MET signaling promotes DNA repair and radiation resistance in glioblastoma stem-like cells

Biomimetic Nanosensitizer Potentiates Efficient Glioblastoma Gene-Radiotherapy through Synergistic Hypoxia Mitigation and PLK1 Silencing

Postoperative radiotherapy currently stands as the cornerstone of glioblastoma (GBM) treatment. Nevertheless, low-dose radiotherapy has been proven ineffective for GBM, due to hypoxia in the GBM microenvironment, which renders the resistance to radiation-induced cell death. Moreover, the overexpression of the PLK1 gene in glioma cells enhances GBM proliferation, invasion, metastasis, and resistance to radiation. This study introduced a hybrid membrane-camouflaged biomimetic lipid nanosensitizer (CNL@miPA), which efficiently encapsulated gold nanoclusters (PA) and miR-593-5p by a chimeric membrane derived from lipids, cancer cells, and natural killer cells. CNL@miPA exhibited exceptional blood-brain barrier and tumor tissue penetration, effectively ameliorating hypoxia and synergizing with radiotherapy. By enabling prolonged miRNA circulation in the bloodstream and achieving high enrichment at the tumor site, CNL@miPA significantly suppressed tumor growth in combination treatment, thereby significantly extending the survival period of treated mice. Overall, the developed biomimetic nanosensitizer represented an efficient and multifunctional targeted delivery system, offering a novel strategy for gene-radiotherapy of GBM.

Molecular Pathways Implicated in Radioresistance of Glioblastoma Multiforme: What Is the Role of Extracellular Vesicles?

Glioblastoma multiforme (GBM) is a primary brain tumor that is very aggressive, resistant to treatment, and characterized by a high degree of anaplasia and proliferation. Routine treatment includes ablative surgery, chemotherapy, and radiotherapy. However, GMB rapidly relapses and develops radioresistance. Here, we briefly review the mechanisms underpinning radioresistance and discuss research to stop it and install anti-tumor defenses. Factors that participate in radioresistance are varied and include stem cells, tumor heterogeneity, tumor microenvironment, hypoxia, metabolic reprogramming, the chaperone system, non-coding RNAs, DNA repair, and extracellular vesicles (EVs). We direct our attention toward EVs because they are emerging as promising candidates as diagnostic and prognostication tools and as the basis for developing nanodevices for delivering anti-cancer agents directly into the tumor mass. EVs are relatively easy to obtain and manipulate to endow them with the desired anti-cancer properties and to administer them using minimally invasive procedures. Thus, isolating EVs from a GBM patient, supplying them with the necessary anti-cancer agent and the capability of recognizing a specified tissue-cell target, and reinjecting them into the original donor appears, at this time, as a reachable objective of personalized medicine.

Radiation-Triggered Selenium-Engineered Mesoporous Silica Nanocapsules for RNAi Therapy in Radiotherapy-Resistant Glioblastoma

Radiotherapy-resistant glioblastoma (rrGBM) remains a significant clinical challenge because of high infiltrative growth characterized by activation of antiapoptotic signal transduction. Herein, we describe an efficiently biodegradable selenium-engineered mesoporous silica nanocapsule, initiated by high-energy X-ray irradiation and employed for at-site RNA interference (RNAi) to inhibit rrGBM invasion and achieve maximum therapeutic benefit. Our radiation-triggered RNAi nanocapsule showed high physiological stability, good blood-brain barrier transcytosis, and potent rrGBM accumulation. An intratumoral RNAi nanocapsule permitted low-dose X-ray radiation-triggered dissociation for cofilin-1 knockdown, inhibiting rrGBM infiltration. More importantly, tumor suppression was further amplified by electron-affinity aminoimidazole products converted from metronidazole polymers under X-ray radiation-exacerbated hypoxia, which sensitized cell apoptosis to ionizing radiation by fixing reactive oxygen species-induced DNA lesions. In vivo experiments confirmed that our RNAi nanocapsule reduced tumor growth and invasion, prolonging survival in an orthotopic rrGBM model. Generally, we present a promising radiosensitizer that would effectively improve rrGBM-patient outcomes with low-dose X-ray irradiation.

