Vandetanib plus sirolimus in adults with recurrent glioblastoma: results of a phase I and dose expansion cohort study

Unlocking Hope: Anti-VEGFR inhibitors and their potential in glioblastoma treatment

PURPOSE

This systematic review summarizes evidence of VEGFR gene mutations and VEGF/VEGFR protein expression in glioblastoma multiforme (GBM) patients, alongside the efficacy and safety of anti-VEGFR tyrosine kinase inhibitors (TKIs) for GBM treatment.

METHODS

A comprehensive literature review was conducted using PubMed up to August 2023. Boolean operators and MeSH term "glioma," along with specific VEGFR-related keywords, were utilized following thorough examination of existing literature.

RESULTS

VEGFR correlates with glioma grade and GBM progression, presenting a viable therapeutic target. Regorafenib and axitinib show promise among studied TKIs. Other multi-targeted TKIs (MTKI) and combination therapies exhibit potential, albeit limited by blood-brain barrier penetration and toxicity. Combining treatments like radiotherapy and enhancing BBB penetration may benefit patients. Further research is warranted in patient quality of life and biomarker-guided selection.

CONCLUSION

While certain therapies hold promise for GBM, future research should prioritize personalized medicine and innovative strategies for improved treatment outcomes.

Mechanistic insights and the clinical prospects of targeted therapies for glioblastoma: a comprehensive review

Glioblastoma (GBM) is a fatal brain tumour that is traditionally diagnosed based on histological features. Recent molecular profiling studies have reshaped the World Health Organization approach in the classification of central nervous system tumours to include more pathogenetic hallmarks. These studies have revealed that multiple oncogenic pathways are dysregulated, which contributes to the aggressiveness and resistance of GBM. Such findings have shed light on the molecular vulnerability of GBM and have shifted the disease management paradigm from chemotherapy to targeted therapies. Targeted drugs have been developed to inhibit oncogenic targets in GBM, including receptors involved in the angiogenic axis, the signal transducer and activator of transcription 3 (STAT3), the PI3K/AKT/mTOR signalling pathway, the ubiquitination-proteasome pathway, as well as IDH1/2 pathway. While certain targeted drugs showed promising results in vivo, the translatability of such preclinical achievements in GBM remains a barrier. We also discuss the recent developments and clinical assessments of targeted drugs, as well as the prospects of cell-based therapies and combinatorial therapy as novel ways to target GBM. Targeted treatments have demonstrated preclinical efficacy over chemotherapy as an alternative or adjuvant to the current standard of care for GBM, but their clinical efficacy remains hindered by challenges such as blood-brain barrier penetrance of the drugs. The development of combinatorial targeted therapies is expected to improve therapeutic efficacy and overcome drug resistance.

From signalling pathways to targeted therapies: unravelling glioblastoma's secrets and harnessing two decades of progress

Glioblastoma, a rare, and highly lethal form of brain cancer, poses significant challenges in terms of therapeutic resistance, and poor survival rates for both adult and paediatric patients alike. Despite advancements in brain cancer research driven by a technological revolution, translating our understanding of glioblastoma pathogenesis into improved clinical outcomes remains a critical unmet need. This review emphasises the intricate role of receptor tyrosine kinase signalling pathways, epigenetic mechanisms, and metabolic functions in glioblastoma tumourigenesis and therapeutic resistance. We also discuss the extensive efforts over the past two decades that have explored targeted therapies against these pathways. Emerging therapeutic approaches, such as antibody-toxin conjugates or CAR T cell therapies, offer potential by specifically targeting proteins on the glioblastoma cell surface. Combination strategies incorporating protein-targeted therapy and immune-based therapies demonstrate great promise for future clinical research. Moreover, gaining insights into the role of cell-of-origin in glioblastoma treatment response holds the potential to advance precision medicine approaches. Addressing these challenges is crucial to improving outcomes for glioblastoma patients and moving towards more effective precision therapies.

Anlotinib as Monotherapy or Combination Therapy for Recurrent High-Grade Glioma: A Retrospective Study

Background

Anlotinib is a multi-target anti-angiogenic agent. The retrospective study was conducted to evaluate the safety and effectiveness of anlotinib as monotherapy or combination therapy for the treatment of recurrent high-grade gliomas.

Methods

In this retrospective study, patients with recurrent high-grade glioma (according to the 2021 World Health Organization classification as levels III-IV) at Sichuan Cancer Hospital from June 2019 to June 2022 were included. The patients were divided into an anlotinib-monotherapy group and an anlotinib-combination group, and received oral anlotinib 8 to 12 mg once a day, with 2 weeks on/1 week off. The primary endpoint was progression-free survival (PFS). The Secondary endpoints included overall survival (OS), 6-month PFS rate, objective response rate (ORR), and disease control rate (DCR). Also, adverse events were evaluated using the National Cancer Institute's Common Terminology Criteria for Adverse Events (CTCAE version 5.0).

