Aged neutrophils accumulate in lymphoid tissues from healthy elderly mice and infiltrate T- and B-cell zones.

The average age of the human population is rising, leading to an increasing burden of age-related diseases, including increased susceptibility to infection. However, immune function can decrease with age which could impact on processes that require a functional immune system. Aging is also characterized by chronic low-grade inflammation which could further impact immune cell function. While changes to neutrophils in blood during aging have been described, little is known in aging lymphoid organs. This study used female C57BL/6J mice comparing bone marrow (BM), spleen and lymph nodes from young mice aged 2-3 months (equivalent to 18 human years) with healthy elderly mice aged 22-24 months (equivalent to 60-70 human years). Neutrophil proportions increased in BM and secondary lymphoid organs of elderly mice relative to their younger counterparts and presented an atypical phenotype. Interestingly, neutrophils from elderly spleen and lymph nodes were long lived (with decreased apoptosis via Annexin V staining and increased proportion of BrdUneg mature cells) with splenic neutrophils also demonstrating a hypersegmented morphology. Furthermore, splenic neutrophils of elderly mice expressed a mixed phenotype with increased expression of activation markers, CD11b and ICAM-1, increased proinflammatory TNFα, yet increased anti-inflammatory transforming growth factor-beta. Elderly splenic architecture was compromised, as the marginal zone (required for clearing infections) was contracted. Moreover, neutrophils from elderly but not young mice accumulated in lymph node and splenic T- and B-cell zones. Overall, the expansion of functionally compromised neutrophils could contribute to increased susceptibility to infection observed in the elderly.

Lipid-laden partially-activated plasmacytoid and CD4(-)CD8α(+) dendritic cells accumulate in tissues in elderly mice.

BACKGROUND: Aging is associated with a decline in lymphocyte function however, little is known about dendritic cell (DC) subsets and aging. Aging is also associated with increasing circulating lipid levels and intracellular lipid accumulation modulates DC function. Whether age-associated increases in lipid levels influence DC biology is unknown. Thus, the effects of aging on DC subsets were assessed in vivo using young adult and elderly C57BL/6 J mice. RESULTS: Major age-related changes included increased CD11c(+) DC numbers in lymph nodes, spleens and livers, but not lungs, and significantly increased proportions of plasmacytoid (pDC) and CD4(-)CD8α(+) DCs in lymph nodes and livers. Other changes included altered pDC activation status (decreased CD40, increased MHC class-I and MHC class-II), increased lipid content in pDCs and CD4(-)CD8α(+) DCs, and increased expression of key mediators of lipid uptake including lipoprotein lipase, scavenger receptors (CD36, CD68 and LRP-1) in most tissues. CONCLUSIONS: Aging is associated with organ-specific numerical changes in DC subsets, and DC activation status, and increased lipid content in pDCs and CD4(-)CD8α(+) DCs. Up-regulation of lipoprotein lipase and scavenger receptors by lipid-rich pDCs and CD4(-)CD8α(+) DCs suggests these molecules contribute to DC lipid accumulation in the elderly. Lipid accumulation and modulated activation in pDCs and CD4(-)CD8α(+) DCs may contribute to the declining responses to vaccination and infection with age.

IL-2/CD40-driven NK cells install and maintain potency in the anti-mesothelioma effector/memory phase.

Murine and human mesothelioma tumors are susceptible to immunotherapy, particularly when immune adjuvants are delivered locally. We have shown that direct injection of IL-2 plus agonist anti-CD40 antibody induces regression of large mesothelioma tumors. These studies aimed to determine if NK cells contribute to IL-2/CD40 antibody-driven tumor eradication. We show that NK cells infiltrate developing mesothelioma tumors; however, their absence (in beige mice or in asialo GM(1) antibody-depleted C57BL/6J mice) does not alter tumor growth rates suggesting that they cannot function as effector cells in this microenvironment. Anti-CD40 antibody treatment did not alter the percent of NK cells in treated tumors or in draining lymph nodes (dLNs), and tumor resolution occurred in the absence of NK cells. However, a two-tumor model showed that NK cells contributed to CD40-driven systemic immunity leading to resolution of untreated distal tumors. IL-2 treatment led to increased proportions of NK cells in tumors and dLNs, and in the absence of NK cells, IL-2 lost its therapeutic effect. In contrast, the absence of NK cells did not reduce the anti-tumor activity of the IL-2/anti-CD40 antibody combination yet tumors recurred in NK-deficient mice and > 37% of tumor cell re-challenged mice were unable to provide protection, implying insufficient memory. Furthermore, untreated distal tumors in NK-depleted mice were less readily cured than in immunologically intact mice. These data show that NK cells infiltrate mesothelioma tumors, which, after local IL-2 and/or anti-CD40 antibody treatment, provide help for the acquisition and/or maintenance of systemic immunity and long-term effector/memory responses.

