Disruption of the Lcn2 gene in mice suppresses primary mammary tumor formation but does not decrease lung metastasis

Oncogenic and tumor-suppressive roles of Lipocalin 2 (LCN2) in tumor progression

Lipocalin-2 (LCN2) is a member of the lipocalin superfamily with multiple functions and can participate in the transport of a variety of small lipophilic ligands in vivo. LCN2 is significantly expressed in various tumors and plays an important role in regulating tumor cell proliferation, invasion, and metastasis. The specific actions of LCN2 in tumors may vary depending on the particular type of cancer involved. In this review, we provide an extensive overview of the transcriptional and post-transcriptional regulation of LCN2 in health and disease. Furthermore, we summarize the impact of LCN2 dysregulation in a broad range of tumors. Lastly, we examine the mechanisms of action of LCN2 during tumorigenesis, progression, and metastasis. Understanding the complex relationships between LCN2 and tumor development, progression, and metastasis is vital for advancing our knowledge of cancer biology, developing biomarkers for diagnosis and clinical decision-making, and creating therapeutic strategies to improve the management of patients with cancer.

LCN2: Versatile players in breast cancer

Lipocalin 2 (LCN2) is a secreted glycoprotein that is produced by immune cells, including neutrophils and macrophages. It serves various functions such as transporting hydrophobic ligands across the cellular membrane, regulating immune responses, keeping iron balance, and fostering epithelial cell differentiation. LCN2 plays a crucial role in several physiological processes. LCN2 expression is upregulated in a variety of human diseases and cancers. High levels of LCN2 are specifically linked to breast cancer (BC) cell proliferation, apoptosis, invasion, migration, angiogenesis, immune regulation, chemotherapy resistance, and prognosis. As a result, LCN2 has gained attention as a potential therapeutic target for BC. This article offered an in-depth review of the advancement of LCN2 in the context of BC occurrence and development.

Mimicking the breast metastatic microenvironment: characterization of a novel syngeneic model of HER2+ breast cancer

Preclinical murine models in which primary tumors spontaneously metastasize to distant organs are valuable tools to study metastatic progression and novel cancer treatment combinations. Here, we characterize a novel syngeneic murine breast tumor cell line, NT2.5-lung metastasis (-LM), that provides a model of spontaneously metastatic neu-expressing breast cancer with quicker onset of widespread metastases after orthotopic mammary implantation in immune-competent NeuN mice. Within one week of orthotopic implantation of NT2.5-LM in NeuN mice, distant metastases can be observed in the lungs. Within four weeks, metastases are also observed in the bones, spleen, colon, and liver. Metastases are rapidly growing, proliferative, and responsive to HER2-directed therapy. We demonstrate altered expression of markers of epithelial-to-mesenchymal transition (EMT) and enrichment in EMT-regulating pathways, suggestive of their enhanced metastatic potential. The new NT2.5-LM model provides more rapid and spontaneous development of widespread metastases. Besides investigating mechanisms of metastatic progression, this new model may be used for the rationalized development of novel therapeutic interventions and assessment of therapeutic responses targeting distant visceral metastases.

Lipocalin-2: A Nurturer of Tumor Progression and a Novel Candidate for Targeted Cancer Therapy

Within the tumor microenvironment (TME) exists a complex signaling network between cancer cells and stromal cells, which determines the fate of tumor progression. Hence, interfering with this signaling network forms the basis for cancer therapy. Yet, many types of cancer, in particular, solid tumors, are refractory to the currently used treatments, so there is an urgent need for novel molecular targets that could improve current anti-cancer therapeutic strategies. Lipocalin-2 (Lcn-2), a secreted siderophore-binding glycoprotein that regulates iron homeostasis, is highly upregulated in various cancer types. Due to its pleiotropic role in the crosstalk between cancer cells and stromal cells, favoring tumor progression, it could be considered as a novel biomarker for prognostic and therapeutic purposes. However, the exact signaling route by which Lcn-2 promotes tumorigenesis remains unknown, and Lcn-2-targeting moieties are largely uninvestigated. This review will (i) provide an overview on the role of Lcn-2 in orchestrating the TME at the level of iron homeostasis, macrophage polarization, extracellular matrix remodeling, and cell migration and survival, and (ii) discuss the potential of Lcn-2 as a promising novel drug target that should be pursued in future translational research.

Lipocalin-2 regulates the expression of interferon-stimulated genes and the susceptibility of prostate cancer cells to oncolytic virus infection

Lipocalin-2 (LCN2) performs pleiotropic and tumor context-dependent functions in cancers of diverse etiologies. In prostate cancer (PCa) cells, LCN2 regulates distinct phenotypic features, including cytoskeleton organization and expression of inflammation mediators. Oncolytic virotherapy uses oncolytic viruses (OVs) to kill cancer cells and induce anti-tumor immunity. A main source of specificity of OVs towards tumor cells stems from cancer-induced defects in interferon (IFN)-based cell autonomous immune responses. However, the molecular underpinnings of such defects in PCa cells are only partially understood. Moreover, LCN2 effects on IFN responses of PCa cells and their susceptibility to OVs are unknown. To examine these issues, we queried gene expression databases for genes coexpressed with LCN2, revealing co-expression of IFN-stimulated genes (ISGs) and LCN2. Analysis of human PCa cells revealed correlated expression of LCN2 and subsets of IFNs and ISGs. CRISPR/Cas9-mediated stable knockout of LCN2 in PC3 cells or transient overexpression of LCN2 in LNCaP cells revealed LCN2-mediated regulation of IFNE (and IFNL1) expression, activation of JAK/STAT pathway, and expression of selected ISGs. Accordingly, and dependent on a functional JAK/STAT pathway, LCN2 reduced the susceptibility of PCa cells to infection with the IFN-sensitive OV, EHDV-TAU. In PC3 cells, LCN2 knockout increased phosphorylation of eukaryotic initiation factor 2α (p-eIF2α). Inhibition of PKR-like ER kinase (PERK) in PC3-LCN2-KO cells reduced p-eIF2α while increasing constitutive IFNE expression, phosphorylation of STAT1, and ISG expression; and decreasing EHDV-TAU infection. Together, these data propose that LCN2 regulates PCa susceptibility to OVs through attenuation of PERK activity and increased IFN and ISG expression.

Lipocalin 2 inhibits actin glutathionylation to promote invasion and migration

Invasive and metastatic tumor cells show an increase in migration and invasion, making the processes contributing to these phenotypes potential therapeutic targets. Lipocalin 2 (LCN2; also known as neutrophil gelatinase-associated lipocalin) is a putative therapeutic target in multiple tumor types and promotes invasion and migration, although the mechanisms underlying these phenotypes are unclear. The data in this report demonstrate that LCN2 promotes actin polymerization, invasion, and migration by inhibiting actin glutathionylation. LCN2 inhibits actin glutathionylation by decreasing the levels of reactive oxygen species (ROS) and by reducing intracellular iron levels. Inhibiting LCN2 function leads to increased actin glutathionylation, decreased migration, and decreased invasion. These results suggest that LCN2 is a potential therapeutic target in invasive tumors.

The link between bone-derived factors osteocalcin, fibroblast growth factor 23, sclerostin, lipocalin 2 and tumor bone metastasis

The skeleton is the third most common site of metastatic disease, which causes serious bone complications and short-term prognosis in cancer patients. Prostate and breast cancers are responsible for the majority of bone metastasis, resulting in osteolytic or osteoblastic lesions. The crosstalk between bone cells and their interactions with tumor cells are important in the development of lesions. Recently, both preclinical and clinical studies documented the clinical relevance of bone-derived factors, including osteocalcin (OC) and its undercarboxylated form (ucOC), fibroblast growth factor 23 (FGF23), sclerostin (SCL), and lipocalin 2 (LCN2) as prognostic tumor biomarkers and potential therapeutic targets in bone metastasis. Both OC and ucOC could be useful targets for the prevention of bone metastasis in breast cancer. Moreover, elevated OC level may be a metastatic marker of prostate cancer. FGF23 is particularly important for those forms of cancer that primarily affect bone and/or are characterized by bone metastasis. In other tumor entities, increased FGF23 level is enigmatic. SCL plays a significant role in the pathogenesis of both osteolytic and osteoblastic lesions, as its levels are high in metastatic breast and prostate cancers. Elevated expression levels of LCN2 have been found in aggressive subtypes of cancer. However, its role in anti-metastasis varies significantly between different cancer types. Anyway, all aforementioned bone-derived factors can be used as promising tumor biomarkers. As metastatic bone disease is generally not curable, targeting bone factors represents a new trend in the prevention of bone metastasis and patient care.

