LOXL3 Silencing Affected Cell Adhesion and Invasion in U87MG Glioma Cells.

Talita De S Laurentino,Roseli Da S Soares,Antonio M Lerario,Sueli M Oba-Shinjo,Suely K N Marie

doi:10.3390/ijms22158072

Abstract

Lysyl oxidase-like 3 (LOXL3), belonging to the lysyl oxidase family, is responsible for the crosslinking in collagen or elastin. The cellular localization of LOXL3 is in the extracellular space by reason of its canonical function. In tumors, the presence of LOXL3 has been associated with genomic stability, cell proliferation, and metastasis. In silico analysis has shown that glioblastoma was among tumors with the highest LOXL3 expression levels. LOXL3 silencing of U87MG cells by siRNA led to the spreading of the tumor cell surface, and the transcriptome analysis of these cells revealed an upregulation of genes coding for extracellular matrix, cell adhesion, and cytoskeleton components, convergent to an increase in cell adhesion and a decrease in cell invasion observed in functional assays. Significant correlations of LOXL3 expression with genes coding for tubulins were observed in the mesenchymal subtype in the TCGA RNA-seq dataset of glioblastoma (GBM). Conversely, genes involved in endocytosis and lysosome formation, along with MAPK-binding proteins related to focal adhesion turnover, were downregulated, which may corroborate the observed decrease in cell viability and increase in the rate of cell death. Invasiveness is a major determinant of the recurrence and poor outcome of GBM patients, and downregulation of LOXL3 may contribute to halting the tumor cell invasion.

Highlights

Glioblastoma (GBM), the most aggressive and common type of malignant brain tumor [1], is characterized by rapid growth and invasion, neovascularization, and necrosis [2]
High Lysyl oxidase-like 3 (LOXL3) expression levels were detected in 10 types of cancer, including GBM (Figure 1A, in red)
The cell lines derived from gliomas (U138MG and U87MG) were in the top five cell lines presenting the highest LOXL3 expression levels among the 64 human cell lines of the Human Protein Atlas (HPA) study (Figure 1B)

Summary

Introduction

Glioblastoma (GBM), the most aggressive and common type of malignant brain tumor [1], is characterized by rapid growth and invasion, neovascularization, and necrosis [2]. In 2016, the World Health Organization restructured the classification of central nervous system tumors, dividing astrocytomas into two groups: diffuse astrocytic tumors (including GBM) and other astrocytic tumors. Molecular features, including isocitrate dehydrogenase (NADP(+)) 1/2 (IDH1/2) mutations, have been incorporated into the classification of gliomas [3]. In addition to the World Health Organization classification, The Cancer Genome Atlas (TCGA) network presented the genetic signatures of GBM. GBMs were subdivided into classical, mesenchymal, and proneural molecular subtypes [4,5]. Maximal tumor resection, followed by radiotherapy and chemotherapy with temozolomide (TMZ), is currently the standard treatment for patients with GBM. A high recurrence rate and resistance to TMZ frequently occur in patients with GBM, resulting in a median overall survival of 15 months [6]

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