Radiotherapy-drug combinations in the treatment of glioblastoma: a brief review

Glioblastoma (GBM) accounts for over 50% of gliomas and carries the worst prognosis of all solid tumors. Owing to the limited local control afforded by surgery alone, efficacious adjuvant treatments such as radiotherapy (RT) and chemotherapy are fundamental in achieving durable disease control. The best clinical outcomes are achieved with tri-modality treatment consisting of surgery, RT and systemic therapy. While RT-chemotherapy combination regimens are well established in oncology, this approach was largely unsuccessful in GBM until the introduction of temozolomide. The success of this combination has stimulated the search for other candidate drugs for concomitant use with RT in GBM. This review seeks to collate the current evidence for these agents and synthesize possible future directions for the field.

Therapeutic Options in Neuro-Oncology

One of the biggest challenges in neuro-oncology is understanding the complexity of central nervous system tumors, such as gliomas, in order to develop suitable therapeutics. Conventional therapies in malignant gliomas reconcile surgery and radiotherapy with the use of chemotherapeutic options such as temozolomide, chloroethyl nitrosoureas and the combination therapy of procarbazine, lomustine and vincristine. With the unraveling of deregulated cancer cell signaling pathways, targeted therapies have been developed. The most affected signaling pathways in glioma cells involve tyrosine kinase receptors and their downstream pathways, such as the phosphatidylinositol 3-kinases (PI3K/AKT/mTOR) and mitogen-activated protein kinase pathways (MAPK). MAPK pathway inhibitors include farnesyl transferase inhibitors, Ras kinase inhibitors and mitogen-activated protein extracellular regulated kinase (MEK) inhibitors, while PI3K/AKT/mTOR pathway inhibitors are divided into pan-inhibitors, PI3K/mTOR dual inhibitors and AKT inhibitors. The relevance of the immune system in carcinogenesis has led to the development of immunotherapy, through vaccination, blocking of immune checkpoints, oncolytic viruses, and adoptive immunotherapy using chimeric antigen receptor T cells. In this article we provide a comprehensive review of the signaling pathways underlying malignant transformation, the therapies currently used in the treatment of malignant gliomas and further explore therapies under development, including several ongoing clinical trials.

Uncovering the Potential of Lipid Drugs: A Focus on Transient Membrane Microdomain-Targeted Lipid Therapeutics

Membrane lipids are generally viewed as inert physical barriers, but many vital cellular processes greatly rely on the interaction with these structures, as expressed by the membrane hypothesis that explain the genesis of schizophrenia, Alzheimer's and autoimmune diseases, chronic fatigue or cancer, among others. The concept that the cell membrane displays transient membrane microdomains with distinct lipid composition provide the basis for the development of selective lipid-targeted therapies, the membrane-lipid therapies (MLTs). In this concern, medicinal chemists may design therapeutically valuable compounds 1) with a higher affinity for the lipids in these microdomains to restore the normal physiological conditions, 2) that can directly or 3) indirectly (via enzyme inhibition/activation) replace damaged lipids or restore the regular lipid levels in the whole membrane or microdomain, 4) that alter the expression of genes related to lipid genesis/metabolism or 5) that modulate the pathways related to the membrane binding affinity of lipid-anchored proteins. In this context, this mini-review aims to explore the structural diversity and clinical applications of some of the main membrane and microdomain-targeted lipid drugs.

SMS2 deficiency impairs PKCδ-regulated B cell tolerance in the germinal center

B cell tolerance prevents autoimmunity by deleting or deactivating autoreactive B cells that otherwise may cause autoantibody-driven disorders, including systemic lupus erythematosus (lupus). Lupus is characterized by immunoglobulin Gs carrying a double-stranded (ds)-DNA autospecificity derived mainly from somatic hypermutation in the germinal center (GC), pointing to a checkpoint breach of GC B cell tolerance that leads to lupus. However, tolerance mechanisms in the GC remain poorly understood. Here, we show that upregulated sphingomyelin synthase 2 (SMS2) in anti-dsDNA GC B cells induces apoptosis by directly activating protein kinase C δ (PKCδ)'s pro-apoptotic activity. This tolerance mechanism prevents lupus autoimmunity in C57/BL6 mice and can be stimulated pharmacologically to inhibit lupus pathogenesis in lupus-prone NZBWF1 mice. Patients with lupus consistently have substantially reduced SMS2 expression in B cells and to an even greater extent in autoimmune-prone, age-associated B cells, suggesting that patients with lupus have insufficient SMS2-regulated B cell tolerance.

