Expression and significance of hypoxia inducible factor-1α and lysyl oxidase in non-small cell lung cancer

Lysyl Oxidase Family Proteins: Prospective Therapeutic Targets in Cancer

The lysyl oxidase (LOX) family, consisting of LOX and LOX-like proteins 1–4 (LOXL1–4), is responsible for the covalent crosslinking of collagen and elastin, thus maintaining the stability of the extracellular matrix (ECM) and functioning in maintaining connective tissue function, embryonic development, and wound healing. Recent studies have found the aberrant expression or activity of the LOX family occurs in various types of cancer. It has been proved that the LOX family mainly performs tumor microenvironment (TME) remodeling function and is extensively involved in tumor invasion and metastasis, immunomodulation, proliferation, apoptosis, etc. With relevant translational research in progress, the LOX family is expected to be an effective target for tumor therapy. Here, we review the research progress of the LOX family in tumor progression and therapy to provide novel insights for future exploration of relevant tumor mechanism and new therapeutic targets.

Lysyl Oxidase Family Enzymes and Their Role in Tumor Progression

The five genes of the lysyl oxidase family encode enzymes that covalently cross-link components of the extracellular matrix, such as various types of collagen and elastin, and, thus, promote the stabilization of extracellular matrixes. Several of these genes, in particular lysyl oxidase (LOX) and lysyl oxidase like-2 (LOXL2) were identified as genes that are upregulated by hypoxia, and promote tumor cells invasion and metastasis. Here, we focus on the description of the diverse molecular mechanisms by which the various lysyl oxidases affect tumor progression. We also describe attempts that have been made, and are still on-going, that focus on the development of efficient lysyl oxidase inhibitors for the treatment of various forms of cancer, and of diseases associated with abnormal fibrosis.

Hypoxia in Lung Cancer Management: A Translational Approach

Simple Summary

Hypoxia is a common feature of lung cancers. Nonetheless, no guidelines have been established to integrate hypoxia-associated biomarkers in patient management. Here, we discuss the current knowledge and provide translational novel considerations regarding its clinical detection and targeting to improve the outcome of patients with non-small-cell lung carcinoma of all stages.

Abstract

Lung cancer represents the first cause of death by cancer worldwide and remains a challenging public health issue. Hypoxia, as a relevant biomarker, has raised high expectations for clinical practice. Here, we review clinical and pathological features related to hypoxic lung tumours. Secondly, we expound on the main current techniques to evaluate hypoxic status in NSCLC focusing on positive emission tomography. We present existing alternative experimental approaches such as the examination of circulating markers and highlight the interest in non-invasive markers. Finally, we evaluate the relevance of investigating hypoxia in lung cancer management as a companion biomarker at various lung cancer stages. Hypoxia could support the identification of patients with higher risks of NSCLC. Moreover, the presence of hypoxia in treated tumours could help clinicians predict a worse prognosis for patients with resected NSCLC and may help identify patients who would benefit potentially from adjuvant therapies. Globally, the large quantity of translational data incites experimental and clinical studies to implement the characterisation of hypoxia in clinical NSCLC management.

Evolving roles of lysyl oxidase family in tumorigenesis and cancer therapy

The lysyl oxidase (LOX) family is comprised of LOX and four LOX-like proteins (LOXL1, LOXL2, LOXL3, and LOXL4), and mainly functions in the remodeling of extracellular matrix (ECM) and the cross-linking of collagen and elastic fibers. Recently, a growing body of research has demonstrated that LOX family is critically involved in the regulation of cancer cell proliferation, migration, invasion and metastasis. In this review, we discuss the roles of LOX family members in the development and progression of different types of human cancers. Furthermore, we also describe the potential inhibitors of LOX family proteins and highlight that LOX family might be an important therapeutic target for cancer therapy.

