluorouracil (5-FU). Double luciferase reporter assay and western blot were used to detect mechanism of SPIB in colorectal cancer cells. ResultsSPIB mRNA was down-regulated in CRC cell lines and CRC tissues. SPIB can inhibit the proliferation, migration and invasion of CRC cells; can inhibit angiogenesis; and induce the cell cycle of CRC cells arrest in G2/M phase and promote the apoptosis of CRC cells. In the 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. Western blot results showed that the overexpression of SPIB up-regulated cleaved-PARP(c-PARP), nuclear factor kB p65 (NFkB p65), phospho-NFkB p65(p-NFkB P65), JNK1, and C-Jun proteins expression level compared with the control group. Double luciferase report experiment showed that SPIB can activate the promoter of MAP4K1 and enhance the expression of MAP4K1. After silencing MAP4K1, the protein expressions of c-PARP, NFkB P65, p-NFkB P65, JNK1, and C-Jun were down-regulated. ConclusionsIn this study, we found that SPIB is a tumor suppressor in colorectal cancer cells, SPIB sensitizes colorectal cancer cells to oxaliplatin and 5-FU. we also found that MAP4K1 is a target gene of SPIB, SPIB exerts its anti-colorectal cancer effect by activating NFkB and JNK signaling pathways through MAP4K1. The above findings may provide reference for new molecular markers and therapeutic targets for CRC.