This review discusses TCF1, which plays context-dependent roles in T cell function during autoimmunity, cancer, and chronic infection.

Glioblastoma remains a fatal tumor despite increased knowledge regarding the complex signalling pathways that drive this devastating disease. Recently, immunotherapeutic approaches have shown remarkable and durable responses in various cancers including metastatic melanoma and advanced non-small cell lung cancer. So far, it remains unclear whether these immunotherapeutics may also work against glioblastoma and other tumors residing in the central nervous system. It is well known that patients with glioblastoma suffer from profound local immunosuppression that represents the major hurdle to overcome in the context of immunotherapy. Several studies have demonstrated that this immunosuppressive phenotype is orchestrated by glioma-derived membrane-bound and soluble factors as well as the particular microenvironment within the brain. Here, we discuss the molecular and cellular pathways involved in glioblastoma-mediated inhibition of the immune system and highlight possible treatment approaches aiming at reinvigorating anti-tumor immune responses.

Glioblastoma multiforme (GBM) is one of the most deadly types of cancer. To date, the best clinical approach for treatment is based on administration of temozolomide (TMZ) in combination with radiotherapy. Much evidence suggests that the intracellular level of the alkylating enzyme O⁶-methylguanine–DNA methyltransferase (MGMT) impacts response to TMZ in GBM patients. MGMT expression is regulated by the methylation of its promoter. However, evidence indicates that this is not the only regulatory mechanism present. Here, we describe a hitherto unknown microRNA-mediated mechanism of MGMT expression regulation. We show that miR-221 and miR-222 are upregulated in GMB patients and that these paralogues target MGMT mRNA, inducing greater TMZ-mediated cell death. However, miR-221/miR-222 also increase DNA damage and, thus, chromosomal rearrangements. Indeed, miR-221 overexpression in glioma cells led to an increase in markers of DNA damage, an effect rescued by re-expression of MGMT. Thus, chronic miR-221/222-mediated MGMT downregulation may render cells unable to repair genetic damage. This, associated also to miR-221/222 oncogenic potential, may poor GBM prognosis.

The intestinal mucosa constitutes an environment of closely regulated immune cells. Dendritic cells (DC) interact with the gut microbiome and antigens and are important in maintaining gut homeostasis. Here, we investigate DC transcriptome, phenotype and function in five anatomical locations of the gut lamina propria (LP) which constitute different antigenic environments. We show that DC from distinct gut LP compartments induce distinct T cell differentiation and cytokine secretion. We also find that PD-L1⁺ DC in the duodenal LP and XCR1⁺ DC in the colonic LP comprise distinct tolerogenic DC subsets that are crucial for gut homeostasis. Mice lacking PD-L1⁺ and XCR1⁺ DC have a proinflammatory gut milieu associated with an increase in Th1/Th17 cells and a decrease in Treg cells and have exacerbated disease in the models of 5-FU-induced mucositis and DSS-induced colitis. Our findings identify PD-L1⁺ and XCR1⁺ DC as region-specific physiologic regulators of intestinal homeostasis.