Cytochrome P450 Epoxygenase 2J2 Protects Against Lung Ischemia/Reperfusion Injury by Activating the P13K/Akt/GSK-3-β/NF-kB Signaling Pathway During Deep Hypothermic Low Flow in Mice

BACKGROUND

Cytochrome P450 epoxygenase 2J2 (CYP2J2) metabolizes arachidonic acid to epoxyeicosatrienoic acids, which exert anti-inflammatory effects and alleviate oxidative stress in the cardiovascular system. Our previous work revealed that CYP2J2 is expressed in pulmonary artery endothelial cells. It was therefore hypothesized that CYP2J2 overexpression may prevent lung ischemia/reperfusion injury (LIRI) in 3-week-old C57BL/6 mice during deep hypothermic low flow (DHLF). This study aimed to establish whether CYP2J2 protects against LIRI and the mechanisms of CYP2J2 overexpression during DHLF in mice. The aim of this study was to explore the effects of DHLF on lung tissue in mice and to find out the regularity of this process, so as to provide theoretical data for lung tissue protection in children undergoing this process in clinic.

METHODS

A 3-week-old C57BL/6 mouse model was used to mimic LIRI conditions during DHLF by clamping the left pulmonary artery and left main bronchus for 120 min, followed by reperfusion for 2 h. The body temperature of the mice was maintained between 18°C and 19°C to induce DHLF.

RESULTS

During DHLF, lung ischemia/reperfusion increased the left lung wet/dry weight, the left lung weight/body weight ratio, the protein concentration in bronchoalveolar lavage fluid, and the concentration of proinflammatory mediators in the lungs, including interleukin (IL)-1, IL-8, and necrosis factor (NF)-α, and decreased the concentration of the anti-inflammatory mediator IL-10. Furthermore, activation of NF-κB p65 and degradation of IKBα were remarkably increased in lung tissues after ischemia/reperfusion. The CYP2J2 overexpression group showed the opposite results (P < 0.05), and p-Akt1 and p-GSK-3β expression were significantly higher in the CYP2J2 overexpression group (P < 0.05). Moreover, the changes in IL-1, IL-8, tumor necrosis factor-α, IL-10, p-Akt1, p-GSK-3β, NF-κB p65, and IKBα were reversed in the Akt1 gene heterozygous knockout group, and lung damage was significantly higher in the Akt1 gene heterozygous knockout group than in the CYP2J2 overexpression group. CYP2J2 overexpression can protect against LIRI, whereas Akt1 gene heterozygous knockout in mice can abolish this protective effect.

CONCLUSIONS

CYP2J2 overexpression can protect against LIRI by activating the P13K/Akt/GSK-3β/NF-kB signaling pathway during DHLF. Thus, changing CYP2J2 expression can be a novel strategy for the prevention and treatment of LIRI during DHLF.

Comparing progression molecular mechanisms between lung adenocarcinoma and lung squamous cell carcinoma based on genetic and epigenetic networks: big data mining and genome-wide systems identification

Non-small-cell lung cancer (NSCLC) is the predominant type of lung cancer in the world. Lung adenocarcinoma (LADC) and lung squamous cell carcinoma (LSCC) are subtypes of NSCLC. We usually regard them as different disease due to their unique molecular characteristics, distinct cells of origin and dissimilar clinical response. However, the differences of genetic and epigenetic progression mechanism between LADC and LSCC are complicated to analyze. Therefore, we applied systems biology approaches and big databases mining to construct genetic and epigenetic networks (GENs) with next-generation sequencing data of LADC and LSCC. In order to obtain the real GENs, system identification and system order detection are conducted on gene regulatory networks (GRNs) and protein-protein interaction networks (PPINs) for each stage of LADC and LSCC. The core GENs were extracted via principal network projection (PNP). Based on the ranking of projection values, we got the core pathways in respect of KEGG pathway. Compared with the core pathways, we found significant differences between microenvironments, dysregulations of miRNAs, epigenetic modifications on certain signaling transduction proteins and target genes in each stage of LADC and LSCC. Finally, we proposed six genetic and epigenetic multiple-molecule drugs to target essential biomarkers in each progression stage of LADC and LSCC, respectively.

Is mitochondrial dysfunction a driving mechanism linking COPD to nonsmall cell lung carcinoma?