Results

A total of 29 patients (including 20 glioblastomas, 1 diffuse midline glioma, 5 anaplastic astrocytoma, and 3 anaplastic oligodendroglioma) were included in this study. Of these, 34.48% of the patients were treated with anlotinib alone and 65.52% with anlotinib combination therapy. The median follow-up time was 11.6 months (95% confidence interval [CI]: 9.4-15.7). The median PFS was 9.4 months (95% CI: 6.5-12.3), and the 6-month PFS rate was 62.1%. The median OS was 12.7 months (95% CI: 9.7-15.7), and the 12-month OS rate was 48.3%. Evaluation of treatment response was performed according to RANO (response assessment in neuro-oncology, RANO) criteria, including 21 partial response, 6 stable disease, and 2 PFS events. The ORR and DCR were 72.4%, and 93.1%, respectively. Grade III AEs occurred in 2 patients, and the others were less than grade III. The most common AE was thrombocytopenia, with an incidence rate of 31.0%. All AEs were alleviated and controlled by symptomatic treatment. No treatment-related deaths occurred.

Conclusion

Anlotinib had a low incidence of AEs and good safety in the treatment of recurrent high-grade glioma. Moreover, it showed good short-term effectiveness and significantly prolonged the PFS of patients, which may become a promising therapeutic option for recurrent high-grade glioma and lay a foundation for further clinical studies.

Metabolic adverse events of multitarget kinase inhibitors: a systematic review

PURPOSE

Multitargeted kinase inhibitors (MKIs) are used for the treatment of several cancers. By targeting multiple signaling pathways, MKIs have become cornerstones of the oncologic treatment. Although their use leads to important results in terms of survival, treatment with MKIs can determine important side effects the clinician must be aware of. Among those, arterial hypertension, mucositis and skin lesions are universally reported, while data about metabolic alterations are scarce. In our review, we focused on glucose and lipid alterations in MKI-treated patients.

METHODS

We searched for articles, published between January 2012 and December 2022, evaluating the effects on lipid and glucose metabolism of four MKIs (Cabozantinib, Lenvatinib, Sorafenib, and Vandetanib) in adult patients with cancer. We focused on drugs approved for thyroid malignancies, since a worse metabolic control may potentially impact life expectancy, due to their better overall survival rate.

RESULTS

As for glucose metabolism, the majority of the studies reported elevation of glucose levels (prevalence: 1-17%) with different grades of severity, including death. As for cholesterol, 12 studies reported worsening or new-onset hypercholesterolemia (prevalence: 4-40%). Finally, 19 studies reported different grades of hypertriglyceridemia (prevalence: 1-86%), sometimes leading to life-threatening events.

CONCLUSIONS

Despite some inherent limitations, our analysis may cast light upon some of the MKIs metabolic disorders that can impact on patients' health, especially when long-term survival is expected. Future clinical trials should consider routine assessment of glucose and lipid levels, because underdetection and underreporting of alterations can lead to the overlooking of important adverse events.

The efficacy and adverse effects of anlotinib in the treatment of high-grade glioma: A retrospective analysis

Introduction

Anlotinib, a novel multi-kinase inhibitor, was found to improve progression-free survival (PFS) in brain metastases.

Methods

This paper retrospectively analyzed 26 newly diagnosed or recurrent high-grade gliomas from 2017 to 2022, and the patients received oral anlotinib during concurrent postoperative chemoradiotherapy or after recurrence. Efficacy was evaluated according to the Response Assessment in Neuro-Oncology (RANO) criteria, and the main study endpoints were PFS at 6 months and overall survival (OS) at 1 year.

Results

After the follow-up, until May 2022, 13 patients survived and 13 patients died, with a median follow-up time of 25.6 months. The disease control rate (DCR) was 96.2% (25/26), and the overall response rate (ORR) rate was 73.1% (19/26). The median PFS after oral anlotinib was 8.9 months (0.8-15.1), and the PFS at 6 months was 72.5%. The median OS after oral anlotinib was 12 months (1.6-24.4), and the OS at 12 months was 42.6%. Anlotinib-related toxicities were observed in 11 patients, mostly grades 1-2. In the multivariate analysis, patients with Karnofsky Performance Scale (KPS) above 80 had a highermedian PFS of 9.9months (p = 0.02), and their sex, age, IDH mutation, MGMTmethylation, and whether anlotinib was combined with chemoradiotherapy or maintenance treatment had no effect on PFS.

Conclusion

We found that anlotinib combined with chemoradiotherapy in treating high-grade central nervous system (CNS) tumors can prolong PFS and OS and that it was safe.

