On the dual roles and polarized phenotypes of neutrophils in tumor development and progression. Crit Rev Oncol Hematol. 2012;82:296-309. [PMID: 21798756 DOI: 10.1016/j.critrevonc.2011.06.004]

Neutrophils in the Tumor Microenvironment

Neutrophils are the first responders to sites of acute tissue damage and infection. Recent studies suggest that in addition to neutrophil apoptosis, resolution of neutrophil inflammation at wounds can be mediated by reverse migration from tissues and transmigration back into the vasculature. In settings of chronic inflammation, neutrophils persist in tissues, and this persistence has been associated with cancer progression. However, the role of neutrophils in the tumor microenvironment remains controversial, with evidence for both pro- and anti-tumor roles. Here we review the mechanisms that regulate neutrophil recruitment and resolution at sites of tissue damage, with a specific focus on the tumor microenvironment. We discuss the current understanding as to how neutrophils alter the tumor microenvironment to support or hinder cancer progression, and in this context outline gaps in understanding and important areas of inquiry.

Intratumoral polymorphonuclear granulocyte is associated with poor prognosis in squamous esophageal cancer by promoting epithelial-mesenchymal transition

AIM

The role of polymorphonuclear granulocyte (PMN) infiltration in tumor remains unclear in esophageal cancer (EC).

MATERIALS & METHODS

We conducted a retrospective study on consecutive patients with primary squamous EC. The potential roles of PMN infiltration into tumor nests were assessed by immunohistochemistry. The interactions of PMNs and tumor cells were investigated in an in vitro coculture system.

RESULTS

Intratumoral PMN is an independent prognostic factor. PMN infiltration induces epithelial-mesenchymal transition of cancer cells with the initiation of TGF-β/Smad signaling pathway.

CONCLUSION

Our study demonstrates intratumoral PMN is an independent unfavorable predictor in squamous EC. PMN promotes cancer progression partly by its ability to induce epithelial-mesenchymal transition via TGF-β/Smad signaling pathway.

Peritumoural neutrophils negatively regulate adaptive immunity via the PD-L1/PD-1 signalling pathway in hepatocellular carcinoma

BACKGROUND

PD-L1 expression on neutrophils contributes to the impaired immune response in infectious disease, but the detailed role of PD-L1 expression on neutrophils in HCC remains unclear.

METHODS

We investigated the phenotype and morphology of neutrophils infiltrated in tumour tissues from both patients with HCC and hepatoma-bearing mice.

RESULTS

We found that neutrophils dominantly infiltrated in the peritumoural region. The neutrophil-to-T cell ratio (NLR) was higher in peritumoural tissue than that in the intratumoural tissue and was negatively correlated with the overall survival of patients with HCC. Infiltrating neutrophils displayed a phenotype of higher frequency of programmed cell death ligand 1 (PD-L1) positive neutrophils. The ratio of PD-L1(+) neutrophils-to-PD-1(+) T cells was higher in peritumoural tissue and better predicted the disease-free survival of patients with HCC. We further confirmed a higher frequency of PD-L1(+) neutrophils and PD-1(+) T cells in hepatoma-bearing mice. Functionally, the PD-L1(+) neutrophils from patients with HCC effectively suppressed the proliferation and activation of T cells, which could be partially reversed by the blockade of PD-L1.

CONCLUSIONS

Our results indicate that the tumour microenvironment induces impaired antitumour immunity via the modulation of PD-L1 expression on tumour infiltrating neutrophils.

Nuclear-enriched abundant transcript 1 as a diagnostic and prognostic biomarker in colorectal cancer

BACKGROUND

High expression of the long non-coding RNA nuclear-enriched abundant transcript 1 (NEAT1) in whole blood has been reported in colorectal cancer patients; however, its' clinical significance and origin are unclear. We evaluated the diagnostic and prognostic value, and origin of whole blood NEAT1 in colorectal cancer.

METHODS

Expression of NEAT1 variants, NEAT1_v1 and NEAT1_v2 were determined using real-time quantitative PCR. The diagnostic value of whole blood NEAT1 expression was evaluated in test (n = 60) and validation (n = 200) cohorts of colorectal cancer patients and normal controls (NCs). To identify the origin of NEAT1, its expression was analyzed in blood, matched primary tumor tissues, para-tumor tissues, metastatic tissues, and also immune cells from patients or NCs. Function of NEAT1 in colorectal cell lines was also assessed. The correlation of NEAT1 expression with clinical outcomes was assessed in 191 patients.

RESULTS

Whole blood NEAT1 expression was significantly higher in colorectal cancer patients than in NCs. NEAT1_v1 and NEAT1_v2 expression were highly accurate in distinguishing colorectal cancer patients from NCs (area under the curve: 0.787 and 0.871, respectively). Knockdown of NEAT1_v1 in vitro could inhibit cell invasion and proliferation, while knockdown of NEAT1_v2 promoted cell growth. However, whole blood expression was not correlated with matched tissues. An elevated expression was seen in neutrophils from CRC patients. Furthermore, high expression of NEAT1_v1 was correlated with worse overall survival. In contrast, high expression of NEAT1_v2 alone was correlated with better overall survival.

CONCLUSION

Whole blood NEAT1 expression is a novel diagnostic and prognostic biomarker of overall survival in colorectal cancer. Elevated NEAT1 may derive from neutrophils.

Differential infiltration of neutrophils in T1-T2 versus T3-T4 oral squamous cell carcinomas: a preliminary study

Background

Recent studies have pointed towards a role of tumour-infiltrating neutrophils in cancer biology. Investigations on oral squamous cell carcinoma have indicated a possible association with clinical characteristics. This study aimed to evaluate neutrophil infiltration and the neutrophil/lymphocyte ratio in the central areas and invasive front of oral squamous cell carcinomas at different T stages, and their association with clinicopathological features and patient outcome.

Methods

Clinical information was retrieved from the charts of patients who had undergone surgical treatment. Samples of the excised tumours were subjected to immunohistochemical analysis for CD66b and CD3. Semi-quantitative analysis was performed in the intratumoural region and in the invasive front. Appropriate statistical tests were used for evaluating the data, including Kaplan–Meier survival analysis and the log-rank test. A p value of less than 0.05 was considered significant.

Results

T3–T4 tumours presented higher CD66b infiltration in the intratumoural region and higher CD66b/CD3 ratios in the invasive front than T1–T2 lesions (p < 0.05). There was a strong inverse correlation between CD66b and CD3 in the invasive front of T3–T4 tumours (r = −0.712, p < 0.05). Comparisons of CD66b and the CD66b/CD3 ratio according to N status, tumour location, recurrence, inflammation grade, and histological grade did not reach statistical significance. Survival analysis also did not show any significant differences.

Conclusions

The present study showed different degrees of neutrophil infiltration between T1–T2 and T3–T4 oral cancers, with higher indexes in the advanced lesions. However, there was no association with clinicopathological features or with time to recurrence.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-015-1541-x) contains supplementary material, which is available to authorized users.

Prognostic and predictive significance of immune cells infiltrating cutaneous melanoma

The tumor microenvironment is shaped by interactions between malignant cells and host cells representing an integral component of solid tumors. Host cells, including elements of the innate and adaptive immune system, can exert both positive and negative effects on the outcome of the disease. In melanoma, studies on the prognostic impact of the lymphoid infiltrate in general, and that of T cells, yielded controversial results. According to our studies and data in the literature, a high peritumoral density of activated T cells, increased amount of B lymphocytes and mature dendritic cells (DCs) predicted longer survival, while intense infiltration by plasmacytoid DCs or neutrophil granulocytes could be associated with poor prognosis. Besides its prognostic value, evaluation of the components of immune infiltrate could provide biomarkers for predicting the efficacy of the treatment and disease outcome in patients treated with immunotherapy or other, non-immune-based modalities as chemo-, radio-, or targeted therapy.

