Antimetabolite TTL-315 selectively kills glucose-deprived cancer cells and enhances responses to cytotoxic chemotherapy in preclinical models of cancer.

Maintaining thiol homeostasis is an imperative for cancer cell survival in the nutrient-deprived microenvironment of solid tumors. Despite this metabolic vulnerability, a selective approach has yet to be developed to disrupt thiol homeostasis in solid tumors for therapeutic purposes. In this study, we report the identification of 2-mercaptopropionyl glycine disulfide (TTL-315) as a novel antimetabolite that blocks cell survival in a manner conditional on glucose deprivation. In the presence of glucose, TTL-315 lacks cytotoxic effects in normal cells where it is detoxified by reduction to 2-mercaptopropionyl glycine, a compound with known clinical pharmacologic and safety profiles. In several rodent models of aggressive breast, lung and skin cancers, TTL-315 blocked tumor growth and cooperated with the DNA damaging drug cisplatin to trigger tumor regression. Our results offer preclinical proof of concept for TTL-315 as a novel antimetabolite to help selectively eradicate solid tumors by exploiting the glucose-deprived conditions of the tumor microenvironment

IDO1 and inflammatory neovascularization: bringing new blood to tumor-promoting inflammation

In parallel with the genetic and epigenetic changes that accumulate in tumor cells, chronic tumor-promoting inflammation establishes a local microenvironment that fosters the development of malignancy. While knowledge of the specific factors that distinguish tumor-promoting from non-tumor-promoting inflammation remains inchoate, nevertheless, as highlighted in this series on the ‘Hallmarks of Cancer’, it is clear that tumor-promoting inflammation is essential to neoplasia and metastatic progression making identification of specific factors critical. Studies of immunometabolism and inflamometabolism have revealed a role for the tryptophan catabolizing enzyme IDO1 as a core element in tumor-promoting inflammation. At one level, IDO1 expression promotes immune tolerance to tumor antigens, thereby helping tumors evade adaptive immune control. Additionally, recent findings indicate that IDO1 also promotes tumor neovascularization by subverting local innate immunity. This newly recognized function for IDO1 is mediated by a unique myeloid cell population termed IDVCs (IDO1-dependent vascularizing cells). Initially identified in metastatic lesions, IDVCs may exert broader effects on pathologic neovascularization in various disease settings. Mechanistically, induction of IDO1 expression in IDVCs by the inflammatory cytokine IFNγ blocks the antagonistic effect of IFNγ on neovascularization by stimulating the expression of IL6, a powerful pro-angiogenic cytokine. By contributing to vascular access, this newly ascribed function for IDO1 aligns with its involvement in other cancer hallmark functionalities, (tumor-promoting inflammation, immune escape, altered cellular metabolism, metastasis), which may stem from an underlying role in normal physiological functions such as wound healing and pregnancy. Understanding the nuances of how IDO1 involvement in these cancer hallmark functionalities varies between different tumor settings will be crucial to the future development of successful IDO1-directed therapies

Alternate cyclin D1 mRNA splicing modulates P27\u3csup\u3eKlP1\u3c/sup\u3e binding and cell migration

Cyclin D1 is an important cell cycle regulator but in cancer its overexpression also increases cellular migration mediated by p27KlP1 stabilization and RhoA inhibition. Recently, a common polymorphism at the exon 4-intron 4 boundary of the human cyclin D1 gene within a splice donor region was associated with an altered risk of developing cancer. Altered RNA splicing caused by this polymorphism gives rise to a variant cyclin D1 isoform termed cyclin D1b, which has the same N-terminus as the canonical cyclin D1a isoform but a distinct C-terminus. In this study we show that these different isoforms have unique properties with regard to the cellular migration function of cyclin D1. Whereas they displayed little difference in transcriptional co-repression assays on idealized reporter genes, microarray cDNA expression analysis revealed differential regulation of genes including those that influence cellular migration. Additionally, while cyclin D1a stabilized p27KIP1 and inhibited RhoA-induced ROCK kinase activity, promoting cellular migration, cyclin D1b failed to stabilize p27KIP1 or inhibit ROCK kinase activity and had no effect on migration. Our findings argue that alternate splicing is an important determinant of the function of cyclin D1 in cellular migration

IDO1 is an Integral Mediator of Inflammatory Neovascularization.

