LINC00669 insulates the JAK/STAT suppressor SOCS1 to promote nasopharyngeal cancer cell proliferation and invasion

Nasopharyngeal carcinoma (NPC) is an epithelial cancer emerging from the lining of nasopharyngeal mucosa, with extremely frequent occurrence in east and southeast Asia. For the purpose of exploring roles of the dysregulated long non-coding RNA (lncRNA) in NPC, we identified a novel lncRNA LINC00669 with an apparent negative correlation to the overall survival from human NPC mRNA expression profiling databases. We further performed RNA pulldown coupled with mass spectrum to find out its target protein, and applied a series of in vitro and in vivo loss-and-gain-of function assays to investigate its oncogenic roles in NPC tumor development and progression. Our results demonstrated that LINC00669 competitively binds to the key JAK/STAT signaling pathway suppressor SOCS1, and insulates it from imposing ubiquitination modification on the pathway component of STAT1, which leads to its abnormal stabilization and activation. The activated STAT1 is then transferred into the nucleus and initiates the transcription of genes related to proliferation and invasion. In summary, our study reveals that the cytoplasmic resident lncRNA LINC00669 confers malignant properties on NPC cancer cells by facilitating a persistent activation of the JAK/STAT signaling pathway. Findings in the current study shed lights on prospects for treating NPC using strategies targeting the novel regulator of the JAK/STAT signaling.