Increased Levels Of The Long Intergenic Non–protein Coding Rna Pou3f3 Promote Dna Methylation In Esophageal Squamous Cell Carcinoma Cells

BACKGROUND & AIMS: Thousands of long intervening noncoding RNAs(lincRNAs) have been identified in mammals via genome-wide sequencing studies. Many are functional, but are aberrantly expressed by cancer cells. We investigated whether levels of lincRNAs are altered during development of ESCC.METHODS: We used quantitative RT-PCR to measure levels of 26 highly conserved lincRNAs in ESCC and surrounding non-tumor tissues. One hundred eighty-two ESCC and paired adjacent non-tumor tissue samples were collected from patients in Suzhou center; another 178 ESCC tissue pairs were collected from Guangzhou center. lincRNAs were expressed from lentiviral vectors or knocked down with shRNAs in Eca-109, and TE-1cells.RESULTS: Levels of a lincRNA neighboring POU3F3(linc-POU3F3) were significantly higher in ESCC than neighboring non-tumor tissues. In RNA immunoprecipitation assays, linc-POU3F3 associated with the EZH2. Overexpression of linc-POU3F3 in cell lines increased their proliferation and ability to form colonies, and reduced expression of POU3F3, whereas knockdown of linc-POU3F3 increased levels of POU3F3. CpG islands in POU3F3 were densely hypermethylated in cell lines that overexpressed linc-POU3F3; methylation at these sites was reduced by downregulation of linc-POU3F3. Pharmacologic inhibition of EZH2 increased levels of POU3F3 and significantly reduced binding of DNMT1, DNMT3 A, and DNMT3 B to POU3F3. ESCC cells with knockdown of linc-POU3F3 formed xenograft tumors more slowly in mice, compare to the control.CONCLUSIONS: Levels of linc-POU3F3 are increased in ESCC samples from patients, compared with non-tumor tissues. This noncoding RNA contributes to development of ESCC by interacting with EZH2 to promote methylation of POU3F3, a transcription factor.