Immune-Related Adverse Events: Regulatory T Cells

Abstract: While regulatory T cells (Treg) are a direct target of immune checkpoint inhibitor (ICI) immunotherapy, inflammatory Treg reprogramming is also a feature of immune-related adverse events (irAEs) in autoimmune diseases
.

The authors of this paper point out the direction for related research: exploring the peripheral immune response to determine the mechanism of irAEs
.

Identifying the mechanisms by which ICI therapy-induced decreased patient tolerance and irAEs occur will advance our understanding of immune dysregulation in cancer and help manage irAEs
.

 Introduction: Immune checkpoint inhibitors (ICIs) target immunomodulatory pathways to increase antitumor responses, revolutionizing cancer immunotherapy
.

Despite the remarkable success of ICI immunotherapy, a subset of patients experience immune-related adverse events (irAEs) similar to autoimmune diseases
.

Although the clinical features of irAEs are clear, the pathogenic mechanism of irAEs remains unclear
.

Introduction: Here, the authors focus on regulatory T cells (Treg) in patients with irAEs, as these cells are critical in maintaining peripheral immune tolerance, Tregs expand in the peripheral blood of cancer patients and express checkpoints abundantly molecule, and thus a direct target of ICI immunotherapy
.

The authors found transcriptional reprogramming of CD4+CD25+CD127-Tregs with inflammatory, apoptotic and metabolic signatures in the blood of melanoma patients with irAEs
.

Tregs from different cancer patients (who developed irAEs) and patients with autoimmune diseases have this inflammatory signal
.

The authors' findings suggest that inflammatory Treg reprogramming is a feature of the development of irAEs, which may contribute to the induction of antitumor immunity in the future without interfering with peripheral tolerance
.

Interpretation of results: The molecular mechanism of transcriptional reprogramming of Tregs in melanoma patients with irAEs remains unclear, and the description of the mechanism will help to design translational methods to induce robust antitumor immunity (without interfering with peripheral immune resistance).
received)
.

CD4+CD25+CD127-Tregs were isolated from the blood of patients with advanced melanoma receiving anti-PD1 therapy and subjected to transcriptional analysis
.

Of these, 11 patients developed irAEs, such as hypoportulitis, thyroiditis, psoriasis, and colitis, hereafter referred to as Mel-irAEs, and 15 patients did not (referred to as Mel-ctrl) although the authors did not observe Mel-irAEs and Mel-irAEs The frequencies of CD4+CD25+CD127-Tregs were significantly different between -ctrls, but genome-wide RNA-seq analysis revealed 252 differentially expressed genes between the two groups
.

Focusing on Treg biology and immune-related genes, the authors identified a core signature of upregulated transcription by Mel-irAEs (compared to Mel-ctrl) (Fig.
1A)
.

These include genes that encode chemokines and chemokine receptors, such as CXCL2, CXCL16, CXCL10 and CCR1, which are involved in inflammation and leukocyte migration; and enzymes such as amino acids that break down ARG1 and the antioxidant SOD2
.

In contrast, genes involved in the function of activating Tregs, such as CCR3 and SERPINE2, or genes in metabolic processes, such as ADAM12 and ATP6AP11, were significantly downregulated in Mel-irAE Tregs (Fig.
1A)
.

Pathway analysis of DEGs showed that compared with Mel-ctrl Tregs, Mel-irAEs Tregs exhibited an inflammatory phenotype including leukocyte activation, inflammatory response, cytokine production, oxidative stress, type I interferon signaling, and interferon gamma signaling (Figure 1B)
.

In detail, GSEA demonstrated that MEL-irAEs Tregs are enriched in pro-inflammatory processes such as "IFNγ response", "TNF-α signaling via NFKb" and "IL-6/JAK/STAT3 signaling" (Fig.
1C).
)
.

Treg metabolism drives proliferative and immunosuppressive properties at steady state, and unstable metabolism contributes to the emergence of autoimmune diseases
.

In this context, the authors analyzed using GSEA and showed that Mel-irAEs Tregs undergo metabolic rearrangement compared to Mel-ctrl Tregs
.

The metabolic rearrangement of Mel-irAEs Tregs was characterized by "MTORC1 signaling", "reactive oxygen species pathway" and "Fatty acid metabolism" (Fig.
1C)
.

These data provide new insights into the signaling of CD4+CD25+CD127-Tregs reprogramming in advanced melanoma patients who develop irAEs following ICI immunotherapy, shift to a proinflammatory phenotype, and are accompanied by metabolic changes
.

Figure 1.
Treg inflammatory transcriptional reprogramming in advanced melanoma patients with irAEs
.

 Common inflammatory and metabolic features of autoimmune diseases and irAE Tregs Although irAEs share a wide range of clinical features, it is not yet clear that they share pathogenic features with autoimmune syndromes
.

Compared with Tregs from healthy individuals, Tregs from autoimmune diseases displayed a dysregulated transcriptional program similar to the phenotype of Mel-irAEs Tregs (Fig.
2A)
.

GSEA analysis showed that DEGs of Mel-irAEs Tregs were overexpressed in autoimmune disease Tregs, including IFNγ signaling (CXCL10, IFNGR2, BCL3 and CD63), leukocyte activation (IRF1, ARG1, NLRP3, IFNGR1 and STAT3), autophagy regulation (MAP1LC3B, BNIP3L, FOXO3, LAMTOR5 and RAB5A), apoptosis (MAP1LC3B, BNIP3L, FOXO3, LAMTOR5 and RAB5A) and metabolic process regulation (Ldlr, ATF3, MAP3K8, related genes (Figures 2A and 2B)
.

