CHD4 and NOX4 expression in thyroid tumor tissues

Aim: Chromodomain-helicase-DNA-binding protein 4 (CHD4) is a core NURD remodeling complex ATPase that plays a crucial role as a gene repressor. Its overexpression has been reported in several cancers. In papillary thyroid carcinomas (PTCs), CHD4 is overexpressed and associated with aggressive features of the tumor, such as proliferation, migration, and epithelial-mesenchymal transition (EMT). We previously showed in PTCs that NADPH oxidase NOX4 expression is positively regulated by BRAFV600E mutation, which is the most aggressive alteration in PTCs. In this retrospective study, we wondered whether there is a link between CHD4 and NOX4 protein expression in malignant thyroid tissues. Methods: We explored CHD4 protein expression by immunostaining analysis in 86 human thyroid tissues: 44 thyroid tumor tissues [28 classical forms of PTCs (C-PTCs), 13 follicular variants of PTCs (F-PTCs), and three anaplastic thyroid carcinomas (ATCs)] and 42 of their normal adjacent tissues (NATs). The detection of BRAFV600E mutation was performed using Sanger sequencing and digital droplet PCR. Statistical analyses were conducted using GraphPad Prism 8 software. Various tests were used to assess the statistical relevance of different correlations, such as the chi-square test, Fisher’s exact test, and the Pearson correlation coefficient. A p-value of less than 0.05 indicates statistical significance. Results: The CHD4 protein expression analysis with already published data from our group (BRAFV600E status and NOX4 expression) reveals a highly significant level of CHD4 protein expression in C-PTCs compared to F-PTCs and ATC. Importantly, 70% of C-PTCs-BRAFV600E overexpress CHD4 at the protein level, confirming the positive correlation between the CHD4 expression and BRAFV600E mutation. Furthermore, a high level of CHD4 is associated with the presence of capsular breach and vascular emboli, affirming the involvement of CHD4 in thyroid tumor aggressiveness. Interestingly, we showed for the first time, to our knowledge, a positive correlation between CHD4 and NOX4 protein expression in malignant thyroid tissues. Conclusions: The results of this study suggest that CHD4 could be used as a complementary molecular marker to improve the diagnosis and the management of PTCs-BRAFV600E.