Metastasis, a powerful prognostic indicator of oral squamous cell carcinoma (OSCC), is chiefly responsible for poor cancer outcomes. Despite an increasing number of studies examining the mechanisms underlying poor outcomes, the development of potent strategies is hindered by insufficient characterization of the crucial regulators. Long noncoding RNAs (lncRNAs) have recently been gaining interest as significant modulators of OSCC metastasis; however, the detailed mechanisms underlying lncRNA-mediated OSCC metastasis remain relatively uncharacterized. Here, we identified a novel alternative splice variant of oral cancer overexpressed 1 (ORAOV1), named as ORAOV1-B, which was subsequently validated as an lncRNA and correlated with OSCC lymph node metastasis; significantly increased invasion and migration were observed in ORAOV1-B-overexpressing OSCC cells. RNA pulldown and mass spectrometry identified Hsp90 as a direct target of ORAOV1-B, and cDNA microarrays suggested TNFα as a potential downstream target of ORAOV1-B. ORAOV1-B was shown to directly bind to and stabilize Hsp90, which maintains the function of client proteins, receptor-interaction protein, and IκB kinase beta, thus activating the NF-κB pathway and inducing TNFα. Additionally, TNFα reciprocally enhanced p-NF-κB-p65 and the downstream epithelial-mesenchymal transition. ORAOV1-B effects were reversed by a TNFα inhibitor, demonstrating that TNFα is essential for ORAOV1-B-regulated metastatic ability. Consistent epithelial-mesenchymal transition in the ORAOV1-B group was demonstrated via an orthotopic model. In the metastatic model, ORAOV1-B significantly contributed to OSCC-related lung metastasis. In summary, the novel splice variant ORAOV1-B is an lncRNA, which significantly potentiates OSCC invasion and metastasis by binding to Hsp90 and activating the NF-κB-TNFα loop. These findings demonstrate the versatile role of ORAOV1 family members and the significance of genes located within 11q13 in promoting OSCC. ORAOV1-B might serve as an attractive OSCC metastasis intervention target.
Keywords: RNA; alternative splicing; epithelial-mesenchymal transition; long noncoding; molecular chaperones.