The thyroid hormone activating enzyme, DIO2, is a potential pan-cancer biomarker and immunotherapy target.

Purpose: Type 2 deiodinase (D2), encoded by DIO2 gene, catalyzes the activation of the prohormone thyroxine (T4) into the bioactive hormone triiodothyronine (T3) in peripheral tissues, thereby regulating the intracellular Thyroid Hormone (TH) availability. Recently, several studies have demonstrated that a drastic increase in the peripheral activation of TH, via D2, fosters tumor progression, metastasis, and immunity.

Methods: To further prove the clinical relevance of D2 in human cancer, based on public Database of The Cancer Genome Atlas (TCGA), we conducted a pan-cancer analysis of DIO2 expression in various cancer types and investigated the association of DIO2 expression with the tumor microenvironment (TME) components and immune cell infiltration, along with the DIO2 genetic alteration types.

Results: Although with different expression levels between the various cancer types, the pan-cancer analysis showed that DIO2 was highly expressed in most tumors and related to the progression of some tumor types. Furthermore, DIO2 expression was also significantly correlated with TME components, immune cell infiltration, and immunoinhibitory and immunostimulatory gene subsets.

Conclusion: The relevance of this study is that it adds a clinical relevance to the recent demonstrations that D2 accelerates tumor invasion in animal models and poses DIO2 gene as a potential prognostic marker in various human cancers.