How neoplastic cells respond to therapy is not solely dependent on the complexity of the genomic aberrations they harbor but is also regulated by numerous dynamic properties of the tumor ...microenvironment. Identifying and targeting critical pathways that improve therapeutic efficacy by bolstering anti-tumor immune responses holds great potential for improving outcomes and impacting long-term patient survival. Macrophages are key regulators of homeostatic tissue and tumor microenvironments. Therefore, therapeutics impacting macrophage presence and/or bioactivity have shown promise in preclinical models and are now being evaluated in the clinic. This review discusses the molecular/cellular pathways identified so far whereby macrophages mediate therapeutic responses.
Mutationally corrupted cancer (stem) cells are the driving force of tumor development and progression. Yet, these transformed cells cannot do it alone. Assemblages of ostensibly normal tissue and ...bone marrow-derived (stromal) cells are recruited to constitute tumorigenic microenvironments. Most of the hallmarks of cancer are enabled and sustained to varying degrees through contributions from repertoires of stromal cell types and distinctive subcell types. Their contributory functions to hallmark capabilities are increasingly well understood, as are the reciprocal communications with neoplastic cancer cells that mediate their recruitment, activation, programming, and persistence. This enhanced understanding presents interesting new targets for anticancer therapy.
Tumor-associated macrophages (TAMs) constitute a plastic and heterogeneous cell population of the tumor microenvironment (TME) that can account for up to 50% of some solid neoplasms. Most often, TAMs ...support disease progression and resistance to therapy by providing malignant cells with trophic and nutritional support. However, TAMs can mediate antineoplastic effects, especially in response to pharmacological agents that boost their phagocytic and oxidative functions. Thus, TAMs and their impact on the overall metabolic profile of the TME have a major influence on tumor progression and resistance to therapy, de facto constituting promising targets for the development of novel anticancer agents. Here, we discuss the metabolic circuitries whereby TAMs condition the TME to support tumor growth and how such pathways can be therapeutically targeted.
Vitale et al. discuss the metabolic circuitries whereby tumor-associated macrophages condition their microenvironment to support the cancer growth, metastatic dissemination and resistance to treatment, and how such pathways can be therapeutically targeted.
The Basis of Oncoimmunology Palucka, A. Karolina; Coussens, Lisa M.
Cell,
03/2016, Volume:
164, Issue:
6
Journal Article
Peer reviewed
Open access
Cancer heterogeneity, a hallmark enabling clonal survival and therapy resistance, is shaped by active immune responses. Antigen-specific T cells can control cancer, as revealed clinically by ...immunotherapeutics such as adoptive T-cell transfer and checkpoint blockade. The host immune system is thus a powerful tool that, if better harnessed, could significantly enhance the efficacy of cytotoxic therapy and improve outcomes for cancer sufferers. To realize this vision, however, a number of research frontiers must be tackled. These include developing strategies for neutralizing tumor-promoting inflammation, broadening T-cell repertoires (via vaccination), and elucidating the mechanisms by which immune cells organize tumor microenvironments to regulate T-cell activity. Such efforts will pave the way for identifying new targets for combination therapies that overcome resistance to current treatments and promote long-term cancer control.
Developing combination therapies with curative potential that harness the power of the immune system to treat cancer will require understanding the diverse mechanisms underlying the cross-talk between immune cells, cancer cells and the tumor microenvironment.
There have been substantial advances in cancer diagnostics and therapies in the past decade. Besides chemotherapeutic agents and radiation therapy, approaches now include targeting cancer ...cell—intrinsic mediators linked to genetic aberrations in cancer cells, in addition to cancer cell—extrinsic pathways, especially those regulating vascular programming of solid tumors. More recently, immunotherapeutics have entered the clinic largely on the basis of the recognition that several immune cell subsets, when chronically activated, foster tumor development. Here, we discuss clinical and experimental studies delineating protumorigenic roles for immune cell subsets that are players in cancer-associated inflammation. Some of these cells can be targeted to reprogram their function, leading to resolution, or at least neutralization, of cancer-promoting chronic inflammation, thereby facilitating cancer rejection.
