Abstract
BackgroundMetastasis is the major cause of cancer-related death. Forkhead Box M1 (FoxM1) is a master regulator of tumor metastasis. This study aims to identify new FoxM1 targets in regulating tumor metastasis using bioinformatics tools as well as biological experiments.MethodsIllumina microarray was used to profile WT and PTTG1 knockout HCT116 cells. R2 Genomics Analysis was used to identify PTTG1 as a potential FoxM1 targeted gene. Luciferase reporter array, EMSA and Chromatin Immunoprecipitation (ChIP) were used to determine the binding of FoxM1 to PTTG1 promoter. Boyden chamber assay was used to evaluate the effects of FoxM1-PTTG1 on cell migration and invasion. Splenic-injection induced liver metastasis model was used to evaluate the effects of FoxM1-PTTG1 on liver metastasis of colorectal cancer.ResultsAnalyses of multiple microarray datasets derived from human colorectal cancer indicated that correlation levels of FoxM1 and pituitary tumor transforming gene (PTTG1) are highly concordant (R = 0.68 ~ 0.89, p = 2.1E-226 ~ 9.6E-86). FoxM1 over-expression increased and knock-down decreased PTTG1 expression. Luciferase reporter assay identified that the −600 to −300 bp region of PTTG1 promoter is important for FoxM1 to enhance PTTG1 promoter activity. EMSA and ChIP assays confirmed that FoxM1 directly binds to PTTG1 promoter at the −391 to −385 bp region in colorectal cancer cells. Boyden chamber assay indicated that both FoxM1 and PTTG1 regulate migration and invasion of HCT116 and SW620 colorectal cancer cells. Further in vivo assays indicated that PTTG1 knock out decreased the liver metastasis of FoxM1 over-expressing HCT116 cells. Microarray analyses identified 662 genes (FDR < 0.05) differentially expressed between WT and PTTG1−/− HCT116 cells. Among them, dickkopf homolog 1 (DKK1), a known WNT pathway inhibitor, was suppressed by PTTG1 and FoxM1.ConclusionsPTTG1 is a FoxM1 targeted gene. FoxM1 binds to PTTG1 promoter to enhance PTTG1 transcription, and FoxM1-PTTG1 pathway promotes colorectal cancer migration and invasion.Electronic supplementary materialThe online version of this article (doi:10.1186/s12920-015-0126-9) contains supplementary material, which is available to authorized users.
Highlights
Metastasis is the major cause of cancer-related death
Pituitary tumor-transforming gene-1 (PTTG1) activates c-Myc and cyclin D3 (CCND3) to facilitate cell proliferation, increases basic fibroblast growth factor, vascular endothelial growth factor (VEGF) and matrix metalloproteinase 2 (MMP2) expression to induce angiogenesis, which play an important role in tumor development and cancer metastasis, and induces interleukin-8 to function in metastasis [11, 20,21,22]
The results consistently demonstrated that the mRNA levels of PTTG1 and FOXM1 are highly correlated
Summary
Metastasis is the major cause of cancer-related death. Forkhead Box M1 (FoxM1) is a master regulator of tumor metastasis. Colorectal cancer (CRC) is the third most commonly diagnosed cancer and the second leading cause of cancer-related death in the United States. PTTG1 has been identified as a key signature gene associated with tumor metastasis. PTTG1 activates c-Myc and cyclin D3 (CCND3) to facilitate cell proliferation, increases basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF) and matrix metalloproteinase 2 (MMP2) expression to induce angiogenesis, which play an important role in tumor development and cancer metastasis, and induces interleukin-8 to function in metastasis [11, 20,21,22]. PTTG1 interacts with transcription factors including p53, Sp1, and upstream stimulatory factor 1 (USF1), which may induce additional genes involved in tumorigenesis and cancer development [20, 23, 24]. In terms of colorectal cancer, PTTG1 overexpression is associated with tumourigenesis, progression and cancer metastasis [25]
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