Spontaneous CD8 T-cell responses occur in growing tumors but are usually poorly effective. Understanding the molecular and cellular mechanisms that drive these responses is of major interest as they could be exploited to generate a more efficacious antitumor immunity. As such, stimulator of IFN genes (STING), an adaptor molecule involved in cytosolic DNA sensing, is required for the induction of antitumor CD8 T responses in mouse models of cancer. Here, we find that enforced activation of STING by intratumoral injection of cyclic dinucleotide GMP-AMP (cGAMP), potently enhanced antitumor CD8 T responses leading to growth control of injected and contralateral tumors in mouse models of melanoma and colon cancer. The ability of cGAMP to trigger antitumor immunity was further enhanced by the blockade of both PD1 and CTLA4. The STING-dependent antitumor immunity, either induced spontaneously in growing tumors or induced by intratumoral cGAMP injection was dependent on type I IFNs produced in the tumor microenvironment. In response to cGAMP injection, both in the mouse melanoma model and an ex vivo model of cultured human melanoma explants, the principal source of type I IFN was not dendritic cells, but instead endothelial cells. Similarly, endothelial cells but not dendritic cells were found to be the principal source of spontaneously induced type I IFNs in growing tumors. These data identify an unexpected role of the tumor vasculature in the initiation of CD8 T-cell antitumor immunity and demonstrate that tumor endothelial cells can be targeted for immunotherapy of melanoma.M etastatic melanoma is a highly aggressive cancer with a fast increasing incidence worldwide. Unless diagnosed early and surgically resected, the disease becomes metastatic and life threatening. Both chemotherapy and irradiation are ineffective. Novel therapies that target oncogenic drivers have brought some improvements, but tumor cells escape regularly (1). Melanoma is a prototypical immunogenic tumor, as shown by the occurrence of spontaneous CD8 T-cell responses that drive tumor regressions and by the identification of CD8 T cells that recognize melanoma antigens (2, 3). Although many immunotherapeutic strategies have been developed to induce such responses, clinical efficacies have been poor. More recently, "checkpoint blockade" therapies that target T-cell-inhibitory pathways mediated by CTLA4 (4) and PD1 (5) have yielded encouraging clinical results and demonstrated that spontaneous CD8 T-cell responses in tumors can be boosted to treat melanoma.The mechanisms that drive spontaneous antitumor immune responses are poorly understood. Type I IFNs (IFN-α and IFN-β) may play a role as the expression type I IFN-related genes in primary melanoma has been associated with spontaneous tumor regressions (6) and correlated to the tumor infiltration by specific CD8+ T cells (6, 7). Furthermore, the lack of type I IFN signaling or IFN-β expression inhibited the generation of tumor-specific CD8 T cells and accelerated tumor growth in a murine melanoma mo...

Lymphatic vasculature is increasingly recognized as an important factor both in the regulation of normal tissue homeostasis and immune response and in many diseases, such as inflammation, cancer, obesity, and hypertension. In the last few years, in addition to the central role of vascular endothelial growth factor (VEGF)-C/VEGF receptor-3 signaling in lymphangiogenesis, significant new insights were obtained about Notch, transforming growth factor β/bone morphogenetic protein, Ras, mitogen-activated protein kinase, phosphatidylinositol 3 kinase, and Ca(2+)/calcineurin signaling pathways in the control of growth and remodeling of lymphatic vessels. An emerging picture of lymphangiogenic signaling is complex and in many ways distinct from the regulation of angiogenesis. This complexity provides new challenges, but also new opportunities for selective therapeutic targeting of lymphatic vasculature.

Knowledge of these intricate ROS signaling pathways and identification of the culprit NADPH oxidases is likely to reveal novel therapeutic opportunities to prevent angiogenesis that occurs during cancer and which is responsible for the revascularization after current antiangiogenic treatment.

BackgroundDysfunctional lymphatic vessel formation has been implicated in a number of pathological conditions including cancer metastasis, lymphedema, and impaired wound healing. The vascular endothelial growth factor (VEGF) family is a major regulator of lymphatic endothelial cell (LEC) function and lymphangiogenesis. Indeed, dissemination of malignant cells into the regional lymph nodes, a common occurrence in many cancers, is stimulated by VEGF family members. This effect is generally considered to be mediated via VEGFR-2 and VEGFR-3. However, the role of specific receptors and their downstream signaling pathways is not well understood.Methods and ResultsHere we delineate the VEGF-C/VEGF receptor (VEGFR)-3 signaling pathway in LECs and show that VEGF-C induces activation of PI3K/Akt and MEK/Erk. Furthermore, activation of PI3K/Akt by VEGF-C/VEGFR-3 resulted in phosphorylation of P70S6K, eNOS, PLCγ1, and Erk1/2. Importantly, a direct interaction between PI3K and VEGFR-3 in LECs was demonstrated both in vitro and in clinical cancer specimens. This interaction was strongly associated with the presence of lymph node metastases in primary small cell carcinoma of the lung in clinical specimens. Blocking PI3K activity abolished VEGF-C-stimulated LEC tube formation and migration.ConclusionsOur findings demonstrate that specific VEGFR-3 signaling pathways are activated in LECs by VEGF-C. The importance of PI3K in VEGF-C/VEGFR-3-mediated lymphangiogenesis provides a potential therapeutic target for the inhibition of lymphatic metastasis.

Highlights d Inflammation-dependent APOBEC3C C-to-T deaminase fuels human HSPC expansion d C-to-T mutagenesis increases during human MPN pre-LSC evolution d Inflammation-induced ADAR1p150 isoform expression promotes hyperediting in pre-LSCs d JAK2/STAT3 inhibition and shRNA ADAR1 knockdown prevent STAT3 isoform switching in LSCs

These results suggest that activation of VEGFR-1 by VEGF-A within the carcinoma, and activation of lymphatic endothelial cell VEGFR-3 by VEGF-D within the adjacent benign stroma may be important signaling mechanisms involved in the progression and subsequent metastatic spread of prostate cancer. Thus inhibition of these pathways may contribute to therapeutic strategies for the management of prostate cancer.

Highlights d Endothelial calcineurin is dispensable for physiological and tumor angiogenesis d Endothelial calcineurin stabilizes vessels and restrains metastatic outgrowth d Calcineurin/NFAT target BMP2 induces differentiation of metastatic cells

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