Saga of monokines in shaping tumour-immune microenvironment: Origin to execution

Cancer development and progression occurs in concert with alterations in the surrounding stroma. Cancer cells can functionally sculpt their microenvironment through the secretion of various cytokines, chemokines, and other factors. This results in a reprogramming of the surrounding cells, enabling them to play a determinative role in tumor survival and progression. Immune cells are important constituents of the tumor stroma and critically take part in this process. Growing evidence suggests that the innate immune cells (macrophages, neutrophils, dendritic cells, innate lymphoid cells, myeloid-derived suppressor cells, and NK cells) as well as adaptive immune cells (T cells and B cells) contribute to tumor progression when present in the tumor microenvironment (TME). Crosstalk between cancer cells and the proximal immune cells ultimately results in an environment that fosters tumor growth and metastasis. Understanding the nature of this dialog will allow for improved therapeutics that simultaneously target multiple components of the TME, increasing the likelihood of favorable patient outcomes.

We describe de novo generation of IL-17-producing T cells from naive CD4 T cells, induced in cocultures of naive CD4 T cells and naturally occurring CD4+ CD25+ T cells (Treg) in the presence of TLR3, TLR4, or TLR9 stimuli. Treg can be substituted by TGFbeta1, which, together with the proinflammatory cytokine IL-6, supports the differentiation of IL-17-producing T cells, a process that is amplified by IL-1beta and TNFalpha. We could not detect a role for IL-23 in the differentiation of IL-17-producing T cells but confirmed its importance for their survival and expansion. Transcription factors GATA-3 and T-bet, as well as its target Hlx, are absent in IL-17-producing T cells, and they do not express the negative regulator for TGFbeta signaling, Smad7. Our data indicate that, in the presence of IL-6, TGFbeta1 subverts Th1 and Th2 differentiation for the generation of IL-17-producing T cells.

Type I interferons (IFNs) activate intracellular antimicrobial programmes and influence the development of innate and adaptive immune responses. Canonical type I IFN signalling activates the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway, leading to transcription of IFN-stimulated genes (ISGs). Host, pathogen and environmental factors regulate the responses of cells to this signalling pathway and thus calibrate host defences while limiting tissue damage and preventing autoimmunity. Here, we summarize the signalling and epigenetic mechanisms that regulate type I IFN-induced STAT activation and ISG transcription and translation. These regulatory mechanisms determine the biological outcomes of type I IFN responses and whether pathogens are cleared effectively or chronic infection or autoimmune disease ensues.