Melanoma Cell-Intrinsic PD-1 Receptor Functions Promote Tumor Growth.

Therapeutic antibodies targeting programmed cell death 1 (PD-1) activate tumor-specific immunity and have shown remarkable efficacy in the treatment of melanoma. Yet, little is known about tumor cell-intrinsic PD-1 pathway effects. Here, we show that murine and human melanomas contain PD-1-expressing cancer subpopulations and demonstrate that melanoma cell-intrinsic PD-1 promotes tumorigenesis, even in mice lacking adaptive immunity. PD-1 inhibition on melanoma cells by RNAi, blocking antibodies, or mutagenesis of melanoma-PD-1 signaling motifs suppresses tumor growth in immunocompetent, immunocompromised, and PD-1-deficient tumor graft recipient mice. Conversely, melanoma-specific PD-1 overexpression enhances tumorigenicity, as does engagement of melanoma-PD-1 by its ligand, PD-L1, whereas melanoma-PD-L1 inhibition or knockout of host-PD-L1 attenuate growth of PD-1-positive melanomas. Mechanistically, the melanoma-PD-1 receptor modulates downstream effectors of mTOR signaling. Our results identify melanoma cell-intrinsic functions of the PD-1:PD-L1 axis in tumor growth and suggest that blocking melanoma-PD-1 might contribute to the striking clinical efficacy of anti-PD-1 therapy.

Elevated levels of the antimicrobial peptide LL-37 in hidradenitis suppurativa are associated with a Th1/Th17 immune response.

Hidradenitis suppurativa (HS) is an inflammatory skin disease with poorly understood immunopathogenic mechanisms. LL-37 is an antimicrobial peptide, which is transcribed from the CAMP (cathelicidin antimicrobial peptide) gene. Previous reports showed upregulated levels of CAMP and LL-37 in HS lesions, and therefore, the aim of this study was to compare levels of LL-37 in HS to other inflammatory skin diseases and to establish immunomodulatory functions of LL-37 in HS. We confirm an upregulation of the LL-37 peptide in lesional HS skin with comparable levels as in psoriasis patients and are able to positively correlate the presence of LL-37 in HS with the presence of T cells, macrophages, neutrophils, IFN-γ, IL-17, IL-23, TNF-α, IL-32 and IL-1ß. Mechanistically, LL-37 boosts the proliferation of unspecifically activated CD4+ T cells via an increased calcium signalling independent of antigen-presenting cells. Targeting LL-37 may therefore represent a new therapeutic option for the treatment of this recalcitrant disease, but it has to be kept in mind that LL-37 also has an antimicrobial function.

Association of Hidradenitis Suppurativa With T Helper 1/T Helper 17 Phenotypes: A Semantic Map Analysis.

Importance: In spite of progress in understanding the mechanisms underlying hidradenitis suppurativa (HS) as an inflammatory skin disease, there is still a demand for an overview on immunopathogenesis of HS. Objective: To demonstrate the importance of the type 1/type 17 immune response in lesional HS skin by drawing a semantic connectivity map. Design, Setting, and Participants: Single-center case series of 24 patients with HS. Association of HS with T helper 1/T helper 17 (TH1/TH17) phenotype was assessed using semantic map analysis. Main Outcomes and Measures: Association of HS with TH1/TH17 phenotype. Results: The analysis was performed on 24 lesional HS biopsy samples from untreated patients with HS (16 [67%] female; median age, 36.5 years [range, 21-51 years]) with a mean (SD) Hurley stage of 2.29 (0.62) and 9 punch biopsy samples from healthy controls (6 [67%] female; median age, 43 years [range, 23-66 years]). The map shows a clustering of all TH1/TH17-associated cytokines (interleukin 17 [IL-17], interferon γ, IL-12, IL-23, IL-32, IL-1ß, tumor necrosis factor) around overall lesional inflammation. Tumor necrosis factor, IL-12, and IL-17 are even directly connected via interferon γ. In contrast, IL-13, a TH2-associated cytokine, was inversely correlated with the presence of TH1/TH17-associated cytokines, further highlighting the importance of the TH1/TH17 cytokines in HS pathogenesis. Conclusions and Relevance: These findings suggest that HS may be a TH1/TH17-driven inflammatory skin disease.