The role of extracellular-5'-nucleotidase/CD73 in glioma peritumoural brain edema

CD73 in glioblastoma: Where are we now and what are the future directions?

Glioblastoma (GB) is the most aggressive type of brain tumor with heterogeneity, strong invasive ability, and high resistance to therapy due to immunosuppressive mechanisms. CD73 is an overexpressed enzyme in GB acts via two main mechanisms:(1) CD73 acts as an adhesion protein independent of the enzymatic activity or (2) via the catalyses of AMP to adenosine (ADO) generating a strong modulatory molecule that induces alterations in the tumor cells and in the tumor microenvironment cells (TME). Taken together, CD73 is receiving attention during the last years and studies demonstrated its dual potential benefit as a target to GB therapy. Here, we review the roles of CD73 and P1 receptors (ADO receptors) in GB, the impact of CD73 in the immune interactions between tumor and other immune cells, the proposed therapeutic strategies based on CD73 regulation, and discuss the gap in knowledge and further directions to bring this approach from preclinical to clinical use.

Anthraquinone: a promising scaffold for the discovery and development of therapeutic agents in cancer therapy

Cancer, characterized by uncontrolled malignant neoplasm, is a leading cause of death in both advanced and emerging countries. Although, ample drugs are accessible in the market to intervene with tumor progression, none are totally effective and safe. Natural anthraquinone (AQ) equivalents such as emodin, aloe-emodin, alchemix and many synthetic analogs extend their antitumor activity on different targets including telomerase, topoisomerases, kinases, matrix metalloproteinases, DNA and different phases of cell lines. Nano drug delivery strategies are advanced tools which deliver drugs into tumor cells with minimum drug leakage to normal cells. This review delineates the way AQ derivatives are binding on these targets by abolishing tumor cells to produce anticancer activity and purview of nanoformulations related to AQ analogs.

Improved efficacy against malignant brain tumors with EGFRwt/EGFRvIII targeting immunotoxin and checkpoint inhibitor combinations

BACKGROUND

D2C7-IT is a novel immunotoxin (IT) targeting wild-type epidermal growth factor receptor (EGFRwt) and mutant EGFR variant III (EGFRvIII) proteins in glioblastoma. In addition to inherent tumoricidal activity, immunotoxins induce secondary immune responses through the activation of T cells. However, glioblastoma-induced immune suppression is a major obstacle to an effective and durable immunotoxin-mediated antitumor response. We hypothesized that D2C7-IT-induced immune response could be effectively augmented in combination with αCTLA-4/αPD-1/αPD-L1 therapies in murine models of glioma.

METHODS

To study this, we overexpressed the D2C7-IT antigen, murine EGFRvIII (dmEGFRvIII), in established glioma lines, CT-2A and SMA560. The reactivity and therapeutic efficacy of D2C7-IT against CT-2A-dmEGFRvIII and SMA560-dmEGFRvIII cells was determined by flow cytometry and in vitro cytotoxicity assays, respectively. Antitumor efficacy of D2C7-IT was examined in immunocompetent, intracranial murine glioma models and the role of T cells was assessed by CD4+ and CD8+ T cell depletion. In vivo efficacy of D2C7-IT/αCTLA-4/αPD-1 monotherapy or D2C7-IT+αCTLA-4/αPD-1 combination therapy was evaluated in subcutaneous unilateral and bilateral CT-2A-dmEGFRvIII glioma-bearing immunocompetent mice. Further, antitumor efficacy of D2C7-IT+αCTLA-4/αPD-1/αPD-L1/αTim-3/αLag-3/αCD73 combination therapy was evaluated in intracranial CT-2A-dmEGFRvIII and SMA560-dmEGFRvIII glioma-bearing mice. Pairwise differences in survival curves were assessed using the generalized Wilcoxon test.

RESULTS

D2C7-IT effectively killed CT-2A-dmEGFRvIII (IC₅₀ = 0.47 ng/mL) and SMA560-dmEGFRvIII (IC₅₀ = 1.05 ng/mL) cells in vitro. Treatment of intracranial CT-2A-dmEGFRvIII and SMA560-dmEGFRvIII tumors with D2C7-IT prolonged survival (P = 0.0188 and P = 0.0057, respectively), which was significantly reduced by the depletion of CD4+ and CD8+ T cells. To augment antitumor immune responses, we combined D2C7-IT with αCTLA-4/αPD-1 in an in vivo subcutaneous CT-2A-dmEGFRvIII model. Tumor-bearing mice exhibited complete tumor regressions (4/10 in D2C7-IT+αCTLA-4 and 5/10 in D2C7-IT+αPD-1 treatment groups), and combination therapy-induced systemic antitumor response was effective against both dmEGFRvIII-positive and dmEGFRvIII-negative CT-2A tumors. In a subcutaneous bilateral CT-2A-dmEGFRvIII model, D2C7-IT+αCTLA-4/αPD-1 combination therapies showed dramatic regression of the treated tumors and measurable regression of untreated tumors. Notably, in CT-2A-dmEGFRvIII and SMA560-dmEGFRvIII intracranial glioma models, D2C7-IT+αPD-1/αPD-L1 combinations improved survival, and in selected cases generated cures and protection against tumor re-challenge.

CONCLUSIONS

These data support the development of D2C7-IT and immune checkpoint blockade combinations for patients with malignant glioma.

Exploration of Involved Key Genes and Signaling Diversity in Brain Tumors

Brain tumors are becoming a major cause of death. The classification of brain tumors has gone through restructuring with regard to some criteria such as the presence or absence of a specific genetic alteration in the 2016 central nervous system World Health Organization update. Two categories of genes with a leading role in tumorigenesis and cancer induction include tumor suppressor genes and oncogenes; tumor suppressor genes are inactivated through a variety of mechanisms that result in their loss of function. As for the oncogenes, overexpression and amplification are the most common mechanisms of alteration. Important cell cycle genes such as p53, ATM, cyclin D2, and Rb have shown altered expression patterns in different brain tumors such as meningioma and astrocytoma. Some genes in signaling pathways have a role in brain tumorigenesis. These pathways include hedgehog, EGFR, Notch, hippo, MAPK, PI3K/Akt, and WNT signaling. It has been shown that telomere length in some brain tumor samples is shortened compared to that in normal cells. As the shortening of telomere length triggers chromosome instability early in brain tumors, it could lead to initiation of cancer. On the other hand, telomerase activity was positive in some brain tumors. It is suggestive that telomere length and telomerase activity are important diagnostic markers in brain tumors. This review focuses on brain tumors with regard to the status of oncogenes, tumor suppressors, cell cycle genes, and genes in signaling pathways as well as the role of telomere length and telomerase in brain tumors.