In conclusion, The authors' findings suggest that Tregs from patients with autoimmune diseases and patients with irAEs share a common transcriptional profile
.

This profile is enriched in inflammatory, apoptotic and metabolic pathways and is characteristic of unstable Tregs
.

Figure 2.
Transcriptional profile of inflammatory Tregs: Common features of autoimmune diseases and irAEs
.

 Transcriptional profiles of irAE Tregs are common in different types of cancer.
To examine whether inflammatory reprogramming of Tregs is specific to melanoma patients undergoing irAEs following anti-PD1 immunotherapy, the authors Transcriptional analysis (denoted as CA-irAEs or CA-ctrl, respectively) was performed on Tregs (denoted as CA -irAEs or CA-ctrl, respectively) in patients with and without irAEs (renal cancer, liver cancer, bladder cancer, and non-small cell lung cancer after anti-PD1 immunotherapy)
.

Compared with -ctrl Tregs, CA-irAEs Tregs have obvious transcriptional differences, with a total of 225 DEGs
.

Pathway analysis shows that the inflammatory characteristics of CA-irAEs Tregs are very similar to Mel-irAEs Tregs, including leukocyte activation, cytokine production, and immune effector processes.
and stress responses were among the most significantly enriched pathways (Fig.
3B)
.

GSEA analysis further confirmed the unstable inflammatory phenotype of CA-irAEsTregs, similar to Mel-irAEsTregs
.

In detail, IFNγ response (through IRF1, IRF2, IRF7, IRF9, STAT1, STAT2, CCL5, CXCL9, CXCL10 and CD274 genes), IFNα response (genes with the highest abundance, such as IRF1, IRF2, IRF7, IRF9, STAT2 , CXCL10, IFITs and IFI) and IL2-STAT5 signaling (IL1R2, EOMS, BCL2L1, SOCS1, CXCL10, CS2 and TNFSF10) were the most abundant pathways (Fig.
3C)
.

Notably, upstream regulators of Tregs activated in CA-irAEs include: IFNγ, IFNα, IL-17A, TBX, NFkB, HIF1A, IRF1, RUNX1, IL-1B, TNFSF10, STAT1, STAT3 and STAT6 (Fig.
3D)
.

Taken together, these findings identify Tregs isolated from patients with irAEs with a distinct pro-inflammatory transcriptional signature that is common across different types of cancer
.

Figure 3.
Pro-inflammatory transcriptional profiles shared among Tregs across multiple cancers
.

 Universal Treg signaling in irAEs and patients with autoimmune disease Since peripheral blood remains the most accessible tissue and irAEs develop throughout the body, the authors reasoned that identifying signatures in circulating Tregs could characterize the development of irAEs regardless of cancer type
.

To this end, the authors compared gene expression in Mel-irAEs, CA-irAEs, autoimmune disease, and healthy Treg (Fig.
4A)
.

Comparison of genomes in three disease settings revealed 93 common DEGs (1.
8% overlap), regulated by involvement in Treg immune-related processes and inflammatory responses (including SOCS1, SOCS3, IFNG, RORC, IL17RE, ARG1, AREG, and SEMA6B) ) of the 19 genes of the salient core feature composition (Fig.
4A)
.

Pathway analysis revealed that 93 common DEGs were mainly involved in inflammatory processes, with high enrichment in IFNγ-mediated responses, immune activation and stress responses (Fig.
4B)
.

Taken together, the authors' findings reveal Treg inflammatory signatures that are prevalent in irAEs across different cancer types, which are the same as Tregs in autoimmune diseases, suggesting that targeting these features may aid in the design of new therapeutic approaches to manage irAEs.
And hope for the development of liquid "biopsy"
.

Figure 4.
Pan-cancer Treg inflammatory signaling in irAEs and autoimmune diseases
.

 Summary of the full text: Increased Tregs in the TME, a hallmark of tumors, are associated with tumor cell aggressiveness and impaired immunotherapy response, but the development of irAEs may be mediated by dysregulated immune responses in peripheral lymphatic compartments
.

Therefore, analysis of blood can reveal the pathogenic mechanism of irAEs
.

Since ICI immunotherapy is administered intravenously, Tregs expressing a large number of checkpoint molecules (ie, PD1 and CTLA4) will be targeted, which may lead to dysregulation of peripheral tolerance
.

The authors' findings highlight that in ICI immunotherapy, peripheral Tregs in patients with irAEs are reprogrammed to inflammatory signals, filling this gap
.

Taken together, the authors' data suggest that we should further explore peripheral immune responses to determine the mechanisms by which irAEs occur
.

Identifying the mechanisms by which ICI therapy-induced decreased patient tolerance and irAEs occur will advance our understanding of immune dysregulation in cancer and help manage irAEs
.

Reference 1.
Grigoriou M, Banos A, Hatzioannou A, et al.
Regulatory T-cell Transcriptomic Reprogramming Characterizes Adverse Events by Checkpoint Inhibitors in Solid Tumors.
Cancer Immunol Res Jul 2021;9(7):726-734.
doi:10.
1158 /2326-6066.
CIR-20-0969 .
For more information on bioinformatics analysis questions: 18501230653 (same number on WeChat) Bioinformatics analysis good article recommendation 01 Master of immunity: Academician Dong Chen's research results are summarized 02 Zhang Zemin's series of research results are summarized 03 Single-cell research tumor immunotherapy case sharing 04 Prognostic models can still be novel and dazzling