No abstract

Evidence has gathered that CD28 costimulation facilitates T cell activation by potentiating TCR intrinsic-signaling. However, the underlying molecular mechanism is largely unknown. Here we show that, by enhancing T cell/APC close contacts, CD28 facilitates TCR signal transduction. Moreover, the signal supplied by CD28 does not lead to increased Zap-70 and Lat phosphorylation, but amplifies PLCgamma1 activation and Ca(2+) response. We provide evidence that the PTK Itk controls the latter function. Our data suggest that CD28 binding to B7 contributes to setting the level of TCR-induced phosphorylated Lat for recruiting signaling complexes, whereas the CD28 signal boosts multiple pathways by facilitating PLCgamma1 activation. These results should provide a conceptual framework for understanding quantitative and qualitative aspects of CD28-mediated costimulation.

IL-23 is a heterodimeric cytokine composed of a unique p19 subunit and a common p40 subunit is shared with IL-12. IL-23 promotes the inflammatory response by inducing the expansion of CD4+ cells producing IL-17. The regulation of p19 gene expression has been less studied than that of p40 subunit expression, which in macrophages is well known to be dependent on NF-κB. To clarify the role of NF-κB in expression of the p19 gene, we analyzed mRNA levels in NF-κB-deficient macrophages. As reported to occur in dendritic cells, p19 expression was dramatically reduced in c-rel-deficient macrophages. Moreover, we found that p19 expression was halved in rela-deficient macrophages, but it was enhanced in p52-deficient macrophages. The p19 promoter contains three putative κB sites, located at nt −642 to −632 (κB–642), nt −513 to −503 (κB–513), and nt −105 to −96 (κB–105), between the transcription start site and −937 bp upstream in the p19 promoter region. Although EMSA analysis indicated that both κB–105 and κB–642, but not κB–513, bound to NF-κB in vitro, luciferase-based reporter assays showed that the most proximal κB site, κB–105, was uniquely indispensable to the induction of p19 transcription. Chromatin immunoprecipitation demonstrated in vivo association of RelA, c-Rel, and p50 with κB–105 of the p19 promoter. These results provide the evidence that the association of RelA and c-Rel with the proximal κB site in the p19 promoter is required to induce of p19 expression.

Inhibition of immune checkpoint molecules, PD‐1 and CTLA4, has been shown to be a promising cancer treatment. PD‐1 and CTLA4 inhibit TCR and co‐stimulatory signals. The third T cell activation signal represents the signals from the cytokine receptors. The cytokine interferon‐γ (IFNγ) plays an important role in anti‐tumor immunity by activating cytotoxic T cells (CTLs). Most cytokines use the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway, and the suppressors of cytokine signaling (SOCS) family of proteins are major negative regulators of the JAK/STAT pathway. Among SOCS proteins, CIS, SOCS1, and SOCS3 proteins can be considered the third immunocheckpoint molecules since they regulate cytokine signals that control the polarization of CD4+ T cells and the maturation of CD8+ T cells. This review summarizes recent progress on CIS, SOCS1, and SOCS3 in terms of their anti‐tumor immunity and potential applications.

Recent studies have shown that stem cell memory T (T SCM ) cell-like properties are important for successful adoptive immunotherapy by the chimeric antigen receptor-engineered-T (CAR-T) cells. We previously reported that both human and murineactivated T cells are converted into stem cell memory-like T (iT SCM ) cells by coculture with stromal OP9 cells expressing the NOTCH ligand. However, the mechanism of NOTCHmediated iT SCM reprogramming remains to be elucidated. Here, we report that the NOTCH/OP9 system efficiently converted conventional human CAR-T cells into T SCM -like CAR-T, "CAR-iT SCM " cells, and that mitochondrial metabolic reprogramming played a key role in this conversion. NOTCH signaling promoted mitochondrial biogenesis and fatty acid synthesis during iT SCM formation, which are essential for the properties of iT SCM cells. Forkhead box M1 (FOXM1) was identified as a downstream target of NOTCH, which was responsible for these metabolic changes and the subsequent iT SCM differentiation. Like NOTCH-induced CAR-iT SCM cells, FOXM1-induced CAR-iT SCM cells possessed superior antitumor potential compared with conventional CAR-T cells. We propose that NOTCHor FOXM1-driven CAR-iT SCM formation is an effective strategy for improving cancer immunotherapy.Significance: Manipulation of signaling and metabolic pathways important for directing production of stem cell memory-like T cells may enable development of improved CAR-T cells.