An Overview of EGFR Mechanisms and Their Implications in Targeted Therapies for Glioblastoma.

Despite all of the progress in understanding its molecular biology and pathogenesis, glioblastoma (GBM) is one of the most aggressive types of cancers, and without an efficient treatment modality at the moment, it remains largely incurable. Nowadays, one of the most frequently studied molecules with important implications in the pathogenesis of the classical subtype of GBM is the epidermal growth factor receptor (EGFR). Although many clinical trials aiming to study EGFR targeted therapies have been performed, none of them have reported promising clinical results when used in glioma patients. The resistance of GBM to these therapies was proven to be both acquired and innate, and it seems to be influenced by a cumulus of factors such as ineffective blood-brain barrier penetration, mutations, heterogeneity and compensatory signaling pathways. Recently, it was shown that EGFR possesses kinase-independent (KID) pro-survival functions in cancer cells. It seems imperative to understand how the EGFR signaling pathways function and how they interconnect with other pathways. Furthermore, it is important to identify the mechanisms of drug resistance and to develop better tailored therapeutic agents.

In vitro evaluation of Axitinib and Sorafenib treatment in glioblastoma cell viability and morphology.

The formation, proliferation, and evolution of glioblastoma (GB) are significantly influenced by pathological angiogenesis. This is supported by several growth factor receptors, such as the vascular endothelial growth factor receptor (VEGFR). In this experiment, we examined how the Food and Drug Administration (FDA) approved VEGFR blockers Sorafenib and Axitinib affect the viability of GB cells in vitro. Cells were cultivated in 96-well culture plates for the experiments, afterwards Sorafenib and Axitinib were administered at doses ranging from 0.3 µM to 80 µM. 2,5-Diphenyl-2H-tetrazolium bromide (MTT) assay was used to assess the impact of VEGFR inhibition on high-grade glioma (HGG) cell lines. To observe the morphological changes in cell shape, we used a 10× magnification microscopy. Our results showed that both Axitinib and Sorafenib retarded GB1B culture proliferation in a dose- and time-dependent manner in comparison to control cohorts that had not received any treatment. The half maximal inhibitory concentration (IC50) value for Axitinib was 3.5839 µM after three days of drug administration and 2.2133 µM after seven days of drug administration. The IC50 value for Sorafenib was 3.5152 µM after three days of drug administration and 1.6846 µM after seven days of drug administration. After the treatment with Axitinib or Sorafenib, very few cells became rounded and detached from the support, others remained adherent to the culture substrate, but acquired a larger, flatter shape. Our results indicate that VEGFR might serve as a key target in the treatment of GB. Although it is known that in vitro some drugs block the VEGFR more potently, clinical evidence is required to show whether this actually translates to better clinical outcomes.

The effect of Azo-dyes on glioblastoma cells in vitro.

Despite the multidisciplinary standard treatment of glioblastoma (GB) consisting of maximal surgical resection, followed by radiotherapy (RT) plus concomitant chemotherapy with temozolomide (TMZ), the majority of patients experience tumor progression and almost universal mortality. In recent years, efforts have been made to create new agents for GB treatment, of which azo-dyes proved to be potential candidates, showing antiproliferative effects by inducing apoptosis and by inhibiting different signaling pathways. In this study we evaluated the antiproliferative the effect of six azo-dyes and TMZ on a low passage human GB cell line using MTT assay. We found that all compounds proved antiproliferative properties on GB cells. At equimolar concentrations azo-dyes induced more cytotoxic effect than TMZ. We found that Methyl Orange required the lowest IC50 for 3 days of treatment (26.4684 µM), whilst for 7 days of treatment, two azo dyes proved to have the highest potency: Methyl Orange IC50 = 13.8808 µM and Sudan I IC50 = 12.4829 µM. The highest IC50 was determined for TMZ under both experimental situations. Conclusions: Our research represents a novelty, by offering unique valuable data regarding the azo-dye cyototoxic effects in high grade brain tumors. This study may focus the attention on azo-dye agents that may represent an insufficient exploited source of agents for cancer treatment.

Intracellular Pathways and Mechanisms of Colored Secondary Metabolites in Cancer Therapy.

Despite the great advancements made in cancer treatment, there are still many unsatisfied aspects, such as the wide palette of side effects and the drug resistance. There is an obvious increasing scientific attention towards nature and what it can offer the human race. Natural products can be used to treat many diseases, of which some plant products are currently used to treat cancer. Plants produce secondary metabolites for their signaling mechanisms and natural defense. A variety of plant-derived products have shown promising anticancer properties in vitro and in vivo. Rather than recreating the natural production environment, ongoing studies are currently setting various strategies to significantly manipulate the quantity of anticancer molecules in plants. This review focuses on the recently studied secondary metabolite agents that have shown promising anticancer activity, outlining their potential mechanisms of action and pathways.

