Roles of CXC chemokines and macrophages in the recruitment of inflammatory cells and tumor rejection induced by Fas/Apo-1 (CD95) ligand-expressing tumor

miR-196b-5p-mediated downregulation of FAS promotes NSCLC progression by activating IL6-STAT3 signaling

Our recent study demonstrated that the QKI-5 regulated miRNA, miR-196b-5p, and it functions as an onco-microRNA in non-small cell lung cancer (NSCLC) by directly targeting GATA6 and TSPAN12. However, the role of miR-196b-5p in NSCLC progression and metastasis still remains unclear. We found that miR-196b-5p promotes lung cancer cell proliferation and colony formation by directly targeting tumor suppressor, FAS. The expression of FAS was significantly downregulated in NSCLC tissue samples and was negatively correlated with the miR-196b-5p expression. Knocking down FAS activates NFkB signaling and subsequent IL6 secretion, resulting in phosphorylation of signal transducer and activator of transcription 3 (STAT3) to promote lung cancer cell growth. Our findings indicated that miR-196b-5p might exhibit novel oncogenic function by FAS-mediated STAT3 activation in NSCLC, and suggested that targeting the miR-196b-5p/FAS/NFkB/IL6/STAT3 pathway might be a promising therapeutic strategy in treating NSCLC.

Luminol-based bioluminescence imaging of mouse mammary tumors

Polymorphonuclear neutrophils (PMNs) are the most abundant circulating blood leukocytes. They are part of the innate immune system and provide a first line of defense by migrating toward areas of inflammation in response to chemical signals released from the site. Some solid tumors, such as breast cancer, also cause recruitment and activation of PMNs and release of myeloperoxidase. In this study, we demonstrate that administration of luminol to mice that have been transplanted with 4T1 mammary tumor cells permits the detection of myeloperoxidase activity, and consequently, the location of the tumor. Luminol allowed detection of activated PMNs only two days after cancer cell transplantation, even though tumors were not yet palpable. In conclusion, luminol-bioluminescence imaging (BLI) can provide a pathway towards detection of solid tumors at an early stage in preclinical tumor models.

Fas/CD95-induced chemokines can serve as "find-me" signals for apoptotic cells

Apoptosis is commonly thought to represent an immunologically silent or even anti-inflammatory mode of cell death, resulting in cell clearance in the absence of explicit activation of the immune system. However, here we show that Fas/CD95-induced apoptosis is associated with the production of an array of cytokines and chemokines, including IL-6, IL-8, CXCL1, MCP-1, and GMCSF. Fas-induced production of MCP-1 and IL-8 promoted chemotaxis of phagocytes toward apoptotic cells, suggesting that these factors serve as "find-me" signals in this context. We also show that RIPK1 and IAPs are required for optimal production of cytokines and chemokines in response to Fas receptor stimulation. Consequently, a synthetic IAP antagonist potently suppressed Fas-dependent expression of multiple proinflammatory mediators and inhibited Fas-induced chemotaxis. Thus, in addition to provoking apoptosis, Fas receptor stimulation can trigger the secretion of chemotactic factors and other immunologically active proteins that can influence immune responsiveness toward dying cells.

Potential for modulation of the fas apoptotic pathway by epidermal growth factor in sarcomas

One important mechanism by which cancer cells parasitize their host is by escaping apoptosis. Thus, selectively facilitating apoptosis is a therapeutic mechanism by which oncotherapy may prove highly advantageous. One major apoptotic pathway is mediated by Fas ligand (FasL). The death-inducing signaling Ccmplex (DISC) and subsequent death-domain aggregations are created when FasL is bound by its receptor thereby enabling programmed cell death. Conceptually, if a better understanding of the Fas pathway can be garnered, an oncoselective prodeath therapeutic approach can be tailored. Herein, we propose that EGF and CTGF play essential roles in the regulation of the Fas apoptotic pathway in sarcomas. Tumor and in vitro data suggest viable cells counter the prodeath signal induced by FasL by activating EGF, which in turn induces prosurvival CTGF. The prosurvival attributes of CTGF ultimately predominate over the death-inducing FasL. Cells destined for elimination inhibit this prosurvival response via a presently undefined pathway. This scenario represents a novel role for EGF and CTGF as regulators of the Fas pathway in sarcomas.

