The Role of Tumor Microenvironment in the Pathogenesis of Sézary Syndrome

STAT5a and SH2B3 novel mutations display malignancy roles in a triple-negative primary myelofibrosis patient

Primary myelofibrosis (PMF) patients frequently have JAK2 (V617F), CALR (exon 9), or MPL (W515 or exon 10) strong driver gene mutation, which triggers abnormal activation of the JAK2-STATs signaling pathway that plays a complex role in the occurrence of PMF. However, about 10-15% of PMF patients have no above typical mutations in these strong driver genes, known as being "triple-negative", which are associated with poor prognosis. In this paper, we reported a unique secondary acute myeloid leukemia (sAML) case transformed from triple-negative PMF combined with lung cancer and erythroderma occurrence at the same time, which has not been reported so far. Through whole blood exome sequencing, four novel noncanonical mutations were detected in key regulatory genes SH2B3 (Q748 and S710) and STAT5a (C350 and K354). Meanwhile, STAT5a-S710 and SH2B3-K354 noncanonical mutations gained strong malignant biofunction on promoting cell growth and tumorigenesis by accelerating the G1/S transition. In the mechanistic study, these pernicious phenotypes driven by noncanonical mutations might be initial PMF by activating p-STAT5a/c-Myc/CyclinD1 and p-STAT3/p-AKT/p-ERK1/2 signaling axes. Therefore, our study explored the deleterious roles of novel noncanonical mutations in STAT5a and SH2B3, which may serve as susceptibility genes and display the oncogenic biofunction in the progression of PMF to acute myeloid leukemia-M2a (AML-M2a).

Spatially Guided and Single Cell Tools to Map the Microenvironment in Cutaneous T-Cell Lymphoma

Mycosis fungoides (MF) and Sézary syndrome (SS) are two closely related clinical variants of cutaneous T-cell lymphomas (CTCL). Previously demonstrated large patient-to-patient and intra-patient disease heterogeneity underpins the importance of personalized medicine in CTCL. Advanced stages of CTCL are characterized by dismal prognosis, and the early identification of patients who will progress remains a clinical unmet need. While the exact molecular events underlying disease progression are poorly resolved, the tumor microenvironment (TME) has emerged as an important driver. In particular, the Th1-to-Th2 shift in the immune response is now commonly identified across advanced-stage CTCL patients. Herein, we summarize the role of the TME in CTCL evolution and the latest studies in deciphering inter- and intra-patient heterogeneity. We introduce spatially resolved omics as a promising technology to advance immune-oncology efforts in CTCL. We propose the combined implementation of spatially guided and single-cell omics technologies in paired skin and blood samples. Such an approach will mediate in-depth profiling of phenotypic and molecular changes in reactive immune subpopulations and malignant T cells preceding the Th1-to-Th2 shift and reveal mechanisms underlying disease progression from skin-limited to systemic disease that collectively will lead to the discovery of novel biomarkers to improve patient prognostication and the design of personalized treatment strategies.

Imbalanced IL-1B and IL-18 Expression in Sézary Syndrome

Sézary syndrome (SS) is a rare and aggressive type of cutaneous T-cell lymphoma, with an abnormal inflammatory response in affected skin. The cytokines IL-1B and IL-18, as key signaling molecules in the immune system, are produced in an inactive form and cleave to the active form by inflammasomes. In this study, we assessed the skin, serum, peripheral mononuclear blood cell (PBMC) and lymph-node samples of SS patients and control groups (healthy donors (HDs) and idiopathic erythroderma (IE) nodes) to investigate the inflammatory markers IL-1B and IL-18 at the protein and transcript expression levels, as potential markers of inflammasome activation. Our findings showed increased IL-1B and decreased IL-18 protein expression in the epidermis of SS patients; however, in the dermis layer, we detected increased IL-18 protein expression. In the lymph nodes of SS patients at advanced stages of the disease (N2/N3), we also detected an enhancement of IL-18 and a downregulation of IL-1B at the protein level. Moreover, the transcriptomic analysis of the SS and IE nodes confirmed the decreased expression of IL1B and NLRP3, whereas the pathway analysis indicated a further downregulation of IL1B-associated genes. Overall, the present findings showed compartmentalized expressions of IL-1B and IL-18 and provided the first evidence of their imbalance in patients with Sézary syndrome.

T Cell Extracellular Traps: Tipping the Balance Between Skin Health and Disease

The role of extracellular traps (ETs) in the innate immune response against pathogens is well established. ETs were first identified in neutrophils and have since been identified in several other immune cells. Although the mechanistic details are not yet fully understood, recent reports have described antigen-specific T cells producing T cell extracellular traps (TETs). Depending on their location within the cutaneous environment, TETs may be beneficial to the host by their ability to limit the spread of pathogens and provide protection against damage to body tissues, and promote early wound healing and degradation of inflammatory mediators, leading to the resolution of inflammatory responses within the skin. However, ETs have also been associated with worse disease outcomes. Here, we consider host-microbe ET interactions by highlighting how cutaneous T cell-derived ETs aid in orchestrating host immune responses against Cutibacterium acnes (C. acnes), a commensal skin bacterium that contributes to skin health, but is also associated with acne vulgaris and surgical infections following joint-replacement procedures. Insights on the role of the skin microbes in regulating T cell ET formation have broad implications not only in novel probiotic design for acne treatment, but also in the treatment for other chronic inflammatory skin disorders and autoimmune diseases.