Iron metabolism, ferroptosis, and lncRNA in cancer: knowns and unknowns

Cancer cells undergo substantial metabolic alterations to sustain increased energy supply and uncontrolled proliferation. As an essential trace element, iron is vital for many biological processes. Evidence has revealed that cancer cells deploy various mechanisms to elevate the cellular iron concentration to accelerate proliferation. Ferroptosis, a form of cell death caused by iron-catalyzed excessive peroxidation of polyunsaturated fatty acids (PUFAs), is a promising therapeutic target for therapy-resistant cancers. Previous studies have reported that long noncoding RNA (lncRNA) is a group of critical regulators involved in modulating cell metabolism, proliferation, apoptosis, and ferroptosis. In this review, we summarize the associations among iron metabolism, ferroptosis, and ferroptosis-related lncRNA in tumorigenesis. This information will help deepen understanding of the role of lncRNA in iron metabolism and raise the possibility of targeting lncRNA and ferroptosis in cancer combination therapy.

Adipose tissue-to-breast cancer crosstalk: Comprehensive insights

The review focuses on mechanistic evidence for the link between obesity and breast cancer. According to the IARC study, there is sufficient evidence that obesity is closely related to a variety of cancers. Among them, breast cancer is particularly disturbed by adipose tissue due to the unique histological structure of the breast. The review introduces the relationship between obesity and breast cancer from two aspects, including factors that promote tumorigenesis or metastasis. We summarize alterations in adipokines and metabolic pathways that contribute to breast cancer development. Breast cancer metastasis is closely related to obesity-induced pro-inflammatory microenvironment, adipose stem cells, and miRNAs. Based on the mechanism by which obesity causes breast cancer, we list possible therapeutic directions, including reducing the risk of breast cancer and inhibiting the progression of breast cancer. We also discussed the risk of autologous breast remodeling and fat transplantation. Finally, the causes of the obesity paradox and the function of enhancing immunity are discussed. Evaluating the balance between obesity-induced inflammation and enhanced immunity warrants further study.

Integrative transcriptomic and proteomic analysis reveals mechanisms of silica-induced pulmonary fibrosis in rats

Background

Silicosis is a systemic disease characterized by persistent inflammation and incurable pulmonary fibrosis. Although great effort has been made to understand the pathogenesis of the disease, molecular mechanism underlying silicosis is not fully elucidated. This study was aimed to explore proteomic and transcriptomic changes in rat model of silicosis.

Methods

Twenty male Wistar rats were randomly divided into two groups with 10 rats in each group. Rats in the model group were intratracheally instilled with 50 mg/mL silicon dioxide (1 mL per rat) and rats in the control group were treated with 1.0 mL saline (1 mL per rat). Twenty-eight days later, transcriptomic analysis by microarray and tandem mass tags (TMT)-based proteomic analysis were performed to reveal the expression of mRNAs and proteins in lung tissues. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were applied to analyze the altered genes and proteins. The integrated analysis was performed between transcriptome and proteome. The data were further verified by RT-qPCR and parallel reaction monitoring (PRM).

Results

In total, 1769 differentially expressed genes (DEGs) and 650 differentially expressed proteins (DEPs) were identified between the silicosis model and control groups. The integrated analysis showed 250 DEPs were correlated to the corresponding DEGs (cor-DEPs-DEGs), which were mainly enriched in phagosome, leukocyte transendothelial migration, complement and coagulation cascades and cellular adhesion molecule (CAM). These pathways are interrelated and converged at common points to produce an effect. GM2a, CHI3L1, LCN2 and GNAI1 are involved in the extracellular matrix (ECM) and inflammation contributing to fibrosis.

Conclusion

Our comprehensive transcriptome and proteome data provide new insights into the mechanisms of silicosis and helpful information for more targeted prevention and treatment of silicosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-021-01807-w.

Lipocalin 2 promotes inflammatory breast cancer tumorigenesis and skin invasion

Inflammatory breast cancer (IBC) is an aggressive form of primary breast cancer characterized by rapid onset and high risk of metastasis and poor clinical outcomes. The biological basis for the aggressiveness of IBC is still not well understood and no IBC-specific targeted therapies exist. In this study, we report that lipocalin 2 (LCN2), a small secreted glycoprotein belonging to the lipocalin superfamily, is expressed at significantly higher levels in IBC vs non-IBC tumors, independently of molecular subtype. LCN2 levels were also significantly higher in IBC cell lines and in their culture media than in non-IBC cell lines. High expression was associated with poor-prognosis features and shorter overall survival in IBC patients. Depletion of LCN2 in IBC cell lines reduced colony formation, migration, and cancer stem cell populations in vitro and inhibited tumor growth, skin invasion, and brain metastasis in mouse models of IBC. Analysis of our proteomics data showed reduced expression of proteins involved in cell cycle and DNA repair in LCN2-silenced IBC cells. Our findings support that LCN2 promotes IBC tumor aggressiveness and offer a new potential therapeutic target for IBC.

Comprehensive review of lipocalin 2-mediated effects in lung inflammation

Lipocalin-2 (LCN2) is an inflammatory mediator best known for its role as an innate acute-phase protein. LCN2 mediates the innate immune response to pathogens by sequestering iron, thereby inhibiting pathogen growth. Although LCN2 and its bacteriostatic properties are well studied, other LCN2 functions in the immune response to inflammatory stimuli are less well understood, such as its role as a chemoattractant and involvement in the regulation of cell migration and apoptosis. In the lungs, most studies thus far investigating the role of LCN2 in the immune response have looked at pathogenic inflammatory stimuli. Here, we compile data that explore the role of LCN2 in the immune response to various inflammatory stimuli in an effort to differentiate between protective versus detrimental roles of LCN2.

Lipocalin-2 Inhibits Osteosarcoma Cell Metastasis by Suppressing MET Expression via the MEK-ERK Pathway

Simple Summary

Higher neutrophil-derived cytokine lipocalin-2 (LCN2) expression possesses a versatile role in a myriad of cancers, but little is known about the role of LCN2 on osteosarcoma metastasis. In this study, we demonstrated that higher LCN2 inhibited cellular motility, migration, and invasion of osteosarcoma cells. Moreover, the phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 was decreased by LCN2 knockdown. Conclusively, LCN2 inhibits osteosarcoma cell metastasis by suppressing MET via the mitogen-activated protein kinases/ERK kinase (MEK)–ERK pathway.

Abstract

Higher neutrophil-derived cytokine lipocalin-2 (LCN2) expression possesses a versatile role in a myriad of cancers, but little is known about the role of LCN2 on osteosarcoma metastasis. In this study, we demonstrated that higher LCN2 inhibited cellular motility, migration, and invasion of osteosarcoma cells. Moreover, using RNA sequencing technology, we found that LCN2 repressed MET gene expression in U2OS cells. Manipulation of LCN2 levels influenced the migratory potential of osteosarcoma cells as cellular migration was enhanced by transfecting with vectors containing a constitutively active LCN2 cDNA and recombinant human LCN2. Moreover, the phosphorylation of mitogen-activated protein kinases/extracellular signal-regulated kinase (ERK) kinase (MEK) 1/2 and ERK 1/2 was decreased by LCN2 knockdown. Furthermore, the use of ERK inhibitor (U0126) and activator (tBHQ) confirmed that the pharmaceutic inhibition of MEK–ERK augmented the LCN2-mediated MET suppression and migration of U2OS and HOS cells. Conclusively, LCN2 inhibits osteosarcoma cell metastasis by suppressing MET via the MEK–ERK pathway.

Interaction between matrix metalloproteinase-9 (MMP-9) and neutrophil gelatinase-associated lipocalin (NGAL): A recent evolutionary event in primates

Matrix metalloproteases are known to represent an early step in the evolution of the immune system. Similarly, neutrophil gelatinase-associated lipocalin is known to be a key effector in immune response. MMP-9 interacts with NGAL, but their interaction mechanisms remain unclear. Functional interaction between proteins is ensured by coevolution. Protein coevolution was inferred by calculating the linear correlation coefficients between inter-protein distance matrices using MirrorTree. Among examined mammal species, we found a robust signal of MMP-9/NGAL coevolution exclusively within Primates (R = 0.96, p < 1e-06). Owing to the high conservation of these proteins among Mammals, we chose to utilize a recent version of Blocks in Sequences (BIS2) algorithm implemented in BIS2Analyzer webserver. Coevolution clusters between the two proteins were identified in MMP-9 fibronectin and hemopexin domains. Our results suggest that MMP-9/NGAL interaction is a recent evolutionary acquisition in Primates. Furthermore, MMP-9 hemopexin domain would represent a promising target for drug design against these molecules.

