Linking Leukemia and Autoimmune Disease Through STAT3 Mutations
Summary
Unknown mechanisms underlie the association between autoimmune disorders and cancer, as seen in T-cell large granular lymphocytic leukemia (T-LGL), where acquired of function (GOF) somatic STAT3 mutations are linked to concurrent autoimmunity. They examined humans and mice with germline STAT3 GOF mutations to determine whether these mutations are contributing factors to CD8+ T cell clonal expansion and autoimmunity or a symptom of them. Effector CD8+ T cell clones with high expression of NKG2D, a receptor for stress-induced MHC-like I-associated molecules, remarkably accumulate due to STAT3 GOF mutations. In addition, Granzyme, perforin, interferon-gamma, and Ccl5/Rantes are also expressed by this subset, which necessitates NKG2D and the IL-15/IL-2 receptor IL2RB for maximum accumulation. For lethal disease in mice, leukocyte-restricted STAT3 GOF is sufficient, but CD8+ T cells are needed. These findings support the notion that somatic mutations in leukemia/lymphoma driver genes result in autoimmune disease by causing the buildup of effector CD8+ T cell oligoclones and their contribution to autoimmune pathology.
Fig.1 Graphical abstract. (Masle-Farquhar, 2022)
Research Criteria
To explore the dysregulated effector/memory CD8+ T cells in STAT3 GOF syndrome, they performed single cell receptor and gene expression RNA sequencing (RAGE-seq) and cellular indexing of transcriptomes and epitopes by sequencing (CITE-seq) on non-naïve (excluding CD45RA+ CCR7+) CD8+ T cells sorted by FACS and CD8- CD4+ cells from PBMCs of 2 controls and 2 patients.
Fig.2 Experimental design. (Masle-Farquhar, 2022)
Sample Type
Cells from Blood, Bone Marrow, Lymph Node, and Spleen.
Result—Clonally Expanded CD57+ effector CD8+ T Cells Expressing Numerous Killer Cell Genes in STAT3 GOF Syndrome
Patients' and controls' non-naive CD8+ T cells have different transcriptional profiles. 16 different non-naive CD8+ T cell clusters were found using an unsupervised dimensionality reduction analysis of the scRNA-seq data for STAT3 GFO and control non-naive CD8+ T cells. Most of the cells in these clusters that had an assignable TCR VDJ clonotype were enlarged clones, defined as having more than five cells with the same VDJ clonotypic sequence, according to RAGE-seq results. By deep TCRB VDJ mRNA sequencing of sorted NKG2Dhi CD8+ T cells from 6 patients and 6 controls, they investigated the frequencies of clonally expanded NKG2Dhi CD8+ T cells from additional STAT3 GOF patients. Compared with the largest clonotypes made up 2.8%–29.5% (mean 10.80%) of unique transcripts, control patients had 2.8%–8.5% (representing 4.7%). The five biggest clonotypes accounted for 10.3%–47.3% (mean 22.8%) of unique transcripts in patients and 8.4%–24.9% (mean 15.1%) in controls. Thus, germline STAT3 GOF patients and healthy individuals have significant clonal CD8+ T cell expansions.
Fig.3 Clonally expanded CD57+ effector CD8+ T cells expressing numerous killer cell genes in STAT3 GOF syndrome patients. (Masle-Farquhar, 2022)
Result—Accumulating NKG2D+ CD8+ T Cells in Stat3 GOF Mice Over-Express Cell Cycle and Killer Cell Genes
ScRNA-seq was carried out on mouse spleen NKG2D+ CX3CR1+ CD8+ T cells as an add-on to the human investigation. NKG2D+ CX3CR1+ CD8+ T cells from Stat3T716M/T716M mice differentially expressed 4667 genes in comparison to total CD8+ T cells from the same animals. The study was confirmed by the first and third most elevated RNAs in the sorted cells, which were those encoding the two markers utilized for sorting, Klrk1 and Cx3cr1. Additionally, the number of mRNAs encoding perforins, granzymes, interferon-gamma, chemokines, NK cell-associated receptor and signaling molecules, as well as the transcription factors Zeb2, Prdm1, Id2, Eomes, and Stat4 that support memory/effector CD8+ T cell differentiation, was increased in NKG2D+ CX3CR1+ CD8+ T cells. The findings demonstrated that the dysregulated effector memory CD8+ T cells in Stat3 GOF mice have a lethal effector gene expression profile.
Fig.4 Stat3 GOF NKG2D+ CX3CR1+ CD8+ T cells in mice overexpress a suite of killer cell genes. (Masle-Farquhar, 2022)
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Reference
- Masle-Farquhar, E.; et al. STAT3 gain-of-function mutations connect leukemia with autoimmune disease by pathological NKG2Dhi CD8+ T cell dysregulation and accumulation. Immunity. 2022, 55(12): 2386-2404.
