Tumor hypoxia enhances Non-Small Cell Lung Cancer metastasis by selectively promoting macrophage M2 polarization through the activation of ERK signaling

Intratumoral fate of functional nanoparticles in response to microenvironment factor: Implications on cancer diagnosis and therapy

The extraordinary growth and progression of tumor require enormous nutrient and energy. Unregulated behaviors of cancer cell progressing and persistently change of tumor microenvironment (TME) which acts as the soil for cancer growth and metastasis are the ubiquitous features. The tumor microenvironment exhibits some unique features which differ with the normal tissues. While the nanoparticles get through the blood vessel leakage, they encounter immediately and interact directly with these microenvironment factors. These factors may inhibit the diffusion of nanoparticles from penetrating through the tumor, or induce the dissociation of nanoparticles. Different nanoparticles encountered with different intratumoral microenvironment factors end up in different way. Therefore, in this review, we first briefly introduced the formations, distributions, features of some intratumoral microenvironment, and their effects on the tumor progression. They include extracellular matrix (ECM), matrix metalloproteinases (MMPs), acidic/hypoxia environment, redox environment, and tumor associated macrophages (TAMs). We then exemplified how these factors interact with nanoparticles and emphasized the potentials and challenges of nanoparticle-based strategies facing in enhancing intratumoral penetration and tumor microenvironment remodeling. We hope to give a simple understanding of the interaction between these microenvironment factors and the nanoparticles, thus, favors the designing and constructing of more ideal functional nanoparticles.

miR-181a/b therapy in lung cancer: reality or myth?

Despite substantial progress in oncology, lung cancer remains the number one malignancy in terms of both incidence and mortality rates, and there thus remains an urgent need for new therapeutic alternatives. MicroRNA (miRNA) have an important role in cancer initiation and progression due to their capacity to interfere with transcriptional signaling and regulate key cellular processes. miR-181a and miR-181b (miR-181a/b), which are located on chromosomes 1 and 9, are pathologically expressed in the tumor tissue and plasma of patients diagnosed with lung cancer. The miR-181a/b regulatory mechanisms are sophisticated and are directly related to different target genes. In recent years, an ever-increasing number of studies have focused on the biological relevance of miR-181a/b in key cellular processes. In this paper, we aim to discuss the challenging experimental data related to miR-181a/b and their potential use for the development of new therapeutic approaches in lung cancer. We will further present the ongoing issues regarding the regulation of their multiple target genes, and their potential use as biomarkers and therapeutic targets in this deadly malignancy.

Krüppel like factor 6 splice variant 1 (KLF6-SV1) overexpression recruits macrophages to participate in lung cancer metastasis by up-regulating TWIST1

The aim of this study was to investigate the mechanism by which KLF6-SV1 promoted lung cancer metastasis through tumor-associated macrophages (TAMs). Plasmid transfection was used to construct cells that upregulated or silenced gene. Tumor-bearing mouse model was established using A549 cells. SP staining was performed to detect the CD163 and CD68. Six-well plates and Transwell chamber were used for co-culture of lung cancer A549 cells and macrophages. CCK-8 and Transwell assay were applied to detected the cell viability and migration respectively. Protein and mRNA were tested by Western blot and quantitative real-time polymerase chain reaction (qRT-PCR).KLF6-SV1 overexpression promoted the expression levels of TWIST1 and CCL2, and also induce macrophage polarization to M2 and epithelial-mesenchymal transition (EMT). In vitro experiments showed that KLF6-SV1 might regulate the migration of lung cancer cells by regulating the expression of TWIST1 and CCL-2. M2 macrophages did not affect the expression of KLF6-SV1, TWIST1 and CCL-2. The co-culture system could up-regulate the EMT of A549 cells.Overexpression of KLF6-SV1 promoted the expression of TWIST1 and CCL2, and up-regulation of TWIST1 expression might promote the infiltration of M2 macrophages, which promoted the involvement of EMT in the metastasis of lung cancer cells.

Static lung hyperinflation is an independent risk factor for lung cancer in patients with chronic obstructive pulmonary disease

INTRODUCTION

Static hyperinflation, a hallmark characteristic of some patients with chronic obstructive pulmonary disease, is related to higher mortality and cardiovascular morbidity. However, information about its association with lung cancer is scarce. Our aim was to evaluate whether static hyperinflation is associated with future risk of lung cancer in COPD patients.

METHODS

A cohort of 848 COPD patients recruited outside the hospital setting was monitored for an average period of 4.3 years, totaling 2858 person-years, regarding diagnosis of cancer of any origin or lung cancer. Static hyperinflation was defined by functional residual capacity measured by plethysmography greater than 120% of the predicted value.

RESULTS

The incidence rates for cancer of any origin and lung cancer were 16.0 (95%CI, 15.1-17.8) and 8.7 (95%CI, 7.7-9.8) per 1000 patient-years, respectively. Among the patients with lung cancer, non-small cell lung cancer predominated (88%). In a stepwise multivariate Cox regression model, body mass index (BMI), pack-years, Charlson index, and postbronchodilator FEV₁/FVC ratio were retained as independent predictors of cancer of any origin. In contrast, features associated with a future risk of lung cancer included older age, low BMI, increased pack-years and presence of static hyperinflation (adjusted hazard ratio: 4.617, 95%CI: 1.007-21.172, p = 0.049).

CONCLUSION

In a general COPD outpatient population, static hyperinflation is an independent risk factor for the development of lung cancer, which might contribute towards justifying the excess mortality identified in COPD patients with hyperinflation.

Sleep disordered breathing and nocturnal hypoxemia are very prevalent in a lung cancer screening population and may condition lung cancer screening findings: results of the prospective Sleep Apnea In Lung Cancer Screening (SAILS) study

OBJECTIVE

Obstructive sleep apnea (OSA) can influence the appearance and proliferation of some tumors. The Sleep Apnea In Lung Cancer Screening (SAILS) study (NCT02764866) evaluated the prevalence of OSA and nocturnal hypoxemia in a high-risk population enrolled in a lung cancer screening program.

METHODS

This was a prospective study of the prevalence of OSA in a lung cancer screening program. Subjects met the National Lung Screening Trial (NLST) age and smoking criteria (age 55-75 years; pack-years >30). Participants in the study were offered annual screening with low-dose computed tomography (LDCT) and pulmonary function testing, as well as home sleep apnea testing (HSAT) and a sleep-specific questionnaire. Sleep study-related variables, symptoms, and epidemiologic data were recorded.

RESULTS

HSAT was offered to 279 subjects enrolled in our lung cancer screening program. HSAT results were available for 236 participants (mean age 63.6 years; mean tobacco exposure: 45 pack-years), of whom 59% were male and 53% were active smokers. Emphysema (74%) and chronic obstructive pulmonary disease (COPD) (62%) were common and in most cases mild in severity. OSA, including moderate to severe disease, was very common in this patient population. AHI distributions were as follows: AHI <5 (22.5%); 5-15 (36.4%); 15-30 (23.3%); and >30 (17.8%). Nocturnal hypoxemia (T90) (p = 0.003), diffusing capacity for carbon monoxide (DLCO) (p = 0.01), tobacco exposure (p = 0.024), and COPD (p = 0.023) were associated with OSA severity. Positive screening findings (nodules ≥6 mm) were associated with nocturnal hypoxemia on multivariate analysis adjusted for confounders (OR = 2.6, 95% CI = 1.12-6.09, p = 0.027).

CONCLUSION

Moderate to severe OSA is very prevalent in patients enrolled in a lung cancer screening program. Nocturnal hypoxemia more than doubles the risk of positive screening findings.

