SYT-SSX is critical for cyclin D1 expression in synovial sarcoma cells: a gain of function of the t(X;18)(p11.2;q11.2) translocation.
The SYT-SSX fusion gene has been implicated in the malignant tumor cell growth of synovial sarcoma, but the underlying molecular mechanisms are still poorly understood. Here we demonstrate that SYT-SSX is critical for the protein level of cyclin D1 in synovial sarcoma cells. Antisense oligonucleotides to SYT-SSX mRNA rapidly and drastically decreased cyclin D1 and subsequently inhibited cell growth. This effect is specific for SYT-SSX, without involving the wild-type genes SYT or SSX. The decrease in cyclin D1 expression, which occurred shortly after inhibition of SYT-SSX expression, was found to be primarily dependent on an increased degradation of the cyclin D1 protein, as assessed by pulse-chase experiments using [(35)S]methionine. Furthermore, transfection of mouse fibroblasts with SYT-SSX cDNA increased the stability of cyclin D1. Because treatment with a proteasome inhibitor restored cyclin D1 expression, it seems like SYT-SSX interferes with ubiquitin-dependent degradation of cyclin D1. However, SYT-SSX-regulated cyclin D1 expression was proven to be independent of the glycogen synthetase kinase-3beta pathway. Taken together, our study provides evidence that SYT-SSX stabilizes cyclin D1 and is critical for cyclin D1 expression in synovial sarcoma cells. SYT-SSX-dependent expression of cyclin D1 may be an important mechanism in the development and progression of synovial sarcoma and also raises the possibility for targeted therapy.
Xie
Yuntao
Y
Department of Oncology and Pathology, Karolinska Hospital, SE-171 76 Stockholm, Sweden.
Skytting
Björn
B
Nilsson
Gunnar
G
Gasbarri
Alessandra
A
Haslam
Karl
K
Bartolazzi
Armando
A
Brodin
Bertha
B
Mandahl
Nils
N
Larsson
Olle
O
D016475:3T3 Cells; D000818:Animals; D002455:Cell Division / Q000502:physiology; D002887:Chromosomes, Human, Pair 18; D019938:Cyclin D1 / Q000096:biosynthesis* / Q000378:metabolism; D015536:Down-Regulation; D006801:Humans; D051379:Mice; D016376:Oligonucleotides, Antisense / Q000235:genetics / Q000494:pharmacology; D015514:Oncogene Proteins, Fusion / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D013584:Sarcoma, Synovial / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D014162:Transfection; D014178:Translocation, Genetic; D014407:Tumor Cells, Cultured; D014960:X Chromosome
D019938:Cyclin D1; D016376:Oligonucleotides, Antisense; D015514:Oncogene Proteins, Fusion; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; C116512:SYT-SSX fusion protein