Differential expression of LOXL4 in normal and tumour tissue samples of laryngeal squamous cell carcinoma

The possibilities of LOXL4 as a prognostic marker for carcinomas

Lysyl oxidase-like 4 (LOXL4), a member of lysyl oxidase family, is a copper and lysine tyrosylquinone-dependent amine oxidase that serves the role of catalyzing the cross-linking of elastin and collagen in the extracellular matrix. Numerous studies have shown a significant association between LOXL4 expression levels and tumor proliferation, migration, invasion and patients' prognosis and overall survival in different types of tumors. Here we review their relationship and the molecular pathogenesis behind them, aiming to explore the possibilities of LOXL4 as a prognostic marker for diverse carcinomas and provide some indications for further research in this field.

Long non-coding RNA AGAP2-AS1 promotes cell proliferation and invasion through regulating miR-193a-3p/LOXL4 axis in laryngeal squamous cell carcinoma

Laryngeal squamous cell carcinoma (LSCC) is an aggressive malignancy with highly mortality rate. Long non-coding RNA (lncRNA) AGAP2-AS1 is an identified oncogene in several types of cancers. However, the role of AGAP2-AS1 in LSCC remains unclear. The expression levels of AGAP2-AS1 in LSCC tissues and cell lines were measured using qRT-PCR. AGAP2-AS1 was knocked down in LSCC cells through transfection with siRNA-AGAP2-AS1. Cell proliferation and invasion were detected using MTT and transwell assays. Dual-luciferase reporter gene assay was performed to confirm the interaction with AGAP2-AS1 and downstream genes. Our results showed that AGAP2-AS1 expression was remarkably increased in human LSCC tissues and cell lines. Knockdown of AGAP2-AS1 significantly inhibited the proliferation and invasion of LSCC cells. In addition, AGAP2-AS1 sponged miR-193a-3p and regulated its expression in LSCC cells. Inhibition of miR-193a-3p reversed the effects of AGAP2-AS1 knockdown on LSCC cells. Furthermore, Lysyl oxidase-like 4 (LOXL4) was a target gene of miR-193a-3p and the role of miR-193a-3p was mediated by LOXL4. In conclusion, these findings suggest that knockdown of AGAP2-AS1 inhibited the proliferation and invasion of LSCC cells through regulating the miR-193a-3p/LOXL4 axis.

Lysyl Oxidase Like-4 (LOXL4) as a tumor marker and prognosticator in advanced stage laryngeal cancer

Introduction

Lysyl oxidase-like 4 is an amine oxidase from the lysyl oxidase family that was previously shown to be overexpressed in head and neck cancer and upregulated in response to hypoxia. The possible role of lysyl oxidase-like 4 as a tumor marker in advanced stage larynx cancer was investigated.

Objective

To investigate the expression of lysyl Oxidase-Like 4 protein in advanced stage laryngeal cancer and elucidate its possible role as a tumor marker, predictor of treatment response and prognosticator.

Methods

Diagnostic specimens of 72 patients treated for stage III–IV laryngeal squamous cell carcinoma were evaluated for lysyl oxidase-like 4 expression by immunohistochemistry.

Results

Lysyl oxidase-like 4 expression was correlated with advanced tumor stage (p = 0.041) and better differentiation (p = 0.025) but was independent of tumor diameter (p = 0.456). Response to induction chemotherapy or the need for salvage laryngectomy were not affected by lysyl oxidase-like 4 expression (p = 0.999, p = 0.070 respectively). Increased lysyl oxidase-like 4 expression was associated with better 2 year overall survival in both univariate (p = 0.036) and multivariate analyses (p = 0.014).

Conclusion

Lysyl oxidase-like 4 expression emerges with advancing stages, is lost with worsening differentiation, and may have tumor suppressive properties in larynx cancer.

Transcriptome network of the papillary thyroid carcinoma radiation marker CLIP2

Background

We present a functional gene association network of the CLIP2 gene, generated by de-novo reconstruction from transcriptomic microarray data. CLIP2 was previously identified as a potential marker for radiation induced papillary thyroid carcinoma (PTC) of young patients in the aftermath of the Chernobyl reactor accident. Considering the rising thyroid cancer incidence rates in western societies, potentially related to medical radiation exposure, the functional characterization of CLIP2 is of relevance and contributes to the knowledge about radiation-induced thyroid malignancies.

