Cancer as an evolutionary and ecological process

Neoplasms are microcosms of evolution. Within a neoplasm, a mosaic of mutant cells compete for space and resources, evade predation by the immune system and can even cooperate to disperse and colonize new organs. The evolution of neoplastic cells explains both why we get cancer and why it has been so difficult to cure. The tools of evolutionary biology and ecology are providing new insights into neoplastic progression and the clinical control of cancer.

IDO2 is critical for IDO1-mediated T-cell regulation and exerts a non-redundant function in inflammation

IDO2 is implicated in tryptophan catabolism and immunity but its physiological functions are not well established. Here we report the characterization of mice genetically deficient in IDO2, which develop normally but exhibit defects in IDO-mediated T-cell regulation and inflammatory responses. Construction of this strain was prompted in part by our discovery that IDO2 function is attenuated in macrophages from Ido1 (-/-) mice due to altered message splicing, generating a functional mosaic with implications for interpreting findings in Ido1 (-/-) mice. No apparent defects were observed in Ido2 (-/-) mice in embryonic development or hematopoietic differentiation, with wild-type profiles documented for kynurenine in blood serum and for immune cells in spleen, lymph nodes, peritoneum, thymus and bone marrow of naive mice. In contrast, upon immune stimulation we determined that IDO1-dependent T regulatory cell generation was defective in Ido2 (-/-) mice, supporting Ido1-Ido2 genetic interaction and establishing a functional role for Ido2 in immune modulation. Pathophysiologically, both Ido1 (-/-) and Ido2 (-/-) mice displayed reduced skin contact hypersensitivity responses, but mechanistic distinctions were apparent, with only Ido2 deficiency associated with a suppression of immune regulatory cytokines that included GM-CSF, G-CSF, IFN-γ, TNF-α, IL-6 and MCP-1/CCL2. Different contributions to inflammation were likewise indicated by the finding that Ido2 (-/-) mice did not phenocopy Ido1 (-/-) mice in the reduced susceptibility of the latter to inflammatory skin cancer. Taken together, our results offer an initial glimpse into immune modulation by IDO2, revealing its genetic interaction with IDO1 and distinguishing its non-redundant contributions to inflammation.

A comprehensive survey of clonal diversity measures in Barrett's esophagus as biomarkers of progression to esophageal adenocarcinoma

Neoplastic progression is an evolutionary process driven by the generation of clonal diversity and natural selection on that diversity within a neoplasm. We hypothesized that clonal diversity is associated with risk of progression to cancer. We obtained molecular data from a cohort of 239 participants with Barrett's esophagus, including microsatellite shifts and loss of heterozygosity, DNA content tetraploidy and aneuploidy, methylation, and sequence mutations. Using these data, we tested all major diversity measurement methods, including genetic divergence and entropy-based measures, to determine which measures are correlated with risk of progression to esophageal adenocarcinoma. We also tested whether the use of different sets of loci and alterations to define clones (e.g., selectively advantageous versus evolutionarily neutral) improved the predictive value of the diversity indices. All diversity measures were strong and highly significant predictors of progression (Cox proportional hazards model, P < 0.001). The type of alterations evaluated had little effect on the predictive value of most of the diversity measures. In summary, diversity measures are robust predictors of progression to cancer in this cohort.

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.

IDO2 is a critical mediator of autoantibody production and inflammatory pathogenesis in a mouse model of autoimmune arthritis

Rheumatoid arthritis and other autoimmune disorders are associated with altered activity of the immunomodulatory enzyme IDO. However, the precise contributions of IDO function to autoimmunity remain unclear. In this article, we examine the effect of two different IDO enzymes, IDO1 and IDO2, on the development of autoimmune arthritis in the KRN preclinical model of rheumatoid arthritis. We find that IDO2, not IDO1, is critical for arthritis development, providing direct evidence of separate in vivo functions for IDO1 and IDO2. Mice null for Ido2 display decreased joint inflammation relative to wild-type mice owing to a reduction in pathogenic autoantibodies and Ab-secreting cells. Notably, IDO2 appears to specifically mediate autoreactive responses, but not normal B cell responses, as total serum Ig levels are not altered and IDO2 knockout mice are able to mount productive Ab responses to model Ags in vitro and in vivo. Reciprocal adoptive transfer studies confirm that autoantibody production and arthritis are modulated by IDO2 expression in a cell type extrinsic to the T cell. Taken together, our results, provide important insights into IDO2 function by defining its pathogenic contributions to autoantibody-mediated autoimmunity.