SIRT6 enhances oxidative phosphorylation in breast cancer and promotes mammary tumorigenesis in mice

BACKGROUND

Sirtuin 6 (SIRT6) is a NAD⁺-dependent deacetylase with key roles in cell metabolism. High SIRT6 expression is associated with adverse prognosis in breast cancer (BC) patients. However, the mechanisms through which SIRT6 exerts its pro-oncogenic effects in BC remain unclear. Here, we sought to define the role of SIRT6 in BC cell metabolism and in mouse polyoma middle T antigen (PyMT)-driven mammary tumors.

METHODS

We evaluated the effect of a heterozygous deletion of Sirt6 on tumor latency and survival of mouse mammary tumor virus (MMTV)-PyMT mice. The effect of SIRT6 silencing on human BC cell growth was assessed in MDA-MB-231 xenografts. We also analyzed the effect of Sirt6 heterozygous deletion, of SIRT6 silencing, and of the overexpression of either wild-type (WT) or catalytically inactive (H133Y) SIRT6 on BC cell pyruvate dehydrogenase (PDH) expression and activity and oxidative phosphorylation (OXPHOS), including respiratory complex activity, ATP/AMP ratio, AMPK activation, and intracellular calcium concentration.

RESULTS

The heterozygous Sirt6 deletion extended tumor latency and mouse survival in the MMTV-PyMT mouse BC model, while SIRT6 silencing slowed the growth of MDA-MB-231 BC cell xenografts. WT, but not catalytically inactive, SIRT6 enhanced PDH expression and activity, OXPHOS, and ATP/AMP ratio in MDA-MB-231 and MCF7 BC cells. Opposite effects were obtained by SIRT6 silencing, which also blunted the expression of genes encoding for respiratory chain proteins, such as UQCRFS1, COX5B, NDUFB8, and UQCRC2, and increased AMPK activation in BC cells. In addition, SIRT6 overexpression increased, while SIRT6 silencing reduced, intracellular calcium concentration in MDA-MB-231 cells. Consistent with these findings, the heterozygous Sirt6 deletion reduced the expression of OXPHOS-related genes, the activity of respiratory complexes, and the ATP/AMP ratio in tumors isolated from MMTV-PyMT mice.

CONCLUSIONS

Via its enzymatic activity, SIRT6 enhances PDH expression and activity, OXPHOS, ATP/AMP ratio, and intracellular calcium concentration, while reducing AMPK activation, in BC cells. Thus, overall, SIRT6 inhibition appears as a viable strategy for preventing or treating BC.

Iron and Cancer: 2020 Vision

New and provocative insights into the relationships between iron and cancer have been uncovered in recent years. These include delineation of connections that link cellular iron to DNA repair, genomic integrity, and oncogenic signaling as well as the discovery of ferroptosis, a novel iron-dependent form of cell death. In parallel, new molecules and pathways that regulate iron influx, intracellular iron trafficking, and egress in normal cells, and their perturbations in cancer have been discovered. In addition, insights into the unique properties of iron handling in tumor-initiating cells (cancer stem cells), novel contributions of the tumor microenvironment to the uptake and regulation of iron in cancer cells, and new therapeutic modalities that leverage the iron dependence of cancer have emerged.

MicroRNA-761 suppresses remodeling of nasal mucosa and epithelial-mesenchymal transition in mice with chronic rhinosinusitis through LCN2

Background

Chronic rhinosinusitis (CRS) is characterized by persistent symptomatic inflammation of the nasal passage and sinus mucosa. Various microRNAs (miRs) have been implicated in CRS. Hence, the current study was conducted to explore the effect of microRNA-761 (miR-761) on remodeling of nasal mucosa and epithelial–mesenchymal transition (EMT).

Methods

Bioinformatics analysis was initially performed to predict the differentially expressed genes (DEGs) associated with CRS. Gene targeting relationship between miR-761 and lipocalin 2 (LCN2) was analyzed by bioinformatics analysis and verified using dual-luciferase reporter gene assay. Histopathological analyses of the nasal mucosa tissues were conducted via hematoxylin–eosin (HE) and alcian blue (AB)-periodic acid Schiff (PAS) staining. ELISA was employed to determine the IL-8 and MMP-9 levels. To define downstream pathway of miR-761, levels of proteins related to LCN2/Twist1 signaling pathway were assessed. Additionally, the effects of miR-761 on EMT, proliferation, and apoptosis were determined.

Results

LCN2 was highly expressed in CRS. LCN2 was a target of miR-761. miR-761 overexpression or LCN2 silencing decreased IL-8 and MMP-9 levels and morphological changes in nasal epithelial tissue from CRS mice. Overexpressed miR-761 or silenced LCN2 decreased the expression of LCN2 and Twist1, indicating LCN2/Twist1 signaling pathway was inactivated. Moreover, miR-761 overexpression or LCN2 silencing reduced the expression of N-cadherin and vimentin, while increased that of E-cadherin, suggesting inhibition of EMT. Furthermore, miR-761 overexpression or LCN2 silencing promoted cell proliferation and inhibited cell apoptosis in CRS.

Conclusion

Taken together, miR-761 suppressed the remodeling of nasal mucosa through inhibition of LCN2 and the LCN2/Twist1 signaling pathway.

LAMTOR5 raises abnormal initiation of O-glycosylation in breast cancer metastasis via modulating GALNT1 activity

During malignancy, perturbed O-glycosylation confers global influence on cancer progression. As a hallmark of cancer metastasis, GalNAc-type O-glycosylation initiation is aberrantly raised, but the regulatory mechanism is still mysterious. Here, we show that LAMTOR5 raises abnormal initiation of O-glycosylation in breast cancer metastasis. LAMTOR5 was highly expressed in adenocarcinoma and correlated with Tn antigen, a product of O-glycosylation initiation, in both clinical metastatic breast cancer specimens and secondary metastasis mouse model. LAMTOR5-modulated O-glycosylation initiating enzyme GALNT1 conferred Tn accumulation and predicted poor survival. Mechanistically, LAMTOR5 stimulated transcriptions of GALNT1 through coactivating c-Jun, and triggered dislocation of GALNT1 in the endoplasmic reticulum (ER) via LAMTOR5 dependent-activation of c-Src. This unusual initiation of O-glycosylation resulted in the abundance of Tn modified glycoproteins, such as MUC1 and OPN. Collectively, our findings indicate that LAMTOR5/c-Jun/c-Src axis serves as the upstream regulator of abnormal O-glycosylation initiation and potential therapeutic targets in breast cancer metastasis.

Implication and role of neutrophil gelatinase-associated lipocalin in cancer: lipocalin-2 as a potential novel emerging comprehensive therapeutic target for a variety of cancer types

Cancer is a leading cause of mortalities worldwide. Over the past few decades, exploration of molecular mechanisms behind cancer initiation and progression has been of great interest in the viewpoint of both basic and clinical scientists. It is generally believed that identification of key molecules implicated in cancer pathology not only improves our understanding of the disease, but also could result in introduction of novel therapeutic strategies. Neutrophil gelatinase-associated lipocalin (NGAL)/lipocalin-2 (LCN2) is a member of lipocalin superfamily with a variety of functions. Although the main function of LCN2 is still unknown, many studies confirmed its significant role in the initiation, progression, and metastasis of various types of cancer. Furthermore, aberrant expression of LCN2 is also concerned with the chemo- and radio-resistant phenotypes of tumors. Here, we will review the contribution of known functions of LCN2 to the pathophysiology of cancer. We also highlight how the deregulated expression of LCN2 is associated with a variety of fatal types of cancer for which there are no effective therapeutic modalities. The unique and multiple functions of LCN2 and its widespread expression in different types of cancer prompted us to suggest LCN2 could be considered either as a valuable diagnostic and prognostic biomarker or as a potential novel therapeutic target.

The iron load of lipocalin-2 (LCN-2) defines its pro-tumour function in clear-cell renal cell carcinoma

BACKGROUND

We aimed at clarifying the role of lipocalin-2 (LCN-2) in clear-cell renal cell carcinoma (ccRCC). Since LCN-2 was recently identified as a novel iron transporter, we explored its iron load as a decisive factor in conferring its biological function.

