Elsevier

Neuroscience Letters

Volume 657, 14 September 2017, Pages 77-83
Neuroscience Letters

Research article
FERMT3 contributes to glioblastoma cell proliferation and chemoresistance to temozolomide through integrin mediated Wnt signaling

https://doi.org/10.1016/j.neulet.2017.07.057Get rights and content

Highlights

  • Upregulation of FERMT3 in glioma.

  • Knockdown of FERMT3 suppresses proliferation of glioma cells.

  • Knockdown of FERMT3 inhibits chemoresistance of glioma cells.

  • FERMT3 functions through integrin-mediated Wnt signaling.

Abstract

FERMT3, also known as kindlin-3, is one of three kindlin family members expressed in mammals. Kindlins are cytosolic, adaptor proteins that are important activators and regulators of integrin function. They have also been shown to play critical roles in the development and progression of various cancers. In the present study, we hypothesized that FERMT3 would enhance glioblastoma multiforme (GBM) cell survival. Indeed, expression level analyses showed significant FERMT3 upregulation in human glioma tissues as compared to normal brain tissues. The effect was particularly pronounced in high-grade gliomas. We then demonstrated that FERMT3 knockdown suppresses glioma cell proliferation and chemoresistance to temozolomide (TMZ). To determine the mechanism by which FERMT3 enhances glioma cell proliferation and chemoresistance, we examined the effects of FERMT3 on integrin activation and Wnt/β-catenin signaling. Through the use of western blot assays and TOPflash and FOPflash plasmid transfection into glioma cells lines, we demonstrated that FERMT3 regulates glioma cell activity through integrin-mediated Wnt/β-catenin signaling. These results suggest that FERMT3 activates integrin activity in high-grade gliomas to enhance glioma cell survival and chemoresistance. The present study thus indicates a potential role for FERMT3 as a genetic target in the treatment of GBM.

Introduction

Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor [3]. Despite clinical advances, its prognosis remains very poor, with a median progression-free survival of less than one year at the time of diagnosis [4], [37], [41]. Standard therapy consists of surgical resection followed by radiotherapy and chemotherapy, most often temozolomide (TMZ) [38], [40]. Despite the survival benefits associated with adjuvant radiation and chemotherapy, the majority of patients suffer recurrences of GBM [1]. The main barriers to successful treatment are the invasiveness and chemoresistance of high-grade gliomas [11], [26]. To overcome these barriers, it is crucial to identify the molecular mechanisms that regulate glioma progression. In the present study, we have identified the kindlin family member FERMT3 as one such regulator, as well as its mechanism of action for causing the growth and treatment resistance observed clinically.

Kindlins are cytosolic, adaptor proteins that are important activators and regulators of integrin function, including signaling [2], [23], [29]. They are essential components of the integrin adhesion complex that act through direct binding of β integrin tails [13], [21], [24]. Kindlins have become prominent in recent basic science research largely because of their roles in the development, progression, or suppression of various malignancies, including lung cancer [42], colorectal cancer [31], and gliomas [28], among many others [30]. It has also been shown that kindlins function as cancer therapeutic targets for agents such as docetaxel and cisplatin [34]. FERMT3, also known as kindlin-3, is expressed largely in the hematopoietic system, whereby it regulates activities such as hemostasis and thrombosis [27]. It is unclear whether FERMT3 acts primarily as a tumor promoter or suppressor, and it is likely that its role depends in part on the physiological context of its expression [8], [35]. FERMT3′s role in gliomas has not yet been explored, but recent research has shown that kindlin-2 (FERMT2) acts through the β-catenin/YB-1/EGFR pathway to enhance glioma progression [28]. Given the evidence that FERMT3 is crucial for integrin signaling and that kindlins can regulate cancer progression, we hypothesized that FERMT3 enhances glioma growth and survival through integrin activation of downstream pathways.

Integrins are cell adhesion molecules composed of α and β subunits that mediate interactions between intracellular and extracellular environments, including the surfaces of other cells, extracellular matrices, and pathogens [12], [17]. Extracellularly, they bind ligands, and intracellularly they bind cytoskeletal components and signaling molecules [12], [32]. They act through downstream signaling pathways to regulate numerous physiological processes that are crucial to the survival of individual cells as well as of the organism, such as mitochondrial function [39], immune system activity [36], and angiogenesis [20]. Specifically, they can function in coordination with growth factor receptors to increase β-catenin-dependent transcription and Wnt signaling [5]. However, through such mechanisms, integrins also contribute to pathological processes, including the progression of a variety of cancers [10], [19]. Targeting integrins has recently been shown to effectively treat malignant gliomas in vivo [33]. Furthermore, targeting β-1 integrin is effective in enhancing chemotherapeutic activity [18]. Results such as these suggest an emerging role for integrins in the pathophysiology and treatment of high-grade gliomas.

Section snippets

Glioma tissues

Fresh tumor tissues were obtained from 44 glioma patients during surgery at Daqing Oilfield General Hospital. The selected glioma specimens were immediately frozen in liquid nitrogen and stored at −80 °C for mRNA and protein extraction. The histopathological diagnoses were based on the World Health Organization (WHO) criteria. None of the glioma patients had received chemotherapy or radiotherapy prior to surgery. The present study was approved by the Ethics Committee of Daqing Oilfield General

Upregulation of FERMT3 in glioma

To evaluate the dysregulation of FERMT3 in gliomas, we examined FERMT3 expression levels in a panel of 49 glioma tissues, including eight oligodendrogliomas, six anaplastic oligoastrocytomas, 30 glioblastomas, four astrocytic tumors and one glioneural neoplasm from the published microarray GDS1813. As shown in Fig. 1A, expression of FERMT3 was remarkably increased in glioma tissues, as compared with four normal brain tissues (p < 0.001). We then collected 44 different grades of glioma tissue,

Discussion

Despite substantial advances in surgical and chemotherapeutic treatments of high-grade gliomas, patients with high-grade gliomas still have poor clinical outcomes. The barriers to successful treatment are caused largely by glioma invasion, recurrence, and chemoresistance [1], [3], [4], [11], [26], [37], [38], [40], [41]. In addition to overcoming these barriers, for optimal high-grade glioma treatment, it is also necessary to identify predictive biomarkers [25], [26]. There is ample evidence

Conflicts of interest

The authors declared that there is no conflict of interest regarding the publication of this article.

Acknowledgement

None.

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    These authors contributed equally to this work.

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