Twist1 is essential in maintaining mesenchymal state and tumor-initiating properties in synovial sarcoma.
Synovial sarcoma is an aggressive mesenchymal tumor with dual differentiation; epithelial and mesenchymal differentiation. However, the molecular mechanisms behind tumorigenesis and dual differentiation have remained elusive. In this study, we investigated whether Twist1 is an essential transcription factor for maintaining tumor-initiating cell properties in synovial sarcoma. First, we identified that Twist1 is overexpressed in most cases of synovial sarcoma (SS) samples as well as in two synovial sarcoma cell lines (HSSYII, SW982). Additionally, Twist1 depletion led to down-regulation of mesenchymal markers and up-regulation of epithelial markers in SS cell lines. The migratory and invasive abilities of SS cell lines were also significantly reduced following the loss of Twist1. These results indicate that Twist1 plays an essential role in the maintenance of mesenchymal character in SS. Furthermore, knock-down of Twist1 induced G1 cycle arrest and apoptosis as well as remarkable reduction in the sphere-forming cell subpopulation and side population cells. Moreover, Twist1 knock-down profoundly inhibited the growth of synovial sarcoma xenograft in nude mice compared to controls indicating that Twist1 is essential for tumor initiating cell properties. To explore transcriptional regulation by Twist1 at the genomic level, Chromatin immunoprecipiation-solexa whole genome sequencing (ChIP-SEQ) and cDNA microarray analysis were performed. Mesenchymal differentiation/proliferation and PDGF related genes were found to be affected by Twist1. Finally, depletion of SS18-SSX fusion oncoprotein by RNA inference induced down-regulation of Twist1, implying that Twist1 is regulated by SS18-SSX. Hence, our results suggest that Twist1 is an essential transcription factor for the maintenance of mesenchymal characters and tumor initiating properties of synovial sarcoma.
Department of Health Sciences and Technology, Samsung Advanced Institute for Health Sciences and Technology, Sungkyunkwan University, Seoul, Republic of Korea.
Keun-Woo
KW
Lee
Department of Pathology, Samsung Medical Center, Sungkyunkwan University, School of Medicine, Seoul, Republic of Korea.
Nam Kyung
NK
Lee
Department of Life Sciences, POSTECH (Pohang University of Science and Technology), Republic of Korea.
Seokjin
S
Ham
Department of Life Sciences, POSTECH (Pohang University of Science and Technology), Republic of Korea; Division of Integrative Biosciences and Biotechnology, POSTECH (Pohang University of Science and Technology), Republic of Korea. Electronic address: tyroh@postech.ac.kr.
Tae-Young
TY
Roh
Department of Health Sciences and Technology, Samsung Advanced Institute for Health Sciences and Technology, Sungkyunkwan University, Seoul, Republic of Korea; Department of Pathology, Samsung Medical Center, Sungkyunkwan University, School of Medicine, Seoul, Republic of Korea. Electronic address: platoshkim@daum.net.
Seok-Hyung
SH
Kim
D000818:Animals; D017209:Apoptosis; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D002465:Cell Movement; D049109:Cell Proliferation; D047369:Chromatin Immunoprecipitation; D018076:DNA, Complementary / Q000378:metabolism; D015536:Down-Regulation; D017353:Gene Deletion; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008648:Mesoderm / Q000378:metabolism*; D051379:Mice; D008819:Mice, Nude; D009687:Nuclear Proteins / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D034622:RNA Interference; D013584:Sarcoma, Synovial / Q000378:metabolism*; D051879:Twist-Related Protein 1 / Q000378:metabolism*
D018076:DNA, Complementary; D009687:Nuclear Proteins; C103173:TWIST1 protein, human; D051879:Twist-Related Protein 1
Apoptosis; EMT; Synovial sarcoma; Tumor-initiating cells; Twist1