METHODS

LCN-2 expression was analysed at the mRNA and protein level by using immunohistochemistry, RNAscope® and qRT-PCR in patients diagnosed with clear-cell renal cell carcinoma compared with adjacent healthy tissue. We measured LCN-2-bound iron by atomic absorption spectrometry from patient-derived samples and applied functional assays by using ccRCC cell lines, primary cells, and 3D tumour spheroids to verify the role of the LCN-2 iron load in tumour progression.

RESULTS

LCN-2 was associated with poor patient survival and LCN-2 mRNA clustered in high- and low-expressing ccRCC patients. LCN-2 protein was found overexpressed in tumour compared with adjacent healthy tissue, whereby LCN-2 was iron loaded. In vitro, the iron load determines the biological function of LCN-2. Iron-loaded LCN-2 showed pro-tumour functions, whereas iron-free LCN-2 produced adverse effects.

CONCLUSIONS

We provide new insights into the pro-tumour function of LCN-2. LCN-2 donates iron to cells to promote migration and matrix adhesion. Since the iron load of LCN-2 determines its pro-tumour characteristics, targeting either its iron load or its receptor interaction might represent new therapeutic options.

Secretomes from metastatic breast cancer cells, enriched for a prognostically unfavorable LCN2 axis, induce anti-inflammatory MSC actions and a tumor-supportive premetastatic lung

Cancer metastasis is responsible for the clear majority of cancer-related deaths. Survival and expansion of cancer cells at secondary sites requires that these premetastatic microenvironments be primed by primary tumor cells and their secreted factors. Efforts to date have been limited by immune-deficient in vivo models and/or the need for finely-tuned analysis time points that reduce contributions from early-disseminating cancer cells. In this regard, we developed a tumor cell-free syngeneic breast cancer model for characterizing tumor cell secretome-mediated reprogramming of premetastatic tissues. We demonstrate that secretomes from metastatic breast cancer cells differentially regulate the lung and brain, promoting a tumor-supportive lung microenvironment with both elevated CD73 expression and decreased TNFα expression. Using in vitro models of CD73-positive mesenchymal stem cells (MSCs) and macrophages/monocytes, we tested whether MSCs can mediate anti-inflammatory effects of metastatic breast cancer cells. Notably, conditioned media from metastatic Py230 cells reprogrammed the secretomes of MSCs toward an anti-inflammatory state. Mining transcriptome data from Py8119 and Py230 cells revealed a lipocalin 2 (LCN2) axis that is selectively expressed in the metastatic Py230 cells, predicts poor breast cancer patient survival and is elevated in circulating serum of mice chronically treated with conditioned media from Py230 cells. Taken together, these results establish the utility of an immune-competent tumor cell-free model for characterizing the mechanisms of breast cancer cell priming of the premetastatic niche, demonstrate that MSCs can mediate the anti-inflammatory effects of metastatic breast cancer cells and substantiate LCN2 as a promising therapeutic target for blocking breast cancer progression.

Iron as a Central Player and Promising Target in Cancer Progression

Iron is an essential element for virtually all organisms. On the one hand, it facilitates cell proliferation and growth. On the other hand, iron may be detrimental due to its redox abilities, thereby contributing to free radical formation, which in turn may provoke oxidative stress and DNA damage. Iron also plays a crucial role in tumor progression and metastasis due to its major function in tumor cell survival and reprogramming of the tumor microenvironment. Therefore, pathways of iron acquisition, export, and storage are often perturbed in cancers, suggesting that targeting iron metabolic pathways might represent opportunities towards innovative approaches in cancer treatment. Recent evidence points to a crucial role of tumor-associated macrophages (TAMs) as a source of iron within the tumor microenvironment, implying that specifically targeting the TAM iron pool might add to the efficacy of tumor therapy. Here, we provide a brief summary of tumor cell iron metabolism and updated molecular mechanisms that regulate cellular and systemic iron homeostasis with regard to the development of cancer. Since iron adds to shaping major hallmarks of cancer, we emphasize innovative therapeutic strategies to address the iron pool of tumor cells or cells of the tumor microenvironment for the treatment of cancer.

Lipocalin 2: a potential therapeutic target for breast cancer metastasis

Although systematic therapeutic approaches have reduced cancer-associated mortality, metastatic breast cancer can still evade therapy, particularly triple-negative breast cancer, which remains associated with high rates of cancer metastasis and has the worst clinical prognosis. Lipocalin 2 (LCN2) is a secreted glycoprotein that transports small lipophilic ligands. Its abnormal expression serves critical roles in the epithelial-to-mesenchymal transition process, angiogenesis, and cell migration and invasion in breast cancer. Notably, LCN2 functions as an initiator of carcinogenesis and metastasis by involving multiple signaling pathways. The present review aims to summarize research findings on the abnormal expression of LCN2 in breast cancer progression. Furthermore, the review highlights the latest developments of potential LCN2-targeting agents and proposed LCN2-associated molecular mechanisms with regard to breast cancer invasion and metastasis.

Exosomal RNA-profiling of pleural effusions identifies adenocarcinoma patients through elevated miR-200 and LCN2 expression

HYPOTHESIS

The inherent challenges associated with tissue biopsies from lung have spurred an interest in the use of liquid biopsies. Pleural effusions are one source of liquid biopsy. Recently, extracellular vesicles of endocytic origin, exosomes, have attracted interest as liquid biopsy of tumors as they are thought to be a mirror of their tumor of origin. Here, we aimed to analyze if RNA profiling of exosomes isolated from pleural effusions could differentiate patients with lung adenocarcinoma from patients with benign inflammatory processes.

METHODS

Exosomes were isolated from 36 pleural effusions from patients with adenocarcinoma (n = 18) and patients with benign inflammatory processes (n = 18). The two groups were balanced with respect to age and smoking history but with a gender bias towards males in the benign group. Profiling was conducted using RT-qPCR arrays covering 754 microRNAs and 624 mRNAs followed by statistical ranking of differentially regulated transcripts between the two patient cohorts.

RESULTS

RNA profiling revealed differential expression of 17 microRNAs and 71 mRNAs in pleural effusions collected from patients with lung adenocarcinoma compared to pleural effusions from benign lung disease. Overall, top differentially expressed microRNAs, including miR-200 family microRNAs, provided a stronger diagnostic power compared to top differentially expressed mRNAs. However, the mRNA transcript encoding Lipocalin-2 (LCN2) displayed the strongest diagnostic power of all analyzed transcripts (AUC: 0.9916).

CONCLUSIONS

Our study demonstrates that exosomal RNA profiling from pleural effusions can be used to identify patients with lung adenocarcinoma from individuals with benign processes and further proposes miR-200 microRNAs and LCN2 as diagnostic markers in lung cancer liquid biopsies.

Plakophilin3 loss leads to an increase in lipocalin2 expression, which is required for tumour formation

An increase in tumour formation and metastasis are observed upon plakophilin3 (PKP3) loss. To identify pathways downstream of PKP3 loss that are required for increased tumour formation, a gene expression analysis was performed, which demonstrated that the expression of lipocalin2 (LCN2) was elevated upon PKP3 loss and this is consistent with expression data from human tumour samples suggesting that PKP3 loss correlates with an increase in LCN2 expression. PKP3 loss leads to an increase in invasion, tumour formation and metastasis and these phenotypes were dependent on the increase in LCN2 expression. The increased LCN2 expression was due to an increase in the activation of p38 MAPK in the HCT116 derived PKP3 knockdown clones as LCN2 expression decreased upon inhibition of p38 MAPK. The phosphorylated active form of p38 MAPK is translocated to the nucleus upon PKP3 loss and is dependent on complex formation between p38 MAPK and PKP3. WT PKP3 inhibits LCN2 reporter activity in PKP3 knockdown cells but a PKP3 mutant that fails to form a complex with p38 MAPK cannot suppress LCN2 promoter activity. Further, LCN2 expression is decreased upon loss of p38β, but not p38α, in the PKP3 knockdown cells. These results suggest that PKP3 loss leads to an increase in the nuclear translocation of p38 MAPK and p38β MAPK is required for the increase in LCN2 expression.