Differential Roles of IDO1 and IDO2 in T and B Cell Inflammatory Immune Responses

Indoleamine-2,3-dioxygenase (IDO)1 and IDO2 are two closely related tryptophan catabolizing enzymes encoded by linked genes. The IDO pathway is also immunomodulatory, with IDO1 well-characterized as a mediator of tumor immune evasion. Due to its homology with IDO1, IDO2 has been proposed to have a similar immunoregulatory function. Indeed, IDO2, like IDO1, is necessary for the differentiation of regulatory T cells in vitro. However, compared to IDO1, in vivo studies demonstrated a contrasting role for IDO2, with experiments in preclinical models of autoimmune arthritis establishing a proinflammatory role for IDO2 in mediating B and T cell activation driving autoimmune disease. Given their potentially opposing roles in inflammatory responses, interpretation of results obtained using IDO1 or IDO2 single knockout mice could be complicated by the expression of the other enzyme. Here we use IDO1 and IDO2 single and double knockout (dko) mice to define the differential roles of IDO1 and IDO2 in B cell-mediated immune responses. Autoreactive T and B cell responses and severity of joint inflammation were decreased in IDO2 ko, but not IDO1 ko arthritic mice. Dko mice had a reduction in the number of autoantibody secreting cells and severity of arthritis: however, percentages of differentiated T cells and their associated cytokines were not reduced compared to IDO1 ko or wild-type mice. These data suggest that autoreactive B cell responses are mediated by IDO2, while autoreactive T cell responses are indirectly affected by IDO1 expression in the IDO2 ko mice. IDO2 also influenced antibody responses in models of influenza infection and immunization with T cell-independent type II antigens. Taken together, these studies provide evidence for the contrasting roles IDO1 and IDO2 play in immune responses, with IDO1 mediating T cell suppressive effects and IDO2 working directly in B cells as a proinflammatory mediator of B cell responses.

The role of genetic diversity in cancer

The role of genetic heterogeneity within neoplasms is increasingly recognized as important for understanding the dynamics of cancer progression, cancer stem cells, and therapeutic resistance, and there is interest in intratumoral heterogeneity measurements as potential biomarkers for risk stratification. In this issue of the JCI, Park et al. characterize this genetic diversity in carcinoma in situ and in invasive regions from 3 types of human breast cancers and lay the groundwork for translation of these measures to the clinic.

IDO2 Modulates T Cell-Dependent Autoimmune Responses through a B Cell-Intrinsic Mechanism

Mechanistic insight into how adaptive immune responses are modified along the self-nonself continuum may offer more effective opportunities to treat autoimmune disease, cancer, and other sterile inflammatory disorders. Recent genetic studies in the KRN mouse model of rheumatoid arthritis demonstrate that the immunomodulatory molecule IDO2 modifies responses to self-antigens; however, the mechanisms involved are obscure. In this study, we show that IDO2 exerts a critical function in B cells to support the generation of autoimmunity. In experiments with IDO2-deficient mice, adoptive transplant experiments demonstrated that IDO2 expression in B cells was both necessary and sufficient to support robust arthritis development. IDO2 function in B cells was contingent on a cognate, Ag-specific interaction to exert its immunomodulatory effects on arthritis development. We confirmed a similar requirement in an established model of contact hypersensitivity, in which IDO2-expressing B cells are required for a robust inflammatory response. Mechanistic investigations showed that IDO2-deficient B cells lacked the ability to upregulate the costimulatory marker CD40, suggesting IDO2 acts at the T-B cell interface to modulate the potency of T cell help needed to promote autoantibody production. Overall, our findings revealed that IDO2 expression by B cells modulates autoimmune responses by supporting the cross talk between autoreactive T and B cells.

Therapeutic antibody targeting of indoleamine-2,3-dioxygenase (IDO2) inhibits autoimmune arthritis

Rheumatoid arthritis (RA) is a debilitating inflammatory autoimmune disease with no known cure. Recently, we identified the immunomodulatory enzyme indoleamine-2,3-dioxygenase 2 (IDO2) as an essential mediator of autoreactive B and T cell responses driving RA. However, therapeutically targeting IDO2 has been challenging given the lack of small molecules that specifically inhibit IDO2 without also affecting the closely related IDO1. In this study, we develop a novel monoclonal antibody (mAb)-based approach to therapeutically target IDO2. Treatment with IDO2-specific mAb alleviated arthritis in two independent preclinical arthritis models, reducing autoreactive T and B cell activation and recapitulating the strong anti-arthritic effect of genetic IDO2 deficiency. Mechanistic investigations identified FcγRIIb as necessary for mAb internalization, allowing targeting of an intracellular antigen traditionally considered inaccessible to mAb therapy. Taken together, our results offer preclinical proof of concept for antibody-mediated targeting of IDO2 as a new therapeutic strategy to treat RA and other autoantibody-mediated diseases.

