John T. O'Malley

Stat3 and Stat4 Direct Development of IL-17-Secreting Th Cells

IL-17-secreting CD4+ T cells are critically involved in inflammatory immune responses. Development of these cells is promoted in vivo and in vitro by IL-23 or TGFβ1 plus IL-6. Despite growing interest in this inflammatory Th subset, little is known about the transcription factors that are required for their development. We demonstrate that Stat3 is required for programming the TGFβ1 plus IL-6 and IL-23-stimulated IL-17-secreting phenotype, as well as for RORγt expression in TGFβ1 plus IL-6-primed cells. Moreover, retroviral transduction of a constitutively active Stat3 into differentiating T cell cultures enhances IL-17 production from these cells. We further show that Stat4 is partially required for the development of IL-23-, but not TGFβ1 plus IL-6-primed IL-17-secreting cells, and is absolutely required for IL-17 production in response to IL-23 plus IL-18. The requirements for Stat3 and Stat4 in the development of these IL-17-secreting subsets reveal additional mechanisms in Th cell fate decisions during the generation of proinflammatory cell types.

TCR sequencing facilitates diagnosis and identifies mature T cells as the cell of origin in CTCL

High-throughput TCR sequencing can accurately diagnose and discriminate CTCL cells in skin. Discriminating taste for CTCL Cutaneous T cell lymphoma (CTCL) is a potentially debilitating disease, but early stages resemble rashes of less dangerous inflammatory skin diseases. Now, Kirsch et al. report that high-throughput TCR sequencing (HTS) can be used to distinguish CTCL from benign inflammatory disease by identifying T cell clones. This diagnostic was more sensitive and specific than the current standard of care and was also able to determine therapeutic response and identify early recurrence. The authors then used HTS to gain insight into CTCL pathogenesis, reporting that the malignancy derived from mature T cells that may have a specialized niche in the skin. Early diagnosis of cutaneous T cell lymphoma (CTCL) is difficult and takes on average 6 years after presentation, in part because the clinical appearance and histopathology of CTCL can resemble that of benign inflammatory skin diseases. Detection of a malignant T cell clone is critical in making the diagnosis of CTCL, but the T cell receptor γ (TCRγ) polymerase chain reaction (PCR) analysis in current clinical use detects clones in only a subset of patients. High-throughput TCR sequencing (HTS) detected T cell clones in 46 of 46 CTCL patients, was more sensitive and specific than TCRγ PCR, and successfully discriminated CTCL from benign inflammatory diseases. HTS also accurately assessed responses to therapy and facilitated diagnosis of disease recurrence. In patients with new skin lesions and no involvement of blood by flow cytometry, HTS demonstrated hematogenous spread of small numbers of malignant T cells. Analysis of CTCL TCRγ genes demonstrated that CTCL is a malignancy derived from mature T cells. There was a maximal T cell density in skin in benign inflammatory diseases that was exceeded in CTCL, suggesting that a niche of finite size may exist for benign T cells in skin. Last, immunostaining demonstrated that the malignant T cell clones in mycosis fungoides and leukemic CTCL localized to different anatomic compartments in the skin. In summary, HTS accurately diagnosed CTCL in all stages, discriminated CTCL from benign inflammatory skin diseases, and provided insights into the cell of origin and location of malignant CTCL cells in skin.

Temporal Induction Pattern of STAT4 Target Genes Defines Potential for Th1 Lineage-Specific Programming

STAT4 is a critical component in the development of inflammatory adaptive immune responses. It has been extensively characterized as a lineage-determining factor in Th1 development. However, the genetic program activated by STAT4 that results in an inflammatory cell type is not well defined. In this report, we use DNA isolated from STAT4-chromatin immunoprecipitation to perform chromatin immunoprecipitation-on-chip analysis of over 28,000 mouse gene promoters to identify STAT4 targets. We demonstrate that STAT4 binds multiple gene-sets that program distinct components of the Th1 lineage. Although many STAT4 target genes display STAT4-dependent IL-12-inducible expression, other genes displayed IL-12-induced histone modifications but lack induction, possibly due to high relative basal expression. In the subset of genes that STAT4 programs for expression in Th1 cells, IL-12-induced mRNA levels remain increased for a longer time than mRNA from genes that are not programmed. This suggests that STAT4 binding to target genes, while critical, is not the only determinant for STAT4-dependent gene programming during Th1 differentiation.