PTEN PDZ-binding domain suppresses mammary carcinogenesis in the MMTV-PyMT breast cancer model

Phosphatase and tension homolog (PTEN) is a potent tumor suppressor that possesses a PDZ-binding domain (PDZ-BD) at the end of its carboxyl terminus, whose functions during tumorigenesis remains unclear. Here, we crossed a mouse strain with germline deletion of PTEN PDZ-BD with MMTV-PyMT breast cancer model, and found that knockout (KO) mice display normal development of mammary glands, but have both increased breast tumorigenicity and lung metastasis. Orthotopic allograft experiments suggest the loss of PTEN PDZ-BD in breast cancer cells rather than in tumor microenvironment plays a prominent role in increasing tumor burden. Through RNA-sequencing, we observed a significant downregulation of myoepithelial marker genes in both KO primary breast cancer and orthotopic allografts. Moreover, these myoepithelial marker genes are significantly downregulated in human breast cancer tissues, and are associated with poorer clinical prognosis. In addition, several homeobox genes were also identified to be downreguated in KO breast cancer, whose expressions showed significant positive correlation with myoepithelial marker genes. Overall, our findings suggest a novel tumor suppressive role of PTEN PDZ-BD in a murine model of breast cancer, and the mechanism involves the dysregulation of homeobox genes which may result in defective myoepithelial differentiation in breast cancer cells.

Macrophage-derived lipocalin-2 transports iron in the tumor microenvironment

While the importance of iron for tumor development is widely appreciated, the exact sources of tumor-supporting iron largely remain elusive. The possibility that iron might be provided by stromal cells in the tumor microenvironment was not taken into account so far. In the present study, we show that tumor-associated macrophages (TAM) acquire an iron-release phenotype upon their interaction with tumor cells, thereby increasing the availability of iron in the tumor microenvironment. Mechanistically, TAM expressed elevated levels of the high-affinity iron-binding protein lipocalin-2 (LCN-2), which appeared to be critical for the export of iron from TAM, and in turn enhanced tumor cell proliferation. Moreover, in PyMT-mouse tumors as well as in primary human breast tumors LCN-2 was predominantly expressed in the tumor stroma as compared to tumor cells. LCN-2 expression in the stroma further correlated with enhanced tumor proliferation in vivo. Our data suggest a dominant role of TAM in the tumor iron-management and identify LCN-2 as a critical iron transporter in this context. Targeting the LCN-2 iron export mechanism selectively in stromal cells might open for future iron-targeted tumor therapeutic approaches.

Iron Handling in Tumor-Associated Macrophages-Is There a New Role for Lipocalin-2?

Carcinogenesis is a multistep process. Besides somatic mutations in tumor cells, stroma-associated immunity is a major regulator of tumor growth. Tumor cells produce and secrete diverse mediators to create a local microenvironment that supports their own survival and growth. It is becoming apparent that iron acquisition, storage, and release in tumor cells is different from healthy counterparts. It is also appreciated that macrophages in the tumor microenvironment acquire a tumor-supportive, anti-inflammatory phenotype that promotes tumor cell proliferation, angiogenesis, and metastasis. Apparently, this behavior is attributed, at least in part, to the ability of macrophages to support tumor cells with iron. Polarization of macrophages by apoptotic tumor cells shifts the profile of genes involved in iron metabolism from an iron sequestering to an iron-release phenotype. Iron release from macrophages is supposed to be facilitated by ferroportin. However, lipid mediators such as sphingosine-1-phosphate, released form apoptotic tumor cells, upregulate lipocalin-2 (Lcn-2) in macrophages. This protein is known to bind siderophore-complexed iron and thus, may participate in iron transport in the tumor microenvironment. We describe how macrophages handle iron in the tumor microenvironment, discuss the relevance of an iron-release macrophage phenotype for tumor progression, and propose a new role for Lcn-2 in tumor-associated macrophages.

Mint3 in bone marrow-derived cells promotes lung metastasis in breast cancer model mice

Breast cancer is one of the most common cancers in women in the world. Although breast cancer is well treatable at the early stage, patients with distant metastases show a poor prognosis. Data from recent studies using transplantation models indicate that Mint3/APBA3 might promote breast cancer malignancy. However, whether Mint3 indeed contributes to tumor development, progression, or metastasis in vivo remains unclear. To address this, here we examined whether Mint3 depletion affects tumor malignancy in MMTV-PyMT breast cancer model mice. In MMTV-PyMT mice, Mint3 depletion did not affect tumor onset and tumor growth, but attenuated lung metastases. Experimental lung metastasis of breast cancer Met-1 cells derived from MMTV-PyMT mice also decreased in Mint3-depleted mice, indicating that host Mint3 expression affected lung metastasis of MMTV-PyMT-derived breast cancer cells. Further bone marrow transplant experiments revealed that Mint3 in bone marrow-derived cells promoted lung metastasis in MMTV-PyMT mice. Thus, targeting Mint3 in bone marrow-derived cells might be a good strategy for preventing metastasis and improving the prognosis of breast cancer patients.

Lipocalin 2: An Emerging Player in Iron Homeostasis and Inflammation

Lipocalin 2 (Lcn2), an innate immune protein, has emerged as a critical iron regulatory protein during physiological and inflammatory conditions. As a bacteriostatic factor, Lcn2 obstructs the siderophore iron-acquiring strategy of bacteria and thus inhibits bacterial growth. As part of host nutritional immunity, Lcn2 facilitates systemic, cellular, and mucosal hypoferremia during inflammation, in addition to stabilizing the siderophore-bound labile iron pool. In this review, we summarize recent advances in understanding the interaction between Lcn2 and iron, and its effects in various inflammatory diseases. Lcn2 exerts mostly a protective role in infectious and inflammatory bowel diseases, whereas both beneficial and detrimental functions have been documented in neurodegenerative diseases, metabolic syndrome, renal disorders, skin disorders, and cancer. Further animal and clinical studies are necessary to unveil the multifaceted roles of Lcn2 in iron dysregulation during inflammation and to explore its therapeutic potential for treating inflammatory diseases.

Lipocalin-2 and iron trafficking in the tumor microenvironment

Iron is an essential element for virtually all organisms. It facilitates cell proliferation and growth but also contributes to major hallmarks of cancer such as tumor initiation, growth, and metastasis. Often, iron handling of tumor cells is disturbed, with altered iron acquisition, efflux, and storage. Targeting perturbed iron metabolic pathways might open opportunities towards novel approaches in cancer treatment. It is becoming clear that cells of the tumor microenvironment such as macrophages contribute to tumor progression. Since macrophages evolved a multitude of mechanisms to sequester, transport, store, and release iron it can be speculated that tumor cells educate them to supply iron to support tumor growth. Recent evidence supports the existence of transferrin-independent iron transport mechanisms in the tumor microenvironment, which points to local iron transport proteins such as lipocalin-2 and/or low molecular weight iron-trafficking substances such as siderophores. We hypothesize that tumor cells educate immune cells, i.e. macrophages in their neighborhood to make them delivering iron for the benefit of cancer progression. In particular, we pay attention to recent developments, pointing to lipocalin-2 and siderophores as alternative iron transport molecules in the tumor microenvironment.

Lipocalin-2 Promotes Endoplasmic Reticulum Stress and Proliferation by Augmenting Intracellular Iron in Human Pulmonary Arterial Smooth Muscle Cells

Endoplasmic reticulum (ER) stress, a feature of many conditions associated with pulmonary hypertension (PH), is increasingly recognized as a common response to promote proliferation in the walls of pulmonary arteries. Increased expression of Lipocalin-2 in PH led us to test the hypothesis that Lipocalin-2, a protein known to sequester iron and regulate it intracellularly, might facilitate the ER stress and proliferation in pulmonary arterial smooth muscle cells (PASMCs). In this study, we observed greatly increased Lcn2 expression accompanied with increased ATF6 cleavage in a standard rat model of pulmonary hypertension induced by monocrotaline. In cultured human PASMCs, Lcn2 significantly promoted ER stress (determined by augmented cleavage and nuclear localization of ATF6, up-regulated transcription of GRP78 and NOGO, increased expression of SOD2, and mild augmented mitochondrial membrane potential) and proliferation (assessed by Ki67 staining and BrdU incorporation). Lcn2 promoted ER stress accompanied with augmented intracellular iron levels in human PASMCs. Treatment human PASMCs with FeSO4 induced the similar ER stress and proliferation response and iron chelator (deferoxamine) abrogated the ER stress and proliferation induced by Lcn2 in cultured human PASMCs. In conclusion, Lcn2 significantly promoted human PASMC ER stress and proliferation by augmenting intracellular iron. The up-regulation of Lcn2 probably involved in the pathogenesis and progression of PH.