Prognostic role of immune environment in luminal B early breast cancer.

The importance of the immune microenvironment in triple negative and HER2-amplified breast cancer (BC) is well-established; less is known about the immune environment in luminal breast cancers. We aimed to assess for the impact of immune biomarkers on BC outcome in a group of luminal B patients with archived tissue and annotated clinical information. Patients with early breast cancer (EBC) treated in a single institution over a 14-year period, with prospectively collected data were included. Luminal B EBC patients were identified and defined into three cohorts: A: grade 2 or 3, ER & PR positive, HER2-negative; B: Any grade, ER positive, PR and HER2-negative (Ki67 ≥ 14% in cohorts A & B); and C: Any grade, ER or PR positive, HER2-positive. Within each cohort, patients with a relapsed BC event (R) were compared on a 1:1 basis with a control patient (C) who remained disease-free, balanced for key characteristics in an effort to balance the contribution of each clinical group to outcome. Archival breast, involved and uninvolved axillary nodes were assessed by immunohistochemistry for biomarkers identifying effector and suppressor immune cells, and compared between R and C. In total, 120 patients were included (80, 22, and 18 patients in cohorts A, B, and C, respectively). R were 1.5 years older (p = 0.016), with all other characteristics being balanced. Overall, there were no statistically significant differences in immune biomarkers in breast or nodal tissue of R and C. However, there was a trend toward higher levels of TILs in breast tumors of C, while GAL-9 was consistently expressed on lymphocytes and tumor cells in all breast and nodes of C and was absent from all tissues of R. These trends in checkpoint molecule expression deserve further research.

Intratumoral interleukin-2/agonist CD40 antibody drives CD4+ -independent resolution of treated-tumors and CD4+ -dependent systemic and memory responses.

Targeting interleukin-2 (IL-2) and/or agonist anti-CD40 antibody (Ab) into tumors represents an effective vaccination strategy that avoids systemic toxicity and resolves treated-site tumors. Here, we examined IL-2 and/or anti-CD40 Ab-driven local versus systemic T cell function and the installation of T cell memory. Single tumor studies showed that IL-2 induced a potent CD4+ and CD8+ T cell response that was limited to the draining lymph node and treated-site tumor, and lymph node tumor-specific CD8+ T cells did not upregulate CD44. A two-tumor model showed that while IL-2-treated-site tumors resolved, distal tumors continued to grow, implying limited systemic immunity. In contrast, anti-CD40 Ab treatment with or without IL-2 expanded the systemic T cell response to non-draining lymph nodes, and distal tumors resolved. Tumor-specific T cells in lymph nodes of anti-CD40 Ab ± IL-2-treated mice upregulated CD44, demonstrating activation and transition to effector/memory migratory cells. While CD40-activated CD4+ T cells were not required for eradicating treated-site tumors, they, plus CD8+ T cells, were crucial for removing distal tumors. Rechallenge/depletion experiments showed that the effector/memory phase required the presence of previously CD40/IL-2-activated CD4+ and CD8+ T cells to prevent recurrence. These novel findings show that different T cell effector mechanisms can operate for the eradication of local treated-site tumors versus untreated distal tumors and that signaling through CD40 generates a whole of body, effector/memory CD4+ and CD8+ T cell response that is amplified and prolonged via IL-2. Thus, successful immunotherapy needs to generate collaborating CD4+ and CD8+ T cells for a complete long-term protective cure.