Angiostatic, tumor inflammatory and anti-tumor effects of CXCL4(47-70) and CXCL4L1(47-70) in an EGF-dependent breast cancer model

CXCL4 and CXCL4L1, platelet-derived CXC chemokines, and their carboxy-terminal peptides CXCL4^47–70 and CXCL4L1^47–70 previously displayed angiostatic and anti-tumoral activity in a melanoma model. Here, we found CXCL4^47–70 and CXCL4L1^47–70 to inhibit lymphatic endothelial cell proliferation in vitro. Furthermore, the angiostatic potential of CXCL4^47–70 and CXCL4L1^47–70 was tested against different angiogenic stimuli (FGF1, FGF2, FGF8, EGF and VEGF). Besides reducing FGF2-induced vascular endothelial cell growth, CXCL4^47–70 and CXCL4L1^47–70 efficiently counteracted EGF. Consequently, we considered their anti-tumoral potential in EGF-dependent MDA-MB-231 breast tumors. In tumor-bearing mice, CXCL4^47–70 reduced tumor growth better than CXCL4L1^47–70. In CXCL4^47–70-treated tumors significantly more intratumoral monocytes/macrophages and dendritic cells were present and higher expression levels of CCL5 and IFN-γ were detected by qPCR on tumor lysates. Because neither peptide was able to specifically bind CXCR3A or CXCR3B, differential glycosaminoglycan binding and direct interaction with cytokines (EGF and CCL5) might explain any differences in anti-tumoral effects. Notably, CCL5-induced monocyte chemotaxis in vitro was increased by addition of CXCL4^47–70 or CXCL4L1^47–70. Finally, CXCL4^47–70 and CXCL4L1^47–70 inhibited proliferation of MDA-MB-231 cells. Our results suggest a tumor type-dependent responsiveness to either CXCL4^47–70 or CXCL4L1^47–70 treatment, defined by anti-proliferative, angiostatic and inflammatory actions, and substantiate their therapeutic potential.

Identification and characterization of VEGF-A-responsive neutrophils expressing CD49d, VEGFR1, and CXCR4 in mice and humans

Vascular endothelial growth factor A (VEGF-A) is upregulated during hypoxia and is the major regulator of angiogenesis. VEGF-A expression has also been found to recruit myeloid cells to ischemic tissues where they contribute to angiogenesis. This study investigates the mechanisms underlying neutrophil recruitment to VEGF-A as well as the characteristics of these neutrophils. A previously undefined circulating subset of neutrophils shown to be CD49d(+)VEGFR1(high)CXCR4(high) was identified in mice and humans. By using chimeric mice with impaired VEGF receptor 1 (VEGFR1) or VEGFR2 signaling (Flt-1tk(-/-), tsad(-/-)), we found that parallel activation of VEGFR1 on neutrophils and VEGFR2 on endothelial cells was required for VEGF-A-induced recruitment of circulating neutrophils to tissue. Intravital microscopy of mouse microcirculation revealed that neutrophil recruitment by VEGF-A versus by the chemokine macrophage inflammatory protein 2 (MIP-2 [CXCL2]) involved the same steps of the recruitment cascade but that an additional neutrophil integrin (eg, VLA-4 [CD49d/CD29]) played a crucial role in neutrophil crawling and emigration to VEGF-A. Isolated CD49d(+) neutrophils featured increased chemokinesis but not chemotaxis compared with CD49d(-) neutrophils in the presence of VEGF-A. Finally, by targeting the integrin α4 subunit (CD49d) in a transplantation-based angiogenesis model that used avascular pancreatic islets transplanted to striated muscle, we demonstrated that inhibiting the recruitment of circulating proangiogenic neutrophils to hypoxic tissue impairs vessel neoformation. Thus, angiogenesis can be modulated by targeting cell-surface receptors specifically involved in VEGF-A-dependent recruitment of proangiogenic neutrophils without compromising recruitment of the neutrophil population involved in the immune response to pathogens.

Angiotensin converting enzyme inhibitors and angiotensin II receptor antagonist attenuate tumor growth via polarization of neutrophils toward an antitumor phenotype

Tumor microenvironments polarize neutrophils to protumoral phenotypes. Here, we demonstrate that the angiotensin converting enzyme inhibitors (ACEis) and angiotensin II type 1 receptor (AGTR1) antagonist attenuate tumor growth via polarization of neutrophils toward an antitumoral phenotype. The ACEis or AGTR1 antagonist enhanced hypersegmentation of human neutrophils and increased neutrophil cytotoxicity against tumor cells. This neutrophil hypersegmentation was dependent on the mTOR pathway. In a murine tumor model, ACEis and AGTR1 antagonist attenuated tumor growth and enhanced neutrophil hypersegmentation. ACEis inhibited tumor-induced polarization of neutrophils to a protumoral phenotype. Neutrophil depletion reduced the antitumor effect of ACEi. Together, these data suggest that the modulation of Ang II pathway attenuates tumor growth via polarization of neutrophils to an antitumoral phenotype.

Stimulation of hepatocarcinogenesis by neutrophils upon induction of oncogenic kras expression in transgenic zebrafish

BACKGROUND & AIMS

Chronic inflammation is a major etiological factor for hepatocellular carcinoma (HCC), but how immune cells respond in the initiation of hepatocarcinogenesis remains uncharacterized. This study aims to investigate the response and roles of neutrophils in early hepatocarcinogenesis.

METHODS

By inducible expression of oncogenic kras(V12) in hepatocytes in transgenic zebrafish combined with live imaging of neutrophils in transparent larvae, the response of neutrophils to oncogenic liver was characterized and their roles investigated by pharmaceutical and genetic manipulations.

RESULTS

We found a rapid recruitment of neutrophils to the liver upon induction of kras(V12) expression. Pharmaceutical stimulation of neutrophils resulted in further increases of neutrophils in oncogenic livers, liver size and tumor severity, while inhibition of neutrophils caused decreases of liver-associated neutrophils and liver size. Time-lapse video indicated that neutrophils had a stagnant migratory pattern meandering along the tumor edge but became relatively stationary upon entering the kras(V12)-expressing liver. Both oncogenic hepatocytes and tumor-associated neutrophils (TANs) were isolated via fluorescence-activated cell sorting. Molecular analyses indicated a pro-inflammatory microenvironment, as marked by increased tgfβ1a expression in kras(V12)-expressing hepatocytes and a loss of anti-tumor activities in TANs. Depletion of Tgf-β significantly reduced the number of TANs and the size of oncogenic liver.

CONCLUSIONS

An inflammatory cue from oncogenic hepatocytes upon induction of kras(V12) expression causes a rapid recruitment of neutrophils to oncogenic liver and the neutrophils play a promoting role in early hepatocarcinogenesis.