Hypoxia Modifies the Transcriptome of Human NK Cells, Modulates Their Immunoregulatory Profile, and Influences NK Cell Subset Migration

Hypoxia, which characterizes most tumor tissues, can alter the function of different immune cell types, favoring tumor escape mechanisms. In this study, we show that hypoxia profoundly acts on NK cells by influencing their transcriptome, affecting their immunoregulatory functions, and changing the chemotactic responses of different NK cell subsets. Exposure of human peripheral blood NK cells to hypoxia for 16 or 96 h caused significant changes in the expression of 729 or 1,100 genes, respectively. Gene Set Enrichment Analysis demonstrated that these changes followed a consensus hypoxia transcriptional profile. As assessed by Gene Ontology annotation, hypoxia-targeted genes were implicated in several biological processes: metabolism, cell cycle, differentiation, apoptosis, cell stress, and cytoskeleton organization. The hypoxic transcriptome also showed changes in genes with immunological relevance including those coding for proinflammatory cytokines, chemokines, and chemokine-receptors. Quantitative RT-PCR analysis confirmed the modulation of several immune-related genes, prompting further immunophenotypic and functional studies. Multiplex ELISA demonstrated that hypoxia could variably reduce NK cell ability to release IFNγ, TNFα, GM-CSF, CCL3, and CCL5 following PMA+Ionomycin or IL15+IL18 stimulation, while it poorly affected the response to IL12+IL18. Cytofluorimetric analysis showed that hypoxia could influence NK chemokine receptor pattern by sustaining the expression of CCR7 and CXCR4. Remarkably, this effect occurred selectively (CCR7) or preferentially (CXCR4) on CD56^bright NK cells, which indeed showed higher chemotaxis to CCL19, CCL21, or CXCL12. Collectively, our data suggest that the hypoxic environment may profoundly influence the nature of the NK cell infiltrate and its effects on immune-mediated responses within tumor tissues.

Exosomes derived from hypoxic epithelial ovarian cancer cells deliver microRNAs to macrophages and elicit a tumor-promoted phenotype

Recently, cancer has been considered to be a complex system that includes the tumor microenvironment (TME). Tumor-associated macrophages (TAMs) are the most common immune-related stromal cells in the TME, and communication between cancer cells and TAMs is crucial for the progression of epithelial ovarian cancer (EOC). In this study, we revealed that exosomes derived from EOC cells remodel macrophages to a tumor-promoted phenotype, namely TAMs. In addition, hypoxic microenvironments have been postulated to facilitate this process in the TME, and hypoxia-inducible factors (HIFs) play an important role in this process. We found that TAMs educated by hypoxic exosomes derived from EOC cells promote tumor proliferation and migration in a feedback loop. Based on microarray analysis of normoxic and hypoxic exosomes, we discovered that a panel of miRNAs was enriched in hypoxic exosomes. And these three highly expressed miRNAs were induced by hypoxia via HIFs. In this study, we revealed that under hypoxic conditions, EOC cell-derived exosomes deliver miRNAs to induce M2 macrophage polarization, which promotes EOC cell proliferation and migration. This study suggests that these exosomes and associated miRNAs might serve as targets for novel treatments or diagnostic biomarkers for EOC.

Tumor-associated macrophages promote the metastasis of ovarian carcinoma cells by enhancing CXCL16/CXCR6 expression

This study investigated the underlying mechanism by which C-X-C motif chemokine ligand 16 (CXCL16)/C-X-C motif chemokine receptor 6 (CXCR6) signaling is activated by tumor-associated macrophages and assists in regulating the metastasis of ovarian carcinoma. Specimens of ovarian carcinoma tissue and adjacent tissue were collected from 20 ovarian carcinoma patients. Human THP-1 cells were induced to differentiate into macrophages, which were then co-cultured with SKOV3 cells and low concentrations of tumor necrosis factor-α (TNF-α) to simulate the inflammatory microenvironment of ovarian carcinoma. Additionally, small interfering RNA (siRNA) targeting CXCR6 was transfected into SKOV3 cells; after which, the levels of nuclear factor kappa B p65 (NF-κB p65) protein and phosphorylated PI3K and Akt were measured. The migration and invasion abilities of the SKOV3 cells were also tested. The levels of TNF-α, interluekin-6 (IL-6), NF-κB p65, CXCL16, and CXCR6 expression in the ovarian carcinoma tissues were higher than those in the precancerous tissues. CXCR6 expression was positively correlated with TNF-α, IL-6, and CXCL16 expression. Co-culture of SKOV3 cells with macrophages significantly promoted CXCL16, CXCR6, NF-κB, and p65 expression by the SKOV3 cells, increased their levels of phosphorylated PI3K and Akt, and increased the migration and invasion abilities of SKOV3 cells. Silencing of CXCR6 or blocking the PI3K/Akt signal pathway markedly attenuated the expression of NF-κB p65 and phosphorylation of PI3K and Akt, as well as the migration and invasion abilities of SKOV3 cells. These findings demonstrate that macrophages can promote the migration and invasion of ovarian carcinoma cells by affecting the CXCL16/CXCR6 pathway.

Coagulation Factor X Regulated by CASC2c Recruited Macrophages and Induced M2 Polarization in Glioblastoma Multiforme

Tumor-associated macrophages (TAMs) constitute a major component of inflammatory cells in the glioblastoma multiforme (GBM) tumor microenvironment. TAMs have been implicated in GBM angiogenesis, invasion, local tumor recurrence, and immunosuppression. Coagulation factor X (FX) is a vitamin K-dependent plasma protein that plays a role in the regulation of blood coagulation. In this study, we first found that FX was highly expressed and positively correlated with TAM density in human GBM. FX exhibited a potent chemotactic capacity to recruit macrophages and promoted macrophages toward M2 subtype polarization, accelerating GBM growth. FX bound to extracellular signal-related kinase (ERK)1/2 and inhibited p-ERK1/2 in GBM cells. FX was secreted in the tumor microenvironment and increased the phosphorylation and activation of ERK1/2 and AKT in macrophages, which may have been responsible for the M2 subtype macrophage polarization. Moreover, although the lncRNA CASC2c has been verified to function as a miR-101 competing endogenous RNA (ceRNA) to promote miR-101 target genes in GBM cells, we first confirmed that CASC2c did not function as a miR-338-3p ceRNA to promote FX expression, and that FX was a target gene of miR-338-3p. CASC2c interacted with and reciprocally repressed miR-338-3p. Both CASC2c and miR-388-3p bound to FX and commonly inhibited its expression and secretion. CASC2c repressed M2 subtype macrophage polarization. Taken together, our findings revealed a novel mechanism highlighting CASC2c and FX as potential therapeutic targets to improve GBM patients by altering the GBM microenvironment.

Hypoxia restrains the expression of complement component 9 in tumor-associated macrophages promoting non-small cell lung cancer progression

The tumor microenvironment, including stroma cells, signaling molecules, and the extracellular matrix, critically regulates the growth and survival of cancer cells. Dissecting the active molecules in tumor microenvironment may uncover the key factors that can impact cancer progression. Human NSCLC tumor tissue-conditioned medium (TCM) and adjacent nontumor tissue-conditioned medium (NCM) were used to treat two NSCLC cells LSC1 and LAC1, respectively. Cell growth and foci formation assays were applied to assess the effects of TCM and NCM on cancer cells. The active factors were identified by protein mass spectrometry. Cell growth and foci formation assays showed that 8 of 26 NCM and none of TCM could effectively lead to tumor cell lysis, which was known as tumoricidal activity. And then protein mass spectrometry analysis and functional verifications confirmed that complement component 9 (C9) played a crucial role in the complement-dependent cytotoxicity (CDC)-mediated tumoricidal activity in vitro. Furthermore, immunofluorescent staining revealed that C9 specifically expressed in most alveolar macrophages (AMs) in adjacent lung tissues and a small fraction of tumor-associated macrophages (TAMs) in NSCLC tissues. Most importantly, the percentage of C9-positive cells in AMs or TAMs was responsible for the tumoricidal activity of NCM and TCM. Herein, we found that high expression of C9 in TAMs was a significant independent prognostic factor (P = 0.029), and associated with beneficial overall survival (P = 0.012) and disease-free survival (P = 0.016) for patients with NSCLC. Finally, we unveiled that hypoxic tumor microenvironment could switch the phenotype of macrophages from M1 to M2 forms, accompanying with the downregulation of C9 in TAMs. Collectively, our findings elucidated a novel role of TAMs expressing C9 in the prognosis of NSCLC patients, which provided a promising strategy in the development of anticancer treatments based on the CDC-mediated tumoricidal activity.

