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Bioinformatics of the Brain

by promoting T cell extravasation and GBM cell apoptosis, especially in mes-

enchymal GBM [199]. Another substantial evidence is provided by Heinrich et

al. in paracrine model of GBM where GL261 glioblastoma cells and RAW264.7

macrophages have provided the opportunity to implement detailed expression

analysis of GBM markers, and genes related epithelial-to-mesenchymal tran-

sition of tumor cells, ECM remodeling enzymes, and many other genes that

were considerably upregulated in contrast to 2D surfaces. The results were

comparable with GBM patient samples lessening the contradictions between

in vitro models and clinical trials [200]. Further, CSCs are identified as major

connection to poor prognosis [201]. Thus, they are promising to be additional

novel targets to eradicate tumor population as such function of the epige-

netic suppressor called polycomb repressive complex 2 was diminished with

S-adenosyl methionine competitive inhibitor (GSK343) to invoke potent tu-

mor killing effects [202] and by also considering communication with stromal

cells [203]. The physical barrier of ECM is also critical for substantial im-

provement of clinical success, as it hinders diffusion of drugs reaching tumor

cells, as well as provides cues that alter tumor cell behavior against the drug.

In one of example studies, Hermida et al. demonstrated that significant re-

sistance to cisplatin was observed in RGDS-alginate gels in contrast to 2D

culture confirming clinical trial failure of this drug [203].

In analysis of drug response, BBB is a key issue for both drug penetration

and distribution towards tumor cells. As such, patient-derived GBM cells co-

encapsulated with stromal cells in gelatin gels were discovered to be affected

differentially, as temozolomide treatment increased cPARP+ apoptotic tumor

cell number, but within 10 µm distance of microvascular network, number of

cPARP- tumor cells were higher when all vascular cell types were encapsu-

lated with GBM cells [159]. Likewise, status of integrity and density of blood

vessels in GBM are subject to modifications depending on the stage of tumor,

invasion and location. In an attempt to study this effect, a biomimetic mi-

crofluidic system of GBM-22 and pericyte heterospheroids surrounded with

endothelial cells, pericytes, and astrocytes in fibrin addresses to the challenge

of intact BBB with functional cell-cell junctions. Instead of naked drugs, a

carrier system is also current interest for cancer treatment and even if a drug

delivery vehicle is chosen as a core strategy, still targeting GBM will be limited

by penetration through BBB. For targeted drug delivery to overcome adverse

effects of toxicity and poor BBB penetration, chemotherapy drug carriers can

be functionalized with ligands of cell surface receptors [204].

Moreover, these scaffold systems are utilized to fabricate microwell-based

chip systems to benefit from the continual drug capture and release, and gra-

dient establishment even if single injection was performed [205]. Similarly,

tumor tissue architecture serves as solid ground to imitate the necrotic region

of GBM and can be targeted for drug delivery. In an effort to show corre-

sponding role of this microenvironment, GBM cells in collagen gel constituted

mid-section of the central chamber to create a region with high number of dead

cells (necrotic core) was successfully formed. In a trial of hypoxia-activated