Chronic obstructive pulmonary disease (COPD) patients are at increased risk of developing nonsmall cell lung carcinoma, irrespective of their smoking history. Although the mechanisms behind this observation are not clear, established drivers of carcinogenesis in COPD include oxidative stress and sustained chronic inflammation. Mitochondria are critical in these two processes and recent evidence links increased oxidative stress in COPD patients to mitochondrial damage. We therefore postulate that mitochondrial damage in COPD patients leads to increased oxidative stress and chronic inflammation, thereby increasing the risk of carcinogenesis.

The functional state of the mitochondrion is dependent on the balance between its biogenesis and degradation (mitophagy). Dysfunctional mitochondria are a source of oxidative stress and inflammasome activation. In COPD, there is impaired translocation of the ubiquitin-related degradation molecule Parkin following activation of the Pink1 mitophagy pathway, resulting in excessive dysfunctional mitochondria. We hypothesise that deranged pathways in mitochondrial biogenesis and mitophagy in COPD can account for the increased risk in carcinogenesis. To test this hypothesis, animal models exposed to cigarette smoke and developing emphysema and lung cancer should be developed. In the future, the use of mitochondria-based antioxidants should be studied as an adjunct with the aim of reducing the risk of COPD-associated cancer.

Lipopolysaccharide-induced toll-like receptor 4 signaling in esophageal squamous cell carcinoma promotes tumor proliferation and regulates inflammatory cytokines expression

Emerging evidence suggests toll-like receptor 4 (TLR4) signaling contributes to cancer development and progression. However, the consequences of signaling via the TLR4 pathway in esophageal squamous cell carcinoma (ESCC) are still unclear. Here, we investigated the impact of Lipopolysaccharide (LPS)-induced TLR4 signaling on ESCC cell proliferation, inflammatory cytokines expression, and downstream molecular mechanisms. Seventy-eight ESCC and 26 normal esophageal specimens were analyzed by immunohistochemistry, and two cell lines (Eca-109 and TE-1) were used for in vitro studies. LPS, a natural agonist of TLR4, was used to activate TLR4 signaling. The effects of LPS-TLR4 signaling on cell proliferation and inflammatory cytokines regulation were examined. Specific inhibitors of mitogen-activated protein kinase (MAPK) (extracellular regulated protein kinase [ERK] and p38) signaling pathways were used to investigate the role of each pathway in LPS-TLR4 signaling. TLR4 protein was increased in ESCC tumor tissues compared with the adjacent normal tissues. TLR4 over-expression was significantly correlated with tumor differentiation grade, lymph node metastasis, and UICC stage. LPS-induced activation of TLR4 signaling promoted cancer cell proliferation, increased production of proinflammatory or immunosuppressive cytokines TNF-α, TGF-β and inhibited the anti-inflammatory cytokine IL-10. LPS-TLR4 signaling was associated with the activation of ERK and p38 MAPK signaling pathways. Further inactivation of the two pathways by specific inhibitors attenuated cell proliferation and inflammatory cytokines expression induced by LPS. Our results indicate that LPS-TLR4 signaling in cancer cells contributes to the progression of human ESCC.

Clinicopathological and prognostic significance of hypoxia-inducible factor-1 alpha in lung cancer: a systematic review with meta-analysis