Safety and Efficacy of Hypofractionated Stereotactic Radiotherapy with Anlotinib Targeted Therapy for Glioblastoma at the First Recurrence: A Preliminary Report

(1) Background: Hypofractionated stereotactic radiotherapy (HSRT) and anti-vascular endothelial growth factor (VEGF) antibodies have been reported to have a promising survival benefit in recent studies. Anlotinib is a new oral VEGF receptor inhibitor. This report describes our experience using HSRT and anlotinib for recurrent glioblastoma (rGBM). (2) Methods: Between December 2019 and June 2020, rGBM patients were retrospectively analysed. Anlotinib was prescribed at 12 mg daily during HSRT. Adjuvant anlotinib was administered d1-14 every 3 weeks. The primary endpoint was the objective response rate (ORR). Secondary endpoints included overall survival (OS), progression-free survival (PFS) after salvage treatment, and toxicity. (3) Results: Five patients were enrolled. The prescribed dose was 25.0 Gy in 5 fractions. The median number of cycles of anlotinib was 21 (14–33). The ORR was 100%. Three (60%) patients had the best outcome of a partial response (PR), and 2 (40%) achieved a complete response (CR). One patient died of tumour progression at the last follow-up. Two patients had grade 2 hand-foot syndrome. (4) Conclusions: Salvage HSRT combined with anlotinib showed a favourable outcome and acceptable toxicity for rGBM. A prospective phase II study (NCT04197492) is ongoing to further investigate the regimen.

Disentangling the signaling pathways of mTOR complexes, mTORC1 and mTORC2, as a therapeutic target in glioblastoma

Aberrant signaling of mechanistic target of rapamycin (mTOR' aka mammalian target of rapamycin) is shown to be linked to tumorigenesis of numerous malignancies including glioblastoma (GB). Glioblastoma mTOR is a serine threonine kinase that functions by forming two multiprotein complexes. There complexes are named mTORC1 and mTORC2 and downstream activated substrate execute cellular and metabolic functions. This signaling cascade of PI3K/AKT/mTOR is often upregulated due to frequent loss of the tumor suppressor PTEN, a phosphatase that functions antagonistically to PI3K. mTOR regulates cell growth, motility, and metabolism by forming two multiprotein complexes, mTORC1 and mTORC2, which are composed of special binding partners. These complexes are sensitive to distinct stimuli. mTORC1 is sensitive to nutrients and mTORC2 is regulated via PI3K and growth factor signaling. Since rapamycin and it's analogue are less effective in treatment of GB, we used novel ATP-competitive dual inhibitors of mTORC1 and mTORC2, namely, Torin1, Torin2, and XL388. Torin2 caused a concentration dependent pharmacodynamic effects on inhibition of phosphorylation of the mTORC1 substrates S6K^Ser235/236 and 4E-BP1^Thr37/46 as well as the mTORC2 substrate AKT^Ser473 resulting in suppression of tumor cell proliferation and migration. Torin1 showed similar effects only at higher doses. Another small molecule compound, XL388 suppressed cell proliferation at a higher dose but failed to inhibit cell migration. Torin1 suppressed phosphorylation of PRAS40^Thr246, however Torin2 completely abolished it. XL388 treatment inhibited the phosphorylation of PRAS40^Thr246 at higher doses only. These findings underscore the use of novel compounds in treatment of cancer. In addition, formulation of third generation mTOR inhibitor "Rapalink-1" may provide new aspects to target mTOR pathways. Numerous inhibitors are currently being used in clinical trials that are aimed to target activated mTOR pathways.

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.

Regulation of autophagy as a therapeutic option in glioblastoma

Around three out of one hundred thousand people are diagnosed with glioblastoma multiforme, simply called glioblastoma, which is the most common primary brain tumor in adults. With a dismal prognosis of a little over a year, receiving a glioblastoma diagnosis is oftentimes fatal. A major advancement in its treatment was made almost two decades ago when the alkylating chemotherapeutic agent temozolomide (TMZ) was combined with radiotherapy (RT). Little progress has been made since then. Therapies that focus on the modulation of autophagy, a key process that regulates cellular homeostasis, have been developed to curb the progression of glioblastoma. The dual role of autophagy (cell survival or cell death) in glioblastoma has led to the development of autophagy inhibitors and promoters that either work as monotherapies or as part of a combination therapy to induce cell death, cellular senescence, and counteract the ability of glioblastoma stem cells (GSCs) for initiating tumor recurrence. The myriad of cellular pathways that act upon the modulation of autophagy have created contention between two groups: those who use autophagy inhibition versus those who use promotion of autophagy to control glioblastoma growth. We discuss rationale for using current major therapeutics, their molecular mechanisms for modulation of autophagy in glioblastoma and GSCs, their potentials for making strides in combating glioblastoma progression, and their possible shortcomings. These shortcomings may fuel the innovation of novel delivery systems and therapies involving TMZ in conjunction with another agent to pave the way towards a new gold standard of glioblastoma treatment.