Glioblastoma Stem Cells-Useful Tools in the Battle against Cancer.

Glioblastoma stem cells (GSCs) are cells with a self-renewal ability and capacity to initiate tumors upon serial transplantation that have been linked to tumor cell heterogeneity. Most standard treatments fail to completely eradicate GSCs, causing the recurrence of the disease. GSCs could represent one reason for the low efficacy of cancer therapy and for the short relapse time. Nonetheless, experimental data suggest that the presence of therapy-resistant GSCs could explain tumor recurrence. Therefore, to effectively target GSCs, a comprehensive understanding of their biology and the survival and developing mechanisms during treatment is mandatory. This review provides an overview of the molecular features, microenvironment, detection, and targeting strategies of GSCs, an essential information required for an efficient therapy. Despite the outstanding results in oncology, researchers are still developing novel strategies, of which one could be targeting the GSCs present in the hypoxic regions and invasive edge of the glioblastoma.

Glioblastoma pharmacotherapy: A multifaceted perspective of conventional and emerging treatments (Review).

Due to its localisation, rapid onset, high relapse rate and resistance to most currently available treatment methods, glioblastoma multiforme (GBM) is considered to be the deadliest type of all gliomas. Although surgical resection, chemotherapy and radiotherapy are among the therapeutic strategies used for the treatment of GBM, the survival rates achieved are not satisfactory, and there is an urgent need for novel effective therapeutic options. In addition to single-target therapy, multi-target therapies are currently under development. Furthermore, drugs are being optimised to improve their ability to cross the blood-brain barrier. In the present review, the main strategies applied for GBM treatment in terms of the most recent therapeutic agents and approaches that are currently under pre-clinical and clinical testing were discussed. In addition, the most recently reported experimental data following the testing of novel therapies, including stem cell therapy, immunotherapy, gene therapy, genomic correction and precision medicine, were reviewed, and their advantages and drawbacks were also summarised.

ELTD1-An Emerging Silent Actor in Cancer Drama Play.

The epidermal growth factor, latrophilin, and seven transmembrane domain-containing protein 1 (ELTD1), is a member of the G-protein coupled receptors (GPCRs) superfamily. Although discovered in 2001, ELTD1 has been investigated only by a few research groups, and important data about its role in normal and tumor cells is still missing. Even though its functions and structure are not yet fully understood, recent studies show that ELTD1 has a role in both physiological and pathological angiogenesis, and it appears to be a very important biomarker and a molecular target in cancer diseases. Upregulation of ELTD1 in malignant cells has been reported, and correlated with poor cancer prognosis. This review article aims to compile the existing data and to discuss the current knowledge on ELTD1 structure and signaling, and its role in physiological and neoplastic conditions.

Updated Insights on EGFR Signaling Pathways in Glioma.

Nowadays, due to recent advances in molecular biology, the pathogenesis of glioblastoma is better understood. For the newly diagnosed, the current standard of care is represented by resection followed by radiotherapy and temozolomide administration, but because median overall survival remains poor, new diagnosis and treatment strategies are needed. Due to the quick progression, even with aggressive multimodal treatment, glioblastoma remains almost incurable. It is known that epidermal growth factor receptor (EGFR) amplification is a characteristic of the classical subtype of glioma. However, targeted therapies against this type of receptor have not yet shown a clear clinical benefit. Many factors contribute to resistance, such as ineffective blood-brain barrier penetration, heterogeneity, mutations, as well as compensatory signaling pathways. A better understanding of the EGFR signaling network, and its interrelations with other pathways, are essential to clarify the mechanisms of resistance and create better therapeutic agents.

The Potential of Helianthin Loaded Into Magnetic Nanoparticles to Induce Cytotoxicity in Glioblastoma Cells.

The central nervous system tumors are the most common solid tumors in adults.. Unlike other types of cancers, brain cancer is much difficult to treat because of the blood-brain barrier (BBB) that prevents drug substances from crossing it and accessing the brain. Different types of methods to overcome BBB have been used in vivo and in vitro, of which the use of nanoparticle-mediated delivery of therapeutic drugs is particularly promising. In the present study, we used iron oxide magnetic nanoparticles (NPs) as carrier system for helianthin (He/NPs) to treat cancer cells derived from glioblastoma. An early passage cell cultures (GB1B), established in our laboratory from tissue obtained from a patient diagnosed with glioblastoma, was used. The cells were treated with different concentrations of NPs or HeNPs and then cell proliferation was measured at 24, 48 and 72 hours. Our results showed that the treatment with NPs was well tolerated by glioblastoma cells, the viability of the cells increased very slightly after the treatment. Furthermore, we demonstrated that helianthin loaded Fe3O4 magnetic nanoparticles induced cytotoxicity in human glioblastoma cells. The treatment with HeNPs induced dose and time dependent.