Differences of tumor microenvironment between stage I lepidic-positive and lepidic-negative lung adenocarcinomas

OBJECTIVE

Lepidic growth is a noninvasive component of lung adenocarcinoma. Many adenocarcinoma cases contain coexistent lepidic and nonlepidic (invasive) components (lepidic-growth positive [Lep+] adenocarcinoma); however, some cases comprise only nonlepidic components (lepidic-growth negative [Lep-] adenocarcinoma). The aim of this study was to investigate the biological differences between the invasive components of Lep+ and Lep- adenocarcinoma.

METHODS

We investigated the clinicopathologic characteristics of 232 adenocarcinomas (116 size-matched tumor pairs from Lep+ and Lep- adenocarcinomas). We then evaluated the cancer cell-specific expression levels of cancer stem cell, hypoxia, and invasion molecules in these lesions. The number of tumor-promoting stromal cells, including podoplanin-positive cancer-associated fibroblasts and CD204-positive tumor-associated macrophages, was also analyzed.

RESULTS

Among cases with size-matched invasive components, significant differences were shown in total tumor size and predominant subtype in invasive component between Lep+ and Lep- adenocarcinomas. The expression levels of hypoxia-related molecules were significantly lower in Lep+ adenocarcinomas (glucose transporter 1: 0 vs 10, P < .01; carbonic anhydrase IX: 0 vs 0 [mean, 4.7 vs 14.1], P = .01). The number of podoplanin-positive cancer-associated fibroblasts and CD204-positive tumor-associated macrophages was significantly lower in Lep+ adenocarcinomas (podoplanin-positive cancer-associated fibroblasts: 0 vs 0 [mean: 1.6 vs 11.6], P < .01; CD204-positive tumor-associated macrophages: 8.7 vs 24.7, P < .01).

CONCLUSIONS

Our results indicated that lower cancer cell-specific expression levels of hypoxia markers and a smaller number of tumor-promoting stromal cells in invasive component were characteristic features of Lep+ adenocarcinomas.

Implications of macrophage polarization in autoimmunity

Macrophages are extremely heterogeneous and plastic cells with an important role not only in physiological conditions, but also during inflammation (both for initiation and resolution). In the early 1990s, two different phenotypes of macrophages were described: one of them called classically activated (or inflammatory) macrophages (M1) and the other alternatively activated (or wound-healing) macrophages (M2). Currently, it is known that functional polarization of macrophages into only two groups is an over-simplified description of macrophage heterogeneity and plasticity; indeed, it is necessary to consider a continuum of functional states. Overall, the current available data indicate that macrophage polarization is a multifactorial process in which a huge number of factors can be involved producing different activation scenarios. Once a macrophage adopts a phenotype, it still retains the ability to continue changing in response to new environmental influences. The reversibility of polarization has a critical therapeutic value, especially in diseases in which an M1/M2 imbalance plays a pathogenic role. In this review, we assess the high plasticity of macrophages and their potential to be exploited to reduce chronic/detrimental inflammation. On the whole, the evidence detailed in this review underscores macrophage polarization as a target of interest for immunotherapy.

Imatinib prevents lung cancer metastasis by inhibiting M2-like polarization of macrophages

Although M2-like tumor-associated macrophages (TAMs) have been considered as a vital therapeutic target in cancer therapy due to their role in promoting tumor progression and metastasis, very few compounds have been identified to inhibit M2-like polarization of TAMs. Here, we showed that Imatinib significantly prevented macrophage M2-like polarization induced by IL-13 or IL-4 in vitro, as illustrated by reduced expression of cell surface marker CD206 and M2-like genes, including Arg1, Mgl2, Mrc1, CDH1, and CCL2. Further, the migration of lung cancer cells promoted by the conditioned medium from M2-like macrophages could be restrained by Imatinib. Mechanistically, Imatinib inhibited STAT6 phosphorylation and nuclear translocation, resulting in the macrophage M2-like polarization arrest. Furthermore, Imatinib reduced the number of metastasis of Lewis lung cancer without affecting tumor growth. Both in tumor and lung tissues, the percentage of M2-like macrophages decreased after the administration of Imatinib for one week. Taken together, these data suggest that Imatinib is able to inhibit macrophage M2-like polarization, which plays a vital role in Imatinib suppressed metastasis of Lewis lung cancer.

Podoplanin-positive cancer-associated fibroblast recruitment within cancer stroma is associated with a higher number of single nucleotide variants in cancer cells in lung adenocarcinoma

PURPOSE

Podoplanin-positive cancer-associated fibroblasts (CAFs) play an essential role in tumor progression. However, it is still unclear whether specific genomic alterations of cancer cells are required to recruit podoplanin-positive CAFs. The aim of this study was to investigate the relationship between the mutation status of lung adenocarcinoma cells and the presence of podoplanin-positive CAFs.

METHODS

Ninety-seven lung adenocarcinomas for which whole exome sequencing data were available were enrolled. First, we analyzed the clinicopathological features of the cases, and then, evaluated the relationship between genetic features of cancer cells (major driver mutations and the number of single nucleotide variants, SNVs) and the presence of podoplanin-positive CAFs.

RESULTS

The presence of podoplanin-positive CAFs was associated with smoking history, solid predominant subtype, and lymph node metastasis. We could not find any significant correlations between major genetic mutations (EGFR, KRAS, TP53, MET, ERBB2, BRAF, and PIC3CA) in cancer cells and the presence of podoplanin-positive CAFs. However, cases with podoplanin-positive CAFs had a significantly higher number of SNVs in cancer cells than the podoplanin-negative CAFs cases (median 84 vs 37, respectively; p = 0.001). This was also detected in a non-smoker subgroup (p = 0.037). Multivariate analyses revealed that the number of SNVs in cancer cells was the only statistically significant independent predictor for the presence of podoplanin-positive CAFs (p = 0.044).

CONCLUSIONS

In lung adenocarcinoma, the presence of podoplanin-positive CAFs was associated with higher numbers of SNVs in cancer cells, suggesting a relationship between accumulations of SNVs in cancer cells and the generation of a tumor-promoting microenvironment.

Redirecting tumor-associated macrophages to become tumoricidal effectors as a novel strategy for cancer therapy

Cancer research in recent decades has highlighted the potential influence of the tumor microenvironment on the progression and metastasis of most known cancer types. Within the established microenvironment, tumor-associated macrophages (TAMs) are one of the most abundant and crucial non-neoplastic cell types. The polarization of macrophages into tumor-suppressive M1 or tumor-promoting M2 types is a fundamental event in the establishment of the tumor microenvironment. Although ample evidence indicates that TAMs are primarily M2 polarized, the mechanisms responsible for the regulation and maintenance of M1 and M2 polarization imbalance remain unclear. The manipulation of this critical axis through three main approaches may provide new strategies for cancer therapy - (I) specific interference with M2-like TAM survival or inhibiting their signaling cascades, (II) repression of macrophage recruitment to tumors, and (III) repolarization of tumor-promoting M2-like TAMs to a tumoricidal M1-like phenotype. This review summarizes current strategies for cancer intervention via manipulation of macrophage polarization, with particular focus on composition of the tumor microenvironment and its influence on cancer progression and metastasis. It is clear that additional fundamental and preclinical research is required to confirm the efficacy and practicality of this novel and promising strategy for treating cancer.

Tumor-derived lactate induces M2 macrophage polarization via the activation of the ERK/STAT3 signaling pathway in breast cancer

Tumor-associated macrophages (TAM) are prominent components of tumor microenvironment (TME) and capable of promoting cancer progression. However, the mechanisms for the formation of M2-like TAMs remain enigmatic. Here, we show that lactate is a pivotal oncometabolite in the TME that drives macrophage M2-polarization to promote breast cancer proliferation, migration, and angiogenesis. In addition, we identified that the activation of ERK/STAT3, major signaling molecules in the lactate signaling pathway, deepens our molecular understanding of how lactate educates TAMs. Moreover, suppression of ERK/STAT3 signaling diminished tumor growth and angiogenesis by abolishing lactate-induced M2 macrophage polarization. Finally, research data of the natural compound withanolide D provide evidence for ERK/STAT3 signaling as a potential therapeutic strategy for the prevention and treatment of breast cancer. These findings suggest that the lactate-ERK/STAT3 signaling pathway is a driver of breast cancer progression by stimulating macrophage M2-like polarization and reveal potential new therapeutic targets for breast cancer treatment.