The immune tolerogenic effects of IDO1 (indoleamine 2,3-dioxygenase 1) have been well documented and genetic studies in mice have clearly established the significance of IDO1 in tumor promotion. Dichotomously, the primary inducer of IDO1, the inflammatory cytokine IFNγ (interferon-γ), is a key mediator of immune-based tumor suppression. One means by which IFNγ can exert an anti-cancer effect is by decreasing tumor neovascularization. We speculated that IDO1 might contribute to cancer promotion by countering this anti-neovascular effect of IFNγ, possibly through IDO1-potentiated elevation of the pro-tumorigenic inflammatory cytokine IL6 (interleukin-6). In this study, we investigated how genetic loss of IDO1 affects neovascularization in mouse models of oxygen-induced retinopathy and lung metastasis. Neovascularization in both models was significantly reduced in mice lacking IDO1, was similarly reduced with loss of IL6, and was restored in both cases by concomitant loss of IFNγ. Likewise, the lack of IDO1 or IL6 resulted in reduced metastatic tumor burden and increased survival, which the concomitant loss of IFNγ abrogated. This insight into IDO1\u27s involvement in pro-tumorigenic inflammatory neovascularization may have important ramifications for IDO1 inhibitor development, not only in cancer where clinical trials are currently ongoing, but in other disease indications associated with neovascularization as well

Intestinal barrier tightening by a cell-penetrating antibody to Bin1, a candidate target for immunotherapy of ulcerative colitis.

Patients afflicted with ulcerative colitis (UC) are at increased risk of colorectal cancer. While its causes are not fully understood, UC is associated with defects in colonic epithelial barriers that sustain inflammation of the colon mucosa caused by recruitment of lymphocytes and neutrophils into the lamina propria. Based on genetic evidence that attenuation of the bridging integrator 1 (Bin1) gene can limit UC pathogenicity in animals, we have explored Bin1 targeting as a therapeutic option. Early feasibility studies in the dextran sodium sulfate mouse model of experimental colitis showed that administration of a cell-penetrating Bin1 monoclonal antibody (Bin1 mAb 99D) could prevent lesion formation in the colon mucosa in part by preventing rupture of lymphoid follicles. In vivo administration of Bin1 mAb altered tight junction protein expression and cecal barrier function. Strikingly, electrophysiology studies in organ cultures showed that Bin1 mAb could elevate resistance and lowe

Indoleamine 2,3-Dioxygenase and Its Therapeutic Inhibition in Cancer

The tryptophan catabolic enzyme indoleamine 2,3-dioxygenase-1 (IDO1) has attracted enormous attention in driving cancer immunosuppression, neovascularization, and metastasis. IDO1 suppresses local CD8 + T effector cells and natural killer cells and induces CD4 + T regulatory cells (iTreg) and myeloid-derived suppressor cells (MDSC). The structurally distinct enzyme tryptophan dioxygenase (TDO) also has been implicated recently in immune escape and metastatic progression. Lastly, emerging evidence suggests that the IDO1-related enzyme IDO2 may support IDO1-mediated iTreg and contribute to B-cell inflammed states in certain cancers. IDO1 and TDO are upregulated widely in neoplastic cells but also variably in stromal, endothelial, and innate immune cells of the tumor microenviroment and in tumor-draining lymph nodes. Pharmacological and genetic proofs in preclinical models of cancer have validated IDO1 as a cancer therapeutic target. IDO1 inhibitors have limited activity on their own but greatly enhance “immunogenic” chemotherapy or immune checkpoint drugs. IDO/TDO function is rooted in inflammatory programming, thereby influencing tumor neovascularization, MDSC generation, and metastasis beyond effects on adaptive immune tolerance. Discovery and development of two small molecule enzyme inhibitors of IDO1 have advanced furthest to date in Phase II/III human trials (epacadostat and navoximod, respectively). Indoximod, a tryptophan mimetic compound with a different mechanism of action in the IDO pathway has also advanced in multiple Phase II trials. Second generation combined IDO/TDO inhibitors may broaden impact in cancer treatment, for example, in addressing IDO1 bypass (inherent resistance) or acquired resistance to IDO1 inhibitors. This review surveys knowledge about IDO1 function and how IDO1 inhibitors reprogram inflammation to heighten therapeutic responses in cancer