The effect of temozolomide in combination with doxorubicin in glioblastoma cells in vitro.

BACKGROUND: Prior to 2000, the DNA alkylating agents nitrosoureas were used as standard treatment of glioblastoma. Current treatments for glioblastoma patients consist of surgery followed by radiation in combination with temozolomide. Despite therapeutic advances, the prognosis for glioblastoma patients remains grim, with a five-year overall survival below 15%. In this study, our team analyzed the interaction between temozolomide and doxorubicin in a glioblastoma cell line, in vitro. MATERIALS AND METHOD: The cell line, established from a patient who underwent surgery at the "Bagdasar Arseni Emergency Hospital", was exposed to 10 µM and 100 µM of temozolomide and 10 nM and 100 nM of doxorubicin, respectively, over a period of 7, 10 and 14 days, in monotherapy and in combination. RESULTS: The results showed that both temozolomide (66.5% cytotoxicity for the 10 µM dose at 14 days) de and doxorubicin (66.8% cytotoxicity for the 10 nM dose after 14 days) were very effective in killing cancer cells in monotherapy, but failed to produce a synergistic effect when used in combination. CONCLUSION: While the results may be discouraging, they present an interesting prospect into how certain drug interactions can impact treatment response.

Receptor tyrosine kinase targeting in glioblastoma: performance, limitations and future approaches.

From all central nervous system tumors, gliomas are the most common. Nowadays, researchers are looking for more efficient treatments for these tumors, as well as ways for early diagnosis. Receptor tyrosine kinases (RTKs) are major targets for oncology and the development of small-molecule RTK inhibitors has been proven successful in cancer treatment. Mutations or aberrant activation of the RTKs and their intracellular signaling pathways are linked to several malignant diseases, including glioblastoma. The progress in the understanding of malignant glioma evolution has led to RTK targeted therapies with high capacity to improve the therapeutic response while reducing toxicity. In this review, we present the most important RTKs (i.e. EGFR, IGFR, PDGFR and VEGFR) currently used for developing cancer therapeutics together with the potential of RTK-related drugs in glioblastoma treatment. Also, we focus on some therapeutic agents that are currently at different stages of research or even in clinical phases and proved to be suitable as re-purposing candidates for glioblastoma treatment.

Platelet-Derived Growth Factor Receptor and Ionizing Radiation in High Grade Glioma Cell Lines.

Treatment of high grade gliomas (HGGs) has remained elusive due to their high heterogeneity and aggressiveness. Surgery followed by radiotherapy represents the mainstay of treatment for HGG. However, the unfavorable location of the tumor that usually limits total resection and the resistance to radiation therapy are the major therapeutic problems. Chemotherapy with DNA alkylating agent temozolomide is also used to treat HGG, despite modest effects on survival. Disregulation of several growth factor receptors (GFRs) were detected in HGG and receptor amplification in glioblastoma has been suggested to be responsible for heterogeneity propagation through clonal evolution. Molecularly targeted agents inhibiting these membrane proteins have demonstrated significant cytotoxicity in several types of cancer cells when tested in preclinical models. Platelet-derived growth factor receptors (PDGFRs) and associated signaling were found to be implicated in gliomagenesis, moreover, HGG commonly display a Platelet-derived growth factor (PDGF) autocrine pathway that is not present in normal brain tissues. We have previously shown that both the susceptibility towards PDGFR and the impact of the PDGFR inactivation on the radiation response were different in different HGG cell lines. Therefore, we decided to extend our investigation, using two other HGG cell lines that express PDGFR at the cell surface. Here, we investigated the effect of PDGFR inhibition alone or in combination with gamma radiation in 11 and 15 HGG cell lines. Our results showed that while targeting the PDGFR represents a good means of treatment in HGG, the combination of receptor inhibition with gamma radiation did not result in any discernable difference compared to the single treatment. The PI3K/PTEN/Akt/mTOR and Ras/Raf/MEK/ERK pathways are the major signaling pathways emerging from the GFRs, including PDGFR. Decreased sensitivity to radiation-induced cell death are often associated with redundancy in these pro-survival signaling pathways. Here we found that Phosphoinositide 3-kinases (PI3K), Extracellular-signal-regulated kinase 1/2 (ERK1/2), or c-Jun N-terminal kinase 1/2 (JNK1/2) inactivation induced radiosensitivity in HGG cells.