Peptide vaccination directed against IDO1-expressing immune cells elicits CD8+ and CD4+ T-cell-mediated antitumor immunity and enhanced anti-PD1 responses

Background

The tryptophan-catabolizing enzyme indoleamine 2,3-dioxygenase 1 (IDO1), which subverts T-cell immunity at multiple levels, is itself subject to inherent T-cell reactivity. This intriguing deviation from central tolerance has been interpreted as counterbalancing IDO1-mediated immunosuppression. Based on this hypothesis, clinical studies employing an IDO1 peptide-based vaccine approach for cancer treatment have been initiated, but there remains a pressing need to further investigate the immunological ramifications of stimulating the anti-IDO1 T-cell response in this manner.

Methods

CT26 colon carcinoma tumors were evaluated for expression of IDO1 protein by western blot analysis, immunofluorescence microscopy and flow cytometry. Mouse IDO1-derived peptides, predicted to bind either major histocompatibility complex (MHC) class I or II of the H2^d BALB/c strain, were emulsified in 50% Montanide for prophylactic or therapeutic vaccine treatment of CT26 tumor-bearing mice initiated either 7 days prior to or following tumor cell injection, respectively. In some therapeutic treatment experiments, administration of programmed cell death protein 1-binding antibody (anti-PD1 antibody) or epacadostat was concurrently initiated. Tumor size was determined by caliper measurements and comparative tumor growth suppression was assessed by longitudinal analyses of tumor growth data. For adoptive transfer, T cells from complete responder animals were isolated using paramagnetic beads and fluorescence-activated cell sorting.

Results

This study identifies mouse MHC class I-directed and II-directed, IDO1-derived peptides capable of eliciting antitumor responses, despite finding IDO1 expressed exclusively in tumor-infiltrating immune cells. Treatment of established tumors with anti-PD1 antibody and class I-directed but not class II-directed IDO1 peptide vaccines produced an enhanced antitumor response. Likewise, class I-directed and II-directed IDO1 peptides elicited an enhanced combinatorial response, suggesting distinct mechanisms of action. Consistent with this interpretation, adoptive transfer of isolated CD8⁺ T cells from class I and CD4⁺ T cells from class II peptide-vaccinated responder mice delayed tumor growth. The class II-directed response was completely IDO1-dependent while the class I-directed response included an IDO1-independent component consistent with antigen spread.

Conclusions

The in vivo antitumor effects demonstrated with IDO1-based vaccines via targeting of the tumor microenvironment highlight the utility of mouse models for further exploration and refinement of this novel vaccine-based approach to IDO1-directed cancer therapy and its potential to improve patient response rates to anti-PD1 therapy.

IDO2: A Pathogenic Mediator of Inflammatory Autoimmunity

Indoleamine 2,3-dioxygenase 2 (IDO2), a homolog of the better-studied tryptophan-catabolizing enzyme IDO1, is an immunomodulatory molecule with potential effects on various diseases including cancer and autoimmunity. Here, we review what is known about the direct connections between IDO2 and immune function, particularly in relationship to autoimmune inflammatory disorders such as rheumatoid arthritis and lupus. Accumulating evidence indicates that IDO2 acts as a pro-inflammatory mediator of autoimmunity, with a functional phenotype distinct from IDO1. IDO2 is expressed in antigen-presenting cells, including B cells and dendritic cells, but affects inflammatory responses in the autoimmune context specifically by acting in B cells to modulate T cell help in multiple model systems. Given that expression of IDO2 can lead to exacerbation of inflammatory responses, IDO2 should be considered a potential therapeutic target for autoimmune disorders.

Development and characterization of an organotypic model of Barrett's esophagus

Understanding the molecular and cellular processes underlying the development, maintenance, and progression of Barrett's esophagus (BE) presents an empirical challenge because there are no simple animal models and standard 2D cell culture can distort cellular processes. Here we describe a three-dimensional (3D) cell culture system to study BE. BE cell lines (CP-A, CP-B, CP-C, and CP-D) and esophageal squamous keratinocytes (EPC2) were cultured on a matrix consisting of esophageal fibroblasts and collagen. Comparison of growth and cytokeratin expression in the presence of all-trans retinoic acid or hydrochloric acid was made by immunohistochemistry and Alcian Blue staining to determine which treatments produced a BE phenotype of columnar cytokeratin expression in 3D culture. All-trans retinoic acid differentially affected the growth of BE cell lines in 3D culture. Notably, the non-dyplastic metaplasia-derived cell line (CP-A) expressed reduced squamous cytokeratins and enhanced columnar cytokeratins upon ATRA treatment. ATRA altered the EPC2 squamous cytokeratin profile towards a more columnar expression pattern. Cell lines derived from patients with high-grade dysplasia already expressed columnar cytokeratins and therefore did not show a systematic shift toward a more columnar phenotype with ATRA treatment. ATRA treatment, however, did reduce the squamoid-like multilayer stratification observed in all cell lines. As the first study to demonstrate long-term 3D growth of BE cell lines, we have determined that BE cells can be cultured for at least 3 weeks on a fibroblast/collagen matrix and that the use of ATRA causes a general reduction in squamous-like multilayered growth and an increase in columnar phenotype with the specific effects cell-line dependent.