Of the multiple unique stromal cell types common to solid tumors, tumor-associated macrophages (TAMs) are significant for fostering tumor progression. The protumor properties of TAMs derive from ...regulation of angiogenic programming, production of soluble mediators that support proliferation, survival and invasion of malignant cells, and direct and indirect suppression of cytotoxic T cell activity. These varied activities are dependent on the polarization state of TAMs that is regulated in part by local concentrations of cytokines and chemokines, as well as varied interactions of TAMs with normal and degraded components of the extracellular matrix. Targeting molecular pathways regulating TAM polarization holds great promise for anticancer therapy.
Functionally significant proteins expressed by tumor macrophages have emerged as promising anti-cancer targets. In this issue of Cancer Cell, Sun et al. identify two FDA-approved agents that together ...safely reprogram tumor macrophages into potent anti-tumor effectors, demonstrating the power of engaging both immune system arms to fight cancer.
Functionally significant proteins expressed by tumor macrophages have emerged as promising anti-cancer targets. In this issue of Cancer Cell, Sun et al. identify two FDA-approved agents that together safely reprogram tumor macrophages into potent anti-tumor effectors, demonstrating the power of engaging both immune system arms to fight cancer.
The roles of tumor-associated macrophages (TAMs) and circulating monocytes in human cancer are poorly understood. Here, we show that monocyte subpopulation distribution and transcriptomes are ...significantly altered by the presence of endometrial and breast cancer. Furthermore, TAMs from endometrial and breast cancers are transcriptionally distinct from monocytes and their respective tissue-resident macrophages. We identified a breast TAM signature that is highly enriched in aggressive breast cancer subtypes and associated with shorter disease-specific survival. We also identified an auto-regulatory loop between TAMs and cancer cells driven by tumor necrosis factor alpha involving SIGLEC1 and CCL8, which is self-reinforcing through the production of CSF1. Together these data provide direct evidence that monocyte and macrophage transcriptional landscapes are perturbed by cancer, reflecting patient outcomes.
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•Cancer alters circulating monocytic populations and their transcriptomes•Tumor-associated macrophages show tissue-specific programming•Tumor-associated macrophages’ gene signature correlates with poor clinical outcome•Tumor-associated macrophages enhance cancer cells malignancy through CCL8
Cassetta et al. identify a breast cancer tumor-associated macrophage (TAM) transcriptome that is different from those of monocytes and tissue-resident macrophages, and which is associated with shorter disease-specific survival, and they demonstrate crosstalk between tumor cells and TAMs via SIGLEC1, CCL8, and CSF1.
Blockade of colony-stimulating factor-1 (CSF-1) limits macrophage infiltration and improves response of mammary carcinomas to chemotherapy. Herein we identify interleukin (IL)-10 expression by ...macrophages as the critical mediator of this phenotype. Infiltrating macrophages were the primary source of IL-10 within tumors, and therapeutic blockade of IL-10 receptor (IL-10R) was equivalent to CSF-1 neutralization in enhancing primary tumor response to paclitaxel and carboplatin. Improved response to chemotherapy was CD8+ T cell-dependent, but IL-10 did not directly suppress CD8+ T cells or alter macrophage polarization. Instead, IL-10R blockade increased intratumoral dendritic cell expression of IL-12, which was necessary for improved outcomes. In human breast cancer, expression of IL12A and cytotoxic effector molecules were predictive of pathological complete response rates to paclitaxel.
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•Macrophages are the primary source of IL-10 in mammary carcinomas•IL-10 receptor blockade improves primary tumor response to paclitaxel•IL-10 suppresses expression of IL-12 by tumor dendritic cells during chemotherapy•IL12A expression correlates with response to chemotherapy in breast cancer patients
Ruffell et al. show that tumor-infiltrating macrophages produce IL-10, which limits cytotoxic T cell responses by suppressing the expression of IL-12 by intratumoral dendritic cell and, thus, provides a mechanism for the effect of CSF-1 blockade in breast cancer.
Immune checkpoint inhibitors (ICIs) have revolutionized the clinical management of multiple tumours. However, only a few patients respond to ICIs, which has generated considerable interest in the ...identification of resistance mechanisms. One such mechanism reflects the ability of various oncogenic pathways, as well as stress response pathways required for the survival of transformed cells (a situation commonly referred to as 'non-oncogene addiction'), to support tumour progression not only by providing malignant cells with survival and/or proliferation advantages, but also by establishing immunologically 'cold' tumour microenvironments (TMEs). Thus, both oncogene and non-oncogene addiction stand out as promising targets to robustly inflame the TME and potentially enable superior responses to ICIs.
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