The Current State of Potential Therapeutic Modalities for Glioblastoma Multiforme: A Clinical Review

Glioblastoma multiforme (GBM), as the most lethal brain tumor, continues to be incurable. Considering the high mortality rate of GBM, it is crucial to develop new treatment approaches. Conventional therapies, including maximal surgical resection, radiation therapy, and chemotherapy (typically temozolomide), have not led to significant changes in the survival rates of GBM patients. However, emerging modalities, such as the use of tyrosine kinase inhibitors, mTOR inhibitors, NF-κB modulators, nitrosoureas, and immunotherapeutic agents have shown promising in improving GBM outcomes. In this context, we reviewed the current status of GBM treatment, the efficacy of existing standard therapies in improving disease outcomes, and future therapeutic directions.

Novel Receptor Tyrosine Kinase Pathway Inhibitors for Targeted Radionuclide Therapy of Glioblastoma

Glioblastoma (GB) remains the most fatal brain tumor characterized by a high infiltration rate and treatment resistance. Overexpression and/or mutation of receptor tyrosine kinases is common in GB, which subsequently leads to the activation of many downstream pathways that have a critical impact on tumor progression and therapy resistance. Therefore, receptor tyrosine kinase inhibitors (RTKIs) have been investigated to improve the dismal prognosis of GB in an effort to evolve into a personalized targeted therapy strategy with a better treatment outcome. Numerous RTKIs have been approved in the clinic and several radiopharmaceuticals are part of (pre)clinical trials as a non-invasive method to identify patients who could benefit from RTKI. The latter opens up the scope for theranostic applications. In this review, the present status of RTKIs for the treatment, nuclear imaging and targeted radionuclide therapy of GB is presented. The focus will be on seven tyrosine kinase receptors, based on their central role in GB: EGFR, VEGFR, MET, PDGFR, FGFR, Eph receptor and IGF1R. Finally, by way of analyzing structural and physiological characteristics of the TKIs with promising clinical trial results, four small molecule RTKIs were selected based on their potential to become new therapeutic GB radiopharmaceuticals.

Therapeutic strategies of recurrent glioblastoma and its molecular pathways 'Lock up the beast'

Glioblastoma multiforme (GBM) has a poor prognosis-despite aggressive primary treatment composed of surgery, radiotherapy and chemotherapy, median survival is still around 15 months. It starts to grow again after a year of treatment and eventually nothing is effective at this stage. Recurrent GBM is one of the most disappointing fields for researchers in which their efforts have gained no benefit for patients. They were directed for a long time towards understanding the molecular basis that leads to the development of GBM. It is now known that GBM is a heterogeneous disease and resistance comes mainly from the regrowth of malignant cells after eradicating specific clones by targeted treatment. Epidermal growth factor receptor, platelet derived growth factor receptor, vascular endothelial growth factor receptor are known to be highly active in primary and recurrent GBM through different underlying pathways, despite this bevacizumab is the only Food and Drug Administration (FDA) approved drug for recurrent GBM. Immunotherapy is another important promising modality of treatment of GBM, after proper understanding of the microenvironment of the tumour and overcoming the reasons that historically stigmatise GBM as an 'immunologically cold tumour'. Radiotherapy can augment the effect of immunotherapy by different mechanisms. Also, dual immunotherapy which targets immune pathways at different stages and through different receptors further enhances immune stimulation against GBM. Delivery of pro-drugs to be activated at the tumour site and suicidal genes by gene therapy using different vectors shows promising results. Despite using neurotropic viral vectors specifically targeting glial cells (which are the cells of origin of GBM), no significant improvement of overall-survival has been seen as yet. Non-viral vectors 'polymeric and non-polymeric' show significant tumour shrinkage in pre-clinical trials and now at early-stage clinical trials. To this end, in this review, we aim to study the possible role of different molecular pathways that are involved in GBM's recurrence, we will also review the most relevant and recent clinical experience with targeted treatments and immunotherapies. We will discuss trials utilised tyrosine receptor kinase inhibitors, immunotherapy and gene therapy in recurrent GBM pointing to the causes of potential disappointing preliminary results of some of them. Additionally, we are suggesting a possible future treatment based on recent successful clinical data that could alter the outcome for GBM patients.

