The characterization of cancer genomes has provided insight into somatically altered genes across tumors, transformed our understanding of cancer biology, and enabled tailoring of therapeutic strategies. However, the function of most cancer alleles remains mysterious, and many cancer features transcend their genomes. Consequently, tumor genomic characterization does not influence therapy for most patients. Approaches to understand the function and circuitry of cancer genes provide complementary approaches to elucidate both oncogene and non-oncogene dependencies. Emerging work indicates that the diversity of therapeutic targets engendered by non-oncogene dependencies is much larger than the list of recurrently mutated genes. Here we describe a framework for this expanded list of cancer targets, providing novel opportunities for clinical translation.

CD8+ T cells play an important role in providing protective immunity against a wide range of pathogens, and a number of different factors control their activation. Although CD40L-mediated CD40 licensing of dendritic cells (DCs) by CD4+ T cells is known to be necessary for the generation of a robust CD8+ T cell response, the contribution of CD8+ T cell-expressed CD40L on DC licensing is less clear. We have previously shown that CD8+ T cells are able to induce the production of IL-12 p70 by DCs in a CD40L-dependent manner, providing some evidence that CD8+ T cell-mediated activation of DCs is possible. To better understand the role of CD40L on CD8+ T cell responses, we generated and characterized CD40L-expressing CD8+ T cells both in vitro and in vivo. We found that CD40L was expressed on 30–50% of effector CD8+ T cells when stimulated and that this expression was transient. The expression of CD40L on CD8+ T cells promoted the proliferation and differentiation of both the CD40L-expressing CD8+ T cells and the bystander effector CD8+ T cells. This process occurred via a cell-extrinsic manner and was mediated by DCs. These data demonstrate the existence of a mechanism where CD8+ T cells and DCs cooperate to maximize CD8+ T cell responses.

T cell activation is mediated by signaling pathways originating from the T cell receptor (TCR). Propagation of signals downstream of the TCR involves a cascade of numerous kinases, some of which have yet to be identified. Through a screening strategy that we have previously introduced, PHA-767491, an inhibitor of the kinases Cdc7 and Cdk9, was identified to impede TCR signaling. PHA-767491 suppressed several T cell activation phenomena, including the expression of activation markers, proliferation, and effector functions. We also observed a defect in TCR signaling pathways upon PHA-767491 treatment. Inhibition of Cdc7/Cdk9 impairs T cell responses, which could potentially be detrimental for the immune response to tumors, and also compromises the ability to resist infections. The Cdc7/Cdk9 inhibitor is a strong candidate as a cancer therapeutic, but its effect on the immune system poses a problem for clinical applications.

Influenza and asthma are two of the major public health concerns in the world today. During the 2009 influenza pandemic asthma was found to be the commonest comorbid illness of patients admitted to hospital. Unexpectedly, it was also observed that asthmatic patients admitted to hospital with influenza infection were less likely to die or require admission to intensive care compared with non-asthmatics. Using an in vivo model of asthma and influenza infection we demonstrate that prior exposure to Blomia tropicalis extract (BTE) leads to an altered immune response to influenza infection, comprised of less severe weight loss and faster recovery following infection. This protection was associated with significant increases in T cell numbers in the lungs of BTE sensitised and infected mice, as well as increased IFN-γ production from these cells. In addition, elevated numbers of CD11b+ dendritic cells (DCs) were found in the lung draining lymph nodes following infection of BTE sensitised mice compared to infected PBS treated mice. These CD11b+ DCs appeared to be better at priming CD8 specific T cells both in vivo and ex vivo, a function not normally attributed to CD11b+ DCs. We propose that this alteration in cross-presentation and more efficient T cell priming seen in BTE sensitised mice, led to the earlier increase in T cells in the lungs and subsequently faster clearance of the virus and reduced influenza induced pathology. We believe this data provides a novel mechanism that explains why asthmatic patients may present with less severe disease when infected with influenza.

Summary The significance of intracellular Ap 4 A levels over immune activity of dendritic cells (DCs) has been studied in Nudt2 fl/fl /CD11c-cre mice. The transgenic mice have been generated by crossing floxed NUDT2 gene mice with DC marker CD11c recombinase (cre) mice. The DCs derived from these mice have higher levels of Ap 4 A (≈30-fold) compared with those derived from Nudt2 +/+ mice. Interestingly, the elevated Ap 4 A in DCs has led them to possess higher motility and lower directional variability. In addition, the DCs are able to enhance immune protection indicated by the higher cross-presentation of antigen and priming of CD8 + OT-I T cells. Overall, the study denotes prominent impact of Ap 4 A over the functionality of DCs. The Nudt2 fl/fl /CD11c-cre mice could serve as a useful tool to study the influence of Ap 4 A in the critical immune mechanisms of DCs.

CD8 T cells play an important role in protective immunity against a wide range of pathogens and the factors that control their activation are clearly important. CD40L-mediated CD40 licensing of dendritic cells by CD4 T cells is known to be necessary for the generation of a robust CD8 T cell response. Less clear is the contribution of CD40L on CD8 T cells to their activation. We have previously shown that CD8 T cells are able to induce the production of IL-12 p70 by dendritic cells in a CD40L-dependent manner. To better understand the role of CD40L on CD8 T cells responses, we generated and characterized CD40L-expressing CD8 T cells both in vitro and in vivo. We found that CD40L is expressed on 30-50% of activated effector CD8 T cells and the differentiation of CD8 T cells into CD40L-expressing cells is strongly induced by IL-12, suggesting the presence of a positive feedback mechanism mediated by CD40L and IL-12. Using an influenza A mouse model, we examined whether this mechanism is involved in the primary expansion of CD8 T cells during an infection and whether CD40L-expressing CD8 T cells are able to license dendritic cells for optimal memory CD8 T cell programming. In the absence of CD40L signaling, the ability to upregulate CD25 and downregulate CD62L is diminished in CD8 T cells, causing an impairment in their primary expansion and also their ability to accumulate at the site of infection.

CD40L is a principal mediator of a large range of humoral and cellular responses and CD40L-mediated licensing of dendritic cells is known to be necessary for the generation of robust effector and memory CD8+ T cell responses. Although the effects of CD40L when expressed on CD4+ T cells are well studied, its role when expressed on CD8+ T cells remain unclear. We have previously reported that CD40L signaling mediates the induction of IL-12 p70 production in dendritic cells when expressed by CD8+ T cells. However, the role and importance of this mechanism in CD8+ T cell responses during an infection are not known. To investigate the function of CD40L when expressed on CD8+ T cells in an in vivo mouse model, we crossed OT-I CD8+ T cell receptor transgenic mice with CD40L−/− mice to generate OVA-specific CD8+ T cells that are unable to expressed CD40L. By transferring CD8+ T cells from these mice into CD40L-competent mice and using a strain of influenza that expresses the OVA epitope recognized by OT-I CD8+ T cells, we were able to create an influenza mouse model where CD40L signaling is absent only on the responding CD8+ T cells. Our analysis indicates that CD40L signaling by CD8+ T cells confers protection against influenza infection and that this is likely dependent on the ability of CD8+ T cells to induce IL-12 p70 production in a CD40L-dependent manner.

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