Signaling by the phosphatase MKP-1 in dendritic cells imprints distinct effector and regulatory T cell fates.

Naive T cells respond to antigens by differentiating into effector and regulatory lineages. Whereas the roles of T cell-intrinsic pathways have been extensively studied, how T cell lineage choices are controlled by innate immune signals remains elusive. Here we report that dendritic cell (DC)-expressed phosphatase MKP-1, a negative regulator of the MAP kinases, programmed reciprocal T helper 1 (Th1) and Th17 cell differentiation by modulating IL-12-STAT4 and IL-6-STAT3 axes and cytokine receptor expression at the DC-T cell interface. MKP-1 was regulated by innate recognition signals and its deficiency disrupted antimicrobial responses and promoted T cell-mediated inflammation. Moreover, MKP-1 inhibited induction of regulatory T cells by downregulating TGF-ß2 production from DCs. Our findings identify a regulatory circuit linking MKP-1 signaling in DCs, production of polarizing cytokines, and integration of DC-derived signals in responding T cells, that bridges innate and adaptive immunity to coordinate protective immunity and immunopathology.

Gfi1 controls the formation of effector CD8 T cells during chronic infection and cancer.

During chronic infections and tumor progression, CD8 T cells gradually lose their effector functions and become exhausted. These exhausted CD8 T cells are heterogeneous and comprised of different subsets, including self-renewing progenitors that give rise to Ly108 - CX3CR1 + effector-like cells. Generation of these effector-like cells is essential for the control of chronic infections and tumors, albeit limited. However, the precise cues and mechanisms directing the formation and maintenance of exhausted effector-like are incompletely understood. Using genetic mouse models challenged with LCMV Clone 13 or syngeneic tumors, we show that the expression of a transcriptional repressor, growth factor independent 1 (Gfi1) is dynamically regulated in exhausted CD8 T cells, which in turn regulates the formation of exhausted effector-like cells. Gfi1 deletion in T cells dysregulates the chromatin accessibility and transcriptomic programs associated with the differentiation of LCMV Clone 13-specific CD8 T cell exhaustion, preventing the formation of effector-like and terminally exhausted cells while maintaining progenitors and a newly identified Ly108 + CX3CR1 + state. These Ly108 + CX3CR1 + cells have a distinct chromatin profile and may represent an alternative target for therapeutic interventions to combat chronic infections and cancer. In sum, we show that Gfi1 is a critical regulator of the formation of exhausted effector-like cells.

Combining PARP and DNA-PK Inhibitors With Irradiation Inhibits HPV-Negative Head and Neck Cancer Squamous Carcinoma Growth.

Novel targeted agents to inhibit DNA repair pathways to sensitize tumors to irradiation (IR) are being investigated as an alternative to chemoradiation for locally advanced human papilloma virus negative (HPV-negative) head and neck squamous cell carcinoma (HNSCC). Two well-characterized targets that, when inhibited, exhibit potent IR sensitization are PARP1 and DNA-PKcs. However, their cooperation in sensitizing HPV-negative HNSCC to IR remains to be explored given that PARP1 and DNA-Pk CS bind to unresected stalled DNA replication forks and cooperate to recruit XRCC1 to facilitate double-strand break repair. Here, we show that the combination of the DNA-PK inhibitor NU7441 and the PARP inhibitor olaparib significantly decrease proliferation (61-78%) compared to no reduction with either agent alone (p < 0.001) in both SCC1 and SCC6 cell lines. Adding IR to the combination further decreased cell proliferation (91-92%, p < 0.001) in SCC1 and SCC6. Similar results were observed using long-term colony formation assays [dose enhancement ratio (DER) 2.3-3.2 at 4Gy, p < 0.05]. Reduced cell survival was attributed to increased apoptosis and G2/M cell cycle arrest. Kinomic analysis using tyrosine (PTK) and serine/threonine (STK) arrays reveals that combination treatment results in the most potent inhibition of kinases involved in the CDK and ERK pathways compared to either agent alone. In vivo, a significant delay of tumor growth was observed in UM-SCC1 xenografts receiving IR with olaparib and/or NU7441, which was similar to the cisplatin-IR group. Both regimens were less toxic than cisplatin-IR as assessed by loss of mouse body weight. Taken together, these results demonstrate that the combination of NU7441 and olaparib with IR enhances HPV-negative HNSCC inhibition in both cell culture and in mice, suggesting a potential innovative combination for effectively treating patients with HPV-negative HNSCC.

VISTA is an inhibitory immune checkpoint that is increased after ipilimumab therapy in patients with prostate cancer.

To date, anti-CTLA-4 (ipilimumab) or anti-PD-1 (nivolumab) monotherapy has not been demonstrated to be of substantial clinical benefit in patients with prostate cancer. To identify additional immune-inhibitory pathways in the prostate-tumor microenvironment, we evaluated untreated and ipilimumab-treated tumors from patients in a presurgical clinical trial. Levels of the PD-L1 and VISTA inhibitory molecules increased on independent subsets of macrophages in treated tumors. Our data suggest that VISTA represents another compensatory inhibitory pathway in prostate tumors after ipilimumab therapy.

HIF1alpha-dependent glycolytic pathway orchestrates a metabolic checkpoint for the differentiation of TH17 and Treg cells.

Upon antigen stimulation, the bioenergetic demands of T cells increase dramatically over the resting state. Although a role for the metabolic switch to glycolysis has been suggested to support increased anabolic activities and facilitate T cell growth and proliferation, whether cellular metabolism controls T cell lineage choices remains poorly understood. We report that the glycolytic pathway is actively regulated during the differentiation of inflammatory T(H)17 and Foxp3-expressing regulatory T cells (T(reg) cells) and controls cell fate determination. T(H)17 but not T(reg) cell-inducing conditions resulted in strong up-regulation of the glycolytic activity and induction of glycolytic enzymes. Blocking glycolysis inhibited T(H)17 development while promoting T(reg) cell generation. Moreover, the transcription factor hypoxia-inducible factor 1α (HIF1α) was selectively expressed in T(H)17 cells and its induction required signaling through mTOR, a central regulator of cellular metabolism. HIF1α-dependent transcriptional program was important for mediating glycolytic activity, thereby contributing to the lineage choices between T(H)17 and T(reg) cells. Lack of HIF1α resulted in diminished T(H)17 development but enhanced T(reg) cell differentiation and protected mice from autoimmune neuroinflammation. Our studies demonstrate that HIF1α-dependent glycolytic pathway orchestrates a metabolic checkpoint for the differentiation of T(H)17 and T(reg) cells.