Bone morphogenetic protein 7 sensitizes O6-methylguanine methyltransferase expressing-glioblastoma stem cells to clinically relevant dose of temozolomide

Abstract

BackgroundTemozolomide (TMZ) is an oral DNA-alkylating agent used for treating patients with glioblastoma. However, therapeutic benefits of TMZ can be compromised by the expression of O6-methylguanine methyltransferase (MGMT) in tumor tissue. Here we used MGMT-expressing glioblastoma stem cells (GSC) lines as a model for investigating the molecular mechanism underlying TMZ resistance, while aiming to explore a new treatment strategy designed to possibly overcome resistance to the clinically relevant dose of TMZ (35 μM).MethodsMGMT-expressing GSC cultures are resistant to TMZ, and IC50 (half maximal inhibitory concentration) is estimated at around 500 μM. Clonogenic GSC surviving 500 μM TMZ (GSC-500 μM TMZ), were isolated. Molecular signatures were identified via comparative analysis of expression microarray against parental GSC (GSC-parental). The recombinant protein of top downregulated signature was used as a single agent or in combination with TMZ, for evaluating therapeutic effects of treatment of GSC.ResultsThe molecular signatures characterized an activation of protective stress responses in GSC-500 μM TMZ, mainly including biotransformation/detoxification of xenobiotics, blocked endoplasmic reticulum stress-mediated apoptosis, epithelial-to-mesenchymal transition (EMT), and inhibited growth/differentiation. Bone morphogenetic protein 7 (BMP7) was identified as the top down-regulated gene in GSC-500 μM TMZ. Although augmenting BMP7 signaling in GSC by exogenous BMP7 treatment did not effectively stop GSC growth, it markedly sensitized both GSC-500 μM TMZ and GSC-parental to 35 μM TMZ treatment, leading to loss of self-renewal and migration capacity. BMP7 treatment induced senescence of GSC cultures and suppressed mRNA expression of CD133, MGMT, and ATP-binding cassette drug efflux transporters (ABCB1, ABCG2), as well as reconfigured transcriptional profiles in GSC by downregulating genes associated with EMT/migration/invasion, stemness, inflammation/immune response, and cell proliferation/tumorigenesis. BMP7 treatment significantly prolonged survival time of animals intracranially inoculated with GSC when compared to those untreated or treated with TMZ alone (p = 0.0017), whereas combination of two agents further extended animal survival compared to BMP7 alone (p = 0.0489).ConclusionsThese data support the view that reduced endogenous BMP7 expression/signaling in GSC may contribute to maintained stemness, EMT, and chemoresistant phenotype, suggesting that BMP7 treatment may provide a novel strategy in combination with TMZ for an effective treatment of glioblastoma exhibiting unmethylated MGMT.Electronic supplementary materialThe online version of this article (doi:10.1186/s12943-015-0459-1) contains supplementary material, which is available to authorized users.

Combined elevation of TRIB2 and MAP3K1 indicates poor prognosis and chemoresistance to temozolomide in glioblastoma

“…To thoroughly explore the potential prognostic biomarkers for glioma, kinome‐wide hierarchical bi‐clustering was performed using previously published microarray databases related to TMZ resistance, World Health Organization (WHO) grade, and radiotherapeutic resistance (Tso et al, 2015; Mao et al, 2015 and Wang et al, 2017). The differentially expressed genes were sorted by their fold changes (Figure A‐C, and Tables S1‐S3).…”

“…A, Kinome‐wide microarray analysis for 668 kinase‐encoding genes in GBM neurosphere compared with the nontumor (Mao et al, 2015). B, Kinome‐wide microarray analysis for 668 kinase‐encoding genes in TMZ‐resistant glioma cell lines compared with the nontreated cells (Tso et al, 2015). C, Kinome‐wide microarray analysis for 668 kinase‐encoding genes in radiation‐treated glioma cell lines (IR) compared with the nontreated cells (Wang et al, 2017).…”

“…To thoroughly explore the potential prognostic biomarkers for glioma, kinome-wide hierarchical bi-clustering was performed using Figure 1A-C, and Tables S1-S3). The genes that were more than 1.5-fold upregulated were selected from Tso et al 21 and Mao et al 20 Moreover, genes that were upregulated by 0.2-fold were extracted from the Wang et al 22 database. The overlapping genes from those three gene lists are summarized.…”

Mesenchymal/proangiogenic factor YKL-40 related to glioblastomas and its relationship with the subventricular zone

“…Furthermore, some investigators observe that GSCs give rise to endothelial cells (ECs)60, as shown in Figure 1, and induce changes in vascular niches, characterized by the sprouting of new blood vessels, consisting of an abundant, leaky and highly disorganized "glomeruloid" vascular network through the cooperative secretion of pro-angiogenic factors [1,61,67], such as VEGF, IL-8 and YKL-40 [2,29,56], highly different in patients with the same tumor [42,56,60,82]. YKL-40, also known as chitinase-like protein 1 or human cartilage glycoprotein-39 [6], is a highly conserved glycoprotein that belongs to the glycosyl hydrolase family 18 with no chitinolytic activity [7,84], included as a mesenchymal marker overexpressed in GB and postulated as one of the most promising predictive serum markers since it was found to have elevated levels in the serum of patients with GB [6,29,31,32,35].…”

Tyrosine kinase Eph receptor A6 sensitizes glioma‐initiating cells towards bone morphogenetic protein‐induced apoptosis

“…5 The BMP family of growth factors has been proposed as potential non-cytotoxic therapeutic agents for inhibiting the growth of GIC by inducing differentiation 6 and sensitization to temozolomide. 7 BMP signaling promotes the differentiation of GIC by BMP type I receptors and the intracellular signaling pathway. 8,9 Moreover, our previous study showed that BMP-4 and BMP-7 induce apoptosis by activating the BMP type I receptor ALK-2.…”