Unique Metabolic Adaptations Dictate Distal Organ-Specific Metastatic Colonization

Metastases arising from tumors have the proclivity to colonize specific organs, suggesting that they must rewire their biology to meet the demands of the organ colonized, thus altering their primary properties. Each metastatic site presents distinct metabolic challenges to a colonizing cancer cell, ranging from fuel and oxygen availability to oxidative stress. Here, we discuss the organ-specific metabolic adaptations that cancer cells must undergo, which provide the ability to overcome the unique barriers to colonization in foreign tissues and establish the metastatic tissue tropism phenotype.

Feeling Stress: The Mechanics of Cancer Progression and Aggression

The tumor microenvironment is a dynamic landscape in which the physical and mechanical properties evolve dramatically throughout cancer progression. These changes are driven by enhanced tumor cell contractility and expansion of the growing tumor mass, as well as through alterations to the material properties of the surrounding extracellular matrix (ECM). Consequently, tumor cells are exposed to a number of different mechanical inputs including cell–cell and cell-ECM tension, compression stress, interstitial fluid pressure and shear stress. Oncogenes engage signaling pathways that are activated in response to mechanical stress, thereby reworking the cell's intrinsic response to exogenous mechanical stimuli, enhancing intracellular tension via elevated actomyosin contraction, and influencing ECM stiffness and tissue morphology. In addition to altering their intracellular tension and remodeling the microenvironment, cells actively respond to these mechanical perturbations phenotypically through modification of gene expression. Herein, we present a description of the physical changes that promote tumor progression and aggression, discuss their interrelationship and highlight emerging therapeutic strategies to alleviate the mechanical stresses driving cancer to malignancy.

Alterations of tumor microenvironment by carbon monoxide impedes lung cancer growth

We hypothesized that tumor-associated macrophages (TAMs) are controlled by the diffusible gas carbon monoxide (CO). We demonstrate that induction of apoptosis in lung tumors treated with low doses of CO is associated with increased CD86 expression and activation of mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinases (Erk) 1/2 pathway in tumor microenvironment. Presence of CD86-positive cells was required for the anti-tumoral effects of CO in established A549 xenografts. We show that the effects of CO on tumor stroma and reprogramming of macrophages towards the anti-tumoral phenotype is mediated by reactive oxygen species (ROS)-dependent activation of MAPK/Erk1/2-c-myc pathway as well as Notch 1-dependent negative feedback on the metabolic enzyme heme oxygenase-1 (HO-1). We find a similar negative correlation between HO-1 and active MAPK-Erk1/2 levels in human lung cancer specimens.

In summary, we describe novel non-cell autonomous mechanisms by which the diffusible gas CO dictates changes in the tumor microenvironment through the modulation of macrophages.

A vascular disrupting agent overcomes tumor multidrug resistance by skewing macrophage polarity toward the M1 phenotype

Multidrug resistance (MDR) mediated by ATP-binding cassette (ABC) transporters is the major obstacle for chemotherapeutic success. Although attempts have been made to circumvent ABC transporter-mediated MDR in past decades, there is still no effective agent in clinic. Here, we identified a vascular disrupting agent, Z-GP-DAVLBH, that significantly inhibited the growth of multidrug-resistant human hepatoma HepG2/ADM and human breast cancer MCF-7/ADR tumor xenografts, although these cells were insensitive to Z-GP-DAVLBH in vitro. Z-GP-DAVLBH increased the secretion of granulocyte-macrophage colony-stimulating factor in tumor tissues and serum of tumor-bearing mice to skew tumor-associated macrophages from the pro-tumor M2 phenotype to the antitumor M1 phenotype, thereby contributing to the induction of HepG2/ADM and MCF-7/ADR cell apoptosis. Our findings shed new light on the underlying mechanisms of VDAs in the treatment of drug-resistant tumors and provide strong evidence that Z-GP-DAVLBH should be a promising agent for overcoming MDR.

Abundant tumor promoting stromal cells in lung adenocarcinoma with hypoxic regions

OBJECTIVES

Carbonic anhydrase IX (CAIX) is a marker of hypoxia and its expression by cancer associated fibroblasts (CAFs) was reportedly associated with the poor prognosis of lung adenocarcinoma. This study aimed to characterize the hypoxic microenvironment containing CAIX (+) CAFs.

MATERIALS AND METHODS

First, we evaluated the clinicopathological significance of CAIX expression by CAFs in 3cm and above lung adenocarcinoma (n=188). We then compared the expressions of E-cadherin, ezrin, ALDH-1, CD44, EGFR, HSF-1, Glut-1, and PD-L1 in cancer cells, as well as those of CD204 and podoplanin in stromal cells between CAIX (+) CAFs and CAIX (-) CAFs cases (n=25, each).

RESULTS

In total, 48 patients had CAIX (+) CAFs (26%). Multivariate analysis revealed that CAIX expression by CAFs could serve as an independent unfavorable prognostic factor for recurrence-free survival (p<0.05). The staining score of hypoxia marker Glut-1 in cancer cells was significantly higher in cases with CAIX (+) CAFs than in those with CAIX (-) CAFs (median: 20 vs. 0, p<0.01). In addition, the numbers of CD204 (+) tumor-associated macrophages (TAMs) and podoplanin (+) CAFs were significantly higher in the CAIX (+) CAFs group than in the CAIX (-) CAFs group (TAMs: 31.5 vs. 17.0: p<0.01, CAFs: 20 vs. 0: p<0.05). The staining score of the other markers did not differ between the groups.

CONCLUSION

Our results indicate that the presence of abundant tumor promoting stromal cells, CD204 (+) TAMs, and podoplanin (+) CAFs is characteristic of the tumor microenvironment containing CAIX (+) CAFs, which contributes to an increase in aggressive behavior in lung adenocarcinoma with hypoxic regions.

Angiopoietin-like protein 2 facilitates non-small cell lung cancer progression by promoting the polarization of M2 tumor-associated macrophages

The functional phenotypes (M1 and M2) of tumor-associated macrophages (TAMs) are influenced by the tumor microenvironment (TME) and contribute greatly to the development of non-small cell lung cancer (NSCLC). However, the molecular mechanisms for TAM polarization remain unclear. Angiopoietin-like protein 2 (Angptl2) is involved in tumor progression. In this study, Angptl2 expression was aberrantly increased in NSCLC cells and positively correlated with TAM infiltration, tumor size and poor patient survival. Moreover, in vitro tumor cell-macrophage co-culture and recombinant protein stimulation revealed that Angptl2 fostered the M2 polarization of TAMs through the p65 nuclear factor-kappa B (NF-ĸB) pathway. In addition, Angptl2-promoted TAM enhanced proliferation, invasion, and migration of NSCLC cells and the tube formation of human umbilical vein endothelial cells (HUVECs). In vivo, TAM depletion inhibited the tumor growth induced by Angptl2. Here, for the first time, we determined that Angptl2 promoted the M2 polarization of TAMs and enhanced NSCLC progression. Interfering with Angptl2 might be an effective strategy for reprogramming TAM polarization in NSCLC, providing a promising therapy for NSCLC treatment.

