γ-Irradiated cancer cells promote tumor growth by activation of Toll-like receptor 1-mediated inducible nitric oxide synthase in macrophages

Toll-Like Receptors and the Response to Radiotherapy in Solid Tumors: Challenges and Opportunities

Toll-like receptors (TLRs) are indispensable for the activation, maintenance and halting of immune responses. TLRs can mediate inflammation by recognizing molecular patterns in microbes (pathogen-associated molecular patterns: PAMPs) and endogenous ligands (danger-associated molecular patterns: DAMPs) released by injured or dead cells. For this reason, TLR ligands have attracted much attention in recent years in many cancer vaccines, alone or in combination with immunotherapy, chemotherapy and radiotherapy (RT). TLRs have been shown to play controversial roles in cancer, depending on various factors that can mediate tumor progression or apoptosis. Several TLR agonists have reached clinical trials and are being evaluated in combination with standard of care therapies, including RT. Despite their prolific and central role in mediating immune responses, the role of TLRs in cancer, particularly in response to radiation, remains poorly understood. Radiation is recognized as either a direct stimulant of TLR pathways, or indirectly through the damage it causes to target cells that subsequently activate TLRs. These effects can mediate pro-tumoral and anti-tumoral effects depending on various factors such as radiation dose and fractionation, as well as host genomic features. In this review, we examine how TLR signaling affects tumor response to RT, and we provide a framework for the design of TLR-based therapies with RT.

Ionizing radiation and toll like receptors: A systematic review article

Ionizing radiation, including X and gamma rays, are used for various purposes such as; medicine, nuclear power, research, manufacturing, food preservation and construction. Furthermore, people are also exposed to ionizing radiation from their workplace or the environment. Apart from DNA fragmentation resulting in apoptosis, several additional mechanisms have been proposed to describe how radiation can alter human cell functions. Ionizing radiation may alter immune responses, which are the main cause of human disorders. Toll like receptors (TLRs) are important human innate immunity receptors which participate in several immune and non-immune cell functions including, induction of appropriate immune responses and immune related disorders. Based on the role played by ionizing radiation on human cell systems, it has been hypothesized that radiation may affect immune responses. Therefore, the main aim of this review article is to discuss recent information regarding the effects of ionizing radiation on TLRs and their related disorders.

The Phosphodiesterase-5 Inhibitors and Prostate Cancer – What We Rely Know About It?

Phosphodiesterase-5 inhibitors (PDE5Is) represent a group of drugs that are registered for the treatment of erectile dysfunctions predominantly, but recently also for treatment of pulmonary hypertension and benign prostatic hypertrophy. However, more and more research deals with possible antitumor potential of PDE5Is in different types of cancers, including prostate cancer. Prostate cancer represents the one of the most common carcinoma in the male population, whose incidence is continuously increasing. Early detection combined with radical prostatectomy increases the survival rate, but also it is necessary to keep in mind the quality of life of patients undergoing prostatectomy in light of bladder control and erectile function. Authors of various clinical studies presented the results that often lead to totally opposing conclusions. For example, Chavez and colleagues have shown that use of PDE5Is in men with erectile dysfunction decreases the risk of developing prostate cancer, while, on the other hand, Michl and colleagues pointed out the adversely effect of PDE5Is on biochemical recurrence after bilateral nerve sparing radical prostatectomy. In that sense, the aim of this review was to present as many as possible of existing results dealing with of action of PDE5Is in the field of prostatic carcinoma. Taking into account all presented data, it can be concluded that eff ect of PDE5Is on formation, development and outcome of treatment in patients with prostate carcinoma is very intriguing question, whose response requires additional both experimental and clinical research.

NOS2 deficiency has no influence on the radiosensitivity of the hematopoietic system

Objective

Previous studies have shown that inhibition of inducible NO synthase (NOS2 or iNOS) with an inhibitor can selectively protect several normal tissues against radiation during radiotherapy. However, the role of NOS2 in ionizing radiation (IR)-induced bone marrow (BM) suppression is unknown and thus was investigated in the present study using NOS2⁻/⁻ and wild-type mice 14 days after they were exposed to a sublethal dose of total body irradiation (TBI).