Novel mTORC1 Inhibitors Kill Glioblastoma Stem Cells

Glioblastoma (GBM) is an aggressive tumor of the brain, with an average post-diagnosis survival of 15 months. GBM stem cells (GBMSC) resist the standard-of-care therapy, temozolomide, and are considered a major contributor to tumor resistance. Mammalian target of rapamycin Complex 1 (mTORC1) regulates cell proliferation and has been shown by others to have reduced activity in GBMSC. We recently identified a novel chemical series of human-safe piperazine-based brain-penetrant mTORC1-specific inhibitors. We assayed the piperazine-mTOR binding strength by two biophysical measurements, biolayer interferometry and field-effect biosensing, and these confirmed each other and demonstrated a structure-activity relationship. As mTORC1 is altered in human GBMSC, and as mTORC1 inhibitors have been tested in previous GBM clinical trials, we tested the killing potency of the tightest-binding piperazines and observed that these were potent GBMSC killers. GBMSCs are resistant to the standard-of-care temozolomide therapy, but temozolomide supplemented with tight-binding piperazine meclizine and flunarizine greatly enhanced GBMSC death over temozolomide alone. Lastly, we investigated IDH1-mutated GBMSC mutations that are known to affect mitochondrial and mTORC1 metabolism, and the tight-binding meclizine provoked 'synthetic lethality' in IDH1-mutant GBMSCs. In other words, IDH1-mutated GBMSC showed greater sensitivity to the coadministration of temozolomide and meclizine. These data tend to support a novel clinical strategy for GBM, i.e., the co-administration of meclizine or flunarizine as adjuvant therapy in the treatment of GBM and IDH1-mutant GBM.

Dendrimer-Mediated Targeted Delivery of Rapamycin to Tumor-Associated Macrophages Improves Systemic Treatment of Glioblastoma

Glioblastoma exhibits high mortality rates due to challenges with drug delivery to the brain and into solid tumors. This two-pronged barrier necessitates high doses of systemic therapies, resulting in significant off-target toxicities. Recently, dendrimer-nanomedicines (without ligands) have shown promise for targeting specific cells in brain tumors from systemic circulation, for improved efficacy and amelioration of systemic toxicities. A dendrimer-rapamycin conjugate (D-Rapa) is presented here that specifically targets tumor-associated macrophages (TAMs) in glioblastoma from systemic administration. D-Rapa improves suppression of pro-tumor expression in activated TAMs and antiproliferative properties of rapamycin in glioma cells in vitro. In vivo, D-Rapa localizes specifically within TAMs, acting as depots to release rapamycin into the tumor microenvironment. This targeted delivery strategy yields improved reduction in tumor burden and systemic toxicities in a challenging, clinically relevant orthotopic syngeneic model of glioblastoma, demonstrating the significant potential of dendrimers as targeted immunotherapies for improving glioblastoma treatment, still an unmet need.

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.

Targeted therapy with anlotinib for patient with recurrent glioblastoma: A case report and literature review

RATIONALE

Glioblastoma (GBM) is the most aggressive malignant brain tumor in adults. The first choice for GBM is surgery, and followed by a combination of radiotherapy and chemotherapy. There are limited treatments for patients with recurrent GBM. Relapsed patients usually have a worse prognosis, and with a median survival time of <6 months. Anlotinib is a novel small molecule multi-target tyrosine kinase inhibitor that can inhibit tumor angiogenesis and inhibit tumor cell growth. This drug has been used to treat advanced lung cancer.

PATIENT CONCERNS

We present a case of recurrent GBM was treated with anlotinib in this report. The patient was diagnosed with GBM in August 2016 and treated with surgery and temozolomide (TMZ) chemotherapy. She was diagnosed with recurrence in February 2017 following which she was treated with gamma knife and TMZ chemotherapy. In November 2017, the patient presented with decreased vision in left eye. She was given radiation and her left eye vision returned to normal after radiation. On May23, 2018, the patient reported a decrease in left visual acuity again.

DIAGNOSES

Brain magnetic resonance imaging (MRI) showed progression of the disease, and the tumor invaded the left optic nerve.

INTERVENTIONS

This patient was administer anlotinib 12 mg po qd (d1-14, 21days as a cycle). Three cycles anlotinib were given to this patient.

OUTCOMES

The patient reported her left visual acuity increased over 10 days after first cycle of anlotinib treatment. MRI scan revealed tumor volume shrinks, especially the part that invades the left optic nerve shrinks significantly at 26 days after anlotinib treatment on August 11, 2018. However, the tumor progressed in 2 months after using of anlotinib. From the beginning of the application of anlotinib to death, her survival time was 110 days.

LESSONS

Anlotinib treatment with mild side effects may be a new option for the patients with recurrent glioblastoma.