Adipocytes and Macrophages Interplay in the Orchestration of Tumor Microenvironment: New Implications in Cancer Progression

Inflammation has been known as one of the main keys to the establishment and progression of cancers. Chronic low-grade inflammation is also a strategic condition that underlies the causes and development of metabolic syndrome and obesity. Moreover, obesity has been largely related to poor prognosis of tumors by modulating tumor microenvironment with secretion of several inflammatory mediators by tumor-associated adipocytes (TAAs), which can modulate and recruit tumor-associated macrophages. Thus, the understanding of cellular and molecular mechanisms that underlay and link inflammation, obesity, and cancer is crucial to identify potential targets that interfere with this important route. Knowledge about the exact role of each component of the tumor microenvironment is not yet fully understood, but the new insights in literature highlight the essential role of adipocytes and macrophages interplay as key factor to determine the fate of cancer progression. In this review article, we focus on the functions of adipocytes and macrophages orchestrating cellular and molecular mechanisms that lead to inflammatory modulation in tumor microenvironment, which will be crucial to cancer establishment. We also emphasized the mechanisms by which the tumor promotes itself by recruiting and polarizing macrophages, discussing the role of adipocytes in this process. In addition, we discuss here the newest possible anticancer therapeutic treatments aiming to retard the development of the tumor based on what is known about cancer, adipocyte, and macrophage polarization.

Regulation of Human Macrophage M1-M2 Polarization Balance by Hypoxia and the Triggering Receptor Expressed on Myeloid Cells-1

Macrophages (Mf) are a heterogeneous population of tissue-resident professional phagocytes and a major component of the leukocyte infiltrate at sites of inflammation, infection, and tumor growth. They can undergo diverse forms of activation in response to environmental factors, polarizing into specialized functional subsets. A common hallmark of the pathologic environment is represented by hypoxia. The impact of hypoxia on human Mf polarization has not been fully established. The objective of this study was to elucidate the effects of a hypoxic environment reflecting that occurring in vivo in diseased tissues on the ability of human Mf to polarize into classically activated (proinflammatory M1) and alternatively activated (anti-inflammatory M2) subsets. We present data showing that hypoxia hinders Mf polarization toward the M1 phenotype by decreasing the expression of T cell costimulatory molecules and chemokine homing receptors and the production of proinflammatory, Th1-priming cytokines typical of classical activation, while promoting their acquisition of phenotypic and secretory features of alternative activation. Furthermore, we identify the triggering receptor expressed on myeloid cells (TREM)-1, a member of the Ig-like immunoregulatory receptor family, as a hypoxia-inducible gene in Mf and demonstrate that its engagement by an agonist Ab reverses the M2-polarizing effect of hypoxia imparting a M1-skewed phenotype to Mf. Finally, we provide evidence that Mf infiltrating the inflamed hypoxic joints of children affected by oligoarticular juvenile idiopatic arthritis express high surface levels of TREM-1 associated with predominant M1 polarization and suggest the potential of this molecule in driving M1 proinflammatory reprogramming in the hypoxic synovial environment.

Exosomes derived from hypoxic epithelial ovarian cancer deliver microRNA-940 to induce macrophage M2 polarization

Hypoxia is a common feature of solid tumors. It is closely related to tumor progression. Exosomal microRNAs derived from cancers are considered to be mediators between cancer cells and the tumor microenvironment. In addition, the number of tumor-associated macrophages (TAMs) in the tumor microenvironment has also been demonstrated to correlate with tumor development. However, the relationship between tumor-secreted exosomes and TAM polarization under hypoxic conditions during tumor progression is not clear. Herein, we demonstrated that hypoxia induces the high expression of microRNA-940 (miR‑940) in exosomes derived from epithelial ovarian cancer (EOC). We also found that miR‑940 is highly expressed in exosomes isolated from ascites of EOC patients. Moreover, the overexpression of miR‑940 in macrophages delivered by exosomes stimulated M2 phenotype polarization, while the M2 subtype macrophages promoted EOC proliferation and migration. These results highlight the function of hypoxia in enhancing the high level of expression of miR‑940 in tumor exosomes taken up by macrophages. We also showed that the tumor-promoting function of miR‑940 is mediated by TAM polarization in EOC. These findings show that tumor-derived exosomal miR‑940 induced by hypoxia plays an important role in stimulating TAM polarization in the progression of EOC.

All-Trans Retinoic Acid Prevents Osteosarcoma Metastasis by Inhibiting M2 Polarization of Tumor-Associated Macrophages

M2-polarized tumor-associated macrophages (TAM) play a critical role in cancer invasion and metastasis. Here, we report that M2 macrophages enhanced metastasis of K7M2 WT osteosarcoma cells to the lungs in mice, thus establishing M2 TAMs as a therapeutic target for blocking osteosarcoma metastasis. We found that all-trans retinoic acid (ATRA) inhibited osteosarcoma metastasis via inhibiting the M2 polarization of TAMs. ATRA suppressed IL13- or IL4-induced M2-type macrophages, and then inhibited migration of osteosarcoma cells as promoted by M2-type macrophages in vitro ATRA reduced the number of pulmonary metastatic nodes of osteosarcoma and decreased expression of M2-type macrophages in metastatic nodes both in intravenous injection and orthotopic transplantation models. ATRA's effect was independent of conventional STAT3/6 or C/EBPβ signaling, which regulate M2-like polarization of macrophages. Quantitative genomic and functional analyses revealed that MMP12, a macrophage-secreted elastase, was elevated in IL13-skewed TAM polarization, whereas ATRA treatment downregulated IL13-induced secretion of MMP12. This downregulation correlates with the antimetastasis effect of ATRA. Our results show the role of TAM polarization in osteosarcoma metastasis, identify a therapeutic opportunity for antimetastasis treatment, and indicate ATRA treatment as an approach for preventing osteosarcoma metastasis via M2-type polarization intervention. Cancer Immunol Res; 5(7); 547-59. ©2017 AACR.

The Promise of Targeting Macrophages in Cancer Therapy

Cancer therapy has developed around the concept of killing, or stopping the growth of, the cancer cells. Molecularly targeted therapy is the modern expression of this paradigm. Increasingly, however, the realization that the cancer has co-opted the normal cells of the stroma for its own survival has led to the concept that the tumor microenvironment (TME) could be targeted for effective therapy. In this review, we outline the importance of tumor-associated macrophages (TAM), a major component of the TME, in the response of tumors to cancer therapy. We discuss the normal role of macrophages in wound healing, the major phenotypes of TAMs, and their role in blunting the efficacy of cancer treatment by radiation and anticancer drugs, both by promoting tumor angiogenesis and by suppressing antitumor immunity. Finally, we review the many preclinical studies that have shown that the response of tumors to irradiation and anticancer drugs can be improved, sometimes markedly so, by depleting TAMs from tumors or by suppressing their polarization from an M1 to an M2 phenotype. The data clearly support the validity of clinical testing of combining targeting TAMs with conventional therapy. Clin Cancer Res; 23(13); 3241-50. ©2017 AACR.

Tumor Hypoxia Regulates Forkhead Box C1 to Promote Lung Cancer Progression

Forkhead box C1 (FOXC1) is a member of the forkhead family of transcription factors that are characterized by a DNA-binding forkhead domain. Increasing evidence indicates that FOXC1 is involved in tumor progression. However, the role of tumor hypoxia in FOXC1 regulation and its impact on lung cancer progression are unclear. Here, we report that FOXC1 was upregulated in hypoxic areas of lung cancer tissues from rodents or humans. Hypoxic stresses significantly induced FOXC1 expression. Moreover, hypoxia activated FOXC1 transcription via direct binding of hypoxia-inducible factor-1α (HIF-1α) to the hypoxia-responsive element (HRE) in the FOXC1 promoter. FOXC1 gain-of-function in lung cancer cells promoted cell proliferation, migration, invasion, angiogenesis, and epithelial-mesenchymal transition in vitro. However, a knockdown of FOXC1 in lung cancer cells inhibited these effects. Notably, knockdown of tumor hypoxia-induced FOXC1 expression via HIF-1-mediated FOXC1 shRNAs in lung cancer xenograft models suppressed tumor growth and angiogenesis. Finally, systemic delivery of FOXC1 siRNA encapsulated in lipid nanoparticles inhibited tumor growth and increased survival time in lung cancer-bearing mice. Taken together, these data indicate that FOXC1 is a novel hypoxia-induced transcription factor and plays a critical role in tumor microenvironment-promoted lung cancer progression. Systemic FOXC1 blockade therapy may be an effective therapeutic strategy for lung cancer.

