NF-κB subunits RelA and c-Rel selectively control CD4+ T cell function in multiple sclerosis and cancer.

The outcome of cancer and autoimmunity is often dictated by the effector functions of CD4+ conventional T cells (Tconv). Although activation of the NF-κB signaling pathway has long been implicated in Tconv biology, the cell-autonomous roles of the separate NF-κB transcription-factor subunits are unknown. Here, we dissected the contributions of the canonical NF-κB subunits RelA and c-Rel to Tconv function. RelA, rather than c-Rel, regulated Tconv activation and cytokine production at steady-state and was required for polarization toward the TH17 lineage in vitro. Accordingly, RelA-deficient mice were fully protected against neuroinflammation in a model of multiple sclerosis due to defective transition to a pathogenic TH17 gene-expression program. Conversely, Tconv-restricted ablation of c-Rel impaired their function in the microenvironment of transplanted tumors, resulting in enhanced cancer burden. Moreover, Tconv required c-Rel for the response to PD-1-blockade therapy. Our data reveal distinct roles for canonical NF-κB subunits in different disease contexts, paving the way for subunit-targeted immunotherapies.

Xevinapant combined with pembrolizumab in patients with advanced, pretreated colorectal and pancreatic cancer: results of the phase 1b/2 CATRIPCA trial.

PURPOSE: Xevinapant is an orally available inhibitor of apoptosis proteins (IAP) inhibitor. Preclinical data suggest that IAP antagonism may synergize with immune checkpoint blockers (ICB) by modulating the NF-KB pathway in immune cells. PATIENTS AND METHODS: Adult patients (pts) with non MSI-H advanced/metastatic PDAC or CRC were enrolled in this phase 1b/2 and received pembrolizumab 200mg q3w, IV and ascending doses of oral xevinapant (100, 150 and 200mg daily for 14 days on/7 days off). Dose escalation followed a 3+3 design with a 21-day dose-limiting toxicity (DLT) evaluation period. Following the determination of the recommended phase II dose (RP2D), 14 patients with PDAC and 14 patients with CRC were enrolled in expansion cohorts to assess preliminary efficacy. RESULTS: Forty-one pts (26 males) with a median age of 64 years were enrolled: 13 in the dose escalation and 28 in the two expansion cohorts. No DLT was observed during dose-escalation. The RP2D was identified as xevinapant 200mg/d + pembrolizumab 200mg q3w. The most common adverse events (AE) were fatigue (37%), gastrointestinal AE (decreased appetite in 37%, nausea in 24%, stomatitis in 12 % and diarrhea and vomiting in 10% each), and cutaneous AE (pruritus, dry skin and rash seen in 20, 15 and 15% of patients respectively). The best overall response according to RECIST1.1 was partial response (PR, confirmed) in one (3%) , stable disease (SD) in four (10%) and progressive disease in 35 (88%). CONCLUSIONS: Xevinapant combined with pembrolizumab was well tolerated with no unexpected adverse events. However, anti-tumor activity was low.

The NF-κB RelA transcription factor is not required for CD8+ T-cell function in acute viral infection and cancer.

CD8+ T cells are critical mediators of pathogen clearance and anti-tumor immunity. Although signaling pathways leading to the activation of NF-κB transcription factors have crucial functions in the regulation of immune responses, the CD8+ T cell-autonomous roles of the different NF-κB subunits, are still unresolved. Here, we investigated the function of the ubiquitously expressed transcription factor RelA in CD8+ T-cell biology using a novel mouse model and gene-edited human cells. We found that CD8+ T cell-specific ablation of RelA markedly altered the transcriptome of ex vivo stimulated cells, but maintained the proliferative capacity of both mouse and human cells. In contrast, in vivo experiments showed that RelA deficiency did not affect the CD8+ T-cell response to acute viral infection or transplanted tumors. Our data suggest that in CD8+ T cells, RelA is dispensable for their protective activity in pathological contexts.

A T cell-intrinsic function for NF-κB RelB in experimental autoimmune encephalomyelitis.

NF-kappaB (NF-κB) is a family of transcription factors with pleiotropic functions in immune responses. The alternative NF-κB pathway that leads to the activation of RelB and NF-κB2, was previously associated with the activation and function of T cells, though the exact contribution of these NF-κB subunits remains unclear. Here, using mice carrying conditional ablation of RelB in T cells, we evaluated its role in the development of conventional CD4+ T (Tconv) cells and their function in autoimmune diseases. RelB was largely dispensable for Tconv cell homeostasis, activation and proliferation, and for their polarization toward different flavors of Thelper cells in vitro. Moreover, ablation of RelB had no impact on the capacity of Tconv cells to induce autoimmune colitis. Conversely, clinical severity of experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis (MS) was significantly reduced in mice with RelB-deficient T cells. This was associated with impaired expression of granulocyte-macrophage colony-stimulating factor (GM-CSF) specifically in the central nervous system. Our data reveal a discrete role for RelB in the pathogenic function of Tconv cells during EAE, and highlight this transcription factor as a putative therapeutic target in MS.