Methods

We generated a transcriptomic mRNA expression data set from a CLIP2-perturbed thyroid cancer cell line (TPC-1) with induced CLIP2 mRNA overexpression and siRNA knockdown, respectively, followed by gene-association network reconstruction using the partial correlation-based approach GeneNet. Furthermore, we investigated different approaches for prioritizing differentially expressed genes for network reconstruction and compared the resulting networks with existing functional interaction networks from the Reactome, Biogrid and STRING databases. The derived CLIP2 interaction partners were validated on transcript and protein level.

Results

The best reconstructed network with regard to selection parameters contained a set of 20 genes in the 1st neighborhood of CLIP2 and suggests involvement of CLIP2 in the biological processes DNA repair/maintenance, chromosomal instability, promotion of proliferation and metastasis. Peptidylprolyl Isomerase Like 3 (PPIL3), previously identified as a potential direct interaction partner of CLIP2, was confirmed in this study by co-expression at the transcript and protein level.

Conclusion

In our study we present an optimized preselection approach for genes subjected to gene-association network reconstruction, which was applied to CLIP2 perturbation transcriptome data of a thyroid cancer cell culture model. Our data support the potential carcinogenic role of CLIP2 overexpression in radiation-induced PTC and further suggest potential interaction partners of the gene.

Clinical significance of LOXL4 expression and features of LOXL4-associated protein-protein interaction network in esophageal squamous cell carcinoma

Lysyl oxidase-like 4 (LOXL4), a member of the LOX family proteins, catalyzes oxidative deamination of lysine residues in collagen and elastin, which are responsible for maintaining extracellular matrix homeostasis. In this study, the mRNA expression of LOXL4 in seven esophageal squamous cell carcinoma (ESCC) cell lines and 15 ESCC pairs of clinical samples were examined. Furthermore, LOXL4 protein levels in the ESCC cell lines were determined using western blotting. With the use of immunofluorescence, LOXL4 was observed to be localized primarily in the cytoplasm, but was also present in the nucleus. In addition, the results indicated that the upregulated expression of LOXL4 was associated with poor survival in patients with ESCC even following curative resection (P = 0.010). Similar Kaplan-Meier estimator curves for proteins that interact with LOXL4, SUV39H1 (P = 0.014) and COL2A1 (P = 0.011), were plotted. The analyses based on the protein-protein interaction network depicted the expression of LOXL4 and its associated proteins as well as their functions, suggesting that LOXL4 and its associated proteins may serve a significant role in the development and progression of ESCC. In conclusion, the results of the present study suggest that LOXL4 is a potential biomarker for patients with ESCC, as well as SUV39H1 and COL2A1, and high expression levels of these genes are associated with poor prognosis in patients with ESCC.

Lysyl Oxidase Isoforms and Potential Therapeutic Opportunities for Fibrosis and Cancer

INTRODUCTION

The lysyl oxidase family of enzymes is classically known as being required for connective tissue maturation by oxidizing lysine residues in elastin and lysine and hydroxylysine residues in collagen precursors. The resulting aldehydes then participate in cross-link formation, which is required for normal connective tissue integrity. These enzymes have biological functions that extend beyond this fundamental biosynthetic role, with contributions to angiogenesis, cell proliferation, and cell differentiation. Dysregulation of lysyl oxidases occurs in multiple pathologies including fibrosis, primary and metastatic cancers, and complications of diabetes in a variety of tissues.

AREAS COVERED

This review summarizes the major findings of novel roles for lysyl oxidases in pathologies, and highlights some of the potential therapeutic approaches that are in development and which stem from these new findings.

EXPERT OPINION

Fundamental questions remain regarding the mechanisms of novel biological functions of this family of proteins, and regarding functions that are independent of their catalytic enzyme activity. However, progress is underway in the development of isoform-specific pharmacologic inhibitors, potential therapeutic antibodies and gaining an increased understanding of both tumor suppressor and metastasis promotion activities. Ultimately, this is likely to lead to novel therapeutic agents.