CD11b+Ly6G+ cells inhibit tumor growth by suppressing IL-17 production at early stages of tumorigenesis

Neutrophils are important innate immune cells involved in microbial clearance at the sites of infection. However, their role in cancer development is unclear. We hypothesized that neutrophils mediate antitumor effects in early tumorigenesis. To test this, we first studied the cytotoxic effects of neutrophils in vitro. Neutrophils were cytotoxic against tumor cells, with neutrophils isolated from tumor-bearing mice trending to have increased cytotoxic activities. We then injected an ELR+ CXC chemokine-producing tumor cell line into C57BL/6 and Cxcr2−/− mice, the latter lacking the receptors for neutrophil chemokines. We observed increased tumor growth in Cxcr2−/− mice. As expected, tumors from Cxcr2−/− mice contained fewer neutrophils. Surprisingly, these tumors also contained fewer CD8⁺ T cells, but more IL-17-producing cells. Replenishment of functional neutrophils was correlated with decreased IL-17-producing cells, increased CD8⁺ T cells, and decreased tumor size in Cxcr2−/− mice, while depletion of neutrophils in C57BL/6 mice showed the opposite effects. Results from a non-ELR+ CXC chemokine producing tumor further supported that functional neutrophils indirectly mediate tumor control by suppressing IL-17A production. We further studied the correlation of IL-17A and CD8⁺ T cells in vitro. IL-17A suppressed proliferation and IFNγ production of CD8⁺ T cells, while CD11b+Ly6G+ neutrophils did not suppress CD8⁺ T cell function. Taken together, these data demonstrate that, while neutrophils could control tumor growth by direct cytotoxic effects, the primary mechanism by which neutrophils exert antitumor effects is to regulate IL-17 production, through which they indirectly promote CD8⁺ T cell responses.

Plasticity of neutrophils reveals modulatory capacity

Neutrophils are widely known as proinflammatory cells associated with tissue damage and for their early arrival at sites of infection, where they exert their phagocytic activity, release their granule contents, and subsequently die. However, this view has been challenged by emerging evidence that neutrophils have other activities and are not so short-lived. Following activation, neutrophil effector functions include production and release of granule contents, reactive oxygen species (ROS), and neutrophil extracellular traps (NETs). Neutrophils have also been shown to produce a wide range of cytokines that have pro- or anti-inflammatory activity, adding a modulatory role for this cell, previously known as a suicide effector. The presence of cytokines almost always implies intercellular modulation, potentially unmasking interactions of neutrophils with other immune cells. In fact, neutrophils have been found to help B cells and to modulate dendritic cell (DC), macrophage, and T-cell activities. In this review, we describe some ways in which neutrophils influence the inflammatory environment in infection, cancer, and autoimmunity, regulating both innate and adaptive immune responses. These cells can switch phenotypes and exert functions beyond cytotoxicity against invading pathogens, extending the view of neutrophils beyond suicide effectors to include functions as regulatory and suppressor cells.

Ovarian cancer microenvironment: implications for cancer dissemination and chemoresistance acquisition

Ovarian adenocarcinoma is characterized by a late detection, dissemination of cancer cells into the whole peritoneum, and the frequent acquisition of chemoresistance. If these particularities can be explained in part by intrinsic properties of ovarian cancer cells, an increased number of studies show the importance of the tumor microenvironment in tumor progression. Ovarian cancer cells can regulate the composition of their stroma in promoting the formation of ascitic fluid, rich in cytokines and bioactive lipids, and in stimulating the differentiation of stromal cells into a pro-tumoral phenotype. In return, cancer-associated fibroblasts, cancer-associated mesenchymal stem cells, tumor-associated macrophages, or other peritoneal cells, such as adipocytes and mesothelial cells can regulate tumor growth, angiogenesis, dissemination, and chemoresistance. This review focuses on the current knowledge about the roles of stromal cells and the associated secreted factors on tumor progression. We also summarize the different studies showing that targeting the microenvironment represents a great potential for improving the prognosis of patients with ovarian adenocarcinoma.

Tumor angiogenesis: MMP-mediated induction of intravasation- and metastasis-sustaining neovasculature

Metastasis is a distinct stage of cancer progression that requires the development of angiogenic blood vessels serving as conduits for tumor cell dissemination. An accumulated body of evidence indicates that metastasis-supporting neovasculature should possess certain structural characteristics allowing for the process of tumor cell intravasation, an active entry of cancer cells into the vessel interior. It appears that the development of tumor vessels with lumens of a distinctive size and support of these vessels by a discontinuous pericyte coverage constitute critical microarchitectural requirements to: (a) provide accessible points for vessel wall penetration by primary tumor cells; (b) provide enough lumen space for a tumor cell or cell aggregate upon intravasation; and (c) allow for sufficient rate of blood flow to carry away intravasated cells from the primary tumor to the next, proximal or distal site. This review will primarily focus on the functional roles of matrix metalloproteinases (MMPs), which catalytically trigger the development of an intravasation-sustaining neovasculature at the early stages of tumor growth and are also required for the maintenance of a metastasis-supporting state of blood vessels at later stages of cancer progression.

Granulocytic immune infiltrates are essential for the efficient formation of breast cancer liver metastases

Introduction

Breast cancer cells display preferences for specific metastatic sites including the bone, lung and liver. Metastasis is a complex process that relies, in part, on interactions between disseminated cancer cells and resident/infiltrating stromal cells that constitute the metastatic microenvironment. Distinct immune infiltrates can either impair the metastatic process or conversely, assist in the seeding, colonization and growth of disseminated cancer cells.

Methods

Using in vivo selection approaches, we previously isolated 4T1-derived breast cancer cells that preferentially metastasize to these organs and tissues. In this study, we examined whether the propensity of breast cancer cells to metastasize to the lung, liver or bone is associated with and dependent on distinct patterns of immune cell infiltration. Immunohistocytochemistry and immunohistofluorescence approaches were used to quantify innate immune cell infiltrates within distinct metastases and depletion of Gr1⁺ (Ly-6C and Ly-6G) or specifically Ly-6G⁺ cells was performed to functionally interrogate the role of Ly-6G⁺ infiltrates in promoting metastasis to these organs.

Results

We show that T lymphocytes (CD3⁺), myeloid-derived (Gr-1⁺) cells and neutrophils (Ly-6G⁺ or NE⁺) exhibit the most pronounced recruitment in lung and liver metastases, with markedly less recruitment within bone metastatic lesions. Interestingly, these infiltrating cell populations display different patterns of localization within soft tissue metastases. T lymphocytes and granulocytic immune infiltrates are localized around the periphery of liver metastases whereas they were dispersed throughout the lung metastases. Furthermore, Gr-1⁺ cell-depletion studies demonstrate that infiltrating myeloid-derived cells are essential for the formation of breast cancer liver metastases but dispensable for metastasis to the lung and bone. A specific role for the granulocytic component of the innate immune infiltrate was revealed through Ly-6G⁺ cell-depletion experiments, which resulted in significantly impaired formation of liver metastases. Finally, we demonstrate that the CD11b⁺/Ly-6G⁺ neutrophils that infiltrate and surround the liver metastases are polarized toward an N2 phenotype, which have previously been shown to enhance tumor growth and metastasis.

Conclusions

Our results demonstrate that the liver-metastatic potential of breast cancer cells is heavily reliant on interactions with infiltrating Ly-6G⁺ cells within the liver microenvironment.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-015-0558-3) contains supplementary material, which is available to authorized users.