Diverse signaling mechanisms of mTOR complexes: mTORC1 and mTORC2 in forming a formidable relationship

Activation of Mechanistic target of rapamycin (mTOR) signaling plays a crucial role in tumorigenesis of numerous malignancies including glioblastoma (GB). The Canonical PI3K/Akt/mTOR signaling cascade is commonly upregulated due to loss of the tumor suppressorm PTEN, a phosphatase that acts antagonistically to the kinase (PI3K) in conversion of PIP2 to PIP3. mTOR forms two multiprotein complexes, mTORC1 and mTORC2 which are composed of discrete protein binding partners to regulate cell growth, motility, and metabolism. These complexes are sensitive to distinct stimuli, as mTORC1 is sensitive to nutrients while mTORC2 is regulated via PI3K and growth factor signaling. The main function of mTORC1 is to regulate protein synthesis and cell growth through downstream molecules: 4E-BP1 (also called EIF4E-BP1) and S6K. On the other hand, mTORC2 is responsive to growth factor signaling by phosphorylating the C-terminal hydrophobic motif of some AGC kinases like Akt and SGK and it also plays a crucial role in maintenance of normal and cancer cells through its association with ribosomes, and is involved in cellular metabolic regulation. mTORC1 and mTORC2 regulate each other, as shown by the fact that Akt regulates PRAS40 phosphorylation, which disinhibits mTORC1 activity, while S6K regulates Sin1 to modulate mTORC2 activity. Allosteric inhibitors of mTOR, rapamycin and rapalogs, remained ineffective in clinical trials of Glioblastoma (GB) patients, in part due to their incomplete inhibition of mTORC1 as well as unexpected activation of mTOR via the loss of negative feedback loops. In recent years, novel ATP binding inhibitors of mTORC1 and mTORC2 suppress mTORC1 activity completely by total dephosphorylation of its downstream substrate pS6K^Ser235/236, while effectively suppressing mTORC2 activity, as demonstrated by complete dephosphorylation of pAKT^Ser473. Furthermore by these novel combined mTORC1/mTORC2 inhibitors reduced the proliferation and self-renewal of GB cancer stem cells. However, a search of more effective way to target mTOR has generated a third generation inhibitor of mTOR, "Rapalink", that bivalently combines rapamycin with an ATP-binding inhibitor, which effectively abolishes the mTORC1 activity. All in all, the effectiveness of inhibitors of mTOR complexes can be judged by their ability to suppress both mTORC1/mTORC2 and their ability to impede both cell proliferation and migration along with aberrant metabolic pathways.

Jinlong capsule inhibits migration and invasion in human glioblastoma cells via the modulation of mTOR/S6 signaling pathway

Aim: To investigate the anticancer effects of Jinlong capsule (JLC) against human glioblastoma cells and the possible underlying mechanism. Methods: Cell Counting Kit-8 and colony formation assay were adopted for the analysis of cell viability. Cell invasion and migration were evaluated by transwell and wound healing assays. Then, the expression level of mammalian target of rapamycin (mTOR), phosphorylated mTOR (p-mTOR), S6 and phosphorylated S6 (p-S6) were determined by western blotting. Results: The results showed that JLC significantly inhibited human glioblastoma cell proliferation, invasion and migration in a dose-dependent manner. The expressions of p-mTOR and p-S6 were dramatically suppressed by JLC. Furtherly, inhibition of mTOR reduced the cell migration and invasion, while the mTOR agonist (MHY1485) could partially reverse the anti-migration and anti-invasion activity of JLC. Conclusion: The above results suggested that JLC would be a potential candidate for the treatment of glioblastoma.

The effect of the mTOR inhibitor rapamycin on glucoCEST signal in a preclinical model of glioblastoma

PURPOSE

The mammalian target of rapamycin is an enzyme that regulates cell metabolism and proliferation. It is up-regulated in aggressive tumors, such as glioblastoma, leading to increased glucose uptake and consumption. It has been suggested that glucose CEST signals reflect the delivery and tumor uptake of glucose. The inhibitor rapamycin (sirolimus) has been applied as a glucose deprivation treatment; thus, glucose CEST MRI could potentially be useful for monitoring the tumor responses to inhibitor treatment.

METHODS

A human U87-EGFRvIII xenograft model in mice was studied. The mice were treated with a mammalian target of Rapamycin inhibitor, rapamycin. The effect of the treatment was evaluated in vivo with dynamic glucose CEST MRI.

RESULTS

Rapamycin treatment led to significant increases (P < 0.001) in dynamic glucose-enhanced signal in both the tumor and contralateral brain as compared to the no-treatment group, namely a maximum enhancement of 3.7% ± 2.3% (tumor, treatment) versus 1.9% ± 0.4% (tumor, no-treatment), 1.7% ± 1.1% (contralateral, treatment), and 1.0% ± 0.4% (contralateral, no treatment). Dynamic glucose-enhanced contrast remained consistently higher in treatment versus no-treatment groups for the duration of the experiment (17 min). This was confirmed with area-under-curve analysis.

