FoxM1 transactivates PTTG1 and promotes colorectal cancer cell migration and invasion.
BACKGROUND
Metastasis 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.


METHODS
Illumina 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.


RESULTS
Analyses 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.


CONCLUSIONS
PTTG1 is a FoxM1 targeted gene. FoxM1 binds to PTTG1 promoter to enhance PTTG1 transcription, and FoxM1-PTTG1 pathway promotes colorectal cancer migration and invasion.
Department of Medicine, Cedars-Sinai Medical Center, UCLA School of Medicine, Room 3021, 8700 Beverly Blvd, Los Angeles, CA, 90048, USA. zhengyun@mail.sysu.edu.cn.|Sun Yat-sen University Cancer Center; State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, China. zhengyun@mail.sysu.edu.cn.
Yun
Y
Zheng
Department of Medicine, Cedars-Sinai Medical Center, UCLA School of Medicine, Room 3021, 8700 Beverly Blvd, Los Angeles, CA, 90048, USA. guojinjun1972@163.com.|Department of Gastroenterology and Hepatology, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, China. guojinjun1972@163.com.
Jinjun
J
Guo
Division of Epidemiology and Biostatistics, College of Public Health, University of Arizona, Tucson, AZ, USA. jzhou@email.arizona.edu.
Jin
J
Zhou
State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macao, China. jinjian.lu@163.com.
Jinjian
J
Lu
Department of Medicine, Cedars-Sinai Medical Center, UCLA School of Medicine, Room 3021, 8700 Beverly Blvd, Los Angeles, CA, 90048, USA. Qi.Chen@cshs.org.
Qi
Q
Chen
Department of Pathology, Xinxiang Medical University, 601 East Jinsui Ave, Xinxiang, Henan, China. 871685776@qq.com.
Cui
C
Zhang
School of Pharmaceutical Science, Kunming Medical University, 1168 Western Chunrong Road,Yuhua Street, Chenggong New City, Kunming, China. qingchenhh@yeah.net.
Chen
C
Qing
Department of Medicine, Cedars-Sinai Medical Center, UCLA School of Medicine, Room 3021, 8700 Beverly Blvd, Los Angeles, CA, 90048, USA. H.Koeffler@cshs.org.
H Philip
HP
Koeffler
Department of Medicine, Cedars-Sinai Medical Center, UCLA School of Medicine, Room 3021, 8700 Beverly Blvd, Los Angeles, CA, 90048, USA. tongy@cshs.org.|Department of Pathology, Xinxiang Medical University, 601 East Jinsui Ave, Xinxiang, Henan, China. tongy@cshs.org.
Yunguang
Y
Tong
D002465:Cell Movement / Q000235:genetics*; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D000072278:Forkhead Box Protein M1; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D045325:HCT116 Cells; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D008113:Liver Neoplasms / Q000556:secondary; D009361:Neoplasm Invasiveness; D011401:Promoter Regions, Genetic; D064249:Securin / Q000235:genetics*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D015854:Up-Regulation; D051153:Wnt Proteins / Q000037:antagonists & inhibitors
C501126:DKK1 protein, human; C107585:FOXM1 protein, human; D000072278:Forkhead Box Protein M1; D051858:Forkhead Transcription Factors; D036341:Intercellular Signaling Peptides and Proteins; D064249:Securin; D051153:Wnt Proteins; C578002:pituitary tumor-transforming protein 1, human