Chemotherapy broadens the range of tumor antigens seen by cytotoxic CD8(+) T cells in vivo.

Cytotoxic chemotherapies may expose the immune system to high levels of tumor antigens and expand the CD8(+) T-cell response to include weak or subdominant antigens. Here, we evaluated the in vivo CTL response to tumor antigens using a murine mesothelioma tumor cell line transfected with a neotumor antigen, ovalbumin, that contains a known hierarchy of epitopes for MHC class I molecules. We show that as tumors progress, effector CTLs are generated in vivo that focus on the dominant epitope SIINFEKL, although a weak response was seen to one (KVVRFDKL) subdominant epitope. These CTLs did not prevent tumor growth. Cisplatin treatment slowed tumor growth, slightly improved in vivo SIINFEKL presentation to T cells and reduced SIINFEKL-CTL activity. However, the CTL response to KVVRFDKL was amplified, and a response to another subdominant epitope, NAIVFKGL, was revealed. Similarly, gemcitabine cured most mice, slightly enhanced SIINFEKL presentation, reduced SIINFEKL-CTL activity yet drove a significant CTL response to NAIVFKGL, but not KVVRFDKL. These NAIVFKGL-specific CTLs secreted IFNγ and proliferated in response to in vitro NAIVFKGL stimulation. IL-2 treatment during chemotherapy refocused the response to SIINFEKL and simultaneously degraded the cisplatin-driven subdominant CTL response. These data show that chemotherapy reveals weaker tumor antigens to the immune system, a response that could be rationally targeted. Furthermore, while integrating IL-2 into the chemotherapy regimen interfered with the hierarchy of the response, IL-2 or other strategies that support CTL activity could be considered upon completion of chemotherapy.

Aging Leads to Increased Monocytes and Macrophages With Altered CSF-1 Receptor Expression and Earlier Tumor-Associated Macrophage Expansion in Murine Mesothelioma.

Increased cancer incidence occurs with the emergence of immunosenescence, highlighting the indispensability of the immune system in preventing cancer and its dysregulation with aging. Tumor-associated macrophages (TAMs) are often present in high numbers and are associated with poor clinical outcomes in solid cancers, including mesothelioma. Monocytes and macrophages from the bone marrow and spleen can respond to tumor-derived factors, such as CSF-1, and initiation of the CSF-1R signaling cascade results in their proliferation, differentiation, and migration to the tumor. Age-related changes occur in monocytes and macrophages in terms of numbers and function, which in turn can impact tumor initiation and progression. Whether this is due to changes in CSF-1R expression with aging is currently unknown and was investigated in this study. We examined monocytes and macrophages in the bone marrow and spleen during healthy aging in young (3-4 months) and elderly (20-24 months) female C57BL/6J mice. Additionally, changes to these tissues and in TAMs were examined during AE17 mesothelioma tumor growth. Healthy aging resulted in an expansion of Ly6Chigh monocytes and macrophages in the bone marrow and spleen. CSF-1R expression levels were reduced in elderly splenic macrophages only, suggesting differences in CSF-1R signaling between both cell type and tissue site. In tumor-bearing mice, Ly6Chigh monocytes increased with tumor growth in the spleen in the elderly and increased intracellular CSF-1R expression occurred in bone marrow Ly6Chigh monocytes in elderly mice bearing large tumors. Age-related changes to bone marrow and splenic Ly6Chigh monocytes were reflected in the tumor, where we observed increased Ly6Chigh TAMs earlier and expansion of Ly6Clow TAMs later during AE17 tumor growth in the elderly compared to young mice. F4/80high TAMs increased with tumor growth in both young and elderly mice and were the largest subset of TAMs in the tumor. Together, this suggests there may be a faster transition of Ly6Chigh towards F4/80high TAMs with aging. Amongst TAM subsets, expression of CSF-1R was lowest in F4/80high TAMs, however Ly6Clow TAMs had higher intracellular CSF-1R expression. This suggests downstream CSF-1R signaling may vary between macrophage subsets, which can have implications towards CSF-1R blockade therapies targeting macrophages in cancer.