CONCLUSION

Increased glucose CEST signal was found after mammalian target of Rapamycin inhibition treatment, indicating potential for dynamic glucose-enhanced MRI to study tumor response to glucose deprivation treatment.

Viral and other therapies for recurrent glioblastoma: is a 24-month durable response unusual?

A phase I trial of an engineered poliovirus for the treatment of recurrent glioblastoma (GBM) has attracted attention due to 8 survivors reaching the 24-month and 5 reaching the 36-month survival landmarks.1 Genetically engineered viruses (oncolytic viruses) have been in trials for GBM for almost two decades.2 These replication-competent (tumor-selective, oncolytic, replication-conditional) viruses or replication-defective viral vectors (gene therapy) deliver cytotoxic payloads to tumors, leading to immunogenic death and intratumoral inflammatory responses. This transforms the tumor microenvironment from immunologically naïve ("cold") to inflamed ("hot"), increasing immune cell recognition of tumor antigens and the durable responses observed in virotherapy.3,4 Several current and past virotherapy trials have reported a "tail" of apparent responders at the 24-month landmark. Other modalities have also reported a "tail" of seemingly long-term survivors. These trials seem to show that these responder "tails" characterize a defined subset of GBM patients.

Autophagic and Apoptotic Pathways as Targets for Chemotherapy in Glioblastoma

Glioblastoma multiforme is the most malignant and aggressive type of brain tumor, with a mean life expectancy of less than 15 months. This is due in part to the high resistance to apoptosis and moderate resistant to autophagic cell death in glioblastoma cells, and to the poor therapeutic response to conventional therapies. Autophagic cell death represents an alternative mechanism to overcome the resistance of glioblastoma to pro-apoptosis-related therapies. Nevertheless, apoptosis induction plays a major conceptual role in several experimental studies to develop novel therapies against brain tumors. In this review, we outline the different components of the apoptotic and autophagic pathways and explore the mechanisms of resistance to these cell death pathways in glioblastoma cells. Finally, we discuss drugs with clinical and preclinical use that interfere with the mechanisms of survival, proliferation, angiogenesis, migration, invasion, and cell death of malignant cells, favoring the induction of apoptosis and autophagy, or the inhibition of the latter leading to cell death, as well as their therapeutic potential in glioma, and examine new perspectives in this promising research field.

Rapamycin promotes differentiation increasing βIII-tubulin, NeuN, and NeuroD while suppressing nestin expression in glioblastoma cells

Glioblastoma cells feature mammalian target of rapamycin (mTOR) up-regulation which relates to a variety of effects such as: lower survival, higher infiltration, high stemness and radio- and chemo-resistance. Recently, it was demonstrated that mTOR may produce a gene shift leading to altered protein expression. Therefore, in the present study we administered different doses of the mTOR inhibitor rapamycin to explore whether the transcription of specific genes are modified. By using a variety of methods we demonstrate that rapamycin stimulates gene transcription related to neuronal differentiation while inhibiting stemness related genes such as nestin. In these experimental conditions, cell phenotype shifts towards a pyramidal neuron-like shape owing long branches. Rapamycin suppressed cell migration when exposed to fetal bovine serum (FBS) while increasing the cell adhesion protein phospho-FAK (pFAK). The present study improves our awareness of basic mechanisms which relate mTOR activity to the biology of glioblastoma cells. These findings apply to a variety of effects which can be induced by mTOR regulation in the brain. In fact, the ability to promote neuronal differentiation might be viewed as a novel therapeutic pathway to approach neuronal regeneration.

Incidence, Diagnosis, and Management of QT Prolongation Induced by Cancer Therapies: A Systematic Review

Background

The cardiovascular complications of cancer therapeutics are the focus of the burgeoning field of cardio‐oncology. A common challenge in this field is the impact of cancer drugs on cardiac repolarization (ie, QT prolongation) and the potential risk for the life‐threatening arrhythmia torsades de pointes. Although QT prolongation is not a perfect marker of arrhythmia risk, this has become a primary safety metric among oncologists. Cardiologists caring for patients receiving cancer treatment should become familiar with the drugs associated with QT prolongation, its incidence, and appropriate management strategies to provide meaningful consultation in this complex clinical scenario.