Tumor cell-targeting radiotherapy in the treatment of glioblastoma multiforme using linear accelerators

Although boron neuron capture therapy (BNCT) has enabled the delivery of stronger radiation dose to glioblastoma multiforme (GBM) cells for precision radiotherapy (RT), patients in need are almost unable to access the treatment due to insufficient operating devices. Therefore, we developed targeted sensitization-enhanced radiotherapy (TSER), a strategy that could achieve precision cell-targeted RT using common linear accelerators. TSER, which involves the combination of GoldenDisk (GD; a spherical radioenhancer), 5-aminolevulinic acid (5-ALA), low-intensity ultrasound (US), and low-dose RT, exhibited synergized radiosensitization effects. Both 5-ALA and hyaluronic-acid-immobilized GD can selectively accumulate in GBM to induce chemical and biological enhancement of radiosensitization, resulting in DNA damage, escalation of reactive oxygen species levels, and cell cycle redistribution, in turn sensitizing GBM cells to radiation under US. TSER showed an enhanced therapeutic effect and survival in the treatment of an orthotropic GBM model with only 20% of the radiation dose compared to that of a 10-Gy RT. The strategy with the potential to inhibit GBM progress and rescue the organ at risk using low-dose RT, thereby improving the quality of life of GBM patients, shedding light on achieving cell-targeted RT using universally available linear accelerators. STATEMENT OF SIGNIFICANCE: We invented GoldenDisk (GD), a radioenhancer with hyaluronic-acid (HAc)-coated gold nanoparticle (AuNP)-core/silica shell nanoparticle, to make radiotherapy (RT) safer and smarter. The surface modification of HAc and silica allows GD to target CD44-overexpressed glioblastoma multiforme (GBM) cells and stay structurally stable in cytoplasm throughout the course of RT. By combining GD with low-energy ultrasound and an FDA-approved imaging agent, 5-aminolevulinic acid (5-ALA), GBM cells were sensitized to RT leaving healthy tissues in the vicinity unaffected. The ionized radiation can further be transferred to photoelectronic products with higher cytotoxicity by GD upon collision, achieving higher therapeutic efficacy. With the newly-developed strategy, we are able to achieve low-dose precision RT with the use of only 20% radiation dose.

Cancer Stem Cells: Significance in Origin, Pathogenesis and Treatment of Glioblastoma

Cancer stem cells (CSCs), known also as tumor-initiating cells, are quiescent, pluripotent, self-renewing neoplastic cells that were first identified in hematologic tumors and soon after in solid malignancies. CSCs have attracted remarkable research interest due to their role in tumor resistance to chemotherapy and radiation treatment as well as recurrence. Extensive research has been devoted to the role of CSCs in glioblastoma multiforme (GBM), the most common primary brain tumor in adults, which is characterized by a dismal prognosis because of its aggressive course and poor response to treatment. The aim of the current paper is to provide an overview of current knowledge on the role of cancer stem cells in the pathogenesis and treatment resistance of glioblastoma. The six regulatory mechanisms of glioma stem cells (GSCs)—tumor microenvironment, niche concept, metabolism, immunity, genetics, and epigenetics—are reviewed. The molecular markers used to identify GSCs are described. The role of GSCs in the treatment resistance of glioblastoma is reviewed, along with future treatment options targeting GSCs. Stem cells of glioblastoma thus represent both a driving mechanism of major treatment difficulties and a possible target for more effective future approaches.

MET Inhibitors for the Treatment of Gastric Cancer: What's Their Potential?

Gastric cancer remains a disease with a dismal prognosis. Extensive efforts to find targetable disease drivers in gastric cancer were implemented to improve patient outcomes. Beyond anti-HER2 therapy, MET pathway seems to be culprit of cancer invasiveness with MET-overexpressing tumors having poorer prognosis. Tyrosine kinase inhibitors targeting the HGF/MET pathway were studied in MET-positive gastric cancer, but no substantial benefit was proven. Some patients responded in early phase trials but later developed resistance. Others failed to show any benefit at all. Etiologies of resistance may entail inappropriate patient selection with a lack of MET detection standardization, tumor alternative pathways, variable MET amplification, and genetic variation. Optimizing MET detection techniques and better understanding the MET pathway, as well as tumor bypass mechanisms, are an absolute need to devise means to overcome resistance using targeted therapy alone, or in combination with other synergistic agents to improve outcomes of patients with MET-positive GC.