Hypoxia-inducible factor-1 alpha (HIF-1α) plays a vital role in the initiation, evaluation and prognosis in lung cancer. The prognostic value of HIF-1α reported in diverse study remains disputable. Accordingly, a meta-analysis was implemented to further understand the prognostic role of HIF-1α in lung cancer. The relationship between HIF-1α and the clinicopathological characteristics and prognosis of lung cancer were investigated by a meta-analysis. PubMed and Embase were searched from their inception to January 2015 for observational studies. Fixed-effects or random-effects meta-analyses were used to calculate odds ratios and 95% confidence intervals of different comparisons. A total of 20 studies met the criteria. The results showed that HIF-1α expression in lung cancer tissues was significantly higher than that in normal lung tissues. Expression of HIF-1α in patients with squamous cell carcinoma was significantly higher than that of patients with adenocarcinomas. Similarly, non-small cell lung cancer (NSCLC) patients had higher HIF-1α expression than small cell lung cancer (SCLC) patients. Moreover, lymph node metastasized tissues had higher HIF-1α expression than non-lymph node metastasized tissues. A high level HIF-1α expression was well correlated with the expression of vascular endothelial growth factor and epidermal growth factor receptor in the NSCLC. Notably, NSCLC or SCLC patients with positive HIF-1α expression in tumor tissues had lower overall survival rate than patients with negative HIF-1α expression. It was suggested that HIF-1α expression may be a prognostic biomarker and a potential therapeutic target for lung cancer.

Prognostic impact of average iodine density assessed by dual-energy spectral imaging for predicting lung tumor recurrence after stereotactic body radiotherapy

The purpose of this study was to investigate the prognostic significance of average iodine density as assessed by dual-energy computed tomography (DE-CT) for lung tumors treated with stereotactic body radiotherapy (SBRT). From March 2011 to August 2014, 93 medically inoperable patients with 74 primary lung cancers and 19 lung metastases underwent DE-CT prior to SBRT of a total dose of 45-60 Gy in 5-10 fractions. Of these 93 patients, nine patients had two lung tumors. Thus, 102 lung tumors were included in this study. DE-CT was performed for pretreatment evaluation. Regions of interest were set for the entire tumor, and average iodine density was obtained using a dedicated imaging software and evaluated with regard to local control. The median follow-up period was 23.4 months (range, 1.5-54.5 months). The median value of the average iodine density was 1.86 mg/cm(3) (range, 0.40-9.27 mg/cm(3)). Two-year local control rates for the high and low average iodine density groups divided by the median value of the average iodine density were 96.9% and 75.7% (P = 0.006), respectively. Tumors with lower average iodine density showed a worse prognosis, possibly reflecting a hypoxic cell population in the tumor. The average iodine density exhibited a significant impact on local control. Our preliminary results indicate that iodine density evaluated using dual-energy spectral CT may be a useful, noninvasive and quantitative assessment of radio-resistance caused by presumably hypoxic cell populations in tumors.

Hypoxia induced high expression of thioredoxin interacting protein (TXNIP) in non-small cell lung cancer and its prognostic effect

Although associations between thioredoxin interacting protein (TXNIP) and cancers have been recognized, the effects of TXNIP on non-small cell lung cancer (NSCLC) prognosis remained to be determined in detail. In addition, while hypoxia is a key characteristic of tumor cell growth microenvironment, the effect of hypoxia on TXNIP expression is controversial. In this study, formaldehyde fixed and paraffin embedded (FFPE) samples of 70 NSCLC patients who underwent resection between January 2010 and December 2011 were obtained. Evaluation of TXNIP and hypoxia inducible factor-1α (HIF-1α) protein expression in FFPE samples was made by immunohistochemistry. By Kaplan-Meier method, patients with high TXNIP expression demonstrated a significantly shorter progression free survival (PFS) compared with those with low TXNIP expression (18.0 months, 95%CI: 11.7, 24.3 versus 23.0 months, 95%CI: 17.6, 28.4, P=0.02). High TXNIP expression level was also identified as an independent prognostic factor by Cox regression analysis (adjusted hazard ratio: 2.46; 95%CI: 1.08, 5.56; P=0.03). Furthermore, TXNIP expression was found to be significantly correlated with HIF- 1α expression (Spearman correlation=0.67, P=0.000). To further confirm correlations, we established a tumor cell hypoxic culture model. Expression of TXNIP was up-regulated in all three NSCLC cell lines (A549, SPC-A1, and H1299) under hypoxic conditions. This study suggests that hypoxia induces increased TXNIP expression in NSCLC and high TXNIP expression could be a poor prognostic marker.

