**4. Natural products mediated targeting of proliferative protein network in glioblastoma**

Crude hydromethanolic extracts produced by maceration of *Spartium junceum* flowers and *Onopordum acanthium* leaves were tested for anticancer activity against glioblastoma U-373 cancer cells. *O. acanthium* was effective against glioblastoma cells and induced apoptosis [31] . Aqueous extract of *Ruta graveolens* L. notably enhanced phosphorylated ERK1/2 and Akt levels in glioma cells. The results indicated that *Ruta graveolens* exerted inhibitory effects via activation of ERK1/2 and Akt-induced signaling pathways [32].

ing MSCs. CBX considerably upregulated cell-surface expression of DR5 in CBX-treated ΔGli36 and U87MG cells. CBX also inhibited gap junction (GJ) communication via modula‐ tion of connexin (Cx43). CBX remarkably reduced expression levels of Cx43 in U87MG and ΔGli36 cells after 72 hours. Results revealed that TRAIL-induced apoptosis was markedly

Antibody-based anticancer therapies have attracted considerable attention and different structural variations are being tested for efficacies which involve smaller antibody frag‐ ments such as ScFvs, Fabs, and nanobodies. Single-chain Fv fragment (scFv) consists of a variable light-chain (VL) and variable heavy-chain (VH) domains, which contains whole

Multidrug resistance protein 3 (MRP3) is frequently overexpressed in glioblastoma multi‐ forme cells. scFvM58-sTRAIL is an engineered protein formed by fusion of MRP3-specific scFv antibody M58 with N-terminus of soluble TRAIL. scFvM58-sTRAIL was effective against MRP3-positive GBM cells. Expectedly, scFvM58-sTRAIL did not show significant activity against MRP3-negative Jurkat cells. These results indicated that scFvM58-sTRAIL was

Various bivalent EGFR-targeting nanobodies (ENbs) have been designed and noted to be effective. Neural stem cells (NSC) are potent agents to deliver ENbs. Preclinical study revealed that tumor regression was significantly higher in xenografted mice treated with NSC-ENb2- TRAIL. Xenografted mice survived for 51 days upon treatment with control NSC-ENb2 and 80% of mice survived for 80 days after treatment with NSC-ENb2-TRAIL. These findings indicated that tumoritropic NSC-releasing ENb2 inhibited growth of glioblastoma and effectiveness of ENb2-based therapy was markedly improved by NSC-releasing ENb2-

Diethylamino-curcumin mimics with substituted triazolyl groups have previously been synthesized and reported to effectively sensitize resistant CRT-MG astroglioma cells to

Gingerol, a major bioactive component of ginger, has been shown to trigger expression of DR5 in a p53-dependent manner in U87 glioblastoma cells. Digitoxin (DT), a clinically approved cardiac glycoside, has been observedto overcome resistance againstTRAILin resistantU87MG glioblastoma cells. Digitoxin effectively enhanced DR5 expression on cell surface of resistant

**4. Natural products mediated targeting of proliferative protein network**

Crude hydromethanolic extracts produced by maceration of *Spartium junceum* flowers and *Onopordum acanthium* leaves were tested for anticancer activity against glioblastoma U-373 cancer cells. *O. acanthium* was effective against glioblastoma cells and induced apoptosis [31] .

higher in cells transfected with Cx43-siRNA [26] .

effective against MRP3-positive cancer cells [27].

antigen-binding site.

150 Neurooncology - Newer Developments

TRAIL [28].

TRAIL [29].

cancer cells [30].

**in glioblastoma**

Triterpenoid saponins from *Albizia lebbeck* (L.) showed activity against TG1 and U-87 MG cancer cells with IC50 values of 2.10 and 2.24 μM for compound 2 and 3.46 and 1.36 μM for compound 1 [33].

Isocitrate Dehydrogenase 1 and 2 (IDH1/2) are two important enzymes involved in the Krebs cycle and oxidatively decarboxylate isocitrate to produce a-ketoglutarate and CO2. IDH1 is a cytosolically located protein. IDH2 encodes a mitochondrial protein. Parsons et al. reported that IDH1/*2* was mutated in approximately 60–80% of secondary gliomas and 5% of primary gliomas [34]. There are two common IDH mutation (IDH1R132H and IDH2172 mutations) types. It has been reported that these mutations are seen in GBM (>90% samples with IDH1/2 mutation). These mutations lead to increased production of the oncometabolite D-2-hydrox‐ yglutarate. This metabolite has previously been noted to modify DNA methylation patterns in GBM and transcriptional activity of different target genes [35]. *IDH1* mutation may be correlated with several clinical factors such as younger patient age and frontal location. It has also been reported that additional survival benefit (median survival 9.75 years) was ach‐ ieved from greater tumor resection (<5 cm3 residual) in *IDH1* mutants, except for wild-type *IDH1*. It has also been suggested that the presence of *IDH1*/*2* mutation supports increased therapeutic efficacy with chemoradiotherapy and greater resection [1]. When IDH mutations occur, enzymatic activities of some important molecules can be altered. While alpha-ketoglu‐ tarate (α-KG) is decreased, produced 2-hydroxyglutarate (2-HG) can inhibit the activity of some enzymes. These enzymes play a significant role in regulating DNA and histone meth‐ ylation (α-KG-dependent dioxygenase), including histone demethylases and the TET family of 5mC hydroxylases [36–38].