SUMOylation regulates TGF-β1/Smad4 signalling in-resistant glioma cells

The aim of this study was to explore the role of TGF-β1/Smad4 signalling in the DNA damage-induced ionization radiation (IR) resistance of glioma cells. T98G cells were assigned to the IR group (treated with IR) or the Blank group (with no treatment). The IR-treated cells were also treated/transfected with the TGF-β receptor inhibitor SB431542, SUMO1-overexpressing plasmids (SUMO1 group), SUMO1-interfering plasmids (si-SUMO1 group) or negative control plasmids group. The wound-healing capacity, cell proliferation and cell apoptosis were evaluated by the scratch assay, flow cytometry and the CCK-8 assay, respectively, and protein interactions were investigated by coimmunoprecipitation and colocalization assays. IR-treated T98G cells had DNA damage, but the wound-healing capacity and cell apoptosis were not significantly suppressed. DNA damage also induced TGF-β1, Smad4, SUMO1, SUMO2/3 and Ubc9 expression. In IR-treated cells cultured with SB431542, the wound-healing capacity and proliferation were promoted. SUMO1 and Smad4 colocalized in the nucleus of T98G cells, and the IR-treated cells had a significantly higher expression of the SUMO1-Smad4 protein complex. Smad4 expression in the nucleus was significantly reduced in the si-SUMO1 group, but was markedly increased in the SUMO1 group; the SUMO1 group had significantly elevated apoptotic activity, whereas the si-SUMO1 group showed significantly suppressed apoptotic activity and the si-SUMO1+SB41542 group had the lowest levels of cell apoptosis. DNA damage may activate Smad4 SUMOylation and the SUMOylation of Smad4 participates in the activation of TGF-β/Smad4 signalling; therefore, enhanced Smad4 SUMOylation is critical for the damage-induced activation of IR resistance.

H1/pHGFK1 nanoparticles exert anti-tumoural and radiosensitising effects by inhibition of MET in glioblastoma

Background:

The therapeutic resistance to ionising radiation (IR) and anti-angiogenesis mainly impair the prognosis of patients with glioblastoma. The primary and secondary MET aberrant activation is one crucial factor for these resistances. The kringle 1 domain of hepatocyte growth factor (HGFK1), an angiogenic inhibitor, contains a high-affinity binding domain of MET; however, its effects on glioblastoma remain elusive.

Methods:

We formed the nanoparticles consisting of a folate receptor-targeted nanoparticle-mediated HGFK1 gene (H1/pHGFK1) and studied its anti-tumoural and radiosensitive activities in both subcutaneous and orthotopic human glioma cell-xenografted mouse models. We then elucidated its molecular mechanisms in human glioblastoma cell lines in vitro.

Results:

We demonstrated for the first time that peritumoural injection of H1/pHGFK1 nanoparticles significantly inhibited tumour growth and prolonged survival in tumour-bearing mice, as well as enhanced the anti-tumoural efficacies of IR in vivo by reducing Ki-67 expression, enhancing TUNEL staining-indicated apoptotic indexes, reducing microvascular intensity and reversing IR-induced MET overexpression in tumour tissues. Furthermore, we showed that HGFK1 suppressed the proliferation and induced cell apoptosis and enhanced sensitivity to IR in glioblastoma cell lines, mainly by suppressing the activities of MET receptor, down-regulating ATM-Chk2 axis but up-regulating Chk1.

Conclusions:

H1/pHGFK1 exerts anti-tumoural and radiosensitive activities mainly through the inhibition and reversal of IR-induced MET and ATM–Chk2 axis activities in glioblastoma. H1/pHGFK1 nanoparticles are a potential radiosensitiser and angiogenic inhibitor for glioblastoma treatment.

Molecular and Microenvironmental Determinants of Glioma Stem-Like Cell Survival and Invasion

Glioblastoma multiforme (GBM) is the most frequent primary brain tumor in adults with a 5-year survival rate of 5% despite intensive research efforts. The poor prognosis is due, in part, to aggressive invasion into the surrounding brain parenchyma. Invasion is a complex process mediated by cell-intrinsic pathways, extrinsic microenvironmental cues, and biophysical cues from the peritumoral stromal matrix. Recent data have attributed GBM invasion to the glioma stem-like cell (GSC) subpopulation. GSCs are slowly dividing, highly invasive, therapy resistant, and are considered to give rise to tumor recurrence. GSCs are localized in a heterogeneous cellular niche, and cross talk between stromal cells and GSCs cultivates a fertile environment that promotes GSC invasion. Pro-migratory soluble factors from endothelial cells, astrocytes, macrophages, microglia, and non-stem-like tumor cells can stimulate peritumoral invasion of GSCs. Therefore, therapeutic efforts designed to target the invasive GSCs may enhance patient survival. In this review, we summarize the current understanding of extrinsic pathways and major stromal and immune players facilitating GSC maintenance and survival.