ABSTRACT
Glioblastomas (GBM) are heterogeneous highly vascular brain tumors exploiting the unique microenvironment in the brain to resist treatment and anti-tumor responses. Anti-angiogenic agents, immunotherapy, and targeted therapy have been studied extensively in GBM patients over a number of decades with minimal success. Despite maximal efforts, prognosis remains dismal with an overall survival of approximately 15 months.Bevacizumab, a humanized anti-vascular endothelial growth factor (VEGF) antibody, underwent accelerated approval by the U.S. Food and Drug Administration in 2009 for the treatment of recurrent GBM based on promising preclinical and early clinical studies. Unfortunately, subsequent clinical trials did not find overall survival benefit. Pursuing pleiotropic targets and leaning toward multitarget strategies may be a key to more effective therapeutic intervention in GBM, but preclinical evaluation requires careful consideration of model choices. In this study, we discuss bevacizumab resistance, dual targeting of pro-angiogenic modulators VEGF and YKL-40 in the context of brain tumor microenvironment, and how model choice impacts study conclusions and its translational significance.
Subject(s)
Bevacizumab/administration & dosage , Brain Neoplasms/drug therapy , Chitinase-3-Like Protein 1/antagonists & inhibitors , Drug Delivery Systems/methods , Glioblastoma/drug therapy , Vascular Endothelial Growth Factor A/antagonists & inhibitors , Animals , Antineoplastic Agents, Immunological/administration & dosage , Brain Neoplasms/metabolism , Chitinase-3-Like Protein 1/metabolism , Drug Resistance, Neoplasm/drug effects , Drug Resistance, Neoplasm/physiology , Glioblastoma/metabolism , Humans , Mice , Mice, Inbred NOD , Tumor Microenvironment/drug effects , Tumor Microenvironment/physiology , Vascular Endothelial Growth Factor A/metabolism , Xenograft Model Antitumor Assays/methodsABSTRACT
Glioblastoma cancer-stem like cells (GSCs) display marked resistance to ionizing radiation (IR), a standard of care for glioblastoma patients. Mechanisms underpinning radio-resistance of GSCs remain largely unknown. Chromatin state and the accessibility of DNA lesions to DNA repair machineries are crucial for the maintenance of genomic stability. Understanding the functional impact of chromatin remodeling on DNA repair in GSCs may lay the foundation for advancing the efficacy of radio-sensitizing therapies. Here, we present the results of a high-content siRNA microscopy screen, revealing the transcriptional elongation factor SPT6 to be critical for the genomic stability and self-renewal of GSCs. Mechanistically, SPT6 transcriptionally up-regulates BRCA1 and thereby drives an error-free DNA repair in GSCs. SPT6 loss impairs the self-renewal, genomic stability and tumor initiating capacity of GSCs. Collectively, our results provide mechanistic insights into how SPT6 regulates DNA repair and identify SPT6 as a putative therapeutic target in glioblastoma.
Subject(s)
DNA Repair , Genomic Instability , Glioblastoma/genetics , Neoplastic Stem Cells , Transcription Factors/genetics , Transcription Factors/metabolism , Animals , Apoptosis , BRCA1 Protein , Brain Neoplasms/genetics , Cell Cycle Checkpoints , Cell Line, Tumor , Female , Gene Expression Regulation, Neoplastic , Gene Knockdown Techniques , Gene Silencing , Glioblastoma/pathology , HEK293 Cells , Heterografts , Humans , Mice , Mice, Inbred BALB C , Neoplastic Stem Cells/pathology , RNA, Small Interfering/genetics , Radiation Tolerance , Radiation, Ionizing , TranscriptomeABSTRACT
Glioblastoma (GBM) ranks among the most lethal cancers, with current therapies offering only palliation. Inter- and intrapatient heterogeneity is a hallmark of GBM, with epigenetically distinct cancer stem-like cells (CSCs) at the apex. Targeting GSCs remains a challenging task because of their unique biology, resemblance to normal neural stem/progenitor cells, and resistance to standard cytotoxic therapy. Here, we find that the chromatin regulator, JmjC domain histone H3K36me2/me1 demethylase KDM2B, is highly expressed in glioblastoma surgical specimens compared to normal brain. Targeting KDM2B function genetically or pharmacologically impaired the survival of patient-derived primary glioblastoma cells through the induction of DNA damage and apoptosis, sensitizing them to chemotherapy. KDM2B loss decreased the GSC pool, which was potentiated by coadministration of chemotherapy. Collectively, our results demonstrate KDM2B is crucial for glioblastoma maintenance, with inhibition causing loss of GSC survival, genomic stability, and chemoresistance.
Subject(s)
Antineoplastic Agents/administration & dosage , Brain Neoplasms/drug therapy , Drug Resistance, Neoplasm , F-Box Proteins/metabolism , Glioblastoma/drug therapy , Jumonji Domain-Containing Histone Demethylases/metabolism , Neoplastic Stem Cells/metabolism , Apoptosis/drug effects , Astrocytes/metabolism , Brain Neoplasms/pathology , Cell Line , DNA Damage/drug effects , Etoposide/administration & dosage , F-Box Proteins/genetics , Glioblastoma/pathology , Histones/metabolism , Humans , Jumonji Domain-Containing Histone Demethylases/genetics , Lomustine/administration & dosage , Lysine/metabolism , Primary Cell CultureABSTRACT
A key task in developing the field of personalized cancer therapy is the identification of novel molecular targets that enable treatment of cancers not susceptible to other means of specific therapy. The collagen receptor uPARAP/Endo180 is overexpressed by malignant cells in several non-epithelial cancers, notably including sarcomas, glioblastomas and subsets of acute myeloid leukemia. In contrast, in healthy adult individuals, expression is restricted to minor subsets of mesenchymal cells. Functionally, uPARAP/Endo180 is a rapidly recycling endocytic receptor that delivers its cargo directly into the endosomal-lysosomal system, thus opening a potential route of entry into receptor-positive cells. This combination of specific expression and endocytic function appears well suited for targeting of uPARAP/Endo180-positive cancers by antibody-drug conjugate (ADC) mediated drug delivery. Therefore, we utilized a specific monoclonal antibody against uPARAP/Endo180, raised through immunization of a uPARAP/Endo180 knock-out mouse, which reacts with both the human and the murine receptor, to construct a uPARAP-directed ADC. This antibody was coupled to the highly toxic dolastatin derivative, monomethyl auristatin E, via a cathepsin-labile valine-citrulline linker. With this ADC, we show strong and receptor-dependent cytotoxicity in vitro in uPARAP/Endo180-positive cancer cell lines of sarcoma, glioblastoma and leukemic origin. Furthermore, we demonstrate the potency of the ADC in vivo in a xenograft mouse model with human uPARAP/Endo180-positive leukemic cells, obtaining a complete cure of all tested mice following intravenous ADC treatment with no sign of adverse effects. Our study identifies uPARAP/Endo180 as a promising target for novel therapy against several highly malignant cancer types.