Lysyl oxidase mediates hypoxia-induced radioresistance in non-small cell lung cancer A549 cells

Hypoxia-induced radioresistance has been well known as the main obstacle in cancer radiotherapy. Lysyl oxidase (LOX) was previously demonstrated to play an important role in hypoxia-induced biological behaviors, such as metastasis and angiogenesis, through hypoxia-inducible factor-1α (HIF-1α), which is an important contributing factor to radioresistance in tumor cells. However, how LOX plays a role in hypoxia-induced radioresistance has yet to be determined. Here, we found that LOX expression was in accordance with HIF-1α expression, and LOX expression at the mRNA and protein level, and enzymatic activity were remarkably upregulated in the hypoxic A549 cells, compared with normoxic A549 cells. Inhibition of LOX resulted in the reduction of the ability to repair double-stranded breaks (DSBs), promotion of apoptosis, relief of G2/M cycle arrest, and eventually reduction of hypoxia-induced radioresistance in the hypoxic A549 cells. This suggests that LOX may play an important role in hypoxia-induced radioresistance. Together, our results might suggest a novel potential therapeutic target in the management of non-small cell lung cancer (NSCLC).

The hypoxic tumor microenvironment: driving the tumorigenesis of non-small-cell lung cancer

Since the application of molecular biology in cancer biology, lung cancer research has classically focused on molecular drivers of disease. One such pathway, the hypoxic response pathway, is activated by reduced local oxygen concentrations at the tumor site. Hypoxia-driven gene and protein changes enhance epithelial-to-mesenchymal transition, remodel the extracellular matrix, drive drug resistance, support cancer stem cells and aid evasion from immune cells. However, it is not the tumor cells alone which drive this response to hypoxia, but rather their interaction with a complex milieu of supporting cells. This review will focus on recent advances in our understanding of how these cells contribute to the tumor response to hypoxia in non-small-cell lung cancer.

Upregulation of HIF-1α by hypoxia protect neuroblastoma cells from apoptosis by promoting survivin expression

Apoptosis is one of main types of neural cell death and is reversible and is a major target of therapeutic interventions. However, detailed apoptotic cascades still need to be recognized. In present study, we determined the promotion of HIF-1α and survivin in brain samples of a mouse model of hypoxic-ischemia and in neuroblastoma SH-SY5Y cells post hypoxia treatment. Then gain-of-function and loss-of-function strategies were adopted to manipulate the HIF-1α in SH-SY5Y cells, and hypoxia-induced survivin upregulation and cell apoptosis were determined. Results demonstrated that the HIF-1α and survivin were significantly promoted in a mouse model of hypoxic-ischemia or in SH-SY5Y cells post hypoxia in vitro. Manually upregulated HIF-1α could promote the hypoxia-induced survivin upregulation and improve the hypoxia-induced SH-SY5Y cell apoptosis. On the other hand, the HIF-1α knockdown by RNAi reduced the hypoxia-induced survivin upregulation and cell apoptosis. Therefore, the present study confirmed the protective role of HIF-1α and survivin in the hypoxia-induced SH- SY5Y cell apoptosis, and the survivin upregulation by hypoxia is HIF-1α-dependent. Promotion of HIF-1α and survivin might be a valuable stragegy for therapeutic intervention for hypoxic-ischemic encephalopathy.

LOX expression and functional analysis in astrocytomas and impact of IDH1 mutation