The STING agonist, DMXAA, reduces tumor vessels and enhances mesothelioma tumor antigen presentation yet blunts cytotoxic T cell function in a murine model.

We assessed the murine Stimulator of Interferon Genes (STING) agonist, DMXAA, for anti-mesothelioma potential using the AE17-sOVA model that expresses ovalbumin (OVA) as a neo tumor antigen. Dose response experiments alongside testing different routes of administration identified a safe effective treatment regimen that induced 100% cures in mice with small or large tumors. Three doses of 25mg/kg DMXAA given intra-tumorally every 9 days induced tumor regression and long-term survival (>5 months). Re-challenge experiments showed that tumor-free mice developed protective memory. MTT and propidium-iodide assays showed that DMXAA exerted direct cytotoxic effects at doses >1mg/ml on the murine AE17 and AB1 mesothelioma cell lines. In-vivo studies using a CFSE-based in-vivo proliferation assay showed that DMXAA improved tumor-antigen presentation in tumor-draining lymph nodes, evidenced by OVA-specific OT-1 T cells undergoing more divisions. An in-vivo cytotoxic T lymphocyte (CTL) assay showed that DMXAA blunted the lytic quality of CTLs recognizing the dominant (SIINFEKL) and a subdominant (KVVRFDKL) OVA epitopes. DMXAA reduced tumor vessel size in-vivo and although the proportion of T cells infiltrating tumors reduced, the proportion of tumor-specific T cells increased. These data show careful dosing and treatment protocols reduce mesothelioma cell viability and modulate tumor vessels such that tumor-antigen specific CTLs access the tumor site. However, attempts to enhance DMXAA-induced anti-tumor responses by combination with an agonist anti-CD40 antibody or IL-2 reduced efficacy. These proof-of-concept data suggest that mesothelioma patients could benefit from treatment with a STING agonist, but combination with immunotherapy should be cautiously undertaken.

Deliberately provoking local inflammation drives tumors to become their own protective vaccine site.

Anti-cancer immunotherapies aim to generate resolution of all existing tumors, including inaccessible ones, and provide long-term protection against recurrence. This is rarely achieved. Thus, we aimed to determine if the tumor microenvironment could be turned into a potent 'self'-vaccine site. Our target was to eradicate larger tumor burdens. Our models respond to single-agent immunotherapies; however, they fail at a precisely defined 'cut-off' tumor burden. Thus, this system was used to define the immune mechanisms required to mediate regression of larger tumors that are resistant to mono-immunotherapies. We report that direct injection of IL-2 with agonist anti-CD40 antibody into the tumor bed resulted in permanent resolution of treated and untreated distal tumors. Tumor-infiltrating CD8(+) T cells and neutrophils collaborated to eradicate treated tumors, IFNgamma was not critical and protective memory was preserved. This approach relied only on tumor antigens expressed within the tumor microenvironment. It also avoided systemic toxicities, did not require chemotherapy or surgery and is clinically useful because only one tumor site has to be accessible for treatment. We conclude that provoking intra-tumoral inflammation skews the tumor microenvironment from tumorigenic to immunogenic, resulting in the resolution of treated and untreated distal tumors, as well long-term protective memory.

CD8+ cytotoxic T cell responses to dominant tumor-associated antigens are profoundly weakened by aging yet subdominant responses retain functionality and expand in response to chemotherapy.

