Aberrant Overexpression of Satellite Repeats in Pancreatic and Other Epithelial Cancers

From Science

1. David T. Ting¹,*, 
2. Doron Lipson²,*, 
3. Suchismita Paul¹, 
4. Brian W. Brannigan¹ , 
5. Sara Akhavanfard¹, 
6. Erik J. Coffman¹,
7. Gianmarco Contino¹, 
8. Vikram Deshpande¹, 
9. A. John Iafrate¹, 
10. Stan Letovsky², 
11. Miguel N. Rivera¹, 
12. Nabeel Bardeesy¹,
13. Shyamala Maheswaran¹ and 
14. Daniel A. Haber¹,³,^†

Satellite repeats in heterochromatin are transcribed into noncoding RNAs that have been linked to gene silencing and maintenance of chromosomal integrity. Using digital gene expression analysis, we show that these transcripts are greatly overexpressed in mouse and human epithelial cancers. In 8 of 10 mouse pancreatic ductal adenocarcinomas (PDAC), pericentromeric satellites accounted for a mean 12% (range 1 to 50%) of all cellular transcripts, a mean 40-fold increase over normal tissue. In 15/15 human PDACs, alpha satellite transcripts were most abundant and HSATII transcripts were highly specific for cancer. Similar patterns were observed in cancers of lung, kidney, ovary, colon, and prostate. Derepression of satellite transcripts correlated with overexpression of the LINE-1 retrotransposon and with aberrant expression of neuroendocrine-associated genes proximal to LINE-1 insertions. The overexpression of satellite transcripts in cancer may reflect global alterations in heterochromatin silencing and could potentially be useful as a biomarker for cancer detection.