Comparison of the Adipose and Luminal Mammary Gland Compartment as Orthotopic Inoculation Sites in a 4T1-Based Immunocompetent Preclinical Model for Triple-Negative Breast Cancer

Breast tumorigenesis is classically studied in mice by inoculating tumor cells in the fat pad, the adipose compartment of the mammary gland. Alternatively, the mammary ducts, which constitute the luminal mammary gland compartment, also provide a suitable inoculation site to induce breast cancer in murine models. The microenvironments in these compartments influence tumor cell progression, yet this effect has not been investigated in an immunocompetent context. Here, we compared both mammary gland compartments as distinct inoculation sites, taking into account the immunological aspect by inoculating 4T1 tumor cells in immunocompetent mice. Following tumor cell inoculation in the adipose compartment of non-pretreated/naive, hormonally pretreated/naive and non-pretreated/lactating mice, the primary tumors developed similarly. However, a slower onset of primary tumor growth was found after inoculations in the luminal compartment of non-pretreated/lactating mice. Despite this difference in tumor development rate, metastasis to the liver and lungs was equally observed and was accompanied by lymphatic spreading of tumor cells and progressive splenomegaly with both inoculation types. Chitinase 3-like 1 (CHI3L1) and lipocalin 2 (LCN2) served as innovative biomarkers for disease progression showing increased levels in primary tumors and sera of the non-pretreated/lactating inoculation groups. A slower increase in circulating CHI3L1 but not LCN2 levels, was observed after inoculations in the luminal compartment which corroborated the slower tumor development at this inoculation site. Our results highlight the critical impact of different mammary gland compartments on tumor development in syngeneic murine models and support the use of novel tumor progression biomarkers in an immune-competent environment.

Tumour stroma-derived lipocalin-2 promotes breast cancer metastasis

Tumour cell-secreted factors skew infiltrating immune cells towards a tumour-supporting phenotype, expressing pro-tumourigenic mediators. However, the influence of lipocalin-2 (Lcn2) on the metastatic cascade in the tumour micro-environment is still not clearly defined. Here, we explored the role of stroma-derived, especially macrophage-released, Lcn2 in breast cancer progression. Knockdown studies and neutralizing antibody approaches showed that Lcn2 contributes to the early events of metastasis in vitro. The release of Lcn2 from macrophages induced an epithelial-mesenchymal transition programme in MCF-7 breast cancer cells and enhanced local migration as well as invasion into the extracellular matrix, using a three-dimensioanl (3D) spheroid model. Moreover, a global Lcn2 deficiency attenuated breast cancer metastasis in both the MMTV-PyMT breast cancer model and a xenograft model inoculating MCF-7 cells pretreated with supernatants from wild-type and Lcn2-knockdown macrophages. To dissect the role of stroma-derived Lcn2, we employed an orthotopic mammary tumour mouse model. Implantation of wild-type PyMT tumour cells into Lcn2-deficient mice left primary mammary tumour formation unaltered, but specifically reduced tumour cell dissemination into the lung. We conclude that stroma-secreted Lcn2 promotes metastasis in vitro and in vivo, thereby contributing to tumour progression. Our study highlights the tumourigenic potential of stroma-released Lcn2 and suggests Lcn2 as a putative therapeutic target. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Lipocalin 2 prevents oral cancer metastasis through carbonic anhydrase IX inhibition and is associated with favourable prognosis

Lipocalin 2 (LCN2), a secreted glycoprotein, is up- or downregulated in different human cancers. At present, the functional role of LCN2 in the progression of oral squamous cell carcinoma (OSCC), which accounts for most head and neck cancers, remains poorly understood, particularly with respect to its involvement in invasion and metastasis. In this study, we observed that LCN2 expression decreased in patients with OSCC and lymph node metastasis compared with that in patients without metastasis. A higher LCN2 expression correlated with the survival of patients with OSCC. Furthermore, LCN2 overexpression in OSCC cells reduced in vitro migration and invasion and in vivo metastasis, whereas its silencing induced an increase in cell motility. Mechanistically, LCN2 inhibited the cell motility of OSCC cells through hypoxia-inducible factor (HIF)-1α-dependent transcriptional inhibition of the carbonic anhydrase IX (CAIX). CAIX overexpression relieved the migration inhibition imposed by LCN2 overexpression in OSCC cells. Moreover, a microRNA (miR) analysis revealed that LCN2 can suppress CAIX expression and cell migration through miR-4505 induction. Examination of tumour tissues from patients with OSCC and OSCC-transplanted mice revealed an inverse correlation between LCN2 and CAIX expression. Furthermore, patients with LCN2(strong)/CAIX(weak) revealed the lowest frequency of lymph node metastasis and the longest survival. Our findings suggest that LCN2 suppresses tumour metastasis by targeting the transcriptional and post-transcriptional regulation of CAIX in OSCC cells. LCN2 overexpression may be a novel OSCC treatment strategy and a useful biomarker for predicting OSCC progression.

A role for novel adipose tissue-secreted factors in obesity-related carcinogenesis

Obesity, a pandemic disease, is caused by an excessive accumulation of fat that can have detrimental effects on health. Adipose tissue plays a very important endocrine role, secreting different molecules that affect body physiology. In obesity, this function is altered, leading to a dysfunctional production of several factors, known as adipocytokines. This process has been linked to various comorbidities associated with obesity, such as carcinogenesis. In fact, several classical adipocytokines with increased levels in obesity have been demonstrated to exert a pro-carcinogenic role, including leptin, TNF-α, IL-6 and resistin, whereas others like adiponectin, with decreased levels in obesity, might have an anti-carcinogenic function. In this expanding field, new proteomic techniques and approaches have allowed the identification of novel adipocytokines, a number of which exhibit an altered production in obesity and type 2 diabetes and thus are related to adiposity. Many of these novel adipocytokines have also been identified in various tumour types, such as that of the breast, liver or endometrium, thereby increasing the list of potential contributors to carcinogenesis. This review is focused on the regulation of these novel adipocytokines by obesity, including apelin, endotrophin, FABP4, lipocalin 2, omentin-1, visfatin, chemerin, ANGPTL2 or osteopontin, emphasizing its involvement in tumorigenesis.

[Effect of Inhibiting NGAL Gene Expression on A549 Lung Cancer Cell Migration and Invasion]

背景与目的

检测NGAL在肺癌组织的表达，观察小干扰RNA（siRNA）沉默NGAL基因表达对肺癌细胞增殖及侵袭能力的影响。

方法

应用免疫组织化学检测肺癌组织中NGAL表达。通过RNAi技术干扰NGAL后，运用定量PCR、Western blot技术，观察干扰NGAL基因效率。干扰NGAL后，MTT检测细胞增殖、Transwell实验检测细胞迁移侵袭能力，细胞划痕愈合能力，免疫荧光及Western blot方法检测上皮细胞-间质细胞转化（epithelial-mesenchymal transition, EMT）相关的蛋白E-cadherin及Vimentin的表达情况。

结果

肺癌中NGAL阳性率高于癌旁组织（P < 0.01）。NGAL-siRNA转染组，癌细胞中NGAL基因及蛋白水平表达都受到明显的抑制。NGAL-siRNA转染组细胞增殖能力，迁移及侵袭能力相对于对照组都降低，差异具有统计学意义（P < 0.05）。干扰NGAL，E-cadherin的表达升高，Vimentin的表达水平降低。干扰NGAL，MMP-2和MMP-9蛋白表达水平降低。

结论

NGAL在肺癌组织高表达，且在肺癌细胞的增殖、侵袭和迁移及EMT过程中起着重要作用。NGAL可能是肺癌浸润和转移的一个重要参考指标，可为肺癌治疗提供潜在的靶点。

Down-regulation of neutrophil gelatinase-associated lipocalin in head and neck squamous cell carcinoma correlated with tumorigenesis, not with metastasis

To examine the significance of the Neutrophil gelatinase-associated lipocalin (NGAL) in diagnosing head and neck squamous cell carcinoma (HNSCC) and predicting regional metastasis. We first used GEO dataset to analyze the NGAL gene expression in HNSCC. Then, we summarized the characteristics of patients retrospectively selected in clinic. Expression of NGAL protein in human HNSCC tumor, lymph node and normal samples were analyzed using immunohistochemistry. Next, we further investigated the NGAL expression in a tissue microassay to analyze the relationship between NGAL protein expression and TNM stage. Finally, we tested the NGAL protein expression in head and neck cancer cell lines. Analysis of GEO dataset concluded that NGAL gene expression in HNSCC was lower than that in normal tissue (P<0.01). There was no statistically significant difference of NGAL gene expression between T-stage and N-stage (P>0.05). NGAL protein expression in tumor was lower than that in normal tissue (P<0.01). There was no statistically significant difference of NGAL protein expression between metastasis group and non-metastasis group (P>0.05). Expression of NGAL protein was not correlated with TNM stage of HNSCC. Aggressive HNSCC cell lines have lower NGAL protein expression. Our data demonstrated that the expression of NGAL protein was correlated with tumorigenesis of HNSCC, but not with regional metastasis. It may serve as a novel biomarker for prognostic evaluation of patients with HNSCC.