Increasing life expectancy is associated with increased cancer incidence, yet the effect of cancer and anti-cancer treatment on elderly patients and their immune systems is not well understood. Declining T cell function with aging in response to infection and vaccination is well documented, however little is known about aged T cell responses to tumor antigens during cancer progression or how these responses are modulated by standard chemotherapy. We examined T cell responses to cancer in aged mice using AE17sOVA mesothelioma in which ovalbumin (OVA) becomes a 'spy' tumor antigen containing one dominant (SIINFEKL) and two subdominant (KVVRFDKL and NAIVFKGL) epitopes. Faster progressing tumors in elderly (22-24 months, cf. 60-70 human years) relative to young (2-3 months, human 15-18 years) mice were associated with increased pro-inflammatory cytokines and worsened cancer cachexia. Pentamer staining and an in-vivo cytotoxic T lymphocyte (CTL) assay showed that whilst elderly mice generated a greater number of CD8+ T cells recognizing all epitopes, they exhibited a profound loss of function in their ability to lyse targets expressing the dominant, but not subdominant, epitopes compared to young mice. Chemotherapy was less effective and more toxic in elderly mice however, similar to young mice, chemotherapy expanded CTLs recognizing at least one subdominant epitope in tumors and draining lymph nodes, yet treatment efficacy still required CD8+ T cells. Given the significant dysfunction associated with elderly CTLs recognizing dominant epitopes, our data suggest that responses to subdominant tumor epitopes may become important when elderly hosts with cancer are treated with chemotherapy.

Microenvironment-Dependent Gradient of CTL Exhaustion in the AE17sOVA Murine Mesothelioma Tumor Model.

The immune system, and in particular, cytotoxic CD8+ T cells (CTLs), plays a vital part in the prevention and elimination of tumors. In many patients, however, CTL-mediated tumor killing ultimately fails in the clearance of cancer cells resulting in disease progression, in large part due to the progression of effector CTL into exhausted CTL. While there have been major breakthroughs in the development of CTL-mediated "reinvigoration"-driven immunotherapies such as checkpoint blockade therapy, there remains a need to better understand the drivers behind the development of T cell exhaustion. Our study highlights the unique differences in T cell exhaustion development in tumor-specific CTL which arises over time in a mouse model of mesothelioma. Importantly, we also show that peripheral tumor-specific T cells have a unique expression profile compared to exhausted tumor-infiltrating CTL at a late-stage of tumor progression in mice. Together, these data suggest that greater emphasis should be placed on understanding contributions of individual microenvironments in the development of T cell exhaustion.

Photophysical and biological investigation of phenol substituted rhenium tetrazolato complexes.

The synthesis, structural and photophysical characterisation of four tricarbonyl rhenium(i) complexes bound to 1,10-phenanthroline and a tetrazolato ancillary ligand are reported. The complexes are differentiated by the nature (hydroxy or methoxy) and position (meta or para) of the substituent attached to the phenyl ring in conjugation to the tetrazole ring. The complexes exhibit phosphorescence emission from triplet charge transfer excited states, with the maxima around 600 nm, excited state lifetime decays in the 200-300 ns range, and quantum yield values of 4-6% in degassed acetonitrile solutions. The nature and position of the substituent does not significantly affect the photophysical properties, which remain unchanged even after deprotonation of the hydroxide group on the phenol ring. The interpretation of the photophysical data was further validated by resonance Raman spectroscopy and time-dependent density functional theory calculations. All the complexes are internalised within cells, albeit to variable degrees. As highlighted by a combination of flow cytometry and confocal microscopy, the species display diffuse cytoplasmic localisation except for the complex with the hydroxy functional group at the para position, which reveals lower accumulation in cells and more pronounced punctate staining. Overall, the complexes displayed low levels of cytotoxicity.

The Regulatory Status Adopted by Lymph Node Dendritic Cells and T Cells During Healthy Aging Is Maintained During Cancer and May Contribute to Reduced Responses to Immunotherapy.