Indoleamine 2,3-Dioxygenase and Its Therapeutic Inhibition in Cancer

The tryptophan catabolic enzyme indoleamine 2,3-dioxygenase-1 (IDO1) has attracted enormous attention in driving cancer immunosuppression, neovascularization, and metastasis. IDO1 suppresses local CD8 + T effector cells and natural killer cells and induces CD4 + T regulatory cells (iTreg) and myeloid-derived suppressor cells (MDSC). The structurally distinct enzyme tryptophan dioxygenase (TDO) also has been implicated recently in immune escape and metastatic progression. Lastly, emerging evidence suggests that the IDO1-related enzyme IDO2 may support IDO1-mediated iTreg and contribute to B-cell inflammed states in certain cancers. IDO1 and TDO are upregulated widely in neoplastic cells but also variably in stromal, endothelial, and innate immune cells of the tumor microenviroment and in tumor-draining lymph nodes. Pharmacological and genetic proofs in preclinical models of cancer have validated IDO1 as a cancer therapeutic target. IDO1 inhibitors have limited activity on their own but greatly enhance “immunogenic” chemotherapy or immune checkpoint drugs. IDO/TDO function is rooted in inflammatory programming, thereby influencing tumor neovascularization, MDSC generation, and metastasis beyond effects on adaptive immune tolerance. Discovery and development of two small molecule enzyme inhibitors of IDO1 have advanced furthest to date in Phase II/III human trials (epacadostat and navoximod, respectively). Indoximod, a tryptophan mimetic compound with a different mechanism of action in the IDO pathway has also advanced in multiple Phase II trials. Second generation combined IDO/TDO inhibitors may broaden impact in cancer treatment, for example, in addressing IDO1 bypass (inherent resistance) or acquired resistance to IDO1 inhibitors. This review surveys knowledge about IDO1 function and how IDO1 inhibitors reprogram inflammation to heighten therapeutic responses in cancer

A Sub-Type of Familial Pancreatic Cancer: Evidence and Implications of Loss-of-Function Polymorphisms in Indoleamine-2,3-Dioxygenase-2.

BACKGROUND: Variation in an individual\u27s genetic status can impact the development of pancreatic ductal adenocarcinoma; however, the majority of familial pancreatic cancers (FPC) cannot yet be attributed to a specific inherited mutation. We present data suggesting a correlation between loss-of-function single nucleotide polymorphisms (SNPs) in an immune regulator gene, indoleamine-2,3-dioxygenase-2 (IDO2), and an increased risk of FPC. STUDY DESIGN: Germline DNA from patients who underwent resection for pancreatic ductal adenocarcinoma (n = 79) was sequenced for the IDO2 SNPs R248W and Y359Stop. Genotypes resulting in inactivation of IDO2 (Y325X homozygous, R248W homozygous) were labeled as homozygous, and the other genotypes were grouped as wild-type or heterozygous. Genotype distributions of each SNP were analyzed for Hardy-Weinberg deviation. A genotype frequency set from the 1000 Genomes Project (n = 99) was used as a genetic control for genotype distribution comparisons. RESULTS: A significant 2-fold increase in the overall prevalence of the Y359Stop homozygous genotype compared with the expected Hardy-Weinberg equilibrium was noted (p \u3c 0.05). Familial pancreatic cancer was noted in 15 cases (19%) and comparison of the FPC cohort set to the genetic control set showed a 3-fold increase in Y359Stop homozygous rates (p = 0.054). Overall in our cohort, the homozygous genotype group was associated with increased risk of FPC (odds ratio 5.4; 95% CI 1.6 to 17.6; p \u3c 0.01). Sex, age at diagnosis, and history of tobacco use were not found to be significantly associated with FPC. CONCLUSIONS: Our preliminary data suggest a strong association between the IDO2 inactivating Y359Stop SNP and an increased risk of FPC when compared with the control group. Future studies will evaluate the value of IDO2 genotyping as a prognostic, early detection marker for pancreatic ductal adenocarcinoma and a predictive marker for novel immune checkpoint therapies

IDO2 in Immunomodulation and Autoimmune Disease.

IDO2 is a relative of IDO1 implicated in tryptophan catabolism and immune modulation but its specific contributions to normal physiology and pathophysiology are not known. Evolutionary genetic studies suggest that IDO2 has a unique function ancestral to IDO1. In mice, IDO2 gene deletion does not appreciably affect embryonic development or hematopoiesis, but it leads to defects in allergic or autoimmune responses and in the ability of IDO1 to influence the generation of T regulatory cells. Gene expression studies indicate that IDO2 is a basally and more narrowly expressed gene than IDO1 and that IDO2 is uniquely regulated by AhR, which serves as a physiological receptor for the tryptophan catabolite kynurenine. In the established KRN transgenic mouse model of rheumatoid arthritis, where IDO1 gene deletion has no effect, IDO2 deletion selectively blunts responses to autoantigen but has no effect on responses to neoantigen challenge. In human populations, natural variations in IDO2 gene sequence that attenuate enzymatic activity have been reported to influence brain cancer control and adaptive immune responses to the IDO2 protein itself, consistent with the concept that IDO2 is involved in shaping immune tolerance in human beings. Biochemical and pharmacological studies provide further evidence of differences in IDO2 enzymology and function relative to IDO1. We suggest that IDO2 may act in a distinct manner from IDO1 as a set-point for tolerance to altered-self antigens along the self-non-self continuum where immune challenges from cancer and autoimmunity may arise