Hemodynamic and metabolic changes induced by temporary clamping of the thoracic aorta

Numerous authors reported a significant deterioration of heart function induced by aortic cross-clamping. Nevertheless, the aorta has been clamped during various surgical procedures without any complication. We studied the hemodynamic and metabolic variations induced by 20 min thoracic aorta cross-clamping in 6 open-chest dogs. During clamping the most striking modifications were an increase in coronary blood flow of over 65%, an increase in cardiac work of over 77% and an increase in total peripheral resistances of over 68% compared to base values. No significant variations were found in the heart rate and cardiac index. Metabolic parameters, such as O2 consumption and lactate consumption increased significantly during the clamping period. The increase in lactate consumption and the progressive and continuous improvement in oxygenation indexes (lactate/pyruvate, redox potential, excess of lactate) proved the absence of any myocardial anoxia during this period. Within 15--30 min after declamping all hemodynamic and metabolic parameters reverted to values close to basal values. These data strongly suggest that the mammalian heart can tolerate this procedure satisfactorily for a limited period of time. In clinical settings, one should consider the base conditions of the cardiovascular system before transposing these conclusions.

An empirical test of the concomitantly variable codon hypothesis

A central assumption of models of molecular evolution, that each site in a sequence evolves independently of all other sites, lacks empirical support. We investigated the extent to which sites evolve codependently in triosephosphate isomerase (TIM), a ubiquitous glycolytic enzyme conserved in both structure and function. Codependencies among sites, or concomitantly variable codons (covarions), are evident from the reduced function and misfolding of hybrid TIM proteins. Although they exist, we find covarions are relatively rare, and closely related proteins are unlikely to have developed them. However, the potential for covarions increases with genetic distance so that highly divergent proteins may have evolved codependencies between many sites. The evolution of covarions undermines a key assumption in phylogenetics and calls into question our ability to disentangle ancient relationships among major taxonomic groups.

Computed radiography in neonatal intensive care

The Authors report their experience in the employment of a computerized digital radiographic system in Neonatal Intensive Care. The analog screen-film system is replaced by photosensitive imaging plates, scanned after X-ray exposure by a laser that releases the digital image, which can then be manipulated on computer work-stations. In a period of twelve months about 200 chest-abdomen X-ray examinations in Neonatal Intensive Care have been performed using this method with good technical and diagnostic results. The use of digital radiography in the neonatal area is of high interest: this system produces good quality images, there is a reduction in radiation dose and 'retakes', the system allows selective enhancement of different structures and their magnification.

Coronary blood flow and myocardial O2 consumption in hypertrophied cardiac muscle in dogs

In dogs with experimental cardiac hypertrophy in resting conditions, coronary blood flow and myocardial O2 consumption increased proportionately to the cardiac mass; coronary flow and O2 consumption per gram of myocardium, therefore, ranged within normal values. The coronary reserve, neasured as the percentage increase in the coronary blood flow from rest till peak flow during reactive hyperaemia, was noticeably reduced, because it was partially utilized, even at rest, and consequently the possibility of an increase in flow after exercise or stress was diminished.

Acute haemodynamic effects of ibopamine and dopamine on isovolumic relaxation

The effects of intraduodenal ibopamine (a new orally active inotropic agent claimed to have haemodynamic effects similar to dopamine) on isovolumic relaxation were monitored for 90 min in eight closed-chest anaesthetized dogs. Dopamine and epinine (ibopamine active metabolite) were also infused at graded doses. After 15 min, ibopamine (12 mg/kg) shortened the time constant of isovolumic relaxation, and increased stroke volume and mean aortic pressure. Peak positive dP/dt increased significantly only 10 min later. Heart rate did not change. Dopamine (10 micrograms/kg per min) similarly reduced the time constant, and increased stroke volume, mean aortic pressure, peak positive dP/dt and heart rate. Epinine (10 micrograms/kg per min) caused similar changes in peak positive dP/dt, stroke volume, mean aortic pressure, and accelerated time constant without raising the heart rate. Ibopamine and epinine therefore significantly improved the isovolumic relaxation phase, like dopamine, without however affecting the heart rate.