Aging is associated with an increased incidence of cancer. One contributing factor could be modulation of immune cells responsible for anti-tumor responses, such as dendritic cells (DCs) and T cells. These immunological changes may also impact the efficacy of cancer immunotherapies in the elderly. The effects of healthy aging on DCs and T cells, and their impact on anti-mesothelioma immune responses, had not been reported. This study examined DCs and T cells in young (2-5 months; equivalent to 16-26 human years) and elderly (20-24 months; equivalent to 60-70 human years) healthy and mesothelioma-bearing C57BL/6J mice. During healthy aging, elderly lymph nodes adopted a regulatory profile, characterized by: (i) increased plasmacytoid DCs, (ii) increased expression of the adenosine-producing enzyme CD73 on CD11c+ cells, and (iii) increased expression of multiple regulatory markers (including CD73, the adenosine A2B receptor, CTLA-4, PD-1, ICOS, LAG-3, and IL-10) on CD8+ and CD4+ T cells, compared to lymph nodes from young mice. Although mesotheliomas grew faster in elderly mice, the increased regulatory status observed in healthy elderly lymph node DCs and T cells was not further exacerbated. However, elderly tumor-bearing mice demonstrated reduced MHC-I, MHC-II and CD80 on CD11c+ cells, and decreased IFN-γ by CD8+ and CD4+ T cells within tumors, compared to young counterparts, implying loss of function. An agonist CD40 antibody based immunotherapy was less efficient at promoting tumor regression in elderly mice, which may be due to: (i) failure of elderly CD8+ T cells to up-regulate perforin, and (ii) increased expression of multiple regulatory markers on CD11c+ cells and T cells in elderly tumor-draining lymph nodes (including CD73, PD-1, ICOS, LAG-3, and TGF-ß). Our findings suggest that checkpoint blockade may improve responses to immunotherapy in elderly hosts with mesothelioma, and warrants further investigation.

Macrophage Depletion in Elderly Mice Improves Response to Tumor Immunotherapy, Increases Anti-tumor T Cell Activity and Reduces Treatment-Induced Cachexia.

Most cancers emerge in the elderly, including lung cancer and mesothelioma, yet the elderly remain an underrepresented population in pre-clinical cancer studies and clinical trials. The immune system plays a critical role in the effectiveness of many anti-cancer therapies in young hosts via tumor-specific T cells. However, immunosuppressive macrophages can constitute up to 50% of the tumor burden and impair anti-tumor T cell activity. Altered macrophage phenotype and function during aging may further impact anti-tumor T cell responses. Yet, the impact of macrophages on anti-tumor T cell responses and immunotherapy in the elderly is unknown. Therefore, we examined macrophages and their interaction with T cells in young (3 months) and elderly (20-24 months) AE17 mesothelioma-bearing female C57BL/6J mice during tumor growth. Mesothelioma tumors grew faster in elderly compared with young mice, and this corresponded with an increase in tumor-associated macrophages. During healthy aging, macrophages increase in bone marrow and spleens suggesting that these sites have an increased potential to supply cancer-promoting macrophages. Interestingly, in tumor-bearing mice, bone marrow macrophages increased proliferation whilst splenic macrophages had reduced proliferation in elderly compared with young mice, and macrophage depletion using the F4/80 antibody slowed tumor growth in young and elderly mice. We also examined responses to treatment with intra-tumoral IL-2/anti-CD40 antibody immunotherapy and found it was less effective in elderly (38% tumor regression) compared to young mice (90% regression). Tumor-bearing elderly mice decreased in vivo anti-tumor cytotoxic T cell activity in tumor draining lymph nodes and spleens. Depletion of macrophages using F4/80 antibody in elderly, but not young mice, improved IL-2/anti-CD40 immunotherapy up to 78% tumor regression. Macrophage depletion also increased in vivo anti-tumor T cell activity in elderly, but not young mice. All the tumor-bearing elderly (but not young) mice had decreased body weight (i.e., exhibited cachexia), which was greatly exacerbated by immunotherapy; whereas macrophage depletion prevented this immunotherapy-induced cachexia. These studies strongly indicate that age-related changes in macrophages play a key role in driving cancer cachexia in the elderly, particularly during immunotherapy, and sabotage elderly anti-tumor immune responses.

Elderly dendritic cells respond to LPS/IFN-γ and CD40L stimulation despite incomplete maturation.

