The genomes of cancers deficient in mismatch repair (MMR) contain exceptionally high numbers of somatic mutations. In a proof-of-concept study, we previously showed that colorectal cancers with MMR deficiency were sensitive to immune checkpoint blockade with anti-PD-1 antibodies. We have expanded this study to now evaluate efficacy of PD-1 blockade in patients with advanced MMR-deficient cancers across 12 different tumor types. Objective radiographic responses were observed in 53% of patients and complete responses were achieved in 21% of patients. Responses were durable with median progression-free and overall survival still not reached. Functional analysis in a responding patient demonstrated rapid in vivo expansion of neoantigen-specific T cell clones that were reactive to mutant neopeptides found in the tumor. These data support the hypothesis that the large proportion of mutant neoantigens in MMR-deficient cancers make them sensitive to immune checkpoint blockade, regardless of the cancers’ tissue of origin.

Purpose Glioblastoma multiforme (GBM) is the most common primary brain tumor in adults, and radiation is one of the main treatment modalities. However, cure rates remain low despite best available therapies. Immunotherapy is a promising modality that could work synergistically with radiation, which has been shown to increase antigen presentation and promote a proinflammatory tumor microenvironment. Programmed-death-1 (PD-1) is a surface receptor expressed on activated and exhausted T cells, which mediate T cell inhibition upon binding with its ligand PD-L1, expressed on many tumor types including human GBMs. We tested the combination of anti-PD-1 immunotherapy with stereotactic radiosurgery in a mouse orthotopic GBM model. Methods and Materials We performed intracranial implantation of mouse glioma cell line GL261 transfected with luciferase into C57BL/6 mice. Mice were stratified into 4 treatment groups: (1) control; (2) radiation only; (3) anti-PD-1 antibody only; and (4) radiation plus anti-PD-1 antibody. Overall survival was quantified. The mice were killed on day 21 after implantation to assess immunologic parameters in the brain/tumor, cervical lymph nodes, and spleen. Results Improved survival was demonstrated with combination anti-PD-1 therapy plus radiation compared with either modality alone: median survival was 25 days in the control arm, 27 days in the anti-PD-1 antibody arm, 28 days in the radiation arm, and 53 days in the radiation plus anti-PD-1 therapy arm (P<.05 by log-rank Mantle-Cox). Long-term survival was seen only in the combined treatment arm, with a fraction (15%–40%) of animals alive at day 180+ after treatment. Immunologic data on day 21 after implantation showed increased tumor infiltration by cytotoxic T cells (CD8+/interferon-γ+/tumor necrosis factor-α+) and decreased regulatory T cells (CD4+/FOXP3) in the combined treatment group compared with the single modality arms. Conclusions The combination of PD-1 blockade and localized radiation therapy results in long-term survival in mice with orthotopic brain tumors. These studies provide strong preclinical evidence to support combination trials in patients with GBM.

The c-Jun N-terminal kinases (JNK) are activated by various stimuli, including UV light, interleukin-1, tumor necrosis factor-␣ (TNF-␣), and CD28 costimulation. Induction of JNK by TNF-␣, a strong apoptosis inducer, implies a possible role of JNK in the regulation of programmed cell death. Present studies show that lethal doses of ␥ radiation (GR) induced JNK activities at the early phase of apoptosis in Jurkat T-cells. We demonstrate that JNK1 was activated by either the T-cell activation signals, anti-CD28 monoclonal antibody plus phorbol 12-myristate 13-acetate (PMA), or the apoptosisinducing treatment, GR; however, the induction patterns were different. In contrast to the rapid and transient JNK1 activation caused by CD28 signaling plus PMA, GR induced a delayed and persistent JNK1 activation. This implies a distinct regulatory mechanism and specific function of JNK1 in irradiated cells. The nuclear and cytosolic JNK1 activities were simultaneously increased in the irradiated cells without an evident change in the protein levels. The abilities of GR to induce JNK1 activation and DNA fragmentation were correlated. Peripheral blood lymphocytes were more sensitive to GR than Jurkat cells in JNK1 induction. The responsiveness of JNK1 to GR suggests the involvement of JNK1 in the initiation of the apoptosis process.

Full T cell activation requires TCR engagement (signal 1) in the context of costimulation (signal 2). Costimulation is required for maximal expression of effector cytokines and prevention of T cell anergy. It has become increasingly clear that another major function of costimulation is to up-regulate the metabolic machinery necessary for T cell function. In this report we demonstrate that anergic T cells are metabolically anergic, in that upon full stimulation (signals 1 plus 2) they fail to up-regulate the machinery necessary to support increased metabolism. These findings suggest that one mechanism responsible for the maintenance of T cell anergy is failure to up-regulate the metabolic machinery. Furthermore, we demonstrate that by blocking leucine, glucose, and energy metabolism, T cell activation is mitigated. Additionally, inhibition of these metabolic pathways during T cell activation leads to anergy in Th1-differentiated cells. Overall, our findings extend the role of T cell metabolism in regulating T cell function.

The c-Jun amino-terminal kinases (JNKsJ/stress-activated protein kinases (SAPKs) play a crucial role in stress responses in mammalian cells. The mechanism underlying this pathway in the hematopoietic system is unclear, but it is a key in understanding the molecular basis of blood cell differentiation. We have cloned a novel protein kinase, termed hematopoietic progenitor kinase 1 (HPKI), that is expressed predominantly in hematopoietic cells, including early progenitor cells. HPK1 is related distantly to the p21Cdc42/Ra'~-activated kinase (PAK) and yeast STE20 implicated in the mitogen-activated protein kinase (MAPK) cascade. Expression of HPK1 activates JNK1 specifically, and it elevates strongly AP-l-mediated transcriptional activity in vivo. HPKI binds and phosphorylates MEKK1 directly, whereas JNK1 activation by HPK1 is inhibited by a dominant-negative MEKK1 or MKK4/SEK mutant. Interestingly, unlike PAK65, HPK1 does not contain the small GTPase Racl/Cdc42-binding domain and does not bind to either Racl or Cdc42, suggesting that HPK1 activation is Racl/Cdc42-independent. These results indicate that HPK1 is a novel functional activator of the JNK/SAPK signaling pathway.