Involvement of Indoleamine 2,3-Dioxygenase in Impairing Tumor-Infiltrating CD8+ T-Cell Functions in Esophageal Squamous Cell Carcinoma

Abstract EN

The indoleamine 2,3-dioxygenase-(IDO-) mediated microenvironment plays an important role in tumor immune escape.

However, the inhibitory effects of IDO on the CD8+ tumour-infiltrating lymphocytes (CD8+ TILs) in esophageal squamous cell carcinoma (ESCC) have not been clarified yet.

Here, we found that the level of IDO expression in ESCC tumor specimens correlated with a reduction in the number of CD8+ TILs.

Patients with high IDO expression and a low number of CD8+ TILs had significantly impaired overall survival time.

IDO expression and functional enzyme activity in ESCC cell lines could be induced by IFNγ.

When exposed to the milieu generated by IDO-expressing Eca109 cells, the CD8+ TILs were suppressed in proliferation, and their cytolytic functions against target tumor cells were lost.

These results suggested that impairing CD8+ TIL functions by IDO expressed in ESCC possibly contributed to the finding that patients with higher IDO expression have more aggressive disease progression and shorter overall survival time.