Circular trimers of gelatinase B/matrix metalloproteinase-9 constitute a distinct population of functional enzyme molecules differentially regulated by tissue inhibitor of metalloproteinases-1

Gelatinase B/matrix metalloproteinase-9 (MMP-9) (EC 3.4.24.35) cleaves many substrates and is produced by most cell types as a zymogen, proMMP-9, in complex with the tissue inhibitor of metalloproteinases-1 (TIMP-1). Natural proMMP-9 occurs as monomers, homomultimers and heterocomplexes, but our knowledge about the overall structure of proMMP-9 monomers and multimers is limited. We investigated biochemical, biophysical and functional characteristics of zymogen and activated forms of MMP-9 monomers and multimers. In contrast with a conventional notion of a dimeric nature of MMP-9 homomultimers, we demonstrate that these are reduction-sensitive trimers. Based on the information from electrophoresis, AFM and TEM, we generated a 3D structure model of the proMMP-9 trimer. Remarkably, the proMMP-9 trimers possessed a 50-fold higher affinity for TIMP-1 than the monomers. In vivo, this finding was reflected in a higher extent of TIMP-1 inhibition of angiogenesis induced by trimers compared with monomers. Our results show that proMMP-9 trimers constitute a novel structural and functional entity that is differentially regulated by TIMP-1.

Phenotypic diversity and plasticity in circulating neutrophil subpopulations in cancer

Controversy surrounds neutrophil function in cancer because neutrophils were shown to provide both pro- and antitumor functions. We identified a heterogeneous subset of low-density neutrophils (LDNs) that appear transiently in self-resolving inflammation but accumulate continuously with cancer progression. LDNs display impaired neutrophil function and immunosuppressive properties, characteristics that are in stark contrast to those of mature, high-density neutrophils (HDNs). LDNs consist of both immature myeloid-derived suppressor cells (MDSCs) and mature cells that are derived from HDNs in a TGF-β-dependent mechanism. Our findings identify three distinct populations of circulating neutrophils and challenge the concept that mature neutrophils have limited plasticity. Furthermore, our findings provide a mechanistic explanation to mitigate the controversy surrounding neutrophil function in cancer.

Neutrophil elastase mediates acute pathogenesis and is a determinant of long-term behavioral recovery after traumatic injury to the immature brain

While neutrophil elastase (NE), released by activated neutrophils, is a key mediator of secondary pathogenesis in adult models of brain ischemia and spinal cord injury, no studies to date have examined this protease in the context of the injured immature brain, where there is notable vulnerability resulting from inadequate antioxidant reserves and prolonged exposure to infiltrating neutrophils. We thus reasoned that NE may be a key determinant of secondary pathogenesis, and as such, adversely influence long-term neurological recovery. To address this hypothesis, wild-type (WT) and NE knockout (KO) mice were subjected to a controlled cortical impact at post-natal day 21, approximating a toddler-aged child. To determine if NE is required for neutrophil infiltration into the injured brain, and whether this protease contributes to vasogenic edema, we quantified neutrophil numbers and measured water content in the brains of each of these genotypes. While leukocyte trafficking was indistinguishable between genotypes, vasogenic edema was markedly attenuated in the NE KO. To determine if early pathogenesis is dependent on NE, indices of cell death (TUNEL and activated caspase-3) were quantified across genotypes. NE KO mice showed a reduction in these markers of cell death in the injured hippocampus, which corresponded to greater preservation of neuronal integrity as well as reduced expression of heme oxygenase-1, a marker of oxidative stress. WT mice, treated with a competitive inhibitor of NE at 2, 6 and 12h post-injury, likewise showed a reduction in cell death and oxidative stress compared to vehicle-treated controls. We next examined the long-term behavioral and structural consequences of NE deficiency. NE KO mice showed an improvement in long-term spatial memory retention and amelioration of injury-induced hyperactivity. However, volumetric and stereological analyses found comparable tissue loss in the injured cortex and hippocampus independent of genotype. Further, WT mice treated acutely with the NE inhibitor showed no long-term behavioral or structural improvements. Together, these findings validate the central role of NE in both acute pathogenesis and chronic functional recovery, and support future exploration of the therapeutic window, taking into account the prolonged period of neutrophil trafficking into the injured immature brain.

Tumor-infiltrating neutrophils predict poor outcome in adenocarcinoma of the esophagogastric junction

Tumor-infiltrating neutrophil (TIN) has been reported to be an independent predictor in multiple tumors, but its role in the development of adenocarcinoma of the esophagogastric junction (AEG) remains unclear. We conducted immunohistochemistry (IHC) to detect the expression of TIN in 113 consecutive patients with primary AEG. The prognostic value and its relationship with clinicopathological characteristics and Ki-67 (a proliferation-associated antigen) expression were analyzed. High level of TIN was related to poor outcome in AEG patients with a hazard ratio (HR) of 3.93 (95% confidence interval (CI) = 2.14-7.19, p < 0.001) in univariate analysis and a HR of 3.44 (95% CI = 1.85-6.37, p < 0.001) in multivariate analysis. In addition, TIN was positively correlated with Ki-67 expression (p = 0.008). Our study found that TIN expression was an independent unfavorable predictor in AEG. Furthermore, the relationship between TIN and Ki-67 indicated that TIN was associated with tumor proliferation, which might provide a potential mechanism for why TIN was related to poor outcome in AEG.

Tumor-associated neutrophils stimulate T cell responses in early-stage human lung cancer

Infiltrating inflammatory cells are highly prevalent within the tumor microenvironment and mediate many processes associated with tumor progression; however, the contribution of specific populations remains unclear. For example, the nature and function of tumor-associated neutrophils (TANs) in the cancer microenvironment is largely unknown. The goal of this study was to provide a phenotypic and functional characterization of TANs in surgically resected lung cancer patients. We found that TANs constituted 5%-25% of cells isolated from the digested human lung tumors. Compared with blood neutrophils, TANs displayed an activated phenotype (CD62L(lo)CD54(hi)) with a distinct repertoire of chemokine receptors that included CCR5, CCR7, CXCR3, and CXCR4. TANs produced substantial quantities of the proinflammatory factors MCP-1, IL-8, MIP-1α, and IL-6, as well as the antiinflammatory IL-1R antagonist. Functionally, both TANs and neutrophils isolated from distant nonmalignant lung tissue were able to stimulate T cell proliferation and IFN-γ release. Cross-talk between TANs and activated T cells led to substantial upregulation of CD54, CD86, OX40L, and 4-1BBL costimulatory molecules on the neutrophil surface, which bolstered T cell proliferation in a positive-feedback loop. Together our results demonstrate that in the earliest stages of lung cancer, TANs are not immunosuppressive, but rather stimulate T cell responses.

A road less traveled paved by IDO silencing: Harnessing the antitumor activity of neutrophils

Orchestrating a cytotoxic polymorphonuclear neutrophil (PMN) response strictly focused within the tumor tissue remains a formidable challenge for the successful therapeutic use of these cells. A Salmonella vector carrying an shRNA against indoleamine 2,3-dioxygenase has been shown to recruit PMNs and enhance their activation specifically in the tumor bed, resulting in significant anticancer effects.

Acute bacterial infection negatively impacts cancer specific survival of colorectal cancer patients

AIM: To assess the impact of bacterial infections on cancer-specific survival in patients with colorectal cancer.