Stat4 Isoforms Differentially Regulate Inflammation and Demyelination in Experimental Allergic Encephalomyelitis

Experimental allergic encephalomyelitis (EAE) is a T cell-mediated autoimmune disease model of multiple sclerosis. Signal transducer and activator of transcription 4 (Stat4) is a transcription factor activated by IL-12 and IL-23, two cytokines known to play important roles in the pathogenesis of EAE by inducing T cells to secrete IFN-γ and IL-17, respectively. We and others have previously shown that therapeutic intervention or targeted disruption of Stat4 was effective in ameliorating EAE. Recently, a splice variant of Stat4 termed Stat4β has been characterized that lacks 44 amino acids at the C terminus of the full-length Stat4α. In this study we examined whether T cells expressing either isoform could affect the pathogenesis of EAE. We found that transgenic mice expressing Stat4β on a Stat4-deficient background develop an exacerbated EAE compared with wild-type mice following immunization with myelin oligodendrocyte glycoprotein peptide 35–55, while Stat4α transgenic mice have greatly attenuated disease. The differential development of EAE in transgenic mice correlates with increased IFN-γ and IL-17 in Stat4β-expressing cells in situ, contrasting increased IL-10 production by Stat4α-expressing cells. This study demonstrates that Stat4 isoforms differentially regulate inflammatory cytokines in association with distinct effects on the onset and severity of EAE.

STAT4 isoforms differentially regulate Th1 cytokine production and the severity of inflammatory bowel disease

STAT4, a critical regulator of inflammation in vivo, can be expressed as two alternative splice forms, a full-length STAT4α, and a STAT4β isoform lacking a C-terminal transactivation domain. Each isoform is sufficient to program Th1 development through both common and distinct subsets of target genes. However, the ability of these isoforms to mediate inflammation in vivo has not been examined. Using a model of colitis that develops following transfer of CD4+ CD45RBhigh T cells expressing either the STAT4α or STAT4β isoform into SCID mice, we determined that although both isoforms mediate inflammation and weight loss, STAT4β promotes greater colonic inflammation and tissue destruction. This correlates with STAT4 isoform-dependent expression of TNF-α and GM-CSF in vitro and in vivo, but not Th1 expression of IFN-γ or Th17 expression of IL-17, which were similar in STAT4α- and STAT4β-expressing T cells. Thus, higher expression of a subset of inflammatory cytokines from STAT4β-expressing T cells correlates with the ability of STAT4β-expressing T cells to mediate more severe inflammatory disease.

Agonist-Driven Development of CD4 + CD25 + Foxp3 + Regulatory T Cells Requires a Second Signal Mediated by Stat6

The factors that induce Foxp3 expression and regulatory T (Treg) cell development remain unknown. In this study, we investigated the role of STAT4 and STAT6 in agonist-driven generation of Ag-specific Foxp3-expressing Treg cells. Our findings indicate that fully efficient induction of Foxp3 expression and development of Ag-specific Treg cells requires the synergistic action of two signals: a TCR-mediated signal and a second signal mediated by STAT6. Indeed, by comparing the development of wild-type and STAT4- and STAT6-deficient hemagglutinin-specific T cells in the presence of hemagglutinin Ag, we found that the absence of STAT6 impaired the generation of Ag-specific CD4+CD25+Foxp3+ cells. Moreover, in transgenic mice expressing a constitutively active form of STAT6, we found that the fraction of CD4+Foxp3+ cells exceeds that of control wild-type littermates. Overall these findings support a role for the STAT6 pathway in Treg cell development and maintenance.

Staged development of long lived TCRαβ Th17 resident memory T cell population to Candida albicans after skin infection

Background: Candida albicans is a dimorphic fungus to which human subjects are exposed early in life, and by adulthood, it is part of the mycobiome of skin and other tissues. Neonatal skin lacks resident memory T (TRM) cells, but in adults the C albicans skin test is a surrogate for immunocompetence. Young adult mice raised under specific pathogen‐free conditions are naive to C albicans and have been shown recently to have an immune system resembling that of neonatal human subjects. Objective: We studied the evolution of the adaptive cutaneous immune response to Candida species. Methods: We examined both human skin T cells and the de novo and memory immune responses in a mouse model of C albicans skin infection. Results: In mice the initial IL‐17–producing cells after C albicans infection were dermal &ggr;&dgr; T cells, but by day 7, &agr;&bgr; TH17 effector T cells were predominant. By day 30, the majority of C albicans–reactive IL‐17–producing T cells were CD4 TRM cells. Intravital microscopy showed that CD4 effector T cells were recruited to the site of primary infection and were highly motile 10 days after infection. Between 30 and 90 days after infection, these CD4 T cells became increasingly sessile, acquired expression of CD69 and CD103, and localized to the papillary dermis. These established TRM cells produced IL‐17 on challenge, whereas motile migratory memory T cells did not. TRM cells rapidly clear an infectious challenge with C albicans more effectively than recirculating T cells, although both populations participate. We found that in normal human skin IL‐17–producing CD4+ TRM cells that responded to C albicans in an MHC class II–restricted fashion could be identified readily. Conclusions: These studies demonstrate that C albicans infection of skin preferentially generates CD4+ IL‐17–producing TRM cells, which mediate durable protective immunity.

