NADPH Oxidase NOX4 Is a Critical Mediator of BRAF^V600E-Induced Downregulation of the Sodium/Iodide Symporter in Papillary Thyroid Carcinomas

Abstract

Here, using two human BRAF-mutated thyroid cell lines and a rat thyroid cell line expressing BRAF in a conditional manner, we show that NOX4 upregulation is controlled at the transcriptional level by the oncogene via the TGF-β/Smad3 signaling pathway. Importantly, treatment of cells with NOX4-targeted siRNA downregulates BRAF-induced NIS repression. Innovation and Conclusion: Our results establish a link between BRAF and NOX4, which is confirmed by a comparative analysis of NOX4 expression in human (TCGA) and mouse thyroid cancers. Remarkably, analysis of human and murine BRAF-mutated thyroid tumors highlights that the level of NOX4 expression is inversely correlated to thyroid differentiation suggesting that other genes involved in thyroid differentiation in addition to NIS might be silenced by a mechanism controlled by NOX4-derived ROS. This study opens a new opportunity to optimize thyroid cancer therapy. Antioxid. Redox Signal. 26, 864-877.

Regulation of thyroid sodium‐iodide symporter in different stages of goiter: Possible involvement of reactive oxygen species

“…It is important to underline that this is the group in which both TGFβ and TGFβ receptor mRNA levels were higher than the control group. This result suggests that this cytokine might have a stimulatory effect on NOX4 physiologically in the thyroid gland, as previously described in other tissues, and also in thyroid cancer …”

“…This result suggests that this cytokine might have a stimulatory effect on NOX4 physiologically in the thyroid gland, as previously described in other tissues, [23][24][25] and also in thyroid cancer. 30 In agreement with the increased NOX4 mRNA levels, we also found a rise in thyroid H 2 O 2 generation in the group R1d-21d ( Figure 4B). It is important to underline that this measurement was done in the absence of calcium, since in the thyroid there are two additional NOX, DuOx1 and DuOx2, which are calcium-dependent.…”

“…[26][27][28][29] Recently, it has been shown that NOX4 is regulated by BRAF V600E oncogene in a TGFβ-dependent manner and that NOX4-dependent ROS generation was critical in NIS repression induced by BRAF V600E oncogene in thyroid cancer cells. 30 Thus, the production of ROS by NOX4 seems to play a critical role in the regulation of thyroid NIS expression and iodide uptake.…”

Oxidative stress in thyroid carcinomas: biological and clinical significance

“…The link between BRAF V600E and NOX4 was confirmed by a comparative analysis of NOX4 expression in human (TCGA) and mouse thyroid cancers. The level of NOX4 expression in human and murine BRAF V600E -mutated thyroid tumours is inversely correlated with thyroid differentiation; this suggests that genes other than NIS that are involved in thyroid differentiation might be silenced by a mechanism controlled by NOX4-derived ROS (Azouzi et al 2017). However, further investigations are needed to determine whether this increase in NOX4 expression is a cause or a consequence of the thyroid dedifferentiation process.…”

Treatment of refractory thyroid cancer

“…This results in a decreased expression of thyroid functional proteins, including NIS and TPO that is likely to 156 be due to epigenetic changes and is reversible (Azouzi, et al 2017). In a pilot study on 20 patients with 157 metastatic differentiated thyroid carcinoma who had no significant RAI uptake in their metastases, lesional 158 dosimetry with 124 I PET imaging was performed following rhTSH stimulation after 4 weeks of treatment with 159 the MEK inhibitor, selumetinib.…”