The expression level of IDO2 is linked with aggressive characteristics in medullary thyroid carcinoma (MTC) and is also predictive of poor prognosis, according to a new study published in the journal BMC Cancer.

Notably, the involvement of IDO2 in the disease showed a moderate sexual dimorphism, with women with the disease being more affected by the IDO2 status than men. 

The study also showed there was a close association between CD4 + T and IDO2 cell infiltration in the cancer microenvironment.

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IDO2 could “serve as an alternative drug target in cancer immunotherapy and as a new prognostic tool,” the study authors concluded.

To explore the possible link between IDO2 status and the clinicopathological parameters, prognosis, and immunomodulatory functions in MTC, the researchers first evaluated the expression levels of IDO2 protein in resected MTC surgical specimens and corresponding lymph nodes. They then evaluated CD4 + T cell infiltration in these tissues.

They found that high IDO2 expression was closely linked with more aggressive clinicopathological disease features. For example, tumors in which IDO2 was highly expressed were multifocal, had extrathyroidal extensions, and were of a higher pT and pN stage.

The recurrence free-survival also differed significantly between patients whose tumor had high IDO2 expression and those whose tumor had low IDO2 expression. 

Moreover, the expression of IDO2 in the lymph nodes was significantly associated with the metastasis state.

There was a negative correlation between IDO2 expression and CD4 + T cell infiltrations in MTC tissues. 

IDO2, or indoleamine 2,3-dioxygenase 2, is an enzyme that catalyzes the first step in the catabolism of tryptophan in the kynurenine pathway. It is known to play a role in immune regulation. Its role in cancer progression remains to be explored further.


Gu P, Ling B, Ma W, et al. Indoleamine 2,3-dioxygenase 2 immunohistochemical expression in medullary thyroid carcinoma: implications in prognosis and immunomodulatory effects. BMC Cancer. Published online November 1, 2022. doi:10.1186/s12885-022-10173-7