PEDF mediates pathological neovascularization by regulating macrophage recruitment and polarization in the mouse model of oxygen-induced retinopathy

Macrophages have been demonstrated to play a proangiogenic role in retinal pathological vascular growth. Pigment epithelium-derived factor (PEDF) works as a powerful endogenous angiogenesis inhibitor, but its role in macrophage recruitment and polarization is largely unknown. To explore the underlying mechanisms, we first evaluated macrophage polarization in the retinas of the oxygen-induced retinopathy (OIR) mouse model. Compared to that in normal controls, M1- and M2-like macrophages were all abundantly increased in the retinas of OIR mice. In addition, both M1 and M2 subtypes significantly promoted neovascularization in vitro and in vivo. In addition, we found that PEDF inhibited retinal neovascularization by dampening macrophage recruitment and polarization. Furthermore, PEDF inhibited macrophage polarization through adipose triglyceride lipase (ATGL) by regulating the activation of MAPKs and the Notch1 pathway, as we found that the phosphorylation of MAPKs, including p38MAPK, JNK and ERK, as well as the accumulation of Notch1 were essential for hypoxia-induced macrophage polarization, while PEDF significantly dampened M1 subtype-related iNOS and M2 subtype-related Arg-1 expression by inhibiting hypoxia-induced activation of Notch1 and MAPKs through ATGL. These findings reveal a protective role of PEDF against retinal neovascularization by regulating macrophage recruitment and polarization.

The accumulation of macrophages attenuates the effect of recombinant human endostatin on lung cancer

Background

Although anti-angiogenic therapy is widely applied clinically, its efficacy has been less than expected. Screening for regulatory factors and sensitive indicators to define the effectiveness of these drugs is required. Through a retrospective study of clinical data, we found that patients with a higher peripheral monocyte-to-lymphocyte ratio (MLR) obtained less benefit from recombinant human endostatin (rhES, Endostar^®), an anti-angiogenic drug, in lung cancer. Because MLR is positively correlated with macrophage count in tumors, this result suggests that macrophages may influence the effectiveness of rhES therapy in lung cancer.

Methods

Clinical data from 72 lung cancer patients treated with rhES were collected. Animal study, flow cytometry, immunofluorescence, enzyme-linked immunosorbent assay, Western blot analysis, and transwell migration assays were carried on Lewis lung carcinoma (LLC) cells, bone marrow-derived macrophages, macrophage cell line RAW264.7, and ANA-1 cells.

Results

Clinical data showed that compared with the baseline MLR before rhES treatment, patients with progressive disease had higher MLRs than those of patients with partial response. Experimental results showed that more macrophages were recruited in the LLC tumors after rhES treatment and the majority of them displayed an M2-like phenotype. rhES aggravated hypoxia and the inflammatory response in the tumor microenvironment. Hypoxia promoted the expression of CCL2 by endothelial and fibroblast cells, which could induce macrophages recruitment, and increased levels of inflammatory cytokines (interleukin-4 [IL-4], IL-6, and IL-10) skewed macrophage polarization toward the M2-like phenotype. Hypoxia or inflammation cytokine-treated macrophages enhanced the progression of LLC in vitro and in vivo.

Conclusion

We found rhES could aggravate hypoxia and the inflammatory response in the tumor microenvironment. These changes were favorable for macrophage accumulation, and skewed their polarization toward the M2-like phenotype which could help LLC to escape from the anti-angiogenic therapy. Thus, these data indicate the accumulation of macrophages in the tumor microenvironment may adversely affect the efficacy of rhES on lung cancer.

Sphingosine-1 Phosphate: A New Modulator of Immune Plasticity in the Tumor Microenvironment

In the last 15 years, increasing evidences demonstrate a strong link between sphingosine-1-phosphate (S1P) and both normal physiology and progression of different diseases, including cancer and inflammation. Indeed, numerous studies show that tissue levels of this sphingolipid metabolite are augmented in many cancers, affecting survival, proliferation, angiogenesis, and metastatic spread. Recent insights into the possible role of S1P as a therapeutic target has attracted enormous attention and opened new opportunities in this evolving field. In this review, we will focus on the role of S1P in cancer, with particular emphasis in new developments that highlight the many functions of this sphingolipid in the tumor microenvironment. We will discuss how S1P modulates phenotypic plasticity of macrophages and mast cells, tumor-induced immune evasion, differentiation and survival of immune cells in the tumor milieu, interaction between cancer and stromal cells, and hypoxic response.

miR-181a Induces Macrophage Polarized to M2 Phenotype and Promotes M2 Macrophage-mediated Tumor Cell Metastasis by Targeting KLF6 and C/EBPα

Macrophages can acquire a variety of polarization status and functions: classically activated macrophages (M1 macrophages); alternatively activated macrophages (M2 macrophages). However, the molecular basis of the process is still unclear. Here, this study addresses that microRNA-181a (miR-181a) is a key molecule controlling macrophage polarization. We found that miR-181a is overexpressed in M2 macrophages than in M1 macrophages. miR-181a expression was decreased when M2 phenotype converted to M1, whereas it increased when M1 phenotype converted to M2. Overexpression of miR-181a in M1 macrophages diminished M1 phenotype expression while promoting polarization to the M2 phenotype. In contrast, knockdown of miR-181a in M2 macrophages promoted M1 polarization and diminished M2 phenotype expression. Mechanistically, Bioinformatic analysis revealed that Kruppel-like factor 6 (KLF6) and CCAAT/enhancer binding protein-α (C/EBPα) is a potential target of miR-181a and luciferase assay confirmed that KLF6 and C/EBPα translation is suppressed by miR-181a through interaction with the 3′UTR of KLF6 and C/EBPα mRNA. Further analysis showed that induction of miR-181a suppressed KLF6 and C/EBPα protein expression. Importantly, miR-181a also diminishes M2 macrophages-mediated migration and invasion capacity of tumor cells. Collectively, our results suggest that miR-181a plays a significant role in regulating macrophage polarization through directly target KLF6 and C/EBPα.

The Roles of Mesenchymal Stromal/Stem Cells in Tumor Microenvironment Associated with Inflammation

State of tumor microenvironment (TME) is closely linked to regulation of tumor growth and progression affecting the final outcome, refractoriness, and relapse of disease. Interactions of tumor, immune, and mesenchymal stromal/stem cells (MSCs) have been recognized as crucial for understanding tumorigenesis. Due to their outstanding features, stem cell-like properties, capacity to regulate immune response, and dynamic functional phenotype dependent on microenvironmental stimuli, MSCs have been perceived as important players in TME. Signals provided by tumor-associated chronic inflammation educate MSCs to alter their phenotype and immunomodulatory potential in favor of tumor-biased state of MSCs. Adjustment of phenotype to TME and acquisition of tumor-promoting ability by MSCs help tumor cells in maintenance of permissive TME and suppression of antitumor immune response. Potential utilization of MSCs in treatment of tumor is based on their inherent ability to home tumor tissue that makes them suitable delivery vehicles for immune-stimulating factors and vectors for targeted antitumor therapy. Here, we review data regarding intrusive effects of inflammatory TME on MSCs capacity to affect tumor development through modification of their phenotype and interactions with immune system.

