Keratinocyte-derived cytokine TSLP promotes growth and metastasis of melanoma by regulating the tumor-associated immune microenvironment.

Malignant melanoma is a major public health issue displaying frequent resistance to targeted therapy and immunotherapy. A major challenge lies in better understanding how melanoma cells evade immune elimination and how tumor growth and metastasis is facilitated by the tumor microenvironment. Here, we show that expression of the cytokine thymic stromal lymphopoietin (TSLP) by epidermal keratinocytes is induced by cutaneous melanoma in both mice and humans. Using genetically engineered models of melanoma and tumor cell grafting combined with TSLP-KO or overexpression, we defined a crosstalk between melanoma cells, keratinocytes, and immune cells in establishing a tumor-promoting microenvironment. Keratinocyte-derived TSLP is induced by signals derived from melanoma cells and subsequently acts via immune cells to promote melanoma progression and metastasis. Furthermore, we show that TSLP signals through TSLP receptor-expressing (TSLPR-expressing) DCs to play an unrecognized role in promoting GATA3+ Tregs expressing a gene signature including ST2, CCR8, ICOS, PD-1, CTLA-4, and OX40 and exhibiting a potent suppressive activity on CD8+ T cell proliferation and IFN-γ production. An analogous population of GATA3-expressing Tregs was also identified in human melanoma tumors. Our study provides insights into the role of TSLP in programming a protumoral immune microenvironment in cutaneous melanoma.

Context-dependent function of TSLP and IL-1ß in skin allergic sensitization and atopic march.

Atopic diseases, including atopic dermatitis (AD) and asthma, affect a large proportion of the population, with increasing prevalence worldwide. AD often precedes the development of asthma, known as the atopic march. Allergen sensitization developed through the barrier-defective skin of AD has been recognized to be a critical step leading to asthma, in which thymic stromal lymphopoietin (TSLP) was previously shown to be critical. In this study, using a laser-assistant microporation system to disrupt targeted skin layers for generating micropores at a precise anatomic depth of mouse skin, we model allergen exposure superficially or deeply in the skin, leading to epicutaneous sensitization or dermacutaneous sensitization that is associated with a different cytokine microenvironment. Our work shows a differential requirement for TSLP in these two contexts, and identifies an important function for IL-1ß, which is independent of TSLP, in promoting allergen sensitization and subsequent allergic asthma.

GOLT1B Activation in Hepatitis C Virus-Infected Hepatocytes Links ER Trafficking and Viral Replication.

Chronic hepatitis C carries a high risk of development of hepatocellular carcinoma (HCC), triggered by both direct and indirect effects of the virus. We examined cell-autonomous alterations in gene expression profiles associated with hepatitis C viral presence. Highly sensitive single molecule fluorescent in situ hybridization applied to frozen tissue sections of a hepatitis C patient allowed the delineation of clusters of infected hepatocytes. Laser microdissection followed by RNAseq analysis of hepatitis C virus (HCV)-positive and -negative regions from the tumoral and non-tumoral tissues from the same patient revealed HCV-related deregulation of expression of genes in the tumor and in the non-tumoral tissue. However, there was little overlap between both gene sets. Our interest in alterations that increase the probability of tumorigenesis prompted the examination of genes whose expression was increased by the virus in the non-transformed cells and whose level remained high in the tumor. This strategy led to the identification of a novel HCV target gene: GOLT1B, which encodes a protein involved in ER-Golgi trafficking. We further show that GOLT1B expression is induced during the unfolded protein response, that its presence is essential for efficient viral replication, and that its expression is correlated with poor outcome in HCC.