There is evidence that dendritic cells (DCs) undergo age-related changes that modulate their function with their key role being priming antigen-specific effector T cells. This occurs once DCs develop into antigen-presenting cells in response to stimuli/danger signals. However, the effects of aging on DC responses to bacterial lipopolysaccharide (LPS), the pro-inflammatory cytokine interferon (IFN)-γ and CD40 ligand (CD40L) have not yet been systematically evaluated. We examined responses of blood myeloid (m)DC1s, mDC2s, plasmacytoid (p)DCs, and monocyte-derived DCs (MoDCs) from young (21-40 years) and elderly (60-84 years) healthy human volunteers to LPS/IFN-γ or CD40L stimulation. All elderly DC subsets demonstrated comparable up-regulation of co-stimulatory molecules (CD40, CD80 and/or CD86), intracellular pro-inflammatory cytokine levels (IFN-γ, tumour necrosis factor (TNF)-α, IL-6 and/or IL-12), and/or secreted cytokine levels (IFN-α, IFN-γ, TNF-α, and IL-12) to their younger counterparts. Furthermore, elderly-derived LPS/IFN-γ or CD40L-activated MoDCs induced similar or increased levels of CD8+ and CD4+ T cell proliferation, and similar T cell functional phenotypes, to their younger counterparts. However, elderly LPS/IFN-γ-activated MoDCs were unreliable in their ability to up-regulate chemokine (IL-8 and monocyte chemoattractant protein (MCP)-1) and IL-6 secretion, implying an inability to dependably induce an inflammatory response. A key age-related difference was that, unlike young-derived MoDCs that completely lost their ability to process antigen, elderly-derived MoDCs maintained their antigen processing ability after LPS/IFN-γ maturation, measured using the DQ-ovalbumin assay; this response implies incomplete maturation that may enable elderly DCs to continuously present antigen. These differences may impact on the efficacy of anti-pathogen and anti-tumour immune responses in the elderly.

Modulation of dendritic cell and T cell cross-talk during aging: The potential role of checkpoint inhibitory molecules.

Dendritic cells (DCs) undergo continuous changes throughout life, and there is evidence that elderly DCs have a reduced capacity to stimulate T cells, which may contribute to impaired anti-tumour immune responses in elderly people with cancer. Changes in checkpoint inhibitory molecules/pathways during aging may be one mechanism that impairs the ability of elderly DCs to activate T cells. However, little is currently known regarding the combined effects of aging and cancer on DC and T cell inhibitory molecules/pathways. In this review, we discuss our current understanding of the influence of aging and cancer on key DC and T cell inhibitory molecules/pathways, the potential underlying cellular and molecular mechanisms contributing to their modulation, and the possibility of therapeutically targeting inhibitory molecules in elderly cancer patients.

A review of the importance of immune responses in luminal B breast cancer.

Historically, the immune environment was not considered an important target for breast cancer treatment. However, the association of lymphocytic infiltrates in triple negative and HER-2 over-amplified breast cancer subtypes with better outcomes, has provoked interest in evaluating the role of the immune system in the luminal B subtype that accounts for 39% of breast cancers and has a poor patient prognosis. It is unknown which immunosuppressive cell types or molecules (e.g., checkpoint molecules) are relevant, or where measurement is most informative. We hypothesize that a profound immunosuppressive tumor and/or lymph node milieu is prognostic and impacts on responses to therapies.

Aging and cancer: The role of macrophages and neutrophils.

Impaired immune function has been implicated in the declining health and higher incidence of cancer in the elderly. However, age-related changes to immunity are not completely understood. Neutrophils and macrophages represent the first line of defence yet their ability to phagocytose pathogens decrease with aging. Cytotoxic T lymphocytes are critical in eliminating tumors, but T cell function is also compromised with aging. T cell responses can be regulated by macrophages and may depend on the functional phenotype macrophages adopt in response to microenvironmental signals. This can range from pro-inflammatory, anti-tumorigenic M1 to anti-inflammatory, pro-tumorigenic M2 macrophages. Macrophages in healthy elderly adipose and hepatic tissue exhibit a more pro-inflammatory M1 phenotype compared to young hosts whilst immunosuppressive M2 macrophages increase in elderly lymphoid tissues, lung and muscle. These M2-like macrophages demonstrate altered responses to stimuli. Recent studies suggest that neutrophils also regulate T cell function and, like macrophages, neutrophil function is modulated with aging. It is possible that age-modified tissue-specific macrophages and neutrophils contribute to chronic low-grade inflammation that is associated with dysregulated macrophage-mediated immunosuppression, which together are responsible for development of multiple pathologies, including cancer. This review discusses recent advances in macrophage and neutrophil biology in healthy aging and cancer.

