**P?0.01. a hypoxia-related phenotype in these cells. PVT1 knockdown reduced NPC cell proliferation, colony formation, and tumorigenesis in a subcutaneous mouse xenograft model systems. We further found that PVT1 serves as a scaffold for the chromatin modification factor KAT2A, which mediates histone 3 lysine 9 acetylation (H3K9), recruiting the nuclear receptor binding protein TIF1 to activate NF90 transcription, thereby increasing HIF-1 stability and Oxytetracycline (Terramycin) promoting a malignant phenotype in NPC cells. Overexpression of NF90 Oxytetracycline (Terramycin) or HIF-1 restored the proliferation in cells that had ceased proliferating due to PVT1 or KAT2A depletion. Conversely, overexpression of active KAT2A or TIF1, but not of KAT2A acetyltransferase activity-deficient mutants or TIF1 isoforms lacking H3K9ac binding sites, promoted a PVT1-mediated increase in NF90 transcription, as well as increased HIF-1 stability and cell proliferation. PVT1 knockdown enhanced the radiosensitization effect in NPC cells via inhibiting binding between H3K9ac and TIF1 in a manner. Taken together, our results demonstrate that PVT1 serves an oncogenic role and plays an important role in radiosensitivity in malignant NPC via activating the KAT2A acetyltransferase and stabilizing HIF-1. Subject terms: Oncogenes, Protein folding Introduction Nasopharyngeal carcinoma (NPC), which is a form of malignancy arising from the epithelium of the nasopharynx, remains highly prevalent, particularly in Southeast Asia and Southern China [1, Oxytetracycline (Terramycin) 2]. Although intensity-modulated radiation advances in NPC treatment, tumor proliferation, and growth for NPC patients remain to be the important cause of treatment failure and cancer-related death [3, 4]. Recently, an increasing body of evidence has suggested that long noncoding RNAs (lncRNAs) are involved in tumorigenesis through regulating histone modification [5, 6]. However, the mechanisms that account for it remain to be elucidated. Plasmacytoma variant translocation 1 (PVT1) is usually a lncRNA that has been found to serve an oncogenic role in a variety of malignant tumors. PVT1 was first discovered to be frequently translocated in mouse models of plasmacytoma, ultimately contributing to carcinogenesis in Oxytetracycline (Terramycin) these models [7, 8]. Recent evidence further indicates that PVT1 exhibits aberrant expression in nonsmall-cell lung cancer [9C11], cervical cancer , colorectal cancer , and gastric cancer [13, 14]. Moreover, PVT1 expression is usually significantly linked to patient survival in those with colorectal , lung , Oxytetracycline (Terramycin) and breast cancer . PVT1 has been shown to directly bind and stabilize the KLF5 proteins in breast malignancy . Enhancer of zeste homolog 2 (EZH2), a major histone methyltransferase, plays an essential role in tumor regulation via trimethylating lysine 27 on histone H3. EZH2 forms a molecular complex with PVT1 to function as an repressive driver of p15 and p16 in gastric cancer . PVT1 is also transcriptionally activated by FOXM1 in gastric cancer . Furthermore, PVT1 induces radioresistance by influencing cell apoptosis and DNA repair in NPC . However, the specific biological importance and clinical significance of PVT1 in NPC progression remains to be established. In the present study, we found that PVT1 was upregulated in NPC, and that it predicted poor survival in patients. PVT1 promoted this NPC cell proliferation via activating the KAT2A H3K9 acetyltransferase and TIF1 activity to activate NF90 transcription and increase HIF-1 stability. Interestingly, PVT1 contributed to the radiosensitization effect in NPC cells by enhancing the binding of H3K9ac and TIF1 in a manner. Collectively, our results establish a Rabbit Polyclonal to MRPS18C new regulatory mechanism by which PVT1 promotes NPC progression, providing a potential therapeutic target and prognostic factor for NPC. Results The PVT1 lncRNA is usually upregulated in NPC and is associated with a poor prognosis in patients To identify the functions of PVT1 in NPC progression, we first analyzed PVT1 expression in the NP69 immortalized nasopharyngeal epithelial cell line and in five NPC cell lines (HNE-1, C666-1, CNE-1, SUNE-1, and CNE-2). Interestingly, we found that the PVT1 expression level was higher in NPC cell lines than that in NP69 cells (Fig.?1a). We next examined PVT1 expression in ten freshly frozen normal nasopharyngeal specimens and in ten clinical NPC tumor samples. As shown in Fig.?1b, compared with the normal nasopharyngeal epithelial specimens, PVT1 expression was markedly elevated in NPC tumors. To further confirm this obtaining, we obtained gene expression data from the microarray datasets “type”:”entrez-geo”,”attrs”:”text”:”GSE12452″,”term_id”:”12452″GSE12452  and “type”:”entrez-geo”,”attrs”:”text”:”GSE64634″,”term_id”:”64634″GSE64634 , and examined PVT1 was more highly expressed in NPC tissues relative to normal nasopharyngeal tissues (Fig.?1c, d). These results suggest that PVT1 may function as an oncogene that is involved in NPC progression. Open in a separate windows Fig. 1 The PVT1 lncRNA is usually upregulated in NPC and is associated with a poor prognosis in patients. a Expression of PVT1 mRNA is usually higher in NPC cell lines compared with the immortalized nasopharyngeal epithelial cell line. b.