Methods and Results

In this article, we performed a systematic review (using Preferred Reporting Items of Systematic Reviews and Meta‐Analyses (PRISMA) guidelines) of commonly used cancer drugs to determine the incidence of QT prolongation and clinically relevant arrhythmias. We calculated summary estimates of the incidence of all and clinically relevant QT prolongation as well as arrhythmias and sudden cardiac death. We then describe strategies to prevent, identify, and manage QT prolongation in patients receiving cancer therapy. We identified a total of 173 relevant publications. The weighted incidence of any corrected QT (QTc) prolongation in our systematic review in patients treated with conventional therapies (eg, anthracyclines) ranged from 0% to 22%, although QTc >500 ms, arrhythmias, or sudden cardiac death was extremely rare. The risk of QTc prolongation with targeted therapies (eg, small molecular tyrosine kinase inhibitors) ranged between 0% and 22.7% with severe prolongation (QTc >500 ms) reported in 0% to 5.2% of the patients. Arrhythmias and sudden cardiac death were rare.

Conclusions

Our systematic review demonstrates that there is variability in the incidence of QTc prolongation of various cancer drugs; however, the clinical consequence, as defined by arrhythmias or sudden cardiac death, remains rare.

mTOR-Dependent Cell Proliferation in the Brain

The mammalian Target of Rapamycin (mTOR) is a molecular complex equipped with kinase activity which controls cell viability being key in the PI3K/PTEN/Akt pathway. mTOR acts by integrating a number of environmental stimuli to regulate cell growth, proliferation, autophagy, and protein synthesis. These effects are based on the modulation of different metabolic pathways. Upregulation of mTOR associates with various pathological conditions, such as obesity, neurodegeneration, and brain tumors. This is the case of high-grade gliomas with a high propensity to proliferation and tissue invasion. Glioblastoma Multiforme (GBM) is a WHO grade IV malignant, aggressive, and lethal glioma. To date, a few treatments are available although the outcome of GBM patients remains poor. Experimental and pathological findings suggest that mTOR upregulation plays a major role in determining an aggressive phenotype, thus determining relapse and chemoresistance. Among several activities, mTOR-induced autophagy suppression is key in GBM malignancy. In this article, we discuss recent evidence about mTOR signaling and its role in normal brain development and pathological conditions, with a special emphasis on its role in GBM.

Crossing the Blood-Brain Barrier: Recent Advances in Drug Delivery to the Brain

CNS disorders are on the rise despite advancements in our understanding of their pathophysiological mechanisms. A major hurdle to the treatment of these disorders is the blood-brain barrier (BBB), which serves as an arduous janitor to protect the brain. Many drugs are being discovered for CNS disorders, which, however fail to enter the market because of their inability to cross the BBB. This is a pronounced challenge for the pharmaceutical fraternity. Hence, in addition to the discovery of novel entities and drug candidates, scientists are also developing new formulations of existing drugs for brain targeting. Several approaches have been investigated to allow therapeutics to cross the BBB. As the molecular structure of the BBB is better elucidated, several key approaches for brain targeting include physiological transport mechanisms such as adsorptive-mediated transcytosis, inhibition of active efflux pumps, receptor-mediated transport, cell-mediated endocytosis, and the use of peptide vectors. Drug-delivery approaches comprise delivery from microspheres, biodegradable wafers, and colloidal drug-carrier systems (e.g., liposomes, nanoparticles, nanogels, dendrimers, micelles, nanoemulsions, polymersomes, exosomes, and quantum dots). The current review discusses the latest advancements in these approaches, with a major focus on articles published in 2015 and 2016. In addition, we also cover the alternative delivery routes, such as intranasal and convection-enhanced diffusion methods, and disruption of the BBB for brain targeting.

Suppression of the invasive potential of Glioblastoma cells by mTOR inhibitors involves modulation of NFκB and PKC-α signaling

Glioblastoma (GBM) is the most aggressive type of brain tumors in adults with survival period <1.5 years of patients. The role of mTOR pathway is documented in invasion and migration, the features associated with aggressive phenotype in human GBM. However, most of the preclinical and clinical studies with mTOR inhibitors are focused on antiproliferative and cytotoxic activity in GBM. In this study, we demonstrate that mTOR inhibitors-rapamycin (RAP), temisirolimus (TEM), torin-1 (TOR) and PP242 suppress invasion and migration induced by Tumor Necrosis Factor-α (TNFα) and tumor promoter, Phorbol 12-myristate 13-acetate (PMA) and also reduce the expression of the TNFα and IL1β suggesting their potential to regulate factors in microenvironment that support tumor progression. The mTOR inhibitors significantly decreased MMP-2 and MMP-9 mRNA, protein and activity that was enhanced by TNFα and PMA. The effect was mediated through reduction of Protein kinase C alpha (PKC-α) activity and downregulation of NFκB. TNFα- induced transcripts of NFκB targets -VEGF, pentraxin-3, cathepsin-B and paxillin, crucial in invasion were restored to basal level by these inhibitors. With limited therapeutic interventions currently available for GBM, our findings are significant and suggest that mTOR inhibitors may be explored as anti-invasive drugs for GBM treatment.