Exhaustion of CD4+ T-cells mediated by the Kynurenine Pathway in Melanoma

Soudabeh Rad Pour,Gowhar Shafi,Jesper Tegnér,Mingmei Shang,Muyi Yang,Daniel F J Ketelhuth,Narsis A Kiani,Craig E Wheelock,Alireza Azimi,Roland Baumgartner,Muhammad Anas Kamleh,Andreas Lundqvist,Hiromasa Morikawa,Johan Hansson

doi:10.1038/s41598-019-48635-x

Abstract

Kynurenine pathway (KP) activation by the enzymatic activity of indoleamine 2,3-dioxygenase1 (IDO1) and kynurenine (KYN) production represents an attractive target for reducing tumour progression and improving anti-tumour immunity in multiple cancers. However, immunomodulatory properties of other KP metabolites such as 3-hydroxy kynurenine (3-HK) and kynurenic acid (KYNA) are poorly understood. The association of the kynurenine metabolic pathway with T-cell status in the tumour microenvironment were characterized, using gene expression data of 368 cutaneous skin melanoma (SKCM) patients from the TCGA cohort. Based on the identified correlations, we characterized the production of KYN, 3-HK, and KYNA in vitro using melanoma-derived cell lines and primary CD4+ CD25− T-cells. Activation of the CD4+ T-cells produced IFNγ, which yielded increased levels of KYN and KYNA. Concurrently, kynurenine 3-monooxygenase (KMO) expression and proliferation of CD4+ T-cells were reduced, whereas exhaustion markers such as PD-L1, AHR, FOXP3, and CTLA4 were increased. Additionally, an analysis of the correlation network reconstructed using TCGA-SKCM emphasized KMO and KYNU with high variability among BRAF wild-type compared with V600E, which underscored their role in distinct CD4+ T-cell behavior in tumour immunity. Our results suggest that, in addition to IDO1, there is an alternative immune regulatory mechanism associated with the lower KMO expression and the higher KYNA production, which contributes to dysfunctional effector CD4+ T-cell response.

Highlights

Melanoma is the most fatal forms of skin cancer arises from the malignant transformation of the melanocytes of which cutaneous melanoma is the most common form[1,2]
To explore whether kynurenine metabolic pathway is associated with T-cell status in the tumour microenvironment, gene expression data of mRNA of 368 cutaneous melanoma metastases (SKCM) in the the cancer genome atlas (TCGA) cohort were divided into groups with low and high expression of T-cell signature genes which has reported previously[33] (Fig. 1a)
Spearman correlation coefficient analyses were performed on kynurenine pathway-related genes (IDO1/2, TDO2, kynurenine 3-monooxygenase (KMO), KYNU, CCBL1/2, GOT2, AADAT, and ACMSD) and T-cell status-related genes which showed that expression of Indoleamine 3-Dioxygenase1 (IDO1), IDO2, KYNU, and KMO are associated with T-cell status-related genes (Fig. 1b, Table S3, Supplementary Fig. S4)

Summary

Introduction

Melanoma is the most fatal forms of skin cancer arises from the malignant transformation of the melanocytes of which cutaneous melanoma is the most common form[1,2]. It has been shown that the level of Tregs is augmented in a different type of cancer such as melanoma, where they prevent anti-tumour immune responses[10]. We characterized the association of the kynurenine metabolic pathway with T-cell status in the tumour microenvironment, using gene expression data of cutaneous skin melanoma (SKCM) patients from the TCGA cohort. In this respect, based on the identified correlations, we characterized the production of KYN, 3-HK, and KYNA in vitro using melanoma-derived BRAF wild type (wt) and BRAF V600E mutant cell lines cultured with primary CD4+ CD25− T-cells. The correlation network was analysed in order to investigate the correlation networks for CD4+ T-cells and KP-related genes in BRAF V600E compared with BRAF wt SKCM-TCGA data

Methods

Results

Conclusion