TET proteins are described as a new class of enzymes which can alter the methylation status of the DNA by converting 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC). The biological function of 5hmC is not clear. It has been suggested that it is an intermediate in DNA demethylation process. 5hmC offers remarkable reduction in human gliomas as compared to normal brain. An inverse relationship has been reported between 5hmC levels and cell proliferation [39,40].

p53 is a very important protein involved in many physiological and pathological process in the regulation of cell viability in terms of cell cycle, apoptosis, cell differentiation, and other mechanisms of cell regulation during exposure to DNA-damaging agents (e.g., ultraviolet radiation, toxins, chemotherapeutic agents) [1]. It has been reported that P53 gene is mutat‐ ed in 28% of primary GBMs [41]. There are three patterns regarding p53 dysfunction. One is called loss of function. This pattern may describe a lot of endogenous growth inhibitor effects of wild-type p53. The other is gain of function. This means that mutant p53 upregulates a distinct subset of genes from wild-type p53. The last one is dominant-negative effects of p53. It is associated with a tetramer pattern of mutant p53/wild-type p53 and leads to downregu‐ late activity [42]. It is known that some other mechanisms of p53 inactivation include muta‐ tions ofits modulators including MDM2 inhibitor or deletion of p14ARF [43,44]. Whetherthere

is a correlation between p53 and GBM prognosis is still unclear due to the complexity of the p53 signaling pathway. P53 pathway includes many important regulators and the heteroge‐ neity of p53 mutation types can also affect the p53 molecule. Because of those mentioned, therapies targeting P53 have been limited in this field [42].

The deletion of 1p and 19q, occurring early in tumorigenesis, is known as an important genetic signature. The deletion is seen in 50–70% of patients with low-grade oligodendrogliomas. This can be predictive for the tumor's chemosensitivity to some agents [46,47]. It has been report‐ ed that *P190RhoGAP*, localized on 19q13.3, can be one of the candidate genes as a tumor suppressor [48]. A large-scale genomic analysis by array CGH has reported two different patterns about 1p deletion for prognostic factors. One of them is the whole 1p (associated with the deletion of the whole 19q). This may be associated with a good prognosis for oligoden‐ drogliomas. Another is 1p deletion (not associated with 19q loss). This deletion has a nega‐ tive prognostic value and improves progression-free survival (PFS) and overall survival (OS). It is mostly associated with astrocytomas [49]. It is also related to the response to chemother‐ apy and radiation in oligodendroglioma. Data obtained from EORTC 26951 and RTOG 9402 trials showed an improvement in OS with the addition of radiation to procarbazine/lomus‐ tine/vincristine chemotherapy in anaplastic oligodendroglioma with 1p/19q mutation [50]. There are some studies correlated with these similar findings, In GBM, similar findings have been demonstrated in some studies [51,52], but not in others [53,54]. It has also been report‐ ed that codeletion of 1p and 19q is related with *IDH1* mutation and *MGMT* hypermethyla‐ tion [47,55].

O-6-Methylguanine-DNA-methyltransferase (MGMT) is involved in removal of alkylation at the O6 position of guanine. Hypermethylation of *MGMT* transcriptionally down-regulated its expression. This situation results in impaired repair capability response to chemotherapeutic agents and radiation. Some clinical trials have confirmed the prognostic and predictive roles of *MGMTm* [56]. It has been suggested that patients with *MGMTm* are responsive to chemo‐ therapy. However, *MGMT* status was not distinguished between patients with glioblastoma (GBM) and those with anaplastic astrocytoma (AA) and this restricts interpretation of the study. The European Organisation for Research and Treatment of Cancer (EORTC) 26981/22981 and National Cancer Institute of Canada (NCIC) trials also indicates increased responsiveness to temozolomide for patients with MGMTm [57]. It has been suggested that a standard marker both following prognosis and identifying patients for clinical trials, in which alkylation therapies and/or radiation therapy are applied, may be used for MGMTm [1].