METHODS: This was a retrospective cohort study of colorectal cancer patients treated at the A.C. Camargo Cancer Center between January 2006 and April 2010. The presence of bacterial infection during cancer treatment, or up to one year after, was confirmed by laboratory tests or by the physician. Infections of the urinary, respiratory or digestive tracts, bloodstream, skin or surgical site were defined by testing within a single laboratory. Criteria for exclusion from the study were: chronically immunosuppressed patients; transplant patients (due to chronic immunosuppression); human immunodeficiency virus carriers; chronic use of corticosteroids or other immunosuppressive drugs; patients with autoimmune disease or primary immunodeficiency; known viral or parasitic infections. Patients with infections that did not require hospitalization were not included in the study because of the difficulty of collecting and tracking data related to infectious processes. In addition, patients hospitalized for pulmonary thromboembolism, stroke, acute myocardial infarction, uncontrolled diabetes, malignant hypercalcemia or other serious non-infectious complications not directly related to infection were also excluded. Survival curves were plotted using the Kaplan-Meier method, and log-rank tests (univariate analysis) and a Cox test assuming a proportional hazards model (multivariate analysis) were performed to examine associations between clinical history and characteristics of infection with cancer-specific survival.

RESULTS: One-hundred and six patients with colorectal cancer were divided into two groups based on the presence or absence of bacterial infection. Patient ages ranged from 23 to 91 years, with a median of 55 years. The majority of patients were male (57/106, 53.77%) with stage III colorectal cancer (45/106, 44.11%). A total of 86 bacteriologic events were recorded. Results indicate that the presence and number of infections during or after the end of treatment were associated with poorer-cancer specific survivals (P = 0.02). Elevated neutrophil counts were also associated with poorer cancer-specific survival (P = 0.02). Analysis of patient age revealed that patients > 65 years of age had a poorer cancer-specific survival (P = 0.04). A multivariate analysis demonstrated that infection was an independent predictor of poor survival (HR = 2.62, 95%CI: 1.26-5.45; P = 0.01) along with advanced clinical staging (HR = 2.63, 95%CI: 1.08-6.39; P = 0.03).

CONCLUSION: Infection and high neutrophil counts are associated with a poorer cancer-specific survival in colorectal cancer patients.

Gene expression profiling for targeted cancer treatment

INTRODUCTION

There is certain degree of frustration and discontent in the area of microarray gene expression data analysis of cancer datasets. It arises from the mathematical problem called 'curse of dimensionality,' which is due to the small number of samples available in training sets, used for calculating transcriptional signatures from the large number of differentially expressed (DE) genes, measured by microarrays. The new generation of causal reasoning algorithms can provide solutions to the curse of dimensionality by transforming microarray data into activity of a small number of cancer hallmark pathways. This new approach can make feature space dimensionality optimal for mathematical signature calculations.

AREAS COVERED

The author reviews the reasons behind the current frustration with transcriptional signatures derived from DE genes in cancer. He also provides an overview of the novel methods for signature calculations based on differentially variable genes and expression regulators. Furthermore, the authors provide perspectives on causal reasoning algorithms that use prior knowledge about regulatory events described in scientific literature to identify expression regulators responsible for the differential expression observed in cancer samples.

EXPERT OPINION

The author advocates causal reasoning methods to calculate cancer pathway activity signatures. The current challenge for these algorithms is in ensuring quality of the knowledgebase. Indeed, the development of cancer hallmark pathway collections, together with statistical algorithms to transform activity of expression regulators into pathway activity, are necessary for causal reasoning to be used in cancer research.

Neutrophil extracellular traps in cancer progression

Neutrophils are being increasingly recognized as an important element in tumor progression. They have been shown to exert important effects at nearly every stage of tumor progression with a number of studies demonstrating that their presence is critical to tumor development. Novel aspects of neutrophil biology have recently been elucidated and its contribution to tumorigenesis is only beginning to be appreciated. Neutrophil extracellular traps (NETs) are neutrophil-derived structures composed of DNA decorated with antimicrobial peptides. They have been shown to trap and kill microorganisms, playing a critical role in host defense. However, their contribution to tumor development and metastasis has recently been demonstrated in a number of studies highlighting NETs as a potentially important therapeutic target. Here, studies implicating NETs as facilitators of tumor progression and metastasis are reviewed. In addition, potential mechanisms by which NETs may exert these effects are explored. Finally, the ability to target NETs therapeutically in human neoplastic disease is highlighted.

Keratin pearl degradation in oral squamous cell carcinoma: reciprocal roles of neutrophils and macrophages

BACKGROUND

We have reported that neutrophilic infiltration was associated with round-shaped dyskeratosis foci, a kind of keratin pearl, of oral carcinoma in situ and that those inflammatory cells are recruited from intra-epithelially entrapped blood vessels. Based on these lines of evidence, we have formulated a hypothesis that keratin pearls are terminally degraded by neutrophils. To confirm this hypothesis, we investigated immunohistochemically stepwise degradation of keratin pearls in oral squamous cell carcinoma (SCC) to clarify any other type scavenger cells in addition to neutrophils are involved in this particular degradation process.

METHODS

Neutrophils (neutrophil elastase) and macrophage subpopulations (CD68, CD163 and CD204) were immunohistochemically localized in 30 cases of oral SCC with typical round-shaped keratin pearls. SCC cells were revealed by immunohistochemistry for keratin (K) 17, and blood vessels were demonstrated by CD31.

RESULTS

Keratin pearl degradation process was divided into four steps: (i) intact stage: no macrophage infiltration but minimal neutrophils were found in keratin pearls; (ii) neutrophil recruit stage: no macrophage infiltration but focal neutrophilic infiltration within the pearls; (iii) neutrophil predominant stage: dense neutrophil infiltration with minimal macrophages and segregated keratinized cancer cells strongly positive for K17; and (iv) macrophage predominant stage: dense infiltration of CD68-, CD163 (mononuclear)- and CD204 (multinucleated)-positive macrophages engulfing detached keratinized SCC cells.

CONCLUSION

Keratin pearl degradation in oral SCC is strictly regulated by two types of scavenger cells: neutrophils, which perform initial tasks, and macrophages, which reciprocally take over from neutrophils the role to finalize the degradation processes.

The Multifaceted Roles Neutrophils Play in the Tumor Microenvironment

Neutrophils are myeloid cells that constitute 50-70 % of all white blood cells in the human circulation. Traditionally, neutrophils are viewed as the first line of defense against infections and as a major component of the inflammatory process. In addition, accumulating evidence suggest that neutrophils may also play a key role in multiple aspects of cancer biology. The possible involvement of neutrophils in cancer prevention and promotion was already suggested more than half a century ago, however, despite being the major component of the immune system, their contribution has often been overshadowed by other immune components such as lymphocytes and macrophages. Neutrophils seem to have conflicting functions in cancer and can be classified into anti-tumor (N1) and pro-tumor (N2) sub-populations. The aim of this review is to discuss the varying nature of neutrophil function in the cancer microenvironment with a specific emphasis on the mechanisms that regulate neutrophil mobilization, recruitment and activation.

Neutrophil cathepsin G, but not elastase, induces aggregation of MCF-7 mammary carcinoma cells by a protease activity-dependent cell-oriented mechanism

We previously found that a neutrophil serine protease, cathepsin G, weakens adherence to culture substrates and induces E-cadherin-dependent aggregation of MCF-7 human breast cancer cells through its protease activity. In this study, we examined whether aggregation is caused by degradation of adhesion molecules on the culture substrates or through an unidentified mechanism. We compared the effect of treatment with cathepsin G and other proteases, including neutrophil elastase against fibronectin- (FN-) coated substrates. Cathepsin G and elastase potently degraded FN on the substrates and induced aggregation of MCF-7 cells that had been subsequently seeded onto the substrate. However, substrate-bound cathepsin G and elastase may have caused cell aggregation. After inhibiting the proteases on the culture substrates using the irreversible inhibitor phenylmethylsulfonyl fluoride (PMSF), we examined whether aggregation of MCF-7 cells was suppressed. PMSF attenuated cell aggregation on cathepsin G-treated substrates, but the effect was weak in cells pretreated with high concentrations of cathepsin G. In contrast, PMSF did not suppress cell aggregation on elastase-treated FN. Moreover, cathepsin G, but not elastase, induced aggregation on poly-L-lysine substrates which are not decomposed by these enzymes, and the action of cathepsin G was nearly completely attenuated by PMSF. These results suggest that cathepsin G induces MCF-7 aggregation through a cell-oriented mechanism.