Lysyl oxidase (LOX) is involved in vital biological processes such as cell motility, cell signaling and gene regulation. Deregulation of this protein can contribute to tumor formation and progression. Although it is known that LOX is involved in invasion, proliferation and tumor migration in other types of tumors, studies of LOX in astrocytomas of different grades are scarce. The purpose of our study was to characterize LOX, BMP1 and HIF1A expression by real-time PCR in astrocytomas with WHO grades I to IV compared to non-neoplastic brain tissue. IDH1 mutational status was determined by PCR and sequencing. LOX protein expression was also analyzed by immunohistochemistry. LOX functional analyses were performed using siRNA knockdown and the specific inhibitor BAPN in two glioblastoma cell lines. The expression levels of LOX, BMP1 and HIF1A were correlated and analyzed according to IDH1 mutation status and to the clinical end-point of overall survival of glioblastoma patients. The results demonstrate that increased expression and activity of LOX, BMP1 and HIF1A were positively correlated with the malignant grade of astrocytomas. LOX protein expression also increased according to the degree of malignancy, with localization in the cytoplasm and nucleus and staining observed in endothelial cells. Glioblastoma with a mutation in IDH1 expressed lower levels of LOX in the nucleus, and IDH1-mutated cases showed lower LOX expression levels when compared to wild-type IDH1 cases. LOX knockdown and inhibition by BAPN in U87MG and A172 cell lines affected migration, invasion and soft agar colony formation. Taken together, these results corroborate the role of LOX in the migration, invasion and angiogenesis of astrocytomas. Furthermore, LOX expression is influenced by IDH1 mutational status. This work provides new insights for researchers aiming to design targeted therapies to control astrocytomas.

Correlation between tumor size and blood volume in lung tumors: a prospective study on dual-energy gemstone spectral CT imaging

The purpose of this study was to investigate the relationship between tumor size and blood volume for patients with lung tumors, using dual-energy computed tomography (DECT) and a gemstone spectral imaging (GSI) viewer. During the period from March 2011 to March 2013, 50 patients with 57 medically inoperable lung tumors underwent DECT before stereotactic body radiotherapy (SBRT) of 50-60 Gy in 5-6 fractions. DECT was taken for pretreatment evaluation. The region-of-interest for a given spatial placement of the tumors was set, and averages for CT value, water density and iodine density were compared with tumor size. The average values for iodine density in tumors of ≤ 2 cm, 2-3 cm, and >3 cm maximum diameter were 24.7, 19.6 and 16.0 (100 µg/cm(3)), respectively. The average value of the iodine density was significantly lower in larger tumors. No significant correlation was detected between tumor size and average CT value or between tumor size and average water density. Both the average water density and the average CT value were affected by the amount of air in the tumor, but the average iodine density was not affected by air in the tumor. The average water density and the average CT value were significantly correlated, but the average iodine density and the average CT value showed no significant correlation. The blood volume of tumors can be indicated by the average iodine density more accurately than it can by the average CT value. The average iodine density as assessed by DECT might be a non-invasive and quantitative assessment of the radio-resistance ascribable to the hypoxic cell population in a tumor.

miR-138-5p reverses gefitinib resistance in non-small cell lung cancer cells via negatively regulating G protein-coupled receptor 124

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR TKIs) such as gefitinib are clinically effective treatments for non-small cell lung cancer (NSCLC) patients with EGFR activating mutations. However, therapeutic effect is ultimately limited by the development of acquired TKI resistance. MicroRNAs (miRNAs) represent a category of small non-coding RNAs commonly deregulated in human malignancies. The aim of this study was to investigate the role of miRNAs in gefitinib resistance. We established a gefitinib-resistant cell model (PC9GR) by continually exposing PC9 NSCLC cells to gefitinib for 6 months. MiRNA microarray screening revealed miR-138-5p showed the greatest downregulation in PC9GR cells. Re-expression of miR-138-5p was sufficient to sensitize PC9GR cells and another gefitinib-resistant NSCLC cell line, H1975, to gefitinib. Bioinformatics analysis and luciferase reporter assay showed that G protein-coupled receptor124 (GPR124) was a direct target of miR-138-5p. Experimental validation demonstrated that expression of GPR124 was suppressed by miR-138-5p on protein and mRNA levels in NSCLC cells. Furthermore, we observed an inverse correlation between the expression of miR-138-5p and GPR124 in lung adenocarcinoma specimens. Knockdown of GPR124 mimicked the effects of miR-138-5p on the sensitivity to gefitinib. Collectively, our results suggest that downregulation of miR-138-5p contributes to gefitinib resistance and that restoration of miR-138-5p or inhibition GPR124 might serve as potential therapeutic approach for overcoming NSCLC gefitinib resistance.