The Novel Antitumor Compound HCA Promotes Glioma Cell Death by Inducing Endoplasmic Reticulum Stress and Autophagy

Glioblastoma (GBM) is the most common and aggressive type of primary brain tumor in adults, and the median survival of patients with GBM is 14.5 months. Melitherapy is an innovative therapeutic approach to treat different diseases, including cancer, and it is based on the regulation of cell membrane composition and structure, which modulates relevant signal pathways. Here, we have tested the effects of 2-hydroxycervonic acid (HCA) on GBM cells and xenograft tumors. HCA was taken up by cells and it compromised the survival of several human GBM cell lines in vitro, as well as the in vivo growth of xenograft tumors (mice) derived from these cells. HCA appeared to enhance ER stress/UPR signaling, which consequently induced autophagic cell death of the GBM tumor cells. This negative effect of HCA on GBM cells may be mediated by the JNK/c-Jun/CHOP/BiP axis, and it also seems to be provoked by the cellular metabolite of HCA, C21:5n-3 (heneicosapentaenoic acid). These results demonstrate the efficacy of the melitherapeutic treatment used and the potential of using C21:5n-3 as an efficacy biomarker for this treatment. Given the safety profile in animal models, the data presented here provide evidence that HCA warrants further clinical study as a potential therapy for GBM, currently an important unmet medical need.

Can we rely on synthetic pharmacotherapy for the treatment of glioblastoma?

Introduction: Despite decades of clinical trials utilizing conventional and novel therapeutics, the effective treatment of glioblastoma remains one of the most formidable challenges in oncology. Current standard of care includes surgery and chemoradiation. Synthetic pharmacotherapies continue to be explored as potential therapeutic options for glioblastoma patients.Areas covered: This study reviews synthetic pharmacotherapies that are currently under investigation in phase I-III clinical trials. The authors of this study highlight the mechanisms of action of the synthetic pharmacotherapy agents under investigation, outline the available evidence for their utility based on the literature, and summarize the current landscape.Expert opinion: Although warranting further investigation, the studies generally highlighted here have not shown remarkable changes in clinical benefits beyond what has already been established with radiochemotherapy. As we develop more synthetics, we will likely need to combine them with other synthetics to target multiple separate molecular pathways. There is considerable potential when this treatment strategy is guided by molecular profiling approaches which seek to stratify patients based on treatments that would be most efficacious for them.

A Systematic Review of Glioblastoma-Targeted Therapies in Phases II, III, IV Clinical Trials

Glioblastoma (GBM), the most frequent and aggressive glial tumor, is currently treated as first line by the Stupp protocol, which combines, after surgery, radiotherapy and chemotherapy. For recurrent GBM, in absence of standard treatment or available clinical trials, various protocols including cytotoxic drugs and/or bevacizumab are currently applied. Despite these heavy treatments, the mean overall survival of patients is under 18 months. Many clinical studies are underway. Based on clinicaltrials.org and conducted up to 1 April 2020, this review lists, not only main, but all targeted therapies in phases II-IV of 257 clinical trials on adults with newly diagnosed or recurrent GBMs for the last twenty years. It does not involve targeted immunotherapies and therapies targeting tumor cell metabolism, that are well documented in other reviews. Without surprise, the most frequently reported drugs are those targeting (i) EGFR (40 clinical trials), and more generally tyrosine kinase receptors (85 clinical trials) and (ii) VEGF/VEGFR (75 clinical trials of which 53 involving bevacizumab). But many other targets and drugs are of interest. They are all listed and thoroughly described, on an one-on-one basis, in four sections related to targeting (i) GBM stem cells and stem cell pathways, (ii) the growth autonomy and migration, (iii) the cell cycle and the escape to cell death, (iv) and angiogenesis.