Neutrophils recruit regulatory T-cells into tumors via secretion of CCL17--a new mechanism of impaired antitumor immunity

The mechanisms by which tumor-associated neutrophils (TANs) affect tumor growth are to a large extent unknown. Regulatory T-cells (T-regs) are functionally immune-suppressive subsets of T-cells. Depletion or inhibition of T-regs can enhance antitumor immunity. We demonstrated both by RT-PCR and by ELISA that murine TANs secrete significant amounts of the T-regs chemoattractant, CCL17, much more than circulating or splenic neutrophils, and at a level progressively increasing during tumor development. Migration assays, both in vitro and in vivo, showed recruitment of T-regs by TANs, which was inhibited with anti-CCL17 monoclonal antibodies. Systemic neutrophil depletion in tumor-bearing mice using anti-Ly6G monoclonal antibodies reduced the migration of T-regs into the tumors. We further showed, using flow cytometry, that CCL17 secretion by TANs is not limited to mouse models of cancer but is also relevant to human TANs. Our results suggest a new indirect mechanism by which TANs may inhibit antitumor immune activity, thus promoting tumor growth. We further describe, for the first time, a clear link between TANs and T-regs acting together to impair antitumor immunity.

Effectiveness of slow-release systems in CD40 agonistic antibody immunotherapy of cancer

Slow-release delivery has great potential for specifically targeting immune-modulating agents into the tumor-draining area. In prior work we showed that local treatment of slowly delivered anti-CD40 antibody induced robust anti-tumor CD8+ T cell responses without systemic toxicity. We now report on the comparison of two slow-release delivery systems for their use in antibody-based immunotherapy of cancer. Anti-CD40 agonistic antibody delivered locally in mineral oil Montanide ISA 51 or in dextran-based microparticles activated tumor-specific T cell activation. Both slow-release formulations significantly decreased systemic side-effects compared to systemic administration of anti-CD40 antibody. However, dextran-based microparticles caused serious local inflammation associated with unwanted rapid outgrowth of tumors instead of the tumor clearance observed with delivery in Montanide. We therefore conclude that Montanide ISA 51 is to be preferred as a slow-release agent for CD40 agonist immunotherapy of cancer.

Advances in radiotherapy and targeted therapies for rectal cancer

The last decade witnessed a significant progress in understanding the biology and immunology of colorectal cancer alongside with the technical innovations in radiotherapy. The stepwise implementation of intensity-modulated and image-guided radiation therapy by means of megavolt computed tomography and helical tomotherapy enabled us to anatomically sculpt dose delivery, reducing treatment related toxicity. In addition, the administration of a simultaneous integrated boost offers excellent local control rates. The novel challenge is the development of treatment strategies for medically inoperable patient and organ preserving approaches. However, distant control remains unsatisfactory and indicates an urgent need for biomarkers that predict the risk of tumor spread. The expected benefit of targeted therapies that exploit the tumor genome alone is so far hindered by high cost techniques and pharmaceuticals, hence hardly justifying rather modest improvements in patient outcomes. On the other hand, the immune landscape of colorectal cancer is now better clarified with regard to the immunosuppressive network that promotes immune escape. Both N2 neutrophils and myeloid-derived suppressor cells (MDSC) emerge as useful clinical biomarkers of poor prognosis, while the growing list of anti-MDSC agents shows promising ability to boost antitumor T-cell immunity in preclinical settings. Therefore, integration of genetic and immune biomarkers is the next logical step towards effective targeted therapies in the context of personalized cancer treatment.

Tumor-associated neutrophils (TAN) develop pro-tumorigenic properties during tumor progression

The role and characteristics of tumor-associated neutrophils (TAN) in cancer are poorly defined. We have recently shown that TAN can have anti-tumorigenic (N1) or pro-tumorigenic (N2) functions. An interesting unanswered question is how the phenotype of TAN is influenced by the ongoing evolvement of tumor microenvironment. We therefore studied the phenotype and effects of TAN at different time points during tumor progression. We used two models of murine tumor cancer cell lines-Lewis lung carcinoma (LLC) and AB12 (mesothelioma). Neutrophils were studied at early and late stages and compared to each other and to neutrophils from bone marrow/periphery of naïve mice. Although there was no difference in the number of neutrophils entering the tumor, we found that at early stages of tumor development, neutrophils were almost exclusively at the periphery of the tumor. Only at later stages, neutrophils were also found scattered among the tumor cells. We further found that TAN from early tumors are more cytotoxic toward tumor cells and produce higher levels of TNF-α, NO and H2O2. In established tumors, these functions are down-regulated and TAN acquire a more pro-tumorigenic phenotype. In line with this phenotype, only depletion of neutrophils at later stages of tumor development inhibited tumor growth, possibly due to their central location in the tumor. Our work adds another important layer to the understanding of neutrophils in cancer by further characterizing the changes in TAN during time. Additional research on the functional role of TAN and differences between subsets of TAN is currently underway.

The multifaceted functions of neutrophils

Neutrophils and neutrophil-like cells are the major pathogen-fighting immune cells in organisms ranging from slime molds to mammals. Central to their function is their ability to be recruited to sites of infection, to recognize and phagocytose microbes, and then to kill pathogens through a combination of cytotoxic mechanisms. These include the production of reactive oxygen species, the release of antimicrobial peptides, and the recently discovered expulsion of their nuclear contents to form neutrophil extracellular traps. Here we discuss these primordial neutrophil functions, which also play key roles in tissue injury, by providing details of neutrophil cytotoxic functions and congenital disorders of neutrophils. In addition, we present more recent evidence that interactions between neutrophils and adaptive immune cells establish a feed-forward mechanism that amplifies pathologic inflammation. These newly appreciated contributions of neutrophils are described in the setting of several inflammatory and autoimmune diseases.

The parity-associated microenvironmental niche in the omental fat band is refractory to ovarian cancer metastasis

Ovarian cancer is an insidious and aggressive disease of older women, typically undiscovered before peritoneal metastasis due to its asymptomatic nature and lack of early detection tools. Epidemiologic studies suggest that child-bearing (parity) is associated with decreased ovarian cancer risk, although the molecular mechanisms responsible for this phenomenon have not been delineated. Ovarian cancer preferentially metastasizes to the omental fat band (OFB), a secondary lymphoid organ that aids in filtration of the peritoneal serous fluid (PSF) and helps combat peritoneal infections. In the present study, we assessed how parity and age impact the immune compositional profile in the OFB of mice, both in the homeostatic state and as a consequence of peritoneal implantation of ovarian cancer. Using fluorescence-activated cell sorting analysis and quantitative real-time PCR, we found that parity was associated with a significant reduction in omental monocytic subsets and B1-B lymphocytes, correlating with reduced homeostatic expression levels of key chemoattractants and polarization factors (Ccl1, Ccl2, Arg1, and Cxcl13). Of note, parous animals exhibited significantly reduced tumor burden following intraperitoneal implantation compared with nulliparous animals. This was associated with a reduction in tumor-associated neutrophils and macrophages, as well as in the expression levels of their chemoattractants (Cxcl1 and Cxcl5) in the OFB and PSF. These findings define a preexisting "parity-associated microenvironmental niche" in the OFB that is refractory to metastatic tumor seeding and outgrowth. Future studies designed to manipulate this niche may provide a novel means to mitigate peritoneal dissemination of ovarian cancer.