Methods

The effects of different doses of IR (1, 2 and 4 Gy) on the apoptosis and colony-forming ability of bone marrow cells from wild-type (WT) and NOS2⁻/⁻ mice were investigated in vitro. In addition, we exposed NOS2⁻/⁻ mice and WT mice to 6-Gy TBI or sham irradiation. They were euthanized 14 days after TBI for analysis of peripheral blood cell counts and bone marrow cellularity. Colony-forming unit-granulocyte and macrophage, burst-forming unit-erythroid and CFU-granulocyte, erythroid, macrophage in bone marrow cells from the mice were determined to evaluate the function of hematopoietic progenitor cells (HPCs), and the ability of hematopoietic stem cells (HSCs) to self-renew was analysed by the cobblestone area forming cell assay. The cell cycling of HPCs and HSCs were measured by flow cytometry.

Results

Exposure to 2 and 4 Gy IR induced bone marrow cell apoptosis and inhibited the proliferation of HPCs in vitro. However, there was no difference between the cells from WT mice and NOS2⁻/⁻ mice in response to IR exposure in vitro. Exposure of WT mice and NOS2⁻/⁻ mice to 6 Gy TBI decreased the white blood cell, red blood cell, and platelet counts in the peripheral blood and bone marrow mononuclear cells, and reduced the colony-forming ability of HPCs (P < 0.05), damaged the clonogenic function of HSCs. However, these changes were not significantly different in WT and NOS2⁻/⁻ mice.

Conclusion

These data suggest that IR induces BM suppression in a NOS2-independent manner.

Di-(2-ethylhexyl) phthalate enhances melanoma tumor growth via differential effect on M1-and M2-polarized macrophages in mouse model

Phthalates are widely used as plasticizers that influence sexual and reproductive development. Here, we investigated whether di-(2-ethylhexyl) phthalate (DEHP) affects macrophage polarization that are associated with tumor initiation and progression. No changes were observed in LPS- or ConA-stimulated in vitro spleen B or T cell proliferation for 48 h, respectively. In contrast, macrophage functions were inhibited in response to DEHP for 12 h as judged by LPS-induced H₂O₂ and NO production and zymosan A-mediated phagocytosis. When six weeks old male mice were pre-exposed to 4.0 mg/kg DEHP for 21 days before the injection of B16F10 melanoma cells and post-exposed to 4.0 mg/kg DEHP for 7 days, tumor nodule formation and the changes in tumor volume were higher than those in control group. Furthermore, when male mice were intraperitoneally pretreated with DEHP for 3 or 4 weeks and peritoneal exudate cells (PECs) or bone marrow-derived macrophages (BMDMs) were incubated with lipopolysaccharide (LPS), the expression of COX-2, TNF-α, and IL-6 was reduced in DEHP-pretreated cells as compared with that in LPS-stimulated control cells. While the production of nitric oxide (NO) for 18 h was reduced by LPS-stimulated PECs and M1-type BMDMs, IL-4 expression was enhanced in LPS-stimulated BMDMs. When BMDMs were incubated with IL-4 for 30 h, arginase 1 for M2-type macrophages was increased in transcriptional and translational level. Data implicate that macrophages were differentially polarized by DEHP treatment, which reduced M1-polarzation but enhanced M2-polarization. Taken together, these data demonstrate that DEHP could affect in vivo immune responses of macrophages, leading to the suppression of their tumor-preventing ability. This suggests that individuals at high risk for tumor incidence should avoid long-term exposure to various kind of phthalate including DEHP.

Macrophage biology plays a central role during ionizing radiation-elicited tumor response

Radiation therapy is one of the major therapeutic modalities for most solid tumors. The anti-tumor effect of radiation therapy consists of the direct tumor cell killing, as well as the modulation of tumor microenvironment and the activation of immune response against tumors. Radiation therapy has been shown to promote immunogenic cells death, activate dendritic cells and enhance tumor antigen presentation and anti-tumor T cell activation. Radiation therapy also programs innate immune cells such as macrophages that leads to either radiosensitization or radioresistance, according to different tumors and different radiation regimen studied. The mechanisms underlying radiation-induced macrophage activation remain largely elusive. Various molecular players such as NF-κB, MAPKs, p53, reactive oxygen species, inflammasomes have been involved in these processes. The skewing to a pro-inflammatory phenotype thus results in the activation of anti-tumor immune response and enhanced radiotherapy effect. Therefore, a comprehensive understanding of the mechanism of radiation-induced macrophage activation and its role in tumor response to radiation therapy is crucial for the development of new therapeutic strategies to enhance radiation therapy efficacy.

