Th17 cytokine differentiation and loss of plasticity after SOCS1 inactivation in a cutaneous T-cell lymphoma

Abstract

We propose that deregulated T-helper-cell (Th) signaling underlies evolving Th17 cytokine expression seen during progression of cutaneous T-cell lymphoma (CTCL). Accordingly, we developed a lymphoma progression model comprising cell lines established at indolent (MAC-1) and aggressive (MAC-2A) CTCL stages. We discovered activating JAK3 (V722I) mutations present at indolent disease, reinforced in aggressive disease by novel compound heterozygous SOCS1 (G78R/D105N) JAK-binding domain inactivating mutations. Though isogenic, indolent and aggressive-stage cell lines had diverged phenotypically, the latter expressing multiple Th17 related cytokines, the former a narrower profile. Importantly, indolent stage cells remained poised for Th17 cytokine expression, readily inducible by treatment with IL-2 - a cytokine which mitigates Th17 differentiation in mice. In indolent stage cells JAK3 expression was boosted by IL-2 treatment. Th17 conversion of MAC-1 cells by IL-2 was blocked by pharmacological inhibition of JAK3 or STAT5, implicating IL2RG - JAK3 – STAT5 signaling in plasticity responses. Like IL-2 treatment, SOCS1 knockdown drove indolent stage cells to mimic key aggressive stage properties, notably IL17F upregulation. Co-immunoprecipitation experiments showed that SOCS1 mutations abolished JAK3 binding, revealing a key role for SOCS1 in regulating JAK3/STAT5 signaling. Collectively, our results show how JAK/STAT pathway mutations contribute to disease progression in CTCL cells by potentiating inflammatory cytokine signaling, widening the potential therapeutic target range for this intractable entity. MAC-1/2A cells also provide a candidate human Th17 laboratory model for identifying potentally actionable CTCL markers or targets and testing their druggability in vitro.

The NKL-code for innate lymphoid cells reveals deregulated expression of NKL homeobox genes HHEX and HLX in anaplastic large cell lymphoma (ALCL)

“…They belong to the TH17 gene signature [ 90 ], supporting the indicated character of ALCL. Breast implant-associated (BIA)-ALCL, CTLC and ALCL are closely related malignancies and consistently express several aspects of ILC3/TH17 cells aberrantly [ 28 , 69 , 91 ]. In CTCL, IL17F expression is driven via the IL2-JAK3-STAT5 pathway reportedly activated by a particular mutation of SOCS1 [ 69 ].…”

“…Breast implant-associated (BIA)-ALCL, CTLC and ALCL are closely related malignancies and consistently express several aspects of ILC3/TH17 cells aberrantly [ 28 , 69 , 91 ]. In CTCL, IL17F expression is driven via the IL2-JAK3-STAT5 pathway reportedly activated by a particular mutation of SOCS1 [ 69 ]. However, our data revealed absence of SOCS1 mutations in ALCL cell lines, excluding this mode of IL17F activation in ALCL.…”

“…Accordingly, ELISA analysis detected high amounts of about 30 ng/ml IL17F protein in the supernatant of SUP-M2 while SU-DHL-1 tested negative (Supplementary Figure 11A). In cutaneous T-cell lymphoma (CTCL) cell lines mutated SOCS1 boosted IL17F expression via the IL2-JAK3-STAT5 pathway [69]. However, LL-100 transcriptome data discounted mutations in JAK3, SOCS1 and STAT5, and showed no conspicuous expression levels of these genes in SUP-M2.…”

Malignant inflammation in cutaneous T‐cell lymphoma—a hostile takeover

“…High expression of IL-17A has, accordingly, been associated with neutrophilic infiltration into CTCL lesions; whether it is also the case for IL-17F remains to be investigated [70]. Malignant T cells derived from some patients have the capacity to express IL-17A and/or IL-17F via a Jak3/Stat3/Stat5-dependent mechanism but do not express the Th17-linage transcription factor, RORc, or display a characteristic Th17-phenotype [62, 71, 76, 129]. Therefore, expression of IL-17A and IL-17F by the malignant T cells is probably not reflective of Th17 origin, or acquisition of a full-fledged Th17 phenotype, but rather a consequence of dysregulated signaling.…”

Bexarotene Reduces Production of CCL22 From Tumor-Associated Macrophages in Cutaneous T-Cell Lymphoma

“…Since CTCL is a rare disease, and since established criteria for staging and response evaluation for CTCL are limited, few prospective clinical trials for advanced CTCL have been reported, and guidelines for the treatment of CTCL have yet to be established (2, 3). Instead, several preclinical studies have been used to determine the optimal therapy for CTCL (4–6). Among them, Shono et al reported that mycosis fungoides (MF), the most common subtype of CTCL, shows high expression of CCR4 on the cell surface, correlating with poor prognosis of MF (4).…”