Deletion of phospholipase A2 group IVc induces apoptosis in rat mammary tumour cells by the nuclear factor-κB/lipocalin 2 pathway

Although some forms of phospholipase A2, the initiator of the arachidonic acid cascade, contribute to carcinogenesis in many organs, the contribution of phospholipase A2 group IVc (Pla2g4c) remains to be clarified and the function of the enzyme in cancer development is unknown. The Hirosaki hairless rat (HHR), a mutant rat strain with autosomal recessive inheritance, derived spontaneously from the Sprague-Dawley rat (SDR). The HHRs showed a lower incidence and much smaller volume of mammary tumours induced by 7,12-dimethylbenz[a]anthracene, and a markedly increased number of TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP nick-end labelling)-positive apoptotic cells was detected. Array comparative genomic hybridization and PCR analyses revealed the deletion of 50-kb genomic DNA on 1q21, including Pla2g4c, in HHRs. The Pla2g4c gene was expressed in the ductal carcinoma cells and myoepithelial cells in SDRs, but not in HHRs. The direct involvement of Pla2g4c in the prevention of cell death was demonstrated through the inhibition of its expression in rat mammary tumour RMT-1 cells using siRNA. This treatment also induced expression of lipocalin 2 (Lcn2) and other NF-κB (nuclear factor κB)-related genes. siRNA-induced apoptosis was inhibited by Lcn2 repression or NF-κB inhibitors. This is the first report on Pla2g4c gene-deficient rats and their low susceptibility to mammary carcinogenesis by enhancing NF-κB/Lcn2-induced apoptosis.

Lipocalin-2 inhibits osteoclast formation by suppressing the proliferation and differentiation of osteoclast lineage cells

Lipocalin-2 (LCN2) is a member of the lipocalin superfamily and plays a critical role in the regulation of various physiological processes, such as inflammation and obesity. In this study, we report that LCN2 negatively modulates the proliferation and differentiation of osteoclast precursors, resulting in impaired osteoclast formation. The overexpression of LCN2 in bone marrow-derived macrophages or the addition of recombinant LCN2 protein inhibits the formation of multinuclear osteoclasts. LCN2 suppresses macrophage colony-stimulating factor (M-CSF)-induced proliferation of osteoclast precursor cells without affecting their apoptotic cell death. Interestingly, LCN2 decreases the expression of the M-CSF receptor, c-Fms, and subsequently blocks its downstream signaling cascades. In addition, LCN2 inhibits RANKL-induced osteoclast differentiation and attenuates the expression of c-Fos and nuclear factor of activated T cells c1 (NFATc1), which are important modulators in osteoclastogenesis. Mechanistically, LCN2 inhibits NF-κB signaling pathways, as demonstrated by the suppression of IκBα phosphorylation, nuclear translocation of p65, and NF-κB transcriptional activity. Thus, LCN2 is an anti-osteoclastogenic molecule that exerts its effects by retarding the proliferation and differentiation of osteoclast lineage cells.

Biomarkers of erlotinib response in non-small cell lung cancer tumors that do not harbor the more common epidermal growth factor receptor mutations

Non-small cell lung cancer (NSCLC) represents approximately 85% of all lung cancers, which are the leading cause of cancer-related deaths in the world. Tyrosine kinase inhibitors such as erlotinib represent one therapeutic options presently recommended for tumors produced by activating mutations in the gene coding of epidermal growth factor receptor (EGFR). The aim of this study is the identification of possible biomarkers for tumor sensitivity to erlotinib in the absence of the main EGFR mutations. The erlotinib sensitivity of cells isolated from 41 untreated NSCLC patients was determined and compared with the presence of the more frequent EGFR mutations. Several patients had tumor cells highly sensitive to erlitinib in the absence of the EGFR mutations analyzed. The gene expression profile of 3 erlotinib-sensitive tumors was compared with that of 4 resistant tumors by DNA microarray hybridization. Sixteen genes were expressed at significantly higher levels in the resistant tumors than in the sensitive tumors. The possible correlation between erlotinib sensitivity and the expression of these genes was further analyzed using the data for the NSCLC, breast cancer and colon cancer cell lines of the NCI60 collection. The expression of these genes was correlated with the overall survival of 5 patients treated with erlotinib, according to The Cancer Genome Atlas (TCGA) database. Overlapping groups of 7, 5 and 3 genes, including UGT1A6, TRIB3, MET, MMP7, COL17A1, LCN2 and PTPRZ1, whose expression correlated with erlotinib activity was identified. In particular, low MET expression levels showed the strongest correlation.

Roles of neutrophil gelatinase-associated lipocalin (NGAL) in human cancer

Cancer remains one of the major cause of death in the Western world. Although, it has been demonstrated that new therapies can improve the outcome of cancer patients, still many patients relapse after treatment. Therefore, there is a need to identify novel factors involved in cancer development and/or progression. Recently, neutrophil gelatinase-associated lipocalin (NGAL) has been suggested as a key player in different cancer types. Its oncogenic effect may be related to the complex NGAL/MMP-9. In the present study, NGAL was analyzed at both transcript and protein levels in different cancer types by analysing 38 public available microarray datasets and the Human Protein Atlas tool.

NGAL transcripts were significantly higher in the majority of solid tumors compared to the relative normal tissues for every dataset analyzed. Furthermore, concordance of NGAL at both mRNA and protein levels was observed for 6 cancer types including bladder, colorectal, liver, lung, ovarian, and pancreatic. All metastatic tumors showed a decrease of NGAL expression when compared to matched primary lesions.

According to these results, NGAL is a candidate marker for tumor growth in a fraction of solid tumors. Further investigations are required to elucidate the function of NGAL in tumor development and metastatic processes.

Iron homeostasis and tumorigenesis: molecular mechanisms and therapeutic opportunities

Excess iron is tightly associated with tumorigenesis in multiple human cancer types through a variety of mechanisms including catalyzing the formation of mutagenic hydroxyl radicals, regulating DNA replication, repair and cell cycle progression, affecting signal transduction in cancer cells, and acting as an essential nutrient for proliferating tumor cells. Thus, multiple therapeutic strategies based on iron deprivation have been developed in cancer therapy. During the past few years, our understanding of genetic association and molecular mechanisms between iron and tumorigenesis has expanded enormously. In this review, we briefly summarize iron homeostasis in mammals, and discuss recent progresses in understanding the aberrant iron metabolism in numerous cancer types, with a focus on studies revealing altered signal transduction in cancer cells.

Estrogen receptor (ER)α-regulated lipocalin 2 expression in adipose tissue links obesity with breast cancer progression

Obesity is associated with increased breast cancer (BrCA) incidence. Considering that inactivation of estrogen receptor (ER)α promotes obesity and metabolic dysfunction in women and female mice, understanding the mechanisms and tissue-specific sites of ERα action to combat metabolic-related disease, including BrCA, is of clinical importance. To study the role of ERα in adipose tissue we generated fat-specific ERα knock-out (FERKO) mice. Herein we show that ERα deletion increased adipocyte size, fat pad weight, and tissue expression and circulating levels of the secreted glycoprotein, lipocalin 2 (Lcn2), an adipokine previously associated with BrCA development. Chromatin immunoprecipitation and luciferase reporter studies showed that ERα binds the Lcn2 promoter to repress its expression. Because adipocytes constitute an important cell type of the breast microenvironment, we examined the impact of adipocyte ERα deletion on cancer cell behavior. Conditioned medium from ERα-null adipocytes and medium containing pure Lcn2 increased proliferation and migration of a subset of BrCA cells in culture. The proliferative and promigratory effects of ERα-deficient adipocyte-conditioned medium on BrCA cells was reversed by Lcn2 deletion. BrCA cell responsiveness to exogenous Lcn2 was heightened in cell types where endogenous Lcn2 expression was minimal, but components of the Lcn2 signaling pathway were enriched, i.e. SLC22A17 and 3-hydroxybutyrate dehydrogenase (BDH2). In breast tumor biopsies from women diagnosed with BrCA we found that BDH2 expression was positively associated with adiposity and circulating Lcn2 levels. Collectively these data suggest that reduction of ERα expression in adipose tissue promotes adiposity and is linked with the progression and severity of BrCA via increased adipocyte-specific Lcn2 production and enhanced tumor cell Lcn2 sensitivity.

