Epigenetic regulation of c-ROS receptor tyrosine kinase expression in malignant gliomas.
The proto-oncogene tyrosine kinase c-ROS is an orphan receptor whose normal expression pattern is tightly spatio-temporally restricted during development. In glioma, c-ROS mRNA expression is frequently ectopically up-regulated. In this study, we determined by immunohistochemical means that c-ROS receptor protein is present in 25% of low-grade and 30% of malignant glioma tumor samples from tissue microarrays. We then explored the molecular basis for the up-regulation of c-ROS expression in these tumors. We identified and characterized the c-ROS gene promoter region and report that the ectopic expression of c-ROS in tumors is tied to hypomethylation of a CpG island in the c-ROS promoter. Bisulfite sequencing analysis in glioma tumor samples revealed that demethylation of the CpG island (-384 to -132 bp) correlated with c-ROS expression. Moreover, c-ROS expression could be activated by treatment of c-ROS-negative cells with the demethylating agent 5-aza-2'-deoxycytidine. These results establish a strong link between c-ROS promoter demethylation and gain of c-ROS expression and function in glioma. Our data suggest that epigenetic activation of c-ROS represents an important oncogenic mechanism for glioma initiation and progression and suggest that cautionary measures in the clinical use of 5-aza-dC for the treatment of glioma be taken into consideration. [Cancer Res 2009;69(6):2180-4].
Jun
Hyun Jung
HJ
Molecular Oncology Research Institute and Department of Neurosurgery, Tufts University School of Medicine, Tufts Medical Center, Boston, Massachusetts.
Woolfenden
Steve
S
Coven
Shanie
S
Lane
Keara
K
Bronson
Roderick
R
Housman
David
D
Charest
Alan
A
D001254:Astrocytoma / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics* / Q000473:pathology; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D019175:DNA Methylation; D000077209:Decitabine; D018450:Disease Progression; D044127:Epigenesis, Genetic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D046228:Microarray Analysis; D011401:Promoter Regions, Genetic; D000090063:Proto-Oncogene Mas; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020794:Receptor Protein-Tyrosine Kinases / Q000096:biosynthesis* / Q000235:genetics*; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D012333:RNA, Messenger; D000077209:Decitabine; D020794:Receptor Protein-Tyrosine Kinases; D001374:Azacitidine