Lastly, IL-4R-targeted liposomal doxorubicin inhibited tumor growth more than chemotherapy in an orthotopic glioma xenograft model [144]

Lastly, IL-4R-targeted liposomal doxorubicin inhibited tumor growth more than chemotherapy in an orthotopic glioma xenograft model [144]. type 2 immune response. Similar to other ILCs, ILC2s are MRT-83 rapidly activated by signals deriving from tissue and/or other tissue-resident immune cells. The biologic activity of ILCs needs to be tightly regulated in order to prevent them from contributing to severe inflammation and damage in several organs. Indeed, ILC2s display both enhancing and regulatory roles in several pathophysiological conditions, including tumors. In this review, we summarize the actual knowledge about ILC2s ability to induce or impair a protective immune response, their pro- or antitumor activity in murine models, human (children and adults) pathologies and the potential strategies to improve cancer immunotherapy by exploiting the features of ILC2s. In a breast cancer model, it has been shown that IL-33 treatment increased tumor growth and metastases [75]. Mice from this model displayed increased proportion of ILC2s and MDSCs (CD11b+CD11c+Gr1+Ly6G?Ly6C+) in the spleen and TME, as well as upregulated IL-13 serum level. Accordingly, ST2 (IL33R) KO mice had reduced levels of MDSC [75]. In this model, IL-13 derived from tumor-activated ILC2s was suggested to directly induce MDSC with suppressive activity on antitumor T cell response, as confirmed by MDSC reduction upon partial ILC2 depletion. Recently, the ILC2-MDSC immune-regulatory axis has been established in human bladder and prostate cancers, as well as in acute promyelocytic leukemia (APL) [32,86]. It has been shown that this protumor function in APL is usually mediated MRT-83 by high levels of PGD2 and B7-H6, able to expand and activate ILC2s [32]. The over-production of IL 13 by ILC2s and MDSCs, in turn, induced a strong immunosuppression mainly of antitumor adaptive immunity. Additional evidence of this suppressive axis includes: i. the proportions of ILC2s and MDSC in the urine of patients with bladder cancer and receiving intravesical Bacillus CalmetteCGuerin (BCG) therapy were negatively correlated with patients outcome, which was also the case in murine models of prostate tumor; ii. ILC2s in prostate and bladder murine cancer secrete IL-13, whose receptor (IL-13R1) is highly expressed on monocytes and MDSCs; iii. IL-13 triggering induces markers of suppressive function in monocytic cells (Arg1, iNOS, C/EBP, IL1-RA). In human gastric and lung tumors a correlation between circulating ILC2 and MDSC were also observed, suggesting an active ILC2-MDSC suppressive axis in several tumor isotypes [81,86,88]. Some reports indicate that ILC2s favor the Tregs compartment, which impairs antitumor T cell responses and is usually associated with poor prognosis [89]. AREG, produced by ILC2s, induces Tregs through TGF- production [45,90]. ILC2s also expand Tregs via an OX40L and ICOSL-dependent mechanisms in murine models of allergen exposure and helminth infection [64,67]. IL-33-treated tumor-bearing mice also showed an elevated proportion of CD4+FoxP3+ Tregs [90], due to the direct effect of IL-33 on Tregs expressing ST2. In addition to the above-mentioned OX40L-dependent ILC2-mediated Tregs expansion, even the increased MDSCs may in turn attract and induce Tregs proliferation [91,92]. On the whole, ILC2s may directly or indirectly favor the involvement of Tregs, even though this must be formally shown inside TME. Conversely, ILC2s themselves can be the target of regulatory cells or cytokines: for instance we have recently shown that the proliferation, cytokines production and CD154 expression of human ILC2s Lif are inhibited by CD4+CD25high Foxp3+ MRT-83 Tregs, while TGF- reduces CD154 expression on ILC2 stimulated with IL-25/IL-33 [38]. A subset of hyporesponsive IL-10-producing ILC2s expressing TIGIT and PD1 were found in the lung of allergic severe inflammation [69]. Transcriptome analysis revealed similarities of this subset with exhausted CD8+ T cells observed during chronic viral infections; for this reason they have been designed exhausted-like ILC2s [47,69]. Thus, it cannot be excluded that immunosuppressive TME, as other chronic inflammatory tissue, may promote the proliferation of ILC2s subsets with regulatory activity at least in some kind of tumors [68,70]. However, the role of the.