Increase in sialylation and branching in the mouse serum N-glycome correlates with inflammation and ovarian tumour progression

Ovarian cancer is the most lethal gynaecological cancer and is often diagnosed in late stage, often as the result of the unavailability of sufficiently sensitive biomarkers for early detection, tumour progression and tumour-associated inflammation. Glycosylation is the most common posttranslational modification of proteins; it is altered in cancer and therefore is a potential source of biomarkers. We investigated the quantitative and qualitative effects of anti-inflammatory (acetylsalicylic acid) and pro-inflammatory (thioglycolate and chlorite-oxidized oxyamylose) drugs on glycosylation in mouse cancer serum. A significant increase in sialylation and branching of glycans in mice treated with an inflammation-inducing compound was observed. Moreover, the increases in sialylation correlated with increased tumour sizes. Increases in sialylation and branching were consistent with increased expression of sialyltransferases and the branching enzyme MGAT5. Because the sialyltransferases are highly conserved among species, the described changes in the ovarian cancer mouse model are relevant to humans and serum N-glycome analysis for monitoring disease treatment and progression might be a useful biomarker.

The role played by the microenvironment in site-specific metastasis

Cancer cells that disseminate to metastatic sites may progress to frank metastasis or persist as dormant micrometastasis. Significant progress has been made in defining the genetic and phenotypic cancer-cell-autonomous determinants of metastasis and in the understanding of the cross-talk between metastasizing tumor cells and the metastatic microenvironment. However several questions remain open, in particular the identity of microenvironmental factors that keep micrometastatic cells in a state of dormancy and those that promote survival, proliferation and progression of such cells. Significantly more information is available on the latter factors than on microenvironmental cells and molecules that restrain micrometastasis. This mini-review summarizes findings suggesting that: In view of the above, it is not unlikely that metastases residing in different microenvironments may require "individualized" treatment modalities.

Emerging roles of immune cells in luteal angiogenesis

In the mammalian ovary, the corpus luteum (CL) is a unique transient endocrine organ displaying rapid angiogenesis and time-dependent accumulation of immune cells. The CL closely resembles 'transitory tumours', and the rate of luteal growth equals that of the fastest growing tumours. Recently, attention has focused on multiple roles of immune cells in luteal function, not only in luteolysis (CL disruption by immune responses involving T lymphocytes and macrophages), but also in CL development (CL remodelling by different immune responses involving neutrophils and macrophages). Neutrophils and macrophages regulate angiogenesis, lymphangiogenesis, and steroidogenesis by releasing cytokines in the CL. In addition, functional polarisation of neutrophils (proinflammatory N1 vs anti-inflammatory N2) and macrophages (proinflammatory M1 vs anti-inflammatory M2) has been demonstrated. This new concept concurs with the phenomenon of immune function within the luteal microenvironment: active development of the CL infiltrating anti-inflammatory N2 and M2 versus luteal regression together with proinflammatory N1 and M1. Conversely, excessive angiogenic factors and leucocyte infiltration result in indefinite disordered tumour development. However, the negative feedback regulator vasohibin-1 in the CL prevents excessive tumour-like vasculogenesis, suggesting that CL development has well coordinated time-dependent mechanisms. In this review, we discuss the physiological roles of immune cells involved in innate immunity (e.g. neutrophils and macrophages) in the local regulation of CL development with a primary focus on the cow.

The human neutrophil subsets defined by the presence or absence of OLFM4 both transmigrate into tissue in vivo and give rise to distinct NETs in vitro

Neutrophil heterogeneity was described decades ago, but it could not be elucidated at the time whether the existence of different neutrophil subsets had any biological relevance. It has been corroborated in recent years that neutrophil subsets, defined by differential expression of various markers, are indeed present in human blood, calling for renewed attention to this question. The expression of the granule protein olfactomedin 4 (OLFM4) has been suggested to define two such neutrophil subsets. We confirm the simultaneous presence of one OLFM4-positive and one OLFM4-negative neutrophil subpopulation as well as the localization of the protein to specific granules. In vitro, these neutrophil subsets displayed equal tendency to undergo apoptosis and phagocytose bacteria. In addition, the subpopulations were recruited equally to inflammatory sites in vivo, and this was true both in an experimental model of acute inflammation and in naturally occurring pathological joint inflammation. In line with its subcellular localization, only limited OLFM4 release was seen upon in vivo transmigration, and release through conventional degranulation required strong secretagogues. However, extracellular release of OLFM4 could be achieved upon formation of neutrophil extracellular traps (NETs) where it was detected only in a subset of the NETs. Although we were unable to demonstrate any functional differences between the OLFM4-defined subsets, our data show that different neutrophil subsets are present in inflamed tissue in vivo. Furthermore, we demonstrate NETs characterized by different markers for the first time, and our results open up for functions of OLFM4 itself in the extracellular space through exposure in NETs.

Neutrophil extracellular traps sequester circulating tumor cells and promote metastasis

The majority of patients with cancer undergo at least one surgical procedure as part of their treatment. Severe postsurgical infection is associated with adverse oncologic outcomes; however, the mechanisms underlying this phenomenon are unclear. Emerging evidence suggests that neutrophils, which function as the first line of defense during infections, facilitate cancer progression. Neutrophil extracellular traps (NETs) are extracellular neutrophil-derived DNA webs released in response to inflammatory cues that trap and kill invading pathogens. The role of NETs in cancer progression is entirely unknown. We report that circulating tumor cells become trapped within NETs in vitro under static and dynamic conditions. In a murine model of infection using cecal ligation and puncture, we demonstrated microvascular NET deposition and consequent trapping of circulating lung carcinoma cells within DNA webs. NET trapping was associated with increased formation of hepatic micrometastases at 48 hours and gross metastatic disease burden at 2 weeks following tumor cell injection. These effects were abrogated by NET inhibition with DNAse or a neutrophil elastase inhibitor. These findings implicate NETs in the process of cancer metastasis in the context of systemic infection and identify NETs as potential therapeutic targets.

Influence of human immune cells on cancer: studies at the University of Colorado

There will be over half a million cancer-related deaths in the United States in 2012, with lung cancer being the leader followed by prostate in men and breast in women. There is estimated to be more than one and a half million new cases of cancer in 2012, making the development of effective therapies a high priority. As tumor immunologists, we are interested in the development of immunotherapies because the immune response offers exquisite specificity and the potential to target tumor cells without harming normal cells. In this review, we highlight the current advances in the field of immunotherapy and the current work being completed by laboratories at University of Colorado School of Medicine in multiple malignancies, including breast cancer, lung cancer, melanoma, thyroid cancer, and glioblastoma. This work focuses on augmenting the anti-tumor response of CD8 T cells in the blood, lymph nodes, and tumors of patients, determining biomarkers for patients who are more likely to respond to immunotherapy, and identifying additional anti-tumor and immunosuppressive cells that influence the overall response to tumors. These collaborative efforts will identify mechanisms to improve immune function, which may elucidate therapeutic targets for clinical trials to improve patient health and survival.