Polymorphonuclear neutrophils and cancer: intense and sustained neutrophilia as a treatment against solid tumors

Polymorphonuclear neutrophils (PMN) are the most abundant circulating immune cells and represent the first line of immune defense against infection. This review of the biomedical literature of the last 40 years shows that they also have a powerful antitumoral effect under certain circumstances. Typically, the microenvironment surrounding a solid tumor possesses many of the characteristics of chronic inflammation, a condition considered very favorable for tumor growth and spread. However, there are many circumstances that shift the chronic inflammatory state toward an acute inflammatory response around a tumor. This shift seems to convert PMN into very efficient anticancer effector cells. Clinical reports of unexpected antitumoral effects linked to the prolonged use of granulocyte colony-stimulating factor, which stimulates an intense and sustained neutrophilia, suggest that an easy way to fight solid tumors would be to encourage the development of intense peritumoral PMN infiltrates. Specifically designed clinical trials are urgently needed to evaluate the safety and efficacy of such drug-induced neutrophilia in patients with solid tumors. This antitumoral role of neutrophils may provide new avenues for the clinical treatment of cancer.

CD95-ligand on peripheral myeloid cells activates Syk kinase to trigger their recruitment to the inflammatory site

Injury to the central nervous system initiates an uncontrolled inflammatory response that results in both tissue repair and destruction. Here, we showed that, in rodents and humans, injury to the spinal cord triggered surface expression of CD95 ligand (CD95L, FasL) on peripheral blood myeloid cells. CD95L stimulation of CD95 on these cells activated phosphoinositide 3-kinase (PI3K) and metalloproteinase-9 (MMP-9) via recruitment and activation of Syk kinase, ultimately leading to increased migration. Exclusive CD95L deletion in myeloid cells greatly decreased the number of neutrophils and macrophages infiltrating the injured spinal cord or the inflamed peritoneum after thioglycollate injection. Importantly, deletion of myeloid CD95L, but not of CD95 on neural cells, led to functional recovery of spinal injured animals. Our results indicate that CD95L acts on peripheral myeloid cells to induce tissue damage. Thus, neutralization of CD95L should be considered as a means to create a controlled beneficial inflammatory response.

Photodynamic therapy enhancement of antitumor immunity is regulated by neutrophils

Photodynamic therapy (PDT) is a Food and Drug Administration-approved local cancer treatment that can be curative of early disease and palliative in advanced disease. PDT of murine tumors results in regimen-dependent induction of an acute local inflammatory reaction, characterized in part by rapid neutrophil infiltration into the treated tumor bed. In this study, we show that a PDT regimen that induced a high level of neutrophilic infiltrate generated tumor-specific primary and memory CD8(+) T-cell responses. In contrast, immune cells isolated from mice treated with a PDT regimen that induced little or no neutrophilic infiltrate exhibited minimal antitumor immunity. Mice defective in neutrophil homing to peripheral tissues (CXCR2(-/-) mice) or mice depleted of neutrophils were unable to mount strong antitumor CD8(+) T-cell responses following PDT. Neutrophils seemed to be directly affecting T-cell proliferation and/or survival rather than dendritic cell maturation or T-cell migration. These novel findings indicate that by augmenting T-cell proliferation and/or survival, tumor-infiltrating neutrophils play an essential role in establishment of antitumor immunity following PDT. Furthermore, our results may suggest a mechanism by which neutrophils might affect antitumor immunity following other inflammation-inducing cancer therapies. Our findings lay the foundation for the rational design of PDT regimens that lead to optimal enhancement of antitumor immunity in a clinical setting. Immune-enhancing PDT regimens may then be combined with treatments that result in optimal ablation of primary tumors, thus inhibiting growth of primary tumor and controlling disseminated disease.