Human mesothelioma induces defects in dendritic cell numbers and antigen-processing function which predict survival outcomes.

Mesothelioma is an almost invariably fatal tumor with chemotherapy extending survival by a few months. One immunotherapeutic strategy is to target dendritic cells (DCs), key antigen-presenting cells involved in antigen presentation, to induce antigen-specific T cell responses. However, DC-targeting will only be effective if DCs are fit-for-purpose, and the functional status of DCs in mesothelioma patients was not clear. We found that mesothelioma patients have significantly decreased numbers of circulating myeloid (m)DC1 cells, mDC2 cells and plasmacytoid (p)DCs relative to healthy age and gender-matched controls. Blood monocytes from patients could not differentiate into immature monocyte-derived DCs (MoDCs), indicated by a significantly reduced ability to process antigen and reduced expression of costimulatory (CD40, CD80 and CD86) and MHC (HLA-DR) molecules, relative to controls. Activation of mesothelioma-derived MoDCs with LPS+/-IFNγ generated partially mature MoDCs, evident by limited upregulation of the maturation marker, CD83, and the costimulatory markers. Attempts to rescue mesothelioma-derived DC function using CD40Ligand(L) also failed, indicated by maintenance of antigen-processing capacity and limited upregulation of CD40, CD83, CD86 and HLA-DR. These data suggest that mesothelioma patients have significant numerical and functional DC defects and that their reduced capacity to process antigen and reduced expression of costimulatory molecules could induce anergized/tolerized T cells. Nonetheless, survival analyses revealed that individuals with mesothelioma and higher than median levels of mDC1s and/or whose MoDCs matured in response to LPS, IFNγ or CD40L lived longer, implying their selection for DC-targeting therapy could be promising especially if combined with another treatment modality.

Murine mesothelioma induces locally-proliferating IL-10(+)TNF-α(+)CD206(-)CX3CR1(+) M3 macrophages that can be selectively depleted by chemotherapy or immunotherapy.

We used a murine model to monitor changes to myeloid cell subsets, i.e., myeloid-derived suppressor cells (MDSCs), M1 macrophages that secrete pro-inflammatory cytokines and express CD40 and CD80 and suppressive M2 macrophages that secrete anti-inflammatory cytokines and express CD206 and CX3CR1, during mesothelioma progression and during chemotherapy or immunotherapy-induced tumor regression. In vitro studies showed that mesothelioma-conditioned media generated CD206(-)CX3CR1(+)MCP-1(+)TGF-ß(+) macrophages that induced T cell proliferation but prevented T cell IFNγ production. In vivo studies showed that co-inoculation of macrophages with mesothelioma cells led to faster tumor growth, and depleting macrophages using anti-F4/80 antibody induced tumor regression. Flow cytometry revealed increasing levels of different suppressive myeloid cells in lymphoid organs: MDSCs dominated bone marrow (BM) and spleens, M2 macrophages dominated tumor-draining lymph nodes (DLN) and a mixed IL-10(+)TNF-α(+)CD206(-)CX3CR1(+) M1/M2 (M3) macrophage subset dominated the mesothelioma microenvironment. Ki67 staining and cell cycle analysis showed that tumor-associated M1 and M3, but not M2, macrophages were proliferating in situ, with M1 cells arrested in the G1 phase while M3 cells progressed to mitosis. Immunohistochemistry showed that M1 and M3 cells were co-located supporting the hypothesis that M1 cells transition to M3 cells during proliferation. Gemcitabine reduced tumor-associated M3 and MDSCs, but not M2 macrophages, the latter likely contributing to the tumor outgrowth seen following treatment cessation. In contrast, IL-2/agonist anti-CD40 antibody therapy reduced M3 cells and polarized macrophages into M1 cells coinciding with tumor regression. These data show that myeloid cells, particularly M3 cells, represent a therapeutic target for the generation of antitumor immunity.