Brain metastasis in lung cancer: Building a molecular and systems-level understanding to improve outcomes

Lung cancer is a clinically difficult disease with rising disease burden around the world. Unfortunately, most lung cancers present at a clinically advanced stage. Of these cancers, many also present with brain metastasis which complicates the clinical picture. This review summarizes current knowledge on the molecular basis of lung cancer brain metastases. We start from the clinical perspective, aiming to provide a clinical context for a significant problem that requires much deeper scientific investigation. We review new research governing the metastatic process, including tumor cell signaling, establishment of a receptive tumor niches in the brain and evaluate potential new therapeutic options that take advantage of these new scientific advances. Lung cancer remains the largest single cause of cancer mortality in the United States (Siegel et al., 2015). This continues to be the clinical picture despite significant advances in therapy, including the advent of targeted molecular therapies and newly adopted immunotherapies for certain subtypes of lung cancer. In the vast majority of cases, lung cancer presents as advanced disease; in many instances, this advanced disease state is intimately associated with micro and macrometastatic disease (Goldberg et al., 2015). For both non-small cell lung cancer and small cell lung cancer patients, the predominant metastatic site is the brain, with up to 68% of patients with mediastinal lymph node metastasis eventually demonstrating brain metastasis (Wang et al., 2009).The frequency (incidence) of brain metastasis is highest in lung cancers, relative to other common epithelial malignancies (Schouten et al., 2002). Other studies have attempted to predict the risk of brain metastasis in the setting of previously non-metastatic disease. One of the largest studies to do this, analyzing historical data from 1973 to 2011 using the SEER database revealed a 9% risk of patients with previously non-metastatic NSCLC developing brain metastasis over the course of their disease, while 18% of small cell lung cancer patients without previous metastasis went on to develop brain metastasis as their disease progressed (Goncalves et al., 2016).The reasons underlying this predilection for the central nervous system, as well as the recent increase in the frequency of brain metastasis identified in patients remain important questions for both clinicians and basic scientists. More than ever, the question of how brain metastasis develop and how they can be treated and managed requires the involvement of interdisciplinary teams-and more importantly-scientists who are capable of thinking like clinicians and clinicians who are capable of thinking like scientists. This review aims to present a translational perspective on brain metastasis. We will investigate the scope of the problem of brain metastasis and the current management of the metastatic disease process in lung cancer. From this clinical starting point, we will investigate the literature surrounding the molecular underpinnings of lung tumor metastasis and seek to understand the process from a biological perspective to generate new hypotheses.

Cycling hypoxia: A key feature of the tumor microenvironment

A compelling body of evidence indicates that most human solid tumors contain hypoxic areas. Hypoxia is the consequence not only of the chaotic proliferation of cancer cells that places them at distance from the nearest capillary but also of the abnormal structure of the new vasculature network resulting in transient blood flow. Hence two types of hypoxia are observed in tumors: chronic and cycling (intermittent) hypoxia. Most of the current work aims at understanding the role of chronic hypoxia in tumor growth, response to treatment and metastasis. Only recently, cycling hypoxia, with spatial and temporal fluctuations in oxygen levels, has emerged as another key feature of the tumor environment that triggers different responses in comparison to chronic hypoxia. Either type of hypoxia is associated with distinct effects not only in cancer cells but also in stromal cells. In particular, cycling hypoxia has been demonstrated to favor, to a higher extent than chronic hypoxia, angiogenesis, resistance to anti-cancer treatments, intratumoral inflammation and tumor metastasis. These review details these effects as well as the signaling pathway it triggers to switch on specific transcriptomic programs. Understanding the signaling pathways through which cycling hypoxia induces these processes that support the development of an aggressive cancer could convey to the emergence of promising new cancer treatments.

Direct effects of airborne PM2.5 exposure on macrophage polarizations

BACKGROUND

Exposure of atmospheric particulate matter with an aerodynamic diameter less than 2.5μm (PM2.5) is epidemiologically associated with illnesses. Potential effects of air pollutants on innate immunity have raised concerns. As the first defense line, macrophages are able to induce inflammatory response. However, whether PM2.5 exposure affects macrophage polarizations remains unclear.

METHODS

We used freshly isolated macrophages as a model system to demonstrate effects of PM2.5 on macrophage polarizations. The expressions of cytokines and key molecular markers were detected by real-time PCR, and flow cytometry. The specific inhibitors and gene deletion technologies were used to address the molecular mechanisms.

RESULTS

PM2.5 increased the expression of pro-inflammatory cytokines granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-6 (IL-6), interleukin-1β (IL-1β), tumor necrosis factor alpha (TNFα). PM2.5 also enhanced the lipopolysaccharide (LPS)-induced M1 polarization even though there was no evidence in the change of cell viability. However, PM2.5 significantly decreased the number of mitochondria in a dose dependent manner. Pre-treatment with NAC, a scavenger of reactive oxygen species (ROS), prevented the increase of ROS and rescued the PM2.5-impacted M1 but not M2 response. However, mTOR deletion partially rescued the effects of PM2.5 to reduce M2 polarization.

CONCLUSIONS

PM2.5 exposure significantly enhanced inflammatory M1 polarization through ROS pathway, whereas PM2.5 exposure inhibited anti-inflammatory M2 polarization through mTOR-dependent pathway.

GENERAL SIGNIFICANCE

The present studies suggested that short-term exposure of PM2.5 acts on the balance of inflammatory M1 and anti-inflammatory M2 macrophage polarizations, which may be involved in air pollution-induced immune disorders and diseases. This article is part of a Special Issue entitled Air Pollution, edited by Wenjun Ding, Andrew J. Ghio and Weidong Wu.

TOPK is highly expressed in circulating tumor cells, enabling metastasis of prostate cancer

Circulating tumor cells (CTCs) are important for metastasis in prostate cancer. T-LAK cell-originated protein kinase (TOPK) is highly expressed in cancer cells. Herein, we established a xenograft animal model, isolated and cultured the CTCs, and found CTCs have significantly greater migratory capacity than parental cells. TOPK is more highly expressed in the CTCs than in parental cells and is also highly expressed in the metastatic nodules caused by CTCs in mice. Knocking down TOPK decreased the migration of CTCs both in vitro and in vivo. TOPK was modulated by the PI3K/PTEN and ERK pathways during the metastasis of prostate cancer. High levels of TOPK in the tumors of patients were correlated with advanced stages of prostate cancer, especially for high-risk patients of Gleason score≥8, PSA>20ng/ml. In summary, TOPK was speculated to be one of a potential marker and therapeutic target in advanced prostate cancer.

Efficacy and Interaction of Antioxidant Supplements as Adjuvant Therapy in Cancer Treatment: A Systematic Review

Oxidative stress is a key component in carcinogenesis. Although radiation produces reactive oxygen species, some anticancer agents such as alkylating agents, platinum and antitumor antibiotics exert cytotoxicity by generating free radicals. Nonenzymatic exogenous antioxidants such as vitamins, minerals, and polyphenols can quench ROS activity. However, whether antioxidants alter antitumor effects during radiotherapy and some types of chemotherapy remains unclear. In the present study, we reviewed antioxidants as an adjuvant therapy for cancer patients during chemotherapy or radiotherapy. Electronic literature searches were performed to select all randomized controlled clinical trials (RCTs) in which antioxidants were administered to cancer patients along with chemotherapy or radiotherapy. Articles or abstracts written in English were included. In total, 399 reports received primary screening. Duplicated articles and those meeting the exclusion criteria (not RCT, not human, and no oral administration) were excluded. Finally, 49 reports matching the inclusion criteria were included. It was difficult to determine whether antioxidants affect treatment outcomes or whether antioxidants ameliorate adverse effects induced by chemotherapy and radiotherapy. It is desirable to use an evidence-based method to select supplements best suited to cancer patients. Although there are many opinions about risks or benefits of antioxidant supplementation, we could mostly conclude that the harm caused by antioxidant supplementation remains unclear for patients during cancer therapy, except for smokers undergoing radiotherapy.