SPARC Endogenous Level, rather than Fibroblast-Produced SPARC or Stroma Reorganization Induced by SPARC, Is Responsible for Melanoma Cell Growth

SPARC (secreted protein acidic and rich in cysteine) is a matricellular protein whose overexpression in malignant or tumor-stromal cells is often associated with increased aggressiveness and bad prognosis in a wide range of human cancer types, particularly melanoma. We established the impact that changes in the level of SPARC produced by malignant cells and neighboring stromal cells have on melanoma growth. Melanoma cell growth in monolayer was only slightly affected by changes in SPARC levels. However, melanoma growth in spheroids was strongly inhibited upon SPARC hyperexpression and conversely enhanced when SPARC expression was downregulated. Interestingly, SPARC overexpression in neighboring fibroblasts had no effect on spheroid growth irrespective of SPARC levels expressed by the melanoma cells, themselves. Downregulation of SPARC expression in melanoma cells induced their rejection in vivo through a mechanism mediated exclusively by host polymorphonuclear cells. On the other hand, SPARC hyperexpression enhanced vascular density, collagen deposition, and fibroblast recruitment in the surrounding stroma without affecting melanoma growth. In agreement with the in vitro data, overexpression of SPARC in co-injected fibroblasts did not affect melanoma growth in vivo. All the data indicate that melanoma growth is not subject to regulation by exogenous SPARC, nor by stromal organization, but only by SPARC levels produced by the malignant cells themselves.

Fas (CD95) induces macrophage proinflammatory chemokine production via a MyD88-dependent, caspase-independent pathway

Activation of the prototypical death receptor, Fas (CD95), can induce both caspase-dependent cell death and production of proinflammatory chemokines, leading to neutrophil recruitment and end-organ injury. The precise mechanism(s) by which Fas up-regulates chemokine production and release, is currently unclear. We hypothesized that Fas-induced chemokine release by macrophages is dependent on the MyD88 adaptor molecule and independent of caspase activity. To test this hypothesis, we measured chemokine response to Fas activation both in RAW 264.7 cells with RNAi-attenuated MyD88 expression and in MyD88-deficient primary macrophages. We found that Fas-induced chemokine release was abrogated in the absence of MyD88. In vivo, MyD88(-/-) mice had impaired CXCL1/KC release and polymorphonuclear cell recruitment in response to intratracheal treatment with the Fas-activating monoclonal antibody, Jo-2. Furthermore, Fas-induced chemokine release was not dependent on either IL-1 receptor signaling or on caspase activity. We conclude that MyD88 plays an integral role in Fas-induced macrophage-mediated inflammation.

Regulatory T cells inhibit Fas ligand-induced innate and adaptive tumour immunity

CD4+CD25+ regulatory T cells (Treg) are known to influence T cell responses to tumours. Here we have explored the role of Treg in inhibiting not only adaptive, but also innate immune responses to tumours. To this end we used a Fas ligand (FasL)-expressing melanoma cell line in a mouse model. In this system, innate immunity is sufficient to reject the tumour. All mice depleted of Treg and challenged with FasL-expressing melanoma remained tumour-free. Investigation of the underlying cellular effector mechanisms revealed that depletion of Treg enhanced an NK cell response capable of tumour lysis. Furthermore, this initial innate immune response primed mice to make an effective adaptive immune response leading to complete rejection of challenge with the parental melanoma. Both antigen-specific antibody and CD4+ T cells were implicated in protection via adaptive immunity. We conclude that removal of Treg and vaccination with whole tumour cells expressing FasL activates multiple arms of the immune system, leading to efficient tumour rejection. These findings highlight a novel role for FasL in inducing innate immune responses that are normally inhibited by Treg and uncover an adjuvant effect of FasL that can be used to stimulate tumour immunity after depletion of Treg.