Dendritic cell-secreted lipocalin2 induces CD8+ T-cell apoptosis, contributes to T-cell priming and leads to a TH1 phenotype

Lipocalin 2 (LCN2), which is highly expressed by dendritic cells (DCs) when treated with dexamethasone (Dex) and lipopolysaccharide (LPS), plays a key role in the defence against bacteria and is also involved in the autocrine apoptosis of T-cells. However, the function of LCN2 when secreted by DCs is unknown: this is a critical gap in our understanding of the regulation of innate and adaptive immune systems. Tolerance, stimulation and suppression are functions of DCs that facilitate the fine-tuning of the immune responses and which are possibly influenced by LCN2 secretion. We therefore examined the role of LCN2 in DC/T-cell interaction. WT or Lcn2^−/− bone marrow-derived DCs were stimulated with LPS or LPS+IFN-γ with and without Dex and subsequently co-cultured with T-cells from ovalbumin-specific TCR transgenic (OT-I and OT-II) mice. We found that CD8⁺ T-cell apoptosis was highly reduced when Lcn2^−/− DCs were compared with WT. An in vivo CTL assay, using LPS-treated DCs, showed diminished killing ability in mice that had received Lcn2^−/− DCs compared with WT DCs. As a consequence, we analysed T-cell proliferation and found that LCN2 participates in T-cell-priming in a dose-dependent manner and promotes a T_H1 microenvironment. DC-secreted LCN2, whose function has previously been unknown, may in fact have an important role in regulating the balance between T_H1 and T_H2. Our results yield insights into DC-secreted LCN2 activity, which could play a pivotal role in cellular immune therapy and in regulating immune responses.

Absence of intestinal PPARγ aggravates acute infectious colitis in mice through a lipocalin-2-dependent pathway

To be able to colonize its host, invading Salmonella enterica serovar Typhimurium must disrupt and severely affect host-microbiome homeostasis. Here we report that S. Typhimurium induces acute infectious colitis by inhibiting peroxisome proliferator-activated receptor gamma (PPARγ) expression in intestinal epithelial cells. Interestingly, this PPARγ down-regulation by S. Typhimurium is independent of TLR-4 signaling but triggers a marked elevation of host innate immune response genes, including that encoding the antimicrobial peptide lipocalin-2 (Lcn2). Accumulation of Lcn2 stabilizes the metalloproteinase MMP-9 via extracellular binding, which further aggravates the colitis. Remarkably, when exposed to S. Typhimurium, Lcn2-null mice exhibited a drastic reduction of the colitis and remained protected even at later stages of infection. Our data suggest a mechanism in which S. Typhimurium hijacks the control of host immune response genes such as those encoding PPARγ and Lcn2 to acquire residence in a host, which by evolution has established a symbiotic relation with its microbiome community to prevent pathogen invasion.

Enteric pathogens like S. Typhimurium convert the host intestine into an inflamed environment in which they are well adapted to thrive. However, the precise strategy that this pathogen employs to achieve such favorable conditions for its survival remains unclear. Here, we uncovered a novel mechanism whereby S. Typhimurium inhibits the expression of the transcription factor PPARγ in the host intestine, surprisingly without TLR-4 involvement; this inhibition worsened the severity of the host's colitis. Subsequent detailed analysis revealed that colitis severity was coupled with elevated levels of antimicrobials like Lcn2, which stabilized the pro-inflammatory endopeptidase MMP-9 in the intestinal milieu. Combination of this escalated antimicrobial action together with enhanced protease activity disrupted the intestinal homeostasis, promoting an inflamed environment suitable for S. Typhimurium. Interestingly, using Lcn2 mutant mice we show that lack of Lcn2 effectively reduced tissue damage and the degree of inflammation, thus supporting a pivotal role of Lcn2 and MMP-9 in infectious colitis. Our data suggests a model whereby the pathogenesis of S. Typhimurium involves manipulation of the host innate immune and protease system, here illustrated by PPARγ, Lcn2 and MMP-9, to establish colonization and infection within the host.

Lipocalin-2 negatively modulates the epithelial-to-mesenchymal transition in hepatocellular carcinoma through the epidermal growth factor (TGF-beta1)/Lcn2/Twist1 pathway

Lipocalin-2 (Lcn2) is preferentially expressed in hepatocellular carcinoma (HCC). However, the functional role of Lcn2 in HCC progression is still poorly understood, particularly with respect to its involvement in invasion and metastasis. The purpose of this study was to investigate whether Lcn2 is associated with the epithelial-mesenchymal transition (EMT) in HCC and to elucidate the underlying signaling pathway(s). Lcn2 was preferentially expressed in well-differentiated HCC versus liver cirrhosis tissues, and its expression was positively correlated with the stage of HCC. The characteristics of EMT were reversed by adenoviral transduction of Lcn2 into SH-J1 cells, including the down-regulation of N-cadherin, vimentin, alpha-smooth muscle actin, and fibronectin, and the concomitant up-regulation of CK8, CK18, and desmoplakin I/II. Knockdown of Lcn2 by short hairpin RNA (shRNA) in HKK-2 cells expressing high levels of Lcn2 was associated with EMT. Epidermal growth factor (EGF) or transforming growth factor beta1 (TGF-β1) treatment resulted in down-regulation of Lcn2, accompanied by an increase in Twist1 expression and EMT in HCC cells. Stable Lcn2 expression in SH-J1 cells reduced Twist1 expression, inhibited cell proliferation and invasion in vitro, and suppressed tumor growth and metastasis in a mouse model. Furthermore, EGF or TGF-β1 treatment barely changed EMT marker expression in SH-J1 cells ectopically expressing Lcn2. Ectopic expression of Twist1 induced EMT marker expression even in cells expressing Lcn2, indicating that Lcn2 functions downstream of growth factors and upstream of Twist1.

CONCLUSION

Together, our findings indicate that Lcn2 can negatively modulate the EMT in HCC cells through an EGF (or TGF-β1)/Lcn2/Twist1 pathway. Thus, Lcn2 may be a candidate metastasis suppressor and a potential therapeutic target in HCC.

Bisected, complex N-glycans and galectins in mouse mammary tumor progression and human breast cancer

Bisected, complex N-glycans on glycoproteins are generated by the glycosyltransferase MGAT3 and cause reduced cell surface binding of galectins. Previously, we showed that MGAT3 reduces growth factor signaling and retards mammary tumor progression driven by the Polyoma middle T antigen (PyMT) expressed in mammary epithelium under the mouse mammary tumor virus (MMTV) promoter. However, the penetrance of the tumor phenotype became variable in mixed FVB/N and C57BL/6 female mice and we therefore investigated a congenic C57BL/6 Mgat3(-/-)/MMTV-PyMT model. In the absence of MGAT3, C57BL/6 Mgat3(-/-)/MMTV-PyMT females exhibited accelerated tumor appearance and increased tumor burden, glucose uptake in tumors and lung metastasis. Nevertheless, activation of extracellular signal-regulated kinase (ERK)1/2 or protein kinase B (AKT) was reduced in ∼20-week C57BL/6 MMTV-PyMT tumors lacking MGAT3. Activation of focal adhesion kinase (FAK), protein tyrosine kinase Src, and p38 mitogen-activated protein kinase were similar to that of controls. All the eight mouse galectin genes were expressed in mammary tumors and tumor epithelial cells (TECs), but galectin-2 and -12 were not detected by western analysis in tumors, and galectin-7 was not detected in 60% of the TEC lines. From microarray data reported for human breast cancers, at least 10 galectin and 7 N-glycan N-acetylglucosaminyl (GlcNAc)-transferase (MGAT) genes are expressed in tumor tissue, and expression often varies significantly between different breast cancer subtypes. Thus, in summary, while MGAT3 and bisected complex N-glycans retard mouse mammary tumor progression, genetic background may modify this effect; identification of key galectins that promote mammary tumor progression in mice is not straightforward because all the eight galectin genes are expressed; and high levels of MGAT3, galectin-4, -8, -10, -13 and -14 transcripts correlate with better relapse-free survival in human breast cancer.