OVOL2 links stemness and metastasis via fine-tuning epithelial-mesenchymal transition in nasopharyngeal carcinoma

Abstract

Rationale: Metastasis is the leading cause of disease-related death among patients with nasopharyngeal carcinoma (NPC). Mounting evidence suggest that epithelial-mesenchymal transition (EMT) is crucial for cancer cells to acquire metastatic ability. In this study, we aim to clarify the extent to which EMT is involved in various cancer properties and identify novel markers for predicting the prognosis of NPC patients.Methods: Two cellular models derived from the same NPC cell line with distinct metastasis ability were used for microarray analysis to identify key transcriptional factors that drive metastasis. Cell migration and invasion were analyzed by wound healing and Transwell analysis. Lung metatasis was determined by tail vein injection assay. Cancer stemness was analyzed using colony formation and xenograft assay. The EMT extent was evaluated using immunoblotting, RT-qPCR and immunofluorescence of EMT markers. The value of OVOL2 in prognosis was determined by immunohistochemistry in NPC biopsies.Results: OVOL2 was the most significantly down-regulated EMT transcription factor (EMT-TF) in cellular models of NPC metatasis. Low levels of OVOL2 were associated with poor overall survival of NPC patients and the reduced expression is partly due to promoter methylation and epithelial dedifferentiation. Knockout of OVOL2 in epithelial-like NPC cells partially activates EMT program and significantly promotes cancer stemness and metastatic phenotypes. Conversely, ectopically expression of OVOL2 in mesenchymal-like cells leads to a partial transition to an epithelial phenotype and reduced malignancy. Reversing EMT by depleting ZEB1, a major target of OVOL2, does not eliminate the stemness advantage of OVOL2-deficient cells but does reduce their invasion capacity. A comparison of subpopulations at different stages of EMT revealed that the extent of EMT is positively correlated with metastasis and drug resistance; however, only the intermediate EMT state is associated with cancer stemness.Conclusion: Distinct from other canonical EMT-TFs, OVOL2 only exhibits modest effect on EMT but has a strong impact on both metastasis and tumorigenesis. Therefore, OVOL2 could serve as a prognostic indicator for cancer patients.

Identification of key pathways and genes in nasopharyngeal carcinoma using bioinformatics analysis

“…The results of the KEGG pathway enrichment analysis and GO function annotation revealed that upregulated DEGs were mainly enriched in 'cell adhesion', 'cell division', 'mitosis,' 'mitotic cell cycle', 'ECM-receptor interaction' and 'human papillomavirus infection', whereas downregulated DEGs were mainly involved in 'axonemal dynein complex assembly', 'microtubule-based movement', 'metabolic pathways', 'Huntington's disease', 'fluid shear stress' and 'atherosclerosis' and 'chemical carcinogenesis'. Previous studies have demonstrated that upregulation or downregulation of specific genes may affect NPC cell invasion, metastasis, proliferation and apoptosis (28)(29)(30). This result is consistent with the fact that carcinoma cell invasion and metastasis are closely associated with abnormal cell adhesion and cell division (28)(29)(30).…”

“…This result is consistent with the fact that carcinoma cell invasion and metastasis are closely associated with abnormal cell adhesion and cell division (28)(29)(30). Furthermore, cancer cell proliferation and apoptosis are closely associated with abnormalities in the mitotic cell cycle (28)(29)(30). A previous study indicated that colorectal cancer cells interact with stromal cells by producing ECM components, mediating direct cell-cell contact and secreting growth factors (31).…”

“…Previous studies have demonstrated that upregulation or downregulation of specific genes may affect NPC cell invasion, metastasis, proliferation and apoptosis (28)(29)(30). This result is consistent with the fact that carcinoma cell invasion and metastasis are closely associated with abnormal cell adhesion and cell division (28)(29)(30). Furthermore, cancer cell proliferation and apoptosis are closely associated with abnormalities in the mitotic cell cycle (28)(29)(30).…”

New Insights Into the Role of Phenotypic Plasticity and EMT in Driving Cancer Progression

“…For example, studies with a Snail-inducible expression system in prostate cancer cells has identified metabolic plasticity and asymmetrical dynamics during their EMT-MET cycle (Stylianou et al, 2019). Other studies, where re-expression of significant epithelial markers such as E-cadherin, OVOL2 and GRHL2 after their knockout may not obtain the same spectrum of reversion also suggests asymmetrical dynamics (Qi et al, 2018;Chung et al, 2019;. The concept of bet hedging had been observed in bacterial persistence under different environmental stimulations by generating mutationindependent phenotypic heterogeneity (Veening et al, 2008).…”

OVOL2 in metastasis prevention in NPC

“…In this issue of Theranostics , Feng and colleagues describe the role of OVOL2, a member of the Ovo family of conserved zinc-finger transcription factors, in metastasis and the enrichment of stemness in NPC 7 . Although OVOL2 was cloned nearly 20 years ago 8 , compared to other transcription factors involved in EMT, much less is known about OVOL2.…”