STAT3/5-Dependent IL9 Overexpression Contributes to Neoplastic Cell Survival in Mycosis Fungoides.

Purpose: Sustained inflammation is a key feature of mycosis fungoides (MF), the most common form of cutaneous T-cell lymphoma (CTCL). Resident IL9–producing T cells have been found in skin infections and certain inflammatory skin diseases, but their role in MF is currently unknown. Experimental Design: We analyzed lesional skin from patients with MF for the expression of IL9 and its regulators. To determine which cells were producing IL9, high-throughput sequencing was used to identify malignant clones and Vb-specific antibodies were employed to visualize malignant cells in histologic preparations. To explore the mechanism of IL9 secretion, we knocked down STAT3/5 and IRF4 by siRNA transfection in CTCL cell lines receiving psoralen+UVA (PUVA) ± anti-IL9 antibody. To further examine the role of IL9 in tumor development, the EL-4 T-cell lymphoma model was used in C57BL/6 mice. Results: Malignant and reactive T cells produce IL9 in lesional skin. Expression of the Th9 transcription factor IRF4 in malignant cells was heterogeneous, whereas reactive T cells expressed it uniformly. PUVA or UVB phototherapy diminished the frequencies of IL9- and IL9r-positive cells, as well as STAT3/5a and IRF4 expression in lesional skin. IL9 production was regulated by STAT3/5 and silencing of STAT5 or blockade of IL9 with neutralizing antibodies potentiated cell death after PUVA treatment in vitro. IL9-depleted mice exhibited a reduction of tumor growth, higher frequencies of regulatory T cells, and activated CD4 and CD8 T lymphocytes. Conclusions: Our results suggest that IL9 and its regulators are promising new targets for therapy development in mycosis fungoides. Clin Cancer Res; 22(13); 3328–39. ©2016 AACR.

CD30+ Lymphoproliferative Disorders of the Skin

Primary cutaneous CD30+ lymphoproliferative disorders encompass lymphomatoid papulosis (LyP), primary cutaneous anaplastic large cell lymphoma (pcALCL), and indeterminate cases. LyP is a benign disorder characterized by recurrent crops of red or violaceous papulonodules. Patients with LyP are at an increased risk of a secondary malignancy. pcALCL is characterized by a solitary red to violaceous nodule or tumor larger than 20 mm. LyP is benign, is limited to the skin, and self-resolves, with a 5-year survival rate of 100%; pcALCL is limited to the skin and responsive to directed therapies, with a 5-year survival rate of over 95%. Aggressive chemotherapeutic regimens should be avoided.

Squamous Cell Carcinoma (Marjolin's Ulcer) Arising in a Sacral Decubitus Ulcer Resulting in Humoral Hypercalcemia of Malignancy

Long-standing burns, fissures, and ulcers that undergo malignant transformation into a variety of malignancies, including squamous cell carcinoma, is commonly referred to as a Marjolins ulcer. It is well recognized that squamous cell carcinomas of the lung and esophagus can cause humoral hypercalcemia of malignancy secondary to paraneoplastic secretion of parathyroid hormone-related peptide. However, it is extremely rare for a squamous cell carcinoma developing in a sacral decubitus ulcer to cause humoral hypercalcemia of malignancy. We describe the first case of a patient found to have elevated serum levels of parathyroid hormone related peptide related to his Marjolins ulcer. A 45-year-old African American man with T6 paraplegia and a sacral decubitus ulcer present for 20 years was admitted for hypercalcemia of unclear etiology. He was subsequently found to have elevated parathyroid hormone related peptide and an excisional biopsy from the ulcer showed invasive squamous cell carcinoma suggestive of humoral hypercalcemia of malignancy. The patient ultimately succumbed to sepsis while receiving chemotherapy for his metastatic squamous cell carcinoma. Humoral hypercalcemia of malignancy is a rare and likely underrecognized complication that can occur in a Marjolins ulcer.