Reprogramming of Tumor-Associated Macrophages with Anticancer Therapies: Radiotherapy versus Chemo- and Immunotherapies

Tumor-associated macrophages (TAMs) play a central role in tumor progression, metastasis, and recurrence after treatment. Macrophage plasticity and diversity allow their classification along a M1–M2 polarization axis. Tumor-associated macrophages usually display a M2-like phenotype, associated with pro-tumoral features whereas M1 macrophages exert antitumor functions. Targeting the reprogramming of TAMs toward M1-like macrophages would thus be an efficient way to promote tumor regression. This can be achieved through therapies including chemotherapy, immunotherapy, and radiotherapy (RT). In this review, we first describe how chemo- and immunotherapies can target TAMs and, second, we detail how RT modifies macrophage phenotype and present the molecular pathways that may be involved. The identification of irradiation dose inducing macrophage reprogramming and of the underlying mechanisms could lead to the design of novel therapeutic strategies and improve synergy in combined treatments.

Nonylphenol increases tumor formation and growth by suppressing gender-independent lymphocyte proliferation and macrophage activation

Nonylphenol (NP) is a well-known endocrine disruptor that influences sexual and reproductive development. Here, we investigated whether NP affects immune responses that are associated with tumor initiation and progression. When spleen cells were incubated with lipopolysaccharide (LPS) and concanavalin A in the presence of 10^-4 M NP, the proliferation of B and T lymphocytes was reduced compared with that in controls, in a gender-independent fashion. While 10^-4 M NP also decreased the production of nitric oxide (NO) in LPS-stimulated bone marrow-derived macrophages (BMDMs), no changes in NO production were detected following treatment with 10^-5 M NP. LPS-stimulated expression of iNOS, COX2, IL-6 and TNF-α in BMDMs was reduced after 6 or 18 hours of incubation with 10^-5 M NP. Furthermore, when mice were pre-exposed to NP for 7 days prior to the injection of B16F10 melanoma cells, the rates of tumor nodule formation and relative tumor growth were higher than those in the control group. In vivo immunosuppressive effect was also clarified by the inhibition of proliferation in B/T lymphocyte and cytokine production in peritoneal macrophages from the mice pretreated with NP for 7 days. Taken together, these data demonstrate that NP could affect the immune responses of lymphocytes and macrophages, leading to the suppression of their tumor-preventing ability. This suggests that individuals at high risk for tumor development should avoid frequent exposure to NP and other endocrine disruptors.

Polarized macrophages treated with nonylphenol differently regulate lipopolysaccharide-induced sepsis

Nonylphenol (NP) as well-known "endocrine disrupter" influences sexual and reproductive development. Here, we investigated the effect of NP on M1-/M2-type macrophages and their role in lipopolysaccharide (LPS)-induced sepsis. Polarized macrophages of M1- and M2-types were obtained by the treatment with LPS and interleukin-4 (IL-4) to bone marrow-derived macrophages (BMDM), respectively. Coincubation of M1-macrophages with NP decreased COX-2, iNOS, IL-6, and TNF-α expression but no changes were detected in the production of nitric oxide (NO). Survival probability of LPS-induced sepsis mice was enhanced by the injection of NP-treated BMDM as compared to the injection of NP-untreated control BMDM. In the meanwhile, the expression of arginase 1(Arg1), a marker for M2-polarized macrophages was increased by the stimulation with LPS in BMDM. Arg1 expression was also enhanced by the treatment with IL-4 in BMDM, which was reduced by the coincubation with NP. Survival probability of LPS-induced sepsis mice was decreased by the injection of BMDM treated with IL-4 and NP as compared to the injection of IL-4-treated BMDM. It suggests that NP might inhibit macrophage function and the polarization to M2-macrophages. Taken together, data demonstrate that NP could differently affect immune responses of polarized macrophages resulted in the modulation of LPS-induced sepsis. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 2081-2089, 2016.

Metabolic Reprogramming of Immune Cells in Cancer Progression

Immune cells play a key role in host defense against infection and cancer. Upon encountering danger signals, these cells undergo activation leading to a modulation in their immune functions. However, recent studies reveal that immune cells upon activation also show distinct metabolic changes that impact their immune functions. Such metabolic reprogramming and its functional effects are well known for cancer cells. Given that immune cells have emerged as crucial players in cancer progression, it is important to understand whether immune cells also undergo metabolic reprogramming in tumors and how this might affect their contribution in cancer progression. This emerging aspect of tumor-associated immune cells is reviewed here, discussing metabolic reprogramming of different immune cell types, the key pathways involved, and its impact on tumor progression.