Comparative studies of TIMP-1 immunohistochemistry, TIMP-1 FISH analysis and plasma TIMP-1 in glioblastoma patients

Identification of novel drug resistance mechanisms by genomic and transcriptomic profiling of glioblastoma cells with mutation-activated EGFR

AIMS

Epidermal growth factor receptor (EGFR) is not only involved in carcinogenesis, but also in chemoresistance. We characterized U87.MGΔEGFR glioblastoma cells with constitutively active EGFR due to deletion at the ligand binding domain in terms of gene expression profiling and chromosomal aberrations. Wild-type U87.MG cells served as control.

MATERIALS AND METHODS

RNA sequencing and network analyses (Ingenuity Pathway Analysis) were performed to identify novel drug resistance mechanisms related to expression of mutation activated EGFR. Chromosomal aberrations were characterized by multicolor fluorescence in situ hybridization (mFISH) and array comparative genomic hybridization (aCGH).

KEY FINDINGS

U87.MGΔEGFR cells presented much more chromosomal aberrations, amplifications and deletions than wild-type U87.MG cells. Still, both cell lines were near-triploid. Numerous genes were overexpressed in U87.MGΔEGFR cells, some of which have been already linked to drug resistance. PXDN, which is associated with epithelial mesenchymal transition, was the most upregulated gene (901.8-fold). TENM1 was 331.6-fold upregulated, and it was previously reported to modulate neural development. EGFR-AS1 (161.2-fold upregulated) has been reported to increase the EGFR mRNA stability and its expression - in accordance with that of EGFR - was upregulated (85.5-fold). In addition to well-known resistance genes, numerous novel genes and genomic aberrations were identified. ANGPT2 upregulation and CPM downregulation were validated by Western blotting.

SIGNIFICANCE

Transcriptomics and genomics analyses in U87.MGΔEGFR cells unraveled a range of novel drug resistance mechanisms including apoptosis, DNA repair, ferroptosis, glutathione related gene activities, heat shock, oxidative stress, transcription factor activities, which may have important implications for future treatment strategies.

Glioblastoma: Is There Any Blood Biomarker with True Clinical Relevance?

Glioblastoma (GBM) is the most frequent malignant primary brain tumor in adults, characterized by a highly aggressive, inflammatory and angiogenic phenotype. It is a remarkably heterogeneous tumor at several levels, including histopathologically, radiographically and genetically. The 2016 update of the WHO Classification of Tumours of the Central Nervous System highlighted molecular parameters as paramount features for the diagnosis, namely IDH1/2 mutations that distinguish primary and secondary GBM. An ideal biomarker is a molecule that can be detected/quantified through simple non- or minimally invasive methods with the potential to assess cancer risk; promote early diagnosis; increase grading accuracy; and monitor disease evolution and treatment response, as well as fundamentally being restricted to one aspect. Blood-based biomarkers are particularly attractive due to their easy access and have been widely used for various cancer types. A number of serum biomarkers with multiple utilities for glioma have been reported that could classify glioma grades more precisely and provide prognostic value among these patients. At present, screening for gliomas has no clinical relevance. This is because of the low incidence, the lack of sensitive biomarkers in plasma, and the observation that gliomas may develop apparently de novo within few weeks or months. To the best of our knowledge, there is no routine use of a serum biomarker for clinical follow-up. The purpose of this paper is to review the serum biomarkers described in the literature related to glioblastoma and their possible relationship with clinical features.

Current and emerging biomarkers in tumors of the central nervous system: Possible diagnostic, prognostic and therapeutic applications

Recent investments in research associated with the discovery of specific tumor biomarkers important for efficient diagnosis and prognosis are beginning to bear fruit. Key biomarkers could potentially outweigh traditional radiological or pathological methods by enabling specificity of early detection, when coupled with tumor molecular profiling and clinical associations. Only few biomarkers are approved by regulatory authorities for Central Nervous System Tumors (CNSTs), despite the evaluation of a large number of CNST related markers during clinical trials. Traditional CNSTs biomarkers include 1p/19q co-deletion, O6-Methylguanine-DNA Methyltransferase Methylation, and mutations in IDH1/IDH2. Recently tested CNSTs biomarkers include VEGFR-2, EGFRvIII, IL2, PDGFR, MMPs, BRAF, STAT3, PTEN, TERT, AKT, NF2, and BCL2. Additional studies have highlighted new and novel MicroRNAs, circular RNAs and long non-coding RNAs as promising biomarkers. Studies on microvesicles pinpoint exosomes as promising, less invasive biomarkers that could be isolated from the serum of cancer patients. Furthermore, Cancer Stem Cells (CSCs) related molecules, such as CD133, SOX2 and Nestin, utilized as CNST biomarkers, might enable efficient monitoring of cancer progression, and/or surveillance of emerging drug resistant cells. Approved protocols that implement novel molecular markers in diagnostics, prognostics and drug development will herald a new era of precision and personalized neuro-oncology. This review summarizes and discusses putative CNST biomarkers that are under clinical development, and are ready to move into diagnostic, prognostic and therapeutic applications. Data presented here is predicted to aid in streamlining the process of biomarker's research and development.