Interleukin-17A neutralization alleviated ocular neovascularization by promoting M2 and mitigating M1 macrophage polarization

Neovascularization (NV), as a cardinal complication of several ocular diseases, has been intensively studied, and research has shown its close association with inflammation and immune cells. In the present study, the role of interleukin-17A (IL-17A) in angiogenesis in the process of ocular NV both in vivo and in vitro was investigated. Also, a paracrine role of IL-17A was demonstrated in the crosstalk between endothelial cells and macrophages in angiogenesis. In the retinas of mice with retinopathy of prematurity, the IL-17A expression increased significantly at postnatal day 15 (P15) and P18 during retinal NV. Mice given IL-17A neutralizing antibody (NAb) developed significantly reduced choroidal NV and retinal NV. Studies on vascular endothelial growth factor (VEGF) over-expressing mice suggested that IL-17A modulated NV through the VEGF pathway. Furthermore, IL-17A deficiency shifted macrophage polarization toward an M2 phenotype during retinal NV with significantly reduced M1 cytokine expression compared with wild-type controls. In vitro assays revealed that IL-17A treated macrophage supernatant gave rise to elevated human umbilical vascular endothelial cell proliferation, tube formation and VEGF receptor 1 and receptor 2 expression. Therefore, IL-17A could potentially serve as a novel target for treating ocular NV diseases. The limitation of this study involved the potential mechanisms, such as which transcription accounted for macrophage polarization and how the subsequent cytokines were modulated when macrophages were polarized. Further studies need to be undertaken to definitively determine the extent to which IL-17A neutralizing anti-angiogenic activity depends on macrophage modulation compared with anti-VEGF treatment.

CD90(+) stromal cells are the major source of IL-6, which supports cancer stem-like cells and inflammation in colorectal cancer

IL-6 is a pleiotropic cytokine increased in CRC and known to directly promote tumor growth. Colonic myofibroblasts/fibroblasts (CMFs or stromal cells) are CD90(+) innate immune cells representing up to 30% of normal colonic mucosal lamina propria cells. They are expanded in CRC tumor stroma, where they also known as a cancer associated fibroblasts (CAFs). Cells of mesenchymal origin, such as normal myofibroblasts/fibroblasts, are known to secrete IL-6; however, their contribution to the increase in IL-6 in CRC and to tumor-promoting inflammation is not well defined. Using in situ, ex vivo and coculture analyses we have demonstrated that the number of IL-6 producing CMFs is increased in CRC (C-CMFs) and they represent the major source of IL-6 in T2-T3 CRC tumors. Activity/expression of stem cell markers-aldehyde dehydrogenase and LGR5- was significantly up-regulated in colon cancer cells (SW480, Caco-2 or HT29) cultured in the presence of conditioned medium from tumor isolated C-CMFs in an IL-6 dependent manner. C-CMF and its derived condition medium, but not normal CMF isolated from syngeneic normal colons, induced differentiation of tumor promoting inflammatory T helper 17 cells (Th17) cell responses in an IL-6 dependent manner. Our study suggests that CD90(+) fibroblasts/myofibroblasts may be the major source of IL-6 in T2-T3 CRC tumors, which supports the stemness of tumor cells and induces an immune adaptive inflammatory response (a.k.a. Th17) favoring tumor growth. Taken together our data supports the notion that IL-6 producing CAFs (a.k.a. C-CMFs) may provide a useful target for treating or preventing CRCs.

Cell Death Conversion under Hypoxic Condition in Tumor Development and Therapy

Hypoxia, which is common during tumor progression, plays important roles in tumor biology. Failure in cell death in response to hypoxia contributes to progression and metastasis of tumors. On the one hand, the metabolic and oxidative stress following hypoxia could lead to cell death by triggering signal cascades, like LKB1/AMPK, PI3K/AKT/mTOR, and altering the levels of effective components, such as the Bcl-2 family, Atg and p62. On the other hand, hypoxia-induced autophagy can serve as a mechanism to turn over nutrients, so as to mitigate the adverse condition and then avoid cell death potentially. Due to the effective role of hypoxia, this review focuses on the crosstalk in cell death under hypoxia in tumor progression. Additionally, the illumination of cell death in hypoxia could shed light on the clinical applications of cell death targeted therapy.

Sulforaphane inhibits hypoxia-induced HIF-1α and VEGF expression and migration of human colon cancer cells

The effects of sulforaphane (a natural product commonly found in broccoli) was investigated on hypoxia inducible factor-1α (HIF-1α) expression in HCT116 human colon cancer cells and AGS human gastric cancer cells. We found that hypoxia-induced HIF-1α protein expression in HCT116 and AGS cells, while treatment with sulforaphane markedly and concentration-dependently inhibited HIF-1α expression in both cell lines. Treatment with sulforaphane inhibited hypoxia-induced vascular endothelial growth factor (VEGF) expression in HCT116 cells. Treatment with sulforaphane modulated the effect of hypoxia on HIF-1α stability. However, degradation of HIF-1α by sulforaphane was not mediated through the 26S proteasome pathway. We also found that the inhibition of HIF-1α by sulforaphane was not mediated through AKT and extracellular signal-regulated kinase phosphorylation under hypoxic conditions. Finally, hypoxia-induced HCT116 cell migration was inhibited by sulforaphane. These data suggest that sulforaphane may inhibit human colon cancer progression and cancer cell angiogenesis by inhibiting HIF-1α and VEGF expression. Taken together, these results indicate that sulforaphane is a new and potent chemopreventive drug candidate for treating patients with human colon cancer.

miR-130a regulates macrophage polarization and is associated with non-small cell lung cancer

Lung cancer is the most common cancer as well as the leading cause of cancer-related mortalities worldwide. Macrophages are the most abundant immune cells in primary and metastatic tumors, and contribute to tumor initiation, progression and metastasis. Macrophages have been shown to demonstrate a high level of plasticity, with the ability to undergo dynamic transition between M1 and M2 polarized phenotypes. In the present study, we investigated a pivotal role of miR-130a in macrophage polarization and whether it was associated with poor prognosis in non-small cell lung cancer (NSCLC), using RT-qPCR and western blot analyses. The in vitro experiments showed that miRNA-130a was expressed at a higher level in M1 compared to M2 macrophages. The enforced expression of miR-130a in macrophages resulted in a significantly increased production of proinflammatory cytokines, whereas deletion of miR-130a impaired the M2‑associated gene expression and led to an M1-biased response. Mechanistically, the bioinformatics analysis revealed that proliferator-activated receptor γ (PPARγ) is a potential target of miR-130a. Additionally, the luciferase assay confirmed that PPARγ translation was suppressed by miR-130a through the interaction with the 3'UTR of PPARγ mRNA. A subsequent analysis revaled that the induction of miR-130a suppressed PPARγ protein expression. In NSCLC patients, the results showed that miR-130a downregulation exhibited clinical relevance as it was correlated with poor prognosis and increased tumor stage and metastasis. In addition, miR‑130a was inversely correlated with the macrophage marker, CD163, and target gene, PPARγ. Taken together, the results established miR-130a as a molecular switch during macrophage development and as a potential target for the treatment of NSCLC.

Ultra‑performance liquid chromatography coupled with quadrupole time‑of‑flight mass spectrometry‑based metabolic profiling of human serum prior to and following radical resection of colorectal carcinoma

Nearly one quarter of patients with colorectal carcinoma (CRC) were diagnosed at an advanced stage. Under these circumstances, radical resection of the tumor is the best strategy to enhance the five-year survival rate. However, up to 50% of post-operative patients experience cancer recurrence within the first few years. Therefore, post‑operative surveillance is important. However, currently performed post‑operative monitoring relies on relatively dated methods with insufficient sensitivity and specificity. The present study applied an advanced technology of ultra‑performance liquid chromatography coupled with quadrupole time‑of‑flight mass spectrometry in order to examine changes in metabolite patterns in serum with the aim of identifying reliable biomarkers in patients with CRC at various time-points. Serum samples were collected from and 20 CRC patients prior to radical resection (group 1) and one month following radical resection (group 2) as well as from 20 healthy volunteers (group 3). Multivariate pattern recognition was used to identify potential biomarkers of CRC. Compared with healthy volunteers, three groups of biomarkers were identified in patients with CRC (P<0.05), namely phosphatidylcholines (PCs), lysophosphatidylcholines (LPCs) and diacylglycerols (DAGs). However, no statistical difference in the levels of these biomarkers between pre‑operative and post‑operative CRC patients was identified (P>0.05). PCs and LPCs, which contain polyunsaturated fatty acids, were decreased, whereas LPCs and DAGs, which contain saturated fatty acids, were increased in CRC patients. The present study demonstrated that obvious metabolic disturbances occur during the development of CRC and provided a novel analytic method, which is likely to be used as a diagnostic tool for CRC and may help to improve the patients' prognosis.