Neutrophil heterogeneity in health and disease: a revitalized avenue in inflammation and immunity

Leucocytes form the principal cellular components of immunity and inflammation, existing as multiple subsets defined by distinct phenotypic and functional profiles. To date, this has most notably been documented for lymphocytes and monocytes. In contrast, as neutrophils are traditionally considered, to be short-lived, terminally differentiated cells that do not re-circulate, the potential existence of distinct neutrophil subsets with functional and phenotypic heterogeneity has not been widely considered or explored. A growing body of evidence is now challenging this scenario, and there is significant evidence for the existence of different neutrophil subsets under both physiological and pathological conditions. This review will summarize the key findings that have triggered a renewed interest in neutrophil phenotypic changes, both in terms of functional implications and consequences within disease models. Special emphasis will be placed on the potential pro- and anti-inflammatory roles of neutrophil subsets, as indicated by the recent works in models of ischaemia–reperfusion injury, trauma, cancer and sepsis.

Tumor stroma: a complexity dictated by the hypoxic tumor microenvironment

A lot of effort has been done to study how cancer cells react to low-oxygen tension, a condition known as hypoxia. Indeed, abnormal and dysfunctional blood vessels in the tumor are incapable to restore oxygenation, therefore perpetuating hypoxia, which, in turn, will fuel tumor progression, metastasis and resistance to antitumor therapies. Nevertheless, how stromal components including blood and lymphatic endothelial cells, pericytes and fibroblasts, as well as hematopoietic cells, respond to low-oxygen tension in comparison with their normoxic counterparts has been a matter of investigation in the last few years only and, to date, this field of research remains poorly understood. In general, opposing phenotypes can arise from the same stromal component when embedded in different tumor microenvironments, and, vice versa, different stromal components can have opposite reaction to the same tumor microenvironment. In this article, we will discuss the emerging link between tumor stroma and hypoxia, and how this complexity is translated at the molecular level.

VEGF-A recruits a proangiogenic MMP-9-delivering neutrophil subset that induces angiogenesis in transplanted hypoxic tissue

Recruitment and retention of leukocytes at a site of blood vessel growth are crucial for proper angiogenesis and subsequent tissue perfusion. Although critical for many aspects of regenerative medicine, the mechanisms of leukocyte recruitment to and actions at sites of angiogenesis are not fully understood. In this study, we investigated the signals attracting leukocytes to avascular transplanted pancreatic islets and leukocyte actions at the engraftment site. Expression of the angiogenic stimulus VEGF-A by mouse pancreatic islets was elevated shortly after syngeneic transplantation to muscle. High levels of leukocytes, predominantly CD11b(+)/Gr-1(+)/CXCR4(hi) neutrophils, were observed at the site of engraftment, whereas VEGF-A-deficient islets recruited only half of the amount of leukocytes when transplanted. Acute VEGF-A exposure of muscle increased leukocyte extravasation but not the levels of SDF-1α. VEGF-A-recruited neutrophils expressed 10 times higher amounts of MMP-9 than neutrophils recruited to an inflammatory stimulus. Revascularization of islets transplanted to MMP-9-deficient mice was impaired because blood vessels initially failed to penetrate grafts, and after 2 weeks vascularity was still disturbed. This study demonstrates that VEGF-A recruits a proangiogenic circulating subset of CD11b(+)/Gr-1(+) neutrophils that are CXCR4(hi) and deliver large amounts of the effector protein MMP-9, required for islet revascularization and functional integration after transplantation.

The biology of personalized cancer medicine: facing individual complexities underlying hallmark capabilities

It is a time of great promise and expectation for the applications of knowledge about mechanisms of cancer toward more effective and enduring therapies for human disease. Conceptualizations such as the hallmarks of cancer are providing an organizing principle with which to distill and rationalize the abject complexities of cancer phenotypes and genotypes across the spectrum of the human disease. A countervailing reality, however, involves the variable and often transitory responses to most mechanism-based targeted therapies, returning full circle to the complexity, arguing that the unique biology and genetics of a patient's tumor will in the future necessarily need to be incorporated into the decisions about optimal treatment strategies, the frontier of personalized cancer medicine. This perspective highlights considerations, metrics, and methods that may prove instrumental in charting the landscape of evaluating individual tumors so to better inform diagnosis, prognosis, and therapy. Integral to the consideration is remarkable heterogeneity and variability, evidently embedded in cancer cells, but likely also in the cell types composing the supportive and interactive stroma of the tumor microenvironment (e.g., leukocytes and fibroblasts), whose diversity in form, regulation, function, and abundance may prove to rival that of the cancer cells themselves. By comprehensively interrogating both parenchyma and stroma of patients' cancers with a suite of parametric tools, the promise of mechanism-based therapy may truly be realized.

Transcriptomic analysis comparing tumor-associated neutrophils with granulocytic myeloid-derived suppressor cells and normal neutrophils

The role of myeloid cells in supporting cancer growth is well established. Most work has focused on myeloid-derived suppressor cells (MDSC) that accumulate in tumor-bearing animals, but tumor-associated neutrophils (TAN) are also known to be capable of augmenting tumor growth. However, little is known about their evolution, phenotype, and relationship to naïve neutrophils (NN) and to the granulocytic fraction of MDSC (G-MDSC).

In the current study, a transcriptomics approach was used in mice to compare these cell types. Our data show that the three populations of neutrophils are significantly different in their mRNA profiles with NN and G-MDSC being more closely related to each other than to TAN. Structural genes and genes related to cell-cytotoxicity (i.e. respiratory burst) were significantly down-regulated in TAN. In contrast, many immune-related genes and pathways, including genes related to the antigen presenting complex (e.g. all six MHC-II complex genes), and cytokines (e.g. TNF-α, IL-1-α/β), were up-regulated in G-MDSC, and further up-regulated in TAN. Thirteen of the 25 chemokines tested were markedly up-regulated in TAN compared to NN, including striking up-regulation of chemoattractants for T/B-cells, neutrophils and macrophages.

This study characterizes different populations of neutrophils related to cancer, pointing out the major differences between TAN and the other neutrophil populations.

Regulatory dendritic cells in the tumor immunoenvironment

The tumor microenvironment is a pivotal factor in tumorigenesis, and especially in progression, as the pathogenesis of cancer critically depends on the complex interactions between various microenvironmental components. A key component of the tumor immunoenvironment is the infiltration of immune cells, which has been proven to play a dual role in tumor growth and progression. This Janus two-faced function of the tumor immunoenvironment is seen in tumor infiltration by T cells, which correlates with improved patient survival, but also with the homing of multiple subsets of immunoregulatory cells that inhibit the antitumor immune response. Regulatory dendritic cells (regDCs) have recently been shown to be induced by tumor-derived factors and represent a new and potentially important player in supporting tumor progression and suppressing the development of antitumor immune responses. Our recent data reveal that different tumor cell lines produce soluble factors that induce polarization of conventional DCs into regDCs, both in vitro and in vivo. These regDCs can suppress the proliferation of pre-activated T cells and are phenotypically and functionally different from their precursors as well as the classical immature conventional DCs. Understanding the biology of regDCs and the mechanisms of their formation in the tumor immunoenvironment will provide a new therapeutic target for re-polarizing protumorigenic immunoregulatory cells into proimmunogenic effector cells able to induce and support effective antitumor immunity.